JAK3 and STAT3 genetic alteration as a treatment target in extranodal NK/T cell lymphoma, nasal type (NTCL)

Abstract

Introduction: Inhibition of the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway has been implicated as a treatment option for extranodal NK/T-cell lymphoma, nasal type (NTCL). However, JAK-STAT pathway alterations in NTCL are variable, and the efficacy of JAK-STAT pathway inhibition has been poorly evaluated. Materials and Methods: JAK3 mutation and STAT3 genetic alterations were investigated by direct sequencing and immunohistochemistry in 84 patients with newly diagnosed NTCL. Novel JAK3 mutations were functionally validated using Ba/F3 and NIH-3T3 cells with retrovirus vector systems. A JAK3 homology model was constructed. Cell viability assays were performed using JAK3 or STAT3 inhibitor in NTCL cells. Results: Five (7.0%) of 71 NTCL patients had JAK3 mutations in the pseudokinase domain: 2 JAK3A573V, 2 JAK3H583Y, and 1 JAK3G589D mutation. Ba/F3 cells transduced with novel JAK3 mutations (JAK3H583Y and JAK3G589D) grew independently without IL-3. NIH-3T3 cells transduced novel JAK3 mutations showed anchorage independent growth in soft agar plate. The transduced Ba/F3 cells were inhibited by the JAK3 inhibitor tofacitinib (mean IC50, 85 ± 10nM and 54 ± 9nM). Ribbon diagrams showed that these JAK3 pseudokinase domain mutations were located at the pseudokinase-kinase domain interface. Although phosphorylated STAT3 was overexpressed in 35 (51.4%) of 68 NTCL patients, STAT3 mutation (p.Tyr640Phe

STAT3Y640F) at the SRC homology 2 domain was detected in 1 (1.5%) of 63 patients. A STAT3 inhibitor was active against STAT3-mutant SNK-6 and YT cells. Conclusions: Novel JAK3-activating mutations are oncogenic and sensitive to a JAK3 inhibitor in NTCL. Although STAT3 mutation rate is low in NTCL patients, STAT3-mutant NTCL cells are sensitive to a STAT3 inhibitor. JAK3 or STAT3 signal was altered in NTCL and pathway inhibition might be a therapeutic option for patients with JAK3- or STAT3-mutant NTCL