FHIT gene expression is repressed by mitogenic signaling through the PI3K/AKT/FOXO pathway

Area of Science:

• Molecular Biology
• Cancer Biology
• Gene Regulation

Background:

• The Fragile Histidine Triad (FHIT) gene acts as a tumor suppressor in epithelial cells.
• Mechanisms regulating FHIT gene expression are not well understood.
• FHIT's role in tumor suppression is extensively studied, but its own regulation is less clear.

Purpose of the Study:

• To investigate the regulation of FHIT gene expression.
• To identify signaling pathways controlling FHIT expression in actively cycling cells.
• To elucidate the role of PI3K/AKT/FOXO signaling in FHIT gene regulation.

Main Methods:

• Cell culture experiments with growth factor stimulation and withdrawal.
• Analysis of FHIT mRNA and protein levels.
• Investigating the role of PI3K, AKT, and FOXO transcription factors.
• RNA interference (RNAi) targeting FOXO family members in MCF7 breast carcinoma cells.

Main Results:

• Phosphoinositide 3-kinase (PI3K) and AKT signaling suppress FHIT gene expression in response to growth factors.
• Removal of mitogens leads to increased FHIT mRNA and protein levels.
• AKT signaling regulates FHIT expression through FOXO transcription factors, specifically FOXO3a.
• FHIT expression is dependent on FOXO3a in MCF7 cells.

Conclusions:

• FHIT gene expression is actively repressed in cycling cells via the PI3K/AKT/FOXO3a pathway.
• This study reveals a novel regulatory mechanism for the tumor suppressor FHIT.
• Understanding FHIT regulation provides insights into cancer biology and potential therapeutic targets.