淋巴管生成因子-C、-D及其受体在肿瘤淋巴管生成和转移中作用机制

淋巴管生成因子（VEGF）-C,-D及其受体（VEGFRs）在肿瘤组织淋巴管生成和淋巴道转移方面起着重要作用,针对于这些信号传导靶点的分子生物学研究和治疗已成为近几年的研究热点。现就这些因子在细胞内的分子信号传导途径以及在诱导淋巴管生成时,分子信号之间的协同作用作一综述。     

肿瘤淋巴管生成与淋巴转移

淋巴转移是恶性肿瘤的主要转移途径.研究发现淋巴系统结构特点是淋巴转移的解剖学基础;肿瘤淋巴管内皮特异性标志物检测有助于明确淋巴管生成;肿瘤内和肿瘤旁组织内存在新生淋巴管,淋巴管密度的表达强度与淋巴结转移密切相关;血管内皮生长因子(vascular endothelial growth factor,VEGF)家族的研究为揭示恶性肿瘤淋巴转移机制提供了重要的研究途径.     

肿瘤淋巴管生成与肿瘤转移研究进展

现已证实淋巴管是肿瘤细胞转移播散至局部淋巴结的主要通路。但关于淋巴管发生的分子机制却了解甚少。新近研究证明血管内皮生长因子(VEGF)-C和VEGF-D及其受体VEGFR-3信号通路是淋巴管形成的基础,并在转基因动物模型观察到VEGF-C和VEGF-D可诱导肿瘤淋巴管生成,并促进其淋巴结转移。然而,VEGF-C和-D如何调节肿瘤相关淋巴管生成,对于肿瘤细胞如何从原发肿瘤逃逸,并怎样进入淋巴管,目前仍不清楚。为此,现就近期淋巴管生成与肿瘤转移研究进展作一简要综述。     

喉癌中血管内皮素-1的表达与血管内皮生长因子-C、淋巴管生成及预后的关系

目的:探讨血管内皮素-1(ET-1)在喉癌组织中的表达与血管内皮生长因子-C(VEGF-C)、淋巴管密度(LVD)、淋巴转移之间的关系及其在喉癌预后中的意义.方法:以45例经病理确诊的喉癌组织为实验组,20例喉良性病变组织为对照组,采用免疫组织化学SP法对上述组织中ET-1、VEGF-C蛋白的表达进行分析,同时采用5′-核苷酸酶-碱性磷酸酶双重染色法(5'-Nase-ALP)计数LVD,并结合临床病理特征和生存资料进行相关分析.结果:喉癌组织中ET-1和VEGF-C的表达均高于良性病变组织,且ET-1和VEGF-C的表达具有相关性;在喉癌组织中ET-1的表达与瘤内LVD和瘤周LVD、淋巴结转移、淋巴管浸润、TNM临床分期呈正相关,ET-1+/VEGF-C+、VEGF-C的表达与生存率呈负相关,其中ET-1+/VEGF-C+组具有高危死亡率.结论:ET-1促进喉癌淋巴管生成和淋巴管转移,ET-1信号途径和VEGF-C信号途径可能对喉癌淋巴管生成和转移有协同促进作用,联合检测ET-1和VEGF-C的表达可成为独立判断喉癌预后的新的生物学指标.     

VEGF-C、VEGFR-3和iNOS在人乳腺癌淋巴管的表达

目的检测乳腺癌组织血管内皮生长因子-C(VEGF-C)及其受体(VEGFR-3)、iNOS基因表达的相关性及这三个基因mRNA表达水平与淋巴管密度(LVD)的相关性,为阐明乳腺癌淋巴管生成的分子机理提供实验依据。方法RT-PCR检测乳腺癌组织及正常乳腺组织VEGF-C、VEGFR-3、iNOSmRNA的表达水平;免疫组织化学染色法检测淋巴管内皮细胞上VEGFR-3的表达,测定淋巴管密度。结果乳腺癌LVD为20.35±4.23,显著高于正常对照组(P<0.05);乳腺癌组织VEGF-C、VEGFR-3、iNOSmRNA三者的表达率分别为74.0%、84.0%、82.0%,显著高于正常对照组(P<0.05);VEGF-C、VEGFR-3、iNOS阳性组中LVD分别为21.34±3.45、18.54±4.68、17.43±4.76,显著高于对照组(P<0.05)。结论VEGF-C、VEGFR-3、iNOSmRNA表达与淋巴管密度之间呈正相关,并且3者之间的表达亦具有相关性,这些基因的表达增高可能在乳腺癌淋巴管生成过程中具有重要作用。     

