April 30, 2013 by

The dual effect of MSCs on tumour growth and tumour angiogenesis

Michelle Kéramidas, Florence de Fraipont, Anastassia Karageorgis, Anaïck Moisan, Virginie Persoons, Marie-Jeanne Richard, Jean-Luc Coll and Claire Rome

Abstract (provisional)
Introduction

Understanding the multiple biological functions played by human mesenchymal stem cells (hMSCs) as well as their development as therapeutics in regenerative medicine or in cancer treatment are major fields of research. Indeed, it has been established that hMSCs play a central role in the pathogenesis and progression of tumours, but their impact on tumour growth remains controversial.

Our results suggest that hMSCs injection decreased solid tumour growth in mice and modified tumour vasculature, which confirms hMSCs could be interesting to use for the treatment of pre-established tumours.

Methods

In this study, we investigated the influence of hMSCs on the growth of pre-established tumours. We engrafted nude mice with luciferase-positive mouse adenocarcinoma cells (TSA-Luc+) to obtain subcutaneous or lung tumours. When tumour presence was confirmed by non-invasive bioluminescence imaging, hMSCs were injected into the periphery of the SC tumours or delivered by systemic intravenous injection in mice bearing either SC tumours or lung metastasis.

Results

Regardless of the tumour model and mode of hMSC injection, hMSC administration was always associated with decreased tumour growth due to an inhibition of tumour cell proliferation, likely resulting from deep modifications of the tumour angiogenesis. Indeed, we established that although hMSCs can induce the formation of new blood vessels in a non-tumoural cellulose sponge model in mice, they do not modify the overall amount of haemoglobin delivered into the SC tumours or lung metastasis. We observed that these tumour vessels were reduced in number but were longer.

Conclusions

Our results suggest that hMSCs injection decreased solid tumour growth in mice and modified tumour vasculature, which confirms hMSCs could be interesting to use for the treatment of pre-established tumours.

Original Link: http://stemcellres.com/content/4/2/41/abstract

Filed Under: Cancer, Mesenchymal Stem Cells, News, Stem Cell Research Tagged With: , , , , , ,
May 13, 2011 by

Killing of the iPS Field?

Zhao et al. Nature.
Embryonic stem cells are associated with numerous ethical dilemmas. The creation of equivalents of ES cells through retrodifferentiation led to a new area of research that does not require destruction of life. Specifically, it was discovered that any adult cell can be transfected with several genes, which results in the cell taking the phenotype and function of cells that appear to be very similar to embryonic stem cells. These cells can give rise to any tissue that embryonic stem cells give rise to, and unfortunately, like embryonic stem cells for teratomas (tumors). We made a video to explain this http://www.youtube.com/watch?v=_RLlUdJLy74.
One of the most exciting medical properties of iPS cells is that they can be made from a donor and theoretically the cells and their differentiated offspring should not be rejected by the donor. This would allow for generation of compatible cells, without the need for immune suppression. However, a recent study suggests that this may not be the case.
In the study (Zhao et al. Immunogenicity of induced pluripotent stem cells. Nature. 2011 May 13) investigators assessed the ability of embryonic stem cells and induced pluripotent stem cells (iPS) to stimulate immune responses using inbred, genetically identical mice. They found that embryonic stem cells (ESCs) derived from C57BL/6 (B6) mice can efficiently form teratomas (an aggressive type of tumor) in B6 mice (syngeneic) without any evident immune rejection. However, when allogeneic ESCs from 129/SvJ mice where transplanted into B6 mice, they were rapidly rejected by the B6 immune system. This by itself is interesting because transplantation of adult stem cells, mesenchymal stem cells, does not lead to rejection when transplanted between mouse strains.
When B6 mouse embryonic fibroblasts (MEFs) were reprogrammed into iPSCs by either retroviral approach (ViPSCs) or a novel episomal approach (EiPSCs) that causes no genomic integration and transplanted into B6 mice rejection was observed. Specifically, the retrovirally-generated iPS cells were more immunogenic than those generated by the novel episomal method. Rejection of both types of iPS cells was characterized by T cell infiltration.
Global gene expression analysis of teratomas formed by B6 ESCs and EiPSCs demonstrated that several iPS genes were expressed that contributed to immunogenicity. According to the authors “these findings indicate that, in contrast to derivatives of ESCs, abnormal gene expression in some cells differentiated from iPSCs can induce T-cell-dependent immune response in syngeneic recipients.”

