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 analysis was used to identify genes that are expressed selectively in a lesion specific manner.⁽¹⁾ Several new genes were identified. The expression level of one of these genes was down-regulated in parallel with hepatocellular carcinoma progression. Microdissection was used to analyze the gene expression pattern of cancer and stromal fractions separately in surgically resected lung adenocarcinoma specimens. Stromal myofibroblasts were shown to express not only HGF (hepatocyte growth factor), but also its receptor c-Met. Survival analysis of 131 patients with small-sized lung adenocarcinoma showed the presence of c-Met expression in stromal myofibroblasts to be associated with a poor prognosis, especially in those with stage I disease.
    Molecular prognostic factors of various cancers and cancer related genes were also studied.^(2-¹¹⁾
Alteration of DNA methylation in multistage carcinogenesis

    In order to clarify the significance of DNA methylation during multistage hepatocarcinogenesis, a comprehensive study was performed using microdissected specimens. Even in the precancerous stage, loss of heterozygosity (LOH), microsatellite instability (MSI) and DNA hypermethylation on C-type CpG islands, where cancer-specific CpG methylation had been reported, were found.⁽¹²⁾ In cancerous tissues, LOH, MSI and DNA hypermethylation were found more frequently than in the precancerous stage.⁽¹²⁾ Absence of silencing of the hMLH1 gene by DNA hypermethylation is consistent with the low incidence of MSI in hepatocellular carcinomas.⁽¹²⁾ At the E-cadherin locus, which is a hot spot for both DNA hypermethylation and LOH, the majority of samples of chronic hepatitis and cirrhosis showed both DNA hypermethylation and LOH, or neither. The incidence of DNA hypermethylation alone in chronic hepatitis and cirrhosis was also high, but that of LOH alone was significantly lower than in the former two cases.⁽¹³⁾ Thus, it was confirmed that LOH and aberrant DNA methylation contribute to hepatocarcinogenesis; DNA hypermethylation in particular, which precedes LOH, is an event occurring early in hepatocarcinogenesis.
Molecular and Cellular Mechanisms of Cancer Invasion and Metastasis

    A large-scale comparison of expression profiles, using two-color fluorescence hybridization of cDNA microarray, led to the identification of multidrug resistance gene-1 (MDR1) as a target gene of the TCF-4/b-catenin complex. Corresponding to the accumulation of b-catenin, expression of the MDR1 gene product was steadily up-regulated in adenomas and adenocarcinomas of 10 patients with familial adenomatous polyposis.⁽¹⁴⁾
    By protein interaction screening, a cytoplasmic protein containing PDZ (PSD-95/Discs-large/ZO-1) domains was isolated as one of the b-catenin associating molecules. This molecule directly associates with b-catenin through its PDZ domain and enhances b-catenin dependent transactivation activity.
    In a highly metastatic and motile cell line, integrin-mediated cell-substratum adhesion induced loss of cadherin-mediated cell-cell adhesion and migration. In response to adhesion, a significant amount of a-catenin was dissociated from the E-cadherin-catenin complex. It was also found that the tyrosine kinase c-Src was dephosphorylated and activated by integrin-mediated cell-substratum adhesion.⁽¹⁵⁾
Clinicopathological Studies

    Identification of dedifferentiated areas, careful follow-up to detect early recurrence, and histological malignancy grading combined with proliferation indices were shown to be important in providing an accurate prognosis for patients with retroperitoneal and mesenteric liposarcoma.⁽¹⁶⁾ The presence of fibrous tissue between the metastatic adenocarcinoma and the liver parenchyma was found to be a promising indicator of a better prognosis after hepatic resection in patients with colorectal liver metastases.⁽¹⁷⁾ Lymph node metastasis and the histologic grade calculated by the degree of nuclear atypia and growth pattern were revealed to be independent poor prognostic factors for patients with superficial squamous cell carcinoma of the esophagus.⁽¹⁸⁾ Clinicopathological studies were also conducted to promote the diagnosis and treatment of various tumors.^(19-³⁹⁾




