Tag Archives: cancer

Does talcum powder cause ovarian cancer? Weighing up the human and animal studies

In this article, Justin Varholick, investigates the evidence on whether talcum powder can cause ovarian cancer. Over the years, several courts have ruled that talcum powder can cause ovarian cancer, while the scientific evidence suggests otherwise. In light of Ovarian Cancer Month, it is important to highlight how animal and human studies can improve our understanding of the disease, and prevent misinformation spread from the media. This article outlines that both animal and human studies are not perfect. Animal studies sometimes do not have proper controls and human studies suffer from bias. The current research suggests no direct link between talc and cancer, but more research is certainly necessary.

Ovarian cancer is a serious disease affecting around 22,000 women in the United States and contributing to around 14,000 deaths each year. Since the 1960s the American public has questioned whether the use of talcum powder – for soothing dry skin, absorbing sweat, and preventing chafing of the thighs — increases women’s’ risk for ovarian cancer. This speculation began after acknowledging the risks of asbestos and public theories that asbestos was in talc products; however, cosmetic grade talc undergoes strict quality control and does not contain asbestos.

Image by Austin Kirk

Multiple studies on rodents, non-human primates, and humans have investigated the link between talc and cancer since the 1960s. Overall the results are inconsistent; some studies suggest talc is associated with ovarian cancer while others suggest talc is not carcinogenic. Recently, despite these inconsistencies, a Los Angeles jury ordered Johnson & Johnson to pay $417 million to a woman who blamed her terminal ovarian cancer on the use of baby powder — this is just one of many lawsuits against Johnson & Johnson over their talc powder. In light of this recent event I would like to delve into the animal and human studies investigating the link between talcum powder and ovarian cancer.

Is talcum powder a carcinogen?

Empirical studies first began on rodents such as hamsters, rats, and mice; however, these studies only focused on whether talc was a carcinogen in general. Researchers chose rodents because it is relatively easy to systematically administer talc to rodents via inhalation. Furthermore, rodents — especially the laboratory rat — are particularly sensitive to forming malignant tumors in the lungs when exposed to chemicals via inhalation regardless of the chemical itself. Therefore, by using rodents there is an increased chance of detecting an effect of cancer following exposure to talc via inhalation — if one is present. It is important to note here that although humans are exposed to talc by inhalation or via topical application, the specific method of applying talc is not important when determining general carcinogenicity.

For one of the first studies investigating talc exposure and cancer in rodents, researchers first gathered information on how much baby powder human infants were regularly exposed to – although infants are usually exposed via topical application and rodents are exposed via inhalation. Using this information they designed an experiment using hamsters and exceeded the amount of talc human infants are normally exposed to by 30 to 1700 times — depending on the experimental treatment group. The scientists also formed a control group that was exposed to a negative dust control; titanium dioxide. This control is important because increased levels of dust in the air can lead to chronic inflammation of the lungs, which increases the risk of malignant tumors — independent of particle type (e.g. talc powder, titanium dioxide, toner, carbon black, etc.). Controlling for dust and exceeding levels of normal exposure, the study reported no difference between the groups in body weight, survival, or signs of cancer in the larynx, trachea, lungs, liver, kidney, stomach, uterus, ovaries, or testes of these hamsters.

Further studies were conducted on rodents — specifically mice and rats — that did find an effect linking cancer to talc; however, these studies were confounded. One study in particular found that female rats and mice exposed to high levels of talc via inhalation for 4 months had a higher risk of lung cancer. Unfortunately, this study did not use a titanium dioxide control group, thus the finding could be an artefact of chronic inflammation from air particles — as discussed above. Furthermore, this study was unable to identify another biological mechanism beyond chronic inflammation responsible for the onset of cancer.

In summary, these rodent studies allowed scientists to exceed normal exposure levels and use an animal with increased sensitivity to the treatment in question. However, proper control groups must be used to help elucidate whether the effect is an artefact. Importantly, these studies were only interested in whether talc is a possible carcinogen, not whether ovaries exposed to talc have increased risk of cancer specifically. Overall, these studies were unable to find a link between talc and risk of cancer, beyond chronic inflammation from increased levels of air particulates.

Can talcum powder be found in the ovaries?

Some studies in animals and humans have been particularly focused on finding a link between talc use and ovarian cancer — not just whether talc is a carcinogen. To understand the plausibility of this link, these studies first needed to establish whether it is possible for particles of talc to migrate into the genital tract after being applied topically to the perineal region (area between vagina/scrotum and anus). A simple understanding of biophysics led many to conclude that it was impossible for the particles to travel up the vagina, cross the cervix, travel through the uterus, and then “swim” upstream through the oviducts; without being assisted by some form of locomotion. Nonetheless, some studies using animals investigated whether it was a possibility. Specifically, one study using female cynomolgus monkeys (Macaca fascicularis) — an animal model anatomically and physiologically comparable to human female — investigated whether carbon black particles could reach the oviducts or ovaries. This study was unable to conclude that carbon black particles could indeed travel up to the oviducts or ovaries.

