Tag Archives: leukemia

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

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

The end of cancer? A personal view.

My husband died of stage 4 metastatic esophageal cancer on August 19, 2011.

I have been an advocate for biomedical research, specifically involving animals, for decades. I go to work each and every day supporting researchers involved with discovering new cures or treatments. I dedicate time outside of those duties to promote education regarding the use of animals in such research. I want people to be able to make up their own minds free of rhetoric and sound bites empty of any real information. Research is part of who I am.

All of this became intensely personal for me, more so than it was, in February of 2010 when my husband was diagnosed. They did not need to explain to me how serious his diagnosis was. I already knew. I knew it was going to be a tough battle but he was a fighter. He was not ready to leave me or his daughters or the life we built. Not now. Not to cancer. No way.

He remained a fighter until his very last day on this earth. In our last conversation he told me cancer had only taken his body but he was still free and he will be waiting for me when the time comes for me to shed my body too. I still work in the same hospital where all his treatments had taken place and I eat at the same cafeteria where I bought all his food when he was in the hospital. I still see some of his caregivers in the hallways and they always ask me how I am. They are very caring people and I am sure each and every one of them would applaud an end to cancer. I know I would. I am pretty sure everyone that has been touched by this horrible disease would love to see an end to it, just as I am sure people were very happy to see an end to polio or small pox.

On Monday, author Sharon Begley published an article in The Daily Beast entitled “Could This Be The End Of Cancer?”outlining some of the new developments in the fight against cancer, particularly using vaccines. It is detailed but easy to read, and it was nice to see more information on some of the treatments my husband received. Research for cancer and many other diseases go on each and every day by thousands of people. Some of those people remember what life was like before the current vaccines we take for granted were widely used. In reading the evaluation results for the polio vaccine, you can see how many children were affected and see pictures of them in iron lungs. My generation has never known a friend confined to one of those thanks to those who continued the research that lead to the vaccine. The mortality rates for small pox were up to 35% and yet according to the WHO this disease was eradicated in 1979, thanks to those who developed the first vaccine. I doubt anyone who was born after 1975 could really tell you what small pox looked like without looking it up thanks to those who continued to search and refine the current vaccine.

Immunotherapy – developed through animal research – offers new hope to patients with Chronic Lymphocytic Leukemia, and is an example of recent advances in cancer treatment discussed by Sharon Bagley

Without research, both with animals and humans, or those dedicated to searching for answers, no cures are possible. Will we see vaccines for all cancers in the next 30 years? No one can answer that, just like no one can give you a date when the human race will finally stop wars. But does that mean we should stop looking? Stop striving? Stop hoping for a cure? Absolutely not. Polio and small pox are simple diseases if compared with the complexity of cancer. It is going to take lots of time, lots of man hours and a lot of dedication from a lot of people to finally put this monstrous disease in the “eradicated” file.

It is also going to take a lot of money. On Ms. Begley’s article page is a comment regarding this money. The poster states:

This is a nice read, but … this will never happen. At least not in our life time as Cancer has become a big business. I am a ovarian 3 cancer survivor and I can tell you that there would be a lot of people out of work if there ever was a cure. The Government would fail. “

Do you suppose she is happy about the treatments she received for her disease that has extended her life? Would she reject a vaccine in favor of current treatments if her cancer was to reappear? Somehow I think she would take the easier treatment.

Is finding cures and treatments expensive? You bet it is. Is funding from the government and charities vital to this research? Absolutely. Without it we would not be able to hire the scientists, the biologists, the doctors or the nurses who work tirelessly each and every day, not only to find a cure, but to make every day in the life of a cancer patient the best it can be. And believe me, we are not a rich bunch. We shop at dollar stores and check the clearance section too just like so many people do in our current economic state.

However…

Do you think any one of us would give up their job to find that cure tomorrow? I know I would. In a heartbeat. It is too late to save my husband. But if I could save everyone else, every kid, mother, father, wife, husband and friend, from having to go through what I just went through, I would collect my last paycheck today. Right now.

But until that cure happens, we are going to come to work and continue searching, perfecting, refining and aiming for that day to come. And it will come.

Pamela Bass

A breakthrough against Chronic Lymphocytic Leukemia…thank the mice!

A challenge that science communicators frequently face when discussing the process whereby a scientific discovery eventually leads to a medical breakthrough is the time that this often takes, indeed by the time that the reports of exciting clinical trial outcomes start to appear in the press the role of the scientists who made the initial discoveries is often relegated to a passing comment…if it is mentioned at all. An example of this comes from the Weizmann Wave blog, produced by the Weizmann Institute of Science.

You may remember reports last month on the very promising results of a small clinical trial where a new immunotherapy technique was used to eradicate cancer cells in patients with Chronic Lymphocytic Leukemia (CLL), a blood cancer for which currently available treatments are often inadequate.  That trial, conducted by scientists at the University of Pennsylvania led by Professor Carl June, involved removing T-cells from the patient, treating the cells with a lentiviral vector that encodes for a Chimeric Antigen Receptor which recognises a protein named CD19 that is found on B-cells, including the cancer cells responsible for CLL, and then infusing the transformed T-cells back into the patients.  As the reported in the Los Angeles Times the results were dramatic, within a few weeks of the infusion the modified T-cells expanded rapidly and targeted the cancer cells in all three paients, so that a year later two of the three patients were still in complete remission.

