MCL-1 (BCL-2 family anti-apoptotic protein) is responsible for melanoma's resistance to therapy.,Cancer initiating cells also contribute to resistance and relapse from treatments.,Here we examined the effects of the MCL-1 inhibitor SC-2001 in killing non melanoma-initiating-cells (bulk of melanoma), and melanoma-initiating-cells (MICs).,By itself, SC-2001 significantly kills melanoma cells under monolayer conditions in vitro and in a conventional mouse xenograft model.,However, even at high doses (10μM), SC-2001 does not effectively eliminate MICs.,In contrast, the combination of SC-2001 with ABT-737 (a BCL-2/BCL-XL/BCL-W inhibitor) significantly decreases ALDH+ cells, disrupts primary spheres, and inhibits the self-renewability of MICs.,These results were observed in multiple melanomas, including short term cultures of relapsed tumors from current treatments, independent of the mutation status of BRAF or NRAS.,Using a low-cell-number mouse xenograft model, we examined the effects of these treatments on the tumor initiating ability of MIC-enriched cultures.,The combination therapy reduces tumor formation significantly compared to either drug alone.,Mechanistic studies using shRNA and the CRISPR-Cas9 technology demonstrated that the upregulation of pro-apoptotic proteins NOXA and BIM contribute to the combination-induced cell death.,These results indicate that the MCL-1 inhibitor SC-2001 combined with ABT-737 is a promising treatment strategy for targeting melanoma.
Epidemiological studies propose that obesity increases the risk of several cancers, including melanoma.,Obesity increases the expression of leptin, a multifunctional peptide produced predominantly by adipocytes which may promote tumor growth.,Several recently experiments have suggested that the tumors growth is in need of endothelial progenitor cell (EPC) dependent generation of new blood vessels.,Our objectives in the present study were to examine the effects of leptin on melanoma growth, circulating EPCs number and plasma levels of nitric oxide metabolites (NOx).,2 × 106 B16F10 melanoma cells were injected to thirty two C57BL6 mice subcutaneously.,The mice were randomly divided into 4 groups (n = 8) in 8th day.,Two groups were received twice daily intraperitoneal(i.p) injections of either PBS or recombinant murine leptin (1 μg/g initial body weight).,Two groups were received i.p. injections of either 9F8 an anti leptin receptor antibody or the control mouse IgG at 50 μg/mouse every 3 consecutive days.,By the end of the second week the animals were euthanized and blood samples and tumors were analyzed.,The tumor weight, EPC numbers and NOx level in leptin, PBS, 9F8, and IgG group were (3.2 ± 0.6, 1.7 ± 0.3, 1.61 ± 0.2,1.7 ± 0.3 g), (222.66 ± 36.5, 133.33 ± 171, 23.33 ± 18, 132.66 ± 27.26/ml of blood), and (22.47 ± 5.5, 12.30 ± 1.5, 6.26 ± 0.84, 15.75 ± 6.3 μmol/L) respectively.,Tumors weight and size, circulating EPC numbers and plasma levels of NOx were significantly more in the leptin than 9f8 and both control groups (p < 0.05).,The plasma concentration of NOx significantly decreased in 9f8 treated mice compare to control group (p < 0.05).,In conclusion, our observations indicate that leptin causes melanoma growth likely through increased NO production and circulating EPC numbers and consequently vasculogenesis.