Malignant melanoma is a common form of skin cancer that contains different cell types recognized by various cell surface markers. Dacarbazine-based combination chemotherapy is frequently used for the treatment of melanoma. Despite its potent anticancer properties, resistance to dacarbazine develops in malignant melanoma. Here, we aim to improve response to dacarbazine therapy by pretreatment with all-trans retinoic acid (ATRA) in CD117 melanoma cells.
The CD117 melanoma cells were sorted from A375 malignant melanoma cell line using magnetic-activated cell sorting (MACS). The cell viability was examined by cell proliferation assay (MTT). Apoptosis was determined by acridine orange/ ethidium bromide staining. Indeed, we performed flow cytometry to evaluate the cell cycle arrest.
Here, the CD117 melanoma cells were incubated with various concentrations of ATRA, dacarbazine, and their combination to determine IC values. We found that 20 µM ATRA treatment followed by dacarbazine was found to be more effective than dacarbazine alone. There was an indication that the combination of ATRA with dacarbazine (ATRA/dacarbazine) caused more apoptosis and necrosis in the melanoma cells (P<0.05). Furthermore, ATRA/dacarbazine treatment inhibited the cell at the G0/G1 phase, while dacarbazine alone inhibited the cells at S phase.
Collectively, combined treatment with ATRA and dacarbazine induced more apoptosis and enhanced the cell cycle arrest of CD117 melanoma cells. These results suggested that ATRA increased the sensitivity of melanoma cells to the effect of dacarbazine.

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