| Research Abstract |
1)Aberrant expression of a proto-oncogene with serine/threonine kinase activity; Pim-3, in malignant lesions of endoderm-derived organs. We compared gene expression patterns in pre-malignant and malignant lesions in murine hepatocarinogenesis model, by using fluorescent differential display method. As a result, we observed that a proto-oncogene with serine/threonine kinase activity, Pim-3 was aberrantaly expressed in pre-malignant and malignant lesions, but not normal hepatic tissues. Similar observations were obtained also on human hepatocellular carcinoma (HCC) and normal liver tissues. Pim-3 was constitutively expressed in human HCC cell lines and the inhibition of Pim-3 expression by short interfering RNA induced the apoptosis of human HCC cell lines. Pim-3 was not detected in other endoderm-derived organs such as pancreas and colon, but its expression was enhanced in the pre-malignant lesions and malignant lesions of these organs. In both human pancreatic cancer and colorectal can
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cer cell lines, Pim-3 was constitutively expressed and a pro-apoptotic molecule, Bad was co-localized with Pim and was phosphorylated at 112-Ser, which represents its inactive form. The inhibition of Pim-3 expression by short interfering RNA reduced the phosphorylation of Bad at 112-Ser and the expression of an anti-apoptotic molecule, Bcl-XL and eventually enhanced the apoptosis. These observations suggest that aberrant expression of Pim-3 can contribute to carcinogenesis in endoderm-derived organs, including liver, pancreas, and colon, by inhibiting apoptosis and that Pim-3 can be a novel tumor marker to detect pre-malignant and malignant lesions of these organs.
2)Roles of chemokines and hepatocarcinogenesis and liver metastasis We observed that a chemokine, CCL3 and its receptor, CCR1, can inhibit the carcinogenesis in the early phase of murine hepatocarcinogenesis induced by diethylnitrosamine administration but that the CCL3-CCR1 axis can promote carcinogenesis of the same hepatocarcinogenesis, by inducing angiogenesis. We further demonstrated that another chemokine, CCL2 and its receptor, CCR2, can promote liver metastasis by activating hepatic stellate cells (Ito cells) and eventually accelerating neovascularization. Less
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