Project description:BTK plays a critical role in B cell malignancies survival. BTK inhibitor was successfully used as first line treatment for CLL in clinical. The emerging unmet needs is new segments are needed for ibrutinib R/R patients. The purpose of this study is to investigate genomic changes and signaling pathway differences after CLL cells were treated with BTK inhibitor (ibrutinib) or degrader (NRX0492).
Project description:Early-phase clinical trials of Bruton’s tyrosine kinase (BTK) degraders have demonstrated efficacy in patients with BTK inhibitor-resistant chronic lymphocytic leukemia (CLL). How clinical resistance to BTK degraders arises is unknown. Here we sequenced serial CLL samples from patients enrolled in the phase I trials of zelebrudomide and bexobrutideg and observed recurrent expansion of preexisting BTK A428D mutations at relapse. Unlike previously studied BTK inhibitor resistance mutations, BTK A428D conferred pan-resistance to BTK inhibitors and degraders. In the absence of BTK-directed therapies, however, cells bearing BTK A428D exhibited a competitive disadvantage. A crystal structure of BTK A428D revealed that the mutant aspartate confers broad resistance to ATP-competitive small molecules by obstructing essential drug contacts with the kinase hinge. Combining BTK degraders with venetoclax mitigated expansion of BTK A428D. These results provide the basis for clinical resistance to BTK degraders and will inform therapy sequencing and the development of next-generation degrader therapies.
Project description:Inactivating mutations in the NF-kB inhibitor NFKBIE are frequent in chronic lymphocytic leukemia (CLL) and have been associated with accelerated disease progression and inferior responses to chemotherapy. To further understand the role of NFKBIE mutations in CLL, we disrupted by CRISPR/Cas9 editing the NFKBIE gene in CLL cells derived from the Eμ-TCL1 transgenic mouse model and investigated how this will affect CLL growth and response to B cell receptor inhibitor treatment. In vitro and adoptive transfer experiments showed that NFKBIE-mutated cells have a growth advantage over NFKBIE-wild type cells when exposed to microenvironmental signals that activate the canonical NF-kB pathway and can induce alterations within the tumor microenvironment that may allow for escape from immune surveillance, including the expansion of CD8+ T cells with an exhausted phenotype and increased expression of PD-L1 on the malignant B cells. Consistent with these findings, significantly greater expression of the exhaustion markers PD1 and TIGIT was observed on T cells from CLL patients with NFKBIE-mutated compared to NFKBIE-wild type leukemia. In addition, in vitro and in vivo experiments showed that NFKBIE-mutated murine CLL cells are selectively resistant to BTK inhibitor treatment while remaining sensitive to treatment with a PI3K or SYK inhibitor. Reduced sensitivity to BTK inhibitor treatment was also observed in a series of 229 ibrutinib-treated CLL patients showing inferior outcomes for the NFKBIE-mutated cases. These findings provide evidence that NFKBIE-mutated CLL cells reshape and are selected by the tumor microenvironment and may account for suboptimal ibrutinib responses.
Project description:Mast cells are indispensable for LPS-induced septic hypothermia, in which TNF-α plays an essential role to initiate sepsis. Tec family non-receptor tyrosine kinases ITK and BTK regulate mast cell-derived TNF-α in response to allergic antigen, but their role in LPS-induced TNF-α production by mast cells and related pathology is unclear. We sought to investigate the role(s) of ITK and BTK in mast cell response in septic condition. We found that the absence of ITK and BTK leads to enhanced TNF-α production by bone marrow-derived mast cells (BMMC). Itk-/-Btk-/- mast cells exhibit hyperactive preformed and LPS-induced TNF-α production, along with enhanced expression of other related genes such as NF-κB targeted genes, compared to WT cells. Bone marrow cells from 8-week old WT, Itk-/-, Btk-/- and Itk-/-Btk-/- (double knockout: DKO) C57Bl/6 mice were cultured in murine Interleukin-3/Stem cell factor (IL-3/SCF) supplemented medium for 5 weeks to derive mast cells. WT, Itk-/-, Btk-/- and DKO bone marrow-derived mast cells (BMMC) were factor starved in medium without IL-3/SCF for 12 hours, followed by treatment with PBS (control) or 100 ng/ml LPS for 1 hour. Triplicates of each group were subjected to mouse whole genome genechip microarray analysis. Replicates were randomized on different chips to avoid systematic error.
