BACKGROUND Alterations in the epidermal growth factor receptor and PI3K pathways in head and neck squamous cell carcinomas (HNSCCs) are frequent events that promote tumor progression. Ectopic expression of the epidermal growth factor receptor-targeting microRNA (miR), miR-27a* (miR-27a-5p), inhibits tumor growth. We sought to identify mechanisms mediating repression of miR-27a* in HNSCC, which have not been previously identified. METHODS We quantified miR-27a* in 47 oral cavity squamous cell carcinoma patient samples along with analysis of miR-27a* in 73 oropharyngeal and 66 human papillomavirus-positive (HPV+) samples from The Cancer Genome Atlas. In vivo and in vitro TP53 models engineered to express mutant TP53, along with promoter analysis using chromatin immunoprecipitation and luciferase assays, were used to identify the role of TP53 and TP63 in miR-27a* transcription. An HNSCC cell line engineered to conditionally express miR-27a* was used in vitro to determine effects of miR-27a* on target genes and tumor cells. RESULTS miR-27a* expression was repressed in 47 oral cavity tumor samples vs matched normal tissue (mean log2 difference = -0.023, 95% confidence interval = -0.044 to -0.002; two-sided paired t test, P = .03), and low miR-27a* levels were associated with poor survival in HPV+ and oropharyngeal HNSCC samples. Binding of ΔNp63α to the promoter led to an upregulation of miR-27a*. In vitro and in vivo findings showed that mutant TP53 represses the miR-27a* promoter, downregulating miR-27a* levels. ΔNp63α and nucleoporin 62, a protein involved in ΔNP63α transport, were validated as novel targets of miR-27a*. CONCLUSION Our results characterize a negative feedback loop between TP63 and miR-27a*. Genetic alterations in TP53, a frequent event in HNSCC, disrupt this regulatory loop by repressing miR-27a* expression, promoting tumor survival.

中文翻译：

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突变TP53在头颈部癌中破坏了TP63-miR-27a *反馈环。

背景技术头颈部鳞状细胞癌（HNSCC）中表皮生长因子受体和PI3K途径的改变是促进肿瘤进展的常见事件。靶向表皮生长因子受体的microRNA（miR），miR-27a *（miR-27a-5p）的异位表达抑制了肿瘤的生长。我们试图确定介导HNSCC中miR-27a *阻遏的机制，此前尚未发现。方法我们对47例口腔鳞状细胞癌患者样品中的miR-27a *进行了定量分析，并对73份来自癌基因组图谱的口咽和66例人乳头瘤病毒阳性（HPV +）样品中的miR-27a *进行了分析。经过工程改造以表达突变型TP53的体内和体外TP53模型，以及使用染色质免疫沉淀和荧光素酶测定的启动子分析，用来鉴定TP53和TP63在miR-27a *转录中的作用。在体外使用工程化条件表达miR-27a *的HNSCC细胞系来确定miR-27a *对靶基因和肿瘤细胞的作用。结果47个口腔肿瘤样品与匹配的正常组织相比，miR-27a *表达受到抑制（平均log2差异= -0.023，95％置信区间= -0.044至-0.002；双侧配对t检验，P = .03），较低的miR-27a *水平与HPV +和口咽HNSCC样品的不良存活率相关。ΔNp63α与启动子的结合导致miR-27a *的上调。体外和体内发现表明，突变型TP53抑制miR-27a *启动子，下调miR-27a *水平。ΔNp63α和核孔蛋白62（一种参与ΔNP63α转运的蛋白）被证实是miR-27a *的新靶标。结论我们的结果表明TP63和miR-27a *之间存在负反馈回路。TP53的基因改变是HNSCC中的常见事件，它通过抑制miR-27a *表达来破坏该调节环，从而促进了肿瘤的存活。