Cisplatin‐mediated down‐regulation of miR‐145 contributes to up‐regulation of PD‐L1 via the c‐Myc transcription factor in cisplatin‐resistant ovarian carcinoma cells

Summary Immune tolerance is one of the leading causes of chemotherapy resistance in carcinoma cases. Studies have shown that programmed cell death ligand‐1 (PD‐L1), an inhibitory molecule expressed by cancer cells, plays a significant role in immune tolerance through the induction of T cell dysfunction. The results of our RNA sequencing in previous studies revealed that microRNA‐145 (miR‐145), which is known to be down‐regulated by cisplatin in cisplatin‐resistant ovarian cancer cells, also represses gene PD‐L1 expression. However, the mechanism by which miR‐145 contributes to regulate PD‐L1 expression in cisplatin resistance of ovarian cancer is yet to be fully understood. Here, we show that cisplatin‐mediated miR‐145 down‐regulation increased PD‐L1 expression via targeting the c‐Myc transcription factor, thereby inducing T cell apoptosis in vitro . We also report that expression of miR‐145 is negatively correlated with PD‐L1 expression in human ovarian cancer tissues, malignant grades and the recurrent risks of ovarian cancer after chemotherapy. In summary, our findings suggest that the miR‐145/c‐Myc/PD‐L1 axis contributes to cisplatin resistance in ovarian cancer and support that miR‐145 might act as an adjuvant therapeutic target in chemotherapy of ovarian cancer.