Tec Kinase Research Articles

Abstract C087: Distinct gene expression and DNA methylation pattern associated with poor outcome of B-cell acute lymphoblastic leukemia in Hispanic/Latino children

Abstract The risk of developing Acute Lymphoblastic Leukemia (B-ALL) in Hispanic/Latino (HL) children is 1.2-1.75 greater that Non-Hispanic whites (NHW) and after correcting for socioeconomic factors, mortality is 40% higher in HL children. H/L children have a higher incidence of high-risk genetic variations: a 2-fold greater rate of IKZF1 deletion (IKZF1-del) and a 4-fold greater rate of CRLF2 translocations. IKZF1-del is associated with chemotherapy resistance and CRLF2 translocations represent Ph-like status. These two genetic alterations are concomitant in H/L children. 94% of H/L patients with CRLF2 translocation had a coexisting IKZF1-del. Despite evidence of specific genomic alterations in B-ALL in H/L children, potential differences in gene expression in B-ALL from H/L vs. NHW children has not been studied. Here, we used transcriptomic and genomic approach to determine the role of specific mutations and genetic background in regulation of gene expression in B-ALL from H/L and NHW children and to gain insight into molecular mechanisms that regulate cellular proliferation and chemotherapy resistance. RNA-seq was performed on B-ALL from 42 H/L and 18 NHW children and differential gene expression patterns were compared between the two ethnic groups. Gene set enrichment analysis (GSEA), Gene ontology (GO), and Ingenuity pathway analysis (IPA) were performed. In addition, we performed separate analysis and compared both ethnic groups with wild-type status of IKZF1 (IKZF1-WT). We performed DNA methylation signature analysis using reduced representation bisulfite sequencing on 8 H/L and 8 NHW B-ALL samples. Results showed increased expression of the genes that regulate Immune and inflammatory response, interferon signaling, and JAK/STAT pathway in H/L compared to NHW B-ALL cells. These expression changes were more pronounced in IKZF1-del B-All cells. In contrast, H/L B-ALL cells have reduced expression of the genes that regulate genome stability, cell cycle checkpoint signaling, and specific amino acid synthesis pathways. IPA showed upregulated interferon, Tec Kinase, and CDK5 signaling in B-ALL cells of H/L compared to NHW children. Compared. DNA Methylation analysis showed distinct patterns associated with altered expression of several oncogenes in B-ALL from H/L, compared to NHW children. In conclusion, H/L B-ALL has a distinct expression of the genes that regulate signaling pathways that promote cellular proliferation and chemotherapy resistance that are different from B-ALL in NHW children. Results identified therapeutic targets and tumor vulnerabilities that can be used for precision medicine approach to reduce disparities in B-ALL outcome in H/L children. Citation Format: Sinisa Dovat, Joseph Schramm, Daniel Bogush, Dhimant Desai, Bing He, Dhimant Desai, Arati Sharma. Distinct gene expression and DNA methylation pattern associated with poor outcome of B-cell acute lymphoblastic leukemia in Hispanic/Latino children [abstract]. In: Proceedings of the 17th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2024 Sep 21-24; Los Angeles, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2024;33(9 Suppl):Abstract nr C087.

Iguratimod suppresses plasma cell differentiation and ameliorates experimental Sjögren's syndrome in mice by promoting TEC kinase degradation.

Primary Sjögren's syndrome (pSS) is a chronic inflammatory autoimmune disease with an unclear pathogenesis, and there is currently no approved drug for the treatment of this disease. Iguratimod, as a novel clinical anti-rheumatic drug in China and Japan, has shown remarkable efficacy in improving the symptoms of patients with pSS in clinical studies. In this study we investigated the mechanisms underlying the therapeutic effect of iguratimod in the treatment of pSS. Experimental Sjögren's syndrome (ESS) model was established in female mice by immunizing with salivary gland protein. After immunization, ESS mice were orally treated with iguratimod (10, 30, 100 mg·kg-1·d-1) or hydroxychloroquine (50 mg·kg-1·d-1) for 70 days. We showed that iguratimod administration dose-dependently increased saliva secretion, and ameliorated ESS development by predominantly inhibiting B cells activation and plasma cell differentiation. Iguratimod (30 and 100 mg·kg-1·d-1) was more effective than hydroxychloroquine (50 mg·kg-1·d-1). When the potential target of iguratimod was searched, we found that iguratimod bound to TEC kinase and promoted its degradation through the autophagy-lysosome pathway in BAFF-activated B cells, thereby directly inhibiting TEC-regulated B cells function, suggesting that the action mode of iguratimod on TEC was different from that of conventional kinase inhibitors. In addition, we found a crucial role of TEC overexpression in plasma cells of patients with pSS. Together, we demonstrate that iguratimod effectively ameliorates ESS via its unique suppression of TEC function, which will be helpful for its clinical application. Targeting TEC kinase, a new regulatory factor for B cells, may be a promising therapeutic option.