Filed Under: News, Stem Cell Research Tagged With: , , , ,
February 17, 2011 by

World’s First Chemical Guided Missile Could Be the Answer to Wiping out Cancer

A research team at Deakin University has made a discovery that could have huge implications on the treatment and survival rates of cancer victims. The researchers, along with scientists in India and Australia have created the world’s first RNA aptamer, a chemical antibody that targets cancer stem cell marker epithelial cell adhesion molecule (EpCAM). This marker is overexpressed in cancer cells, thus allowing the RNA aptamer to bind directly to the cell before being internalized. The implications of this are that the aptamer has the potential ability to deliver drugs directly to the cancer stem cells and can also be used to develop a more effective cancer imaging system for early detection of the disease.

“Despite technological and medical advances, the survival rates for many cancers remain poor, due partly to the inability to detect cancer early and then provide targeted treatment,” said Professor Wei Duan, the Director of the Deakin Medical School’s Nanomedicine Program. “Current cancer treatments destroy the cells that form the bulk of the tumour, but are largely ineffective against the root of the cancer, the cancer stem cells. This suggests that in order to provide a cure for cancer we must accurately detect and eliminate the cancer stem cells.”

The aptamer is the first part of the ‘medical smart bomb’ the researchers have been developing. “What we have created is the ‘guided missile’ part of the ‘smart bomb’,” Professor Duan explained. “The aptamer acts like a guided missile, targeting the tumour and binding to the root of the cancer. “The aim now is to combine the aptamer with the ‘bomb’ (a microscopic fat particle) that can carry anti-cancer drugs or diagnostic imaging agents directly to the cancer stem cells, creating the ultimate medical smart bomb.”

“The cancer stem cell-targeting missile and the smart bomb could revolutionise the way cancer is diagnosed,” he explained. “The minute size of the aptamer means it could locate cancer cells in their very early stages. Attaching radioactive compounds to the aptamer could lead to the development of sensitive diagnostic scans for earlier detection, more accurate pinpointing of the location of cancer, better prediction of the chance of cure and improved monitoring of the response to treatment. More accurate identification of the type of cancer present would lead to more personalised treatment that is more successful and cost-effective. This could ultimately lead to better cancer survival rates and greatly improved quality of life for patients.”

Filed Under: News, Stem Cell Research Tagged With: , , , , , , ,
August 1, 2010 by

Pluripotent stem cell-derived natural killer cells for cancer therapy.

Knorr et al. Transl Res. 2010 Sep;156(3):147-154. Epub

Immune therapy of cancer is an exciting prospect given the possibility of treating cancer without the side effects associated with conventional treatments such as chemotherapy or radiotherapy. Additionally, the use of the immune system to target tumors offers the possibility of eradicating micrometastasis, which often cannot be treated by conventional means.

Early work in the immunotherapy of cancer involved taking out patient lymphocytes that were infiltrating the tumor, expanding them outside of the body, and subsequently re-injecting them with the hope that expanded numbers of tumor-specific killer cells would destroy the tumor. Unfortunately this approach was very expensive and did not yield positive results to justify the complexity and expense of the procedure. One possible reason for the failure of this approach is that the cells used where already “old” and “exhausted”. In other words, previous encounters of the T cells with cancer antigens seems to have programmed them so as to inhibit ability to mount a proper immune response.

The use of natural killer cells as an alternative to T cells was considered. These cells, called lymphokine activated killers (LAK) displayed specific ability to kill tumors and were more effective than T cells alone. Unfortunately this approach too also required substantial manipulation of the cells outside of the body and was not practical.

In a recent paper, the group of Knorr et al discussed how to use stem cells to solve the problem of generating anti-cancer immune cells out of the body. They discuss how they have successfully used embryonic stem cells to generate “universal donor” natural killer cells. This approach is highly promising since NK cells do not need to be matched with the recipient in order to mediate anti-cancer activity. Additionally, since the cells are generated “brand new” in the laboratory, the problem of “exhaustion” is no longer relevant. Unfortunately there are still several obstacles to overcome such as the potential of embryonic stem cells forming leukemias/tumors, and the possibility of host anti-graft responses.

