Dataset Information

The Covalent CDK7 Inhibitor THZ1 Potently Induces Apoptosis in Multiple Myeloma Cells In Vitro and In Vivo.

ABSTRACT:

Purpose

The goal of this study was to characterize the activity of the covalent CDK7 inhibitor THZ1 in multiple myeloma models.

Experimental design

Multiple myeloma lines were exposed to varying THZ1 concentrations alone or with carfilzomib or ABT-199, after which apoptosis was monitored by flow cytometry, protein expression by Western blot analysis, mRNA by RT-PCR. Analogous studies were performed in cells ectopically expressing c-MYC, MCL-1, or BCL-XL, or CRISPER-Cas CDK7 sgRNA knockout. Primary multiple myeloma cells were exposed to THZ1 ± carfilzomib or ABT-199. In vivo effects of THZ1 were examined in a systemic U266 xenograft model.

Results

THZ1 markedly diminished multiple myeloma cell proliferation and survival despite bortezomib or stromal cell resistance in association with G₂-M arrest, inactivation of CTD RNA Pol II, dephosphorylation of CDKs 7 as well as 1, 2, and 9, and MCL-1, BCL-xL, and c-MYC mRNA or protein downregulation. Ectopic MCL-1, c-MYC, or BCL-X_L expression significantly protected cells from THZ1 lethality. Both THZ1 and CRISPR-Cas CDK7 knockout sharply diminished multiple myeloma cell proliferation and significantly increased carfilzomib and ABT-199 lethality. Parallel effects and interactions were observed in primary CD138⁺ (N = 22) or primitive multiple myeloma cells (CD138^-/CD19⁺/CD20⁺/CD27⁺; N = 16). THZ1 administration [10 mg/kg i.p. twice daily (BID), 5 days/week] significantly improved survival in a systemic multiple myeloma xenograft model with minimal toxicity and induced similar events observed in vitro, for example, MCL-1 and c-MYC downregulation.

Conclusions

THZ1 potently reduces multiple myeloma cell proliferation through transcriptional downregulation of MCL-1, BCL-X_L, and c-MYC in vitro and in vivo. It warrants further attention as a therapeutic agent in multiple myeloma.

SUBMITTER: Zhang Y

PROVIDER: S-EPMC6801078 | biostudies-literature | 2019 Oct

REPOSITORIES: biostudies-literature

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Publications

The Covalent CDK7 Inhibitor THZ1 Potently Induces Apoptosis in Multiple Myeloma Cells <i>In Vitro</i> and <i>In Vivo</i>.

Zhang Yu Y Zhou Liang L Bandyopadhyay Dipankar D Sharma Kanika K Allen Alexander Joseph AJ Kmieciak Maciej M Grant Steven S

Clinical cancer research : an official journal of the American Association for Cancer Research 20190729 20

<h4>Purpose</h4>The goal of this study was to characterize the activity of the covalent CDK7 inhibitor THZ1 in multiple myeloma models.<h4>Experimental design</h4>Multiple myeloma lines were exposed to varying THZ1 concentrations alone or with carfilzomib or ABT-199, after which apoptosis was monitored by flow cytometry, protein expression by Western blot analysis, mRNA by RT-PCR. Analogous studies were performed in cells ectopically expressing c-MYC, MCL-1, or BCL-XL, or CRISPER-Cas CDK7 sgRNA ...[more]

PMID: 31358538

Similar Datasets

Project description:IntroductionThe emergence of resistance to the highly successful BCL2-directed therapy is a major unmet need in acute myeloid leukemia (AML), an aggressive malignancy with poor survival rates. Towards identifying therapeutic options for AML patients who progress on BCL2-directed therapy, we studied a clinical-stage CDK7 inhibitor XL102, which is being evaluated in solid tumors (NCT04726332).Materials and methodsTo determine the anti-proliferative effects of XL102, we performed experiments including time-resolved fluorescence resonance energy transfer, target occupancy, cell cycle and apoptosis-based assays. We also included genetically characterized primary myeloid blasts from de novo and relapsed/refractory AML patients. For mechanistic studies, CRISPR/Cas9 mediated knockout of CDK7 and c-Myc and immunoblotting were performed. NOD/SCID orthotropic and subcutaneous AML xenografts were used to determine anti-leukemic effects. To assess the synergistic effects of XL102 with Venetoclax, we performed RNA sequencing and gene set enrichment analysis using Venetoclax sensitive and resistant model systems.ResultsXL102, a highly specific, orally bioavailable covalent inhibitor of CDK7. Inhibitory effect on CDK7 by XL102 in primary myeloid blasts (n = 54) was in nanomolar range (mean = 300 nM; range = 4.0-952 nM). XL102 treated AML cells showed a reduction in phosphorylation levels of Serine 2/5/7 at carboxy-terminal domain of RNA polymerase II. T-loop phosphorylation of CDK1(Thr161) and CDK2(Thr160) was inhibited by XL102 in dose-dependent manner leading to cell-cycle arrest. c-Myc downregulation and enhanced levels of p53 and p21 in XL102 treated cells were observed. Increased levels of p21 and activation of p53 by XL102 were mimicked by genetic ablation of CDK7, which supports that the observed effects of XL102 are due to CDK7 inhibition. XL102 treated AML xenografts showed remarkable reduction in hCD45 + marrow cells (mean = 0.60%; range = 0.04%-3.53%) compared to vehicle control (mean = 38.2%; range = 10.1%-78%), with corresponding increase in p53, p21 and decrease in c-Myc levels. The data suggests XL102 induces apoptosis in AML cells via CDK7/c-Myc/p53 axis. RNA-sequencing from paired Venetoclax-sensitive and Venetoclax-resistant cells treated with XL102 showed downregulation of genes involved in proliferation and apoptosis.ConclusionTaken together, XL102 with Venetoclax led to synergistic effects in overcoming resistance and provided a strong rationale for clinical evaluation of XL102 as a single agent and in combination with Venetoclax.