Tatsuo Abe

Causal relationship between the loss of RUNX3 expression and gastric cancer.

Runx3/Pebp2alphaC null mouse gastric mucosa exhibits hyperplasias due to stimulated proliferation and suppressed apoptosis in epithelial cells, and the cells are resistant to growth-inhibitory and apoptosis-inducing action of TGF-beta, indicating that Runx3 is a major growth regulator of gastric epithelial cells. Between 45% and 60% of human gastric cancer cells do not significantly express RUNX3 due to hemizygous deletion and hypermethylation of the RUNX3 promoter region. Tumorigenicity of human gastric cancer cell lines in nude mice was inversely related to their level of RUNX3 expression, and a mutation (R122C) occurring within the conserved Runt domain abolished the tumor-suppressive effect of RUNX3, suggesting that a lack of RUNX3 function is causally related to the genesis and progression of human gastric cancer.

Internal tandem duplication of the FLT3 gene is preferentially seen in acute myeloid leukemia and myelodysplastic syndrome among various hematological malignancies. A study on a large series of patients and cell lines.

In this study, we examined a large number of patients to clarify the distribution and frequency of a recently described FLT3 tandem duplication among hematopoietic malignancies, including 112 acute myelocytic leukemia (AML), 55 acute lymphoblastic leukemia (ALL), 37 myelodysplastic syndrome (MDS), 20 chronic myelogenous leukemia (CML), 30 non-Hodgkin’s lymphoma (NHL), 14 adult T cell leukemia, 15 chronic lymphocytic leukemia (CLL) and 38 multiple myeloma (MM). We also evaluated 71 cell lines derived from 11 AML, 31 ALL, two hairy cell leukemia, three acute unclassified leukemia, 10 CML, 12 NHL including six Burkitt’s lymphoma, and two MM. Using genomic PCR of exon 11 coding for the juxtamembrane (JM) domain and first amino acids of the 5′-tyrosine kinase (TK) domain, this length mutation was found only in AML (22/112, 20%) and MDS (1/37). According to the FAB subclassification, they were 5/18 (28%) of M1, 4/29 (14%) of M2, 3/17 (18%) of M3, 6/24 (25%) of M4, 4/20 (20%) of M5 and 1/9 of refractory anemia with excess of blast in transformation. In the various cell lines examined, this abnormality was determined in only one derived from AML and never found in other hematological malignancies. The sequence analysis of the abnormal PCR products revealed that 23 of 24 showed internal tandem duplication with or without insertion of nucleotides. In one AML, insertion and deletion without duplication was determined. All 24 lengthened sequences were in-frame. Duplication takes place in the sequence coding for the JM domain and leaves the TK domain intact. In conclusion, we emphasize that the length mutation of FLT3 at JM/TK-I domains were restricted to AML and MDS. Since all these mutations resulted in in-frame, this abnormality might function for the proliferation of leukemic cells.

Tumour-amplified kinase BTAK is amplified and overexpressed in gastric cancers with possible involvement in aneuploid formation

Our recent analysis of gastric cancers using comparative genomic hybridization (CGH) revealed a novel high frequent copy number increase in the long arm of chromosome 20. Tumour-amplified kinase BTAK was recently cloned from breast cancers and mapped on 20q13 as a target gene for this amplification in human breast cancers. In the study presented here, we analysed BTAK copy-number and expression, and their relation to the ploidy pattern in 72 primary gastric cancers. Furthermore, wild-type BTAK and its deletion mutants were transfected to gastric cancers to examine changes in cell proliferation and DNA ploidy pattern. Evaluation of 72 unselected primary gastric cancers found BTAK amplification in 5% and overexpression in more than 50%. All four clinical samples with BTAK amplification showed aneuploidy and poor prognosis. Transfection of BTAK in near-diploid gastric cancers induced another aneuploid cell population. In contrast, the c-terminal-deleted mutant of BTAK induced no effect in DNA ploidy pattern and inhibited gastric cancer cell proliferation. These results suggest that BTAK may be involved in gastric cancer cell aneuploid formation, and is a candidate gene for the increase in the number of copies of the 20q, and thus may contribute to an increase in the malignant phenotype of gastric cancer.

Tandem duplications of the FLT3 receptor gene are associated with leukemic transformation of myelodysplasia.

