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P53-independent ibrutinib responses in an E?-TCL1 mouse model demonstrates efficacy in high-risk CLL.

ABSTRACT: Deletion of the short-arm of chromosome 17 (17p-) is one of the most critical genetic alterations used in chronic lymphocytic leukemia (CLL) risk stratification. The tumor suppressor TP53 maps to this region, and its loss or mutation accelerates CLL progression, hampers response to chemotherapy and shortens survival. Although florescent in situ hybridization analyses for 17p deletions are routinely performed during clinical diagnoses, p53 mutational status is often unexamined. Given the limited clinical data that exists for frontline treatment of patients with CLL harboring TP53 mutations, there is a need to understand the biology of CLL with TP53 mutations and identify treatment strategies for this subset of patients. Herein, we used a CLL mouse model (E?-TCL1) harboring one of the most common TP53 hot-spot mutations observed in CLL (p53(R172H), corresponding to p53(R175H) in humans) to evaluate its impact on disease progression, survival, response to therapy and loss of the remaining wild-type Trp53 allele following ibrutinib treatment. We show that ibrutinib was effective in increasing survival, activating cellular programs outside the p53 pathway and did not place selective pressure on the remaining wild-type Trp53 allele. These data provide evidence that ibrutinib acts as an effective treatment for aggressive forms of CLL with TP53 mutations.

SUBMITTER: Lee HJ

PROVIDER: S-EPMC5141356 | biostudies-literature | 2016 Jun

REPOSITORIES: biostudies-literature

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p53-independent ibrutinib responses in an Eμ-TCL1 mouse model demonstrates efficacy in high-risk CLL.

Lee H J HJ Gallardo M M Ma H H Zhang X X Larsson C A CA Mejia A A Hornbaker M J MJ Qi Y Y Su X X Pageon L R LR Quintas-Cardama A A Post S M SM

Blood cancer journal 20160610

Deletion of the short-arm of chromosome 17 (17p-) is one of the most critical genetic alterations used in chronic lymphocytic leukemia (CLL) risk stratification. The tumor suppressor TP53 maps to this region, and its loss or mutation accelerates CLL progression, hampers response to chemotherapy and shortens survival. Although florescent in situ hybridization analyses for 17p deletions are routinely performed during clinical diagnoses, p53 mutational status is often unexamined. Given the limited ...[more]

PMID: 27284738

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Project description:Development of chronic lymphocytic leukemia (CLL) is associated with severe immune dysfunction. T-cell exhaustion, immune checkpoint upregulation, and increase of regulatory T cells contribute to an immunosuppressive tumor microenvironment. As a result, CLL patients are severely susceptible to infectious complications that increase morbidity and mortality. CLL B-cell survival is highly dependent upon interaction with the supportive tumor microenvironment. It has been postulated that the reversal of T-cell dysfunction in CLL may be beneficial to reduce tumor burden. Previous studies have also highlighted roles for histone deacetylase 6 (HDAC6) in regulation of immune cell phenotype and function. Here, we report for the first time that HDAC6 inhibition exerts beneficial immunomodulatory effects on CLL B cells and alleviates CLL-induced immunosuppression of CLL T cells. In the Eμ-TCL1 adoptive transfer murine model, genetic silencing or inhibition of HDAC6 reduced surface expression of programmed death-ligand 1 (PD-L1) on CLL B cells and lowered interleukin-10 (IL-10) levels. This occurred concurrently with a bolstered T-cell phenotype, demonstrated by alteration of coinhibitory molecules and activation status. Analysis of mice with similar tumor burden indicated that the majority of T-cell changes elicited by silencing or inhibition of HDAC6 in vivo are likely secondary to decrease of tumor burden and immunomodulation of CLL B cells. The data reported here suggest that CLL B cell phenotype may be altered by HDAC6-mediated hyperacetylation of the chaperone heat shock protein 90 (HSP90) and subsequent inhibition of the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) pathway. Based on the beneficial immunomodulatory activity of HDAC6 inhibition, we rationalized that HDAC6 inhibitors could enhance immune checkpoint blockade in CLL. Conclusively, combination treatment with ACY738 augmented the antitumor efficacy of anti-PD-1 and anti-PD-L1 monoclonal antibodies in the Eμ-TCL1 adoptive transfer murine model. These combinatorial antitumor effects coincided with an increased cytotoxic CD8+ T-cell phenotype. Taken together, these data highlight a role for HDAC inhibitors in combination with immunotherapy and provides the rationale to investigate HDAC6 inhibition together with immune checkpoint blockade for treatment of CLL patients.

Dataset Information

P53-independent ibrutinib responses in an E?-TCL1 mouse model demonstrates efficacy in high-risk CLL.

Publications

p53-independent ibrutinib responses in an Eμ-TCL1 mouse model demonstrates efficacy in high-risk CLL.

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