Tag Archives: cancer

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

Defeating Leukemia: A smile that says “Thank the mice”

A couple of days ago the New York times published a heart warming story about a young girl named Emma Whitehead whose acute lymphoblastic leukemia – which had previously defied all therapies – has gone into full remission following treatment with a novel gene therapy that programmed her immune system to target the cancer cells. The New York Times report noted that the therapy used a vector based on the HIV-1 virus to deliver genes – known as a chimeric antigen complex (CAR) – to modify  Emma’s T-cells so that they would destroy the leukemia cells.  This isn’t the first example of how scientists are using the properties of this deadly virus to develop powerful new therapies, back in 2009 we discussed how such a lentiviral vector was used to treat the genetic disease cerebral X-linked adrenoleukodystrophy. Emma wasn’t the only patient to benefit from this therapy developed by scientists at the University of Pennsylvania, 9 other patients with intractable leukemia have experienced partial or full remissions.

Emma2

Earlier today I received an e-mail from a long-time reader of this blog asking:

Did I dream there was an SR post on this already?”

Well my friend, you were not dreaming.

Last year we published a post entitled “A breakthrough against Chronic Lymphocytic Leukemia…thank the mice!” which discussed the role of animal research in the development of this therapy, and in particular that of mice the evaluation of chimeric antigen complexes in order to identify a complex that would induce a long-lasting immune response against the cancer cells. Our post also linked to an article on the Weizmann Wave Blog entitled “Cancer Breakthrough 20 Years in the Making” which described the basic biomedical research – mice were again crucial – that underpinned this field.

At the time I concluded the post by saying:

So there you have it, behind the headlines are years of graft by hard-working and innovative scientists, who utilised a wide range of experimental approaches – among which animal studies figure prominently – to develop a novel therapy for CLL.”

And I say the same again today. At a time when funding of medical research in the US is facing the threat of very damaging cuts, Emma’s story is a reminder of why you should write to your Senator and Congressional Representative today!

Paul Browne

Hope for young cancer victims as stem cell transplantation restores functioning sperm in monkeys.

Chemotherapy plays a crucial role in treating many cancers, but unfortunately some chemotherapy has a side effect of destroying the spermatogonial stem cells that are responsible for producing sperm.  Adult men who need to undergo chemotherapy have the option of cryopreserving their sperm in order to give themselves the option of having children in the future, but for young cancer patients who have not yet gone through puberty this is not an option.

Today the BBC news reports on a major advance; scientists at the University of Pittsburgh and Magee-Womens Research Institute have announced that they had taken samples of the spermatogonial  stem cells from 12 adult and 5 prepubescent male macaques and cryopreserved them, administered the macaques with a chemotherapy course that eliminated the remaining spermatogonial stem cells (SSCs), and then thawed and implanted the preserved stem cells after the course of chemotherapy had ended. Nine out of 12 adult monkeys and three out of five prepubescent monkeys were later able to produce sperm again, and additional studies showed that these sperm were capable of fertilising eggs. They were able to show that the sperm were produced by transplanted SSCs and not stem cells that had survived chemotherapy by labelling the transplanted cells with a harmless virus that expressed a Green Fluorescent Protein tag (another interesting application of this Nobel Prize winning technology).

Macaque monkeys play a crucial role in this and many other fields of medical research. Image courtesy of Understanding Animal Research/Wellcome Images

The study by Dr Kyle Orwig and colleagues, published on Thursday in Cell Stem Cell (1), publish work builds on almost 20 years of research, and they discuss how studies in mice and rats initially demonstrating the feasibility of SSC transplantation, while follow-up studies in a range of large animals (including pigs, sheep and monkeys) provided further support for the approach.

The feasibility of this approach is supported by observations in lower animal models that SSCs from donors of all ages, newborn to adult, can regenerate spermatogenesis (Shinohara et al., 2001; Ryu et al., 2003) and that SSCs can be cryopreserved and retain spermatogenic function upon thawing and transplantation (Dobrinski et al., 1999, 2000; Brinster, 2002).

