Tumor-induced activation of lymphatic endothelial cells via vascular endothelial growth factor receptor-2 is critical for prostate cancer lymphatic metastasis

Prostate cancer disseminates initially and primarily to regional lymph nodes. However, the nature of interactions between tumor cells and lymphatic endothelial cells (LEC) is poorly understood. In the current study, we have isolated prostate LECs and developed a series of two-dimensional and three-dimensional in vitro coculture systems and in vivo orthotopic prostate cancer models to investigate the interactions of prostate cancer cells with prostate LECs. In vitro, highly lymph node metastatic prostate cancer cell lines (PC-3 and LNCaP) and their conditioned medium enhanced prostate LEC tube formation and migration, whereas poorly lymph node metastatic prostate cancer cells (DU145) or normal prostate epithelial cells (RWPE-1) or their conditioned medium had no effect. In vivo, the occurrence of lymphatic invasion and lymph node metastasis was observed in PC-3 and LNCaP xenografts but not in DU145 xenografts. Furthermore, vascular endothelial growth factor (VEGF) receptor (VEGFR)-2 is expressed by prostate LECs, and its ligands VEGF-A, VEGF-C, and VEGF-D are up-regulated in highly lymph node metastatic prostate cancer cells. Recombinant VEGF-A and VEGF-C, but not VEGF-C156S, potently promoted prostate LEC tube formation, migration, and proliferation in vitro, indicating that signaling via VEGFR-2 rather than VEGFR-3 is involved in these responses. Consistent with this, blockade of VEGFR-2 significantly reduced tumor-induced activation of LECs. These results show that the interaction of prostate tumor cells with LECs via VEGFR-2 modulates LEC behavior and is related to the ability of tumor cells to form lymph node metastases.     

Soluble vascular endothelial growth factor receptor-3 suppresses lymphangiogenesis and lymphatic metastasis in bladder cancer

Background  

Most bladder cancer patients experience lymphatic metastasis in the course of disease progression, yet the relationship between lymphangiogenesis and lymphatic metastasis is not well known. The aim of this study is to elucidate underlying mechanisms of how expanded lymphatic vessels and tumor microenvironment interacts each other and to find effective therapeutic options to inhibit lymphatic metastasis.     

Sunitinib inhibits lymphatic endothelial cell functions and lymph node metastasis in a breast cancer model through inhibition of vascular endothelial growth factor receptor 3

Introduction  

Metastasis is a common event and the main cause of death in cancer patients. Lymphangiogenesis refers to the formation of new lymphatic vessels and is thought to be involved in the development of metastasis. Sunitinib is a multi-kinase inhibitor that blocks receptor tyrosine kinase activity, including that of vascular endothelial growth factor receptors (VEGFRs). Although sunitinib is a clinically available angiogenesis inhibitor, its effects on lymphangiogenesis and lymph node metastasis remain unclear. The purpose of this study was to investigate the effects of sunitinib on vascular endothelial growth factor receptor 3 (VEGFR-3) and a related event, lymphangiogenesis.     

Tumor-secreted vascular endothelial growth factor-C is necessary for prostate cancer lymphangiogenesis, but lymphangiogenesis is unnecessary for lymph node metastasis

