Hormonally Regulated Myogenic miR-486 Influences Sex-specific Differences in Cancer-induced Skeletal Muscle Defects.

Cancer-induced skeletal muscle defects show sex-specific differences in severity with men performing poorly compared to women. Hormones and sex chromosomal differences are suggested to mediate these differences, but the functional skeletal muscle markers to document these differences are unknown. We show that the myogenic microRNA miR-486 is a marker of sex-specific differences in cancer-induced skeletal muscle defects. Cancer-induced loss of circulating miR-486 was more severe in men with bladder, lung, and pancreatic cancers compared to women with the same cancer types. In a syngeneic model of pancreatic cancer, circulating and skeletal muscle loss of miR-486 was more severe in male mice compared to female mice. Estradiol (E2) and the clinically used selective estrogen receptor modulator toremifene increased miR-486 in undifferentiated and differentiated myoblast cell line C2C12 and E2-inducible expression correlated with direct binding of estrogen receptor alpha (ERα) to the regulatory region of the miR-486 gene. E2 and toremifene reduced the actions of cytokines such as myostatin, transforming growth factor β, and tumor necrosis factor α, which mediate cancer-induced skeletal muscle wasting. E2- and toremifene-treated C2C12 myoblast/myotube cells contained elevated levels of active protein kinase B (AKT) with a corresponding decrease in the levels of its negative regulator PTEN, which is a target of miR-486. We propose an ERα:E2-miR-486-AKT signaling axis, which reduces the deleterious effects of cancer-induced cytokines/chemokines on skeletal muscle mass and/or function.