Uncovering key steps in FGF12 cellular release reveals a common mechanism for unconventional FGF protein secretion

FGF12 belongs to a subfamily of FGF proteins called FGF homologous factors (FHFs), which until recently were thought to be non-signaling intracellular proteins. Our recent studies have shown that although they lack a conventional signal peptide for secretion, they can reach the extracellular space, especially under stress conditions. Here, we unraveled that the long “a” isoform of FGF12 is secreted in a pathway involving the A1 subunit of Na(+)/K(+) ATPase (ATP1A1), Tec kinase and lipids such as phosphatidylinositol and phosphatidylserine. Further, we showed that the short “b” isoform of FGF12, which binds ATP1A1 and phosphatidylserine less efficiently, is not secreted from cells. We also indicated regions in the FGF12a protein sequence that are crucial for its secretion, including N-terminal fragment and specific residues, and proposed that liquid-liquid phase separation may be important in this process. Our results strongly suggest that the mechanism of this process is very similar for all unconventionally secreted FGF proteins.

Abstract 2846: Investigation of mechanisms that result in health disparity for Hispanic/Latino patients with B acute lymphoblastic leukemia

Abstract Although social determinants of health have a large impact on health disparity, biologic vulnerabilities - particularly in cancers that impact at-risk populations are important. Amongst children with Acute Lymphoblastic Leukemia (ALL), the Hispanic/Latino (H/L) population is vulnerable given since the risk of developing ALL is 1.2-1.75 that of Non-Hispanic White children. After corrections for socioeconomic impacts, the mortality for H/L children is 40% higher than NHW. H/L children have a higher rate of high-risk genetic variations: 2-fold rate of heterozygous IKZF1 deletion (IKZF1-del) and a 4-fold rate of CRLF2 translocation. IKZF1 deletion and CRLF2 translocations are associated increased risk of relapse and chemotherapy resistance in B ALL. IKZF1 is an important transcriptional factor and epigenetic regulator that affects global gene transcription in hematopoietic cells. Simultaneous IKZF1-del and CRLF2 translocation represented 94% of H/L children with CRLF2 translocation. Although only 49% of all H/L patients with IKZF1-del had a CRLF2 translocation. Transcriptomics were analyzed for 42 H/L and 18 NHW patient samples using RNAseq. Gene expression from H/L patients was compared to expression in NHW patients and differentially expressed genes were analyzed. Gene set enrichment analysis (GSEA) revealed downregulation of processes responsible for genome maintenance including DNA replication, DNA templated transcription elongation, double strand break repair, and recombinational repair. Ingenuity pathway analysis (IPA) revealed upregulated pathways in stress related translation, histone deacetylases, interferon, and FLT3 signaling compared to NWH. H/L specimens resulted in decreased expression for FGF pathways, ceramide, and FAK signaling. We performed the same analysis in H/L and NHW with wildtype IKZF1 to compare these two population without high risk structural variants. GSEA analysis showed downregulated Intra S DNA Damage checkpoint signaling, DNA replication checkpoint signaling, glutamine amino acid synthesis, and aspartate amino acid synthesis. IPA showed upregulated interferon, histone deacetylases, TREM1 signaling, and Tec Kinase signaling. IPA showed downregulated Ephrin and CDK5 signaling. DNA methylation patterns were compared between 8 H/L and 8 NWH B ALL samples which showed differential methylation patterns affecting multiple cancer relevant genes.In conclusion, these data represent biologic vulnerability in H/L patients with B ALL in comparison to NWH regardless of high-risk genetic variants. H/L B-ALL shows deregulated maintenance of the genome via replication and repair pathways as well as potential vulnerabilities related to regulation of glutamate/aspartate synthesis. These findings give insight into potential mechanisms that can explain increased frequency of high-risk genetic variants in H/L B ALL. Citation Format: Joseph W. Schramm, Bing He, Yali Ding, Chingakham Singh, Daniel Bogush, Katarina Dovat, Diwakar Bastihalli Tukaramrao, Riya Bhalodia, Sinisa Dovat. Investigation of mechanisms that result in health disparity for Hispanic/Latino patients with B acute lymphoblastic leukemia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2846.

Differential Protein Expression between the Motor and Sensory Fascicles in Rat Femoral Nerve Injury.

It is important to distinguish between motor and sensory fascicles of the peripheral nerves for nerve alignment in surgery. However, there are no biomarkers currently available for effective identification of motor or sensory fascicles. The objective of this study was to identify differentially expressed proteins between motor and sensory fascicles of rats in response to injury. The study was carried out using a rat femoral nerve injury model. A proteomic analysis was performed to detect differential protein expression using samples of bilateral motor and sensory branches of intact and injured rat femoral nerves through fluorescent two-dimensional difference gel electrophoresis and matrix-assisted laser desorption ionization-time of flight mass spectrometry. Chi-square tests and t-tests were performed for comparison between motor or sensory nerve groups. The data identified six proteins that were differentially expressed between motor and sensory fascicles (>1.5-fold, P < 0.05), including apolipoprotein E, neurofilament light polypepticle, TEC kinase, serine protease inhibitor A3N, peroxiredoxin-2, and TPM1. The proteomic results were consistent with the mRNA expression levels of these genes as determined by quantitative reverse transcription polymerase chain reaction. Our study suggests that these proteins may play roles in nerve regeneration and repair. Importantly, apolipoprotein E and Serpina3n may serve as specific biomarkers for distinguishing motor and sensory fascicles of the peripheral nerves for nerve alignment in surgery.

