Project description:Drug-tolerant “persister” cells underlie the emergence of drug-resistant clones and allow residual tumors to survive therapy; thus, represent an attractive therapeutic target to mitigate relapse. With the promising outcome, yet some resistance cases surfaced after the approval of venetoclax (ABT-199), we defined a novel invasive drug resistance mechanism induced by Bcl2 inhibitor via examining the evolution of drug tolerant persister clones generated with ABT-199 treatment. The ABT-199 drug-tolerant persister cells showed genetic alteration by losing the copy number at 18q21 paralleled with BCL2, PMAIP1 and TCF4 gene downregulation. The persister status are generated through major enhancer-remodeling mediated transcriptional activation of the super enhancer, which offered unique opportunity for overcoming the drug resistance. The insight of major determinant for ABT-199 persistence evolution identified the molecular vulnerability in Bcl2 inhibitor resistant lymphoma cells through CDK7 pathway inhibition. The combined CDK7 and BCL2 inhibition was found to be more effective against ABT-199 persistence ex vivo and in vivo rather than the parental line, and CDK7 inhibition eliminated the persister phenotype by blocking dynamic active enhancer formation to further prevent the evolution of drug resistance. Together, these studies unified genetic alteration and non-mutational adaptive response as a drug resistance mechanism, more importantly, demonstrated a rationale for transcriptional inhibition-based combination strategies to prevent and overcome drug resistance in B-cell malignancies.
Project description:Drug-tolerant “persister” cells underlie the emergence of drug-resistant clones and allow residual tumors to survive therapy; thus, represent an attractive therapeutic target to mitigate relapse. With the promising outcome, yet some resistance cases surfaced after the approval of venetoclax (ABT-199), we defined a novel invasive drug resistance mechanism induced by Bcl2 inhibitor via examining the evolution of drug tolerant persister clones generated with ABT-199 treatment. The ABT-199 drug-tolerant persister cells showed genetic alteration by losing the copy number at 18q21 paralleled with BCL2, PMAIP1 and TCF4 gene downregulation. The persister status are generated through major enhancer-remodeling mediated transcriptional activation of the super enhancer, which offered unique opportunity for overcoming the drug resistance. The insight of major determinant for ABT-199 persistence evolution identified the molecular vulnerability in Bcl2 inhibitor resistant lymphoma cells through CDK7 pathway inhibition. The combined CDK7 and BCL2 inhibition was found to be more effective against ABT-199 persistence ex vivo and in vivo rather than the parental line, and CDK7 inhibition eliminated the persister phenotype by blocking dynamic active enhancer formation to further prevent the evolution of drug resistance. Together, these studies unified genetic alteration and non-mutational adaptive response as a drug resistance mechanism, more importantly, demonstrated a rationale for transcriptional inhibition-based combination strategies to prevent and overcome drug resistance in B-cell malignancies.
Project description:Two mice in which luciferase-positive LOUCY ETP-ALL cells were xenografted were treated with either vehicle or ABT-199 (50 mg/kg) for 11 days. Afterwards, single cells suspensions were made from bone marrow and spleen of both mice for 10x Genomics scRNA-seq. Following quality control, a total of 13,681 spleen cells and 11,442 bone marrow cells of the control mouse and 15,955 spleen cells and 9,443 bone marrow cells of the ABT 199 treated mouse were processed for further analysis. Our data show that ABT-199 triggers transcriptional changes in T-cell differentiation genes in leukemic cells obtained from the spleen microenvironment. These results are in line with our previous findings that mature typical T-ALL are resistant to ABT-199.
