Due to its potent anticancer activity, there is interest in repurposing of the FDA-approved anti-alcoholism drug, disulfiram (DSF). DSF forms potent complexes with copper (DSF/Cu) that induce apoptosis of many types of cancer cells. Here, we investigated the role of DSF/Cu in autophagy, a mechanism of cell death or survival, and its interplay with DSF/Cu induced apoptosis of human pancreatic and breast cancer cells.
Methods: Levels of autophagy and apoptosis were assessed by Western blot, flow cytometry and immunofluorescence analysis. Cell viability was measured by MTT assays. Activation of inositol-requiring enzyme 1α (IRE1α)-mRNA X-box binding protein 1 (XBP1) pathway and spliced XBP1 (XBP1s) expression were analyzed by Western blot, Phos-tag gel assay, RT-PCR, qRT-PCR and flow cytometry.
Results: The apoptosis induced by DSF/Cu in pancreatic and breast cancer cells is autophagy dependent. This is accomplished by activating IRE1α, the sensor of unfolded protein response (UPR) via promotion of phosphorylation of IRE1α and its downstream XBP1 splicing into active XBP1s.
Conclusions: DSF/Cu induces ER-stress through activation of IRE1α-XBP1 pathway which is responsible, at least in part, for induction of autophagy-dependent apoptosis of cancer cells. Insight into the ER-stress inducing ability by DSF/Cu may open a new research area for rational design of innovative therapeutic strategies for pancreatic and breast cancers.
Keywords: Disulfiram; ER stress; IRE1α pathway; XBP1s; apoptosis; cancer; cytotoxic autophagy.