TFAM is a novel mediator of immunogenic cancer cell death

Immunogenic cell death (ICD) is a type of cell death that is accompanied by the release of damage-associated molecular patterns (DAMPs) and results in a dead-cell antigen-specific immune response. Here, we report that spautin-1, an inhibitor of ubiquitin-specific peptidases, triggers immunogenic cancer cell death in vitro and in vivo. The anticancer activity of spautin-1 occurs independent of autophagy inhibition, but depends on the intrinsic mitochondrial apoptosis pathway. Spautin-1 causes mitochondrial oxidative injury, which results in JUN transcription factor activation in a JNK-dependent manner. Mechanistically, activation of JUN by spautin-1 leads to apoptosis by upregulation of pro-apoptotic BAD expression. Importantly, the release of TFAM, a mitochondrial DAMP, by apoptotic cells may contribute to spautin-1-induced ICD via its action on the receptor AGER. Indeed, cancer cells treated with spautin-1 in vitro were able to elicit an anticancer immune response when inoculated in vivo, in the absence of any adjuvant. This immunogenic effect of spautin-1-treated cancer cells was lost when TFAM or AGER were neutralized by specific antibodies. Altogether, our results suggest that spautin-1 may stimulate an apoptotic pathway that results in ICD, in TFAM- and AGER-dependent fashion.