According to new research women with ovarian cancer who had low levels of either of two tumor proteins had lower chances of survival as compared to women who had higher levels of one of the two enzymes. In the case of both the enzyme levels being low the prognosis was even grimmer.

Study senior author Dr. Anil K. Sood, a professor in gynecologic oncology and cancer biology at the University of Texas M. D. Anderson Cancer Center in Houston said, "If there were low levels [of both proteins], those patients tended to survive, on average, 2.66 years compared to those with high levels of both proteins, who survived around
11 years, so there's quite a bit of difference."

The proteins, known as Dicer and Drosha, are key players in RNA interference (RNAi), a naturally occurring system that turns genes on and off. The study published in the Dec. 18 issue of the New England Journal of Medicine is the largest to link RNAi with cancer survival rates.

The researchers also found that high Dicer levels are linked to survival in breast and lung cancer. These two proteins are responsible for cutting and shaping tiny snippets of genetic material known as microRNAs, or miRNA.

"In the past, people used to think that miRNA might actually promote tumor growth, but there is some emerging thought that some of the miRNAs might keep tumors from growing and actually function as a tumor suppressor," said Sood,

Dr. Robert A. Burger, co-director of the Ovarian Cancer Research Program at Fox Chase Cancer Center in Philadelphia said, "There's a spectrum of survival among patients with advanced ovarian cancer, and researchers are trying to see if there are actual genetic factors within these tumors identified that are independent from known factors such as age, stage at diagnosis, microscopic appearance of the tumor, that have an influence on the aggressiveness of the tumor. This article represents an example of very, very new genetic information on ovarian cancers that in the distant future could lead to new types of treatment strategies."

In the study Sood and colleagues analyzed tissue from 111 women with advanced epithelial ovarian cancer, specifically looking for Dicer and Drosha. They found 60 % of the cancers had low levels of Dicer, 51 % had low levels of Drosha, and 39 % had low levels of each. Low levels of either or both genes was associated with poorer survival. Low Dicer levels also strongly predicted worse survival in lung cancer and breast cancer patients while Drosha had less of an association in these cancers. So-called "RNA interference therapies" are coming closer to realization, Sood noted.

"This really helps us to understand more about the fine-tuning mechanisms that are going awry in cancer cells versus normal cells," said Robert J. Morgan Jr., M. D., co-director of the gynecological malignancy program at the City of Hope Cancer Center, in Duarte, California. "While this won't influence patients right now, it will influence scientists developing these lifesaving drugs."