CD8+ T cells from T-LGLL patients harboring STAT3Y640F mutation had the highest global DNA methylation levels (median = 1.44) compared to cells from T-LGLL patients without STAT3 mutations (median = 0.45) or from healthy controls (median = 0.365) (Fig. 4A). Here, STAT3 is linked to T-cell large granular lymphocyte leukemia.