Researchers trace the source of recurring blood cancers to a few slowly dividing cancer stem cells.

By Cristina Luiggi | May 31, 2012

Brain cancer stem cellsWellcome Images

Why cancer comes back in some patients after chemotherapy has beaten it into remission has been a matter of debate for oncologists. In a new study published in Blood this week, researchers at The Weizmann Institute of Science in Rehovot, Israel, found that in certain blood cancers, slowly-dividing cancer stem cells that are impervious to the actions of chemotherapywhich commonly target fast-dividing cellsare the source for future recurring cancers.

Led by computational biologist Ehud Shapiro, the researchers reconstructed lineage trees of cells sampled from patients with newly diagnosed leukemia and from patients in which leukemia had returned. They found that in some cases, the source of the recurring cancer cells were not rapidly dividing cancer cells that had dodged chemotherapy, but the slowly-dividing stem cells at the root of the tree.

We know that in many cases, chemotherapy alone is not able to cure leukemia, Shapiro said in a press release. Our results suggest that to completely eliminate it, we must look for a treatment that will not only eliminate the rapidly dividing cells, but also target the cancer stem cells that are resistant to conventional treatment.

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Why Some Cancers Come Back

Public release date: 31-May-2012 [ | E-mail | Share ]

Contact: Deborah Wormser deborah.wormser@utsouthwestern.edu 214-648-3404 UT Southwestern Medical Center

DALLAS May 31, 2012 An immune-system receptor plays an unexpected but crucially important role in keeping stem cells from differentiating and in helping blood cancer cells grow, researchers at UT Southwestern Medical Center report today in the journal Nature.

"Cancer cells grow rapidly in part because they fail to differentiate into mature cells. Drugs that induce differentiation can be used to treat cancers," said Dr. Chengcheng "Alec" Zhang, assistant professor in UT Southwestern's departments of physiology and developmental biology. "Our research identified a protein receptor on cancer cells that induces differentiation, and knowing the identity of this protein should facilitate the development of new drugs to treat cancers."

The family of proteins investigated in the study could help open a new field of biology integrating immunology with stem cell and cancer research, he added.

"The receptor we identified turned out to be a protein called a classical immune inhibitory receptor, which is known to maintain stemness of normal adult stem cells and to be important in the development of leukemia," he said.

Stemness refers to the blood stem cells' potential to develop into a range of different kinds of cells as needed, for instance to replenish red blood cells lost to bleeding or to produce more white blood cells to fight off infection. Once stem cells differentiate into adult cells, they cannot go back to being stem cells. Current thinking is that the body has a finite number of stem cells and it is best to avoid depleting them, Dr. Zhang explained.

Prior to this study, no high-affinity receptors had been identified for the family of seven proteins called the human angiopoetic-like proteins. These seven proteins are known to be involved in inflammation, supporting the activity of stem cells, breaking down fats in the blood, and growing new blood vessels to nourish tumors. Because the receptor to which these proteins bind had not been identified, the angiopoetic-like proteins were referred to as "orphans," he said.

The researchers found that the human immune-inhibitory receptor LILRB2 and a corresponding receptor on the surface of mouse cells bind to several of the angiopoetic-like proteins. Further studies, Dr. Zhang said, showed that two of the seven family members bind particularly well to the LILRB2 receptor and that binding exerts an inhibitory effect on the cell, similar to a car's brakes.

In the case of stem cells, inhibition keeps them in their stem state. They retain their potential to mature into all kinds of blood cells as needed but they don't use up their energy differentiating into mature cells. That inhibition helps stem cells maintain their potential to create new stem cells because in addition to differentiation, self-renewal is the cells' other major activity, Dr. Zhang said. He stressed that the inhibition doesn't cause them to create new stem cells but does preserve their potential to do so.

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Researchers identify mechanism that maintains stem cells readiness

Newswise DALLAS May 31, 2012 An immune-system receptor plays an unexpected but crucially important role in keeping stem cells from differentiating and in helping blood cancer cells grow, researchers at UT Southwestern Medical Center report today in the journal Nature.

Cancer cells grow rapidly in part because they fail to differentiate into mature cells. Drugs that induce differentiation can be used to treat cancers, said Dr. Chengcheng Alec Zhang, assistant professor in UT Southwesterns departments of physiology and developmental biology. Our research identified a protein receptor on cancer cells that inhibits differentiation, and knowing the identity of this protein should facilitate the development of new drugs to treat cancers.

The family of proteins investigated in the study could help open a new field of biology integrating immunology with stem cell and cancer research, he added.

The receptor we identified turned out to be a protein called a classical immune inhibitory receptor, which is known to maintain stemness of normal adult stem cells and to be important in the development of leukemia, he said.

Stemness refers to the blood stem cells potential to develop into a range of different kinds of cells as needed, for instance to replenish red blood cells lost to bleeding or to produce more white blood cells to fight off infection. Once stem cells differentiate into adult cells, they cannot go back to being stem cells. Current thinking is that the body has a finite number of stem cells and it is best to avoid depleting them, Dr. Zhang explained.

Prior to this study, no high-affinity receptors had been identified for the family of seven proteins called the human angiopoetic-like proteins. These seven proteins are known to be involved in inflammation, supporting the activity of stem cells, breaking down fats in the blood, and growing new blood vessels to nourish tumors. Because the receptor to which these proteins bind had not been identified, the angiopoetic-like proteins were referred to as orphans, he said.

