Ceramide synthase 3 affects invasion and metastasis of hepatocellular carcinoma via the SMAD6 gene.

Patients with hepatocellular carcinoma (HCC) have poor prognosis due to lack of early diagnosis and effective treatment. Therefore, there is an urgent need to better understand the molecular mechanisms associated with HCC and to identify effective targets for early diagnosis and treatment. This study is to explore the expression and biological role of ceramide synthase 3 (CerS3) in HCC.A total of 159 pairs of HCC tissues and adjacent non-tumor tissues were obtained from the patients underwent radical resection in Shenzhen People's Hospital, and the total RNA and proteins from HCC tissues and adjacent non-tumor tissues were obtained. The expression of CerS3 protein and mRNA in HCC was detected by immunohistochemistry, Western blotting and real-time PCR. In vitro experiments, Hep3B cells were divided into a control vector group and a CerS3 vector group, and the cells were transfected with retroviral vector containing control cDNA or CerS3 cDNA, respectively. HCCLM3 cells were divided into a normal control shRNA group and a CerS3 shRNA group, and the cells were transfected with lentiviral vectors containing normal control shRNA or CerS3 shRNA, respectively. MTT, EdU, Transwell and scratch method were used to detect cell proliferation, migration and invasion. RNA sequencing was performed to determine the downstream signal of CerS3.Compared with the corresponding adjacent tissues,the mRNA and protein levels of CerS3 were elevated in the HCC tissues, with significant difference (both P<0.05). The Univariate and multivariate analysis showed that the overall survival rate was significantly correlated with the presence of venous invasion (95% CI 1.8-9.2, P<0.01), TNM stage (95% CI 2.3-5.2, P<0.05), poor histological grade (95% CI 1.4-6.8, P<0.05), and CerS3 (95% CI 1.5-3.9, P<0.05). Furthermore, the high CerS3 expression levels in tumor tissues were significantly associated with shorter overall survival rates compared with the low CerS3 expression (P<0.05). Compared with the vector control group, the Hep3B cell viability, EdU positive cells, and migration and invasion cell numbers in the CerS3 vector group were significantly increased (all P<0.05). Compared with the shRNA normal control group, the HCCLM3 cell viability, EdU positive cells, and numbers of migrating and invasive cells in the CerS3 shRNA group were significantly lower (all P<0.05). The RNA sequencing confirmed that the small mothers against decapentaplegic family member 6 (SMAD6) gene as an oncogenic gene could promote the HCC metastasis.Clinically, the overexpression of CerS3 is closely related to poor clinical features and poor prognosis. Functionally, CerS3 participates in the proliferation, invasion and metastasis of liver cancer cells via activating SMAD6 gene.目的: 由于缺乏早期诊断和有效治疗，肝细胞癌(hepatocellular carcinoma，HCC)患者预后较差。因此迫切需要更好地了解HCC相关的分子机制，并确定早期诊断和治疗的有效靶点。本研究旨在探讨神经酰胺合成酶3(ceramide synthase 3，CerS3)在HCC中的表达及其生物学作用。方法: 收集深圳市人民医院159例HCC接受根治性切除术患者的临床标本，包括HCC组织和邻近非肿瘤组织。采用免疫组织化学染色、蛋白印迹法和real-time PCR检测CerS3在HCC组织和邻近非肿瘤组织中的表达。体外实验中，将Hep3B细胞分为载体对照组和CerS3载体组，并分别用含有cDNA对照或CerS3 cDNA的反转录病毒载体转染细胞；将HCC LM3细胞分为shRNA对照组或CerS3 shRNA组，并分别用含有shRNA对照或CerS3 shRNA慢病毒载体转染细胞。分别采用MTT、EdU、Transwell和划痕试验测定细胞的增殖、迁移和侵袭，并进行RNA测序以确定CerS3的下游信号。结果: 与相应的相邻非肿瘤组织相比，HCC组织中CerS3 mRNA和蛋白质水平均升高(均P<0.05)。Cox回归生存模型的单变量和多变量分析显示：静脉浸润(95% CI：1.8~9.2，P<0.01)、TNM分期(95% CI：2.3~5.2，P<0.05)、组织学分级差(95% CI：1.4~6.8，P<0.05)和CerS3(95% CI：1.5~3.9，P<0.05)与HCC患者总生存率显著相关。此外，与肿瘤组织中CerS3低表达患者相比，CerS3高表达患者的总生存率显著缩短(P<0.05)。与载体对照组相比，CerS3载体组Hep3B细胞活力、EdU阳性细胞数、迁移和侵袭细胞数均显著增加(均P<0.05)。与shRNA对照组相比，CerS3 shRNA组HCC LM3细胞活力、EdU阳性细胞数、迁移和侵袭细胞数均显著降低(均P<0.05)。RNA测序将母体抗生物皮肤生长因子同源物6(small mothers against decapentaplegic family member 6，SMAD6)基因鉴定为促进HCC转移的致癌基因。结论: CerS3的过度表达与不良临床特征和不良预后密切相关。CerS3在功能上可通过激活SMAD6基因参与肝癌细胞的增殖、侵袭和转移。.