let-7b/g silencing activates AKT signaling to promote gastric carcinogenesis

Area of Science:

• Oncology
• Molecular Biology
• Gene Regulation

Background:

• Aberrant AKT pathway activation is crucial for gastric cancer cell survival and chemoresistance.
• The regulatory mechanisms of AKT in gastric cancer remain poorly understood.
• microRNAs (miRNAs) are key regulators in gastric carcinogenesis, with let-7b and let-7g (let-7b/g) identified as potential players.

Purpose of the Study:

• To investigate the functional role of let-7b/g in gastric carcinogenesis.
• To identify and validate the target gene(s) of let-7b/g.
• To explore the therapeutic potential of targeting let-7b/g in gastric cancer.

Main Methods:

• Quantitative reverse transcription polymerase chain reaction (qRT-PCR) to assess let-7b/g expression in gastric cancer cell lines and primary tumors.
• Bioinformatic analysis (TargetScan) followed by experimental validation to identify let-7b/g targets.
• In vitro functional assays (MTT proliferation, colony formation, invasion) and in vivo studies using ectopic expression and knockdown approaches.

Main Results:

• let-7b/g expression was significantly downregulated in gastric cancer, correlating with poor survival and lymph node metastasis.
• let-7b/g directly targets AKT2, inhibiting its expression and subsequently reducing AKT phosphorylation (p-AKT S473) and downstream signaling (pS6).
• Knockdown of AKT2 mimicked the tumor-suppressive effects of let-7b/g, and AKT2 re-expression partially reversed these effects.

Conclusions:

• Reduced let-7b/g levels contribute to aberrant AKT activation in gastric tumorigenesis.
• let-7b/g acts as a tumor suppressor by inhibiting the AKT2 pathway.
• These findings suggest that let-7b/g represents a potential therapeutic target for gastric cancer.