Dr. Anil Sood with the University of Texas MD Anderson Cancer Center here in Houston was the senior author of the study. Researchers compared ovarian cancer patients with low levels of Dicer and Drosha with those who were found to have higher levels of both proteins. The results were startling. The median length of survival for patients with low levels of both proteins was 2.66 years, compared to 11 years for patients with higher levels of both proteins.
"These enzymes typically are present in normal cells and their role is to process RNA interference in a way that genes downstream of these enzymes can be regulated. To us it was a surprise that such a sizable proportion of cancers had low or absent levels of these enzymes and that this finding was consistent, not in just one cancer type but in other cancers as well."
The initial study included 111 patients with invasive ovarian cancer tumors and a second analysis that studied 132 patients. Additional studies of lung and breast cancer patients showed similar results.
"The reason we started to study the role of these was that as we start to figure out how genes are regulated in cancer cells, these two enzymes play a critical role in that process. A substantial proportion of cancers, our focus was on ovarian cancer, tend to have low levels, or lack one or both of these enzymes."
The study is published in the latest online edition of the New England Journal of Medicine. Sood says the research could provide a roadmap on how to use proteins to disrupt cancer cells.
"It provides us with direction in terms of understanding how genes are regulated, but it also guides us in terms of where to focus with regard to developing therapies."
View the research at http://content.nejm.org/cgi/content/short/359/25/2641.