SLAMF1 Promotes Methotrexate Resistance via Activating Autophagy in Choriocarcinoma Cells

OBJECTIVE: The acquisition of chemoresistance to methotrexate (MTX) still remains one of the major challenges for choriocarcinoma treatment. Herein, we aimed to evaluate the potential role of Signaling Lymphocytic Activation Molecule Family Member 1 (SLAMF1) as a possible regulator of chemoresistance to MTX in choriocarcinoma. MATERIAL AND METHODS: MTX-resistant JEG3 and JAR sublines (JEG3/MTX, JAR/MTX) were used to study SLAMF1 function. CCK8 assay and soft agar assay were conducted to measure the cell viability and clonogenesis of choriocarcinoma cells, respectively; MDC incorporation assay was conducted for the quantification of intracellular autophagy; BrdU labeling was used to assess the proliferative potential of choriocarcinoma cells; SLAMF1 protein expression was analyzed by Western blotting. RESULTS: Upregulation of SLAMF1 expression was observed in MTX-resistant JEG3/MTX and JAR/MTX sublines compared to their parental JEG3 and JAR cell lines, respectively. Knockdown of SLAMF1 markedly attenuated cell viability and soft agar clonogenesis after incubation with MTX in JEG3/MTX and JAR/MTX cells. In contrast, constitutive expression of SLAMF1 rescued cell survival soft agar clonogenesis in JEG3 and JAR cells treated with MTX. Moreover, autophagy is apparently activated in MTX-resistant JEG3/MTX and JAR/MTX sublines compared to their parental cell lines. Autophagy inhibitor 3-methyladenine and bafilomycin A1 enhanced MTX-induced cytotoxicity in MTX-resistant JEG3 and JAR sublines. Further, SLAMF1 might activate autophagy-related mechanism to promote resistance to MTX in choriocarcinoma cells. Depletion of SLAMF1 suppressed autophagy and induced apoptosis in MTX-treated JEG3/MTX and JAR/MTX cells. CONCLUSION: SLAMF1 might promote MTX resistance via activating protective autophagy in choriocarcinoma cell lines. Targeting SLAMF1 might be a useful therapeutic strategy to sensitize choriocarcinoma cells to MTX-based regimens.