Ritlecitinib (Litfulo) for severe alopecia areata.

The FDA has approved ritlecitinib (Litfulo – Pfizer), an oral JAK and TEC kinase family inhibitor, for treatment of severe alopecia areata in patients ≥12 years old. Ritlecitinib is the second oral drug to be approved in the US for treatment of severe alopecia areata; baricitinib (Olumiant), a JAK inhibitor, is approved only for use in adults.

Combinatorial inhibition of Tec kinases BTK and ITK is beneficial in ameliorating murine sclerodermatous chronic graft versus host disease.

Graft-versus-host disease (GVHD) is the major factor limiting the widespread use of potentially curative allogeneic hematopoietic stem cell transplant (allo-HSCT). Chronic GVHD is characterized by the activation of alloreactive donor immune cells, especially B- and T-cells, leading to tissue damage and pathogenic fibrosis. In this study, we used highly specific next-generation inhibitors of ITK (PCYC-274), BTK (PCYC-804), and ibrutinib-like BTK/ITK inhibitors (PCYC-914 and PCYC-401) in the B10.D2 → BALB/C model of murine sclerodermatous cGVHD. From the third week onward, allogeneic recipients in each group of respective Tec kinase inhibitors were treated three times weekly with inhibitors at doses of 10 and 30 mg/kg or with saline control via oral gavage. Overall, we found that selective BTK inhibition was less effective than combined ITK/BTK or ITK inhibition in lengthening survival and reducing symptoms of cGVHD. ITK inhibition was most efficacious, with PCYC-274 and PCYC-401 demonstrating a nearly 50 percent reduction in GVHD scoring even at the 10 mg/kg dose, while 30 mg/kg of these compounds almost completely ameliorated GVHD symptomology. BTK/ITK and ITK-treated mice showed significant reductions in overall pathology. Significant reductions in dermal thickness and fibrosis were shown for all treatment groups. There was evidence of mixed Th1 and Th2 cytokine profiles in the skin of mice with dermal cGVHD, as both IFN-gamma and IL-4 were upregulated in the allogeneic control group, while kinase inhibition significantly reduced levels of these cytokines. Using an in vitro model of T-cell polarization, Th1 cell production of TNF-alpha and IFN-gamma were partially blocked by ITK. Th2 cell production of IL-4 was almost completely blocked synergistically by ITK and BTK inhibition. BTK-specific inhibition was unable to block either Th1 or Th2 cytokine production. Taken together, these results confirm previous reports that ITK-focused inhibition inhibits Th1 and Th2 cells. Additionally, the compound's effects on T-cell proliferation were tested by CFSE assay. Pure ITK inhibition was most effective at blocking T-cell proliferation, with no proliferation in PCYC-274-treated cells even at 0.1uM. PCYC-401 and PCYC-914 showed some inhibition at lower doses, with complete inhibition evident at 10uM. PCYC-804 was only partially able to block proliferation even at 10uM. In conclusion, we observed substantial benefit for differential inhibition of Tec kinases in GVHD, with ITK being most efficacious and Th1 cells being more resistant to inhibition, matching the previously reported findings of a Th2 to Th1 selective pressure in cells treated with ibrutinib. Our data warrants the further development of ITK and ITK/BTK inhibitors with specific inhibitory ratios to improve the treatment of GVHD and other T-cell mediated diseases.

IL-2 rescues impaired T cell function upon loss of Itk via metabolic reprogramming

Abstract IL-2 inducible T cell kinase (Itk) is a critical component of T cell receptor (TCR) signaling required for activation of PLCg and downstream transcription factors, that regulate expression of effector molecules. Loss of Itk impairs T-cell activation by modulating the strength of TCR signal. Itk −/−mice have defects in T cell development with decreased proliferation and impaired differentiation to multiple CD4 T helper lineages. Most severe defects are seen in differentiation of Th9 cells, which produce the cytokine, IL-9. Under Th9 differentiation conditions, Itk −/−cells initially appear similar to WT cells but at 72hrs fail to sustain long-term expression of effector molecules. Th9 differentiation could be rescued by inclusion of IL-2. Itk −/−CD4 T cells show decreased mTORC1 signaling and do not maintain expression of IRF4, c-Myc, pRb and multiple nutrient transporters, including the Glucose transporter 1 (GLUT1), transferrin receptor (CD71), and amino acid co-transporter (CD98), all of which were rescued by IL-2. IL-2 is not required initially but can be added as late as 48hrs into culture. Using SCENITH—a flow cytometry-based technique that profiles metabolism—we found that WT differentiated Th9 cells were primarily glycolytic. In contrast, Itk −/−Th9 cells were less synthetic and more dependent on mitochondrial respiration. Inclusion of IL-2 in Itk −/−cultures rescued metabolic profiles, comparable to WT cells. Our results suggest that metabolic flexibility is central to dictating the functional/effector fate of CD4 T cells and that the Tec kinase Itk and IL-2-mediated pathways are required for maintenance of metabolic integrity, providing novel insight into mechanisms by which IL-2 can rescue T cell functional defects. This work was supported by the Intramural Research Program of NIAID, NIH.

