LYVE-1在肿瘤淋巴管生成领域的研究

淋巴管生成可能是肿瘤转移有效的途径之一,但淋巴管生成的基本生理学知识明显落后于血管生成,主要归于缺乏鉴别淋巴管的特异性标志物。最近,随着淋巴管内皮透明质酸受体-1（lymphatic vessel endothelial HA receptor-1,LYVE-1）作为淋巴管内皮标志物被发现,正开辟淋巴管生成、肿瘤淋巴转移研究的新领域。     

肿瘤淋巴管生成的研究进展

恶性肿瘤除了浸润性生长侵及周围组织外,还可发生远处转移,这是影响疗效,致患者死亡的主要因素。血道转移和淋巴转移是实体肿瘤最重要的两条转移途径。然而,直到淋巴内皮细胞特异性标志物的相继发现后,对淋巴管生成的相关研究才得以蓬勃开展起来。本文就主要的淋巴管内皮标记物和淋巴管生成调节因子及相关治疗的新进展做一相关综述。     

肿瘤转移中的淋巴管新生

肿瘤转移是肿瘤致死的重要原因,临床发现,肿瘤最初的生长主要通过诱导血管新生(angiogenesis)来提供所需的营养,但是肿瘤转移的主要途径并不是通过新生血管,而是通过肿瘤诱导的新生淋巴管进行转移.淋巴管新生(1ymphangiogenesis)是在原来淋巴管的基础上长出新的毛细淋巴管的过程,毛细淋巴管仅由一层内皮细胞组成,几乎不被周细胞或平滑肌细胞包被,它是肿瘤细胞转移和扩散的重要途径.因此,肿瘤细胞通过新生淋巴管转移至淋巴结可被视为肿瘤转移的预后指标,抑制肿瘤的淋巴管新生被认为是肿瘤诊断和决定医治的重要治疗方法.但是由于缺乏淋巴特异性标记和对淋巴管新生知识的匮乏,淋巴管新生并没有像血管新生那样得到关注.近年来,淋巴管新生信号途径的阐明,淋巴内皮细胞(1ymphatic endothelial cell,LEC)分子标记物如Prox-l、LYVE-1和podoplanin等的发现和淋巴内皮细胞的成功分离和培养,使得淋巴管新生方面的研究更深入.     

淋巴管内皮细胞在淋巴管生成异常相关疾病中的研究进展

淋巴管系统在组织液稳态、免疫监视和脂质吸收中起关键性作用.淋巴管内皮细胞是淋巴管的主要组成结构,主要参与维持体液平衡、调节淋巴细胞再循环和免疫反应等生理过程.因此,淋巴管内皮细胞异常可导致淋巴管功能障碍和淋巴管生成异常,进而引起多种疾病,如淋巴水肿、炎症、肿瘤转移和心血管疾病等.然而,淋巴管内皮细胞在淋巴管生成异常相关...     

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。     

VEGF-C与肿瘤细胞转移

血管内皮生长因子C(VEGF—C)通过与其受体VEGFR2／VEGFR3结合,影响到肿瘤生长、肿瘤外周血管生成、淋巴血管形成、肿瘤表面积,促进肿瘤细胞从原发部位通过血液以及淋巴系统转移到其他器官,是引起肿瘤治疗失败的主要原因之一。阻碍VEGF—C与受体的结合可以降低肿瘤细胞的转移性,为肿瘤治疗提供了1个新的靶点。     

VEGF-D表达与下咽癌组织淋巴管生成及预后的相关性

目的探讨血管内皮生长因子-D(Vascular endothelial growth factor D,VEGF-D)在下咽癌组织中的表达规律、与淋巴管密度(LVD)、淋巴结转移之间的关系及其在下咽癌预后中的意义。方法采用Western-bolt方法检测6例下咽癌和6例正常下咽组织中VEGF-D蛋白的表达情况,以45例经病理确诊的下咽癌组织为实验组,15例下咽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-D蛋白的表达进行分析,同时采用5′-核苷酸酶染色法(5′-Nase)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①Western-bolt结果显示下咽癌组织中VEGF-D的表达量较正常组织明显增加。②在下咽癌组织中VEGF-D的阳性率为44.4%,明显高于在良性病变组织的表达水平(P<0.05)。③VEGF-D表达与LVD、淋巴结转移、淋巴管浸润显著相关(P<0.05),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VEGF-D的表达与生存率不相关(P>0.05)。结论 VEGF-D促进下咽癌淋巴管生成和淋巴管转移,但与下咽癌预后不相关。     

