PATHOLOGY DIVISION

1.PATHOLOGY DIVISION

    Research in the Pathology Division is based on a combination of molecular and cellular biological analyses and clinicopathological observations.
Molecular Diagnosis of Biological Aggressiveness of Human Cancers

    Differential display and gene chip analyses were used to identify genes that are expressed selectively in a lesion specific manner.^(1,²⁾ An orphan G protein-coupled receptor was identified as being frequently overexpressed in hepatocellular carcinomas (HCCs) with b-catenin mutation, and has the potential to be a new therapeutic target in the treatment of HCC. Tetraspanin CO-029 was identified as being overexpressed in HCCs, especially in HCCs showing intrahepatic spreading, while the other tetraspanins, CD9 and CD82, were downregulated in HCCs.⁽³⁾ It was also indicated that CO-029 overexpression could be a poor prognostic factor. A candidate molecular marker for the diagnosis of early HCC, which is difficult even for pathologists because of its very well differentiated histology with little atypia, was identified. Molecular prognostic factors of various cancers and cancer related genes were also studied.^(4,⁵⁾
Alteration of DNA methylation in multistage carcinogenesis

    The average level of mRNA for DNMT (DNA methyltransferase) 1 and DNMT3a was significantly higher in chronic hepatitis or cirrhosis, which are considered to be precancerous conditions, than in histologically normal liver tissues, and was even higher in HCCs.⁽⁶⁾ Overexpression of DNMT1 was particularly associated with the CpG islands methylator phenotype of colorectal and stomach cancers.⁽⁷⁾ In respect of methyl-CpG-binding proteins, reduced expression of DNA repair protein MBD4 and transcriptional repressor MeCP2 may play a role in the malignant progression of HCC.⁽⁶⁾ In an attempt to identify tumor-related genes whose expression is affected by DNA methylation and that participate in the determination of the biological characteristics of human cancers, the differential display method was used in 5-azacytidine-treated human cancer cell lines.⁽⁸⁾ Among genes whose expression was induced during 5-azacytidine treatment, reduced expression of Wip1 was significantly correlated with poorer tumor differentiation and involvement of portal vein in HCC. Reduced expression of B4-2 protein was associated with hepatitis B virus infection.⁽⁸⁾ DNA methylation may play a role in multistage carcinogenesis through direct or indirect regulation of multiple tumor-related genes.
Molecular and Cellular Mechanisms of Cancer Invasion and Metastasis

    Dysadherin is a transmembrane protein which downregulates E-cadherin activity in cancer cells. By Yeast Two Hybrid screening, a novel serine/threonine kinase (DASK: Dysadherin-ASsociated Kinase) was isolated as an interacting molecule with the cyto-plasmic domain of dysadherin. DASK is broadly expressed in various cancer cell lines. To elucidate the functions of the mutant b-catenin protein in colon carcinogenesis,⁽⁹⁾ the wild or the mutant b-catenin gene of a colorectal cancer cell line was disrupted by somatic cell gene targeting. There was no significant difference in the in vitro and in vivo growth between the two genotypes. This suggests that mutant b-catenin may not particularly enhance the growth of some colorectal cancers. By analyzing several hepatocellular carcinoma cell lines with an "in vivo model" for intrahepatic metastasis of HCC, the acquisition of cell survival ability through activated PI3 kinase-AKT pathway, as well as the increase of cell motility potentiated by Rho-ROCK pathway, was shown to play an important role in intrahepatic metastasis.^(10,¹¹⁾
Clinicopathological Studies

    EGFR gene amplification and protein expression were shown to be closely correlated with laminin-5g2 chain expression in oral squamous cell carcinoma cell lines and resected tongue cancer specimens. Increased cytoplasmic localization of laminin-5g2 chain was found to be associated with a poor prognosis for the patients with tongue, colon, pancreas⁽¹²⁾ and lung⁽¹³⁾ cancers. Intraductal papillary components in invasive ductal carcinoma of the pancreas were revealed to be associated with long-term survival of patients.⁽¹⁴⁾ Clinicopathological studies were also conducted to promote the diagnosis and treatment of various tumors.^(15-⁴⁷⁾




