Dual blockage of PI3K-mTOR and FGFR induced autophagic cell death in cholangiocarcinoma cells.

Purpose: To assess the impact of concurrent inhibition of the FGFR and PI3K/mTOR signaling pathways on oncogenic characteristics in cholangiocarcinoma (CCA) cells, including proliferation, autophagy, and cell death. Materials and methods: KKU-213A, KKU-100, and KKU-213C cells were treated with either infigratinib or PKI-402 alone or in combination. Cell viability and cell death were evaluated using the sulforhodamine B (SRB) assay and acridine orange/ethidium bromide (AO/EB) staining. Cell cycle progression and apoptotic cell death were analyzed by flow cytometry. Western blotting was performed to assess the expression of proteins involved in cell cycle regulation and autophagy. Additionally, AO staining was employed to assess autophagic induction. Results: The combination of infigratinib and PKI-402 showed a remarked synergistic suppression in cell viability in both CCA cell lines compared to treatment with single inhibitors. This antiproliferative effect was associated with cell cycle arrest in the G2-M phase and a decrease in the expression of cyclin A and cyclin B1 in CCA cells. Furthermore, the combination treatment induced apoptotic cell death to a greater extent than treatment with a single inhibitor. Infigratinib enhanced the induction of autophagy by PKI-402, as evidenced by marked increases of autophagic vacuoles stained acridine orange, levels of LC3B-II and suppression of levels of p-mTOR and. Notably, inhibition of autophagic flux by chloroquine prevented cell death induced by the combination treatment. Conclusions: This study demonstrated that concurrent inhibition of the key FGFR/PI3K/mTOR pathways in CCA carcinogenesis enhances the suppression of CCA cells. The present findings indicate potential clinical implications for using combination treatment modalities in CCA therapy.