Mutated JAK kinases and deregulated STAT activity are potential therapeutic targets in cutaneous T-cell lymphoma

Abstract

Mutated JAK kinases and deregulated STAT activity are potential therapeutic targets in cutaneous T-cell lymphomaThe malignant mechanisms that control the development of cutaneous T-cell lymphoma (CTCL) are starting to be identified. Recent evidence suggests that disturbances in specific intracellular signaling pathways, such as RAS-MAPK, TCR-PLCG1-NFAT and JAK-STAT, can play an essential role in the pathogenesis of CTCL.1,2 Our group previously reported a network of somatic mutations affecting genes with potential to affect critical Tcell signaling pathways in CTCL patients. 1 As part of our findings we detected a number of mutations potentially affecting JAK/STAT signaling. These findings were recently confirmed by an independent group, suggesting that mutations in this pathway may contribute as disease mechanisms in CTCL.3 Deregulated JAK/STAT signaling is involved in many types of cancer. In fact, somatically acquired genetic alterations of JAK or STAT genes that induce aberrant activation of downstream signaling, via STAT phosphorylation, have been reported in some human hematologic malignancies including T-cell lymphomas. 4,5 We decided to explore JAK/STAT signaling as part of an intricate network of malignant signaling that controls the pathogenesis of CTCL, on the basis of the following evidence: (i) we had detected mutations in the pseudokinase domain of JAK1 and JAK3 in two of 11 patients and one cell line; (ii) we had also found several mutations that can directly (i.e., IL6S/T) or indirectly (i.e., TRAF6, RELB and CARD11) activate JAK/STAT signaling; and (iii) activated STAT3 had been detected in a large proportion of patients with advanced CTCL. 6,7 To explore the mutational status of JAK genes in a larger cohort of human CTCL patients' samples and cell lines, two independent state-of-the-art ultrasequencing approaches were used: a targeted gene-enrichment kit (HaloPlex) coupled to Ion-PGM (Life Technologies) sequencing, and a specific polymerase chain reactionbased amplification protocol targeting the pseudokinase domains of JAK1, JAK2 and JAK3 genes (hereafter, referred to as PsTKd-PCR), followed by specific indexing and sequencing with MiSeq (Illumina; see the Online Supplementary Methods for details). These are two highly sensitive methods that can enable the detection of mutations even present at low frequencies in neoplastic cells or in minority clones which may be found in CTCL samples. Thus, taken together, the data from our series (including those already described by Vaqué et al. © F e r r a t a S t o r t i F o u n d a t i o nthe pseudokinase domain of JAK proteins, a finding that is consistent with the results of other research groups that have found somatic mutations in the same domain of JAK1 and JAK3 kinases in prolymphocytic leukemia, other T-cell leukemias including CTCL and various human malignancies. 3,4,[8][9][10] Thus, it has been shown that JAK pseudokinase domains are auto-inhibitory and keep the kinase domain inactive until receptor dimerization stimulates transition to an a...

Innovative Treatment Concepts for Cutaneous T-Cell Lymphoma Based on Microenvironment Modulation

“…Ruxolitinib inhibits JAK1/2 and tofacitinib inhibits JAK1/3, and both were shown to effectively inhibit downstream STAT activation leading to a marked proliferation arrest of CTCL cells in vitro [77]. Additionally, several in vitro and in vivo studies were able to demonstrate profound impairment of DC differentiation and function [78] and NK cell expansion and activation [79], as well as a reduced number of Tregs [80], thus causing complex immune modulation that might result in stronger antitumor activity.…”

“…Another substantial finding of recent whole genome sequencing studies in CTCL are recurrent mutations in the JAK/STAT pathway, leading to a stronger activation of genes regulating T-cell proliferation and differentiation [10,77]. Ruxolitinib inhibits JAK1/2 and tofacitinib inhibits JAK1/3, and both were shown to effectively inhibit downstream STAT activation leading to a marked proliferation arrest of CTCL cells in vitro [77].…”

Innovative Behandlungskonzepte mit Modulation der Mikroumgebung beim kutanen T-Zell-Lymphom

“…Eine weitere wichtige Entdeckung in den aktuellen CTCL- Genomsequenzierungsstudien sind wiederkehrende Mutationen im JAK/STAT-Signalweg und die dadurch ausgelöste verstärkte Aktivierung von Genen, die die Proliferation und Differenzierung von T-Lymphozyten steuern [10,77]. Ruxolitinib und Tofacitinib hemmen JAK1/2 bzw.…”

“…Ruxolitinib und Tofacitinib hemmen JAK1/2 bzw. JAK1/3, und für beide Wirkstoffe wurde nachgewiesen, dass sie in vitro effektiv die nachgelagerte STAT-Aktivierung inhibieren und so zu einer deutlichen Proliferationshemmung von CTCL-Zellen führen [77]. Darüber hinaus konnte in mehreren in vitro- und in-vivo-Studien nachgewiesen werden, dass die JAK-Inhibition die Differenzierung und Funktion von DZ [78] sowie die Expansion und Aktivierung von NK-Zellen [79] erheblich beeinträchtigt und die Anzahl der Treg reduziert [80] und somit eine komplexe Immunmodulation bewirkt, die in einer stärkeren antitumoralen Aktivität resultieren könnte.…”

Report from the II Melanoma Translational Meeting of the Spanish Melanoma Group (GEM)

“…To this end, Dr. Vaque's group designed specific cancer-type approaches, consisting of a combination of NGS techniques used alongside other tools commonly employed in diagnosis, such as, immunohistochemistry (IHC), and pre-clinical/clinical research (i.e., patient-derived xenograft in vivo models and a clinical trial respectively). For CTCL they identified important mechanisms of tumorigenesis and progression of CTCL regarding PLCG1-downstream signaling as activating mutations in PLCG1, NFKB (CARD11 and RELB) and JAK/STAT (38,39), as well as amplifications in PRKCQ (40). For MM they developed a targeted NGS approach (exons from 217 genes) that enabled the rapid detection (15 days) of important mechanisms of MM disease, as well as case-specific combinations of targeted inhibitors, tested ex vivo and in vivo, that proved to be more effective when used in appropriate mutational backgrounds (41).…”