Kai Li, Haipeng Zhang, Jianguang Qiu, Yuan Lin, Jiankai Liang, Xiao Xiao, Liwu Fu, Fang Wang, Jing Cai, Yaqian Tan, Wenbo Zhu, Wei Yin, Bingzheng Lu, Fan Xing, Lipeng Tang, Min Yan, Jialuo Mai, Yuan Li, Wenli Chen, Pengxin Qiu, Xingwen Su, Guangping Gao, Phillip W L Tai, Jun Hu, Guangmei Yan

Oncolytic virotherapy is a novel and emerging treatment modality that uses replication-competent viruses to destroy cancer cells. Although diverse cancer cell types are sensitive to oncolytic viruses, one of the major challenges of oncolytic virotherapy is that the sensitivity to oncolysis ranges among different cancer cell types. Furthermore, the underlying mechanism of action is not fully understood. Here, we report that activation of cyclic adenosine monophosphate (cAMP) signaling significantly sensitizes refractory cancer cells to alphavirus M1 in vitro, in vivo, and ex vivo. We find that activation of the cAMP signaling pathway inhibits M1-induced expression of antiviral factors in refractory cancer cells, leading to prolonged and severe endoplasmic reticulum (ER) stress, and cell apoptosis. We also demonstrate that M1-mediated oncolysis, which is enhanced by cAMP signaling, involves the factor, exchange protein directly activated by cAMP 1 (Epac1), but not the classical cAMP-dependent protein kinase A (PKA). Taken together, cAMP/Epac1 signaling pathway activation inhibits antiviral factors and improves responsiveness of refractory cancer cells to M1-mediated virotherapy.Molecular Therapy (2015); doi:10.1038/mt.2015.172.