Department of Oral and Maxillofacial Surgery, Binzhou Medical University Hospital, Binzhou, Shandong, 256603, China.
Department of Oral Medicine, Binzhou Medical University Hospital, Binzhou, Shandong, 256603, China.
Biochem Biophys Res Commun. 2020 Aug 27;529(3):685-691. doi: 10.1016/j.bbrc.2020.05.183. Epub 2020 Jul 18.
BRCA2 And CDKN1A Interacting Protein (BCCIP) is initially identified as a tumor suppressor. Some recent studies confirmed its p53 binding capability. In this study, we explored the regulatory effect of BCCIPβ on p53 stability in HPV-positive and HPV-negative HNSCC cells. RNA-seq data from TCGA-HNSC were extracted for transcript isoform analysis in HPV-positive and HPV-negative tumors. HPV16-positive UM-SCC-47 (SCC47) and UM-SCC-104 (SCC104) and HPV-negative SCC-9 (SCC9) and UM-SCC-1 (SCC1) cell lines were used as in vitro cell models. Results showed that BCCIPβ was the dominant transcript in both HPV-positive and HPV-negative HNSCC cases. Knockdown of BCCIPβ decreased p53 protein concentration in the two HPV-negative cell lines but increased p53 concentration in the two HPV-positive cell lines. BCCIPβ inhibition increased proliferation and G1/S transition of SCC9 and SCC1 cells. In comparison, BCCIPβ inhibition slowed proliferation and increased G1 arrest of SCC104 and SCC47 cells. BCCIPβ inhibition prolonged the half-life of p53 protein and reduced p53 ubiquitination in the two HPV16-positive cell lines. Co-IP assay confirmed interactions among BCCIPβ, HPV E6, and p53 in both SCC104 and SCC47 cells. In comparison, only the interaction between BCCIPα and p53 was confirmed in these two cell lines. Either E6 or BCCIPβ inhibition reduced p53 ubiquitination and increased p53 concentration. However, inhibiting E6 and BCCIPβ at the same did not generate synergistic effects. On the contrary, p53 ubiquitination level was even higher in the combination group, with lower p53 concentration compared to the shE6 group. BCCIPβ overexpression in SCC47 cells with HPV E6 depletion significantly reduced p53 ubiquitination. In conclusion, this study found a novel interaction between HPV E6 and BCCIPβ in HPV16-positive HNSCC cells. The presence of HPV E6 turned BCCIPβ from a p53 stabilizer to a ubiquitination facilitator. This mechanism helps explain why BCCIPβ acted as a tumor suppressor in HPV-negative HNSCC but exerted oncogenic function in HPV16-positive HNSCC.
BRCA2 和 CDKN1A 相互作用蛋白（BCCIP）最初被鉴定为肿瘤抑制因子。一些最近的研究证实了其与 p53 的结合能力。在这项研究中，我们探讨了 BCCIPβ 对 HPV 阳性和 HPV 阴性头颈鳞状细胞癌（HNSCC）细胞中 p53 稳定性的调节作用。从 TCGA-HNSC 中提取 RNA-seq 数据，用于 HPV 阳性和 HPV 阴性肿瘤的转录本亚型分析。HPV16 阳性的 UM-SCC-47（SCC47）和 UM-SCC-104（SCC104）以及 HPV 阴性的 SCC-9（SCC9）和 UM-SCC-1（SCC1）细胞系被用作体外细胞模型。结果表明，BCCIPβ 是 HPV 阳性和 HPV 阴性 HNSCC 病例中的主要转录本。BCCIPβ 敲低降低了两个 HPV 阴性细胞系中 p53 蛋白的浓度，但增加了两个 HPV 阳性细胞系中 p53 的浓度。BCCIPβ 抑制促进了 SCC9 和 SCC1 细胞的增殖和 G1/S 期过渡。相比之下，BCCIPβ 抑制减缓了 SCC104 和 SCC47 细胞的增殖并增加了 G1 期阻滞。BCCIPβ 抑制延长了两个 HPV16 阳性细胞系中 p53 蛋白的半衰期并减少了 p53 的泛素化。Co-IP 测定证实了 BCCIPβ、HPV E6 和 p53 之间在 SCC104 和 SCC47 细胞中的相互作用。相比之下，仅在这两个细胞系中证实了 BCCIPα 和 p53 之间的相互作用。E6 或 BCCIPβ 的抑制均减少了 p53 的泛素化并增加了 p53 的浓度。然而，同时抑制 E6 和 BCCIPβ 并没有产生协同作用。相反，与 shE6 组相比，组合组的 p53 泛素化水平甚至更高，p53 浓度更低。在 HPV E6 耗尽的 SCC47 细胞中过表达 BCCIPβ 可显著降低 p53 泛素化。总之，本研究在 HPV16 阳性 HNSCC 细胞中发现了 HPV E6 和 BCCIPβ 之间的新相互作用。HPV E6 的存在使 BCCIPβ 从 p53 稳定剂转变为泛素化促进剂。这种机制有助于解释为什么 BCCIPβ 在 HPV 阴性 HNSCC 中作为肿瘤抑制因子发挥作用，但在 HPV16 阳性 HNSCC 中发挥致癌作用。