The paper also describes the future possibility of using inducible pluripotent stem (iPS) cells as a method of generating autologous T cells with any given TCR specificity.

Filed Under: Cancer, News, Stem Cell Research Tagged With: , , ,
July 2, 2010 by

Eradication of brain tumor stem cells with an oncolytic adenovirus.

Jiang et al. Discov Med. 2010 Jul;10(50):24-8.

Philosophically, tumor cells have an advantage to humans in the “War on Cancer”. That is, the tumors have the ability to rapidly mutate, so that when drugs are given to fight the tumor, the tumor can “mutate around” the drug and become resistant. This occurs in several ways: a) the tumor starts expressing drug efflux pumps, such as the multi-drug resistance (MDR) protein that actively transports chemotherapeutics out of cancer cells; b) the tumor mutates the kinase or molecular target that the drug is inhibiting; and c) the tumor increases expression of other oncogenes that are not inhibited by the drug.

One interesting method of dealing with the problem of tumor mutation is to use agents against the tumor that are actively mutating. One approach has been the use of viruses that have a selective ability to infect tumors and to kill them. These are called “oncolytic” viruses. One of the most well-known oncolytic virus is the Reovirus, which only replicates in cells that express high concentrations of the oncogene RAS. This virus is in clinical trials by the Canadian company Oncolytics.

Delta-24-RGD is an oncolytic adenovirus that is capable of infecting glioma cells and preferentially inducing their death. It is being developed at the Brain Tumor Center, The University of Texas MD Anderson Cancer Center and is the subject of an ongoing Phase I clinical trial in the treatment of patients with therapy-resistant glioma.

One of the key issues surrounding any cancer therapeutic is whether the treatment is targeting tumor stem cells, or only the tumor progeny cells. This is very important because tumor stem cells are usually resistant to chemotherapy or other interventions that require cells to be metabolically-active and hyperproliferating. The majority of tumor cells are metabolically-active and fast multiplying, these cells are usually destroyed by conventional drug approaches, however, subsequent to their destruction the tumor stem cells exit quiescence and start making a new tumor. This has been one of the primary reasons for the poor success rate of cancer therapeutics that are currently under development.

In the current paper scientists found that the Delta-24-RGD virus is capable of infecting and causing death of glioma stem cells. This is a very important finding because it implies the possibility of attaining tumor cure by administration of such an oncolytic virus. Other advantages of the oncolytic virus approach is that the process of tumor cell death likely releases numerous antigens which cause activation of systemic immunity towards micrometastasis. Unfortunately one of the drawbacks of cancer therapy using oncolytic viruses is that the host develops an immune response to the virus which does not allow for long term continual administration. Patients interested in this treatment should contact Dr. Jiang at hjiang@mdanderson.org .

Filed Under: News, Stem Cell Research Tagged With: , , , , ,
May 17, 2010 by

Identification of Peptides Which Show Potential To Generate Cancer Stem Cell Specific Immune Responses

The use of the immune system to target cancer has been a therapeutic goal for over a century. The advantage of immunotherapy is the possibility of targeting cancer throughout the body in a non-toxic manner, thus allowing destruction of metastasis, and induction of immunological memory to protect from relapse. Unfortunately with exception of the recent FDA approval of Dendreon’s prostate cancer vaccine on April 29th, 2010 all other cancer vaccine Phase III clinical trials have failed. The company ImmunoCellular Therapeutics believes that one of the reasons for poor efficacy of previous trials revolves around the fact that they were targeting the wrong
type of tumor cell.

It is known that tumors are comprised of rapidly multiplying cells and "sleeping" cells. The cells that are dormant appear to act as stem cells in that they are capable of starting a brand new tumor when transplanted to mice. To date, cancer vaccines have been designed to kill rapidly multiplying tumor cells but not the dormant stem cells. ImmunoCellular Therapeutics has been collaborating with the Torrey Pines Institute to identify molecules found on tumor stem cells that can be used to generate vaccines. Today the company announced some progress in its quest.

