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Pharmacological modulation of CXCR4 cooperates with BET bromodomain inhibition in diffuse large B-cell lymphoma.

ABSTRACT: Constitutive activation of the chemokine receptor CXCR4 has been associated with tumor progression, invasion, and chemotherapy resistance in different cancer subtypes. Although the CXCR4 pathway has recently been suggested as an adverse prognostic marker in diffuse large B-cell lymphoma, its biological relevance in this disease remains underexplored. In a homogeneous set of 52 biopsies from patients, an antibody-based cytokine array showed that tissue levels of CXCL12 correlated with high microvessel density and bone marrow involvement at diagnosis, supporting a role for the CXCL12-CXCR4 axis in disease progression. We then identified the tetra-amine IQS-01.01RS as a potent inverse agonist of the receptor, preventing CXCL12-mediated chemotaxis and triggering apoptosis in a panel of 18 cell lines and primary cultures, with superior mobilizing properties in vivo than those of the standard agent. IQS-01.01RS activity was associated with downregulation of p-AKT, p-ERK1/2 and destabilization of MYC, allowing a synergistic interaction with the bromodomain and extra-terminal domain inhibitor, CPI203. In a xenotransplant model of diffuse large B-cell lymphoma, the combination of IQS-01.01RS and CPI203 decreased tumor burden through MYC and p-AKT downregulation, and enhanced the induction of apoptosis. Thus, our results point out an emerging role of CXCL12-CXCR4 in the pathogenesis of diffuse large B-cell lymphoma and support the simultaneous targeting of CXCR4 and bromodomain proteins as a promising, rationale-based strategy for the treatment of this disease.

SUBMITTER: Recasens-Zorzo C

PROVIDER: S-EPMC6442946 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Aberrant changes in microRNAs (miRNAs) contribute to lymphomagenesis and represent potential therapeutic targets. OTX015 (MK-8628), a bromodomain and extra-terminal domain (BET) inhibitor (BETi), has demonstrated preclinical and clinical activity in haematological tumours. To better understand the mechanism of action of OTX015 we studied its effects on miRNAs in lymphomas. We performed miRNA profiling of DLBCL cells treated with OTX015 and observed changes in the expression levels of a subset of miRNAs, including miR-92a-1-5p, miR-21-3p, miR-155-5p and miR-96-5p, which are known to play a role in lymphomagenesis and/or resistance to chemotherapy. Analysis of publicly available BRD4 ChIP-Seq data of DLBCL cells treated with the BETi JQ1 showed that BRD4 was bound to the upstream regulatory regions of multiple miRNA genes and that this binding decreased following BETi. Alignment of our miRNA profiling data with the BRD4 ChIP-Seq data revealed that many miRNAs downregulated by OTX015 also exhibited reduced BRD4 binding in their promoter regions following BETi treatment, indicating that BRD4 directly modulated miRNA expression in lymphoma. Among the miRNAs upregulated in response to OTX015 was miR-96-5p, a miRNA known to play a role in B-cell transformation. In lymphomas, miR-96-5p transcription is repressed by the arginine methyltransferase PRMT5. In turn, PRMT5 translation is inhibited by miR-96-5p. We demonstrated that BRD4 bound to the 5’ regulatory region of PRMT5 and that following BET inhibition PRMT5 expression decreased, BRD4 binding to the 5’ region of PRMT5 was reduced and enrichment of PRMT5 at the miR-96-5p promoter lessened. Our results demonstrate that BRD4 binds to the promoters of miRNA genes to directly modulate their expression in lymphoma cells and that BETi administration results in decreased binding of BRD4 to the promoters of specific miRNAs to reduce their expression. Additionally, we show that BETi treatment can affect the expression of genes that control miRNA transcription to indirectly modulate miRNA expression. The data presented here indicate that the ability of BETi to inhibit or activate specific signalling pathways and processes critical to lymphoma cell proliferation and survival is in part due to changes in miRNA expression.

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Pharmacological modulation of CXCR4 cooperates with BET bromodomain inhibition in diffuse large B-cell lymphoma.

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