Vascular endothelial growth factor (VEGF)‐C and VEGF‐D are potent lymphangiogenic factors produced by tumor and stromal cells. The purpose of this study was to determine whether expression of VEGF‐C and/or VEGF‐D correlates with clinicopathological features of human colorectal carcinoma. Expression of mRNAs for VEGF‐C, VEGF‐D, and their receptor VEGFR‐3 was examined by reverse transcription‐polymerase chain reaction (RT‐PCR) in six colon carcinoma cell lines and in fresh endoscopic biopsy specimens from 20 patients with colorectal carcinoma. Expression of VEGF‐C and VEGF‐D protein was also examined immunohistochemically in 139 archival surgical specimens of human colorectal carcinoma. Of the six cell lines, one (Colo320D) constitutively expressed VEGF‐C and four (Colo320D, DLD‐1, km12sm, km12c) constitutively expressed VEGF‐D mRNA. Expression of VEGF‐D mRNA was increased under low oxygen conditions, and all six cell lines constitutively expressed VEGF‐D mRNA under hypoxic conditions. Of the 139 specimens of human colorectal carcinoma, 65 (46.8%) showed intense VEGF‐C immunoreactivity and 41 (29.5%) showed intense VEGF‐D immunoreactivity. In 49 (75.3%) of the 65 and 20 (48.8%) of the 41 cases, heterogeneous intratumoral staining was observed for VEGF‐C and VEGF‐D, respectively, with the highest levels of expression at the invasive edges. VEGF‐C expression correlated with the depth of tumor invasion, lymphatic involvement, venous involvement, lymph node metastasis, and liver metastasis, and VEGF‐D expression correlated with the depth of tumor invasion, lymph node metastasis, and liver metastasis. No correlation was observed between VEGF‐C and VEGF‐D expression in tumors. The survival time of patients with VEGF‐C‐positive tumors was significantly shorter than that of patients with VEGF‐C‐negative tumors, and the survival time of patients with VEGF‐D‐positive tumors was significantly shorter than that of patients with VEGF‐D‐negative tumors. The survival time of patients with both VEGF‐C‐ and VEGF‐D‐positive tumors was significantly shorter than that of patients with both VEGF‐C‐and VEGF‐D‐negative tumors. These results suggest that VEGF‐C and VEGF‐D may be independent and important prognostic factors in patients with human colorectal carcinoma. (Cancer Sci 2004; 95: 32–39)

Recent study of murine fibrosarcoma has revealed that platelet‐derived growth factor (PDGF) plays a direct role in promoting lymphangiogenesis and metastatic spread to lymph nodes. Thus, we investigated the relation between PDGF and PDGF receptor (PDGF‐R) expression and lymphatic metastasis in human gastric carcinoma. We examined PDGF‐B and PDGF‐Rβ expression in four human gastric carcinoma cell lines (TMK‐1, MKN‐1, MKN‐45, and KKLS) and in 38 surgical specimens of gastric carcinoma. PDGF‐B and PDGF‐Rβ expression was examined by immunofluorescence in surgical specimens and in human gastric carcinoma cells (TMK‐1) implanted orthotopically in nude mice. Groups of mice (n = 10, each) received saline (control) or PDGF‐R tyrosine kinase inhibitor imatinib. PDGF‐B and PDGF‐Rβ mRNA expression was significantly higher in patients with lymph node metastasis than in those without and was also significantly higher in diffuse‐type carcinoma than in intestinal‐type carcinoma. In surgical specimens, tumor cells expressed PDGF‐B, but PDGF‐Rβ was expressed predominantly by stromal cells. Under culture conditions, expression of PDGF‐B mRNA was found in all of the gastric cell lines, albeit at different levels. In orthotopic TMK‐1 tumors, cancer cells expressed PDGF‐B but not PDGF‐Rβ. PDGF‐Rβ was expressed by stromal cells, including lymphatic endothelial cells. Four weeks of treatment with imatinib significantly decreased the area of lymphatic vessels. Our data indicate that secretion of PDGF‐B by gastric carcinoma cells and expression of PDGF‐Rβ by tumor‐associated stromal cells are associated with lymphatic metastasis. Blockade of PDGF‐R signaling pathways may inhibit lymph node metastasis of gastric carcinoma. (Cancer Sci2010)

Recent studies in molecular and cellular biology have shown that tumor growth and metastasis are not determined by cancer cells alone but also by a variety of stromal cells. The stroma constitutes a large part of most solid tumors, and cancer-stromal cell interaction contributes functionally to tumor growth and metastasis. Angiogenesis is the result of an imbalance between positive and negative angiogenic factors released by tumor and host cells into the microenvironment of the neoplastic tissue. In gastric cancer, tumor cells and stromal cells produce various angiogenic factors, including vascular endothelial growth factor, interleukin-8, and platelet-derived endothelial cell growth factor. The microenvironment in the gastric mucosa may also influence the angiogenic phenotype of gastric cancer. Helicobacter pylori infection increases expression of several angiogenic factors by tumor cells. Activated fibroblasts and macrophages in tumor stroma also play an important role in angiogenesis and tumor progression. We review the current understanding of cancer-stromal cell interaction as it pertains to tumor angiogenesis in gastric cancer.

The spread of tumor cells to regional lymph nodes is an early event of gastric cancer metastasis. In our study, we assessed the expression of lymphangiogenic factors and lymphatic endothelial markers in gastric carcinoma tissues and compared expression levels with the status of lymph node metastasis. We also examined the correlation between lymphatic vessel density (LVD) in primary tumors and lymph node metastasis. Paired biopsy samples (tumor and corresponding normal mucosa) of gastric tissue were obtained from 39 patients with gastric carcinoma. The expression of VEGF‐C, VEGF‐D, VEGFR‐3 and podoplanin mRNAs was assessed by real‐time quantitative PCR. The expression of VEGF‐C (but not of VEGF‐D) was significantly greater in patients with lymph node metastasis than in those without metastasis. The expression of lymphatic endothelial markers VEGFR‐3 and podoplanin was also significantly greater in the node‐positive group. LVD, as assessed by immunohistochemistry for podoplanin, was correlated with lymph node metastasis. These results indicate that quantitative analysis of lymphangiogenic markers in gastric biopsy specimens may be useful in predicting metastasis of gastric cancer to regional lymph nodes.