Genetic status of p53 and induction of apoptosis by radiation or isoflavones in human gastric carcinoma cell lines

We have shown previously that various human cancer cell lines undergo morphological changes and internucleosomal DNA fragmentation characteristic of apoptosis after exposure to ionizing radiation or isoflavones. Here, we assessed the role of p53 gene in cell cycle and apoptosis following treatment of 11 gastric carcinoma cell lines with gamma-rays, genistein, biochanin A, or daidzein. Cell survival was measured by trypan blue staining, and apoptosis was assessed by fluorochrome staining. The rate of cell survival and apoptosis of the cells by gamma-irradiation or isoflavones did not correlate with p53 gene abnormalities. Flow cytometric measurement of DNA content demonstrated that while gamma-irradiation and genistein induced G(2) arrest, biochanin A and daidzein blocked the cell cycle of all carcinoma cells at G(1) phase. At multiple time points following irradiation, G(2) arrest was observed at 12-16 h in the wild-type and mutant p53 cell lines. Induction of p53 and p21 proteins was not observed in wild-type p53 lines after exposure to gamma-irradiation or isoflavones by Western blotting. Moreover, transfection of the wild-type p53 gene into MKN-1 cells failed to induce G(1) arrest by gamma-irradiation and genistein. Based on these results, we hypothesize that gastric cancer cells may possess a signal pathway which is different from the usual mechanisms of the p53-mediated DNA damage response in normal or hematopoietic tumor cells.

Biologic effect of human hepatocyte growth-factor on human gastric-carcinoma cell-lines

Biologic effect of human hepatocyte growth factor (hHGF), which is now known to be the same protein of scatter factor and tumor cytotoxic factor, on gastric cancer cell lines were examined. hHGF messenger RNA expression was undetectable in human gastric cancer cell lines TMK-1 (poorly differentiated adenocarcinoma) and MKN-28 (well differentiated adenocarcinoma). Human fetal lung fibroblast cell line MRC-5 and human stomach derived fibroblast ST-Fib expressed high levels of hHGF mRNA. hHGF production was also confirmed in the culture media of the fibroblast cell lines by enzyme linked immunosorbent assay. Interestingly, TMK-1, having weak expression of E-cadherin, showed marked scattering on 0.1% collagen gel with hHGF (10 ng/ml). The same scattering activity was also observed with fibroblast conditioned medium or with stomach derived fibroblast ST-Fib co-culture. Contrarily, well differentiated adenocarcinoma cell line MKN-28 maintaining strong E-cadherin expression did not show this morphologic change. The expression of c-met proto-oncogene, which encodes the receptor for hHGF, and the biochemical character of hHGF receptor did not differ significantly between TMK-1 and MKN-28. On the other hand, Western blot analysis using specific antibody to phosphotyrosine revealed a difference in phosphoprotein pattern between the two cell lines. These results indicate that hHGF produced by the stromal fibroblasts has a histologic type-specific morphogenic activity on gastric cancer cells with different expression of E-cadherin in a paracrine manner in vivo and a different post-receptor signal transduction mechanism.

Alterations of the apc gene in carcinoma cell-lines and precancerous lesions of the stomach

Somatic mutations of the APC gene in eight cancer cell lines, twelve adenomas and sixteen intestinal metaplasias of the stomach were examined. The expression of the APC mRNA and protein in eight cancer cell lines was also investigated. PCR-SSCP analysis detected mutations of the APC gene in 25% (2 out of 8) of cancer cell lines, 42% (5 out of 12) of gastric adenomas, 6% (1 out of 16) of intestinal metaplasia mucosae. Direct sequencing analysis confirmed nonsense mutations in one cancer cell line, one adenoma and one intestinal metaplasia mucosa resulted in truncation of the product, frameshift mutations in one adenoma and silent mutations in one cancer cell line and three adenomas. In addition, the KATO-III cell line, which was established from signet ring cell carcinoma, expressed very low level of APC mRNA and its APC protein could not be detected. On the other hand, the expression level of variant APC mRNA transcript which lacks exon 7 was relatively high in KATO-III. It is supposed that the variant APC mRNA transcript might contribute to the inactivation of the APC gene. These data overall provide strong evidence that changes in the APC gene play an important role in the early event of stomach carcinogenesis, especially in intestinal type gastric cancer.