Dissemination to draining lymph nodes is a frequent first step in prostate cancer metastasis. Although tumors metastasize to lymph nodes via the lymphatics, the importance of lymphangiogenesis in mediating the process remains controversial. Here, we inhibit intratumoral lymphangiogenesis in s.c. and surgical orthotopic implantation mouse models of human prostate cancer using several strategies. Stable expression of small interfering RNAs (siRNA) targeted against human vascular endothelial growth factor-C (VEGF-C) in PC-3 cells reduced intratumoral lymphatics by 99% in s.c. tumors, indicating that tumor-secreted VEGF-C is necessary for lymphangiogenesis. Expression of siRNAs against human VEGF-A somewhat reduced tumor lymphangiogenesis. Secretion of a soluble VEGF receptor-3/Flt4 fusion protein by PC-3 cells reduced intratumoral lymphatics by 100% in s.c. tumors. Combination of soluble Flt4 and VEGF-C siRNA yielded >92% reduction of intratumoral lymphatics in orthotopic prostate tumors. However, metastasis to lymph nodes was not significantly affected regardless of intratumoral lymphatic vessel density. The abundance of marginal lymphatics at the tumor-stromal interface was unchanged in orthotopic tumors whose intratumoral lymphatics were inhibited, suggesting that these marginal vessels could be sufficient for lymph node metastasis. Hematogenous metastasis (blood tumor burden, lung metastasis) correlated with degree of lymph node invasion. We also analyzed the lymphatics in spontaneous transgenic adenocarcinomas of the mouse prostate which metastasize to lymph nodes. Progression from well-differentiated prostate intraepithelial neoplasia to metastatic, undifferentiated adenocarcinoma was accompanied by loss of lymphatics. These results suggest that tumor-secreted VEGF-C and, to a lesser extent, VEGF-A, are important for inducing prostate cancer intratumoral lymphangiogenesis but are unnecessary for lymph node metastasis.     

Suppression of tumor lymphangiogenesis and lymph node metastasis by blocking vascular endothelial growth factor receptor 3 signaling

BACKGROUND: Vascular endothelial growth factor C (VEGF-C) stimulates tumor lymphangiogenesis (i.e., formation of lymphatic vessels) and metastasis to regional lymph nodes by interacting with VEGF receptor 3 (VEGFR-3). We sought to determine whether inhibiting VEGFR-3 signaling, and thus tumor lymphangiogenesis, would inhibit tumor metastasis. METHODS: We used the highly metastatic human lung cancer cell line NCI-H460-LNM35 (LNM35) and its parental line NCI-H460-N15 (N15) with low metastatic capacity. We inserted genes by transfection and established a stable N15 cell line secreting VEGF-C and a LNM35 cell line secreting the soluble fusion protein VEGF receptor 3-immunoglobulin (VEGFR-3-Ig, which binds VEGF-C and inhibits VEGFR-3 signaling). Control lines were transfected with mock vectors. Tumor cells were implanted subcutaneously into severe combined immunodeficient mice (n = 6 in each group), and tumors and metastases were examined 6 weeks later. In another approach, recombinant adenoviruses expressing VEGFR-3-Ig (AdR3-Ig) or beta-galactosidase (AdLacZ) were injected intravenously into LNM35 tumor-bearing mice (n = 14 and 7, respectively). RESULTS: LNM35 cells expressed higher levels of VEGF-C RNA and protein than did N15 cells. Xenograft mock vector-transfected LNM35 tumors showed more intratumoral lymphatic vessels (15.3 vessels per grid; 95% confidence interval [CI] = 13.3 to 17.4) and more metastases in draining lymph nodes (12 of 12) than VEGFR-3-Ig-transfected LNM35 tumors (4.1 vessels per grid; 95% CI = 3.4 to 4.7; P<.001, two-sided t test; and four lymph nodes with metastases of 12 lymph nodes examined). Lymph node metastasis was also inhibited in AdR3-Ig-treated mice (AdR3-Ig = 0 of 28 lymph nodes; AdLacZ = 11 of 14 lymph nodes). However, metastasis to the lungs occurred in all mice, suggesting that LNM35 cells can also spread via other mechanisms. N15 tumors overexpressing VEGF-C contained more lymphatic vessels than vector-transfected tumors but did not have increased metastatic ability. CONCLUSIONS: Lymph node metastasis appears to be regulated by additional factors besides VEGF-C. Inhibition of VEGFR-3 signaling can suppress tumor lymphangiogenesis and metastasis to regional lymph nodes but not to lungs.     