血管内皮生长因子-C与肿瘤细胞转移

血管内皮生长因子(vascular endothelial growth factor,VEGF)C通过与其受体VEGFR2／VEGFR3结合,影响到肿瘤生长、肿瘤外周血管生成、淋巴血管形成、肿瘤表面积,促进肿瘤细胞从原发部位通过血液以及淋巴系统转移到其他器官,是引起肿瘤治疗失败的主要原因之一。阻碍VEGF-C与受体的结合可以降低肿瘤细胞的转移性,为肿瘤治疗提供了一个新的靶点。     

VEGF与肿瘤血管生成及其在抗肿瘤药物开发中的应用

肿瘤血管生成在肿瘤的形成和转移过程中起到很重要的作用,众多的血管生成因子和抑制因子在肿瘤血管生成中起到调控作用,而血管生成因子（VEGF）是其中很重要的一类,通过研究其在肿瘤血管形成过程的调节机制,找到了一条有效的预防和治疗肿瘤的新途径。本文就肿瘤血管生成、VEGF家族的特性、VEGF在抗肿瘤药物开发中的应用做一综述。     

小鼠膈腹膜淋巴孔和膈淋巴管的发育

应用透射电镜、扫描电镜和酶组织化学方法,研究胚胎期和出生后不同时期小鼠膈腹膜淋巴孔（PLS）和膈淋巴管的发生和发育,并用Elescope计算机图像处理技术对PLS进行定量分析。结果发现：胚胎13天时,膈腹膜仅由扁平形间皮细胞（FMC）组成;胚胎15天时,FMC间出现立方形间皮细胞（CMC）和早期腹膜淋巴孔（NLS）;胚胎18天时,膈毛细淋巴管出现,台盼蓝吸收试验显示NLS无物质吸收功能;出生后1天（PND1）,膈毛细淋巴管内皮细胞向PLS伸出胞质突起,并横跨CMC下结缔组织纤维和基底膜,形成腹膜下小管。后者与PLS沟通,建立了腹膜腔内物质转归通路。台盼蓝吸收试验表明,出生后PLS具有物质吸收功能,即为成熟腹膜淋巴孔（MLS）。PND5,立方细胞嵴（CMCR）发生,膈毛细淋巴管数量增多。PND10,大量立方细胞嵴融合,形成条带状分布的立方细胞区域,其上分布有大量MLS。随着发育进展,MLS平均面积和平均分布密度逐渐增大,且随着膈淋巴管的发育,吸收功能逐渐增强。     

Emerging roles for lymphatics in acute kidney injury: Beneficial or maleficent?

Acute kidney injury, a sudden decline in renal filtration, is a surprisingly common pathology resulting from ischemic events, local or systemic infection, or drug-induced toxicity in the kidney. Unchecked, acute kidney injury can progress to renal failure and even recovered acute kidney injury patients are at an increased risk for developing future chronic kidney disease. The initial extent of inflammation, the specific immune response, and how well inflammation resolves are likely determinants in acute kidney injury-to-chronic kidney disease progression. Lymphatic vessels and their roles in fluid, solute, antigen, and immune cell transport make them likely to have a role in the acute kidney injury response. Lymphatics have proven to be an attractive target in regulating inflammation and immunomodulation in other pathologies: might these strategies be employed in acute kidney injury? Acute kidney injury studies have identified elevated levels of lymphangiogenic ligands following acute kidney injury, with an expansion of the lymphatics in several models post-injury. Manipulating the lymphatics in acute kidney injury, by augmenting or inhibiting their growth or through targeting lymphatic-immune interactions, has met with a range of positive, negative, and sometimes inconclusive results. This minireview briefly summarizes the findings of lymphatic changes and lymphatic roles in the inflammatory response in the kidney following acute kidney injury to discuss whether renal lymphatics are a beneficial, maleficent, or a passive contributor to acute kidney injury recovery.     

