Impact of the PI3KC2α Y1595H mutation in cholangiocarcinoma progression

Cholangiocarcinoma is the second most prevalent primary hepatic cancer, presenting increased incidence, aggressive clinical course, and poor prognosis. Several risk factors and mutations are associated with this malignancy, contributing to a chronic inflammatory environment and/or cholestasis, which trigger cholangiocarcinoma progression. Transcriptomic analysis of precursor and malignant lesions in a mouse model of intrahepatic cholangiocarcinoma resulted in the identification of the same point mutation c.4783T>C in PI3KC2α in two out of three mice. This gene codes for phosphatidylinositol4-phosphate 3-kinase catalytic subunit type 2 alpha, an enzyme that phosphorylates phosphoinositols from the cellular membrane, and is implicated in a wide range of cellular processes, including vesicular trafficking, cell proliferation, and migration. PI3KC2α was recently suggested to play a role in tumorigenesis, however, its mechanism remains unknown. Since c.4783T>C mutation causes a Y1595H amino acid change that has not been described yet, we have investigated its potential impact in tumor progression. First, to determine if this mutation affects the protein’s function and structure, we resorted to several in silico tools, which predicted that the Y1595H mutation may modulate phosphoinositol binding without affecting the overall protein’s structure. Next, we implemented CRISPR/Cas-9 genome editing in human cholangiocarcinoma EGI-1 cells to generate a clonal line containing the c.4783T>C mutation. In vitro, we found some evidence supporting partial epithelial-mesenchymal transition in the PI3KC2α Y1595H mutant EGI-1 cells. In addition, we found increased clonogenicity and migration, along with perturbed cell cycling. In vivo, histological analyses of mutant cell-derived tumors revealed changes in the distribution of the extracellular matrix. In conclusion, our data require further strengthening but are compatible with a tumor-promoting role of PI3KC2α Y1595H.