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Co-inhibition of BET proteins and NF-?B as a potential therapy for colorectal cancer through synergistic inhibiting MYC and FOXM1 expressions.

ABSTRACT: The bromodomain and extra-terminal domain inhibitors (BETi) are promising epigenetic drugs for the treatment of various cancers through suppression of oncogenic transcription factors. However, only a subset of colorectal cancer (CRC) cells response to BETi. We investigate additional agents that could be combined with BETi to overcome this obstacle. JQ1-resistant CRC cells were used for screening of the effective combination therapies with JQ1. RNA-seq was performed to explore the mechanism of synergistic effect. The efficacy of combinational treatment was tested in the CRC cell line- and patient-derived xenograft (PDX) models. In BETi-sensitive CRC cells, JQ1 also impaired tumor angiogenesis through the c-myc/miR-17-92/CTGF+THBS1 axis. CTGF knockdown moderately counteracted anti-angiogenic effect of JQ1 and led to partially attenuated tumor regression. JQ1 decreased c-myc expression and NF-?B activity in BETi-sensitive CRC cells but not in resistant cells. Bortezomib synergistically sensitized BETi-resistant cells to the JQ1 treatment, and JQ1+Bortezomib induced G2/M arrest in CRC cells. Mechanistically, inhibition of NF-?B by Bortezomib or NF-?B inhibitor or IKK1/2 siRNA all rendered BETi-resistant cells more sensitive to BETi by synergistic repression of c-myc, which in turn induces GADD45s' expression, and by synergistic repression of FOXM1 which in turn inhibit G2/M checkpoint genes' expression. Activation of NF-?B by I?B? siRNA induced resistance to JQ1 in BETi-sensitive CRC cells. Last, JQ1+Bortezomib inhibited tumor growth and angiogenesis in CRC cell line xenograft model and four PDX models. Our results indicate that anti-angiogenic effect of JQ1 plays a vital role in therapeutic effect of JQ1 in CRC, and provide a rationale for combined inhibition of BET proteins and NF-?B as a potential therapy for CRC.

SUBMITTER: Wu T

PROVIDER: S-EPMC5833769 | biostudies-literature | 2018 Feb

REPOSITORIES: biostudies-literature

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Co-inhibition of BET proteins and NF-κB as a potential therapy for colorectal cancer through synergistic inhibiting MYC and FOXM1 expressions.

Wu Tingyu T Wang Guanghui G Chen Wei W Zhu Zhehui Z Liu Yun Y Huang Zhenyu Z Huang Yuji Y Du Peng P Yang Yili Y Liu Chen-Ying CY Cui Long L

Cell death & disease 20180222 3

The bromodomain and extra-terminal domain inhibitors (BETi) are promising epigenetic drugs for the treatment of various cancers through suppression of oncogenic transcription factors. However, only a subset of colorectal cancer (CRC) cells response to BETi. We investigate additional agents that could be combined with BETi to overcome this obstacle. JQ1-resistant CRC cells were used for screening of the effective combination therapies with JQ1. RNA-seq was performed to explore the mechanism of sy ...[more]

PMID: 29472532

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Project description:BackgroundThe bromodomain and extra-terminal domain (BET) inhibitor is a type of anti-tumor agent, currently being evaluated in phase I and II clinical trials for cancer therapy. It can decrease MYC expression levels and cause effective anti-tumor effects in diverse human cancers. However, its cytotoxic effect and related mechanisms of drug resistance are poorly understood in hepatocellular carcinomas (HCC). Here, we investigated the anti-tumor effects of BET inhibitor on HCC and the molecular mechanisms involved in its associated drug resistance.MethodsWe assessed the cytotoxicity of BET inhibitor on HCC cells compared with sorafenib by cell viability assay, metastasis assay and reproduced the anti-tumor effect in xenograft mouse model. In addition, the molecular mechanisms involved in drug resistance on JQ1-resistant HCC cells were revealed by western blotting, qRT-PCR, whole exome-sequencing and gene-editing technology. Finally, with specific inhibition of EGFR or ERK activity by interference RNAs or inhibitors, the efficacy of the synergistic treatment was investigated using cell viability assay, colony formation, apoptosis and xenograft mouse model.ResultsWe found that JQ1, a commonly used BET bromo-domain inhibitor, offered a better anti-tumor response than sorafenib in MYC-positive HCC cells by inducing apoptosis in vitro and in vivo. Unlike sorafenib, JQ1 treatment significantly impaired mitochondrial respiration and glycolysis in HCC cells. Importantly, we revealed that MAPK activation by a previously undescribed activating mutation of EGFR-I645L, was critical for JQ1 sensitivity through stabilizing oncogenic MYC protein in JQ1-resistant HCC cells. Inhibition of either EGFR or ERK activity overcame the JQ1 resistance and significantly decreased MYC protein level in vitro and in vivo.ConclusionSince MYC amplification is frequently identified in HCC, co-occurring with EGFR amplification, our findings suggest that targeting EGFR signaling might be essential for JQ1 therapy in advanced HCC.

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Co-inhibition of BET proteins and NF-?B as a potential therapy for colorectal cancer through synergistic inhibiting MYC and FOXM1 expressions.

Publications

Co-inhibition of BET proteins and NF-κB as a potential therapy for colorectal cancer through synergistic inhibiting MYC and FOXM1 expressions.

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