Genetic abnormalities and expression of p53 in human colon carcinomas

Genetic alteration and expression of p53 was examined on matched pairs of tumor and nonneoplastic tissues of colon carcinomas and compared with clinicopathological findings. Loss of heterozygosity (LOH) of p53 locus was found in 83% (44/53) of carcinomas and the incidence of LOH increased as tumor stage progressed. Among LOH cases, 63% (5/8) showed p53 mutations, most of which occured at CpG site. Although the level of p53 mRNA in tumor tissues was lower than its nonneoplastic counterpart in 55% (6/11) of the cases, no obvious relation was detected between mRNA expression and gene alteration. Accumulation of p53 protein determined by immunohistochemistry was found in 47% (25/53) of cases regardless of allelic status nor mRNA level. p53 immunoreactivity showed a tendency to increase with tumor stage. These results indicate the diversity of p53 alterations in the development and progression of colon carcinoma.

Reduced tumorigenicity and cell motility of a gastric-carcinoma cell-line by introduction of wild-type p53 gene

Wild-type or mutant human p53 gene was transfected into a human gastric carcinoma cell line MKN-1 which shares a mutant p53 allele. Transfected wild-type p53 reduced the colony forming efficiency and tumorigenicity of MKN-1 cells. However, no difference in expression of cell adhesion molecule, oncogenes and growth factors was observed among parent, wild-type p53 and mutant p53 transfectants. In motility assay, the wild-type p53 transfectants relative to the parental or mutant p53 transfectants exhibited a decreased motility, and HGF had a greater effect on the motility of the mutant p53 transfectants, but very little effect on the motility of either the parental or wild-type transfectants. In invasion assay, mutant p53 transfectants revealed the increased invasion ability into collagen gel. These results suggest that allele loss and point mutation of p53 gene may play a critical role not only in growth but also in invasion of gastric carcinoma cells.

Regulation of PTEN expression by the SWI/SNF chromatin-remodelling protein BRG1 in human colorectal carcinoma cells

Background:

Aberrant expression of Brahma-related gene-1 (BRG1), a core component of the SWI/SNF chromatin-remodelling complex, has been implicated in cancer development; however, the biological significance of BRG1 in colorectal carcinoma (CRC) remains unknown.

Methods:

In CRC tissues, expression of BRG1 and Brahma (BRM) was investigated immunohistochemically. Colorectal carcinoma-derived DLD-1 cells were used for knockdown of BRG1 and PTEN with small interfering RNA (siRNA) and transduction of Akt. Complementary DNA (cDNA) microarray analysis was performed to explore the genes affected by BRG1.

Results:

Expression of BRG1, but not BRM, was frequently elevated in CRC specimens, and knockdown of BRG1 suppressed cell proliferation of DLD-1 cells. By cDNA microarray, we determined that PTEN expression was negatively regulated by BRG1 in DLD-1 cells, which subsequently influenced the cyclin D1 levels via the phosphoinositide 3-OH kinase (PI3K)–Akt signalling pathway. The interplay of BRG1 on cyclin D1 expression was confirmed by the introduction of Akt and knockdown of PTEN in the BRG1 siRNA-transduced DLD-1 cells. Interestingly, this positive correlation between BRG1 and cyclin D1 expression was also observed in CRC specimens.

Conclusion:

Brahma-related gene-1 has an important role in the process of CRC development by activating the PI3K–Akt signalling pathway and resultant upregulation of cyclin D1 levels.

Direct cancer-stromal interaction increases fibroblast proliferation and enhances invasive properties of scirrhous-type gastric carcinoma cells

BACKGROUND

Scirrhous-type gastric carcinoma (SGC) exhibits an extensive submucosal fibrosis and extremely poor patient prognosis. We investigated the importance of the cancer-stromal interaction in the histogenesis of SGC.

