Hepatic Surgery Center, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Clinical Medicine Research Center for Hepatic Surgery of Hubei Province, Key Laboratory of Organ Transplantation, Ministry of Education, NHC Key Laboratory of Organ Transplantation, Key Laboratory of Organ Transplantation, Chinese Academy of Medical Sciences, Wuhan, Hubei, 430030, People's Republic of China.
Department of Hepatobiliary Surgery, The First Affiliated Hospital, College of Medicine, Shihezi University, Shihezi, Xinjiang, 832008, People's Republic of China.
J Exp Clin Cancer Res. 2019 Feb 26;38(1):101. doi: 10.1186/s13046-019-1058-6.
Deregulation of ubiquitin ligases is related to the malignant progression of human cancers. F-box only protein 22 (FBXO22), an F-box E3 ligase, is a member of the F-box protein family. However, the biological function of FBXO22 in HCC and the underlying molecular mechanisms are still unclear. In this study, we explored the role of FBXO22 in HCC and its mechanism of promoting tumor development.
We examined the expression of FBXO22 in normal liver cell lines, HCC cell lines, HCC tissue microarrays and fresh specimens. The correlation between FBXO22 and clinical features was analyzed in a retrospective study of 110 pairs of HCC tissue microarrays. Univariate and multivariate survival analyses were used to explore the prognostic value of FBXO22 in HCC. At the same time, the correlation between the FBXO22 and p21 was also studied in HCC samples. Knock-down and overexpression experiments, CHX and Mg132 intervention experiments, ubiquitination experiments, rescue experiments and nude mouse xenograft models were used to determine the potential mechanism by which FBXO22 promotes tumorigenesis in vitro and in vivo.
The expression of FBXO22 in HCC tissues was significantly higher than in normal liver tissues. The overall survival rate and disease-free survival time of patients with high expression of FBXO22 were significantly shorter than those of patients with low expression of FBXO22. The high expression of FBXO22 in HCC tissues were significantly correlated with serum AFP (p = 0. 003, Pearson's chi-squared test), tumor size (p = 0. 019, Pearson's chi-squared test) and vascular invasion (p = 0. 031, Pearson's chi-squared test). Especially, Multivariate analysis showed that tumor size and the expression of FBXO22 were independent prognostic indicator of OS (95% CI: 1.077-5.157, P<0.05). Correlation analysis also showed that FBXO22 was negatively correlated with p21 in tissue microarrays (r = - 0.3788, P<0.001, Pearson correlation) and fresh specimens (r = - 0.4037, P<0.01, Pearson correlation). Moreover, both in vitro and in vivo experiments showed that knocking down FBXO22 expression could inhibit cell proliferation, while overexpression of FBXO22 promoted tumor formation. Furthermore, we identified that FBXO22 interacts with p21 by regulating protein stability and by influencing the ubiquitination process. A knockdown of FBXO22 decreased the ubiquitylation of p21, while overexpression enhanced it.
This study uncovered a new mechanism by which FBXO22 functions as an oncogene in HCC pathogenesis and progression by mediating the ubiquitination and degradation of p21. It was also found that tumor size and the expression of FBXO22 were independent prognostic indicator of OS and the expression of FBXO22 and p21 was negatively correlated in clinical samples. Our findings present a new perspective for understanding the development of HCC, which may provide a new target for the treatment and management of this challenging cancer.
泛素连接酶的失调与人类癌症的恶性进展有关。F-box 仅蛋白 22（FBXO22）是 F-box 蛋白家族的一员，作为一种 F-box E3 连接酶，其在 HCC 中的生物学功能及其促进肿瘤发展的潜在机制尚不清楚。在这项研究中，我们探讨了 FBXO22 在 HCC 中的作用及其促进肿瘤发生的机制。
我们检测了正常肝细胞系、HCC 细胞系、HCC 组织微阵列和新鲜标本中 FBXO22 的表达情况。通过对 110 对 HCC 组织微阵列的回顾性研究，分析了 FBXO22 与临床特征之间的相关性。采用单因素和多因素生存分析探讨了 FBXO22 在 HCC 中的预后价值。同时，还研究了 HCC 样本中 FBXO22 与 p21 的相关性。通过敲低和过表达实验、CHX 和 Mg132 干预实验、泛素化实验、挽救实验和裸鼠异种移植模型，确定了 FBXO22 促进体外和体内肿瘤发生的潜在机制。
与正常肝组织相比，HCC 组织中 FBXO22 的表达明显升高。FBXO22 高表达的 HCC 患者总生存率和无病生存率明显短于 FBXO22 低表达的患者。HCC 组织中 FBXO22 的高表达与血清 AFP（p=0.003，Pearson 卡方检验）、肿瘤大小（p=0.019，Pearson 卡方检验）和血管侵犯（p=0.031，Pearson 卡方检验）显著相关。特别是，多因素分析表明肿瘤大小和 FBXO22 的表达是 OS 的独立预后指标（95%CI：1.077-5.157，P<0.05）。相关性分析还表明 FBXO22 与组织微阵列中的 p21（r=-0.3788，P<0.001，Pearson 相关）和新鲜标本（r=-0.4037，P<0.01，Pearson 相关）呈负相关。此外，体外和体内实验均表明，敲低 FBXO22 表达可抑制细胞增殖，而过表达 FBXO22 则促进肿瘤形成。此外，我们还发现 FBXO22 通过调节蛋白稳定性和影响泛素化过程与 p21 相互作用。敲低 FBXO22 可降低 p21 的泛素化，而过表达则增强其泛素化。
本研究揭示了 FBXO22 通过介导 p21 的泛素化和降解在 HCC 发病机制和进展中作为癌基因发挥作用的新机制。此外，还发现肿瘤大小和 FBXO22 的表达是 OS 的独立预后指标，临床样本中 FBXO22 和 p21 的表达呈负相关。我们的研究结果为理解 HCC 的发展提供了新的视角，可能为这种具有挑战性的癌症的治疗和管理提供新的靶点。
