肿瘤血液微循环形成的新机制

The development of adequate blood microcirculation is essential for tumor growth and metastasis. However, it remains debatable whether microvessel density (MVD，a classical index of tumor angiogenesis) is associated with tumor metastasis and recurrence after resection in hepatocellular carcinoma (HCC), although active angiogenesis is required for the rapid growth of HCC. We recently observed the presence of two distinct patterns of blood microcirculation in HCC tissues: endothelium-coated tumor cell clusters (ECTC) and vasculogenic mimicry (VM,-an architecture of vessels lined exclusively by tumor cells). Notably, the presence of ECTC or/and VM were an independent predictor of reccurence and poor survival in HCC patients. These data suggest that the formation of ECTC and VM may play crucial roles in developing blood microcirculation and protmoting blood-borne metastasis in HCC. By maicroarray analysis, we screened the expression profile of HCC tissues with or without ECTC and/or VM, and obtained a cohort of differential expression genes (including a subset of candidates presented in both ECTC- and VM-tissues). Furthermore, we have also established in vitro and in vivo mouse model to recapitulate these phenotypes. With these findings as background, we will combine the clinical sample analysis and experimental studies to further investigate: 1)the molecular mechanisms underlying the modulation of VM and ECTC by HCC cells; 2)the implication of tumor stromal cells in the formation of VM and ECTC; 3)the feasibility of individual therapy for HCC patients according to the patterns of blood microcirculation. The results obtained will not only reveal the mechanisms underlying the formation of blood microcirculation in HCC, but also provide the molecular basis to select potential HCC patients who may benefit more from proper molecular-targeted drugs.

建立有效的血液微循环是肿瘤生长转移的先决条件。但在肝癌组织中，微血管密度（经典的评价血管生成指标）与肿瘤转移复发的关系尚无定论。我们在肝癌组织中观察到一种由内皮细胞包裹肿瘤细胞团(ECTC)的独特血管结构以及不依赖于内皮细胞的血管拟态（VM），而且这两类结构均与肿瘤转移复发密切相关。提示：ECTC和VM可能是肝癌建立血液微循环并发生血行转移的重要机制。我们已分别在有或无ECTC以及VM的临床样本中筛选到差异表达基因（包括部分在这两类结构中重叠的基因），并建立了相应的细胞和动物模型。以此为基础，本课题拟结合临床样本和实验模型来研究并比较：1）肝癌细胞调控VM和ECTC形成的分子机制；2）肿瘤间质细胞对VM和ECTC形成的影响及其机制；3）探讨基于不同的血液微循环结构进行选择性干预治疗肝癌的可行性。所得结果不仅有助于揭示肝癌血液微循环的形成机制，还可望为发展基于微循环结构的个体化治疗奠定基础。

有效的血液微循环既可为肿瘤细胞提供氧气和养分，也可为癌细胞转移提供通道，是肿瘤生长转移的前提条件。内皮细胞构成的脉管系统和癌细胞构成的血管拟态结构（VM）是肿瘤血液微循环的重要组成，但它们的形成机制及其在肿瘤发生发展中的作用尚不清楚。因此，本项目结合细胞、小鼠模型及病人标本分析，系统地阐述了肝癌血液微循环形成的新机制及其临床意义，取得了如下的重要发现：1）揭示了VETC血管结构介导的新型转移途径，并鉴定了调控VETC形成的新型分子。我们发现肝癌组织存在一种新型的血管形态，我们称之肿瘤包绕型血管（vessels that encapsulated tumor clusters, VETC），VETC与病人复发转移密切相关。深入研究揭示肝癌细胞Ang-2表达升高及miRNA-100和miRNA-125下降、内皮细胞膜表面CXCR4升高是促进VETC形成的关键，VETC能够提供一种不依赖于EMT的高效转移模式，使得肿瘤细胞集群在内皮的包绕中成团释放到血液中，从而实现转移。（2）发现了调控肝癌毛细管状血管生成及肝癌转移的新分子。我们揭示了肝癌细胞内miRNA-195的下降或肝癌细胞高分泌miRNA-210可促进肝癌血管生成；肝癌细胞内miRNA-195的下降或纤维化肺组织分泌的Fn1和Spp1则促进肿瘤细胞转移。（3）阐述了肿瘤间质细胞对VM形成的调控作用，并鉴定了调控VM形成的新分子。肿瘤间质细胞CAF和TAM可通过分泌细胞因子，包括IL-6、TGF-β和SDF1，促进肿瘤细胞形成VM，而miR-29b和miR-101则能抑制肿瘤间质细胞对VM形成的诱导作用。上述研究结果从新的角度、更全面地阐述肝癌血液微循环的模式及其临床意义，为抗肿瘤治疗提供了新靶点，具有较好的创新性和临床应用前景。