Pharmacological mTOR targeting enhances the antineoplastic effects of selective PI3Kα inhibition in medulloblastoma

Area of Science:

• Oncology
• Molecular Biology
• Cancer Research

Background:

• High-risk medulloblastoma patients have poor prognoses, with cancer stem cells contributing to treatment resistance and relapse.
• Targeting specific signaling pathways in medulloblastoma subgroups is crucial for overcoming resistance.
• Previous studies showed alpelisib, a PI3Kα inhibitor, has antineoplastic effects in medulloblastoma.

Purpose of the Study:

• To enhance the anti-medulloblastoma effects of alpelisib by combining it with mTOR kinase inhibition.
• To investigate the combined efficacy of PI3Kα and mTOR inhibition on medulloblastoma cell proliferation, stem-like properties, and tumor growth.
• To identify key molecular targets of this dual inhibition in specific medulloblastoma subtypes.

Main Methods:

• In vitro studies assessing cancer cell proliferation, colony formation, apoptosis, and sphere-forming ability.
• In vivo studies evaluating the impact of combined alpelisib and mTOR inhibition on medulloblastoma tumor growth.
• Identification of the HH pathway effector GLI1 as a target for dual PI3Kα/mTOR inhibition.

Main Results:

• Pharmacological mTOR inhibition significantly enhanced alpelisib's suppressive effects on medulloblastoma cell proliferation, colony formation, and apoptosis.
• Combined inhibition blocked the sphere-forming capacity of medulloblastoma stem-like cells in vitro.
• Dual PI3Kα/mTOR inhibition targeted GLI1 in SHH-type medulloblastoma and HH-driven Ewing sarcoma, and significantly reduced medulloblastoma tumor growth in vivo.

Conclusions:

• Combined PI3Kα and mTOR inhibition demonstrates potent anti-tumor activity against medulloblastoma, including stem-like cells.
• The PI3K/mTOR pathway plays a critical role in GLI1 regulation in HH-driven cancers.
• Dual PI3Kα/mTOR inhibition represents a promising therapeutic strategy for high-risk medulloblastomas.