Use of chemical genomics in assessment of the UPR

Glucose deprivation, one of the major physiological conditions in solid tumor, leads to activation of the unfolded protein response (UPR) in cancer cells. The UPR occurs through the transcriptional and translational regulatory mechanisms that improve the capacity of the endoplasmic reticulum (ER) to fold and traffic proteins and allows the cell to survive under stress conditions. We previously reported that the macrocyclic compound versipelostatin and the antidiabetic biguanides metformin, buformin, and phenformin could inhibit the UPR during glucose deprivation as well as induce the UPR by treatment of cells with 2-deoxy-d-glucose (2DG), a glycolysis inhibitor. Versipelostatin and biguanides show highly selective cytotoxicity to glucose-deprived tumor cells and exert in vivo antitumor activity; thus, these compounds would be interesting anticancer agent candidates. By microarray analysis, we demonstrated that cancer cells under glucose deprivation conditions caused activation of the UPR transcription program, which was suppressed broadly by versipelostatin and biguanides. We also identified the drug-driven gene signatures that can be used to discover pharmacologic UPR modulators. Indeed, we found several bioactive drugs, such as pyrvinium pamoate, valinomycin, and rottlerin, that selectively suppressed 2DG-induced GRP78 promoter activity as versipelostatin and biguanide did. Together with growing bioinformatics databases and analytical tools, our approach could provide a chemical genomic basis for developing UPR-targeting drugs against solid tumors.