It’s exciting stuff but as the Weizmann Wave reports the Press Release issued by Penn Medicine noted that this was a “cancer treatment breakthrough 20 years in the making” but “didn’t, however, explain those “20 years in the making.””. The Weizmann Wave goes on to discuss the pioneering basic scientific research undertaken by Professor Zelig Eshhar at theWeizman Institute of Science in the late 1980’s, which you can read about here.

Of course between the basic research undertaken by Prof. Eshhar and his colleagues in the 1980’s and the clinical trial whose outcome was announced last month there was a lot of work to be done. It would be impractical to describe all the different discoveries that made this immunotherapy possible, but one discovery in particular highlights the importance of animal research to this breakthrough.

There have been previous attempts to use Chimeric Antigen Receptors to target T-cells to attack cancer, but these had disappointing results in clinical trials.  A major improvement made by the University of Pennsylvania team was to include an additional motif – named the CD137 co-stimulatory molecule- which greatly enhances the cancer killing ability of the infused T-cells.  In a recent paper published in the Journal of Cancer the University of Pennsylvania team point out that the decision to include CD137 (called 4-1BB in mice) in their Chimeric Antigen Receptor construct was based on promising results in studies undertaken in mice:

 Our group has tested a CAR directed against CD19 linked to the CD137 (4-1BB) co-stimulatory molecule signaling domain to enhance activation and signaling after recognition of CD19. By inclusion of the 4-1BB signaling domain, in vitro tumor cell killing, and in-vivo anti-tumor activity and persistence of CART-19 cells in a murine xenograft model of human ALL (acute lymphocytic leukemia) is greatly enhanced”

Indeed, in a paper published by Professor June and colleagues in the journal Molecular Therapy in 2009 they describe this work in much more detail, highlighting just how groundbreaking the results were:

Previous in vitro studies have characterized the incorporation of CD137 domains into CARs.10,11,29 Our results represent the first in vivo characterization of these CARs and uncover several important advantages of CARs that express CD137 that were not revealed by the previous in vitro studies. We demonstrated that CARs expressing the CD137 signaling domain could survive for at least 6 months in mice bearing tumor xenografts. This may have significant implications for immunosurveillance, as well as for tumor eradication. For example, in a mouse prostate cancer xenograft model, survival of CAR+ T cells for at least a week was required for tumor eradication.30

Long-term survival of the CARs did not require administration of exogenous cytokines, and these results significantly extend the duration of survival of human T cells expressing CARs shown in previous studies.17,31 To our knowledge, this is the first report demonstrating elimination of primary leukemia xenografts in a preclinical model using CAR+ T cells. Furthermore, complete eradication was achieved in some animals in the absence of further in vivo therapy, including prior chemotherapy or subsequent cytokine support.

The long-term control of well-established tumors by immunotherapy has rarely been reported. Most preclinical models in a therapeutic setting have tested tumors that have been implanted for a week or less before initiation of therapy.32 After establishing leukemia 2–3 weeks before T cell transfer, we found that many animals had long-term control of leukemia for at least 6 months. The efficacy of targeted, adoptive immunotherapy in this xenograft model of primary human ALL compares favorably to our prior experience testing the antileukemic efficacy of single cytotoxic (ref. 27 and data not shown) or targeted agents,26 where we have observed extension of survival but not cure of disease. Additionally, we have not previously observed the ability to control xenografted ALL for a period of as long as 6 months.”

These results led directly to the clinical trial reported last month.

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. As Professor Bruce Levine points out in the video above, the key to success is often keeping one hand in the basic research lab and the other in the clinic.

Paul Browne

Addendum: Scienceblogger Erv has written an excellent commentary on this study

Mice pave the way to a cord blood transplant advance

Leukemia is a cancer of the blood or bone marrow that affects over 200,000 Americans and still kills thousands every year despite the great progress made over recent decades in developing  effective treatments for many leukemia types.  When undergoing treatment for leukemia many patients require hematopoietic stem cell (HSC) transplantation to replace the blood stem cells that are killed off along with the cancer cells by radiation or chemotherapy.  The most usual source of such HSCs is the blood or bone marrow of the patient themselves or a donor, but unfortunately it is often not possible to use the patient’s own cells because of the risk that some might be cancerous, while finding a donor whose cells are compatible with the patient is difficult, especially for members of ethnic minorities.  As a result of the growing numbers of patients waiting for suitable cells to become available for transplant scientists have turned to another source;  umbilical cord blood (CB) cells.  CB cells have the useful property of being partially immunologically privileged so that the match between the donor and recipient does not have to be as exact as for bone marrow or blood derived cells, but this advantage comes at the price that only small amounts of CB cells can be obtained from each umbilical cord.  To overcome this limitation on the use of CB cells scientists have sought to develop methods to expand in vitro the number of cells obtained from the umbilical cord before transplanting them into patients, and scientists recently announced the first successful clinical trial of in vitro expanded CB cells in leukemia patients (1) after a decade of research and refinement in mice.

