ATF6 and melanoma: Figure 4B shows that following 24 hours of treatment, sensitivity of melanoma cells to Obatoclax was increased, most evidently in the ATF6, IRE1α and XBP-1 knockdown cells. Sensitivity to ABT-737 was also increased, albeit to a lesser extent. Additionally, Figure 4C indicates that while Mcl-1 was upregulated in the untransfected and control shRNA-transfected cells following 6 and 24 hours of treatment with Obatoclax or ABT-737, we observed that this upregulation of Mcl-1 was inhibited in the knockdown cells, particularly in those lacking IRE1α and XBP-1.