The company claims to have identified several peptides which can generate T-cells capable of killing cells that express the protein CD133. This protein according to the press release, is found in high abundance on cancer stem cells. What is interesting is that this protein is also found on healthy, non-cancerous, stem cells such as circulating endothelial progenitor cells. Therefore it will be interesting to see if the vaccines that are being developed will have adverse effects. Theoretically the cancer stem cells should be more difficult to target with a vaccine as compared to non-malignant stem cells due to the fact that cancer stem cells generally secrete immune suppressive factors that protect them from the body’s attack.

Torrey Pines Institute and Immunocellular Therapeutics have expanded their existing research agreement to conduct additional studies to support an Investigational New Drug Application (IND) filing. This is an application to the FDA to ask for permission to perform clinical trials in humans.

Additionally, the press release stated that ImmunoCellular Therapeutics and the Torrey Pines Institute will work on research programs with other proteins found on cancer stem cells such as Numb and Notch.

Dr. Manish Singh, President and Chief Executive Officer of ImmunoCellular Therapeutics stated "We are excited by the discoveries to date that could prove
efficacious in treating cancer," he continued, "We look forward to expanding our relationship with the Torrey Pines Institute."

Filed Under: News, Stem Cell Research Tagged With: , , , ,
May 11, 2010 by

Natural Compound in Broccoli Slows Breast Cancer Stem Cells

The area of cancer stem cells is very hot. To give an
example, the pharmaceutical company GSK recently purchased the cancer stem cell
company Oncomed for more than a billion dollars, at a time when Oncomed’s cancer
stem cell-targeting drugs were not even tested in humans. This area is of great
interest because it suggests that the way to kill cancer is not to block the
fast multiplying cells, but that the cancer has a "root cause" that scientists
for decades have been ignoring.

Cancer stem cells are usually not destroyed by chemotherapy
or radiation therapy because they are slow dividing cells that possess numerous
proteins to protect themselves from toxicity such as multiple drug resistance
proteins. These proteins have the function of identifying chemotherapy inside
of the cancer cell and actively pumping it out. It is believed that the reason
why these proteins exist is to protect cells from damage to DNA. In cancer stem
cells these proteins appear to play a role in causing relapse after
chemotherapy.

Previously it was reported that the chicken feed antibiotic
salinomycin has the ability to selectively kill cancer stem cells (Gupta PB.
Identification of selective inhibitors of cancer stem cells by high-throughput
screening. Cell. 2009 Aug 21;138(4):645-59. Epub 2009 Aug 13), additionally,
using similar testing scenarios researchers found the anti-diabetic drug
metfomin inhibits breast cancer stem cells (Vazquez-Martin et al. The
anti-diabetic drug metformin suppresses self-renewal and proliferation of
trastuzumab-resistant tumor-initiating breast cancer stem cells. Breast Cancer
Res Treat. 2010 May 11). Given the recent nature of these findings, their
use in humans has not yet been reported in the scientific literature. In the
current study which will be discussed, another compound with similar anti-breast
cancer stem cell activity was identified.

A recent study (Li et al. Sulforaphane, a dietary
component of broccoli/broccoli sprouts, inhibits breast cancer stem cells. Clin
Cancer Res. 2010 May 1;16(9):2580-90) demonstrated that a natural chemical
compound found in broccoli and other cruciferous vegetables called sulforaphane
has the ability to slow down multiplication of breast cancer stem cells.
Essentially this means that sulforaphane can block the cells that cause cancer
from being activated and thus could be an effective cancer therapy if high
enough doses can be safely administered.

The scientists purified human breast cancer stem cells
using the Aldefluor assay made by the company Aldagen, which selects for cells
expressing the enzyme aldehyde dehydrogenase, an enzyme found in normal and
cancer stem cells. The stem cells were tested to see if they would form tumors
in mice lacking an immune system called nonobese diabetic/severe combined
immunodeficient mice.

It was found that sulforaphane administered at a
concentration of 1-5 micromol/L was sufficient to suppress multiplication of the
aldehyde dehydrogenase-positive stem cell population by 65% to 80% and reduce
the size and number of primary mammospheres by 8- to 125-fold and 45% to 75%,
respectively. Mammospheres are round tumor-like structures that grow in tissue
culture plates that represent a three-dimensional cancer.

