Tight Junction Protein Claudin-2 Promotes Self-Renewal of Human Colorectal Cancer Stem-like Cells

Post-treatment recurrence of colorectal cancer (CRC), the third most lethal cancer worldwide, is often driven by a subpopulation of cancer stem cells (CSCs). The tight junction (TJ) protein claudin-2 is overexpressed in human CRC where it enhances cell proliferation, colony formation, and chemoresistance in vitro. While several of these biological processes are features of the CSC phenotype, a role for claudin-2 in the regulation of these has not been identified. Here we report that elevated claudin-2 expression in stage II/III colorectal tumors is associated with poor recurrence-free survival following 5-FU-based chemotherapy, an outcome in which CSC play an instrumental role. In patient-derived organoids, primary cells, and cell lines, claudin-2 promoted CRC self-renewal in vitro and in multiple mouse xenograft models. Claudin-2 enhanced self-renewal of ALDHHigh CSC and increased their proportion in CRC cell populations, limiting their differentiation and promoting the phenotypic transition of non-CSC towards the ALDHHigh phenotype. Next-generation sequencing in ALDHHigh cells revealed that claudin-2 regulated expression of nine microRNAs known to control stem cell signaling. Among these, miR-222-3p was instrumental for the regulation of self-renewal by claudin-2, and enhancement of this self-renewal required activation of YAP, most likely upstream from miR-222-3p. Taken together, our results indicate that overexpression of claudin-2 promotes self-renewal within CRC stem-like cells, suggesting a potential role for this protein as a therapeutic target in CRC.