School of Medicine, Guangxi University, Nanning, Guangxi, 530004, China.
Department of Spleen and Stomach Liver Diseases, The First Affiliated Hospital of Guangxi University of Traditional Chinese Medicine, Nanning, Guangxi, 530200, China.
BMC Cancer. 2023 Mar 14;23(1):244. doi: 10.1186/s12885-023-10713-9.
Liver cancer is the third most deadly malignant tumor in the world with poor prognosis and lacks early diagnostic markers. It is urgent need to explore new biomarkers and prognostic factors. The oxysterol-binding protein-like family proteins (OSBPLs) are essential mediators of lipid transportation and cholesterol balancing which has been reported to participate in cancer progression. So far, the expression, immune infiltration, and prognosis of OSBPLs have not been elucidated in liver cancer.
The differential expressions of OSBPLs between liver tumor and normal tissues were assessed by analyzing RNA-seq data from TCGA and protein data from CPTAC, respectively. Subsequently, genetic variations, potential functional enrichment analysis, and immune cell infiltration were analyzed. Further, the prognostic effects of OSBPLs were identified via constructing lasso models and performing receiver operating characteristic curve (ROC) analysis. Moreover, 10 local liver cancer specimens were involved to validate the expression of OSBPL3 via immunohistochemistry (IHC) assay. Finally, CCK-8, cell cycle, apoptosis, transwell assays, real time qPCR (RT-qPCR), and western blot assays were conducted to explore the function of OSBPL3 in liver cancer cells.
The mRNA of OSBPL2, OSBPL3, and OSBPL8 were highly expressed while OSBPL6 was lowly expressed in liver cancer samples compared with normal samples. As to the protein expression, OSBPL2 and OSBPL3 were significantly elevated and OSBPL5, OSBPL6, OSBPL9, OSBPL10, OSBPL11 were downregulated in tumor samples. A positive correlation was found between copy number variations (CNV) and the expression of OSBPL2, OSBPL8, OSBPL9, OSBPL11, while DNA methylation was negatively associated with the expressions of OSBPLs. Of these, CNV amplification mainly contributed to the overexpression of OSBPL2 and DNA methylation may be responsible for the high expression of OSBPL3. Interestingly, OSBPL3, OSBPL5, SOBPL7, and OSBPL10 were significantly positively correlated with immune infiltration. Notably, OSBPL3 was identified correlated to overall survival (OS) and disease specific survival (DSS) in liver cancer. Functionally, knocking down OSBPL3 reduced liver cancer cell viability, induced a G2/M cell cycle arrest, promoted apoptosis, and restrained cell migration.
In aggregate, we reported a heretofore undescribed role of OSBPLs in liver cancer by analyzing multi-omics data. Importantly, we identified OSBPL3 was overexpressed in liver tumor compared with normal and its high expression was correlated with poor OS and DSS. Inhibition of OSBPL3 resulted in a pronounced decrease in cell proliferation and migration.
肝癌是世界上第三大最致命的恶性肿瘤，预后较差，缺乏早期诊断标志物。因此，迫切需要探索新的生物标志物和预后因素。氧化固醇结合蛋白样家族蛋白（OSBPLs）是脂质运输和胆固醇平衡的重要介质，已被报道参与癌症进展。迄今为止，OSBPLs 在肝癌中的表达、免疫浸润和预后尚未阐明。
通过分析 TCGA 的 RNA-seq 数据和 CPTAC 的蛋白质数据，分别评估 OSBPLs 在肝癌组织和正常组织中的差异表达。随后，进行遗传变异、潜在功能富集分析和免疫细胞浸润分析。进一步通过构建lasso 模型和进行接收者操作特征曲线（ROC）分析来确定 OSBPLs 的预后效应。此外，还使用免疫组织化学（IHC）检测对 10 例局部肝癌标本进行了 OSBPL3 表达的验证。最后，通过 CCK-8、细胞周期、凋亡、Transwell 检测、实时 qPCR（RT-qPCR）和 Western blot 检测，探讨了 OSBPL3 在肝癌细胞中的功能。
与正常样本相比，肝癌样本中 OSBPL2、OSBPL3 和 OSBPL8 的 mRNA 表达水平升高，而 OSBPL6 的表达水平降低。在蛋白质表达方面，OSBPL2 和 OSBPL3 显著升高，而 OSBPL5、OSBPL6、OSBPL9、OSBPL10 和 OSBPL11 则在肿瘤样本中下调。CNV 与 OSBPL2、OSBPL8、OSBPL9、OSBPL11 的表达呈正相关，而 DNA 甲基化与 OSBPLs 的表达呈负相关。其中，CNV 扩增主要导致 OSBPL2 过表达，而 DNA 甲基化可能导致 OSBPL3 高表达。有趣的是，OSBPL3、OSBPL5、SOBPL7 和 OSBPL10 与免疫浸润呈显著正相关。值得注意的是，OSBPL3 与肝癌的总生存期（OS）和疾病特异性生存期（DSS）相关。功能上，敲低 OSBPL3 可降低肝癌细胞活力，诱导 G2/M 细胞周期阻滞，促进凋亡，并抑制细胞迁移。
总之，我们通过分析多组学数据，报道了 OSBPLs 在肝癌中的作用，这是以前未曾描述过的。重要的是，我们发现 OSBPL3 在肝癌肿瘤中表达高于正常组织，其高表达与 OS 和 DSS 较差相关。抑制 OSBPL3 可显著降低细胞增殖和迁移。