MMP9 induction by vascular endothelial growth factor receptor-1 is involved in lung-specific metastasis

The molecular mechanism of tissue-specific metastasis in tumors endogenously expressing members of the vascular endothelial growth factor (VEGF) family is not yet clear. Here we demonstrate that MMP9 is specifically induced in premetastatic lung endothelial cells and macrophages by distant primary tumors via VEGFR-1/Flt-1 tyrosine kinase (TK) and that it significantly promotes lung metastasis. In a genetic approach using mice, suppression of MMP9 induction by deletion of either VEGFR-1TK or MMP9 markedly reduced lung metastasis. Furthermore, the MMP9 levels in endothelial cells of normal lung lobes from patients carrying distant tumors were significantly elevated as compared with those from patients without tumors. Thus, a block of MMP9 induction via VEGFR-1 inhibition could be useful for the prevention of tumor metastasis in lung.     

Role of vascular endothelial growth factor C expression in the development of lymph node metastasis in gastric cancer.

Neogenesis of lymphatic vessel and lymphatic invasion is frequently found in the stroma of cancers, but the mechanisms of this phenomenon remain unclear. Vascular endothelial growth factor C (VEGF-C) is known to be the only growth factor for the lymphatic vascular system, and its receptor has been identified as Flt4. To clarify the mechanism of lymphatic invasion in cancer, we studied the expression of VEGF-C and flt4 genes in gastric cancer tissues. VEGF-C mRNA was mainly expressed in primary tumors (15 of 32; 47%), but the frequency of VEGF-C mRNA expression was low in normal mucosa (4 of 32; 13%). In primary tumors, there was a significant relationship between VEGF-C and flt4 mRNA expression. In contrast, Flt4 was mainly expressed on the lymphatic endothelial cells but not in cancer cells. A strong correlation was found between VEGF-C expression and lymph node status, lymphatic invasion, venous invasion, and tumor infiltrating patterns. Cancer cells in the lymphatic vessels frequently showed intracytoplasmic VEGF-C immunoreactivity. Furthermore, there was a close correlation between VEGF-C tissue status and the grade of lymph node metastasis. Patients with high expression of VEGF-C protein had a significantly poorer prognosis than did those in low VEGF-C expression group. By the Cox regression model, depth of wall invasion, lymph node metastasis, and VEGF-C tissue status emerged as independent prognostic parameters, and the VEGF-C tissue status was ranked third as an independent risk factor for death. These results strongly suggest that cancer cells producing VEGF-C may induce the proliferation and dilation of lymphatic vessels, resulting in the development of invasion of cancer cells into the lymphatic vessel and lymph node metastasis.     

Expression of Vascular Endothelial Growth Factor-C and Vascular Endothelial Growth Factor Receptor-3 in Ovarian Epithelial Tumors

Objective： To explore the role of vascular endothelial growth factor-C （VEGF-C） in the process of angiogenesis, lymphangiogenesis and lymphatic metastasis in epithelial ovarian tumors. Methods： In situ hybridization and immunohistochemical staining for VEGF-C were performed in 30 epithelial ovarian carcinomas, 9 borderline tumors and 26 benign tumors. Endothelial cells were immunostained with anti-VEGFR-3 pAb and anti-CD31 mAb, and VEGFR-3 positive vessels and microvessel density （MVD） were assessed by image analysis. Results： VEGF-C mRNA and protein expression were detected in cytoplasm of carcinoma cells. VEGF-C mRNA and protein expression in ovarian epithelial carcinomas were significantly higher than those in borderline tumors and benign tumors （P〈0.05 or P〈0.01）. In ovarian epithelial carcinomas, VEGF-C protein expression, VEGFR-3 positive vessels and MVD were significantly higher in the cases of clinical stage Ⅲ-Ⅳ and with lymph node metastasis than those of clinical stage Ⅰ-Ⅱ and without lymph node metastasis respectively （P〈0.05 or P〈0.01）. VEGFR-3 positive vessels and MVD were significantly higher in VEGF-C protein positive tumors than negative tumors （P〈0.05）. VEGFR-3 positive vessels was significantly correlated with MVD（P〈0.01）. Conclusion： VEGF-C might play a role in lymphatic metastasis via lymphangiogenesis and angiogenesis in epithelial ovarian tumors, and VBEGF-C could be used as a biologic marker of metastasis in ovarian epithelial tumors.     