Image by Noveprim

Further studies were done with human females that applied talcum powder to their underwear or perineal region daily that also had ovarian or pelvic cancer; which required surgical removal of the ovaries.  After removing the ovaries, scientists used microscopy techniques to scan the ovaries and identified low numbers of particles that were relatively small in size in about 50–75% of cases (multiple studies). Thus, although talc can be found in or around ovarian tissue the amount found was considered too small to cause ovarian cancer. It has also been noted that findings from these studies were widely inconsistent and were confounded by women lying in a supine or Trendelenburg position — which may aid in the surgery of the pelvic region but is also used to aid in vitro fertilization.

Thus, studies in both animals and humans cannot definitively suggest talc can translocate from the perineal region to the ovaries, which may be necessary for the talc to affect the ovaries. Nonetheless, both animal and human studies have been limiting; studies with monkeys only used a particle similar to talc and human studies involved a lying position that aided in the migration of talc up the genital tract.

How many women using talcum powder get ovarian cancer?

Two types of human studies have investigated, and continue to investigate, the link between talc and ovarian cancer; case-control and cohort studies. The case-control studies gather a group of women diagnosed with ovarian cancer and a group of women with no ovarian cancer. They then ask all women to retrospectively discuss their use of talc on the genital area throughout their life — noting frequency and average amount. The obvious downside to this type of study is that it is open to reporting bias. Some women may forget when or how often they used talc, while others may overestimate their use and further bias may occur if there is an expectancy that talc may have contributed to the onset of ovarian cancer. In contrast, the cohort studies gather a group of women early in life and then have them report in real-time throughout their life how often they use multiple products — including products with talc. After several decades they then compare how many women are diagnosed with ovarian cancer and used talc products, diagnosed with ovarian cancer and did not use talc products, etc. Cohort studies, however, are often limiting because few women are actually diagnosed with ovarian cancer compared to those that are not.

A recent meta-analysis, published this year, gathered 24 case-control and 3 cohort studies investigating the use of talc on the perineal region and its relation to ovarian cancer. Gathering all of these studies into a single analysis, they found that talc powder use on the perineal region is associated with a small increased risk of developing ovarian cancer; however, case-control studies largely contributed to this association — which have obvious disadvantages as outlined above. This positive association was also limited to a single type of ovarian cancer; identified as serous carcinoma — the most common type of ovarian cancer (types of ovarian cancer). Importantly, if reporting bias is affecting the case-control studies, then the association between talc use and ovarian cancer should not be limited to a single type of ovarian cancer. The authors also note that publication bias may also be affecting the case-control studies, meaning that some hospitals may gather information about talc use and ovarian cancer but do not publish their findings because they do not find a link between the two.

In summary, studies with humans do suggest that there is a small positive association between talc use and ovarian cancer; however, these studies are largely limited to case-control studies which have disadvantages of reporting and publication biases. Furthermore, these studies can only tell us about the relative risk of ovarian cancer when using talc. They cannot tell us about the biological basis linking talcum powder use to cancer.

Talcum powder does not cause ovarian cancer

The current evidence from both animal and human studies does not suggest that talc can be directly linked to ovarian cancer. However, both animal and human studies are not perfect. Studies using animals sometimes lack important controls and are not able to properly investigate the specific question at hand without proper animal models (i.e. cynomolgus monkeys). However, animals can be utilized in investigating whether talc is a carcinogen in general because some are especially sensitive to different types of treatments. Studies with humans also have disadvantages due to limitations of subject pools and biases. Despite this, studies with humans somewhat consistently find a link between talc and ovarian cancer, thus humans may be particularly sensitive to talc beyond other animals — although this is highly unlikely given that studies on other mammals suggest no direct relationship.

Importantly, there are many more studies on animals and humans that investigate the link between talc and cancer that I did not include in this brief discussion. Therefore, it is important to note that in a recent review in 2015, the Cosmetic Ingredient Review Expert Panel reported that talc is safe to use in standard practices with normal concentrations. They also note that there is:

  • Absence of persuasive evidence that talc can migrate from the perineum to the ovaries
  • Lack of consistent statistically significant positive associations across studies
  • Failure to rule out plausible alternative explanations of statistically significant results, including biases, risk factors, and exposure to misclassifications
  • Absence of a plausible biological mechanism
  • Lack of credible, defensible evidence of carcinogenicity from results of epidemiological studies of occupational exposures and animal bioassays

Thus, more research is necessary to determine whether talc is linked to ovarian cancer, despite what the Los Angeles courts might say.

Justin Varholick

 

References

Berge, W., Mundt, K., Luu, H. and Boffetta, P. 2017. Genital use of talc and risk of ovarian cancer: a meta-analysis. European Journal of Cancer Prevention.

Fiume, M.M., Boyer, I., Bergfeld, W.F., Belsito, D.V., Hill, R.A., Klaassen, C.D., Liebler, D.C., Marks, J.G., Shank, R.C., Slaga, T.J., Snyder, P.W. and Andersen, F.A. 2015. Safety assessment of talc as used in cosmetics. International journal of toxicology 34(1 Suppl), p. 66S–129S.

Reid, B.M., Permuth, J.B. and Sellers, T.A. 2017. Epidemiology of ovarian cancer: a review. Cancer biology & medicine 14(1), pp. 9–32.

Wehner, A.P. 2002. Cosmetic talc should not be listed as a carcinogen: comments on NTP’s deliberations to list talc as a carcinogen. Regulatory Toxicology and Pharmacology 36(1), pp. 40–50.

