Insulin feedback is a targetable resistance mechanism of PI3K inhibition in glioblastoma.
Academic Article
Overview
abstract
BACKGROUND: Insulin feedback is a critical mechanism responsible for poor clinical efficacy of PI3K inhibition in cancer, and hyperglycemia is an independent factor associated with poor prognosis in glioblastoma. We investigated combination anti-hyperglycemic therapy in a mouse model of glioblastoma and evaluated the association of glycemic control in clinical trial data from patients with glioblastoma. METHODS: The effect of the anti-hyperglycemic regimens metformin and the ketogenic diet were evaluated in combination with PI3K inhibition in patient-derived glioblastoma cells and an orthotopic glioblastoma mouse model. Insulin feedback and the immune microenvironment were retrospectively evaluated in blood and tumor tissue from a Phase 2 clinical trial of buparlisib in patients with recurrent glioblastoma. RESULTS: We found that PI3K inhibition induces hyperglycemia and hyperinsulinemia in mice and that combining metformin with PI3K inhibition improves treatment efficacy in an orthotopic glioblastoma xenograft model. Through examination of clinical trial data, we found that hyperglycemia was an independent factor associated with poor progression-free survival in patients with glioblastoma. We also found that PI3K inhibition increased insulin receptor activation and T cell and microglia abundance in tumor tissue from these patients. CONCLUSION: Reducing insulin feedback improves the efficacy of PI3K inhibition in glioblastoma in mice, and hyperglycemia worsens progression-free survival in patients with glioblastoma treated with PI3K inhibition. These findings indicate that hyperglycemia is a critical resistance mechanism associated with PI3K inhibition in glioblastoma and that anti-hyperglycemic therapy may enhance PI3K inhibitor efficacy in glioblastoma patients.