VEGF-A和C在人结肠癌淋巴管生成和淋巴道转移中的作用

目的分析血管内皮生长因子(VEGF)-A和VEGF-C在人结肠癌组织的表达及与结肠癌淋巴管生成和淋巴道转移的关系。方法取人结肠癌组织91例,应用免疫组化方法检测VEGF-A和VEGF-C在结肠癌组织中的表达。应用D2-40标记结肠癌组织的淋巴管,观察结肠癌组织的淋巴管生成情况。结果结肠癌组织中VEGF-A和VEGF-C的表达水平明显高于正常组织,VEGF-A和VEGF-C表达阳性的结肠癌组织的淋巴管密度(LVD)明显高于阴性组织,VEGF-A和VEGF-C的表达及LVD均与淋巴结转移及Duke's分期相关。结论结肠癌组织VEGF-A和VEGF-C过表达与结肠癌的淋巴管生成和淋巴道转移相关。     

Smad4的表达与胰腺癌淋巴管生成之间的关系

目的观察血管内皮生长因子(VEGF)-C和Smad 4在胰腺癌组织内的表达情况,分析VEGF-C和Smad 4的表达与胰腺癌淋巴管生成及淋巴结转移之间的关系。方法取胰腺癌病例52例,其中,无淋巴结转移组12例,淋巴结转移组40例。应用免疫组化和Western blot技术检测VEGF-C和Smad4在胰腺癌组织内的表达情况。以D2-40作为淋巴管内皮标记物,观察胰腺癌组织内淋巴管生成情况。结果 VEGF-C主要表达于胰腺癌细胞胞质内,在淋巴结转移组的表达水平明显高于无淋巴结转移组。Smad4表达于胰腺癌细胞胞质和胞核内,在无淋巴结转移组的表达水平明显高于淋巴结转移组,Smad4表达阳性组淋巴管数密度明显低于Smad4表达阴性组(=0.02)。Smad4的表达与VEGF-C的表达呈显著的负相关性。结论 VEGF-C在胰腺癌淋巴管的发生及淋巴结转移中发挥重要作用,Smad4可能通过调节VEGF-C蛋白的表达抑制胰腺癌淋巴管生成和淋巴结转移。     

喉癌中VEGF-C的表达与淋巴管生成及预后关系的研究

目的研究血管内皮生长因子-C(vessel endothelium growth factor C,VEGF-C)在喉癌组织的表达与临床病理特征的关系,探讨VEGF-C与喉癌淋巴管生成及预后的关系。方法以45例经病理确诊的喉癌组织为实验组,以20例喉良性病变组织为对照组,采用免疫组化SP法对上述组织中VEGF-C蛋白的表达进行分析,同时采用5′-核苷酸酶-碱性磷酸酶双重染色法(5′-Nase-ALP)计数淋巴管密度(LVD),并结合临床病理特征和生存资料进行相关分析。结果①在喉癌组织中VEGF-C的阳性率为37.8%,明显高于在正常喉组织内的表达水平(P<0.05);②VEGF-C表达与瘤内和瘤周LVD、淋巴结转移、淋巴管浸润显著相关(P<0.05),而与年龄、性别、肿瘤部位及组织学分级无关(P>0.05);③Kaplan-Meier生存曲线分析表明VEGF-C的表达与生存率呈负相关(P<0.05)。结论 VEGF-C促进喉癌淋巴管生成和转移,VEGF-C可以成为判断喉癌预后的生物学指标之一。     

VEGF-C和Smad4在结肠癌淋巴管生成和淋巴道转移中的作用

目的研究血管内皮生长因子C(VEGF-C)和Smad4对结肠癌淋巴管生成、淋巴结转移的影响。方法应用免疫组化方法检测79例人结肠癌组织中VEGF-C、VEGFR-3、TGF-β1、TβR-Ⅱ和Smad4的表达和淋巴管密度(LVD)。结果 LVD与VEGF-C表达水平呈正相关、与Smad4表达呈负相关;有淋巴结转移的人结肠癌组织VEGF-C表达水平高于无淋巴结转移者(<0.001)、Smad4表达低于无淋巴结转移者(=0.001);VEGF-C表达与Smad4表达呈负相关(<0.001,R=-0.507)。结论在结肠癌组织中VEGF-C和Smad4与淋巴管生成、淋巴道转移相关。     

