Role of ST6GalNAc-I in immunosuppression and lung adenocarcinoma development

Tumors are prone to immune escape by developing strategies to evade immunity. ST6GalNAc-I is an O-glycosyltransferase, which catalyzes the addition of sialic acid onto the first sugar GalNAc (Tn) and results in the formation of Neu5Acα2, 6GalNAc (STn) carbohydrate antigen. SialylTn plays an important role in tumor progression, angiogenesis, and metastasis. RNA sequence analysis was performed using genetically engineered LUAD mouse model tumors (KrasG12D/+; Trp53R172H/+; Ad-Cre (KPA) and KrasG12D/+; Ad-Cre (KA)). We have performed RNA sequence analysis using KPA tumors (N=3), KA tumors (N=3), and littermate control lung tissues (N=3). In comparison to normal lung tissues, several genes were significantly overexpressed in KPA and KA-derived LUAD tumors, including Meg3, Slc7a5, Cxcr1, Awat1, Kng2, Gjb3, Mfi2, and Dlk1. More specifically, St6galnac-I was significantly overexpressed in aggressive-type KPA tumor tissues compared to KA and normal lung tissues. Expression of ST6GalNAc-I is associated with tumor progression and angiogenesis by immunosuppression. Mechanistically, ST6GalNAc-I promotes tumor cell sialylation that impacts tumor angiogenesis by altering mucin MUC5AC. Similarly, ST6GalNAc-I regulates Nectin2 sialylation which leads to immunosuppression and tumor progression. Overall, our study defined that ST6GalNAc-I is a critical molecule for tumor cell sialylation for disease aggressiveness.