Fucoxanthin inhibits tumour‐related lymphangiogenesis and growth of breast cancer

Tumour lymphangiogenesis plays an important role in promoting the growth and lymphatic metastasis of tumours. The process is associated with cell proliferation, migration and tube‐like structure formation in lymphatic endothelial cells (LEC), but no antilymphangiogenic agent is currently used in clinical practice. Fucoxanthin is a material found in brown algae that holds promise in the context of drug development. Fucoxanthin is a carotenoid with variety of pharmacological functions, including antitumour and anti‐inflammatory effects. The ability of fucoxanthin to inhibit lymphangiogenesis remains unclear. The results of experiments performed as part of this study show that fucoxanthin, extracted from Undaria pinnatifida (Wakame), inhibits proliferation, migration and formation of tube‐like structures in human LEC (HLEC). In this study, fucoxanthin also suppressed the malignant phenotype in human breast cancer MDA‐MB‐231 cells and decreased tumour‐induced lymphangiogenesis when used in combination with a conditional medium culture system. Fucoxanthin significantly decreased levels of vascular endothelial growth factor (VEGF)‐C, VEGF receptor‐3, nuclear factor kappa B, phospho‐Akt and phospho‐PI3K in HLEC. Fucoxanthin also decreased micro‐lymphatic vascular density (micro‐LVD) in a MDA‐MB‐231 nude mouse model of breast cancer. These findings suggest that fucoxanthin inhibits tumour‐induced lymphangiogenesis in vitro and in vivo, highlighting its potential use as an antilymphangiogenic agent for antitumour metastatic comprehensive therapy in patients with breast cancer.     

Tumor associated osteoclast-like giant cells promote tumor growth and lymphangiogenesis by secreting vascular endothelial growth factor-C

Tumors with osteoclast-like giant cells (OGCs) have been reported in a variety of organs and exert an invasive and prometastatic phenotype, but the functional role of OGCs in the tumor environment has not been fully clarified. We established tumors containing OGCs to clarify the role of OGCs in tumor phenotype. A mixture of HeLa cells expressing macrophage colony-stimulating factor (M-CSF, HeLa-M) and receptor activator of nuclear factor-κB ligand (RANKL, HeLa-R) effectively supported the differentiation of osteoclast-like cells from bone marrow macrophages in vitro. Moreover, a xenograft study showed OGC formation in a tumor composed of HeLa-M and HeLa-R. Surprisingly, the tumors containing OGCs were significantly larger than the tumors without OGCs, although the growth rates were not different in vitro. Histological analysis showed that lymphangiogenesis and macrophage infiltration in the tumor containing OGCs, but not in other tumors were accelerated. According to quantitative PCR analysis, vascular endothelial growth factor (VEGF)-C mRNA expression increased with differentiation of osteoclast-like cells. To investigate whether VEGF-C expression is responsible for tumor growth and macrophage infiltration, HeLa cells overexpressing VEGF-C (HeLa-VC) were established and transplanted into mice. Tumors composed of HeLa-VC mimicked the phenotype of the tumors containing OGCs. Furthermore, the vascular permeability of tumor microvessels also increased in tumors containing OGCs and to some extent in VEGF-C-expressing tumors. These results suggest that macrophage infiltration and vascular permeability are possible mediators in these tumors. These findings revealed that OGCs in the tumor environment promoted tumor growth and lymphangiogenesis, at least in part, by secreting VEGF-C.     

Tumor microenvironment abnormalities: causes, consequences, and strategies to normalize

A solid tumor is an organ-like entity comprised of neoplastic cells and non-transformed host stromal cells embedded in an extracellular matrix. The expression of various genes is influenced by interactions among these cells, surrounding matrix, and their local physical and biochemical microenvironment. The products encoded by these genes, in turn, control the pathophysiological characteristics of the tumor, and give rise to the abnormal organization, structure, and function of tumor blood vessels. These abnormalities contribute to heterogeneous blood flow, vascular permeability, and microenvironment. Proliferating tumor cells produce solid stress which compresses blood and lymphatic vessels. As a result of vessel leakiness and lack of functional lymphatics, interstitial fluid pressure is significantly elevated in solid tumors. Each of these abnormalities forms a physiological barrier to the delivery of therapeutic agents to tumors. Furthermore, the metabolic microenvironment in tumors such as hypoxia and acidosis hinder the efficacy of anti-tumor treatments such as radiation therapy and chemotherapy. A judicious application of anti-angiogenic therapy has the potential to overcome these problems by normalizing the tumor vessels and making them more efficient for delivery of oxygen and drugs. Combined anti-angiogenic and conventional therapies have shown promise in the clinic.     