血管内皮生长因子C和Smad4的表达与膀胱癌淋巴管生成之间的关系

目的观察血管内皮生长因子-C(VEGF-C)和Smad4在膀胱癌的表达,分析VEGF-C和Smad4的表达与膀胱癌淋巴管生成及膀胱癌进展之间的关系。方法取膀胱癌病例56例,其中浅表性膀胱癌(Tis,Ta,T1)32例,浸润性膀胱癌(T2以上)24例。应用免疫组化法和Western blot技术观察VEGF-C和Smad4在膀胱癌组织内的表达。以D2-40作为淋巴管内皮特异性标记物,检测膀胱癌组织内的淋巴管密度(LVD)。结果VEGF-C表达于肿瘤细胞的胞浆内,Smad4表达于肿瘤细胞的胞浆和胞核内。VEGF-C的表达水平与膀胱癌淋巴管密度呈正相关(P0.05),Smad4的表达水平与膀胱癌淋巴管密度呈负相关(P0.05)。VEGF-C和Smad4的表达呈负相关,VEGF-C的高表达和Smad4的低表达与膀胱癌淋巴管生成之间呈显著的相关性。Western blot检测结果表明,VEGF-C在浸润性膀胱癌组织内的表达量与其在浅表性膀胱癌组织内的表达量未见显著差异(P0.05),而Smad4在浅表性膀胱癌组织内的表达量明显高于其在浸润性膀胱癌组织内的表达量(P0.05)。结论 VEGF-C和Smad4在膀胱癌组织内表达水平呈负相关,Smad4可能通过调节VEGF-C蛋白的表达而抑制膀胱癌淋巴管生成。     

The biological significance of lymphangiogenesis in human tumours

Increasing evidence indicates that lymphangiogenesis in cancer is an important factor in promoting tumour progression and metastasis. The discovery of immunohistochemical markers for lymphatic vessels' identification as well as the characterization of lymphatic-specific growth factors and receptors afforded insight into the mechanisms involved in new lymphatic vessel formation and the process of lymphatic-borne metastasis. Quantitative assessment of lymphangiogenesis in malignant tumours has emerged as a promising prognostic indicator, although there are conflicting results on the impact of lymphatic vessel density to predict lymph nodal metastases and overall survival. Solid tumours were recently found to induce new lymphatic vessel growth in draining lymph nodes before the onset of metastasis and therefore lymphangiogenesis in the lymph nodes has gained great interest. This review highlights advances in our understanding of the mechanisms by which lymphangiogenesis in tumours and lymph nodes enhances metastases and reports the potential implications of these developments in cancer therapeutics.     

VEGFR-3与肿瘤淋巴转移的研究进展

肿瘤转移通常是人类癌症致死的主要原因之一.淋巴转移是肿瘤特别是癌的常见转移途径,肿瘤细胞转移至淋巴结通常作为肿瘤转移的信号,同时也是患者预后的重要指标.在肿瘤转移过程中,血管内皮生长因子及其受体家族发挥了重要的作用.尤其是淋巴内皮特异性的受体--血管内皮生长因子受体3(VEGFR-3)及其配体VEGF-C/D在促进淋巴管生长具有关键的作用.本文就VEGFR-3与肿瘤淋巴转移的研究进展进行综述.     

Lysophosphatidic acid induces lymphangiogenesis and IL-8 production in vitro in human lymphatic endothelial cells

The bioactive phospholipid lysophosphatidic acid (LPA) and its receptors LPA(1-3) are aberrantly expressed in many types of human cancer. LPA has been reported to induce tumor cell proliferation, migration, and cytokine production. However, whether LPA exerts an effect on lymphatic endothelial cells (LECs) or on lymphangiogenesis, a process of new lymphatic vessel formation that is associated with increased metastasis and poor prognosis in cancer patients, has been unknown. Here, we show that LPA induces cell proliferation, survival, migration, and tube formation, and promotes lymphangiogenesis in vitro in human dermal LECs. In addition, LPA induces IL-8 expression by enhancing IL-8 promoter activity via activation of the NF-κB pathway in LECs. Using IL-8 siRNA and IL-8 neutralizing antibody, we revealed that IL-8 plays an important role in LPA-induced lymphangiogenesis in vitro. Moreover, using siRNA inhibition, we discovered that LPA-induced lymphangiogenesis in vitro and IL-8 production are mediated via the LPA(2) receptor in LECs. Finally, using human sentinel afferent lymphatic vessel explants, we demonstrated that LPA up-regulates IL-8 production in the LECs of lymphatic endothelia. These studies provide the first evidence that LPA promotes lymphangiogenesis and induces IL-8 production in LECs; we also reveal a possible new role of LPA in the promotion of tumor progression, as well as metastasis, in different cancer types.     