Expression of vascular endothelial growth factor, matrix metalloproteinase-9 and E-cadherin in the process of lymph node metastasis in oesophageal cancer.

Lymph node metastasis is a strong independent prognostic factor for oesophageal cancer. The expression of matrix metalloproteinases (MMPs) and reduction of E-cadherin correlate with lymph node metastasis of oesophageal cancer. We previously reported that the expression of vascular endothelial growth factor (VEGF) is associated with lymph node metastasis. This study was designed to determine whether VEGF, MMP-9 and E-cadherin expression is stable or changes in the process of lymph node metastasis of oesophageal cancer. Using immunohistochemistry, we detected VEGF, MMP-9 and E-cadherin expression in paraffin-embedded specimens of oesophageal squamous cell carcinoma. We classified 134 primary tumours and 174 nodal metastases using two different criteria: the absence [Group N(-)] or presence [Group N(+)] of nodal metastasis, and the stage of metastasis--Early Stage (cancer cells < 50% of lymph node) or Late Stage (> or = 50%)--and compared the expression among two groups and among two stages. The expression rates of Group N(-), Group N(+), Early Stage and Late Stage are as follows: VEGF (49%, 74%, 60%, 33%), MMP-9 (76%, 65%, 95%, 69%) and E-cadherin (49%, 24%, 55%, 38%). VEGF expression was down-regulated in Late Stage lymph node metastasis, while MMP-9 expression was elevated in Early Stage metastasis. E-cadherin expression is restored somewhat in Early Stage metastasis, but suppressed again in Late Stage metastasis. These data suggest that the expression of VEGF, MMP-9 and E-cadherin each change in the process of lymph node metastasis in oesophageal cancer, and that the patterns of change are different.     

CD133 expression is correlated with lymph node metastasis and vascular endothelial growth factor-C expression in pancreatic cancer

Although CD133 has been shown to be a marker for cancer stem cells in various tumours, its expression in pancreatic cancer has not yet been clinically reported. In this study, we investigated the relationship between CD133 expression and clinicopathological factors in pancreatic cancer. Pancreatic head carcinoma specimens from 80 patients who underwent surgical resection were immunohistochemically assessed for CD133, vascular endothelial growth factor (VEGF)-C, CXCR4, CD34, Ki-67, and cytokeratin (CK) expressions. Sixty percentage (48/80) of specimens were CD133-positive, with less than 15% cells per specimen expressing the marker. CD133-positive cells were found at the peripheral site of adenocarcinoma glandular structures and were negative for CK. There was a significant correlation between CD133 expression and clinicopathological factors, including histological type, lymphatic invasion, and lymph node metastasis (P=0.0215, 0.0023, and 0.0024, respectively). Vascular endothelial growth factor-C expression was also significantly correlated with CD133 expression (P=0.0002). Consequently, the 5-year survival rate of CD133-positive patients was significantly lower than that of CD133-negative patients (P=0.0002) and multivariate analysis revealed that CD133 expression was an independent prognostic factor (P=0.0103). These results suggest that CD133 expression in pancreatic cancer was significantly associated with lymphatic metastasis, VEGF-C expression, and prognosis.     

血管内皮生长因子-C在胃癌组织中的表达及与肿瘤淋巴结转移的关系

目的:检测血管内皮生长因子 C(vascu larendothelialgrowthfactor C,VEGF C)在胃癌 组织中的表达及其与肿瘤淋巴结转移的关系。 方法:采用免疫组织化ABC法检测52例胃癌组 织中VEGF C的表达及定位。结果:52例中29 例VEGF C染色阳性,阳性率55.8%,阳性物质 主要位于细胞质内,VEGF C在有淋巴结转移的 胃癌组织中表达(63.4%)明显高于无淋巴结转 移组(27.3%),χ2=4.59,P<0.05;低分化胃癌 中的表达(72.4%)明显高于高、中分化胃癌 (37.8%),χ2=7.44,P<0.01。结论:VEGF C 的表达与胃癌肿瘤细胞的淋巴结转移密切相关。     

