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J Yokota

Publications and source records attributed to J Yokota.

At least 37 records · Page 2Linked to original sources
PubMed2001

Genetic alterations and expression of the protein phosphatase 1 genes in human cancers.

Recent studies have revealed that genetic alterations of the protein phosphatase genes, including PTEN, PPP2R1A, PPP2R1B and PPP1R3, are involved in human carcinogenesis. In the present study, we examined the genetic and expression status of nine protein phosphatase 1 (PP1) genes in 55 human cancer cell lines, consisting of 10 small cell lung cancers, 22 non-small cell lung cancers, 11 colorectal cancers, 7 gastric cancers and 5 ovarian cancers. The PP1 genes examined were three catalytic subunit genes, PPP1CA, PPP1CB and PPP1CC, and six regulatory subunit genes, PPP1R1A, PPP1R2, PPP1R5, PPP1R6, PPP1R7 and PPP1R8. Three catalytic subunit genes and three regulatory subunit genes, PPP1R2, PPP1R7 and PPP1R8, were ubiquitously expressed in the 55 cell lines, while PPP1R1A, PPP1R5, and PPP1R6 were differentially expressed. Possible missense mutations of the PPP1R5, PPP1R7 and PPP1R8 genes were detected in one (2%), two (4%) and one (2%) cell line, respectively. A rare, non-synonymous polymorphism was also identified in the PPP1R5 gene. Four of the 55 cell lines carried genetic alterations of several protein phosphatase genes, including PTEN, PPP1R3, PPP1R7 and PPP1R8. Ubiquitous expression as well as a lack of genetic diversity of catalytic subunit genes suggested the essential role of these genes for the growth of cancer cells. In contrast, differential expression, somatic mutations and/or genetic polymorphisms of several regulatory subunit genes indicate the involvement of these genes in multistep carcinogenesis.

DNA Primers↗
PubMed2001

Absence of p51 alteration in human ovarian cancer.

The p51 gene encodes a protein with significant homology to p53, thus, it is a candidate tumor suppressor gene. To investigate the involvement of the p51 gene in human ovarian carcinogenesis, p51 gene alterations were examined in primary ovarian cancers and ovarian cancer cell lines. Mutation analysis of the p51 gene was performed in 40 primary ovarian cancers and 6 ovarian cancer cell lines using the PCR-SSCP and direct sequencing methods. Expression of p51 mRNA was examined in 9 primary ovarian cancers and 5 ovarian cancer cell lines by Northern blot and RT-PCR analyses. No mutations of the p51 gene causing amino acid substitutions or frameshifts were detected in either primary tumors or cancer cell lines by PCR-SSCP analysis of the entire coding region, although several genetic polymorphisms were detected in three samples. Allelic imbalance was detected in 3 of 19 (16%) primary ovarian cancers. No p51 gene expression was detected in 9 primary ovarian cancers and the corresponding normal ovarian tissues by Northern blot and by RT-PCR analyses. One of 5 ovarian cancer cell lines showed p51 gene expression by Northern blot analysis (20%). These results indicated that p51 gene expression was silent in normal ovarian tissues and primary ovarian cancers, and that mutation of the p51 gene does not play a major role in the development of ovarian cancer.

Blotting, Northern↗
PubMed2000

Adenine excisional repair function of MYH protein on the adenine:8-hydroxyguanine base pair in double-stranded DNA.

Adenine paired with 8-hydroxyguanine (oh(8)G), a major component of oxidative DNA damage, is excised by MYH base excision repair protein in human cells. Since repair activity of MYH protein on an A:G mismatch has also been reported, we compared the repair activity of His(6)-tagged MYH proteins, expressed in Spodoptera frugiperda Sf21 cells, on A:oh(8)G and A:G mismatches by DNA cleavage assay and gel mobility shift assay. We also compared the repair ability of type 1 mitochondrial protein with type 2 nuclear protein, as well as of polymorphic type 1-Q(324) and 2-Q(310) proteins with type 1-H(324) and 2-H(310) proteins by DNA cleavage assay and complementation assay of an Escherichia coli mutM mutY strain. In a reaction buffer with a low salt (0-50 mM) concentration, adenine DNA glycosylase activity of type 2 protein was detected on both A:oh(8)G and A:G substrates. However, in a reaction buffer with a 150 mM salt concentration, similar to physiological conditions, the glycosylase activity on A:G, but not on A:oh(8)G, was extremely reduced and the binding activity of type 2 protein for A:G, but not for A:oh(8)G, was proportionally reduced. The glycosylase activity on A:oh(8)G and the ability to suppress spontaneous mutagenesis were greater for type 2 than type 1 enzyme. There was apparently no difference in the repair activities between the two types of polymorphic MYH proteins. These results indicate that human MYH protein specifically catalyzes the glycosylase reaction on A:oh(8)G under physiological salt concentrations.

