Targeting EGFR Activation to Overcome Gemcitabine Resistance in Cholangiocarcinoma.

Background/aim: Chemotherapy resistance is an important problem in the treatment of patients with cholangiocarcinoma (CCA) who are not eligible for surgery. This study aimed to overcome gemcitabine (Gem) resistance in CCA by investigating and targeting Gem resistance-associated molecules.

Materials And Methods: Three stable Gem-resistant CCA cell lines (CCA-GemR) were established by gradually exposing CCA cell lines to Gem. The cells were characterized in terms of growth, cross-resistance to chemotherapeutic drugs, cell cycle distribution, and colony formation. The molecular mechanisms related to Gem resistance were assessed using a phosphorylation array assay and protein expression was confirmed using western blotting analysis. The targeted molecules were subsequently analyzed using PanDrugs to identify potential targeted therapies. The drug was used to enhance Gem sensitivity.

Results: The results demonstrated that CCA-GemR cells grow more slowly compared to their parental cell lines. Cell cycle analysis revealed an increase in KKU-213A-GemR and KKU-213B-GemR cell accumulation in the G1 phase. Moreover, cross-resistance to 5-FU and cisplatin was observed in all CCA-GemR cells. The Proteome Profiler Human Phospho-Kinase Array showed increased phosphorylation of EGFR in CCA-GemR cells. Erlotinib, a specific inhibitor of EGFR, significantly enhanced the anti-tumor activity of Gem with a synergistic effect (Combination index <1). Western blot analysis confirmed that phosphorylation of EGFR increased in cells treated with Gem, whereas the expression was significantly decreased in cells treated with either erlotinib alone or in combination with Gem.

Conclusion: EGFR is a potential target molecule for reducing Gem resistance and enhancing its anti-tumor effects in patients with CCA.