Enzymes Predict Ovarian Cancer Survival
CancerWise - March 2009
Two enzymes that are a type of protein and important for the regulation of genes may play a part in the outcomes of patients with ovarian or other types of cancer.
A recent study showed that women with ovarian cancer who had low levels of these enzymes, named Dicer and Drosha, had shorter survival times. The enzymes also were shown to affect lung and breast cancers.
A research team led by scientists at M. D. Anderson published its findings in the Dec. 18, 2008, issue of the New England Journal of Medicine.
Significance of study
Dicer and Drosha are important parts of the cells’ gene-silencing machinery.
“Drosha functions within the cell nucleus,” says Anil Sood, M.D., professor in the departments of Gynecologic Oncology and Cancer Biology and co-director of the Blanton-Davis Ovarian Cancer Research Program at M. D. Anderson. “It processes longer fragments of ribonucleic acid (RNA), which are then transported into the cytoplasm (a part of a cell). There, Dicer processes the fragments into even shorter fragments, which go on to silence or shut off specific genes or pathways.”
Researchers measured the levels of Dicer and Drosha in invasive epithelial ovarian cancer cells from 111 patients. Then, they compared those levels with the patients’ survival times.
They validated the results by looking at levels of the enzymes in ovarian, breast and lung cancer.
Women with high levels of Dicer and Drosha had median survival times of 11 years. On the other hand, women with low or absent levels of the enzymes survived about 2½ years.
About half the ovarian cancers had low levels of Dicer and Drosha.
When researchers looked at patients with lung and breast cancer, they confirmed the findings in ovarian cancer. Patients with lower levels of Dicer and Drosha had dramatically shorter survival times.
Sood says the findings have many potential applications. The information may be useful to understanding how cancer affects people differently, and it eventually may guide treatment.
“This information appears to be a promising prognostic factor in determining which patients with certain types of cancer might fare better or worse,” Sood says. “Could there be certain cancer treatments that are tailored to people with low Drosha and Dicer levels? This is just one of the many questions remaining to be answered.”
As therapies that alter RNA get closer to reality, the findings of this study may help researchers determine which type of RNA fragments to use for treatment. This, in turn, will guide further development of new therapies, Sood says.
“We’re trying to understand further why this kind of machinery is altered in cancer cells,” he says. “Secondly, as we move forward investigating this process, we want to understand the pathways that are altered in cancer cells and the implications of these alterations both in patients’ clinical outcomes and the behavior of cancers.”
— Adapted by Dawn Dorsey from an M. D. Anderson news release