PRB inhibited cell proliferation through let-7b-E2F1 in breast cancer

Area of Science:

• Oncology
• Molecular Biology
• Genetics

Background:

• Progesterone receptor (PR) and its isoform B (PRB) presence correlates with better outcomes in breast cancer.
• Hormone-independent PR/PRB effects also show prognostic significance in non-small cell lung cancer (NSCLC).
• The precise mechanisms underlying PR/PRB's tumor-inhibitory roles remain largely undefined.

Purpose of the Study:

• To investigate the role of microRNAs (miRNAs) in tumor inhibition through progesterone receptor (PR)/PR isoform B (PRB) expression.
• To identify miRNAs with potential tumor-agnostic effects in both breast cancer and NSCLC.
• To elucidate the molecular pathway linking miRNAs, PR/PRB, and cancer cell proliferation.

Main Methods:

• Analysis of miRNA expression data from The Cancer Genome Atlas (TCGA) for breast cancer and NSCLC.
• Utilized PCR array data from an NSCLC patient cohort.
• Conducted in vitro functional studies using breast cancer cell lines to assess miRNA effects on PR/PRB expression and cell proliferation.
• Investigated the role of E2 promoter binding factor 1 (E2F1) as a mediator in the let-7b-PRB interaction.

Main Results:

• let-7b expression was significantly correlated with PR expression in both breast cancer and NSCLC.
• let-7b significantly inhibited cell proliferation by inducing PR and PRB expression in breast cancer cell lines.
• The let-7b-PRB correlation was mediated by E2F1, where let-7b inhibited E2F1, and E2F1 inhibited PRB.
• Immunohistochemical analysis in NSCLC corroborated the in vitro findings.

Conclusions:

• PRB inhibits breast cancer cell proliferation via the let-7b-E2F1 interaction pathway.
• This pathway may represent a conserved mechanism across different cancer types, including NSCLC.
• Targeting let-7b or PRB could offer novel therapeutic strategies for PR/PRB-positive breast and lung cancers.