We recently reported an internal tandem duplication of the human flt3 receptor gene (FLT3) as a somatic mutation in 17% of acute myelogenous leukemia (AML). The present study revealed the duplication at the juxtamembrane and the first tyrosine kinase domains of FLT3 in seven of 92 (8%) patients with myelodysplastic syndrome (MDS) and AML with trilineage myelodysplasia (AML/TMDS), the diseases which may represent neoplastic changes of pluripotent stem cells. A tandem duplication of exon 11 of FLT3 was harbored by two of 58 (3%) patients with MDS and five of 34 (15%) with overt leukemia, including MDS-derived leukemia, AML/TMDS and therapy-related leukemia. Although the duplicated regions varied within exon 11 in each case, they occurred in-frame, and altered mRNA expressions were demonstrated by reverse-transcription polymerase chain reaction. Two cases of MDS with a FLT3 duplication transformed to overt leukemia within a few months. Longitudinal analyses in two other patients with leukemia revealed that the duplication was a late genetic event during the disease course; one of whom showed two independent duplications of FLT3 at the terminal therapy-resistant phase. Of seven patients with the FLT3 duplication, six had abnormal karyotypes, and four harbored a point mutation of the N-RAS and/or TP53 genes. Patients with FLT3 mutations have poor prognoses. This study uncovered the fact that the accumulation of genetic events, including FLT3 duplication, correlates with leukemic transformation from antecedent myelodysplasia and with subsequent disease progression.

Gains, losses, and amplifications of genomic materials in primary gastric cancers analyzed by comparative genomic hybridization

By means of comparative genomic hybridization (CGH), we screened 58 primary gastric cancers for changes in copy number of DNA sequences. We detected frequent losses on 1p32–33 (21%), 3p21–23 (22%), 5q14–22 (36%), 6q16 (26%), 9p21–24 (22%), 16q (21%), 17p13 (48%), 18q11–21 (33%), and 19 (40%). Gains were most often noted at 1p36 (22%), 8p22–23 (24%), 8q23–24 (29%), 11q12–13 (24%), 16p (21%), 20p (38%), 20q (45%), Xp21–22 (38%), and Xq21–23 (43%), with high‐level amplifications at 6p21 (2%), 7q31 (10%), 8p22–23 (5%), 8q23–24 (7%), 11q13 (4%), 12p12–13 (4%), 17q21 (2%), 19q12–13 (2%), and 20q13 (2%). High‐level amplification at 8p22–23 has never been reported in any other cancer type and its frequency was as high as that reported for the MYC, MET, and KRAS genes. We narrowed down the smallest common amplicon to 8p23.1 by reverse‐painting FISH to prophase chromosomes. Southern blot analysis using one EST marker (D38736) clearly demonstrated that amplification of this exon‐like sequence had occurred in all three tumors in which amplifications at 8p22–23 had been detected by CGH. Our data provide evidence for several, previously undescribed, genomic aberrations that are characteristic of gastric cancers. Genes Chromosomes Cancer 24:299–305, 1999.

Amplification and over-expression of the AIB1 nuclear receptor co-activator gene in primary gastric cancers.

Our analysis of chromosomal aberrations in primary gastric cancers using comparative genomic hybridization has revealed novel, high and frequent copy number increases in the long arm of chromosome 20, indicating that this region contains novel amplified genes involved in gastric cancer progression. AIB1, a member of the steroid receptor co‐activator‐1 family, has been cloned on 20q12 as a candidate target gene for this amplification in human breast cancers. In this study, we examined the numbers of AIB1 copies as well as their expression and relation to clinico‐pathological features in 72 primary gastric cancers. AIB1 amplification was observed in 7% and over‐expression in 40% of the specimens. AIB1 amplification always coincided with its over‐expression, but several cases showed AIB1 over‐expression without amplification, suggesting that expression of AIB1 is regulated not only by gene amplification but also by other mechanisms, such as transcriptional activation, in human gastric cancer. Gastric cancers with AIB1 amplification showed extensive lymph node metastases, liver metastases and poorer prognosis compared to those without amplification. Our results suggest that amplification and over‐expression of AIB1 are likely to increase the number of malignant phenotypes of gastric cancers and that it can be expected to be useful as a marker of poor prognosis. Int. J. Cancer 89:217–223, 2000.

Fusion of MOZ and p300 histone acetyltransferases in acute monocytic leukemia with a t(8;22)(p11;q13) chromosome translocation.

Histone acetyltransferase p300 functions as a transcriptional co-activator which interacts with a number of transcription factors. Monocytic leukemia zinc finger protein (MOZ) has histone acetyltransferase activity. We report the fusion of the MOZ gene to the p300 gene in acute myeloid leukemia with translocation t(8;22)(p11;q13). FISH and Southern blot analyses showed the rearrangement of the MOZ and p300 genes. We determined the genomic structure of the p300 and the MOZ genes and the breakpoints of the translocation. Analysis of fusion transcripts indicated that the zinc finger and acetyltransferase domains of MOZ are fused to a largely intact p300. These results suggest that MOZ-p300, which has two acetyltransferase domains, could be involved in leukemogenesis through aberrant regulation of histone acetylation.

