Altered O-glycosylation is associated with inherent radioresistance and malignancy of human laryngeal carcinoma

Radioresistance (inherent or acquired) remains a major obstacle affecting the clinical outcome of radiotherapy for laryngeal carcinoma. Results from our laboratory and other groups suggest that aberrant glycosylation contributes to cancer acquired radioresistance. However, the role of glycosylation in inherent radioresistance of laryngeal carcinoma has not been fully uncovered. In this study, we investigated the glycan profiling of the inherent radioresistant (Hep-2max) and radiosensitive (Hep-2 min) cell lines using lectin microarray analysis. The results revealed that the radioresistant cell line Hep-2max presented higher core 1-type O-glycans than the sensitive one. Further analysis of the O-glycan regulation by benzyl-alpha-GalNAc application in Hep-2max cells showed partial inhibition of the O-glycan biosynthesis and increased radiosensitivity. In addition, core 1 beta 1, 3-galactosyltransferase (C1GALT1) overexpression in Hep-2 min cells enhanced cell migration, invasion, and radioresistance. Conversely, knockdown of ClGALT1 in Hep-2max cells was able to suppress these malignant phenotypes. Moreover, mechanistic investigations showed that ClGALT1 modified the O-glycans on integrin beta 1 and regulated its activity. The glycosylation-mediated radioresistance was further inhibited by anti-integrin beta 1 blocking antibody. Importantly, we also observed that core 1-type O-glycans expression was correlated with advanced tumor stage, metastasis, and poor survival of laryngeal carcinoma patients. These findings suggest that altered O-glycosylation can lead to the inherent radioresistance and progression, and therefore may be important for enhancing the efficacy of radiotherapy in laryngeal carcinoma.