Large animal models are critical for examining the safety and feasibility of experimental therapies before they are translated to the clinic. SSC transplantation has been reported in seven previous large animal studies (Table S1 available online). All of those studies, except for one in the boar (Mikkola et al., 2006), employed irradiation to destroy spermatogenesis and cause infertility. There is a dearth of information on the efficacy of SSC transplantation in chemotherapy-treated large animals, probably due to the significant challenges associated with clinical management of animals treated systemically with highdose chemotherapies that cause severe hematopoietic deficits (Hermann et al., 2007). However, the importance of this experimental paradigm should not be overlooked because high-dose alkylating chemotherapies are used routinely for conditioning prior to hematopoietic stem cell (HSC) transplantation and are associated with high risk of infertility (Wallace et al., 2005”

This study added to this previous research by demonstrating for the first time that it is possible for cryopreserved SSCs to generate functioning sperm in a primate following high dose chemotherapy, and is a major step forward in this field.

Experts in reproductive science have welcomed this study, with Professor Allan Pacey on the University of Sheffield saying:

This report is a very useful step forward and clearly shows that the science of spermatogonial stem cells transplantation might one day work for humans. And, although the authors report relatively low efficiency so far, in the context of someone who does not have any banked sperm to fall back on, these odds are probably very encouraging to make this kind of approach worthwhile.”

It’s certainly true that further research in macaques is needed to ensure that the sperm that result from this technique give rise to healthy offspring, and that cancer cells are not inadvertently transplanted with the SSCs. The second potential problem is already being addressed by Dr. Orwig’s team, who last year demonstrated that where there is a risk that SSCs may be contaminated with cancer cells, it is possible to screen to remove the cancer cells before transplantation. It is also worth noting that such autologous hematopoietic stem cell transfer using cells isolated from a patient’s own bone marrow is a standard part of therapy for some cancers such as lymphoma, and in this week’s paper Dr. Orwig and colleagues highlight the role of animal research in developing this therapy (for which Joseph Murray and Donnall Thomas shared the 1990 Nobel Prize in Physiology or Medicine):

Adult stem cell transplantation for homologous tissue regeneration was first described for primates in the 1950s when bone marrow stem cells were used to reconstitute the hematopoietic systems of monkeys and humans treated with chemotherapy or radiation (Crouch and Overman, 1957; Thomas et al.,1957). Large animals, primarily the dog and monkey, were instrumental for establishing the safety, feasibility, and range of applications for bone marrow transplantation. Today, approximately 50,000 bone marrow or HSC transplant procedures are performed worldwide each year for diseases ranging from cancer to thalassemia, sickle cell anemia, and autoimmune and immune-deficiency disorders (Appelbaum, 2007; Powellet al., 2009).”

Such history is very encouraging, but it is worth paying attention to the final paragraph of the this week’s Cell Stem Cell paper, which notes the great potential of the technique, stresses the need for further development and evaluation, and points out that even when animal studies have played their part further development and study in human trials will be required to realise the full potential of the SSC transfer:

Several promising techniques are in the research pipeline (i.e., SSC transplantation,testicular tissue grafting or xenografting,and in vitro development of gametes) that may allow patients receiving gonadotoxic therapies to preserve their future fertility (Brinster, 2007; Rodriguez-Sosa and Dobrinski, 2009; Sato et al., 2011). SSC transplantation has the unique potential to regenerate spermatogenesis in the autologous environment of the seminiferous tubules, enabling the recipient male to father his own genetic children, possibly through normal coitus. As with hematopoiesis, large animal models that are relevant to human anatomy and physiology will be important for translating the SSC transplantation technique to the human fertility clinic. Considering the successful regeneration of spermatogenesis in the nonhuman primate model reported here and the fact that patients are already preserving testicular tissue and/or cells, clinical translation of the SSC transplantation technique appears imminent. Responsible development of the technology in a clinically relevant nonhuman primate system will help to address issues of safety and feasibility. As with hematopoiesis, the clinical significance and breadth of applications for SSC transplantation will ultimately be established in human patients.”

Dr. Orwig and his colleagues at University of Pittsburgh and Magee-Womens Research Institute for a study that will bring hope to many thousands of cancer patients, and we congratulate them on it, but they also deserve a pat on the back for an excellent paper that shows their appreciation for the long-view of medical research.