Abstract 1813: Selective ITK blockade induces antitumor responses and enhances efficacy to immune checkpoint inhibitors in preclinical models

Abstract Interleukin 2 inducible T cell kinase (ITK) plays a role in both T cell receptor (TCR) signaling and T helper cell differentiation. ITK-/- mice exhibit defects in Th2 differentiation while retaining the ability to differentiate into Th1 cells that secrete IFNγ. We generated CPI-818, a covalent inhibitor of ITK (KD 2.5nM) with &amp;gt; 100 fold selectivity over resting lymphocyte kinase (RLK) and other TEC family kinases. This drug is now being evaluated as a single agent in an ongoing Phase 1 clinical trial in refractory T cell lymphoma where objective tumor responses have been observed. In the studies reported here, we have investigated the immunomodulatory effects of specific ITK blockade of human T cells with CPI-818 in vitro and in vivo in murine tumor models. Analysis of the cytokine profiles in human CD4 T cells differentiated under non-polarizing, Th1 or Th2 polarizing conditions showed that CPI-818 inhibited generation of Th2-associated cytokines whereas, production of Th1 cytokines such as IFNγ were largely unaffected. Suppression of IL-2-mediated proliferative response occurred only at high concentrations of CPI-818 (&amp;gt;1uM). The effect of CPI-818 on anti-tumor immunity was evaluated in both murine syngeneic CT26 colon cancer and EL4 T cell lymphoma models. In vivo treatment of animals with established tumors showed single-agent anti-tumor activity in both models. Combining CPI-818 with suboptimal doses of anti-PD1 and anti-CTLA4 synergistically inhibited the growth of established CT26 tumors, leading to complete tumor elimination in 100% treated animals. Furthermore, triple combination therapy elicited durable anti-tumor immune memory after animals were rechallenged with a new engraftment of CT26 cells. Enhancement of anti-tumor activity required CD8+ T cells as in vivo antibody-mediated depletion of CD8, but not CD4, abolished the efficacy of CPI-818 monotherapy. Consistent with that, we found increased tumor-infiltrating CD8+ T cells and increased ratio of CD8: Treg in the responding tumors of CPI-818 treated animals. Levels of several exhaustion makers were down-regulated by treatment with CPI-818, suggesting that inhibition of ITK by CPI-818 produces favorable changes in the tumor microenvironment. Our findings provide insights into the effects of selective ITK blockade on tumor immunity and its potential role in immunotherapy. Citation Format: Lih-Yun Hsu, Rahul D. Pawar, Dan Li, Poorva Ghosh, Kevin Nguyen, Carlene Williams, Yuqin Song, Ning Ding, Erik Verner, Richard A. Miller. Selective ITK blockade induces antitumor responses and enhances efficacy to immune checkpoint inhibitors in preclinical models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1813.

Abstract 1770: CD28-Y218 phosphorylation in CAR-T cells is mediated by the IL-2-inducible T-cell kinase (ITK)

