Involvement of CHOP in activin A­induced myeloma NS­1 cell apoptosis.

Activin A, a multifunctional cytokine, is a member of transforming growth factor­ß (TGF­ß) superfamily. It is associated with a variety of pathophysiological processes, including inflammation, fibrosis, and tumorigenesis. Chronic or prolonged endoplasmic reticulum (ER) stress can lead to cells apoptosis. However, whether ER stress­related proteins, such as CHOP, GADD34 are involved in activin A­induced myeloma cell apoptosis remains unknown. In the present study, it was revealed that activin A inhibited the proliferation of myeloma cell line NS­1 cells and induced NS­1 cell apoptosis. Activin A upregulated the expression of CHOP, GADD34, caspase­3, and caspase­12. Moreover, both Smad3 and p­Smad3 levels were increased with treatment of activin A. Further studies revealed that the overexpression of activin signaling protein Smad3 in NS­1 cells increased the levels of CHOP, caspase­3, and p­Smad3. These data indicated that the CHOP protein of the ER stress pathway may be involved in activin A­induced NS­1 cell apoptosis, and also indicated the potential therapy of activin A­induced apoptosis via CHOP signaling for multiple myeloma.