Objective  To observe and identify the inhibitory effect of oncostatin M (OSM) combined with dacarbazine (DTIC) on mouse melanoma cells B16 in vitro and in vivo.

  Methods  The inhibitory effect of OSM combined with DTIC on the proliferation and apoptosis of B16 melanoma cell line B16 were determined through MTT assay and flow cytometry, respectively. The change in nucleus morphology of B16 cells was observed under a fluorescence microscope by Hoechst staining method. The effects of single agents OSM and DTIC, as well as OSM–DTIC joint treatments, on tumor in mice in vivo were observed by inoculating B16 cells into C57 BL of six mice.

  Results  The OSM, DTIC, and combined OSM–DTIC treatments inhibited the proliferation of B16 cells by (11.2±2.3)%, (25.3±4.6)%, and (32.5±3.8)%, respectively (P < 0.05). Apoptosis of B16 occurred at (1.32±0.42)%, (10.64±2.13)%, and (15.86±2.76)%, respectively (P < 0.05). Cell morphology showed a significant increase in nuclear fragmentation, as proven by OSM-DTIC combined treatment. In the in vivo experiment, DTIC caused an apparent inhibition on the growth of mouse melanoma compared with the control group, and the joint treatment showed that the addition of OSM enhanced the tumor suppression effect of DTIC.

  Conclusion  OSM combined with DTIC has a synergistic effect that inhibits proliferation and apoptosis of B16 in vitro. This approach suggests a new potential treatment for melanoma.