Abstract CD28-derived co-stimulation modules are frequently used as part of the signaling domain of chimeric antigen receptors (CAR). These modules contain well characterized tyrosine-containing moieties (YMNM and PYAP) that become phosphorylated upon CAR activation, and result in IL-2 secretion and T cell expansion. Previous work by our group has shown that an additional tyrosine residue, located in the C-terminus of CD28 (Y218), was also phosphorylated upon CAR activation. The kinase responsible for this phosphorylation remains unknown, but in silico studies point towards the IL-2-inducible T-cell kinase (ITK), the protein-tyrosine kinase TEC and the bone marrow tyrosine kinase (BMX). In this work we sought to elucidate the molecular mechanism and functional relevance of CD28-Y218 phosphorylation in CAR-T cells.To analyze the kinetics of Y218 phosphorylation, prostate stem cell antigen (PSCA)-specific second-generation CAR-T cells were stimulated through co-culture with HPAC pancreatic cancer cells for 0, 1, 10, 30 and 60 minutes. Phosphorylation of CD28 Y218, Zap70, PLCγ and Vav1 was analyzed by Western blotting. To determine the role of ITK in CD28-218 phosphorylation: 1) PSCA-specific CAR-T cells were treated with ITK inhibitors 10 μM (BMS-509744 or Ibrutinib) for 24h and 2) ITK-deficient Jurkat cells expressing a PSCA-specific CAR were cocultured with HPAC cells for 0 or 10 min. To determine the functional relevance of this phosphorylation event, we generated mutant CARs where the tyrosine residue was replaced with a non-phosphorylatable amino acid (Y218F) and evaluated its effects in vivo and in vitro. CAR-T cell cytotoxicity was monitored using the xCELLigence Real Time Cytotoxicity Assay (RTCA) and cytokine production was assessed following overnight co-culture with target cells using the ELLA system (Biotechne, CA, USA). To evaluate the in vivo antitumor efficacy of PSCA-specific CAR-T cells, NSG mice were injected (s.c.) with 1 HPAC cells and infused 14 days later with 5 CAR-T cells (i.v.). Tumor growth was monitored for 35 days.Our results show that phosphorylation of CD28-Y218 occurs after the phosphorylation of early TCR signaling mediators, reaching maximum levels around 10-30 min post-stimulation. Pharmacological inhibition and genomic ablation of ITK impairs CD28-Y218 phosphorylation, suggesting an essential role of ITK in this signaling event. We observed that mutation of the Y218 residue did not affect CAR expression, in vitro cytotoxicity, or INFγ production. However, this mutation was associated with reduced IL-2 and TNFα secretion. In vivo, this mutation completely abrogated the therapeutic effect of CAR-T cells in a pancreatic cancer model. In conclusion, these results indicate that ITK is required for CD28-Y218 phosphorylation, a signaling event that plays an important role in CAR-T cell function, with direct impact on IL-2 secretion and antitumor efficacy. Citation Format: Elena Martinez-Planes, Miguel G. Fontela, Cecilia Ramello, Daniel Abate-Daga. CD28-Y218 phosphorylation in CAR-T cells is mediated by the IL-2-inducible T-cell kinase (ITK) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1770.

Degrading the signal amplifier: ITK as a target for targeted protein degradation

In this issue of Cell Chemical Biology, Jiang and colleagues show for the first time that the Tec kinase ITK can be targeted using PROTAC approaches. This new modality has implications for the treatment of Tcell lymphomas, but also potentially for the treatment of Tcell-mediated inflammatory diseases, that depend on ITK signaling.

627MO Orelabrutinib plus RCHOP for previously untreated non-germinal center b cell-like (GCB) diffuse large b cell lymphoma (DLBCL) patients with extranodal disease

The prognosis of patients with non-GCB DLBCL is poor, especially in those with extranodal invasion which has strong invasiveness and rapid clinical progress. How to improve the prognosis of these patients is the main challenge of DLBCL therapy. Bruton tyrosine kinase (BTK) is a member of the non-receptor tyrosine kinase Tec family; it is involved in the proliferation, adhesion and metastasis of B cells. BTK inhibitor showed activity in relapsed/refractory non-GCB DLBCL. Orelabrutinib is a new oral covalent BTK inhibitor; this study aimed to analyze the efficacy and safety of orelabrutinib plus RCHOP for previously untreated non-GCB DLBCL patients with extranodal disease.

Epigenetic regulation of inflammatory genes involving histone methylation is associated with hyperimmune response in COVID-19 patients

Abstract One of the leading causes of the severe COVID-19 disease symptoms is the production of massive amounts of pro-inflammatory cytokines. Although the precise mechanisms that trigger such hyperimmune response is unclear, epigenetic mechanisms are known to play important roles in the regulation of cytokine production and inflammation. In this study we examined global gene expression and histone methylation profile in the PBMCs of hospitalized COVID-19 patients. Despite individual variations, the expressions of many inflammation-related genes such as Arginase 1 (ARG1) and IL1 receptor 2 (IL1R2) were significantly upregulated in COVID-19 patients. We also found the expressions of coagulation-related genes, VWF and Protein S, were altered in COVID-19 patients. The expression patterns of some genes such as IL1R2 correlated with their histone methylation marks. Pathway analysis revealed that most of these dysregulated genes were in the TGFb, IL1b, IL6 and IL17 pathway. Interestingly, we found that the majority of those altered genes were in the dexamethasone targeting pathway. We also found that the expression of BMX, a member of TEC family kinases, was significantly increased in the PBMCs of COVID-19 patient at both RNA level and protein level. Interestingly, some TEC kinase inhibitors have been used to treat COVID-19 patients in clinical trials. Overall, this study has identified genes in PBMCs of COVID-19 patients with altered histone mark and gene expression profile, providing important information towards identifying potential biomarkers and therapeutic targets for COVID-19 disease. (Supported by NIH grants P01AT003961, P20GM103641, R01AT006888, R01ES030144, R01AI129788 and R01AI123947 to P.S.N and M.N.) Supported by NIH grants P01AT003961, P20GM103641, R01AT006888, R01ES030144, R01AI129788 and R01AI123947 to P.S.N and M.N.

A Role for Liquid-Ordered Plasma Membrane Nanodomains Coordinating the Unconventional Secretory Pathway of Fibroblast Growth Factor 2?