Expression and function of vascular endothelial growth factor receptor-1 on human colorectal cancer cells

Vascular endothelial growth factor (VEGF) is associated with tumor angiogenesis and poor prognosis in human colorectal cancer (CRC). VEGF receptor-1 (VEGFR-1 or Flt-1) is a high-affinity receptor for VEGF and is typically considered specific to endothelial cells. Here we report the expression and function of VEGFR-1 in CRC cell lines. VEGFR-1 was expressed in all CRC cell lines studied as determined by RT-PCR, Western blot analysis, FACS, and ELISA. Treatment of the human CRC cell lines HT-29 and SW480 with VEGF-A (a ligand for both VEGFR-1 and -2) or VEGF-B (a ligand specific for VEGFR-1) led to activation of Erk-1/2, SAPK/JNK, and translocation of the p65 subunit of nuclear factor-kappaB into the nucleus. Both VEGF-A and -B led to significant induction of cell motility and invasiveness of CRC cells. Stimulation of cells with VEGF-A or -B also led to larger and more numerous colonies in soft agar. However, activation of VEGFR-1 did not increase CRC cell proliferation. In contrast to the previous paradigm that VEGFRs are not present on tumor cells of epithelial origin, we found that VEGFR-1 is present and functional on CRC cells, and activation by VEGF family ligands can activate processes involved in tumor progression and metastasis.     

血管内皮生长因子-C在胃癌组织中的表达及与肿瘤淋巴结转移的关系

目的：检测血管内皮生长因子-C（vascular endothelial growth factor-C，VEGF-C）在胃癌组织中的表达及其与肿瘤淋巴结转移的关系。方法：采用免疫组织化ABC法检测52例胃癌组织中VEGF-C的表达及定位。结果：52例中29例VEGF-C染色阳性，阳性率55．8％，阳性物质主要位于细胞质内，VEGFC在有淋巴结转移的胃癌组织中表达（63．4％）明显高于无淋巴结转移组（27．3％），X^2=4．59，P〈0．05；低分化胃癌中的表达（72．4％）明显高于高、中分化胃癌（37．8％），X^2=7．44，P〈0．01。结论：VEGF-C的表达与胃癌肿瘤细胞的淋巴结转移密切相关。     

Expression analysis of vascular endothelial growth factors and their relationships to lymph node metastasis in human colorectal cancer

This study was undertaken to determine whether expressions of the vascular endothelial growth factor (VEGF) family (VEGF-A, VEGF-B, VEGF-C, and VEGF-D) are correlated with clinicopathological parameters, with particular reference to lymph node metastasis in colorectal cancer. Total RNA was isolated from 82 surgical specimens of colorectal cancer and matched to normal mucosa with (n = 41) or without (n = 41) lymph node metastasis. The mRNA expression of each VEGF family member was quantified by real-time quantitative (RTQ) RT-PCR assay. VEGF-B and VEGF-C mRNA were significantly higher both in the tumors with lymph node metastasis (p = 0.027 and p = 0.024, respectively) and in tumors with lymphatic invasion (p = 0.042 and p = 0.005, respectively). In contrast, VEGF-D mRNA was down-regulated in tumors with lymphatic involvement (p = 0.047). Among the other clinicopathological factors, we noted that VEGF-A mRNA was higher in tumors with liver metastasis than in those without (p = 0.018) and was higher in tumors with venous invasion than in those without (p = 0.007). The results of this study demonstrate that high levels of VEGF-B, C and low levels of VEGF-D mRNA expression are associated with lymph node metastasis and lymphatic involvement. These results suggest that a balance among VEGF-B, VEGF-C, and VEGF-D might contribute to the lymphangiogenic process and metastasis in colorectal cancer.