METHODS

Gastric fibroblasts NF-25 and intestinal fibroblasts NF-j2 were co-cultured with SGC-derived (HSC-39) or non-SGC-derived (HSC-57 and HSC-64) cells. To identify genes that are up- or downregulated in NF-25, complementary DNA (cDNA) microarray analysis was performed. The antibody against vascular-cell adhesion molecule-1 (VCAM-1) was used for cell growth test and immunohistochemistry. Moreover, the impact of interaction with NF-25 fibroblasts on HSC-39 cells was investigated using western blot and reverse transcription-polymerase chain reaction.

RESULTS

HSC-39 cells stimulated growth of NF-25 but not NF-j2 when co-cultured. Induction of VCAM-1 in NF-25 fibroblasts was identified, which was specific when co-cultured with HSC-39 but not with non-SGC-derived HSC-57 and HSC-64 cells. Neutralising antibody to VCAM-1 suppressed NF-25 growth in dose-dependent manners. In tissue samples, positive immunoreactivity of VCAM-1 in SGC-derived fibroblasts was significantly higher than that in non-SGC-derived fibroblasts. Furthermore, interaction with NF-25 fibroblasts not only induced the epithelial-mesenchymal transition-like change, but also expressions of matrix metalloproteinase- related genes in HSC-39 cells.

CONCLUSION

Direct interaction between SGC cells and gastric fibroblasts establishes the tumour microenvironment and reinforces the aggressiveness of SGC.

High PRL-3 expression in human gastric cancer is a marker of metastasis and grades of malignancies: an in situ hybridization study

Phosphatase of regenerating liver (PRL)-3, encoding a 22-kD low molecular weight tyrosine phosphatase, has been reported to be associated with metastasis of colorectal carcinoma. We assessed the levels of PRL-3 mRNA expression to know whether its up-regulation was involved in progression and metastasis of gastric carcinoma. Levels of PRL-3 expression in 94 human gastric adenocarcinomas and 54 matched lymph node metastases were detected by in situ hybridization and compared with clinicopathological characteristics including prognosis. High PRL-3 expression was detected in 36.2% of primary gastric carcinoma (with nodal metastasis, 55.6%; without nodal metastasis, 10%; P < 0.001) and in 74.1% of lymph node metastases. The incidence of high PRL-3 expression in lymph node metastasis was significantly higher than in primary tumors (P < 0.044). Moreover, high expression of PRL-3 was closely associated with tumor size, lymphatic invasion, venous invasion, extent of lymph node metastasis, and tumor stage. These results suggest that high PRL-3 expression may participate in the progression and metastasis of gastric carcinoma. PRL-3 might be a novel molecular marker for aggressive gastric cancer.

Assessment of microsatellite instability status for the prediction of metachronous recurrence after initial endoscopic submucosal dissection for early gastric cancer

The technique of endoscopic submucosal dissection (ESD) has been developed for en bloc resection of early gastric cancer (EGC); however, little is known about the risk of metachronous cancer in the remnant stomach after initial ESD. In this study, we investigated the correlation between microsatellite instability (MSI) status and the incidence of metachronous recurrence of gastric cancer. According to the genetic/molecular background determined with MSI status and expression levels of hMLH1 and p53 tumour suppressor, 110 EGCs removed with ESD were subclassified into three groups: the mutator/MSI-type (8%), suppressor/p53-type (45%) and unclassified type (47%). Interestingly, patients with the mutator/MSI-type tumour had a high incidence (67%) of metachronous recurrence of gastric cancer within a 3-year observation after initial ESD, which was significantly higher than those with the suppressor/p53-type and unclassified type tumours (P<0.01). Although we investigated mucin phenotypes, there was no correlation between mucin phenotype and the recurrence of EGC. These findings suggest that subclassification of molecular pathological pathways in EGCs is required for the assessment of patients with a high risk of recurrent gastric cancer. The information delivered from our investigation is expected to be of value for decisions about therapy and surveillance after ESD.

