Abstract
The present study examined the expression and biological functions of bromodomain-containing protein 4 (BRD4) in skin squamous cell carcinoma (SCC) cells. Our results show that BRD4 mRNA and protein expression was upregulated in human skin SCC cells, as compared to its level in the normal skin keratinocytes and fibroblasts. Treatment with BRD4 inhibitors, JQ1 and CPI203, resulted in proliferation inhibition, apoptosis and cell cycle arrest in both established (A431 cell line) and primary skin SCC cells. Furthermore, BRD4 knockdown (by targeted shRNAs) or knockout (by CRISPR/Cas9) largely inhibited A431 cell proliferation. Reversely, forced-overexpression of BRD4 in A431 cells facilitated cell proliferation. We show that BRD4 is required for the expression of several oncogenes, including cyclin D1, Bcl-2 and MYC. BRD4 inhibition, knockdown or knockout significantly decreased above oncogene expression in SCC cells. In vivo, CRISPR/Cas9-mediated BRD4 knockout significantly suppressed A431 xenograft tumor growth in severe combined immunodeficient (SCID) mice. Together, our results suggest that BRD4 could be a novel and pivotal oncogenic protein of skin SCC.
Copyright © 2017. Published by Elsevier Inc.
MeSH terms
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Acetamides / pharmacology
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Animals
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Apoptosis / drug effects
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Apoptosis / genetics
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Azepines / pharmacology
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CRISPR-Cas Systems
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Carcinoma, Squamous Cell / genetics*
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Carcinoma, Squamous Cell / metabolism
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Carcinoma, Squamous Cell / pathology
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Carcinoma, Squamous Cell / therapy
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Cell Cycle Checkpoints / drug effects
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Cell Cycle Checkpoints / genetics
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Cell Cycle Proteins
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Cell Line, Tumor
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Cell Proliferation / drug effects
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Cyclin D1 / genetics
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Cyclin D1 / metabolism
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Gene Expression Regulation, Neoplastic*
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Genetic Therapy / methods
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Humans
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Mice
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Mice, SCID
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Nuclear Proteins / antagonists & inhibitors
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Nuclear Proteins / genetics*
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Nuclear Proteins / metabolism
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Proto-Oncogene Proteins c-bcl-2 / genetics
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Proto-Oncogene Proteins c-bcl-2 / metabolism
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Proto-Oncogene Proteins c-myc / genetics
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Proto-Oncogene Proteins c-myc / metabolism
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RNA, Messenger / antagonists & inhibitors
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RNA, Messenger / genetics*
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RNA, Messenger / metabolism
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RNA, Small Interfering / genetics
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RNA, Small Interfering / metabolism
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Signal Transduction
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Skin Neoplasms / genetics*
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Skin Neoplasms / metabolism
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Skin Neoplasms / pathology
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Skin Neoplasms / therapy
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Transcription Factors / antagonists & inhibitors
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Transcription Factors / genetics*
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Transcription Factors / metabolism
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Triazoles / pharmacology
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Tumor Burden / drug effects
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Xenograft Model Antitumor Assays
Substances
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(+)-JQ1 compound
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Acetamides
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Azepines
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BCL2 protein, human
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BRD4 protein, human
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CCND1 protein, human
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CPI203
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Cell Cycle Proteins
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MYC protein, human
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Nuclear Proteins
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Proto-Oncogene Proteins c-bcl-2
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Proto-Oncogene Proteins c-myc
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RNA, Messenger
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RNA, Small Interfering
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Transcription Factors
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Triazoles
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Cyclin D1