mTOR activation is critical for betulin treatment in renal cell carcinoma cells

Area of Science:

• Oncology
• Natural Products Chemistry
• Molecular Biology

Background:

• The mTOR signaling pathway is frequently activated in renal cell carcinoma (RCC).
• Betulin, a natural product from birch bark, has demonstrated anticancer properties.
• Understanding betulin's mechanism in RCC, particularly its interaction with mTOR, is crucial for therapeutic development.

Purpose of the Study:

• To investigate the role of the mTOR signaling pathway in betulin's anti-RCC effects.
• To determine if mTOR activation influences sensitivity to betulin treatment in RCC cells.
• To elucidate the downstream targets of betulin's action in RCC.

Main Methods:

• Cell survival and colony formation assays were used to assess betulin's effect on RCC cell lines with varying mTOR activity.
• Genetic manipulation (TSC2 knockdown, mTOR silencing, PKM2/HK2 knockdown/overexpression) was employed to confirm pathway dependency.
• Glucose consumption and lactate production assays were performed to evaluate metabolic changes.
• Western blotting was used to analyze protein expression levels of PKM2 and HK2.

Main Results:

• mTOR-hyperactive RCC cells (786-O) were more sensitive to betulin than mTOR-inactive cells (Caki-2).
• Betulin's anti-proliferative effect was dependent on mTOR signaling, as evidenced by rescue experiments.
• Betulin treatment reduced glucose uptake and lactate production, and inhibited PKM2 and HK2 expression in 786-O cells.
• Modulating PKM2 or HK2 levels altered sensitivity to betulin, confirming their role in the mechanism.

Conclusions:

• mTOR activation is critical for betulin's efficacy in inhibiting RCC cell proliferation.
• Betulin affects glucose metabolism by downregulating PKM2 and HK2 in an mTOR-dependent manner.
• Betulin holds promise as a targeted therapy for RCC patients with activated mTOR signaling.