Adenine↗
PubMed2000

Identification of a 428-kb homozygously deleted region disrupting the SEZ6L gene at 22q12.1 in a lung cancer cell line.

Frequent allelic losses on chromosome 22q in small cell lung carcinomas (SCLCs) and advanced non-small cell lung carcinomas indicate the presence of tumor suppressor gene(s) on this chromosome arm. We detected a homozygous deletion at 22q12.1 in a SCLC cell line, Lu24. Cloning of the breakpoints of the Lu24 deletion revealed that the deletion was interstitial and 428, 131 bp in size. The deleted region contained the SEZ6L (Seizure 6-like) gene, whose structure had been partially determined by the chromosome 22 sequencing project. We determined the full length cDNA sequence for the SEZ6L gene based on the genomic sequence for the SEZ6L locus using the GENSCAN program and the RT - PCR method. The deduced SEZ6L protein was a transmembrane protein of 1024 amino acids with multiple domains involved in protein - protein interaction and signal transduction. SEZ6L expression was detected in a variety of human tissues, including lung, while its expression was detected in 14 (30%) of 46 lung cancer cell lines examined. Missense mutations were detected in three (7%) of the 46 cell lines, and a 1 bp deletion in the polypyrimidine tract preceding exon 4 was detected in one (2%) of 46 primary lung cancers. Therefore, it is possible that genetic and/or epigenetic SEZ6L alterations are involved in the development and/or progression in a subset of lung cancer, although functional analysis of the SEZ6L gene as well as molecular analysis of other genes in the homozygously deleted region is necessary to understand the pathogenetic significance of 22q deletions in human lung carcinogenesis.

Amino Acid Sequence↗
PubMed2000

A novel gene, MEL1, mapped to 1p36.3 is highly homologous to the MDS1/EVI1 gene and is transcriptionally activated in t(1;3)(p36;q21)-positive leukemia cells.

The reciprocal translocation t(1;3)(p36;q21) occurs in a subset of myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML), which is frequently characterized by trilineage dysplasia, in particular dysmegakaryocytopoiesis, and poor prognosis. Previously, the breakpoint cluster region (BCR) at 3q21 was identified within a 60-kilobase (kb) region centromeric to the BCR of 3q21q26 syndrome and that at 1p36.3 within a 90-kb region. In this study, genes were searched near the breakpoints at 1p36.3, and a novel gene was isolated that encoded a zinc finger protein with a PR domain, which is highly homologous to the MDS1/EVI1 gene. The novel gene, designated as MEL1 (MDS1/EVI1-like gene 1), with 1257 amino acid residues is 64% similar in nucleotide and 63% similar in amino acid sequences to MDS1/EVI1 with the same domain structure. The MEL1 gene is expressed in leukemia cells with t(1;3) but not in other cell lines or bone marrow, spleen, and fetal liver, suggesting that MEL1 is specifically in the t(1;3)(p36;q21)-positive MDS/AML. On the basis of the positional relationship between the EVI1 and MEL1 genes in each translocation, it was suggested that both genes are transcriptionally activated by the translocation of the 3q21 region with the Ribophorin I gene. Because of the transcriptional activation of the EVI1 family genes in both t(1;3)(p36;q21)-positive MDS/AML and 3q21q26 syndrome, it is suggested that they share a common molecular mechanism for the leukemogenic transformation of the cells.

Amino Acid Sequence↗
PubMed2000

Population-based mapping of pulmonary adenoma susceptibility 1 locus.

