New study shows evidence of stem cells’ pivotal role in cancer

WASHINGTON - A Stanford University study has suggested that leukemia patients whose cancers express higher levels of genes associated with cancer stem cells have a significantly poorer prognosis than patients with lower levels of the genes.

The finding is among the first to show that the cancer stem cell hypothesis - which posits that some cancers spring from and are replenished by a small, hardy population of self-renewing cells - can be used to predict outcomes in a large group of patients and one day to tailor treatments in the clinic.

“If we’re not able to design therapies to target this self-renewing population of chemotherapy-resistant cells, the patients will continue to have a tendency to relapse,” said Ash Alizadeh, co-senior author of the study.

In the study, researchers were interested in learning whether leukemia stem cells play a similarly important role in acute myeloid leukemia, which is one of the most aggressive blood cancers in adults.

The team used two cell surface markers formerly shown to identify leukemia stem cells to isolate these cells from tumor samples from seven patients. They then compared the overall gene expression patterns of the stem cells to other cells in the tumors and identified a total of 52 genes whose expression varies between the tumor stem cells and non-stem cells.

Interestingly, the gene expression pattern is similar to that found on normal blood stem cells, which give rise to blood cells and the immune system. This similarity implies that the cancer stem cells not only can self-renew, but also that they, like normal stem cells, don’t divide unless they’re needed. Infrequent division may be one way the cancer stem cells escape many conventional treatments that target rapidly dividing cells.

“It’s as if these cells are lurking in the background, waiting to pounce after chemotherapy has wiped out most of the other cells,” said Alizadeh.

When the researchers compared the levels of expression of these new leukemia stem-cell-associated genes among tumor samples from four groups with a total of more than 1,000 people with acute myeloid leukemia, they found a strong correlation between high levels of expression and a poor outcome for the patients.

The findings were published in the Journal of the American Medical Association. (ANI)