Chromosome abnormalities and karyotypic evolution in 83 patients with myelodysplastic syndrome and predictive value for prognosis.

In a chromosome study of 83 patients with myelodysplastic syndrome (MDS), 50 showed a clonally abnormal karyotype. The most frequent abnormalities were the whole or a partial loss of the long arm of chromosome 7 (−7 or 7q−) (14 patients) and a partial loss of the long arm of chromosome 5 (5q‐) (11 patients). Twenty patients with 5q− and/or −7 or 7q− had a shorter survival (median, 5 months) than those with other abnormal karyotypes (22 months) or those with a normal karyotype (28 months). In this series 30 patients were examined cytogenetically on two or more occasions during the course of their illness. Ten patients showed a further karyotypic alteration from the initial findings, and, concomitantly, their disease progressed in severity including overt leukemia. These patients had a shorter survival (median, 2 months) after the chromosome reanalysis than the other 20 patients who did not have further karyotypic changes (21 months). Thus, the prognosis of patients with MDS can be predicted more accurately by reanalyzing the chromosomes after the initial analysis.

Chromosomal aberrations in colorectal cancers and liver metastases analyzed by comparative genomic hybridization

Comparative genomic hybridization (CGH) was used to screen for changes in the number of DNA sequence copies in 30 primary colorectal cancers and 16 liver metastases, to identify regions that contain genes important for the development and progression of colorectal cancer. In primary colorectal cancer, we found frequent gains at 7p21 (36.7%), 7q31‐36 (30%), 8q23‐24 (43.0%), 12p (30%), 14q24‐32 (33.3%), 16p (40.0%), 20p (33.3%), 20q (63.3%) and 21q (36.3%), while loss was often noted at 18q12‐23 (36.7%). In metastatic tumors, there were significantly more gains and losses of DNA sequences than in primary tumors, with gains at 8q23‐24 (found in 62.5% of recurrences vs. 43.0% of primary tumors), 15q21‐26 (37.5% vs. 20.0%), 19p (43.8% vs. 20.0%) and 20q (81.3% vs. 63.3%) and losses at 18q12‐23 (50.0% vs. 36.7%). The pattern of genetic changes seen in metastatic tumors, with frequent gains at 8q23‐24 and 20q and loss at 18q12‐23, suggests the progression of colorectal cancer. We investigated a clinical follow‐up study for all patients examined by CGH and directed our attention to the genetic changes consisting of gains at 8q and 20q. The incidence of liver metastases was higher in patients with primary colorectal cancer with these genetic changes. Gains at 8q and 20q might be useful to identify patients at high risk for developing liver metastases.

Differential gene expression profiles of gastric cancer cells established from primary tumour and malignant ascites

Advanced gastric cancer is often accompanied by metastasis to the peritoneum, resulting in a high mortality rate. Mechanisms involved in gastric cancer metastasis have not been fully clarified because metastasis involves multiple steps and requires a combination of altered expressions of many different genes. Thus, independent analysis of any single gene would be insufficient to understand all of the aspects of gastric cancer peritoneal dissemination. In this study, we performed a global analysis of the differential gene expression of a gastric cancer cell line established from a primary main tumour (SNU-1) and of other cell lines established from the metastasis to the peritoneal cavity (SNU-5, SNU-16, SNU-620, KATO-III and GT3TKB). The application of a high-density cDNA microarray method made it possible to analyse the expression of approximately 21 168 genes. Our examinations of SNU-5, SNU-16, SNU-620, KATO-III and GT3TKB showed that 24 genes were up-regulated and 17 genes down-regulated besides expression sequence tags. The analysis revealed the following altered expression such as: (a) up-regulation of CD44 (cell adhesion), keratins 7, 8, and 14 (epitherial marker), aldehyde dehydrogenase (drug metabolism), CD9 and IP3 receptor type3 (signal transduction); (b) down-regulation of IL2 receptor γ, IL4-Stat (immune response), p27 (cell cycle) and integrin β4 (adhesion) in gastric cancer cells from malignant ascites. We then analysed eight gastric cancer cell lines with Northern blot and observed preferential up-regulation and down-regulation of these selected genes in cells prone to peritoneal dissemination. Reverse transcriptase–polymerase chain reaction confirmed that several genes selected by DNA microarray were also overexpressed in clinical samples of malignant ascites. It is therefore considered that these genes may be related to the peritoneal dissemination of gastric cancers. The results of this global gene expression analysis of gastric cancer cells with peritoneal dissemination, promise to provide a new insight into the study of human gastric cancer peritoneal dissemination.