Cerebral venous thrombosis in adult nephrotic syndrome due to systemic amyloidosis

Although venous thrombosis is one of the common complications in nephrotic patients, cerebral venous thrombosis (CVT) is rarely reported. CVT is so difficult to be detected by conventional diagnostic methods that it is sometimes overlooked despite its potential severity. We report a 79-year-old female with nephrotic syndrome due to systemic amyloidosis who suddenly altered mental status during her hospitalization. The underlying etiology had been not identified by physical examinations, various laboratory data, and repeated computed tomography, and finally she died. The post-mortem examination showed a massive thrombus impacted in intracranial left-sided transverse and sigmoid sinus. This case suggests that CVT can occur in a nephrotic patient who presents unexplained neurological signs and symptoms, which might not be detected only through conventional diagnostic tests.

Increased expression but not genetic alteration of BRG1, a component of the SWI/SNF complex, is associated with the advanced stage of human gastric carcinomas

BRG1, a component of the SWI/SNF complex, regulates gene transcription through chromatin remodeling. Certain human cancer cell lines have been shown to contain homozygous deletions or mutations, half of which are concentrated in exons 4 and 10, resulting in aberrant BRG1 expression. We examined the expression of BRG1 in 38 gastric carcinomas and corresponding nonneoplastic mucosa by using the quantitative real-time RT-PCR method. Twenty-three carcinomas (61%) showed increased BRG1 expression in tumor tissue in comparison with that in nonneoplastic mucosa. The T/N ratio (the expression level of BRG1 mRNA in tumor tissues relative to those in corresponding nonneoplastic mucosa) in advanced cases of gastric carcinoma (stages III and IV) was significantly higher than that in cases of stage I and II carcinoma (p = 0.029). Furthermore, gastric carcinomas with lymph node metastasis showed a tendency to express BRG1 at a higher level than gastric carcinomas without metastasis (p = 0.097). We also searched for genetic alterations of the BRG1 gene in 8 gastric carcinoma cell lines and 33 primary gastric carcinomas by PCR-SSCP analysis. No SSCP variants in exons 4, 10 and 16 of the BRG1 gene were found in both gastric carcinoma cell lines and primary gastric carcinomas. These results suggest that, although genetic abnormality of BRG1 might be rare, an increased expression of BRG1 might be associated with the development and progression of gastric carcinoma.

Infrequent loss of heterozygosity of the major tumour suppressor genes in Indian oral cancers

The loss of heterozygosity (LOH) in tumour suppressor gene loci such as p53, retinoblastoma (rb) and adenomatous polyposis coli (apc) were analyzed in oral cancer tissues with matched controls by employing polymerase chain reaction based/restriction fragment length polymorphism (PCR-RFLP), variable number of tandem repeats (PCR-VNTR) analysis and microsatellite assay. The PCR-RFLP analysis showed an infrequent LOH in rb (17%), p53 (11%) and apc (10%) loci in these cases. The microsatellite assay also revealed only a low frequency of LOH in the microsatellite markers such as TP53 (25%), D5S505 (10%) and D3S1067 (0%) in the same samples. In contrast to the present study, similar studies from Western countries have reported a high frequency of LOH in p53, rb and apc genes in oral cancer tissues. The present preliminary study indicates that the gene aberration by LOH may be an insignificant mechanism in Indian oral cancers with respect to the tumour suppressor genes examined.

Promoter methylation status of the DNA repair genes hMLH1 and MGMT in gastric carcinoma and metaplastic mucosa

