Impact of sialyltransferase deletion in mature T cells on control of subcutaneous and metastatic cancers.

To investigate the roles of the α2,3-sialyltransferase ST3Gal1 and the α2,6-sialyltransferase ST6Gal1 in T cell-mediated tumor control, we generated mice with mature T cell-specific deletion of ST3Gal1 (T-ST3KO) or ST6Gal1 (T-ST6KO) using distal Lck-Cre-mediated recombination. Deletion of ST3Gal1 in mature T cells did not affect thymic T cell development but resulted in a reduction of peripheral CD8+ T cells. In contrast, ST6Gal1 deletion had minimal impact on T cell development and peripheral T cell abundance. Following in vitro stimulation of isolated T cells from T-ST3KO and parental wild type (WT) mice with anti-CD3 plus anti-CD28/CD80-Fc, CD8+ T cells from T-ST3KO mice exhibited enhanced activation and an increased frequency of CD44 positive memory-like T cells, while comparison of T cells from T-ST6KO and the parental WT mice showed no significant changes. Despite the activated CD8+ T cell phenotype in T-ST3KO mice, subcutaneous MC38 tumors displayed accelerated growth. In contrast, tumor progression in T-ST6KO mice was unchanged from the parental WT mice. Notably, T-ST6KO mice developed increased pulmonary metastases following intravenous challenge with B16F10 melanoma cells, whereas metastatic burden was unaffected in T-ST3KO mice. These findings demonstrate distinct and non-redundant roles for ST3Gal1- and ST6Gal1-mediated sialylation in regulating T cell function and antitumor immunity and reveal context-dependent effects of T cell intrinsic sialylation in controlling primary tumor growth and metastatic dissemination.