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Abstract Patients with aggressive breast cancer (BC) subtypes usually do not have favorable prognosis despite improvements in treatment modalities. These cancers remain a major cause of morbidity and mortality in women globally. This has fostered a major effort to discover actionable molecular targets to treat these patients. Polo-like Kinase (PLK1) is one of these molecular targets that are under comprehensive investigation for the treatment of such tumors. However, its role in the pathogenesis of BC from Middle Eastern ethnicity has not been explored. Therefore, we examined the expression of PLK1 protein in a large cohort of more than 1500 Middle Eastern ethnicity BC by immunohistochemistry. Correlation with clinico-pathological parameters and the prognosis was performed. PLK1 overexpression was observed in 27. 4% of all BC and was significantly associated with aggressive clinico-pathological markers. The antitumor effect of PLK1 and PARP inhibitors either alone or in combination was tested in two BRCA mutated, and one BRCA proficient TNBC cell lines. We showed that combined inhibition significantly reduced cell survival and induced apoptosis in TNBC cell lines. Furthermore, our data suggest that PLK1 inhibition overcomes PARP inhibitor resistance in TNBC cell lines. These findings would pave the way to explore the future use of PLK1 inhibitors in the clinical setting of PARPi-resistant patients. Citation Format: Abdul K. Siraj, Pratheesh Kumar Poyil, Divya Padmaja, Sandeep Kumar Parvathareddy, Khadija Alobaisi, Rafia Begum, Osama Almalik, Fouad Al-Dayel, Khawla S. Al-Kuraya. PLK1 inhibition overcomes PARP inhibitor resistance in triple-negative breast cancer abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 7205.
Siraj et al. (Fri,) studied this question.