Hsp27 Protects Triple-Negative Breast Cancer Cells against Carboplatin-Induced Cytotoxicity via the Maintenance of Late-Stage Autophagy.

INTRODUCTION

Triple-Negative Breast Cancer (TNBC) is a highly aggressive subtype of breast cancer associated with poor prognosis and limited treatment options. Due to the lack of targetable receptors, standard chemotherapy remains the main treatment for TNBC. Heat shock proteins and (macro)autophagy are fundamental stressresponsive systems involved in oncogenesis and increasingly recognized to act in a coordinated manner. This study aimed to investigate the role of Hsp27 in autophagy regulation in response to carboplatin in TNBC cells.

METHODS

The IC50 of carboplatin was determined using WST-8 assay. Hsp27 was silenced via siRNA transfection. Autophagic activity was evaluated by Western blot analysis of LC3-II and p62. Cell death was measured using Annexin V-based flow cytometry.

RESULTS

Autophagic flux assays conducted with the autophagy inhibitor bafilomycin A1 revealed that Hsp27 depletion blocks the late stage of carboplatin-induced autophagy, as demonstrated by elevated LC3-II levels not further increasing with bafilomycin A1 treatment but remaining unchanged. Additionally, LC3-II accumulation in Hsp27-silenced cells increased in a dose-dependent manner with carboplatin, with 1 mM carboplatin resulting in peak LC3-II levels, accompanied by 50.7% increase in cell death compared to control cells. Collectively, Hsp27 confers cytoprotection against carboplatin-induced toxicity in MDA-MB-231 cells by promoting latestage autophagy.

DISCUSSION: Given the aggressive nature of TNBC and its limited treatment options, our findings suggest that targeting Hsp27 has the potential to enhance the efficacy of carboplatin chemotherapy by suppressing cytoprotective autophagy.

CONCLUSION

Our findings demonstrate that depletion of Hsp27 sensitizes human TNBC cells to carboplatininduced cell death through inhibition of late-stage autophagy.