Hypermethylation of CpG islands in the promoter region is associated with the silencing of a variety of tumor suppressor genes. DNA repair genes human Mut L homologue 1 (hMLH1) and O(6)-methylguanine-DNA methyltransferase (MGMT) have been shown to be hypermethylated in certain carcinomas. We studied DNA methylation of CpG islands in hMLH1 and MGMT in 50 gastric carcinomas and 10 intestinal metaplastic mucosa samples. We analyzed the methylation status of hMLH1 and MGMT using methylation-specific polymerase chain reaction and DNA sequencing analysis. We measured protein levels of hMLH1 using Western blot and immunohistochemical analysis. CpG island hypermethylation of hMLH1 and MGMT was detected in 11 (22%) and 8 (16%) of the 50 gastric tumors, respectively. Hypermethylation of the promoter was more common in intestinal-type gastric carcinomas than in poorly diffuse-type gastric carcinomas (p = 0.016 and 0.021, respectively; Fisher's exact test). However, hMLH1 promoter hypermethylation did not coincide with MGMT promoter hypermethylation except in 1 patient. Hypermethylation of the hMLH1 promoter but not the MGMT promoter occurred in intestinal metaplastic mucosae. Immunohistochemical analysis revealed a corresponding reduction in hMLH1 protein expression in some of the intestinal metaplastic mucosae. Our results suggest that at least two types of promoter methylation participate in the development of gastric carcinoma. Tumor-specific promoter hypermethylation of hMLH1 may be an early event in carcinogenesis in the stomach.

Expression of MRE11 complex (MRE11, RAD50, NBS1) and hRap1 and its relation with telomere regulation, telomerase activity in human gastric carcinomas

The MRE11 complex (MRE11, RAD50, NBS1) are required for the repair of DNA double-strand breaks and have another important function in regulating telomere length. The silent information regulator (Sir) proteins required for telomere position effect also bind telomeres. hRap1 protein is a human ortholog of yeast Rap1 which regulates telomere length by interacting with TRF2 and is recruited to telomeres by TRF2. We examined the expression of the MRE11 complex (MRE11, RAD50, NBS1), Sir2 and hRAP1 in 20 gastric carcinomas by reverse transcription polymerase chain reaction and then analyzed the relation between telomerase activity and other telomerase components such as human telomerase reverse transcriptase (TERT), human telomerase RNA component (hTR), human telomerase-associated protein (TEP1), telomeric repeat binding factor 1 (TRF1), TRF2- and TRF1-interacting, ankyrin-related ADP-ribose polymerase (tankyrase) as well as TRF1-interacting nuclear protein 2 (TIN2). Of twenty gastric carcinomas examined, 13 (65%), 14 (70%), 16 (80%), 12 (60%) and 13 (65%) expressed MRE11, RAD50, NBS1, Sir2 and hRap1 at higher levels than corresponding nonneoplastic gastric mucosa, respectively. No obvious correlation was observed between MRE11 complex expression and telomerase activity or expression of TERT, hTR, TEP1, tankyrase and TIN2. Carcinomas with high TRF1 expression expressed significantly higher levels of MRE11 and RAD50 than those with low TRF1 expression (p < 0.05). On the other hand, carcinomas with high TRF2 expression expressed significantly higher levels of MRE11, NBS1 and hRap1 than those with low TRF2 expression (p < 0.05). These results suggest that gastric carcinomas with high TRF1 and TRF2 expression may need a large quantity of the MRE11 complex. Moreover, gastric carcinomas with high TRF1 expression may require a large quantity of hRap1.

Molecular diagnosis of gastric cancer: present and future

Although histopathological diagnosis is extremely useful for the definitive as well as the supportive diagnosis of gastric cancer in clinical practice, it is limited in certain respects. Over the past 15 years, integrated research in molecular pathology has clarified the details of genetic and epigenetic abnormalities of cancer-related genes in the course of the development and progression of gastric cancer. These abnormalities, which include telomerase activation, genetic instability, and abnormalities in oncogenes, tumor suppressor genes, cell-cycle regulators, cell adhesion molecules, and DNA repair genes, could be effective markers in the molecular diagnosis of gastric cancer. It is possible that the molecular analysis of these alterations in histopathology specimens may overcome deficiencies in diagnoses that depend only on histomorphology, and, consequently, we may be able to improve the differential diagnosis of cancer, obtain information on the grade of malignancy, and identify patients at high risk of developing multiple primary cancers. In Hiroshima, we have established a system of molecular-pathological diagnosis as a routine service; about 5,000 lesions of the stomach have been subjected to this diagnosis, and much useful information has been obtained. In the near future, genetic analysis by means of DNA microarray may become routine in the diagnosis of gastric cancer. Genetic analysis of histopathology specimens may make clear the characteristics of individual cancers; indicating the common and specific features of molecular pathogenesis that may be directly connected with gene therapy or molecular-targeted therapy. By analyzing the relationship between single-nucleotide polymorphisms and cancer susceptibility, we will be able to obtain information on cancer prevention from histopathology samples.

