Tumors' Chemical Signal

Leukemia cells use powerful chemical signals to lure healthy blood-forming stem cells into their cancerous lairs, where they lose their power to make healthy blood cells, U.S. researchers said.

But by jamming these signals in mice, the team was able to protect the stem cells, called hematopoietic progenitor cells. If it works in humans, this process could help preserve healthy blood cells in people with leukemia.

Leukemia cells and some solid tumors create specific niches in the bone marrow where they multiply and spread. Healthy blood-making cells also congregate in special bone marrow niches, where they divide and make cells needed to fight infection, control blood clotting and carry oxygen to the body.

Cells that were previously in happy normal homes were actually so attracted by the malignant niches; they were migrating into these tumor cell niches where they were compromised. Their number declines over time and once they were in the malignant niche they couldn't leave it and were stuck there. The cancer overproduces a normally expressed molecule called a stem cell factor, which entices normal stem cells into the cancer niche. When the team blocked the release of this chemical signal with neutralizing antibodies, the blood-making cells went about their normal business.

In anther unrelated French-led international study found that acute myeloid leukemia patients treated with Vidaza (azacitidine) have significantly increased overall survival. Acute myeloid leukemia is a cancer in which abnormal cells accumulate in bone marrow and interfere with normal blood cell production. Patients with AML typically have a poor prognosis and do not respond well to conventional chemotherapy. Noting approximately 30 percent of patients diagnosed with myelodysplastic syndrome, formerly known as "preleukemia," will progress to AML.

The results from an international phase III trial that was the first to show an increased overall survival for higher-risk MDS patients. The study showed 50 percent of the AML patients who were treated with Vidaza survived at least two years, compared with only 16 percent of patients treated with conventional regimens.