Project description:Drug-tolerant “persister” tumor cells underlie the emergence of drug-resistant clones contribute to relapse and disease progression; thus, identifying actionable targets that disable persisters and mitigate relapse are a high priority need. Although the BCL2-targeting agent venetoclax (ABT-199) has shown promising responses in mantle cell and double hit B cell lymphomas, resistance often arises, yet mechanistically how this occurs is unclear. Here we report that ABT-199 resistance can evolve from persister clones that have selective deletions at 18q21 that involve the drug target BCL2 and the apoptotic regulators Noxa (PMAIP1) and TCF4. Notably, reprogramming of super enhancers (SE) in persisters contributes to resistance, where there is a selection for SE-directed overexpression of the apoptotic regulator BCL2A1 and oncogenic transcription factors IKZF1 and FOXC1. At the same time, the SE reprogramming confers an opportunity for overcoming ABT-199 resistance. An unbiased drug screen on a platform that recapitulates the lymphoma microenvironment revealed that persisters are vulnerable to inhibitors of transcription initiation and elongation, and especially so to inhibitors of cyclin-dependent kinase 7 (CDK7) that is essential for transcription initiation. Specifically, CDK7 loss or inhibition eliminated the persister phenotype by disabling SE-driven expression of BCL2A1, IKZF1 and FOXC1. Thus, the co-treatment of ABT-199 with CDK7 inhibitors blocked the evolution of drug resistance, and provoked tumor regression in models of mantle cell lymphoma (MCL) and double hit lymphomas (DHL) that overexpress both MYC and BCL2. Together, these findings establish loss of apoptotic regulators and an adaptive transcriptional response as drug resistance mechanisms in lymphoma, more importantly, establish a rationale for transcription inhibition-based combination strategies to prevent and overcome drug resistance in B cell malignancies toward BCL2 inhibitor.
Project description:RNA-sequencing was performed to evaluate gene expression changes between ABT-199 (venetoclax) sensitive and resistant matched diffuse large B cell lymphoma cell lines
Project description:GSK3alpha has been identified as a new target in the treatment of acute myeloid leukemia (AML). However, most GSK3 inhibitors lack specificity for GSK3alpha over GSK3beta and other kinases. We have previously shown in lung cancer cells that GSK3alpha and to a lesser extent GSK3beta are inhibited by the advanced clinical candidate tivantinib (ARQ197), which was designed as a MET inhibitor. Thus, we hypothesized that tivantinib would be an effective therapy for the treatment of AML. Here, we show that tivantinib has potent anticancer activity across several AML cell lines and primary patient cells. Tivantinib strongly induced apoptosis, differentiation and G2/M cell cycle arrest and caused less undesirable stabilization of beta-catenin compared to the pan-GSK3 inhibitor LiCl. Subsequent drug combination studies identified the BCL-2 inhibitor ABT-199 to synergize with tivantinib. Interestingly, the addition of ABT-199 to tivantinib completely abrogated tivantinib induced beta-catenin stabilization. Tivantinib alone, or in combination with ABT-199, downregulated anti-apoptotic MCL-1 and BCL-XL levels, which likely contribute to the observed synergy. Importantly, tivantinib as single agent or in combination with ABT-199 significantly inhibited the colony forming capacity of primary patient AML bone marrow mononuclear cells. In summary, tivantinib is a novel GSK3alpha/beta inhibitor that potently kills AML cells and tivantinib single agent or combination therapy with ABT-199 may represent attractive new therapeutic opportunities for AML.
Project description:Diffuse large B-cell lymphoma (DLBCL) and follicular lymphoma (FL) are the most prevalent B-lymphocyte neoplasms in which abnormal activation of the Bruton’s tyrosine kinase (BTK)–mediated B-cell receptor (BCR) signaling pathway contributes to pathogenesis. Ibrutinib is an oral covalent BTK inhibitor that has shown some efficacy in both indications. To improve ibrutinib efficacy through combination therapy, we first investigated differential gene expression in parental and ibrutinib-resistant cell lines to better understand the mechanisms of resistance. Ibrutinib-resistant TMD8 cells had higher BCL2 gene expression and increased sensitivity to ABT-199, a BCL-2 inhibitor. Consistently, clinical samples from ABC-DLBCL patients who experienced poorer response to ibrutinib had higher BCL2 gene expression. We further demonstrated synergistic growth suppression by ibrutinib and ABT-199 in multiple ABC-DLBCL, GCB-DLBCL, and FL lymphoma cell lines. The combination of both drugs also reduced colony formation, increased apoptosis, and inhibited tumor growth in a TMD8 xenograft model. A synergistic combination effect was also found in ibrutinib-resistant cells generated by either genetic mutation or drug treatment. Together, these findings suggest a potential clinical benefit from ibrutinib and ABT-199 combination therapy.