| Malignant melanoma is resistant to almost all conventional forms of chemotherapy. Recent evidence suggests that anti-apoptotic proteins of the Bcl-2 family are overexpressed in melanoma and may contribute to melanoma's striking resistance to apoptosis. ABT-737, a small-molecule inhibitor of Bcl-2, Bcl-xl and Bcl-w, has demonstrated efficacy in several forms of cancer. However, overexpression of Mcl-1, a frequent observance in melanoma, is known to confer ABT-737 resistance.;Currently, there are no effective treatments for metastatic melanoma. My findings describe two potential combination therapies for melanoma as well as provide novel evidence as to the mechanisms involved in treatment response.;My results demonstrate that the combination of ABT-737 and RNA silencing of Mcl-1 induces significant cell death in six different melanoma cell lines, representing a potential new therapeutic strategy. I show that the apoptotic response to the combination treatment involves both the intrinsic pathway and a death receptor-independent role for extrinsic pathway proteins. The combination treatment also induces a number of gene expression changes as assessed by cDNA microarray and follow-up analyses. Based on the results of the array, I investigated the effects of inhibition of MAPK proteins combined with ABT-737 and/or Mcl-1 knockdown. I found that the combination of a p38 MAPK inhibitor and ABT-737 strongly and synergistically induces apoptosis in melanoma cell lines, thus suggesting a second novel treatment combination with potential for melanoma therapy. Finally, I provide novel evidence that Bcl-2 family member PUMA is cleaved in a caspase-dependent fashion during apoptosis and may play a role in treatment response. |
