Combinational therapy of all-trans retinoic acid (ATRA) and sphingomyelin induces apoptosis and cell cycle arrest in B16F10 melanoma cancer cells

Background/aim: Melanoma arises from the uncontrolled multiplication of melanocytes, and poses an escalating global health concern. Despite the importance of early detection and surgical removal for effective treatment, metastatic melanoma poses treatment challenges, with limited options. Among optional therapies, including chemotherapy and immunotherapy, all-trans retinoic acid (ATRA), a natural metabolite of vitamin A, has shown promise in treating melanoma by inducing differentiation, apoptosis, growth arrest, and immune modulation in melanoma cells. However, ATRA treatment alone can lead to resistance and relapse. Furthermore, sphingomyelin (SM) was implicated in the inhibition of cell proliferation, differentiation, and apoptotic cell death during melanoma progression. Materials and methods: The combinational anticancer effects of ATRA and SM on an in vitro B16F10 melanoma model were investigated based on cell viability, apoptotic cell death, cell cycle progression, and gene expression levels; whereas the safety properties of the treatments were tested on RAW264.7 macrophages. Results: The combination of 123 mu M of ATRA + 136 mu M of SM was the most effective treatment, showing a 50% reduction in cell proliferation, leading to 53.91% apoptotic cell death in 48 h, and G2/M phase-cell cycle arrest in the B16F10 cells. While 123 mu M of ATRA alone did not change the caspase 3 and Bax gene expressions, the combinational ATRA + SM treatment resulted in 2- and 5-fold increases in the gene expression level, respectively. A 13-fold increase in cyclin-dependent kinase inhibitor 2A was observed with the combinational ATRA + SM treatment, while suppressing the programmed death ligand 1 (PD-L1) expression by 0.5-fold. Conclusion: Combinational ATRA and SM therapy could be a promising therapeutic approach for melanoma, potentially improving efficacy, while reducing toxicity to healthy cells.