Research Roundup: Biosensors, breast cancer and the benefits of antiretrovirals

Welcome to this week’s (slightly late!) Research Roundup. These posts aim to inform our readers about the many stories that relate to animal research each week. Do you have an animal research story we should include in next week’s Research Roundup? You can send it to us via our Facebook page or through the contact form on the website.

  • A new experimental technology can monitor and maintain drug levels in body. The device has a biosensor to monitor drug levels in the body; this can relay information every few seconds to a control unit and pump, which releases additional drugs as necessary. Using rabbits, the researchers were able to keep a constant dosage among all animals in their study – despite physiological and metabolic differences between individual animals. Taking it a step further, the research team introduced secondary drugs that, due to acute drug-drug interactions, would disrupt the levels of the initial drug. However they found levels of the initial drug were stabilised by the sensor.  This paper was published in Nature Biomedical Engineering.

Image courtesy of the Soh Lab, Stanford.

  • A gene associated with the growth of cancer cells is also implicated with the growth of stem cells. Previous research by this group has implicated the high-mobility group (HMG) gene in the formation of polyps, abnormal growths projecting from the intestinal lining that can be precursors of cancer, in mice. Examining the intestinal cells of these mice localized the HMG active gene and its protein to stem cells buried within the deep grooves in the intestinal lining. These stem cells carrying the HMG gene multiplied far more rapidly and also increased the number of Paneth cells, a type of niche cell known to support intestinal stem cells. This research provides an exciting avenue for future research into processes that could disrupt cancer growth and prevent tumour progression. This study was published in Nature Communications.

  • Young people who contract HIV in the UK can now expect to live to a near-normal age thanks to anti-retrovirals. A study in the Lancet of almost 90,000 people showed, “Patients who started Anti-Retroviral Therapy (ART) during 2008–10 whose CD4 counts exceeded 350 cells per μL 1 year after ART initiation have estimated life expectancy approaching that of the general population”. This is 10 years longer than those who started ART in 1996. This breakthrough owes much of its success to animal research that eventually lead to such clinical trials in humans. For example, the ability of AZT, an anti-retroviral medicine more commonly known as Retrovir and Retrovis, to act against HIV (without toxic side effects) was discovered in mice and rats.

How zebrafish help advance cancer research

Do sharks get cancer?

Despite the widely touted myth that sharks do not develop cancer, fish of all species do occasionally develop spontaneous tumours. This is of course also true for the most common of laboratory fish, the zebrafish. In this article, I will give you a brief overview of how the unique properties of the zebrafish have been exploited by scientists to generate very useful models to study the molecular basis of various cancers.

The use of zebrafish in cancer biology goes right back to when scientists first started using them in the lab, at which point it was noticed that they spontaneously develop various kinds of tumours. However, using these naturally occurring malignancies to study cancer development is rather impractical – not only would you need a lot of fish due to the rarity of these cancers, but there would also be a lot of heterogeneity as to what kinds of tumours develop. This is clearly not ideal if you want to study the molecular basis and treatment options of one particular cancer.

From disease to model

Subsequently, carcinogenic chemicals were used to speed up the onset of cancer development. However, similar to using naturally occurring tumours, this strategy is not terribly useful for studying one particular kind of cancer, as the resulting tumours can still be very diverse(although some substances tend to always cause the same type). This approach is mostly used to identify cancer-causing chemicals during human and environmental safety testing.

To study one specific cancer type in detail, scientists started to create zebrafish carrying particular loss of function mutations (i.e. genes that lose activity due to a change), or overexpressing certain cancer-causing oncogenes (i.e. genes that cause cancer when they are overly active). Usually, this leads to the early development of only one – or at most a few – types of cancer. The first of these more specific models were acute lymphoblastic leukaemia (ALL) models, but nowadays there are models for cancers of various tissues, ranging from the brain to the pancreas.

Most of these mutant models were originally created using mutagenizing drugs followed by screening for a phenotype, but recently the research community has shifted to more targeted techniques. These make use of novel genome editing tools, such as the CRISPR-Cas9 system to switch off certain genes. The overexpression of specific genes on the other hand was usually achieved using proteins called transposases to integrate novel genetic information, but very recently the CRISPR-Cas9 system has also been tweaked to do the same.

Why study cancer in fish?

So why would anyone bother to go through this effort and do all this in fish, if we can just use the more closely related mice or rats? Apart from the lower expense and easier generation of large numbers of fish, the main reason why fish are used is that visualizing particular cells is much easier than in other organisms. This is mainly due to two factors: the existence of various transgenic fish lines in which a particular cell type is labelled, and the existence of transparent adult fish (the casper fish, as below).

Casper_fish

Transparent fish like these Casper fish shown here allow researchers to track cells inside the body of adult fish much more easily than ever before

The ease of labelling specific cell types has been exploited elegantly for studying the clonal expansion of cancer cells that drives tumor growth in vivo as it happens, as well for the study of cancer metastases. Now that adult transparent zebrafish have enabled even easier in vivo imaging, the approach has been used successfully to visualize the process by which metastases arise and cancer cells distribute throughout the body.

