Oncolytic Avian Reovirus sigma A-Modulated Upregulation of the HIF-1 alpha/C-myc/glut1 Pathway to Produce More Energy in Different Cancer Cell Lines Benefiting Virus Replication

Our previous reports proved that the structural protein sigma A of avian reovirus (ARV) is an energy activator which can regulate cellular metabolism that is essential for virus replication. This study has further demonstrated that the ARV protein sigma A is able to upregulate the HIF-1 alpha/myc/glut1 pathway in three cancer cell lines (A549, B16-F10, and HeLa) to alter the metabolic pathway of host cells. Quantitative real-time RT-PCR and Western blotting results have revealed that sigma A protein could enhance both mRNA and the protein levels of HIF-1 alpha, c-myc, and glut1 in these cancer cell lines. In this work, ATeam immunofluorescence staining was used to reveal that knockdown of HIF-1 alpha, c-myc, and glut1 by shRNAs decreased cellular ATP levels. Our data reveal that the ARV sigma A protein can downregulate lactate fermentation and upregulate glutaminolysis. The sigma A protein upregulates glutaminase, which converts glutamate into the TCA cycle intermediate alpha-ketoglutarate, activating the TCA cycle. In the lactate fermentation pathway, ARV sigma A protein suppresses lactate dehydrogenase A (LDHA), implying the Warburg effect does not occur in these cancer cell lines. This study provides a novel finding revealing that ARV sigma A protein upregulates glycolysis and glutaminolysis to produce energy using the HIF-1 alpha/c-myc/glut1 pathway to benefit virus replication in these cancer cell lines.