Expression of sialyl-Tn sugar antigen in bladder cancer cells affects response to (BCG) and to oxidative damage.

The sialyl-Tn (sTn) antigen is an -linked carbohydrate chain aberrantly expressed in bladder cancer (BC), whose biosynthesis is mainly controlled by the sialyltransferase ST6GALNAC1. Treatment with (BCG) is the most effective adjuvant immunotherapy for superficial BC but one third of the patients fail to respond. A poorly understood correlation between the expression of sTn and BC patient's response to BCG was previously observed. By analyzing tumor tissues, we showed that patients with high ST6GALNAC1 and IL-6 mRNA expression were BCG responders. To investigate the role of sTn in BC cell biology and BCG response, we established the cell lines MCR and MCR by retroviral transduction of the BC cell line MCR with the cDNA or with an empty vector, respectively. Compared with MCR, BCG-stimulated MCR secreted higher levels of IL-6 and IL-8 and their secretome induced a stronger IL-6, IL-1β, and TNFα secretion by macrophages, suggesting the induction of a stronger inflammatory response. Transcriptomic analysis of MCR and MCR revealed that /sTn expression modulates hundreds of genes towards a putative more malignant phenotype and down-regulates several genes maintaining genomic stability. Consistently, MCR cells displayed higher HO sensitivity. In MCR,, BCG challenge induced an increased expression of several regulatory non coding RNA genes. These results indicate that the expression of /sTn improves the response to BCG therapy by inducing a stronger macrophage response and alters gene expression towards malignancy and genomic instability, increasing the sensitivity of BC cells to the oxidizing agents released by BCG.