Activation of PI3K/AKT and MAPK pathway through a PDGFRβ-dependent feedback loop is involved in rapamycin resistance...

Area of Science:

• Hepatocellular Carcinoma Research
• Cancer Pharmacology
• Immunotherapy

Background:

• Rapamycin shows promise for preventing HCC recurrence post-transplant, but its efficacy is limited by resistance.
• Mechanisms of rapamycin resistance are not well-understood in HCC, necessitating further investigation.

Purpose of the Study:

• To elucidate the mechanisms of rapamycin resistance in HCC.
• To identify strategies for overcoming rapamycin resistance to improve HCC treatment outcomes.

Main Methods:

• Investigated rapamycin's anti-tumor effects in human and rat HCC cells in vitro and in vivo.
• Utilized RT-PCR and western blot to assess PDGFRβ expression and phosphorylation.
• Employed siRNA to knock down PDGFRβ and examined downstream signaling pathways (AKT, ERK).
• Evaluated the efficacy of combining rapamycin with sorafenib in an orthotopic HCC rat model.

Main Results:

• Rapamycin demonstrated modest anti-tumor activity in HCC models.
• Rapamycin treatment led to increased PDGFRβ expression and phosphorylation in HCC cells.
• PDGFRβ activation was found to mediate downstream signaling through AKT and ERK, contributing to rapamycin resistance.
• Sorafenib effectively blocked the PDGFRβ-dependent feedback loop, enhancing rapamycin's anti-tumor sensitivity.

Conclusions:

• PDGFRβ-dependent activation of PI3K/AKT and MAPK pathways compromises rapamycin's anti-tumor activity in HCC.
• Combining rapamycin with sorafenib to block this feedback loop represents a promising strategy to enhance anti-tumor effects.
• This combination therapy holds potential for preventing or treating HCC recurrence after liver transplantation.