Interleukin-15 expression is associated with malignant potential in colon cancer cells

Interleukin 15 (IL-15 mRNA expression was detected in human colorectal cancer cells (Colo320, WiDr, TCO and DLD1) by the reverse transcriptase-polymerase chain reaction (RT-PCR). Only Colo320 and WiDr cells secreted IL-15 culture medium. With IL-15 treatment, all cell lines grew at a rate of 120-180% of that of nontreated cells. A binding assay with (125)I-labeled IL-15 showed binding activity to IL-15 in Colo320 (K(d): 0.098 nM) cells. IL-15 also reversed the growth inhibition caused by serum starvation in Colo320 cells. IL-15-induced cell growth in regular and serum-free media was abrogated by anti-IL-15 antibody treatment in Colo320 cells. Moreover, IL-15 treatment reduced doxorubicin-induced cytostasis and cytolysis in Colo320 cells by 50%. The invasion capacity of IL-15-treated Colo320 cells was 5.3 times that of untreated cells. Immunoblotting showed that IL-15-treated Colo320 cells exhibited downregulation of p21Waf1 and Bax, and upregulation of Bcl-2, phospho-AKT, MMP9/MMP2, and VEGF. Finally, immunostaining of human colon cancer revealed that 33 (70%) of 47 Dukes' C cases showed IL-15 expression in cancer cells, whereas only 16% of Dukes' B cases did (p < 0.0001). IL-15 may play important roles in cell proliferation, invasion, and metastasis of human colorectal cancer.

Expression of Bub1 gene correlates with tumor proliferating activity in human gastric carcinomas

Bub1 plays an important role at the spindle assembly checkpoint to prevent cell cycle progression following spindle damage. We examined the expression of human Bub1 mRNA in 20 gastric carcinoma tissues and corresponding nonneoplastic mucosas by reverse transcriptase-polymerase chain reaction and analyzed the relation with proliferative activity monitored by the expression of proliferating cell nuclear antigen (PCNA) on Western blotting as well as Ki-67 labeling index by immunohistochemistry. Increased expression of Bub1 mRNA was detected in 8 (40%) of the gastric carcinomas in comparison with their nonneoplastic counterparts, while 4 (20%) expressed Bub1 at lower levels. The expression of Bub1 mRNA was confirmed by in situ hybridization. The expression levels of Bub1 mRNA were well correlated with the levels of PCNA protein in 16 (80%) gastric carcinoma cases. The examination of Ki-67 labeling indices proved the close correlation between the expression levels of Bub1 and proliferating activity. These findings suggest that mRNA expression of human Bub1 gene is closely associated with the tumor-proliferating activity. Since genetic alterations of human Bub1 rarely occur in gastrointestinal cancers, the functional machinery of Bub1 to prevent cell cycle progression into anaphase might be well preserved in gastric carcinomas even with high proliferative activity.

Prospective study of Ki-67 labeling index in the mucosa adjacent to cancer as a marker for colorectal cancer metastasis

