Targeting of miR34a-NOTCH1 axis reduced breast cancer stemness and chemoresistance

Area of Science:

• Oncology
• Molecular Biology
• Genetics

Background:

• Human breast cancers contain cancer stem cells (CSCs) with self-renewal and chemotherapy resistance.
• MicroRNAs (miRNAs) are key regulators of gene expression, and their dysregulation is implicated in cancer pathogenesis.
• The role of miRNA dysregulation in CSC stemness and drug resistance remains largely unexplored.

Purpose of the Study:

• To investigate the role of miR34a in breast cancer stemness and chemoresistance.
• To explore the relationship between p53 mutation and miR34a downregulation in drug-resistant breast cancer cells.
• To evaluate the therapeutic potential of restoring miR34a expression in chemoresistant breast cancer.

Main Methods:

• Compared miR34a expression in MCF7 and MCF7/ADR (doxorubicin-resistant) cells.
• Investigated the effect of p53 modulation (RNAi, dominant-negative mutant) on miR34a expression in MCF7 cells.
• Assessed the impact of ectopic miR34a expression on CSC properties and doxorubicin sensitivity.
• Evaluated the in vivo efficacy of miR34a in a mouse xenograft model.

Main Results:

• miR34a expression was significantly downregulated in MCF7/ADR cells compared to MCF7 cells.
• p53 modulation (RNAi or dominant-negative mutant) suppressed primary and mature miR34a in MCF7 cells.
• Ectopic miR34a expression reduced CSC characteristics and enhanced doxorubicin sensitivity by targeting NOTCH1.
• In vivo studies showed that miR34a treatment significantly reduced tumor size in nude mice.

Conclusions:

• Downregulation of miR34a, potentially due to p53 mutation, contributes to stemness and chemoresistance in breast cancer.
• Restoring miR34a expression can overcome chemoresistance and reduce CSC properties.
• Ectopic miR34a delivery represents a promising therapeutic strategy for treating chemoresistant breast cancer.