Pulmonary adenoma susceptibility 1 (Pas1), the major locus affecting inherited predisposition to lung tumor development in mice, maps near the Kras2 gene. We previously reported a significant association between a KRAS2/RsaI polymorphism and the risk and prognosis of lung adenocarcinoma (ADCA) in the Italian population. In the present case-control study, we examined 269 lung ADCA patients, 121 squamous cell lung carcinoma patients, and 632 healthy individuals (general population controls) in the Japanese population with genetic markers spanning approximately 1200 kb in the KRAS2 region. Allele-specific oligonucleotide hybridization revealed the same KRAS2/RsaI polymorphism associated with risk and prognosis as in Italian lung ADCA patients; the polymorphism was significantly associated with clinical stage (P < 0.001) and survival rate (log rank = 0.0014), confirming the mapping of PAS1 and pointing to the role of this locus in human lung cancer.

Adenocarcinoma↗
PubMed2000

Differential expression of the LAMB3 and LAMC2 genes between small cell and non-small cell lung carcinomas.

To identify genes differentially expressed between small cell lung carcinoma (SCLC) cells and non-SCLC cells, mRNA differential display was applied to 3 SCLC cell lines and 6 non-SCLC cell lines. The LAMB3 gene was identified as being expressed only in non-SCLC cells and not in SCLC cells. The LAMB3 gene encodes the laminin beta3 chain, which is a unique component of laminin-5. Laminin-5 is a heterotrimer protein consisting of the alpha3, beta3, and gamma2 chains, and another unique component of laminin-5 is the gamma2 chain encoded by the LAMC2 gene. RT-PCR analysis of the LAMB3 and LAMC2 genes in 45 lung cancer cell lines revealed that both the LAMB3 and LAMC2 genes were co-expressed in 21 of 32 non-SCLC cell lines (66%) but only in one of 13 SCLC cell lines (8%). Coexpression of the LAMB3 and LAMC2 genes was also observed in all 4 cases of primary non-SCLC cells examined but not in the corresponding non-cancerous lung cells. Since alpha6beta4 integrin, the specific laminin-5 binding receptor, is known to be expressed only in non-SCLC cells and not in SCLC cells, it was indicated that laminin-5 is a critical microenvironmental factor for the growth of non-SCLC cells but not of SCLC cells. The differences in the expression of integrins and laminins would be critical factors to distinguish SCLC and non-SCLC cells, and such differences might be associated with the unique biological properties of SCLC cells, including metastatic potential and drug sensitivity.

Carcinoma, Non-Small-Cell Lung↗
PubMed2000

Frequent chromosome 8q gains in human small cell lung carcinoma detected by arbitrarily primed-PCR genomic fingerprinting.

The arbitrarily primed-polymerase chain reaction (AP-PCR) genomic fingerprinting method was applied to detect chromosomal numerical imbalances in 13 small cell lung carcinomas (SCLC). Increases and decreases in the intensity of the AP-PCR bands from several chromosomes, representing gains of chromosomes 1, 7, 16, and X, and losses of chromosomes 2, 10, and 22, were recurrent events in independent tumors. In addition, the most common alterations detected were increases in signal intensity of three AP-PCR bands derived from genomic sequences on chromosome 8q (eight of 13 tumors: 62%). To define whether the 8q gains observed in the AP-PCR analysis include the C-MYC gene at chromosome 8q24 or not, we performed targeted AP-PCR analysis of the C-MYC gene. The C-MYC gene was amplified in five of the eight tumors with gains of 8q, but in none of the remaining five tumors in which 8q gains were not detected. These results indicate that chromosome 8q gain occurs frequently in SCLC and gained regions often, but do not always, include the C-MYC gene. Moderate increases in copy number of the C-MYC gene and additional gene(s) in the 8q region appear to be under positive selection during SCLC progression.

Carcinoma, Small Cell↗
PubMed2000

Absence of hSNF5/INI1 mutation in human lung cancer.

Frequent occurrence of chromosome 22q deletions in lung cancer indicates the presence of a tumor suppressor gene on this chromosome arm. The hSNF5/INI1 gene at chromosome 22q11.2 has recently been shown to act as a tumor suppressor in rhabdoid tumors. To investigate whether the hSNF5/INI1 gene located on chromosome 22q is involved in lung carcinogenesis, mutation analysis of the hSNF5/INI1 gene was performed using 50 lung cancer cell lines. No mutations causing amino acid substitutions or frameshifts were found by PCR-SSCP analysis of the entire coding region. The results indicated that the hSNF5/INI1 gene is not inactivated in lung cancers and suggested the presence of another tumor suppressor gene on chromosome 22q. Thus, further studies are necessary to identify the target lung tumor suppressor gene(s) on chromosome 22q.