Lymphangiogenesis and lymphatic metastasis in breast cancer

Lymphatic metastasis is the main prognostic factor for survival of patients with breast cancer and other epithelial malignancies. Mounting clinical and experimental data suggest that migration of tumor cells into the lymph nodes is greatly facilitated by lymphangiogenesis, a process that generates new lymphatic vessels from pre-existing lymphatics with the aid of circulating lymphatic endothelial progenitor cells. The key protein that induces lymphangiogenesis is vascular endothelial growth factor receptor-3 (VEGFR-3), which is activated by vascular endothelial growth factor-C and -D (VEGF-C and VEGF-D). These lymphangiogenic factors are commonly expressed in malignant, tumor-infiltrating and stromal cells, creating a favorable environment for generation of new lymphatic vessels. Clinical evidence demonstrates that increased lymphatic vessel density in and around tumors is associated with lymphatic metastasis and reduced patient survival. Recent evidence shows that breast cancers induce remodeling of the local lymphatic vessels and the regional lymphatic network in the sentinel and distal lymph nodes. These changes include an increase in number and diameter of tumor-draining lymphatic vessels. Consequently, lymph flow away from the tumor is increased, which significantly increases tumor cell metastasis to draining lymph nodes and may contribute to systemic spread. Collectively, recent advances in the biology of tumor-induced lymphangiogenesis suggest that chemical inhibitors of this process may be an attractive target for inhibiting tumor metastasis and cancer-related death. Nevertheless, this is a relatively new field of study and much remains to be established before the concept of tumor-induced lymphangiogenesis is accepted as a viable anti-metastatic target. This review summarizes the current concepts related to breast cancer lymphangiogenesis and lymphatic metastasis while highlighting controversies and unanswered questions.     

Targeting COX-2 and EP4 to control tumor growth, angiogenesis, lymphangiogenesis and metastasis to the lungs and lymph nodes in a breast cancer model

We reported that cyclo-oxygenase (COX)-2 expression in human breast cancer stimulated cancer cell migration and invasiveness, production of vascular endothelial growth factor (VEGF)-C and lymphangiogenesis in situ, largely from endogenous PGE2-mediated stimulation of prostaglandin E (EP)1 and EP4 receptors, presenting them as candidate therapeutic targets against lymphatic metastasis. As human breast cancer xenografts in immuno-compromised mice have limitations for preclinical testing, we developed a syngeneic murine breast cancer model of spontaneous lymphatic metastasis mimicking human and applied it for mechanistic and therapeutic studies. We tested the roles of COX-2 and EP receptors in VEGF-C and -D production by a highly metastatic COX-2 expressing murine breast cancer cell line C3L5. These cells expressed all EP receptors and produced VEGF-C and -D, both inhibited with COX-2 inhibitors or EP4 (but not EP1, EP2 or EP3) antagonists. C3H/HeJ mice, when implanted SC in both inguinal regions with C3L5 cells suspended in growth factor-reduced Matrigel, exhibited rapid tumor growth, tumor-associated angiogenesis and lymphangiogenesis (respectively measured with CD31 and LYVE-1 immunostaining), metastasis to the inguinal and axillary lymph nodes and the lungs. Chronic oral administration of COX-1/COX-2 inhibitor indomethacin, COX-2 inhibitor celecoxib and an EP4 antagonist ONO-AE3-208, but not an EP1 antagonist ONO-8713 at nontoxic doses markedly reduced tumor growth, lymphangiogenesis, angiogenesis, and metastasis to lymph nodes and lungs. Residual tumors in responding mice revealed reduced VEGF-C and -D proteins, AkT phosphorylation and increased apoptotic/proliferative cell ratios consistent with blockade of EP4 signaling. We suggest that EP4 antagonists deserve clinical testing for chemo-intervention of lymphatic metastasis in human breast cancer.     

