circ-1584 promotes the antitumor activity of oncolytic virus M1 selectively on pancreatic cancer

Pancreatic cancer is among the most challenging tumors to treat, and due to its immune tolerance characteristics, existing immunotherapy methods are not effective in alleviating the disease. Oncolytic virus therapy, a potential new strategy for treating pancreatic cancer, also faces the limitation of being ineffective when used alone. Elucidating the key host endogenous circular RNAs (circRNAs) involved in M1 virus-mediated killing of pancreatic ductal adenocarcinoma (PDAC) cells may help overcome this limitation. Here, we report that the oncolytic virus M1, a nonpathogenic alphavirus, exhibits different cell viability-inhibitory effects on different pancreatic cancer cells in the clinical stage. Through high-throughput circRNA sequencing, we found that circRNA expression varies among these cells. Further gain-of-function and loss-of-function experiments have shown that circ-1584 can selectively enhance the anti-pancreatic cancer effects of the M1 virus in vitro and in vivo. Additionally, circ-1584 may negatively regulate miR-578 to modulate the anti-pancreatic cancer effects of the M1 virus. Our findings lay the foundation for using circRNA as an adjuvant to enhance the M1 virus efficacy against pancreatic cancer.