Fibroblast growth factor 2 (FGF2) is a tumor cell survival factor that belongs to a subgroup of extracellular proteins lacking N-terminal signal peptides. Whereas this phenomenon was already recognized in the early 1990s, detailed insights into the molecular mechanisms underlying alternative pathways of protein secretion from eukaryotic cells were obtained only recently. Today, we know about a number of alternative secretory mechanisms, collectively termed unconventional protein secretion (UPS). FGF2 belongs to a subgroup of cargo proteins secreted by direct translocation across the plasma membrane. This feature has been classified as type I UPS and is shared with other unconventionally secreted proteins, such as HIV-Tat and Tau. FGF2 translocation across the membrane is initiated through sequential interactions with the Na,K-ATPase, Tec kinase, and phosphoinositide PI(4,5)P2 at the inner plasma membrane leaflet. Whereas the first two are auxiliary factors of this pathway, the interaction of FGF2 with PI(4,5)P2 triggers the core mechanism of FGF2 membrane translocation. It is based on a lipidic membrane pore that is formed by PI(4,5)P2-induced oligomerization of FGF2. Membrane-inserted FGF2 oligomers are recognized as translocation intermediates that are resolved at the outer plasma membrane leaflet by glypican-1, a heparan sulfate proteoglycan that captures and disassembles FGF2 oligomers on cell surfaces. Here, we discuss recent findings suggesting the molecular machinery mediating FGF2 membrane translocation to be highly organized in liquid-ordered plasma membrane nanodomains, the core process underlying this unusual pathway of protein secretion.

Bruton's tyrosine kinase inhibition-An emerging therapeutic strategy in immune-mediated dermatological conditions.

Bruton's tyrosine kinase (BTK), a member of the Tec kinase family, is critically involved in a range of immunological pathways. The clinical application of BTK inhibitors for B‐cell malignancies has proven successful, and there is strong rationale for the potential benefits of BTK inhibitors in some autoimmune and allergic conditions, including immune‐mediated dermatological diseases. However, the established risk‐to‐benefit profile of “first‐generation” BTK inhibitors cannot be extrapolated to these emerging, non‐oncological, indications. “Next‐generation” BTK inhibitors such as remibrutinib and fenebrutinib entered clinical development for chronic spontaneous urticaria (CSU); rilzabrutinib and tirabrutinib are being studied as potential treatments for pemphigus. Promising data from early‐phase clinical trials in CSU suggest potential for these agents to achieve strong pathway inhibition, which may translate into measurable clinical benefits, as well as other effects such as the disruption of autoantibody production. BTK inhibitors may help to overcome some of the shortcomings of monoclonal antibody treatments for immune‐mediated dermatological conditions such as CSU, pemphigus, and systemic lupus erythematosus. In addition, the use of BTK inhibitors may improve understanding of the pathophysiological roles of mast cells, basophils, and B cells in such conditions.

A uniquely distributed purpuric drug eruption from acalabrutinib.

Acalabrutinib is a second-generation, highly selective Bruton's Tyrosine Kinase inhibitor (BTKi) indicated for use in some mature B-cell malignancies. The authors describe a uniquely distributed drug reaction presenting as palpable purpura over the bilateral upper limbs. BTKi is theorised to cause haemorrhage through off-target inhibition of Tec kinases and EGFR receptors. Dermatologists play an integral role in the multidisciplinary management of these patients to limit the negative impact on patient quality of life and, more importantly, to restrict dose reduction or treatment discontinuation.

TEC kinase stabilizes PLK4 to promote liver cancer metastasis.

Aberrated PLK4 expression has been reported in different malignancies and causes centrosome amplification, aneuploidy, and genomic instability. However, the mechanism by which PLK4 is regulated in carcinogenesis remains not fully characterised. Here, we showed that PLK4 was overexpressed in human HCC and overexpression of PLK4 predicted poorer patient prognosis. Unexpectedly, we found that induced expression of PLK4 promotes, but knockdown of PLK4 inhibits, HCC cell migration and invasion. Mechanistically, we found that TEC tyrosine kinase, which also promotes HCC cell migration, stabilizes PLK4 by phosphorylation. TEC directly phosphorylates PLK4 at tyrosine 86 residue, which not only stabilizes the protein but also enhances PLK4-mediated HCC cell invasion. Further investigation by transcriptome sequencing indicated that PLK4 promotes the phosphorylation of focal adhesion kinase to regulate the focal adhesion pathway in HCC cell migration. Taken together, our results demonstrated that PLK4 plays an important role in HCC metastasis and revealed for the first time the mechanism by which PLK4 promotes HCC metastasis via TEC phosphorylation.

The Tyrosine Kinase Tec Regulates Effector Th17 Differentiation, Pathogenicity, and Plasticity in T-Cell-Driven Intestinal Inflammation.

