Abstract 552: Functional effects of miPEP133 on mitochondrial integrity and treatment response in ovarian cancer.

Abstract Background: MiPEP133 is a microprotein encoded by the miR-34a precursor. In normal cells, it functions as a tumor suppressor and is expressed in colon, stomach, ovary, uterus, and pharynx, but its levels are markedly reduced in cancer. Localized in the mitochondria, miPEP133 regulates mitochondrial homeostasis through interactions with mitochondrial chaperones and has been reported to induce apoptosis and inhibit tumor cell migration in other cancer types. However, its functional role in ovarian cancer remains poorly defined. We investigated the biological impact of miPEP133 overexpression in patient-derived high grade serous ovarian cancer cell lines to further characterize its cellular effects and therapeutic relevance. Methods MiPEP133 was overexpressed in two patient-derived ovarian cancer cell lines using lentiviral vectors. Protein expression was confirmed by western blot. Cell growth kinetics were assessed using flow-cytometry-based proliferation assays. Mitochondrial morphology was evaluated by immunofluorescence staining. Sensitivity to chemotherapeutic agents (carboplatin and paclitaxel), MEK inhibitors, and mitochondrial modulators were measured using CellTiter-Glo assays. Apoptosis was quantified by Annexin V/PI staining and flow cytometry. Gene expression changes in treated and untreated miPEP133-overexpressing and control cells were evaluated by quantitative PCR (qPCR). Results Overexpression of miPEP133 in the ovarian cancer cell lines led to a moderate reduction in cell proliferation, consistent with growth suppression. Immunofluorescence analysis revealed disruption of mitochondrial network structure and a decrease in mitochondrial mass. MiPEP133-overexpressing cells exhibited significantly increased sensitivity to MEK inhibitors and selected chemotherapeutic agents compared with control cells. Annexin V staining demonstrated increased apoptotic populations following chemotherapeutic treatment. qPCR analysis validated upregulation of genes involved in apoptosis, mitochondrial stress response, and oxidative stress pathways in miPEP133-overexpressing cells treated with MEK inhibitors and mitochondrial modulators. Conclusion These findings further characterize miPEP133 as a suppressor of ovarian cancer cell growth and a regulator of mitochondrial integrity in cancer cells. The restoration of miPEP133 function in ovarian cancer cells can enhance their sensitivity to chemotherapeutic and MEK-inhibitors. MiPEP133 represents a promising tumor suppressor with potential utility as both a therapeutic sensitizer and a biomarker in ovarian cancer. Citation Format: Samantha Goncalves Novo, Miranda Mansolf, Tobias M. Hartwich, Jasmine Jathan, Viktoriia Kolesnyk, Yang Yang-Hartwich. Functional effects of miPEP133 on mitochondrial integrity and treatment response in ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 552.