HPCAL1促进Nanog降解调控肝癌干细胞自我更新和转移的机制研究

Hepatocellular Carcinoma（HCC） is known to be a malignant tumor with poor prognosis, owning to its high recurrence and metastasis properties. Liver cancer stem cells are a subpopulation of cancer cells capable of self-renewing and driving invasive and metastatic phenotypes and are considered to be the root of tumor recurrence and metastasis. Nanog is regarded as the potent regulator in maintaining stemness property. Previously we have for the first time found HPCAL1 is a novel biomarker for HCC. HPCAL1 promotes HCC progression by increasing p21 stabilization via activation ERK1/2 signaling pathway. However, mechanisms that underlying the self-renewal and metastasis of liver cancer stem cells have not been reported. We have found that HPCAL1 could inhibit the self-renewal and metastasis of liver cancer stem cells. Furthermore, HPCAL1 could bind to Nanog, thereby decreasing its protein stability. Also, we demonstrated HPCAL1 promotes MET (mesenchymal–epithelial transition) by gene-specific regulation of Twist1 in a Nanog-dependent manner. Taken together, the current study aims to investigate mechanisms that underlying the self-renewal and metastasis of liver cancer stem cells driven by HPCAL1 from the levels of cell, mouse model and clinical samples. Our ultimate goal is to verify the possibility of HPCAL1 as a novel biomarker for prediction of HCC recurrence and metastasis.

原发性肝癌具有高复发和高转移的生物学特性，是导致肝癌患者预后差的主要原因。肝癌干细胞是一类具有自我更新能力的细胞群，具有更强的侵袭和转移潜能，是肝癌复发和转移的根源。Nanog是公认的维持肿瘤干细胞干性特征的关键调控因子。我们首次发现并报道了HPCAL1是肝癌的新型标志物。HPCAL1通过激活ERK1/2信号通路抑制p21的泛素化降解而调控肝癌增殖。但是，HPCAL1在肝癌干细胞自我更新及转移的中作用尚未研究。前期研究发现，HPCAL1能够促进肝癌干细胞的自我更新和转移能力，并首次发现HPCAL1能够与Nanog相互作用并抑制其蛋白质稳定性。同时，HPCAL1能够通过Nanog选择性下调Twist1而抑制上皮间质细胞转化。本研究拟通过阐明HPCAL1通过调控Nanog的稳定性抑制肝癌转移的分子机制，并从细胞，动物及临床标本多个层次验证，探讨HPCAL1作为肝癌复发和转移标志物的可行性。

原发性肝癌具有高复发和高转移的生物学特性，是导致肝癌患者预后差的主要原因。我们首次发现并报道了HPCAL1是肝癌的新型标志物。通过多种体内体外模型，我们发现HPCAL1能够显著抑制肝癌的转移潜能。 本研究通过构建Hpcal1基因敲除小鼠，进一步证实Hpcal1缺失引起肝癌发生和肺转移，并伴随着胆囊扩张和胆结石发生。HPCAL1与上皮间质细胞转化的关键调控因子相互作用并调控EMT下游靶基因的表达。通过RNA-seq测序，我们发现Hpcal1与脂质代谢密切相关，包括脂肪代谢和神经酰胺代谢等。这些结果均提示HPCAL1可能通过TWIST1调控脂肪代谢和神经酰胺代谢抑制肿瘤转移。我们还解析了肿瘤组织中神经酰胺代谢通路的表达图谱和代谢图谱，发现了从头代谢通路相关基因（SPTLC1,CERS1,CERS2，CERS6）以及产物（C16，C18,C20,C24-Ceramide，）在肿瘤中显著异常表达。C24-Ceramide显著促进肿瘤生长和转移，并可与PIP4K2C直接结合促进mTOR通路而促进肿瘤发生发展。我们还设计了短链C6-Ceramide，前者可竞争性结合C24-Ceramide,抑制肿瘤生长和转移。这些研究结果揭示了Hpcal1抑制肝癌复发转移的分子机制。此外，我们鉴定了以神经酰胺通路为靶点，设计了针对肿瘤的新型治疗策略。