Understanding the origins of melanoma

A recent paper from Charles Kaufman of the Harvard Stem Cell Institute and colleagues nicely illustrates how these advantages can be very powerful indeed. In this paper published in Science magazine, the researchers used a zebrafish melanoma model that they had developed a few years earlier which expresses gene variants associated with the cancer in humans, and combined this with a newly developed transgenic zebrafish line, in which cells expressing a gene known as Crestin, which is involved in early neural development , are labelled in green. The Crestin gene is normally not expressed in adult humans, but is switched on again in melanomas. This is also why this combination is interesting; emerging melanoma cells will re-express the normally silent gene and be labelled fluorescently.

This method allowed the researchers to track melanoma development from the very first tumour cell to the macroscopically visible tumour comprised of millions of cells. The very early changes that have to occur for cancer to develop can now be studied at much greater detail than before, as these very early tumorigenic cells are extremely hard (or completely impossible) to distinguish from normal cells if they are not labelled. In this specific case the researchers identified the activation of several gene pathways that are usually involved in neural crest development in the embryo as key events in the initiation of melanoma, and believe that their findings could lead to a new genetic test for suspicious moles in patients. Their work suggests a model of cancer development where normal tissue becomes primed for cancer when oncogenes are activated and tumour suppressor genes are silenced or lost, but where cancer develops only when a cell in the tissue reverts to a more primitive, embryonic state and starts dividing.

This paper increased our understanding of the underlying biology of the very early stages of tumour development, and a detailed understanding of these early steps might be very important when developing preventative or therapeutic drugs.

Image: Kaufman, C.K., et al, 2016. A zebrafish melanoma model reveals emergence of neural crest identity during melanoma initiation. Science, 351(6272), p.aad2197. DOI: 10.1126/science.aad2197

Image: Kaufman, C.K., et al, 2016. A zebrafish melanoma model reveals emergence of neural crest identity during melanoma initiation. Science, 351(6272), p.aad2197. DOI: 10.1126/science.aad2197

In summary, the field of zebrafish cancer biology has made great advances in the last decade and will continue to do so with the increasing popularity of genome editing techniques. The easy visualization of particular cell types leads to distinct advantages of using zebrafish, particularly for the study of metastases and the very early stages of cancer development.

Jan Botthof

References
Kaufman, C.K., Mosimann, C., Fan, Z.P., Yang, S., Thomas, A.J., Ablain, J., Tan, J.L., Fogley, R.D., van Rooijen, E., Hagedorn, E.J. and Ciarlo, C., 2016. A zebrafish melanoma model reveals emergence of neural crest identity during melanoma initiation. Science, 351(6272), p.aad2197. DOI: 10.1126/science.aad2197

Lung cancer immunotherapy, from PD-1 knockout mice to clinical trials

This morning many news outlets, including the BBC, covered a very promising development in lung cancer therapy; the successful clinical trial of the cancer immunotherapy Nivolumab in 582 patients with advanced lung cancer. While the extension of survival was modest in most patients, it is to be remembered that these were patients with advanced lung cancer, which is notoriously difficult to treat, so to see the survival time doubling in some patients was quite dramatic. Future trials will examine whether greater benefits are seen when Nivolumab is given earlier in the course of the disease.

Dr Alan Worsley, Cancer Research UK’s senior science information officer, told the BBC that harnessing the immune system would be an “essential part” of cancer treatment, and adding:

This trial shows that blocking lung cancer’s ability to hide from immune cells may be better than current chemotherapy treatments. “Advances like these are giving real hope for lung cancer patients, who have until now had very few options.”

Nivolumab works by blocking the activation of the PD-1 receptor protein found on the surface of many of the immune cells that infiltrate tumours. Another protein named PD-L1 binds to PD-1 and initiates a regulatory pathway that leads to the immune response being dampened down. Usually this is a good thing as it maintains immune tolerance to self-antigens and prevents auto-immune damage to healthy tissue, but unfortunately many solid tumour cells, such as lung cancer cells, also secrete PD-L1, and by activating PD-1 can evade destruction by the immune system. By blocking PD-1 Nivolumab turns off this protective mechanism and allows the immune cells to detect and destroy the tumour cells.

X-ray of a lung cancer patient. Image credit:

X-ray of a lung cancer patient. Image credit: “LungCACXR” by James Heilman, MD – Own work.

So how was this discovered? This is where the knockout mice come in. Scientists had observed in the 1990’s that PD-1 was highly expressed on the surface of circulating T- and B- immune cells in mice, but didn’t know what role PD-1 played, suspecting that it may be involved in increasing the magnitude of the immune response. To examine the role of PD-1 researchers at Kyoto University in Japan led by Professor Tasuku Honjo created a knock-out mouse line where the PD-1 gene was absent, and observed that this lead to some immune responses being augmented. In a paper published in 1998 they reported than rather than being an activator of the immune response PD-1 was actually involved in dampening down the immune response (1).

Subsequent studies in a range of PD-1 knockout mouse strains over the next decade explored the role of PD-1 in regulating the immune system, and also demonstrated that its ligand, PD-L1, could block immune-mediated tissue damage (2).  At the same time as these studies were taking place other research was demonstrating that PD-L1 was produced at high levels by tumour cells, first in   renal cell carcinoma in 2004 (3), but later in many other solid tumours including in lung cancer (4), and that this expression was associated with a decrease in the immune response to the tumour and a poorer prognosis.

This raised an obvious question: would blocking PD-1 improve the immune response against these tumours?