Project description:Using the novel BTK inhibitor PF-303, we model the clinical phenotype of BTK inhibition by systematically examining the impact of PF-303 on the mature immune system in mice autoimmune indications. However, our current knowledge of the role of BTK in immune competence has been gathered in the context of genetic inactivation of btk in both mice and man. Using the novel BTK inhibitor PF-303, we model the clinical phenotype of BTK inhibition by systematically examining the impact of PF-303 on the mature immune system in mice. We implicate BTK in tonic BCR signaling, demonstrate dependence of the T3 B cell subset and IgM surface expression on BTK activity, and find that B1 cells survive and function independently of BTK. While BTK inhibition does not impact humoral memory survival, antigen-driven clonal expansion of memory B cells and antibody secreting cell generation are inhibited. These data define the role of BTK in the mature immune system and mechanistically predict the clinical phenotype of BTK inhibition. We used Affymetrix genechips to profile the transcriptional changes downstream of BTK inhibition after in vivo B-cell activation by anti-IgD Mice were injected with the novel BTK inhibitor PF-303 2 hours prior to anti-IgD mediated in vivo B-cell activation; B-cells where harvested 2 hours after anti-IgD activation and RNA isolated.
Project description:Bruton's tyrosine kinase (Btk) is important for B lymphocyte development. To identify genes that are differentially expressed in primary B cells lacking functional Btk, splenocytes from X-linked immunodeficiency (Xid), Btk knockout (KO) and immunocompetent CBA mice, were used in microarrays containing more than 12,000 genes and expressed sequence tags (ESTs). We found 4515 transcripts expressed in duplicate experiments in all three strains. Out of these, 38 were differentially expressed genes (21 up-regulated >2 fold and 17 down-regulated <-2 fold) between CBA and Btk defective mice. Ten out of these genes were selected and quantitative Real-Time PCR was conducted for validation and further investigation. Real-Time experiments correlated nicely with the microarray data. No definitive phenotypic difference has previously been reported between Xid and Btk KO mice. We found 7 genes, whose expression differed (>2 fold) between the two strains. Moreover, when the 38 genes, which differed between immunocompetent CBA and Btk defective mice were ranked according to fold-increase, the levels in Btk KO mice were significantly more altered. This suggests that the defect in Btk KO mice is more severe and demonstrates that the mutant Btk protein in Xid mice does not generally function as dominant negative form. Experiment Overall Design: 6 Affymetrix U74Av2 GeneChip arrays was run. Three initially with CBA, Xid and Btk KO mice and then additional three chips with new RNA preperations from new CBA, Xid and Btk KO mice.
Project description:Inhibition of Bruton’s tyrosine kinase (BTK) has proven to be highly effective in the treatment of B-cell malignancies such as chronic lymphocytic leukemia (CLL), autoimmune disorders and multiple sclerosis. Since the approval of the first BTK inhibitor (BTKi), Ibrutinib, several other inhibitors including Acalabrutinib, Zanubrutinib, Tirabrutinib and Pirtobrutinib have been clinically approved. All are covalent active site inhibitors, with the exception of the reversible active site inhibitor Pirtobrutinib. The large number of available inhibitors for the BTK target creates challenges in choosing the most appropriate BTKi for treatment. Side-by-side comparisons in CLL have shown that different inhibitors may differ in their treatment efficacy. Moreover, the nature of the resistance mutations that arise in patients appears to depend on the specific BTKi administered. We have previously shown that Ibrutinib binding to the kinase active site causes unanticipated long-range effects on the global conformation of BTK (Joseph, R.E., et al., 2020, https://doi.org/10.7554/eLife.60470). Here we show that binding of each of the five approved BTKi to the kinase active site brings about distinct allosteric changes that alter the conformational equilibrium of full-length BTK. Additionally, we provide an explanation for the resistance mutation bias observed in CLL patients treated with different BTKi and characterize the mechanism of action of two common resistance mutations: BTK T474I and L528W.