Tumor and lymph node lymphangiogenesis--impact on cancer metastasis

The extent of lymph node (LN) metastasis is a major determinant for the staging and the prognosis of most human malignancies and often guides therapeutic decisions. Although the clinical significance of LN involvement is well documented, little has been known about the molecular mechanisms that promote tumor spread via lymphatic vessels to sentinel and distal LN and beyond. However, recent discoveries have identified novel lymphatic-specific markers, and the newly discovered lymphangiogenesis factors vascular endothelial growth factor-C (VEGF-C) and VEGF-D were found to promote tumor-associated lymphatic vessel growth in mouse tumor models, leading to enhanced tumor spread to sentinel LN. Our recent findings indicate that VEGF-A also acts as a potent tumor lymphangiogenesis factor that promotes lymphatic tumor spread. VEGF-A overexpressing primary tumors induced sentinel LN lymphangiogenesis even before metastasizing and maintained their lymphangiogenic activity after metastasis to draining LN. Our recent studies showed that primary human melanomas that later metastasized were characterized by increased lymphangiogenesis and that the degree of tumor lymphangiogenesis can serve as a novel predictor of LN metastasis and overall patient survival, independently of tumor thickness. Tumor lymphangiogenesis also significantly predicted the presence of sentinel LN metastases at the time of surgical excision of the primary melanoma. Together, these findings suggest that tumor lymphangiogenesis actively contributes to cancer dissemination, that blockade of lymphatic vessel growth might inhibit tumor metastasis to LN, and that the extent of tumor-associated lymphangiogenesis could serve as a novel, prognostic parameter for the metastatic risk of human cancers.     

Biology of the lymphatic marker LYVE-1 and applications in research into lymphatic trafficking and lymphangiogenesis

The pace of research into the lymphatic system continues to accelerate with the availability of new molecular markers. One such marker, LYVE-1, the lymphatic receptor for the extracellular matrix mucopolysaccharide hyaluronan, has been a key component of many important studies on embryonic and tumour-induced lymphangiogenesis, and continues to be used for the detection and isolation of lymphatic endothelial cells. However, LYVE-1 is interesting in its own right. Being a member of the Link protein family whose only other major hyaluronan receptor is directly involved in leukocyte migration and tumour metastasis, LYVE-1 is already implicated in the trafficking of cells within lymphatic vessels and lymph nodes. The current challenge is to determine the precise roles played by LYVE-1 and other scavenger type receptors in the immune functions of the lymphatics as well as to use LYVE-1 and other markers to investigate the way in which tumours exploit lymphatic vessels for metastasis.     

VEGF-C在淋巴管生成及乳腺癌淋巴道转移中的作用

目的： 探讨阻断VEGF-C/Flt-4调控系统对淋巴管生成和乳腺癌淋巴道转移的影响。方法： 体外培养胎牛胸导管内皮细胞，观察VEGF-C和抗Flt-4抗体对淋巴管内皮细胞增殖的影响；设计合成VEGF-C反义脱氧寡核苷酸（ASODN），体外实验观察其对VEGF-C基因表达的影响；建立乳腺癌裸鼠原位移植瘤模型并观察ASODN对肿瘤淋巴管生成及肿瘤生长转移的影响。结果： 加入前列腺癌细胞PC3(高表达VEGF-C)上清后，淋巴管内皮细胞增殖活跃；加入抗Flt-4抗体后各时段细胞计数均明显少于其它各组。体外实验RT-PCR及 Western blotting显示ASODN作用的MCF-7细胞组VEGF-C mRNA及蛋白表达均低于对照组。体内RT-PCR检测表明ASODN组移植瘤VEGF-C mRNA表达明显受抑制；5-Nase-ALPase双重酶组织化学法结果显示ASODN组移植瘤的淋巴管生成明显减少；ASODN组肿瘤生长速度较对照组缓慢，且肿瘤体积、淋巴结转移明显低于对照组。结论： VEGF-C/Flt-4调控系统与乳腺癌组织的淋巴管生成及肿瘤的淋巴道转移密切相关。阻断淋巴管内皮细胞Flt-4表达，可在一定程度上抑制肿瘤细胞诱导的淋巴管内皮细胞增殖；ASODN通过下调乳腺癌VEGF-C的表达，减少肿瘤淋巴管的生成及淋巴结转移。