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 analysis was used to identify genes that are expressed selectively in a lesion specific manner.⁽¹⁾ Several new genes were identified. The expression level of one of these genes was down-regulated in parallel with hepatocellular carcinoma progression. Microdissection was used to analyze the gene expression pattern of cancer and stromal fractions separately in surgically resected lung adenocarcinoma specimens. Stromal myofibroblasts were shown to express not only HGF (hepatocyte growth factor), but also its receptor c-Met. Survival analysis of 131 patients with small-sized lung adenocarcinoma showed the presence of c-Met expression in stromal myofibroblasts to be associated with a poor prognosis, especially in those with stage I disease. Molecular prognostic factors of various cancers and cancer related genes were also studied.^(2-¹¹⁾ Alteration of DNA methylation in multistage carcinogenesis In order to clarify the significance of DNA methylation during multistage hepatocarcinogenesis, a comprehensive study was performed using microdissected specimens. Even in the precancerous stage, loss of heterozygosity (LOH), microsatellite instability (MSI) and DNA hypermethylation on C-type CpG islands, where cancer-specific CpG methylation had been reported, were found.⁽¹²⁾ In cancerous tissues, LOH, MSI and DNA hypermethylation were found more frequently than in the precancerous stage.⁽¹²⁾ Absence of silencing of the hMLH1 gene by DNA hypermethylation is consistent with the low incidence of MSI in hepatocellular carcinomas.⁽¹²⁾ At the E-cadherin locus, which is a hot spot for both DNA hypermethylation and LOH, the majority of samples of chronic hepatitis and cirrhosis showed both DNA hypermethylation and LOH, or neither. The incidence of DNA hypermethylation alone in chronic hepatitis and cirrhosis was also high, but that of LOH alone was significantly lower than in the former two cases.⁽¹³⁾ Thus, it was confirmed that LOH and aberrant DNA methylation contribute to hepatocarcinogenesis; DNA hypermethylation in particular, which precedes LOH, is an event occurring early in hepatocarcinogenesis. Molecular and Cellular Mechanisms of Cancer Invasion and Metastasis A large-scale comparison of expression profiles, using two-color fluorescence hybridization of cDNA microarray, led to the identification of multidrug resistance gene-1 (MDR1) as a target gene of the TCF-4/b-catenin complex. Corresponding to the accumulation of b-catenin, expression of the MDR1 gene product was steadily up-regulated in adenomas and adenocarcinomas of 10 patients with familial adenomatous polyposis.⁽¹⁴⁾ By protein interaction screening, a cytoplasmic protein containing PDZ (PSD-95/Discs-large/ZO-1) domains was isolated as one of the b-catenin associating molecules. This molecule directly associates with b-catenin through its PDZ domain and enhances b-catenin dependent transactivation activity. In a highly metastatic and motile cell line, integrin-mediated cell-substratum adhesion induced loss of cadherin-mediated cell-cell adhesion and migration. In response to adhesion, a significant amount of a-catenin was dissociated from the E-cadherin-catenin complex. It was also found that the tyrosine kinase c-Src was dephosphorylated and activated by integrin-mediated cell-substratum adhesion.⁽¹⁵⁾ Clinicopathological Studies Identification of dedifferentiated areas, careful follow-up to detect early recurrence, and histological malignancy grading combined with proliferation indices were shown to be important in providing an accurate prognosis for patients with retroperitoneal and mesenteric liposarcoma.⁽¹⁶⁾ The presence of fibrous tissue between the metastatic adenocarcinoma and the liver parenchyma was found to be a promising indicator of a better prognosis after hepatic resection in patients with colorectal liver metastases.⁽¹⁷⁾ Lymph node metastasis and the histologic grade calculated by the degree of nuclear atypia and growth pattern were revealed to be independent poor prognostic factors for patients with superficial squamous cell carcinoma of the esophagus.⁽¹⁸⁾ Clinicopathological studies were also conducted to promote the diagnosis and treatment of various tumors.^(19-³⁹⁾