Linarin Reverses Doxorubicin Resistance by Modulating PTEN and MDR1 Expression in MCF-7 Breast Cancer Cells

Abstract

Introduction: Chemoresistance in breast cancer remains a major obstacle that limits the effectiveness of current therapeutic options for patients. Therefore, the identification or development of adjuvant compounds with minimal side effects to enhance the efficacy of standard treatments continues to be an important goal in cancer therapy. In this study, we investigated the impact and molecular mechanisms of linarin to overcome drug resistance in the doxorubicin-resistant MCF-7 breast cancer cell line (MCF-7/DOX). Methods: The cytotoxic effects of linarin were assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. MDR-1 and PTEN mRNA/protein expression levels were quantified by quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and western blotting. Rhodamine 123 uptake was measured after linarin treatment to assess P-glycoprotein (P-gp) activity, and flow cytometry was performed to evaluate cell death. Results: Our findings indicate that linarin significantly enhanced the cytotoxicity of doxorubicin and reduced the resistance index in MCF-7/DOX cells (p < 0.05). Linarin treatment also led to a marked downregulation of MDR1 mRNA expression and a decrease in P-gp levels. Increased intracellular accumulation of Rhodamine 123 was observed, suggesting inhibition of P-gp activity and reduced drug efflux. Notably, linarin upregulated both gene expression and protein levels of PTEN in MCF-7/DOX cells, which are typically characterized by low PTEN levels. Conclusion: Our findings suggest that linarin may represent a promising adjunct therapeutic agent for overcoming resistance to conventional chemotherapeutic drugs. This effect may be mediated through PTEN upregulation, which appears to play a role in suppressing P-gp-associated resistance mechanisms.