Chromosomal Proteins, Non-Histone↗
PubMed2000

Molecular cloning of a novel NF2/ERM/4.1 superfamily gene, ehm2, that is expressed in high-metastatic K1735 murine melanoma cells.

We have cloned a novel gene, Ehm2, that is expressed in high-metastatic but not in low-metastatic K-1735 murine melanoma cells. The Ehm2 gene encodes a protein of 527 amino acid residues, showing up to 41% amino acid identity with the FERM domain of NF2/ERM/4.1 superfamily proteins, which have the function of connecting cell surface transmembrane proteins to cytoskeletal molecules. The Ehm2 gene was mapped to chromosome 4 and was expressed in the liver, lung, kidney, and testis and in 7- to 17-day embryos. The highest level of homology was observed with NBL4, which is a new subfamily protein of the NF2/ERM/4.1 superfamily. A human homologue of the mouse Ehm2 gene, showing significant homology (83% identity), was identified in the genomic DNA and EST databases. Furthermore, seven rat EST clones and one pig EST clone in the GenBank EST database were identified as having 83-92% sequence homology with the cDNA sequence of the mouse Ehm2 gene. Thus, Ehm2 is a highly conserved gene that encodes a novel member of the NF2/ERM/4.1 superfamily proteins.

Animals↗
PubMed2000

Somatic mutations and genetic polymorphisms of the PPP1R3 gene in patients with several types of cancers.

Recently, we found nonsense and missense mutations of the PPP1R3 (protein phosphatase 1, regulatory subunit 3) gene in diverse human cancer cell lines and primary lung carcinomas, indicating that PPP1R3 functions as a tumor suppressor in human carcinogenesis. In this study, to assess the prevalence of PPP1R3 mutations in human primary cancers and the genetic diversity of the PPP1R3 gene in the human population, somatic mutations and genetic polymorphisms in the PPP1R3 gene were examined in 137 pairs of cancerous and non-cancerous tissues of patients with cancers of colon, ovary, and liver. Five somatic mutations including two missense mutations were detected in three cancerous tissues consisting of two colorectal carcinomas and one ovarian carcinoma. Five novel single nucleotide polymorphisms (SNPs) associated with the substitution of amino acids were also identified in cancer patients, in addition to five known nonsynonymous SNPs, including three previously reported ones as having an impact on the susceptibility to insulin resistant disorders. Differences in the activities and properties of multiple PPP1R3 proteins, which are produced in human cells due to variable somatic mutations and genetic polymorphisms in the PPP1R3 gene, can be involved in human carcinogenesis and susceptibility to diseases.

Amino Acid Substitution↗
PubMed2000

Absence of p51 mutation in human hepatocellular carcinoma.

The p51 gene encodes a protein with significant homology to p53. To investigate the involvement of the p51 gene in human hepatocarcinogenesis, mutation analysis of the p51 gene was performed in 54 cases of hepatocellular carcinoma (HCC). No mutations causing amino acid substitutions or frameshifts were found by polymerase chain reaction-single strand conformational polymorphism (PCR-SSCP) analysis of the entire coding region. The result indicated that mutation of the p51 gene does not play a major role in the development of HCC in Japanese patients. Further studies on p51 expression and its functions, including the interaction with p53, are necessary to elucidate the role of the p51 gene in human hepatocarcinogenesis.

Carcinoma, Hepatocellular↗
PubMed2000

Allelic imbalance and mutations of the PTEN gene in ovarian cancer.