Daily injection with 50 mg/kg sulforaphane for 2 weeks
reduced aldehyde dehydrogenase-positive cells by >50% in nonobese
diabetic/severe combined immunodeficient xenograft tumors. Since it appeared
that the administration of sulforaphane eliminated breast cancer stem cells in
the animal, the next step was to assess the ability of the growing tumors to
cause secondary tumors when transplanted into other animals. This indeed was
demonstrated to be the case. Ability to block transfer of tumors to secondary
recipients is associated with possibility of cure since it represents targeting
of the functional tumor stem cell compartment.

Mechanistically it appears that sulforaphane works on the
cancer stem cells through suppression of the Wnt/beta-catenin self-renewal
pathway, which is found in numerous tumor and non-malignant stem cells. This of
course poses the question of whether the high doses of sulforaphane that were
used in the study would have unwanted effects on healthy stem cells in the
body. The most relevant side effect of chemotherapeutic drugs is suppression of
blood cell production from the bone marrow stem cell. Indeed the scientists
found that there was no alteration of blood cell parameters in treated animals,
suggesting at least a partial degree of selectivity.

Sulforaphane is believed to exert at least some of its
anticancer biological effects through its ability to suppress histone
deacetylase (HDAC) activity. HDAC are proteins that are involved in "bundling"
of the DNA. If DNA from one cell was stretched out, it would be 7 meters from
end-to-end. The histone that are acetylated bind DNA in a loose manner and
allow for new genes from the DNA to be expressed that normally would not be
expressed. In the area of cancer, the treatment with HDAC inhibitors is
believed to cause brand new expression of tumor suppressor genes. These genes,
such as p53, instruct the tumor cell to undergo cellular suicide, called
apoptosis.

The controversial "Burzynski Therapy" involving
antineoplastons, which are naturally occurring compounds is believed to function
through induction of histone acetylation and induction of tumor suppressor genes
(Burzynski, The present state of antineoplaston research, Integr Cancer Ther.
2004 Mar;3(1):47-58). It would be interesting to examine whether some of the
reported positive effects of this non-toxic cancer therapy is mediated by
suppression of tumor stem cell activity.

A recent paper (Ho et al. Dietary sulforaphane, a
histone deacetylase inhibitor for cancer prevention. J Nutr. 2009
Dec;139(12):2393-6. Epub 2009 Oct 7) demonstrated that sulforaphane inhibits
HDAC activity in human colorectal and prostate cancer cells. Based on the
similarity of sulforaphane metabolites and other phytochemicals to known HDAC
inhibitors, it was previously demonstrated that sulforaphane acted as an HDAC
inhibitor in the prostate, causing enhanced histone acetylation, derepression of
P21 and Bax, and induction of cell cycle arrest/apoptosis, leading to cancer
prevention. The possible ability of sulforaphane to target aberrant acetylation
patterns, in addition to effects on phase 2 enzymes, may make it an effective
agent in suppressing cancer cells in a non-toxic manner.

This study also poses the question if HDAC inhibitors in
general can alter tumor stem cell ability. It is known that valproic acid, the
HDAC inhibitor actually increases ability of stem cells to self renew while
being selectively toxic to leukemic cells

http://www.youtube.com/watch?v=3Hc4LCUOSiA.

An interesting note regarding cancer stem cells is that many approaches
traditionally supported by practitioners of alternative medicine may actually be
targeting these cells. In alternative medicine the main theme is providing the
body with nutrients to "heal itself". Practitioners of alternative medicine
have had some degree of success treating cancer in a "nontoxic" manner using
dramatic dietary modifications, nutrient therapy, and administration of agents
that induce differentiation. It may be possible that these interventions act to
reduce the localized inflammation in the tumor mass. This inflammation is
believed by some to be what stimulates the cancer stem cell to enter cell
cycle. Accordingly, it is interesting to see that components of broccoli
inhibit cancer stem cells. It will be interesting to examine other nutrients
for ability to target cancer stem cells.

