High levels of the microRNA miR-21 in the environment around a tumor, but not in the cancer cells, are associated with worse outcomes for patients with triple-negative breast cancer, according to a study in The American Journal of Pathology.
miRNAs are short RNAs that modulate gene expression. In previous research, miR-21 was associated with poorer disease outcomes in cancers of the colon, pancreas, and breast. The goal of this study was to explore in greater detail the influence of miR-21 on TNBC outcomes, looking both at the amount and the location of miR-21 expression. The authors suspected that changes in the tumor's surrounding microenvironment could be even more important than changes within the cancer cells.
miR-21 expression was found in 42.8 percent of the 901 cases tested. Patients with TNBC with high levels of miR-21 in the tumor microenvironment faced outcomes three times worse than those with lower expressions or at other locations.
Researchers say this emphasizes the need for genetic testing of TNBC tumors and could lead to targeted treatment for those with miR-21.