T helper (Th) 17 cells are not only key in controlling infections mediated by extracellular bacteria and fungi but are also triggering autoimmune responses. Th17 cells comprise heterogeneous subsets, some with pathogenic functions. They can cease to secrete their hallmark cytokine IL-17A and even convert to other T helper lineages, a process known as transdifferentiation relying on plasticity. Both pathogenicity and plasticity are tightly linked to IL-23 signaling. Here, we show that the protein tyrosine kinase Tec is highly induced in Th17 cells. Th17 differentiation was enhanced at low interleukin-6 (IL-6) concentrations in absence of Tec, which correlates with increased STAT3 phosphorylation and higher Il23r expression. Therefore, we uncovered a function for Tec in the IL-6 sensing via STAT3 by CD4+ T cells, defining Tec as a fine-tuning negative regulator of Th17 differentiation. Subsequently, by using the IL-17A fate mapping mouse combined with in vivo adoptive transfer models, we demonstrated that Tec not only restrained effector Th17 differentiation but also pathogenicity and plasticity in a T-cell intrinsic manner. Our data further suggest that Tec regulates inflammatory Th17-driven immune responses directly impacting disease severity in a T-cell-driven colitis model. Notably, consistent with the in vitro findings, elevated levels of the IL-23 receptor (IL-23R) were observed on intestinal pre- and postconversion Th17 cells isolated from diseased Tec−/− mice subjected to adoptive transfer colitis, highlighting a fundamental role of Tec in restraining IL-23R expression, likely via the IL-6-STAT3 signaling axis. Taken together, these findings identify Tec as a negative regulator of Th17 differentiation, pathogenicity, and plasticity, contributing to the mechanisms which help T cells to orchestrate optimal immune protection and to restrain immunopathology.

Effects of Prior Exposure to Tec Kinase(BTK/ITK) Inhibitors on Kte-X19 Products

Introduction:Frequent and durable responses were recently reported in relapsed or refractory (R/R) mantle cell lymphoma (MCL) patients treated with KTE-X19, an autologous CD19-targeted chimeric antigen receptor-engineered T-cell (CAR-T) product (Wang et al. N Engl J Med. 2020). Most patients enrolled had received at least one line of Tec kinase inhibitor prior to KTE-X19 manufacturing, either in the form of ibrutinib, a Bruton's tyrosine kinase (BTK) and Inducible T cell kinase (ITK) inhibitor, or acalabrutinib, a more selective BTK inhibitor. Pharmacokinetic expansion of KTE-X19 was higher in ibrutinib-treated patients relative to acalabrutinib-treated patients. We previously showed that prolonged exposure to ibrutinib enhanced T cell effector function and proliferation in patients with CLL (Fraietta et al, Blood, 2016). To assess the impact of Tec kinase inhibitor on KTE-X19 products and downstream clinical outcomes, we examined the phenotype, transcriptional profile and cytokine production of KTE-X19 infusion products and post-infusion lymphocytes from patients with R/R MCL treated on the Zuma-2 study.Study Design and Methods:We evaluated biospecimens from MCL patients who enrolled on the Zuma-2 clinical trial (NCT02601313) and who were previously treated with ibrutinib (n=14) or acalabrutinib (n=6). Samples analyzed consisted of KTE-X19 CAR T products and peripheral blood mononuclear cells (PBMC) collected 7 days after infusion. Lymphocytes were assessed for CAR expression, T cell phenotype, transcriptional profile and cytokine production. In addition, CAR T cell phenotypes and cytokines were profiled following co-culture of KTE-X19 with CD19 + Toledo cells (DLBCL).Results:Flow cytometric analysis of KTE-X19 demonstrated similar distributions of CD4+ and CD8+ T cells and comparable frequencies of central and effector memory populations in the CAR+ T cells derived from patients with prior exposure to ibrutinib vs. acalabrutinib. T helper subset analysis trended towards enrichment of Th1/Th17 populations within the CAR+ CD4+ cells of the ibrutinib cohort. This finding was further supported by transcriptional profiling of sorted CAR+ T cells from infusion products, where Th1/Th17, Jak/STAT and activation-related genes were enriched in the cohort with prior ibrutinib exposure. In addition, the Th1 phenotype was more frequent in PBMC of ibrutinib-exposed patients (8/14) compared to acalabrutinib-exposed patients (1/4). Interestingly, a shift from a central memory-dominant product towards an effector memory phenotype was observed in peripheral CD4+ and CD8+ CAR T cells in the ibrutinib cohort, whereas acalabrutinib post-infusion CAR T cells maintained a central memory phenotype. In vitro stimulation of KTE-X19 CAR-T infusion products with tumor cells resulted in a significant enrichment of the Th1 population in patients who had received ibrutinib compared to those that received acalabrutinib (p=0.0058). Following stimulation, CAR-T cells from the acalabrutinib cohort produced higher levels of Th2 cytokines, including IL-4, IL-5, and IL-13 as well as GM-CSF compared to the ibrutinib cohort.Conclusions:Analysis of KTE-X19 infusion products and day 7 post-infusion PBMC demonstrated that CAR T cells from patients with prior ibrutinib exposure have a Th1 predominant phenotype, suggesting that ibrutinib but not acalabrutinib promotes Th1 differentiation and effector function, potentially through the inhibition of ITK. Furthermore, our data suggest that inhibition of non-BTK targets such as ITK may play a role in driving a Th17 phenotype. Prior exposure to ibrutinib may increase CAR T cell effector function to a greater extent than exposure to acalabrutinib to enhance clinical outcome in patients with MCL. DisclosuresBudka: Kite Pharma: Current Employment. Sowrirajan: Kite Pharma: Current Employment. Nguyen: Kite Pharma: Current Employment. Shen: Gilead Sciences: Current equity holder in publicly-traded company; Kite, a Gilead Company: Current Employment, Other: Leadership role, Patents & Royalties; Atara: Current Employment, Current equity holder in publicly-traded company, Other: Leadership role, Patents & Royalties. Bot: Kite, a Gilead Company: Current Employment; Gilead Sciences: Consultancy, Current equity holder in publicly-traded company, Other: Travel support. Maus: Agenus: Consultancy; Arcellx: Consultancy; Astellas: Consultancy; AstraZeneca: Consultancy; Atara: Consultancy; Bayer: Consultancy; BMS: Consultancy; Cabaletta Bio (SAB): Consultancy; CRISPR therapeutics: Consultancy; In8bio (SAB): Consultancy; Intellia: Consultancy; GSK: Consultancy; Kite Pharma: Consultancy, Research Funding; Micromedicine: Consultancy, Current holder of stock options in a privately-held company; Novartis: Consultancy; Tmunity: Consultancy; Torque: Consultancy, Current holder of stock options in a privately-held company; WindMIL: Consultancy; Adaptimmune: Consultancy; tcr2: Consultancy, Divested equity in a private or publicly-traded company in the past 24 months; century: Current equity holder in publicly-traded company; ichnos biosciences: Consultancy, Current holder of stock options in a privately-held company.

