The study also shows that three of these miRNAs inhibit the action of two genes important for cancer development, helping to explain how the drug works.
The drug is called all-trans-retinoic acid (ATRA) and it is considered the gold standard for treating the disease.
The study showed that ATRA raises the levels of three particular miRNAs in leukemia cells and that this rise coincides with a fall in activity of two important cancer-causing genes. The three are identified as miRNA-15b, miRNA-16-1 and let-7.
Two of these, miRNA-15b and miRNA-16-1, reduce the activity of the Bcl-2 gene, which is over-active in many kinds of cancer. The protein produced by this gene blocks the normal process of cell death and helps keep cancer cells alive long after they should have died.
The remaining miRNA molecule, let-7, lowered the activity of the Ras oncogene, an important cancer-causing gene. (Oncogenes are normal genes that when mutated lead to cancer.)
Researchers at the Ohio State University Comprehensive Cancer Center led the study, which was published in a recent issue of the journal Oncogene.
"The findings are important because they tell us that some miRNAs switch off genes that promote cancer," says first author Ramiro Garzon, a hematologist and oncologist at Ohio State's James Cancer Hospital and Solove Research Institute.
Acute promyelocytic leukemia occurs when cells that give rise to a form of white blood cell become stuck at an immature stage. The immature cells accumulate until they crowd out healthy white cells in the blood and bone marrow.
"Our findings suggest that these three miRNAs help re-program the malignant cells to a more normal state," Garzon says, "and that they are also impo
Source:Ohio State University