1.PATHOLOGY DIVISION



	Research in the Pathology Division is based on a combination of molecular and cellular biological analyses and clinicopathological observations. Molecular Diagnosis of Biological Aggressiveness of Human Cancers Differential display and gene chip analyses were used to identify genes that are expressed selectively in a lesion specific manner.^(1,²⁾ An orphan G protein-coupled receptor was identified as being frequently overexpressed in hepatocellular carcinomas (HCCs) with b-catenin mutation, and has the potential to be a new therapeutic target in the treatment of HCC. Tetraspanin CO-029 was identified as being overexpressed in HCCs, especially in HCCs showing intrahepatic spreading, while the other tetraspanins, CD9 and CD82, were downregulated in HCCs.⁽³⁾ It was also indicated that CO-029 overexpression could be a poor prognostic factor. A candidate molecular marker for the diagnosis of early HCC, which is difficult even for pathologists because of its very well differentiated histology with little atypia, was identified. Molecular prognostic factors of various cancers and cancer related genes were also studied.^(4,⁵⁾ Alteration of DNA methylation in multistage carcinogenesis The average level of mRNA for DNMT (DNA methyltransferase) 1 and DNMT3a was significantly higher in chronic hepatitis or cirrhosis, which are considered to be precancerous conditions, than in histologically normal liver tissues, and was even higher in HCCs.⁽⁶⁾ Overexpression of DNMT1 was particularly associated with the CpG islands methylator phenotype of colorectal and stomach cancers.⁽⁷⁾ In respect of methyl-CpG-binding proteins, reduced expression of DNA repair protein MBD4 and transcriptional repressor MeCP2 may play a role in the malignant progression of HCC.⁽⁶⁾ In an attempt to identify tumor-related genes whose expression is affected by DNA methylation and that participate in the determination of the biological characteristics of human cancers, the differential display method was used in 5-azacytidine-treated human cancer cell lines.⁽⁸⁾ Among genes whose expression was induced during 5-azacytidine treatment, reduced expression of Wip1 was significantly correlated with poorer tumor differentiation and involvement of portal vein in HCC. Reduced expression of B4-2 protein was associated with hepatitis B virus infection.⁽⁸⁾ DNA methylation may play a role in multistage carcinogenesis through direct or indirect regulation of multiple tumor-related genes. Molecular and Cellular Mechanisms of Cancer Invasion and Metastasis Dysadherin is a transmembrane protein which downregulates E-cadherin activity in cancer cells. By Yeast Two Hybrid screening, a novel serine/threonine kinase (DASK: Dysadherin-ASsociated Kinase) was isolated as an interacting molecule with the cyto-plasmic domain of dysadherin. DASK is broadly expressed in various cancer cell lines. To elucidate the functions of the mutant b-catenin protein in colon carcinogenesis,⁽⁹⁾ the wild or the mutant b-catenin gene of a colorectal cancer cell line was disrupted by somatic cell gene targeting. There was no significant difference in the in vitro and in vivo growth between the two genotypes. This suggests that mutant b-catenin may not particularly enhance the growth of some colorectal cancers. By analyzing several hepatocellular carcinoma cell lines with an "in vivo model" for intrahepatic metastasis of HCC, the acquisition of cell survival ability through activated PI3 kinase-AKT pathway, as well as the increase of cell motility potentiated by Rho-ROCK pathway, was shown to play an important role in intrahepatic metastasis.^(10,¹¹⁾ Clinicopathological Studies EGFR gene amplification and protein expression were shown to be closely correlated with laminin-5g2 chain expression in oral squamous cell carcinoma cell lines and resected tongue cancer specimens. Increased cytoplasmic localization of laminin-5g2 chain was found to be associated with a poor prognosis for the patients with tongue, colon, pancreas⁽¹²⁾ and lung⁽¹³⁾ cancers. Intraductal papillary components in invasive ductal carcinoma of the pancreas were revealed to be associated with long-term survival of patients.⁽¹⁴⁾ Clinicopathological studies were also conducted to promote the diagnosis and treatment of various tumors.^(15-⁴⁷⁾