Work was already underway to find out. A paper published in 2007 by scientists from Nara Medical University in Japan demonstrated that blocking PD-L1 binding to PD-1 with monoclonal antibodies enhanced the immune response against established tumours in a mouse model of pancreatic cancer and acted synergistically with chemotherapy to clear the tumours without obvious toxicity (5). Subsequent studies with other monoclonal antibodies in a range of mouse and in vitro models of cancer showed similar results, including the humanized monoclonal antibody MDX-1106, now called Nivolumab, which was obtained by immunizing mice which had been genetically modified to produce human antibodies with human PD-1 (6).

Laboratory Mice are the most common species used in research

Cancer Immunotherapy – adding another accomplishment to an already impressive CV!

MDX-1106/Nivolumab showed promising results in a phase 1 trial against metastatic melanoma, colorectal cancer, castrate-resistant prostate cancer, non-small-cell lung cancer, and renal cell carcinoma, and following larger clinical trials (7) it was approved by the FDA for the treatment of melanoma that cannot be removed by surgery or is metastatic and no longer responding to other drugs, and more recently for metastatic squamous non-small cell lung cancer.

The story of the development of anti-PD-1 cancer immunotherapy is an illustration of how basic or fundamental biological research in animals informs medical science, and drives the discovery of new therapies. As cancer immunotherapy begins to transform the treatment of many previously untreatable cancers, it is well worth remembering that this revolution has its origin in the hard work of countless scientists working around the world, many of whom could only have guessed at the time where their efforts would eventually lead.

Breaking news, 1 June 2015: In another exciting report from the American Society of Clinical Oncology meeting in Chicago, researchers have reported that in a clinical trial of 945 patients with advanced metastatic melanoma a combination of Nivolumab with  Ipilimumab (another cancer immunotherapy that works through a different mechanism) stopped cancer advancing for nearly a year in 58% of cases, with the cancer still stopped in its tracks in many patients when the study period had ended. This is substantially greater effect than is seen with existing therapies, including Ipilimumab when administered alone, and shows how powerful cancer immunotherapies may be when two or more are combined.

Paul Browne

References:

  1. Nishimura H1, Minato N, Nakano T, Honjo T. “Immunological studies on PD-1 deficient mice: implication of PD-1 as a negative regulator for B cell responses.” Int Immunol. 1998 Oct;10(10):1563-72. PubMed: 9796923
  2. Grabie N, Gotsman I, DaCosta R, Pang H, Stavrakis G, Butte MJ, Keir ME, Freeman GJ, Sharpe AH, Lichtman AH. “Endothelial programmed death-1 ligand 1 (PD-L1) regulates CD8+ T-cell mediated injury in the heart.” Circulation. 2007 Oct 30;116(18):2062-71. PubMed 17938288
  3. Thompson RH1, Gillett MD, Cheville JC, Lohse CM, Dong H, Webster WS, Krejci KG, Lobo JR, Sengupta S, Chen L, Zincke H, Blute ML, Strome SE, Leibovich BC, Kwon ED. “Costimulatory B7-H1 in renal cell carcinoma patients: Indicator of tumor aggressiveness and potential therapeutic target.” Proc Natl Acad Sci U S A. 2004 Dec 7;101(49):17174-9. PubMed:15569934
  4. Zhang Y1, Huang S, Gong D, Qin Y, Shen Q. “Programmed death-1 upregulation is correlated with dysfunction of tumor-infiltrating CD8+ T lymphocytes in human non-small cell lung cancer.” Cell Mol Immunol. 2010 Sep;7(5):389-95. doi: 10.1038/cmi.2010.28. PubMed: 20514052
  5. Nomi T1, Sho M, Akahori T, Hamada K, Kubo A, Kanehiro H, Nakamura S, Enomoto K, Yagita H, Azuma M, Nakajima Y. “Clinical significance and therapeutic potential of the programmed death-1 ligand/programmed death-1 pathway in human pancreatic cancer.” Clin Cancer Res. 2007 Apr 1;13(7):2151-7. PubMed:17404099
  6. Brahmer JR, Drake CG, Wollner I, Powderly JD, Picus J, Sharfman WH, Stankevich E, Pons A, Salay TM, McMiller TL, Gilson MM, Wang C, Selby M, Taube JM, Anders R, Chen L, Korman AJ, Pardoll DM, Lowy I, Topalian SL. “Phase I study of single-agent anti-programmed death-1 (MDX-1106) in refractory solid tumors: safety, clinical activity, pharmacodynamics, and immunologic correlates.” J Clin Oncol. 2010 Jul 1;28(19):3167-75. doi:10.1200/JCO.2009.26.7609. PubMed: 20516446
  7. Topalian SL, Sznol M, McDermott DF, Kluger HM, Carvajal RD, Sharfman WH, Brahmer JR, Lawrence DP, Atkins MB, Powderly JD, Leming PD, Lipson EJ, Puzanov I, Smith DC, Taube JM, Wigginton JM, Kollia GD, Gupta A, Pardoll DM, Sosman JA, Hodi FS. “Survival, durable tumor remission, and long-term safety in patients with advanced melanoma receiving nivolumab.” J Clin Oncol. 2014 Apr 1;32(10):1020-30. doi: 10.1200/JCO.2013.53.0105. PubMed:24590637

Peritoneal Carcinosis and HIPEC: A second chance for patients, thanks to animal research

When we hear the phrase ‘animal research’ we tend to think about the development of new drugs for the clinical practice, or studying molecular pathways involved in the progression of disease; but we must also remember that the techniques used in the operation room are a consequence of biomedical research, including the use of animals. It is not just the creation of these techniques but also for the prior steps necessary for us to consider a surgical technique as an option when faced with a disease. An example of this is research into a type of cancer known as Peritoneal Carcinosis (PC) and the development of a technique, known as HIPEC, that may dramatically improve the prognosis for patients with this type of cancer.