High-Dimensional Analysis Identifies Mechanisms of Gilteritinib Resistance in FLT3-Mutated AML

While clinical benefit has been observed with gilteritinib in patients with FLT3 mutated relapsed/refractory acute myeloid leukemia (AML), most patients relapse through mechanisms that are incompletely understood. In this study, to investigate mechanisms of gilteritinib sensitivity and resistance, we performed targeted sequencing (21 patients) and scRNASeq analysis (8 patients) of FLT3-ITD-positive AML samples obtained before and during treatment. Before treatment, co-occurring mutations were observed in 33 genes among 21 patients. Mutations in RAS pathway genes (PTPN11, KRAS, NRAS, CBL) were the most common and observed in 57% (12/21) of patients. Seven patients pretreatment already contained RAS pathway mutations, of which 6 of these mutations were maintained over the course of treatment. During treatment, 9 patients showed emerging RAS mutations, 4 of which initially presented with a different RAS pathway mutation pre-treatment. Other mutations that arose during treatment were observed in CEBPA, IDH1, SF1 and WT1; as well as CSF3R, CUX1, PLEKHG5, and XPO1, not previously identified in gilteritinib-treated patients. Mutational clonality was generally maintained over treatment in both responders and non-responders. scRNASeq revealed global gene expression differences in myeloblast populations between gilteritinib-responsive and -unresponsive patients. Previous studies in vitro have shown that bone marrow-derived hematopoietic and inflammatory cytokines/chemokines confer resistance to FLT3 inhibitors. In the unresponsive group, we observed an increase in expression of CCL5, CXCL1, CXCL2, CXCL8, FLT3, IL6R, IL3RA, and CSF2RA during gilteritinib treatment, supporting the concept from preclinical studies that AML microenvironment-mediated factors play a critical role in drug resistance. Baseline expression of the Tec kinase BMX was significantly higher in unresponsive patients (Log2FoldChange, 6.65; adjusted P value, 0.00186), and this was maintained in the expanding myeloblast populations during treatment. Previously, upregulated BMX was shown to contribute to sorafenib resistance in patients with FLT3-ITD-positive AML, through cell-nonautonomous microenvironment hypoxia-dependent effects. Further in vitro investigation confirmed gilteritinib resistance could be reversed through genetic and pharmacological manipulation of BMX. Gene module analysis showed associations between gilteritinib responsive and upregulation of genes and pathways involved in lymphocyte differentiation and myeloid leukocyte activation, including TBX21, GATA3, CD33, and LYZ. By contrast, there was association between unresponsiveness to gilteritinib and upregulation of cell-cycle, DNA, and RNA metabolic processes, including pathways involving METTL1 and DNMT3A, as well as pre-treatment expression of pathways associated with protein translation. Together, these data provide support for microenvironment-dependent escape from targeted therapy and suggest that BMX may contribute to gilteritinib resistance. High-dimensional analysis with scRNA-seq provides a deeper understanding of targets and pathways for potential therapeutic intervention to restore gilteritinib sensitivity. DisclosuresBlachly: INNATE: Consultancy, Honoraria; KITE: Consultancy, Honoraria; AbbVie: Consultancy, Honoraria; AstraZeneca: Consultancy, Honoraria.