BIOLOGY DIVISION

4.BIOLOGY DIVISION

    The primary project of the Biology Division is to elucidate the molecular basis of multistage human pulmonary carcinogenesis. Positional and functional cloning of several lung-cancer-related genes by the latest molecular biological methods is under way to achieve this goal. Once a gene that is genetically or epigenetically altered in cancer cells has been isolated, functional analyses are performed to clarify the biological significance of the alterations in the development of lung cancer. Since it is important to elucidate the molecular basis of metastasis, isolation and characterization of metastasis-associated genes is another project of the Division. Associations between cancer susceptibility and both genetic polymorphisms and germline mutations are also being investigated by focusing on the involvement of tumor suppressor (TSGs) genes and DNA repair genes.
Genetic Alterations in Human Cancers

    Loss of heterozygosity (LOH) on chromosomes 18q and 22q occurs frequently in advanced lung cancer, suggesting the presence of TSGs on these chromosome arms. Chromosomes 18q21 and 22q12.1 were identified as being homozygously deleted in lung cancer cell lines, and several candidate TSGs, including the SEZ6L gene, have been isolated from the regions of these deletions and characterized.^(67,⁶⁸⁾ The SEZ6L gene was found to be infrequently mutated, and its expression was reduced in lung cancers. Extensive mutational analyses of known and candidate TSGs, CTNNB1 (b-catenin), p51, and protein phosphatase 1 (PP1), have been performed in several types of human cancers.^(69-⁷¹⁾ The p51 gene was found not to be mutated in ovarian cancer.⁽⁷¹⁾ A family of PP1 genes was discovered to be infrequently mutated in several types of cancers.⁽⁷⁰⁾ Testing of several histological types of lung cancers revealed that CTNNB1 mutations occur rarely but specifically in a subset of adenocarcinomas.⁽⁶⁹⁾
Functional Analysis of Cancer-related Genes

    LOH on chromosome 3p is a common genetic alteration in lung cancer, and several candidate TSGs have recently been isolated from the 3p21 region. Functional analyses of two candidate TSGs on chromosome 3p21.3, SEMA3B and FUS1, were performed, and the results indicated that the SEMA3B and FUS1 genes have activity that induces apoptosis and G1 arrest, respectively, in lung cancer cells.^(72,⁷³⁾ A DNA-damage-inducible gene, p33ING2, was shown to negatively regulate cell proliferation through activation of p53 by enhancing its acetylation.⁽⁷⁴⁾ It was also shown that RB protein is a critical component for regulating the E2F-responsive genes while p53 protein alone affects only a subset of these genes.⁽⁷⁵⁾
Isolation and Characterization of Metastasis-associated Genes

    To elucidate the molecular mechanism of lung cancer metastasis, several cell lines with high- and low-metastatic potentials were isolated from human lung adenocarcinoma cell line PC14.⁽⁷⁶⁾ Using these sublines and the mRNA differential display method enabled isolation of a novel actin-related gene, ARP11, as a gene specifically expressed in low-metastatic sublines.⁽⁷⁷⁾
Functional Diversity among Polymorphic Base Excision Genes

    To develop novel methods for evaluation of cancer risk in individuals, genetic polymorphisms in the base excision repair genes were determined in association with their enzymatic activity.⁽⁷⁸⁾ Several single nucleotide polymorphisms were identified in the base excision repair genes OGG1, MYH1, and APEX, which are involved in the repair of 8-hydroxyguanine (oh⁸G) in DNA.⁽⁷⁹⁾ oh⁸G is a major base lesion produced by reactive oxygen species and induces G:C to T:A mutations. The ability of OGG1 protein to suppress G:C to T:A mutations in human cells was demonstrated by using a shuttle vector system with oh⁸G in a vector,⁽⁸⁰⁾ and the AP lyase activity of OGG1 protein was shown to be positively regulated by the amount of APEX protein.⁽⁸¹⁾
Genetic Factors for Multiple Primary Cancers

    Since p53 is a gene responsible for Li-Fraumeni syndrome, in which multiple primary cancers are often observed in family members, we examined a case of multiple primary cancers for a germline p53 mutation. A unique mutation of AGC(Ser) to AGG(Arg) was detected at codon 106 in DNA from non-cancerous tissue.⁽⁸²⁾ The patient had osteosarcoma, Paget carcinoma of the breast, and adenocarcinoma of the lung. Since only a limited number of germline p53 mutations have been reported to date, this information will contribute to establishing correlations between the types and locations of mutations and their phenotypic consequences.