What is the definition of Peritoneal Carcinosis? We describe this medical condition as the presence of neoplastic nodules caused by the spreading of a primary or secondary tumor in the peritoneal cavity. The peritoneal cavity, also called the abdominal cavity, is the largest body cavity and contains many of the major organs – such as the liver, kidneys, stomach and intestines – surrounded by a protective membrane known as the peritoneum.

Although PC is sometimes seen in primary tumours, such as peritoneal mesothelioma or Pseudomyxoma peritoneii, it is more frequently observed as a metastatic diffusion of gastroenteric (stomach and colon, primary) or gynaecologic (ovarian) tumors. In the second situation, we could see it as an advanced manifestation present at the same time as the primary neoplastic disease or appearing in the years following treatment of the tumour. This condition is often associated with a poor prognosis (about 6 months), depending on the site to which it spreads, the involvement of abdominal organs (like colon or liver) and how aggressive is the tumor at the moment of diagnose.

Peritoneal Carcinosis viewed by laparoscopy. Image: www.cancersurgery.us

Peritoneal Carcinosis viewed by laparoscopy. Image: http://www.cancersurgery.us

In the past, physicians have had only two options when combating the disease: systemic chemotherapy or palliative surgical therapy to debulk the tumor masses- removing as much as possible of tumors which cannot be entirely removed –  and prevent severe conditions such as bowel obstruction. Recently, surgical research developed another therapeutic approach, known as Cytoreduction (CR) associated with Hyperthermic intraperitoneal Chemotherapy (HIPEC). This technique consists of a two-part operation: during the first part, the surgeon debulks as much of the neoplastic nodules in the peritoneal cavity as possible, and in the second stage the peritoneal cavity is washed with a hyperthermic chemotherapy solution, where a solution containing a high concentration of chemotherapy drugs is heated to above body temperature (usually 41.5°-42.5°C) which increases absorption of the drugs by the target tumor and therefor their effectiveness.

The role of the hyperthermic solution and the possibility of using a high-dose of chemotherapic agent was developed through research in rodents and dogs: these studies demostrated that the peritoneal barrier itself is not a barrier that prevents substances from pass through it. This is in agreement with observations made during surgery in human patients, when we remove the peritoneum (for example, when we debulk a neoplastic nodule on a peritoneal surface with a technique known as peritonectomy) the rate at which drugs are cleared from peritoneal cavity is not significantly affected. [1]

Studies in dogs and subsequently in human volunteers demonstrated that the high concentration of chemotherapeutic drugs in the peritoneal cavity is not related to a high concentration of these in the blood stream [2]. In particular a key study undertaken in dogs by Rubin et al. [3], consisted of studying the effects of removing portions of the perotineum such as the the omentum, the mesentery or the small bowel on the clearance of substances like glucose, urea and insulin from the peritoneal cavity. Surprisingly, this experiment indicated that these operations do not influence the clearance of these substances. On the base of these observation, clinical studies were started on clearance of drugs from the peritoneal compartment:. These clinical studies demonstrated that the process observed in dog with other substances occured also with drugs and that, in some cases, the concentration of a drug within the peritoneal cavity could be extremely high without having effects on the concentration in the bloodstream.

A natural consequence of this evidence is that we can use a high-dose chemotherapy drug against these nodules without having systemic adverse effects on the patient, a problem frequently observed in conventional systemic chemotherapy. These studies also led researchers to reconsider the spreading of a tumour in the peritoneal cavity not as a systemic dissemination but as a local disease, and that treatment might be able to cure it rather than just have a palliative impact. If the peritoneal barrier can selectively allow only some molecules to pass through, it could have also an active role on slowing the diffusion of metastatic cancer cells.

This evidence, together with the property of hyperthermia in helping drugs to penetrate cancer cells [4], and avoid the normal defences that a tumor cell has, led to development of this ambitious surgical technique.

The results of this combined technique is clear. Against primary tumors this technique shows a high survival-rate after 5 years (reaching 96% in some studies [5]). Against secondary spreading of gastroenteric or gynaecological tumours it shows a lower efficacy that may be related to the more diverse biological characteristics of the tumor cells, to the physiopathological features (diffusion, tumor already treated with chemotherapy etc.) and also to the characteristics of the patient (such as clinical status, age, concomitant diseases) [6],[7],[8],[9]. The 5-years survival rate for PC from colorectal cancer, for example, according to studies conducted by Dr. Paul Sugarbaker of the Washington Cancer Institute, one of the most important researcher on this field, is around 40%, when the cytoreduction is complete and the disease is not so diffuse in the peritoneal cavity. [7] Also, this surgical approach can be uses a second time, in case of a recurrence of PC, and, ultimately, as a palliative treatment to delay complications and reduce suffering of the cancer patients.

