STAT3 and STAT5B Mutations in T/NK-Cell Chronic Lymphoproliferative Disorders of Large Granular Lymphocytes (LGL): Association with Disease Features

Abstract

STAT3 and STAT5B (STAT3/STAT5B) mutations are the most common mutations in T-cell large granular lymphocytic leukemia (T-LGLL) and chronic lymphoproliferative disorders of NK cells (CLPD-NK), but their clinical impact remains unknown. We investigated the frequency and type of STAT3/STAT5B mutations in FACS-sorted populations of expanded T/NK-LGL from 100 (82 clonal; 6 oligoclonal; 12 polyclonal) patients, and its relationship with disease features. Seventeen non-LGL T-CLPD patients and 628 age-matched healthy donors were analyzed as controls. STAT3 (n = 30) and STAT5B (n = 1) mutations were detected in 28/82 clonal T/NK-LGLL patients (34%), while absent (0/18, 0%) among oligoclonal/polyclonal LGL-lymphocytosis. Mutations were found across all diagnostic subgroups: TCD8+-LGLL, 36%; CLPD-NK, 38%; TCD4+-LGLL, 7%; Tαβ+DP-LGLL, 100%; Tαβ+DN-LGLL, 50%; Tγδ+-LGLL, 44%. STAT3-mutated T-LGLL/CLPD-NK showed overall reduced (p < 0.05) blood counts of most normal leukocyte subsets, with a higher rate (vs. nonmutated LGLL) of neutropenia (p = 0.04), severe neutropenia (p = 0.02), and cases requiring treatment (p = 0.0001), together with a shorter time-to-therapy (p = 0.0001), particularly in non-Y640F STAT3-mutated patients. These findings confirm and extend on previous observations about the high prevalence of STAT3 mutations across different subtypes of LGLL, and its association with a more marked decrease of all major blood-cell subsets and a shortened time-to-therapy.

Anti-TRBC1 Antibody-Based Flow Cytometric Detection of T-Cell Clonality: Standardization of Sample Preparation and Diagnostic Implementation

“…Although final diagnosis at the referring center was inconclusive in the first case (case #1), the presence of a clearly aberrant (CD2 lo ) Tαβ effector cell population associated with chronic neutropenia would strongly support the diagnosis of T-LGLL [33], in line with monotypic expression of TRBC1. In one of the remaining two discrepant cases (case #3), an expansion of LGL with a normal Tαβ-effector cell phenotype (CD2 + CD7 lo CD27 − CD28 − CD45RA −/+ cytoplasmic granzyme + ) [33], but an elevated TRBC1 + /TRBC1 − ratio compared to normal/reactive polyclonal TαβCD8 + cells was observed in the absence of clonality by PCR. In this case, the possibility that the altered TRBC1 + /TRBC1 − ratio might be due to an increased number of (activated-oligoclonal) senescent effector memory/terminal effector TαβCD8 + cells [14,15] could not be ruled out, since similarly increased TRBC1 + /TRBC1 − ratios were observed in normal and reactive blood when analysis was restricted to normal effector memory/terminal effector TαβCD8 + cells.…”

“…More detailed investigation of such discrepant cases showed that in three of five patients (cases #1, #2 and #4), final diagnosis was concordant with the TRBC1-based FCM assay results, with failure of PCR in two of three cases (cases #1 and #2) to detect T-cell clonality being due to the analysis of whole blood DNA instead of the FACS-sorted (suspicious) cell population DNA, in samples where the percentage of clonal cells in PB was below the sensitivity limit of the molecular technique [15][16][17]. Although final diagnosis at the referring center was inconclusive in the first case (case #1), the presence of a clearly aberrant (CD2 lo ) Tαβ effector cell population associated with chronic neutropenia would strongly support the diagnosis of T-LGLL [33], in line with monotypic expression of TRBC1. In one of the remaining two discrepant cases (case #3), an expansion of LGL with a normal Tαβ-effector cell phenotype (CD2 + CD7 lo CD27 − CD28 − CD45RA −/+ cytoplasmic granzyme + ) [33], but an elevated TRBC1 + /TRBC1 − ratio compared to normal/reactive polyclonal TαβCD8 + cells was observed in the absence of clonality by PCR.…”

Clinicobiological Characteristics and Outcomes of Patients with T-Cell Large Granular Lymphocytic Leukemia and Chronic Lymphoproliferative Disorder of Natural Killer Cells from a Single Institution

“…There was heterogeneity in the immunophenotype in the group of T-LGLL, with the most common profile being CD8 + CD4 − CD57 + and CD4 + CD8 − or CD8 +/− less common, as previously described [19][20][21]. It is becoming apparent that these two immunological subgroups are indeed clinically and biologically distinct.…”

Large Granular Lymphocytic Leukemia: From Immunopathogenesis to Treatment of Refractory Disease

“…Canonical STAT3 variants (Y640F, D661V, D661Y, N647I) have been identified in 40% of LGLL patients, whereas STAT5b variants (Y665F, N642H) are prevalent in specific disease subtypes as they were recently reported in up to 19% of TCRγδ LGLL and up to 55% of CD4 + LGLL cases [10,19,20]. The finding of constitutive activation of JAK/STAT signaling and the frequency of STATs mutations point towards a pivotal role of this pathway in LGLL pathogenesis, possibly indicating scenarios for the treatment of this disorder with JAK inhibitors [1,9,[21][22][23]. The JAK/STAT pathway is involved in a multitude of molecular functions, including transduction of signals conveyed by cytokine receptors such as growth hormone, erythropoietin, and interleukin-6 receptors [24].…”