Genotoxicity and apoptotic effect of silver(I) complexes with mixed-ligands of thiosemicarbazones and diphenyl(p-tolyl)phosphine on malignant melanoma cells, SK-MEL-28

Complexes of coinage metals can potentially be used as alternatives to platinum-based chemotherapeutic drugs. Silver is a coinage metal that can potentially improve the spectrum of efficacy in various cancers treatment, such as malignant melanoma. Melanoma is the most aggressive form of skin cancer that is often diagnosed in young and middle-aged adults. Silver has high reactivity with skin proteins and can be developed as a malignant melanoma treatment modality. Therefore, this study aims to identify the anti-proliferative and genotoxic effects of silver(I) complexes with mixed-ligands of thiosemicarbazones and diphenyl(p-tolyl)phosphine ligands in the human melanoma SK-MEL-28 cell line. The anti-proliferative effects of a series of silver(I) complex compounds labelled as OHBT, DOHBT, BrOHBT, OHMBT, and BrOHMBT were evaluated on SK-MEL-28 cells by using the Sulforhodamine B assay. Then, DNA damage analysis was performed in a time-dependent manner (30 min, 1 h and 4 h) by using alkaline comet assay to investigate the genotoxicity of OHBT and BrOHMBT at their respective IC50 values. The mode of cell death was studied using Annexin V-FITC/PI flow cytometry assay. Our current findings demonstrated that all silver(I) complex compounds showed good anti-proliferative activity. The IC50 values of OHBT, DOHBT, BrOHBT, OHMBT, and BrOHMBT were 2.38 ± 0.3 μM, 2.70 ± 0.17 μM, 1.34 ± 0.22 μM, 2.82 ± 0.45 μM, and 0.64 ± 0.04 μM respectively. Then, DNA damage analysis showed that OHBT and BrOHMBT could induce DNA strand breaks in a time-dependent manner, with OHBT being more prominent than BrOHMBT. This effect was accompanied by apoptosis induction in SK-MEL-28, as evaluated using Annexin V-FITC/PI assay. In conclusion, silver(I) complexes with mixed-ligands of thiosemicarbazones and diphenyl(p-tolyl)phosphine exerted anti-proliferative activities by inhibiting cancer cell growth, inducing significant DNA damage and ultimately resulting in apoptosis.