These numbers could seem low but we have to consider that we’re facing a disease that is often fatal within six months if left untreated. This technique gives patients another chance until very recently, they did not have. Why? Because of research that was built up, in part, thanks to animal research

These results are a direct effect of research in the fields of surgery and oncology, from the including the development of more effective chemotherapic agents, research that, as we have said many times, requires the study of animals for everything from the basic understanding of the processes involved to the preclinical testing a new therapy’s effectiveness and safety profile.

Marco Delli Zotti

[1] Michael F. Flessner “The transport barrier in intraperitoneal therapy” Am J Physiol Renal Physiol 288:F433-F442, 2005. http://www.ncbi.nlm.nih.gov/pubmed/15692055

[2] Pierre Jacquet, Andrew Averbach, Arvil D. Stephens, O. Anthony Stuart, David Chang, Paul H. Sugarbaker “Heated Intraoperative Intraperitoneal Mitomycin C and Early Postoperative Intraperitoneal 5-Fluorouracil: Pharmacokinetic Studies” Oncology 1998;55:130–138 http://www.ncbi.nlm.nih.gov/pubmed/9499187

[3] Rubin J, Jones Q, Planch A, Rushton F, Bower J. “The importance of the abdominal viscera to pertioneal transport during peritoneal dialysis in the dog.” Am J Med Sciences 1986;292:203– 208. http://www.ncbi.nlm.nih.gov/pubmed/3752166

[4] Elwood P. Armour, Donna McEachern, Zhenhua Wang, et al. “Sensitivity of Human Cells to Mild Hyperthermia” Cancer Res 1993;53:2740-2744. http://www.ncbi.nlm.nih.gov/pubmed/8504414

[5] Yan TD, Black D, Savady R et al. “Systematic review on the efficacy of cytoreductive surgery and perioperative intraperitoneal chemotherapy for pseudomyxoma peritonei.” Ann Surg Oncol 2007;14:484-92 http://www.ncbi.nlm.nih.gov/pubmed/17054002

[6] Franco Roviello, Daniele Marrelli, Alessandro Neri, Daniela Cerretani, Giovanni de Manzoni, Corrado Pedrazzani, MD, Tommaso Cioppa, MD, Giacomo Nastri, MD, Giorgio Giorgi, Enrico Pinto
“Treatment of Peritoneal Carcinomatosis by Cytoreductive Surgery and Intraperitoneal Hyperthermic Chemoperfusion (IHCP): Postoperative Outcome and Risk Factors for Morbidity” World J Surg (2006) 30: 2033–2040 http://www.ncbi.nlm.nih.gov/pubmed/17006608

[7] Paul H. Sugarbaker “Review of a personal experience in the Management of Carcinomatosis and Sarcomatosis” Jpn J Clin Oncol 2001; 31(12)573-583 http://www.ncbi.nlm.nih.gov/pubmed/11902487

[8] Zanon C, Bortolini M, Chiappino I et al. “Cytoreductive surgery combined with intraperitoneal chemohyperthermia for the treatment of advanced colon cancer.” World J Surg. 2006 Nov;30(11):2025-32. http://www.ncbi.nlm.nih.gov/pubmed/17058031

[9] Bijelic L, Jonson A, Sugarbaker PH “Systematic review of cytoreductive surgery and heated intraoperative intraperitoneal chemotherapy for treatment of peritoneal carcinomatosis in primary and recurrent ovarian cancer.” Ann Oncol 2007;18:1943-50 http://www.ncbi.nlm.nih.gov/pubmed/17496308

To learn more about the role of animal research in advancing human and veterinary medicine, and the threat posed to this progress by the animal rights lobby, follow us on Facebook or Twitter.

 

Cancer Immunotherapy: A breakthrough made through animal research

The prestigious journal Science has published its top 10 Breakthroughs of the Year 2013, and top of the list is a development that promises to have a huge impact on the lives of millions of people in the coming decades – Cancer Immunotherapy.

The article focuses on three particular therapies that have recently shown great
promise in clinical trials – chimeric antigen receptors, anti-CTLA4 therapy, and anti-PD1 therapy – all of which highlight the fact that his is a field
where animal research is making an absolutely critical contribution.

Regular readers will remember that we discussed how studies in mouse xenograft models of acute lymphoblastic leukaemia (ALL) contributed to the development of chimeric antigen receptor (CAR) therapy that has now shown very promising results in clinical trials against ALL and Chronic Lymphocytic Leukemia, and as Science reports is now being evaluated against many other cancers.

The Science news article on cancer immunotherapy notes that a mouse study published in Science provided key evidence that antibodies that target the protein CTLA-4 – a receptor that acts to suppress the activate the T cells of the immune system – can increase the effectiveness of the immune system in eliminating tumor cells.

Similarly – as discussed in this open access review – the development of anti-PD1 immunotherapy started when was found that PD-1 knockout mice developed autoimmmune disorders, indicating that PD-1 played a role in regulating the immune response. Subsequent preclinical studies in a variety of mouse cancer models demonstrated that administration of antibodies against PD-1 greatly increased the ability of the immune system to attack the tumors, even well established and metastatic tumors.

Laboratory Mice are the most common species used in research

Cancer Immunotherapy – adding even more accomplishments to an already impressive CV!

