Modulation of ferroptotic cell death by mitochondrial calcium signaling

Project Summary/Abstract Ferroptosis is a unique type of programmed cell death that is induced by excessive lipid peroxidation. Emerging evidence suggests that ferroptosis represents a vulnerability in certain types of cancer that have acquired resistance to therapies. However, the signaling mechanisms that can be harnessed to promote

cancer cell ferroptosis and its functional consequence on the tumor microenvironment (TME) reprogramming are poorly understood. In this Proposal, we aim to study a previously unrecognized anti-ferroptotic effect imparted by mitochondrial calcium signaling, which may also contribute to the establishment of

immunosuppressive TME. Mitochondrial calcium uniporter (MCU) is a highly selective calcium channel that is localized to the inner mitochondrial membrane, which promotes the production of metabolite acetyl-coenzyme A (acetyl-CoA) by targeting the pyruvate dehydrogenase (PDH). In preliminary studies, we discovered that

MCU-mediated acetyl-CoA generation blocks both cancer cell ferroptosis and antitumor immunity. We found that genetic ablation of Mcu (Mcu−/−) abolished acetylation of the glutathione peroxidase 4 (GPX4), a critical gatekeeper of ferroptosis, which correlated with impaired GPX4 activity and enhanced sensitivity to ferroptosis

induction. Moreover, Mcu deficiency in cancer cells significantly blunted their growth and improved antitumor immune response. Therefore, blockade of MCU function may represent a promising therapeutic regimen for cancer. The goal of our proposed research proposal is to examine the function and mechanism of MCU-

mediated acetyl-CoA metabolism on GPX4-controlled ferroptosis and its impact on antitumor immunity. We hypothesize that 1) decreased acetyl-CoA production in the absence of MCU sensitizes cancer cells to ferroptosis due to GPX4 hypoacetylation; 2) elevated ferroptotic cell death of Mcu−/− cancer cells promotes the

production of type 1 interferon by intratumoral myeloid cells via the cyclic GMP-AMP synthase (cGAS)- dependent DNA-sensing pathway, leading to enhanced antitumor immunity; and 3) pharmacological inhibition of MCU by MCU-i11 synergizes with programmed death-1 (PD-1) blockade in limiting tumor growth.

Representative syngeneic tumor models with high or low immunogenicity will be employed to examine the effect of MCU-mediated ferroptosis on antitumor immunity. Single-cell RNA sequencing analysis of tumor- infiltrating immune cells in response to MCU-i11 treatment will be performed to understand whether MCU

inhibition promotes antitumor immunity. Results of these studies will provide novel insights into the induction and function of ferroptosis in rejuvenating antitumor immunity, which can potentially lead to the identification of new therapeutic targets in cancer treatment.