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Enzyme accelerates malignant stem cell cloning in chronic myeloid leukemia

Some cancer stem cells avoid destruction and eventually regenerate themselves.

Chronic myeloid leukemia blood cells

An international team, headed by researchers at the UC San Diego School of Medicine, has identified a key enzyme in the reprogramming process that promotes malignant stem cell cloning and the growth of chronic myeloid leukemia (CML), a cancer of the blood and marrow that experts say is increasing in prevalence.

The findings are published in the Dec. 24 online early edition of the Proceedings of the National Academy of Sciences (PNAS).

Despite the emergence of new therapies, such as tyrosine kinase inhibitors, CML and other leukemias remain problematic because some cancer stem cells avoid destruction and eventually regenerate themselves, a stem cell process known as self-renewal that can result in a return and spread (metastasis) of the disease.

In the PNAS paper, principal investigator Catriona H. M. Jamieson, M.D., Ph.D., associate professor of medicine at UC San Diego, with colleagues in the United States, Canada and Italy, report that inflammation – long associated with the development of cancer – boosts activity of  an enzyme called adenosine deaminase or ADAR1.

Expressed during embryogenesis to help blood cell development, ADAR1 subsequently turns off and is triggered by viral infections where it protects normal hematopoietic stem cells from attack. In leukemia stem cells, however, overexpression of ADAR1 enhances the missplicing of RNA, which leads to greater self-renewal and therapeutic resistance of malignant stem cells.

The findings build upon previous studies by Jamieson and others that elucidate the effects of RNA missplicing and instability. “People normally think about DNA instability in cancer, but in this case, it’s how the RNA is edited by enzymes that really matters in terms of cancer stem cell generation and resistance to conventional therapy.”

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