The examples of CAR, Anti-CTLA4 and anti-PD1 therapies highlight how the field of cancer immunotherapy is maturing, but it is a field which has already delivered some important therapies.  For, example back in 2009 Emma Stokes wrote an article for this blog on the discovery and development of Rituximab, a chimeric antibody therapy that has revolutionized the treatment of B-cell cancers such as Non-Hodgkin’s lymphoma. This work has not stood still either, last week the BBC reported on the successful trial of a new chimeric antibody therapy named GA101 in patients with chronic lymphocytic leukaemia (CLL) and other B-cell conditions. GA101 targets the same protein – CD20 – as Rituximab, but was designed to induce a more powerful anti-cancer activity with fewer adverse effects. The abstract of the 2010 paper reporting on the preclinical research leading to the development of GA101 highlights the role played by studies in mouse models of cancer and in monkeys.

CD20 is an important target for the treatment of B-cell malignancies, including non-Hodgkin lymphoma as well as autoimmune disorders. B-cell depletion therapy using monoclonal antibodies against CD20, such as rituximab, has revolutionized the treatment of these disorders, greatly improving overall survival in patients. Here, we report the development of GA101 as the first Fc-engineered, type II humanized IgG1 antibody against CD20. Relative to rituximab, GA101 has increased direct and immune effector cell-mediated cytotoxicity and exhibits superior activity in cellular assays and whole blood B-cell depletion assays. In human lymphoma xenograft models, GA101 exhibits superior antitumor activity, resulting in the induction of complete tumor remission and increased overall survival. In nonhuman primates, GA101 demonstrates superior B cell–depleting activity in lymphoid tissue, including in lymph nodes and spleen. Taken together, these results provide compelling evidence for the development of GA101 as a promising new therapy for the treatment of B-cell disorders.”

Of course there are another 9 breakthroughs on Science’s list, and it’s notable that several others involve animal research. One of these is CRISPR, a technique that allows scientists to modify the genes of organisms in vivo or cells in vitro with unprecedented precision, and more recently showed potential in mouse studies as a therapy for genetic disorders. Another is CLARITY, a technique that renders brain tissue transparent so that it can be studied in more detail than has previously been possible, and which joins a range of new techniques that are part of a revolution in neuroscience. Of course there was also the news of the first human stem cells created through cloning by Professor Mitalipov at Oregon Health and Science University, a pioneering scientist whose work we have discussed on several occasions.

The choice of cancer immunotherapy, and indeed of this list as a whole, is a reminder at the end of what has been a very difficult year for science in several countries across the world of the extraordinary progress that is being made, and why it is vital to support the scientists who make it happen. As we bid farewell to 2013 and greet 2014 we can only guess at what new discoveries and breakthroughs the year will bring, but we also know that now – perhaps more than any time in recent history – we need to join together across the world to stand up for science!

Paul Browne

Animal Research Saved Both My Dogs

By Michael Brunt

Recently a post was written to dispel the myth that animals do not naturally suffer from the same diseases as humans.   I thought it appropriate to address another commonly held myth: that animals do not benefit from animal research.

The medications and therapies people use could only have been developed through biomedical research.  It is important to realize that we are quite similar to animals sharing nearly 99% of our genes with a mouse, for example.  Many of these therapies are developed for and used in both human and veterinary medicine.   The One Health Initiative is an excellent example of the partnership that exists between scientists, physicians and veterinarians.   These partnerships recognize the importance of collaborative efforts to treat disease and alleviate suffering irrespective of species.

Kiwi with Cancer

Kiwi with cancer.

Kiwi was adopted into my family at the age of two.  She was welcomed and celebrated as the first addition to our family.  A year later we had the pleasure to expand our family again and adopt Kiwi’s sister Karla.  Life moves along at such a quick pace until unexpected news makes time stand still.  Unfortunately, at the age of six Kiwi was diagnosed with chronic lymphocytic leukemia (CLL) and the news was devastating.  Kiwi was extremely lucky to have had access to an outstanding veterinary oncologist who recommended a treatment program of chlorambucil and prednisone that allowed her to live a clinically normal life for an additional six years.  The drug combination that Kiwi was prescribed is one of the chemotherapeutic drug combinations that can be used to treat CLL in humans.  Without these treatments my daughter would not have known and had such joyful memories of the first member added to our family. 

Karla

Karla with CDS

More recently Kiwi’s sister Karla, at the age of thirteen, began to be treated for canine cognitive dysfunction syndrome (CDS).  An aged companion animal can develop many similar age related neurological disorders as old humans.  Karla had a very  gradual increase in aged related behaviours including indoor urination, disorientation, confusion, staring, wandering, getting stuck in corners, sleep pattern disturbances, restlessness, barking, separation anxiety, drooling and obsessive licking which cumulatively had a significant impacted on her wellbeing.  Karla has been on a daily treatment of selegiline for nearly one year and it has dramatically improved her wellbeing and resolved most of her symptoms.  Selegiline is also used in human medicine to treat Parkinson’s disease, Alzheimer’s disease, attention deficit hyperactivity disorder, schizophrenia and depressive disorders.

Biomedical research provides benefits to all aspects of medicine.  Working together scientists, physicians and veterinarians improve the lives of countless millions of animals and humans around the world.

Michael Brunt