Lymphatic biomarkers in primary melanomas as predictors of regional lymph node metastasis and patient outcomes

Recently developed lymphatic‐specific immunohistochemical markers can now be utilized to assess intratumoral and/or peritumoral lymphatic vessel density (LVD), to detect lymphatic vessel invasion (LVI) by melanoma cells and to identify lymphatic marker expression in melanoma cells themselves. We systematically reviewed the available evidence for the expression of lymphatic markers as predictors of regional node metastasis and survival in melanoma patients. The currently available evidence suggests that LVD (particularly in a peritumoral location) and LVI are predictors of sentinel node metastasis and poorer survival. Nevertheless, adherence to international guidelines in the conduct and reporting of the studies was generally poor, with wide methodologic variations and heterogeneous findings. Larger, carefully conducted and well‐reported studies that confirm these preliminary findings are required before it would be appropriate to recommend the routine application of costly and time‐consuming immunohistochemistry for lymphatic markers in the routine clinical assessment of primary cutaneous melanomas.     

Tumor cell-mediated neovascularization and lymphangiogenesis contrive tumor progression and cancer metastasis

Robust neovascularization and lymphangiogenesis have been found in a variety of aggressive and metastatic tumors. Endothelial sprouting angiogenesis is generally considered to be the major mechanism by which new vasculature forms in tumors. However, increasing evidence shows that tumor vasculature is not solely composed of endothelial cells (ECs). Some tumor cells acquire processes similar to embryonic vasculogenesis and produce new vasculature through vasculogenic mimicry, trans-differentiation of tumor cells into tumor ECs, and tumor cell–EC vascular co-option. In addition, tumor cells secrete various vasculogenic factors that induce sprouting angiogenesis and lymphangiogenesis. Vasculogenic tumor cells actively participate in the formation of vascular cancer stem cell niche and a premetastatic niche. Therefore, tumor cell-mediated neovascularization and lymphangiogenesis are closely associated with tumor progression, cancer metastasis, and poor prognosis. Vasculogenic tumor cells have emerged as key players in tumor neovascularization and lymphangiogenesis and play pivotal roles in tumor progression and cancer metastasis. However, the mechanisms underlying tumor cell-mediated vascularity as they relate to tumor progression and cancer metastasis remain unclear. Increasing data have shown that various intrinsic and extrinsic factors activate oncogenes and vasculogenic genes, enhance vasculogenic signaling pathways, and trigger tumor neovascularization and lymphangiogenesis. Collectively, tumor cells are the instigators of neovascularization. Therefore, targeting vasculogenic tumor cells, genes, and signaling pathways will open new avenues for anti-tumor vasculogenic and metastatic drug discovery. Dual targeting of endothelial sprouting angiogenesis and tumor cell-mediated neovascularization and lymphangiogenesis may overcome current clinical problems with anti-angiogenic therapy, resulting in significantly improved anti-angiogenesis and anti-cancer therapies.     

Hyaluronan promotes tumor lymphangiogenesis and intralymphantic tumor growth in xenografts

Hyaluronan （HA）, a high molecular weight glycosaminoglycan in the extracellular matrix, has been implicated in the promotion of malignant phenotypes, including tumor angiogenesis. However, little is known about the effect of HA on tumor-associated lymphangiogenesis. In this study, mouse hepatocellular carcinoma Hca-F cells combined with or without HA were injected subcutaneously into C3H/Hej mice, then angiogenesis and lymphangiogenesis of implanted tumors were examined by immunostaining for plateletendothelial cell adhesion molecule-1 and lymphatic vascular endothelial hyaluronan receptor-1 respectively. Interestingly, we found HA promotes tumor lymphangiogenesis and the occurrence of intratumoral lymphatic vessels, but has little effect on tumor angiogenesis. Moreover, HA also promotes intralymphatic tumor growth, although it is not sufficient to potentiate lymphatic metastasis. These results suggest that HA, which is elevated in most malignant tumor stroma, may also play a role in tumor progression by promoting lymphangiogenesis.     

Lymphangiogenesis in vitro: Formation of lymphatic capillary-like channels from confluent monolayers of lymphatic endothelial cells

Summary Lymphatic endothelial cells grown long term in culture form lymphatic capillarylike tubes. Examination by light and transmission electron microscopy showed that these structures were closed loops composed of one to several cells connected by intercellular junction to form a luminal space. This first demonstration of lymphangiogenesis in confluent monolayer cultures of lymphatic endothelial cells (a) showed that collagen type I accelerated lymphatic capillary tube formation, whereas fibronectin and matrigel had no effect; b) provided a model to study lymphatic endothelial cell function and differentiation; and c) offered a possibility to distinguish differences between the process of lymphangiogenesis and angiogenesis by testing various factors and conditions that effect endothelial cell behavior.