Gap junctions are associated with cell growth and differentiation in tissue organization. However, the association of gap junctions with chondrogenesis or chondrogenic differentiation is still unclear. We succeeded in establishing a cartilaginous transplanted tumor in a nude mouse from a human chondroblastic osteosarcoma, and a cell line (USAC) expressing chondrocytic phenotypes from the transplanted tumor. Using these transplanted tumor and USAC cells, we investigated the relationship between the expression of gap junctions and chondrogenesis or chondrogenic differentiation. Gap junctions are observed by immunostaining with connexin 43 (Cx 43) protein, which is an intrinsic component of gap junctions. The results revealed that Cx 43 in the tumor tissue was found both on chondrocytic and hypertrophic cells. In cultured cells, gap junctions composed of Cx 43 appearing as USAC cells were condensed and progressed toward mature chondrocytic cells. A high density micro-mass culture of USAC cells showed that dexamethasone and 1 a, 25 (OH) 2D3, which stimulated chondrogenic differentiation, enhanced the expression of Cx 43. These results indicate that expression of gap junctions is closely linked to chondrogenesis and chondrogenic differentiation.
Lymphatic vessels are distributed directly under the epithelium of the oral mucosal. In the present study, we investigated whether lymphoangiogenseis in tumors occurs in human oral squamous cell carcinoma and whether the density of tumor lympahngiogensis may be related to the risk of lymph node metastasis. Moreover, these analyses identified peritumoral lymphatic vascular density as a novel prognostic indicator for the risk of lymph node metastasis in oral squamous cell carcinoma. LYVE-1, which was an endothelial cell hyaluronic acid receptor, has been identified as a peculiar protein of endothelial cells of lymphatic vessels. LYVE-1 expression in the carcinoma tissue was divided into two types. In one it appears in contact with the cancer nest. This shows contact with basal-like cells which are located on the outer side of the cancer nest, and observation via light microscope is unable to show intervention of the fibrous connective tissues. The other case is that in which there is intervention of the clear fibrous connective tissues between the cancer nest and LYVE-1-positive cells. The cancer cells showed a high degree of differentiation, increased by the formation of the cancer nest, and in what is called highly-differentiated squamous cell carcinoma whose invasion pattern showed INF alpha, the cells staining positive to the LYVE-1 antibody could be recognized only negligibly in the connective tissue. Positive staining of the LYVE- 1 antibody was seen in the endothelial cells presenting in the lumen formed between each small cancer nest in the case of undifferentiated squamous cell carcinoma in which the cancer nest was very small and composed of undifferentiated cancer cells. In this case the cancer invasion pattern shows INFγ. In addition, the expression of LYVE-1 was recognized in cells which had not formed into the lumen between the cancer nests. In the meantime, VEGF-C was expressed in endothelial cells which formed the lumen and cancer cells. In the cancer cells which formed the large cancer nest, the expression of VEGF-C was recognized in basal-like cells which located at the periphery of the nest. VEGF-C was expressed in the cancer cells which formed the small nest. The results of this study show that the incidence of VEGF-C expression in the cancer cell is low. However, lymphatic vessels form in carcinoma tissue at a high rate when VEGF-C is expressed. It was shown that in this study, the close proximity of the lymphatic vessel to the cancer nest shows correlation to lymph node metastasis. This should affect the determination of the operation range, and have a direct influence on prognosis. It is also indicated that LYVE-1 can act as a useful marker in oral cancer.