Filed Under: Cancer, News, Stem Cell Research Tagged With: , , , ,
February 26, 2010 by

Fat May Serve a Purpose in Stem Cell Research

Scientist Dr. Joseph Wu at the Stanford University School
of Medicine has recently published a new and improved method to generate stem
cells "artificially".  For almost a decade there has been substantial
controversy regarding the use of embryonic stem cells, with the debate becoming
socially and politically focused as opposed to based on science: one camp
believing that embryonic stem cell research must be supported at all costs, the
other camp believing that adult stem cells can do anything that embryonic stem
cells can do, so there should be no research performed in this area.  This
debate became somewhat irrelevant when the Japanese group of Yamanaka discovered
a method of "dedifferentiating" adult cells into cells that appear at a
molecular and functional level similar to embryonic stem cells.  These
"artificial" stem cells, called inducible pluripotent stem cells (iPS) have
several unique properties:  They don’t need to be extracted from embryos; they
can be made from the same patient that they will be used on; and the methods of
manufacturing can be relatively standardized. 

To date these cells have been demonstrated to be capable of
generating not only every tissue in the body tested, but they also can improve
disease conditions in animal models ranging from heart attacks, to liver
failure, to bone marrow reconstitution.  Unfortunately the biggest problem with
iPS cells is that they are difficult to generate.  In order to understand this,
it is important to first mention how the cells are made.  Adult cells have the
same DNA blueprint as embryonic stem cells.  However in adult cells certain
portions of the DNA are not used to make proteins.  So in liver cells the DNA
that encodes for proteins found in the skin is "silenced" or "blocked" from
making proteins by various chemical modifications that occur as a cell is
maturing.  Embryonic stem cells are considered "blank slate" cells because the
DNA is capable of expressing every protein found in the body.  In order to make
an adult stem cell "younger" so as to resemble an embryonic stem cell, it is
necessary to somehow reprogram the DNA in order to allow it to express every
gene.  So how would one go about doing this? There is one biological condition
in which adult cells take the phenotype of younger cells.  This is in cancer. 
This is the reason why some types of cancer start expressing proteins that other
cells normally produce.  For example certain liver cancers can produce insulin,
even though liver cells do not produce insulin.  The concept that certain cancer
genes can evoke a "rejuvenation" of adult cells was used by Yamanaka as a
starting point.  His group found that if you insert the oncogene c-myc, together
with the stem cell genes Nanog, Oct-4, and SOX-2 skin cells will start to look
like embryonic stem cells.  If these cells are placed on top of feeder cells
then they can be expanded and used as a substitute for embryonic stem cells.

The current problem with wide-scale use of this approach is
that insertion of the various genes into the cells requires the use of viruses
that literally infect the cells with the foreign genes.  Not only can the
viruses cause cancer, but also the genes administered can cause cancer because
they are oncogenes.  The other hurdle is that generation of iPS cells is a very
inefficient process.  It takes approximately 2-3 months to generate stable
cells, and these cells are usually generated from approximately 1 out of
100-300,000 starting cells.  We previously discussed advances that allowed for
uses of non-hazardous means of inserting genes into cells to make iPS

https://www.celllmedicine.com/thomson-safer-ips.asp , in this current article
another approach was described to increase efficacy.

Scientists used as starting population not skin cells,
which are considered substantially differentiated, but instead used fat derived
stem cells.  This type of stem cell is very much a mesenchymal stem cell

http://www.youtube.com/watch?v=qJN2RyBj78I and possesses ability to
transform into different tissues already.  Thus by starting with a cell that is
already more "immature", scientists have been able to increase the rate of iPS
generation, as well as, alleviate the need for the oncogene c-myc.

Other approaches being investigated on increasing
generation of iPS cells include use of chemicals that affect the DNA structure
such as valproic acid.  This is interesting because simple administration of
valproic acid on bone marrow stem cells has been demonstrated to increase their
"stemness"

http://www.youtube.com/watch?v=3Hc4LCUOSiA .

Although we are still far from the day when
individual-specific stem cells will be available for widespread use, we are
getting closer to this dream at a very fast pace.

Filed Under: Adult Stem Cells, Embryonic Stem Cells, News, Stem Cell Research Tagged With: , , , , ,