Candida albicans promotes self-adhesion and tumor cell progression of colorectal cancer cells.
Candida albicans, a benign commensal yeast in the healthy gut, is increasingly being recognized as a tumor-promoting component of the gut mycobiome that is linked to worse patient outcomes in colorectal cancer (CRC). Emerging evidence suggests that in the tumor microenvironment, C. albicans drives tumor progression in its pathogenic hyphal form with the secretion of its peptide toxin, candidalysin, enhancing tumor cell evolution. CRC cells differentially express transglutaminase 2 (TG2), which mediates covalent binding to C. albicans and can promote tumor adaptability and metastases. However, mechanistic insight into how C. albicans infection leads to CRC progression is incomplete. CRC lines that express high (SW480) and low (LoVo, HCT 116) TG2 were infected with C. albicans and examined for effects on epithelial to mesenchymal transition (EMT) and cell migration. Parallel studies were also conducted using a candidalysin-deficient C. albicans strain. C. albicans invasion stimulated TG2 activity that allowed covalent crosslinking of the hyphae adhesin, Hwp1, to SW480 cells in a candidalysin-dependent manner. Independent of TG2 expression, infection of SW480, LoVo, and HCT 116 cells induced EMT-like changes including downregulation of E-cadherin, altered N-glycosylation of N-cadherin, and variable Snail1 expression. Infection increased MGAT5 activity, which raised levels of branched {beta}(1-6) N-glycans. Infection promoted CRC cell motility that was blocked by pharmacological inhibition of MGAT5. Thus, C. albicans engages CRC cells through separable mechanisms: a candidalysin-TG2-Hwp1 axis that may stabilize fungal attachment in TG2-high tumor cells, and a TG2-independent program of epithelial plasticity, altered N-glycosylation and migration-associated behavior that requires validation in vivo.