STAT3 and T-cell large granular lymphocyte leukemia: Furthermore, it has previously been shown that STAT3 GOF mutations cause DNA hypermethylation, resulting in high sensitivity towards azacytidine in large granular lymphocyte leukemia (LGLL) [56], which could contribute to the potency of hypomethylating agents in a disease characterized by JAK/STAT activation such as T-PLL.