Relationship between development of microvilli on tumor cells and growth or metastatic potential of tumor cells.

The present study was undertaken to elucidate the ultrastructural differences between tumor cell clones with high growth or highly metastatic potential and those with low growth or weakly metastatic potential. Transmission, scanning and immuno-electron microscopy revealed a remarkable variance of surface microvilli between these two types of tumor cell clones. Greater numbers of microvilli appeared on the tumor cells which possess high growth or highly metastatic potential than on those of tumor cells with low growth or weakly metastatic potential. In contrast, gap junctions and desmosomes were more occasionally seen on the weakly metastatic tumor cells than the highly metastatic tumor cells. Immuno-electron microscopy revealed that epidermal growth factor (EGF) receptor and c-neu oncogene product, which is closely related to the EGF-receptor, were positively stained on the microvilli of tumor cells with high growth potential, whereas the tumor cells with low growth potential showed almost no staining. Western blot analysis also revealed that in the tumor cells with high growth potential, positive expression of c-neu at 185 kDa was stronger than in the tumor cells with low growth potential. The findings suggest that increased numbers of microvilli are closely related to the growth and metastatic potential of tumor cells.