[Large Granular Lymphocytic Leukemia and JAK/STAT Signaling Pathway--Review]

Large granular lymphocytic leukemia (LGLL) is a rare lymphoproliferative disorder of clonal expansion of cytotoxic T- or NK-cells in blood and bone marrow, and often associated with autoimmune disorders. According to the current WHO classification of the hematopoietic and lymphoid tissue tumors, the clonal LGL expansions are further classified as T-cell large granular lymphocytic leukemia (T-LGLL), chronic lymphoproliferative disorders of NK cells (CLPD-NK) and aggressive NK cell leukemia. Since there is a general lack of awareness of this disease, some patients may be misdiagnosed or some cases may be missed when diagnosis was done. At present, the pathogenesis of LGLL remains incomplete and unclear, and the therapeutic effects are unsatisfactory. For this reason, it is necessary to find prognostic marks and therapeutic targets of this disease. The constitutive activation of JAK/STAT pathway has been claimed to be involved in the development of LGLL. Recently, the somatic mutations in the SH2 domain of STAT3 in LGLL are frequently observed, which lead to the activation of JAK/STAT pathway. STAT3 is the first molecular markers that are highly specific for LGLL, and STAT3 mutations have been rarely detected in other tumor types studied, thus the STAT3 mutations can be used as molecular markers for LGLL diagnosis and can provide a novel therapeutic target for patients with LGLL.