Establishment and characteristics of human hepatocellular carcinoma cells with metastasis to lymph nodes
Although the mechanism of cancer metastasis has been gradually elucidated, less is known concerning the characteristics of human hepatocellular carcinomas (HCCs) with metastatic potential. We examined the expression of molecules that mediate cell-cell or cell-substrate interaction, nm23-H1 expression, and ultrastructural features of several human HCC cell lines. Expression of E-cadherin, integrin (alpha3beta1), intracellular adhesion molecule-1 (ICAM-1), and nm23-H1 protein was analyzed by immunocytochemistry or Western blotting, and ultrastructural features were further studied by electron microscopy in 4 human HCC cell lines, PLC/PRF/5, HuH-7, OCUH-16, and Nuk-1 which were originally established from metastatic cells in lymph nodes at our institute. Neither E-cadherin, integrin, nor ICAM-1 was immunocytochemically detected in any of the 4 cell lines. Expression of nm23-H1 protein was weakly detected in OCUH-16, Nuk-1, and Huh-7 cells by Western blotting, but was clearly detected in PLC/PRF/5 cells by Western blotting. Ultrastructurally, metastatic Nuk-1 cells exhibited the intracytoplasmic canaliculus-like structures found in fibrolamellar carcinoma and the intracytoplasmic glandular lumina found in bile-duct carcinoma, while the other 3 cell lines did not. In addition, Nuk-1 cells expressed neither cytokeratin 8 nor cytokeratin 19. Nuk-1 cells, which are human HCC cells with metastasis to lymph nodes, alone exhibited intracytoplasmic canaliculus-like structures and glandular lumina, as well as a marked reduction of nm23-H1 protein, but did not express E-cadherin, integrin, or ICAM-1. Formation of both intracytoplasmic canaliculus-like structures and intracytoplasmic glandular lumina is one of the characteristics that may be involved in metastasis of HCC cells to lymph nodes, as is reduction of nm23-H1 protein.