Blood smear of the final blast crisis phase of chronic myelogenous leukemia, a disease whose treatment often includes hematopoietic stem cell transplant. Reproduced courtesy of the CDC Public Health Image Library.

Our story doesn’t however start with mice but with the fly Drosophila melanogaster,  a key model organism in developmental research.  Almost a century ago the geneticist Thomas Hunt Morgan identified a strain of D. Melanogaster which had characteristic notches in their wings, so the gene whose inactivation caused this trait was named Notch.  Since the revolution in molecular biology got underway in the 1980’s scientists studying D. melanogaster have learned that Notch  is a cell surface receptor which regulates the development of many tissues, and found that it plays a similar role in many other species, including mammals which have 4 versions of the Notch gene.  This all became relevant to the expansion of CB cells when a team lead by Dr. Irwin D. Bernstein of the Fred Hutchinson Cancer Research Center found that the Notch 1 gene was expressed in human hematopoietic  stem cells and decided to investigate the role of Notch 1 in regulating the ability of these cells to expand their numbers and subsequently differentiate into all the many different kinds of blood cell. A decade ago they used a modified virus to express Notch 1 in mouse bone marrow hematopoietic stem cells and found that these cells became immortal, producing far more cells than hematopoietic stem cells normally do in vitro, and that these cells could be made to differentiate into a wide range of blood cell types in vitro. However they found that while the Notch 1 expressing cells were incorporated into the bone marrow and gave rise to a wide variety of cell types when  transplanted along with unmodified hematopoietic stem cells into mice whose own bone marrow stem cells had been removed by radiation treatment , they did not do so when transplanted on their own (2).  This indicated that while using a viral vector to express Notch1 continually enhanced the ability of hematopoietic stem cells to self-renew and multiply it also impaired the other vital characteristic of these cells, namely their ability to differentiate into mature blood cells.

To overcome this problem Dr. Bernstein’s team turned to a modified version of Delta-1, the natural ligand of Notch, which could be used activate the Notch pathway and expand hematopoietic stem cells in vitro. When the cells were transplanted into the bone marrow the notch pathway would no longer be activated to such an extent and the cells could differentiate normally.  In the years that followed they tested and refined their Notch-mediated in vitro expansion technique, first using mouse bone marrow hematopoietic stem cells and when that was successful switching to human cord blood hematopoietic cells.  All this time they evaluated the ability of modified cells to engraft and repopulate blood and thymus with the full spectrum of blood cells by transplanting them into mice; including NOD-SCID mice which were genetically modified to be immunodeficient so that they could receive human cord blood cells that can then develop into a functioning immune system.

In the latest paper published online in Nature Medicine (1) Colleen Delaney and colleagues describe the final refinements to their technique. One major refinement concerned the source of the cell population to be expanded.  In previous studies they used a sub-population of CB  cells termed CD34+CD38- as the starting population in their in vitro expansion, a reasonable decision since CD34+CD38- are the most primitive form of hematopoietic cell with the greatest capacity to develop into the full range of other blood cell types.  Unfortunately the purification of CD34+ CD38- cells is a process that itself entails the loss of many CB hematopoietic cells, not an ideal situation when they are already in short supply.  So they compared a starting population of CD34+ cells with the more highly purified CD34+ CD38- population, and found that the CD34+ derived cells actually performed better when transplanted into mice.  The Notch-mediated in vitro expansion technique they had developed and refined over the preceding decade had produced cells that were able to engraft into the bone marrow a lot more quickly than untreated CB  hematopoietic stem cells and start producing immune cells earlier and in greater numbers,  it was now time to take it into human trials.

The phase I trials reported in the Nature Medicine paper involved transplanting the in vitro expanded CB cells alongside unmanipulated CB cells into high-risk leukemia patients, with the primary objective of evaluating the safety of the procedure.  At the end of the trial it was apparent that not only was the procedure not associated with any unexpected safety concerns, but that engraftment of the transplanted cells and production of immune cells was significantly enhanced, enabling the immune systems of the patients to recover more quickly.  While there are more and larger trials to come, this outcome raises the hope that umbilical cord blood cells will in future be able to offer many more leukemia patients the chance of earlier treatment and a quicker recovery.

Paul Browne Ph.D.

1)      Delaney C. et al. “Notch-mediated expansion of human cord blood progenitor cells capable of rapid myeloid reconstitution.” Nat. Med. Published online 17 January 2010 doi:10.1038/nm.2080

2)      Varnum-Finney B. Et al. “Pluripotent, cytokine-dependent, hematopoietic stem cells are immortalized by constitutive Notch1 signaling” Nat. Med. Volume 6, Number 11, Pages 1278-1281 (2000) doi: 10.1038/81390