Tissue transglutaminase induces epithelial-mesenchymal-transition and the acquisition of stem cell like characteristics in colorectal cancer cells

Abstract

Human colon cancer cell lines (CRCs) RKO, SW480 and SW620 were investigated for TG2involvement in tumour advancement and aggression.TG2 expression correlated with tumouradvancement and expression of markers of epithelial-mesenchymal transition (EMT). Themetastatic cell line SW620 showed high TG2 expression compared to the primary tumourcell lines SW480 and RKO and could form tumour spheroids under non- adherent conditions.TG2 manipulation in the CRCs by shRNA or TG2 transduction confirmed the relationshipbetween TG2 and EMT. TGFβ1 expression in CRC cells, and its level in the cell medium andextracellular matrix was increased in primary tumour CRCs overexpressingTG2 and couldregulate TG2 expression and EMT by both canonical (RKO) and non-canonical (RKO andSW480) signalling. TGFβ1 regulation was not observed in the metastatic SW620 cell line, but TG2 knockdown or inhibition in SW620 reversed EMT. In SW620, TG2 expression andEMT was associated with increased presence of nuclear β-catenin which could be mediatedby association of TG2 with the Wnt signalling co-receptor LRP5. TG2 inhibition/knockdown increased interaction between β-catenin and ubiquitin shown by co-immunoprecipitation,suggesting that TG2 could be important in β-catenin regulation. β-Catenin and TG2 was alsoupregulated in SW620 spheroid cells enriched with cancer stem cell marker CD44 and TG2inhibition/knockdown reduced the spheroid forming potential of SW620 cells. Our datasuggests that TG2 could hold both prognostic and therapeutic significance in colon cancer.