The researchers found that the human immune-inhibitory receptor LILRB2 and a corresponding receptor on the surface of mouse cells bind to several of the angiopoetic-like proteins. Further studies, Dr. Zhang said, showed that two of the seven family members bind particularly well to the LILRB2 receptor and that binding exerts an inhibitory effect on the cell, similar to a cars brakes.

In the case of stem cells, inhibition keeps them in their stem state. They retain their potential to mature into all kinds of blood cells as needed but they dont use up their energy differentiating into mature cells. That inhibition helps stem cells maintain their potential to create new stem cells because in addition to differentiation, self-renewal is the cells other major activity, Dr. Zhang said. He stressed that the inhibition doesnt cause them to create new stem cells but does preserve their potential to do so.

In future research, the scientists hope to find subtle differences between stem cells and leukemia cells that will identify treatments to block the receptors action only in leukemia.

Other UT Southwestern researchers involved in the study from the departments of physiology and developmental biology include postdoctoral researchers Dr. ChangHao Cui, Dr. Xiaoli Chen, Dr. Chaozheng Zhang, Dr. HoangDinh Huynh, and Dr. Xunlei Kang; senior research associates Robert Silvany and Jiyuan Li; and graduate student Xuan Wan. Researchers from the department of immunology include former technician Alberto Puig Cant and Dr. E. Sally Ward, professor of immunology.

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Researchers Identify Mechanism That Maintains Stem Cells Readiness, Helps Leukemia Cells Growth

GRAND RAPIDS, MI -- A stem cell treatment investigated for Huntingtons disease holds out hope that scientists will someday be able to reverse damage caused by the degenerative brain disorder.

The technique, which uses reprogrammed skin cells from a Huntingtons patient, successfully restored motor functions in rats, said Dr. Patrik Brundin, a Van Andel Institute researcher who was involved in the study.

Its an interesting step, one weve been hoping for, he said. Its exciting.

The technique also will be tested in treatments for Parkinsons disease, said Brundin, who came to VAI from Sweden in October to lead the institutes Parkinsons research.

Scientists from Sweden, South Korea and the U.S. collaborated on the study, which was published online Monday in the journal Stem Cells.

Brundin said researchers took stem cells derived from the skin of a patient with Huntingtons disease and converted them to brain cells or nerve cells in culture dishes in the lab. The cells were transplanted into the brains of rats that had an experimental form of Huntingtons, and the rats motor functions improved.

The unique features of the (stem cell approach) means that the transplanted cells will be genetically identical to the patient, Jihwan Song, an associate professor at CHA University in Seoul and co-author of the study, said in a statement released by VAI. Therefore, no medications that dampen the immune system to prevent graft rejection will be needed.

Brundin estimated the research might lead to treatments for humans in five to 10 years, although he acknowledged a timeframe is difficult to predict. Researchers are eager to find a new treatment for Huntingtons because there is nothing really powerful to offer currently, he said.

Huntingtons is a genetic disorder affecting one in every 10,000 Americans that slowly diminishes a persons ability to walk, talk and reason. A child of a parent who has Huntingtons has a 50 percent chance of inheriting the gene that causes it.

Medications can relieve some symptoms in some cases, but there are no treatments available that can slow the disease, according to the Huntingtons Disease Society of America.

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First treatment for Huntington's disease shows promise in rats, Van Andel Institute scientist says

Be cautious with stem cells

EDITOR

The secret of restoring health lies in replacing decrepit cells ravaged by disease with stem cells. This advance in stem cell research follows and is closely linked to the simultaneous announcement by former US President Bill Clinton and British Prime Minister John Major in 2000 that scientists had unravelled the human genome by more than 90 percent. The breakthrough of the Human Genome Project was hailed in superlative terms as advancement in the treatment of cancer and hereditary diseases. Clinton described it as the first survey of the entire human genome and "the most wondrous map ever produced by humankind". A couple of years earlier, physician-geneticist Francis Collins, that leading light noted for his discoveries of disease genes, had described the advance in breaking the human genetic code as something that would be judged by history as "more significant than even splitting the atom or going to the moon".

However, the same sage had warned: "We have a small lantern in the form of a gene, but the lantern doesn't penetrate more than a couple of hundred feet. We don't know whether we're going to encounter chasms, rock walls or mountain ranges along the way." It is this warning that we want to draw attention to. In doing so, we recall that Dolly, the cloned sheep that was eventually euthanised after being diagnosed with progressive lung disease in 2003, was the culmination of embryonic stem cell research that pitted moral scruples against science in yet another of their cyclical rancorous confrontations. In the end, governments ordered a stop to what they feared could degenerate into man playing God. It is important to note that the theatre of this apparent antipathy between metaphysics and science was the citadel of the latter in Western Europe and North America, and not some windswept desert country on a plateau in southern Africa. We feel compelled to issue this warning because countries defined by widespread ignorance have often provided the ideal environment for rogue scientists to conduct their nefarious experiments in pursuit of wicked goals. We say this because while the Ministry of Agriculture (MoA) has perhaps the highest concentration of educated Batswana, they simply looked the other way as controversy around genetically modified foods raged everywhere else in the world.

Our country being a net exporter of food, it was incumbent upon MoA to at least mount a deliberate awareness campaign and insist on adequate labelling of food. But where food production remains an elusive goal, it must be too much to expect MoA to understand that the end aim of food and pharmaceutical multinationals is depletion of botanical resources in the so-called Third Word and dependence on the West. Hence we receive news that enabling legislation for a stem cell facility is to be passed in July with a sense of trepidation.

Today's thought"The world is a dangerous place, not because of those who do evil, but because of those who look on and do nothing."

- Albert Einstein

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Be cautious with stem cells