Peptide-2 from Mouse Myostatin Precursor Protein Alleviates Muscle Wasting in Cancer-associated Cachexia

Cancer cachexia, characterized by continuous muscle wasting, is a key determinant of cancer-related death; however, there are few medical treatments to combat it. Myostatin (MSTN)/growth differentiation factor 8 (GDF-8), which is a member of the transforming growth factor-β family, is secreted in an inactivated form noncovalently bound to the prodomain, negatively regulating the skeletal muscle mass. Therefore, inhibition of MSTN signaling is expected to serve as a therapeutic target for intractable muscle wasting diseases. Here, we evaluated the inhibitory effect of peptide-2, an inhibitory core of mouse MSTN prodomain, on MSTN signaling. Peptide-2 selectively suppressed the MSTN signal, although it had no effect on the activin signal. In contrast, peptide-2 slightly inhibited the GDF-11 signaling pathway, which is strongly related to the MSTN signaling pathway. Furthermore, we found that the i.m. injection of peptide-2 to tumor-implanted C57BL/6 mice alleviated muscle wasting in cancer cachexia. Although peptide-2 was unable to improve the loss of heart weight and fat mass when cancer cachexia model mice were injected with it, peptide-2 increased the gastrocnemius muscle weight and muscle cross-sectional area resulted in the enhanced grip strength in cancer cachexia mice. Consequently, the model mice treated with peptide-2 could survive longer than those that did not undergo this treatment. Our results suggest that peptide-2 might be a novel therapeutic candidate to suppress muscle wasting in cancer cachexia.