1)      Brian P. Hermann, Meena Sukhwani, Felicity Winkler, Julia N. Pascarella, Karen A. Peters, Yi Sheng, Hanna Valli, Mario Rodriguez, Mohamed Ezzelarab, Gina Dargo, Kim Peterson, Keith Masterson, Cathy Ramsey, Thea Ward, Maura Lienesch, Angie Volk, David K. Cooper, Angus W. Thomson, Joseph E. Kiss, Maria Cecilia T. Penedo, Gerald P. Schatten, Shoukhrat Mitalipov, Kyle E. Orwig “Spermatogonial Stem Cell Transplantation into Rhesus Testes Regenerates Spermatogenesis Producing Functional Sperm” Cell Stem Cell – Vol. 11, Issue 5, pp. 715-726 (2012)

ERV blogs on GMO Herpes vs severe cancer pain

As gene therapy emerges as one of the hottest areas of medical research, one thing that is striking is how it employs viruses – sometimes very nasty viruses - to deliver the gene to where it is needed in the human body.

Yesterday virologist Abbie Smith discussed another excellent example of this on the ERV blog in a post entitled “GMO Herpes vs. severs cancer pain”, describing how scientists at the Universities of Michigen and Pittsburgh have used a genetically modified herpes virus to deliver the preproenkephalin gene – which produced a precursor to pain-killing opiates – to the nerve cells of terminal cancer patients who were suffering from severe pain.

Abbie remarks that “This was one of the most depressing, yet hopeful, papers I have ever read.”. It’s difficult to disagree, after all most of the patients participating in the trial died within 3 months of it starting. But to focus on this sobering statistic would miss the reason for this study, namely that the pain-relief available to patients with severe chronic pain is often inadequate, as the drugs are not specific enough and cause unacceptable side effects when used at the high doses often required for prolonged periods of time. By targeting the opiate molecules to the nerve ccells themselves these side effects can be avoided, and more effective pain relief provided.

The paper “Gene Therapy for Pain: Results of a Phase I Clinical Trial” is available for anyone to read in PubMed Central and makes it very clear that this is a therapy that was discovered, evaluated and refined in animal models of different types of pain before entering this first clinical trial. The first two paragraphs of the introduction noting that:

A significant limitation to the development of analgesic drugs is that off-target effects at doses below the maximal analgesic threshold restrict the ability to selectively interrupt nociceptive neurotransmission1. To address this limitation, we developed a series of replication defective HSV-based vectors to deliver gene expression cassettes directly to DRG neurons from skin inoculation 2, 3. The anatomically defined projection of DRG axons allows targeting of specific ganglia by injection into selected dermatomes. In preclinical studies, the release of anti-nociceptive peptides or inhibitory neurotransmitters in spinal dorsal horn from the central terminals of transduced DRG neurons effectively reduced pain-related behaviors in rodent models of inflammatory pain, neuropathic pain, and pain caused by cancer4-9.

The human PENK gene encodes for preproenkephalin, a precursor protein proteolytically cleaved to produce the endogenous opioid peptides met- and leu-enkephalin. In the spinal cord, enkephalin peptides inhibit pain signaling through actions at presynaptic opioid receptors located on central terminals of primary afferent nociceptors and postsynaptic opioid receptors on second order neurons involved in nociceptive neurotransmission10. HSV vectors expressing opioid peptides appear to be particularly effective in animal models of inflammatory and cancer pain4, 5, 8.”

And in the conclusion:

In preclinical animal studies, skin inoculation of HSV vectors expressing PENK reduce acute hyperalgesic responses27, and reduce pain-related behaviors in models of arthritis28, formalin injection4, peripheral nerve damage6 and bone cancer5. Because this was the first human trial employing HSV vectors to achieve gene transfer, we elected to carry out the phase 1 clinical trial for safety and dose-finding in patients with pain caused by cancer…This Phase I clinical trial primarily addressed the question of whether intradermal delivery of NP2 to skin would prove to be safe and well tolerated by subjects. The small number of patients and the absence of placebo controls warrant circumspect interpretation of the secondary outcome measures. But the observation that subjects in the low dose cohort had little change in the NRS or SF-MPQ while subjects in the higher dose cohorts reported substantial reduction in NRS and improvement in SF-MPQ is encouraging.”

Encouraging is possibly an understatement, seeing clear evidence of therapeutic benefits in a Phase I trial like this is very promising, or as Abbie puts it “A trial turning out this successful is a great starting point for optimizing this kind of therapy.”.

Paul Browne

p.s. Those interested in a more detailed account of the research that led to this clinical trial can find it in this review published in 2008 and available to read online for free.