4.BIOLOGY DIVISION



	The primary project of the Biology Division is to elucidate the molecular basis of multistage human pulmonary carcinogenesis. Positional and functional cloning of several lung-cancer-related genes by the latest molecular biological methods is under way to achieve this goal. Once a gene that is genetically or epigenetically altered in cancer cells has been isolated, functional analyses are performed to clarify the biological significance of the alterations in the development of lung cancer. Since it is important to elucidate the molecular basis of metastasis, isolation and characterization of metastasis-associated genes is another project of the Division. Associations between cancer susceptibility and both genetic polymorphisms and germline mutations are also being investigated by focusing on the involvement of tumor suppressor (TSGs) genes and DNA repair genes. Genetic Alterations in Human Cancers Loss of heterozygosity (LOH) on chromosomes 18q and 22q occurs frequently in advanced lung cancer, suggesting the presence of TSGs on these chromosome arms. Chromosomes 18q21 and 22q12.1 were identified as being homozygously deleted in lung cancer cell lines, and several candidate TSGs, including the SEZ6L gene, have been isolated from the regions of these deletions and characterized.^(67,⁶⁸⁾ The SEZ6L gene was found to be infrequently mutated, and its expression was reduced in lung cancers. Extensive mutational analyses of known and candidate TSGs, CTNNB1 (b-catenin), p51, and protein phosphatase 1 (PP1), have been performed in several types of human cancers.^(69-⁷¹⁾ The p51 gene was found not to be mutated in ovarian cancer.⁽⁷¹⁾ A family of PP1 genes was discovered to be infrequently mutated in several types of cancers.⁽⁷⁰⁾ Testing of several histological types of lung cancers revealed that CTNNB1 mutations occur rarely but specifically in a subset of adenocarcinomas.⁽⁶⁹⁾ Functional Analysis of Cancer-related Genes LOH on chromosome 3p is a common genetic alteration in lung cancer, and several candidate TSGs have recently been isolated from the 3p21 region. Functional analyses of two candidate TSGs on chromosome 3p21.3, SEMA3B and FUS1, were performed, and the results indicated that the SEMA3B and FUS1 genes have activity that induces apoptosis and G1 arrest, respectively, in lung cancer cells.^(72,⁷³⁾ A DNA-damage-inducible gene, p33ING2, was shown to negatively regulate cell proliferation through activation of p53 by enhancing its acetylation.⁽⁷⁴⁾ It was also shown that RB protein is a critical component for regulating the E2F-responsive genes while p53 protein alone affects only a subset of these genes.⁽⁷⁵⁾ Isolation and Characterization of Metastasis-associated Genes To elucidate the molecular mechanism of lung cancer metastasis, several cell lines with high- and low-metastatic potentials were isolated from human lung adenocarcinoma cell line PC14.⁽⁷⁶⁾ Using these sublines and the mRNA differential display method enabled isolation of a novel actin-related gene, ARP11, as a gene specifically expressed in low-metastatic sublines.⁽⁷⁷⁾ Functional Diversity among Polymorphic Base Excision Genes To develop novel methods for evaluation of cancer risk in individuals, genetic polymorphisms in the base excision repair genes were determined in association with their enzymatic activity.⁽⁷⁸⁾ Several single nucleotide polymorphisms were identified in the base excision repair genes OGG1, MYH1, and APEX, which are involved in the repair of 8-hydroxyguanine (oh⁸G) in DNA.⁽⁷⁹⁾ oh⁸G is a major base lesion produced by reactive oxygen species and induces G:C to T:A mutations. The ability of OGG1 protein to suppress G:C to T:A mutations in human cells was demonstrated by using a shuttle vector system with oh⁸G in a vector,⁽⁸⁰⁾ and the AP lyase activity of OGG1 protein was shown to be positively regulated by the amount of APEX protein.⁽⁸¹⁾ Genetic Factors for Multiple Primary Cancers Since p53 is a gene responsible for Li-Fraumeni syndrome, in which multiple primary cancers are often observed in family members, we examined a case of multiple primary cancers for a germline p53 mutation. A unique mutation of AGC(Ser) to AGG(Arg) was detected at codon 106 in DNA from non-cancerous tissue.⁽⁸²⁾ The patient had osteosarcoma, Paget carcinoma of the breast, and adenocarcinoma of the lung. Since only a limited number of germline p53 mutations have been reported to date, this information will contribute to establishing correlations between the types and locations of mutations and their phenotypic consequences.