Chemical inhibition of the heat shock response downregulates<i> ERCC1</i> gene expression and shifts carboplatin-induced necrosis to apoptosis in TNBC cells

Reisoglu B., Arslan M. A.

TRAKYA UNIVERSITY JOURNAL OF NATURAL SCIENCES, vol.27, no.1, pp.47-56, 2026 (ESCI, Scopus, TRDizin)

Abstract

Background: Triple-negative breast cancer (TNBC) is an aggressive cancer type associated with poor prognosis and limited therapeutic options. Due to the absence of targetable receptors, conventional chemotherapy remains the primary treatment approach. ERCC1 is a critical component of the nucleotide excision repair system, responsible for repairing DNA damaged by platinum-based agents like carboplatin. Heat shock response (HSR) is a fundamental, stress-induced defense mechanism that supports cancer cell survival. Aims: This study aims to investigate the effects of HSR inhibition by KNK437 on ERCC1 gene expression and carboplatin sensitivity in the TNBC cell line MDA-MB-231. Methods: The IC50 values of carboplatin and KNK437 were determined using WST-8 cytotoxicity assay. ERCC1 gene expression levels were quantified by real-time quantitative polymerase chain reaction. Apoptotic and necrotic cell death induced by carboplatin and KNK437 was assessed by flow cytometry using FITC-Annexin V assay. Results: The IC50 values of carboplatin and KNK437 were 247.5 & micro;M and 89.74 & micro;M, respectively. Carboplatin or KNK437 monotherapy significantly decreased ERCC1 expression by 42.8% and 49.5%, respectively, while their combined application caused a 54.9% reduction. Furthermore, co-treatment markedly increased total cell death by 34.1% compared to carboplatin alone. Interestingly, necrosis induced by carboplatin shifted toward apoptosis upon co-treatment with KNK437, as confirmed by light microscopy and flow cytometry. Conclusion: HSR inhibition by KNK437 enhances carboplatin sensitivity in TNBC cells and downregulates ERCC1 gene expression. Given the aggressive nature of TNBC and its limited treatment options, our results suggest that KNK437 may offer therapeutic advantages when combined with carboplatin, particularly in contexts where carboplatin-induced necrosis contributes to inflammation-related complications.