Cancer Stem Cells: Mouse studies lead to paradigm shift in cancer research

For the past 15 years one of the most intriguing ideas in cancer research has been that the growth and spread of most – if not all – cancers is driven by cancer stem cells. The hypothesis is that only a tiny proportion of cancer cells, cancer stem cells, have the stem cell-like ability to proliferate indefinitely to produce cells that can differentiate into other cancer cell types. It suggests that the reason why cancer often returns after apparently being eradicated is that while the therapy (surgery/radiation/chemotherapy) may remove the differentiated cancer cells it fails to remove all the cancer stem cells, whose subsequent proliferation results in the cancer’s return.

Multicolored intestine tissue in genetically modified mice allows scientists to track which cells give rise to tumors.
Credit: A. G. Schepers et al., Science (2012) DOI: 10.1126/science.1224676

Today 3 teams of scientists have announced important results that provide the strongest evidence to date that cancer stem cells are indeed at the heart of cancer proliferation.

The first evidence that only a small minority of cancer cells may have the ability to proliferate indefinitely came from a study of leukemia cells in 1997, when Dr Dominique Bonnet and Dr John Dick, then both working at the University of Toronto, observed that when they injected a variety of acute myeloid leukemia (AML) cell populations obtained from human biopsy into immunodeficient mice and analyzed which cells gave rise to leukemia cells in the mice, and found that regardless of the characteristics of injected AML cells the cells that initiated the leukemic cell populations in the mice always expressed the cell surface marker CD34 and lacked the cell surface marker CD38, a key characteristic of stem cells.

Since then similar observations have been made for a wide variety of cancer types, and scientists have discovered important new facts about cancer stem cells, for example in 2009 we discussed how scientists at Stanford University had used genetic modification of bone marrow stem cells to show that leukemia stem cells were very similar to embryonic stem cells.  However, these studies all involved the transplantation of cancer cells into mice, and there has always been some concern that the manipulation of these cells during their isolation from humans and sorting into specific populations before injection into mice may have affected their behavior.

Today, three independent studies of mouse models of brain, skin and intestinal tumours, led respectively by Dr Luis Parada at the University of Texas Southwestern Medical Center, Dr Benjamin Simmons of the Gurdon Institute and Dr Cédric Blanpain of the Free University of Brussels, and Dr Hans Clevers of the Hubrecht Institute, and published in the prestigious scientific journals Nature and Science,  provide the first evidence that cancer stem cells do arise during tumour formation in intact organs, and drive tumour formation.

What these studies all share is that they were able to do this because rather than injecting cancer cells into the mice they used genetically modified mice in which cancer develops spontaneously. Using additional genetic modification to label certain types of cells they were able to track the different cell types involved in the growth and spread of cancer, and even assess the differing effects of standard cancer therapies and therapies that included drugs that specifically target cancer stem cells.

There is an excellent discussion of the three projects and their implications for cancer research in Nature News, and Science Now also offers a informative prespective on the work.  From its very first paragraphthe Nature News article highlights how these studies provide crucial information that could not be obtained through other methods:

Cancer researchers can sequence tumour cells’ genomes, scan them for strange gene activity, profile their contents for telltale proteins and study their growth in laboratory dishes. What they have not been able to do is track errant cells doing what is more relevant to patients: forming tumours. Now three groups studying tumours in mice have done exactly that. Their results support the ideas that a small subset of cells drives tumour growth and that curing cancer may require those cells to be eliminated.”

Commenting in an article in the LA Times, Dr. Owen Witte of the UCLA Broad Stem Cell Center was clear about what these results mean for cancer research.

People can stop arguing…Now they can say, ‘OK, the cells are here. We now need to know how to treat them.’ ”

And “how to treat them” will not be an easy problem to solve, perhaps drugs that target the cancer stem cells or prevent their development may be the answer, but as the Nature News, Science Now and LA Times articles stress we don’t yet know enough about the origins of cancer stem cells to be sure which approach will work.

What is true is that thanks to advanced animal research methods a huge gap in our knowledge of how cancer develops and spreads – a gap that we only recently realised existed – has been filled. As research accelerates to turn this new knowledge into effective cancer therapies we can be certain of one thing; animal research will continue to provide key insights that turn hypothesis into cures.

Paul Browne