Abstract: Objective To investigate the effect of anti-angiogenic drug Sitravatinib combined with poly(adenosine diphosphate[ADP]-ribose) polymerase inhibitor(PARPi) Niraparib on mucosal melanoma cell lines and its possible mechanism. Methods The CCK8 assay was used to detect the maximal half inhibitory concentration (IC₅₀) of Sitravatinib and Niraparib targeting at mucosal melanoma (MM) cell lines. CompuSyn was used to detect the Combination Index (CI) in different concentrations of the two drugs. Flow cytometry was used to detect the effect of drugs on cell apoptosis. Colony formation assay was used to detect the effect of drugs on cell proliferation. Western blot was used to detect the protein expressions and RT-qPCR was used to detect mRNA expression. Results CI values was respectively 0.19 and 0.15 for Sitravatinib (2 μmol/L) in combination with Niraparib (20 μmol/L) in a human vaginal maligant melanoma cell line (HMVII) and a metastasis inguinal lymph node of vulvar malignant melanoma cell line (GAK). Compared with the control group and single-drug groups, the cell proliferation of the combination group was significantly reduced (P＜0.05 or P＜0.01 or P＜0.001). The cell apoptosis rate was significantly increased (P＜0.01 or P＜0.001). The protein and mRNA expression of apoptosis-related biomarkers significantly increased (P＜0.001); In addition, the protein and mRNA expression of cell autophagy biomarkers significantly increased (P＜0.01 or P＜0.001). The protein expression of DNA damage marker significantly increased. Moreover, compared with the control group, The expression of radiation sensitive protein 51 (RAD51) recombinase in the Sitravatinib single-drug group and combination group significantly reduced. As the dose of Sitravatinib gradually increased up to 2 μmol/L, the protein and mRNA expression of RAD51 both significantly reduced (P＜0.05 or P＜0.01), the mRNA expression of BRCA1 and BRCA2 also significantly reduced (P＜0.05 or P＜0.01 or P＜0.001). Conclusions Sitravatinib combined with Niraparib inhibits the proliferation of mucosal melanoma cells, induces cell apoptosis and promotes autophagy. The mechanism is potentially related to the inhibition of homology-dependent recombination repairs(HRR).

Key words: mucosal melanoma, anti-angiogenic drug, poly(adenosine diphosphate-ribose) polymerase inhibitor, homology-dependent recombination repair