The PTEN/MMAC1/TEP1 tumor-suppressor gene, which maps to chromosome 10q23.3, is mutated and homozygously deleted in a variety of human tumors, including endometrioid-type ovarian tumors. We examined 33 primary ovarian cancers and 3 ovarian borderline tumors for allelic imbalance (AI) of the 10q23.3 region using 5 polymorphic markers, including an insertion/deletion-type polymorphic marker identified in intron 4 of the PTEN gene. AI at one or more loci was detected in 12 of 31 (39%) informative ovarian cancers and none of 3 ovarian borderline tumors. The commonly deleted region was mapped between the D10S215 and D10S541 loci, including the PTEN locus. Moreover, the incidence of AI at the PTEN locus (38%) was the highest among the 5 loci examined. Therefore, we searched for mutations in the entire coding region of the PTEN gene by PCR-SSCP and sequencing analyses in these tumors and 7 ovarian cancer cell lines. Mutations were detected in 3 of the 33 (9%) ovarian cancers: 2 cases with double mutations and 1 case with a mutation on 1 allele accompanied by deletions on both alleles in the poly T tract preceding the splice acceptor site in intron 7. An intragenic deletion was detected in 1 of the 7 (14%) ovarian cancer cell lines. PTEN mutations were detected not only in the endometrioid type but also in the serous and mucinous types of ovarian cancer. However, PTEN was not mutated in the 12 tumors that showed AI of the PTEN locus. Our results suggest that the PTEN gene plays an important role in the development of a subset but diverse histological types of ovarian tumors. However, it is possible that another tumor-suppressor gene in the close vicinity of the PTEN gene is also inactivated by AI of the 10q23.3 region.

Chromosome Mapping↗
PubMed2000

Identification of breakpoint cluster regions at 1p36.3 and 3q21 in hematologic malignancies with t(1;3)(p36;q21).

The reciprocal translocation t(1;3)(p36;q21) is associated with myelodysplastic syndromes (MDSs) and acute myeloid leukemia (AML) characterized by trilineage dysplasia, in particular dysmegakaryocytopoiesis, and a poor prognosis. As yet no molecular genetic analyses of the t(1;3) have been reported. In four patients with t(1;3), all of whom had AML-M4, which evolved from MDS, the breakpoints at 3q21 clustered within a 60-kb region centromeric to the breakpoint of the inv(3)(q21q26), whereas the breakpoints at 1p36 clustered within a 90-kb region at 1p36.3. The presence of novel clusters in both the 3q21 and 1p36 breakpoints (BCRs) suggests a common, underlying molecular mechanism for the development of t(1;3)-positive MDS/AML. The Ribophorin I (RPN1) gene close to the BCR at 3q21 was highly expressed without gross structural changes, whereas the GR6 gene located within the BCR at 3q21 was not expressed. No other highly expressed genes were isolated in a 150-kb region at 3q21. Thus, it is likely that a gene at 1p36.3 is activated by the translocation of the 3q21 region or a gene important for transformation lies on 3q21, outside the 150-kb region. Further characterization of the BCRs at 1p36.3 and 3q21 should provide important insights into the molecular genetic mechanisms involved in the genesis of t(1;3)-positive MDS/AML. Genes Chromosomes Cancer 27:229-238, 2000.

Aged↗
PubMed2000

Frequent microsatellite instability and BAX mutations in T cell acute lymphoblastic leukemia cell lines.

Allelic status of the BAT26 and BAT25 loci was examined in 117 leukemia/lymphoma cell lines consisting of 44 B-lymphoid lineage cell lines, 30 T-lymphoid cell lines and 43 myeloid cell lines to define the lineage specificity of microsatellite instability (MSI) in hematological malignancies. Seventeen (15%) cell lines were defined as having MSI. The incidence of MSI was significantly (P < 0.01) higher in cell lines of lymphoid lineage (15/74; 20%) than in those of myeloid lineage (2/43; 5%). In the cell lines of lymphoid lineage, the incidence of MSI in T cell acute lymphoblastic leukemia (T-ALL) (11/30; 37%) was significantly (P < 0.01) higher than those in B-lineage malignancies (4/44; 9%). The 17 cell lines with MSI were subjected to the mutation analysis of the coding microsatellites in 13 candidate genes. Frameshift mutations were most frequently detected in the BAX gene (14/17, 82%), while the hMSH3, hMSH6, TGFbetaRII, DRP and IGFIIR genes were less frequently mutated (24-47%). The present result indicates that MSI is involved in the development and/or progression of lymphoid malignancies, especially of T-ALL, through the inactivation of BAX and several other genes.

Gene Frequency↗