Multivariate regression analysis has shown that Ki-67 labeling index in the mucosa adjacent to cancer was the most significant marker for colorectal cancer metastasis among several metastasis-related parameters according to our previous retrospective data base (7). We have performed a prospective study to ascertain whether Ki-67 labeling index in the mucosa adjacent to cancer is a useful preoperative diagnostic marker for colorectal cancer metastasis. In 182 registered cases colonoscopically biopsied, we performed surgical resection of the cancer in 37 adenocarcinoma cases, which were registered in the study. In 31 out of the 37 cases except for 6 cases with an insufficient amount of non-neoplastic mucosa, preoperative diagnosis for metastasis was performed using the Ki-67 cutoff line. The cutoff line was set at 15% according to our previous retrospective database. The preoperative diagnosis for metastasis was compared to the pathological findings of the resected specimen. The incidences of correct diagnosis for metastasis was 81% (25/31). There were 3 false positive cases and 3 false negative cases in Dukes' A-B and Dukes' C, respectively. The mean Ki-67 labeling index in the mucosa adjacent to cancer of Dukes' A-B and Dukes' C-D cases, except for the 6 misdiagnosed cases, was 7.4+/-5.0% and 29.9+9.8%, being significant at p<0.0001 by unpaired Mann-Whitney U test. These results suggest that Ki-67 labeling index in the mucosa adjacent to cancer might be a good marker for metastasis in colorectal cancer.

Promoter hypermethylation of MGMT is associated with protein loss in gastric carcinoma

Aberrant methylation of CpG islands within promoter regions is associated with transcriptional inactivation of various tumor suppressor genes in neoplasms. Recently, O(6)-methylguanine-DNA methyltransferase, MGMT, was shown to be hypermethylated in certain carcinomas, resulting in loss of MGMT protein. We studied DNA methylation of CpG islands of the MGMT gene by methylation specific PCR in 26 gastric carcinoma tissues and 8 gastric carcinoma cell lines for comparison with levels of MGMT protein expression. In addition, we examined p53 mutation status in the same tissues by PCR-SSCP analysis for comparison with MGMT protein expression levels. In total, promoter hypermethylation of the MGMT gene was found in 8 (31%) of the 26 gastric carcinomas with reduced expression of MGMT protein, whereas the hypermethylation was not detected in the 18 carcinomas with non-reduced MGMT expression. MGMT protein expression levels were associated with promoter hypermethylation of MGMT (p = 0.0001; Mann-Whitney test); however, MGMT expression was not associated with p53 mutation status (p = 0.461; Mann-Whitney test). Among in gastric carcinoma cell lines, the TMK-1 cell line showed loss of the MGMT protein association with promoter hypermethylation and this loss was rectified by treatment with a demethylating agent, 5-Aza-2'-deoxycytidine. Our results suggest that transcriptional inactivation of MGMT by aberrant methylation of the promoter region may participate in carcinogenesis in the stomach.

DNA methylation status of hMLH1, p16(INK4a), and CDH1 is not associated with mRNA expression levels of DNA methyltransferase and DNA demethylase in gastric carcinomas

DNA methyltransferase and DNA demethylase are enzymes potentially affecting promoter methylation status. We examined levels of DNA methyltransferase (DNMT1, DNMT3a, DNMT3b) and DNA demethylase (MBD2) mRNA expression by semi-quantitative RT-PCR. In addition, we examined promoter methylation status of hMLH1, p16(INK4a), and CDH1 by methylation-specific PCR since all three of these genes are reported to be hypermethylated in gastric carcinoma. MBD2 appeared to be down-regulated in neoplasms. The levels of DNMT1, DNMT3a, DNMT3b, and MBD2 mRNA expression were not associated with either tumor stage or histologic type. Promoter hypermethylation of hMLH1, p16(INK4a), and CDH1 was detected in 5/20 (25%), 8/20 (40%) and 8/20 (40%) of gastric carcinomas, respectively. There was no clear relation between DNA methylation status of hMLH1, p16(INK4a), and CDH1 and the mRNA expression levels of DNMT1, DNMT3a, DNMT3b or MBD2. We divided the examined cases into two groups according to the number of hypermethylated genes. Cases with more than two hypermethylated genes comprised a hypermethylation group, and cases with no hypermethylation comprised a non-hypermethylation group. We found no group association for levels of DNMT1, DNMT3a, DNMT3b, and MBD2 mRNA expression. Our results suggest that the mRNA expression levels for pro-methylating (DNMT1, DNMT3a, DNMT3b) and anti-methylating (MBD2) enzymes is not a critical determinate of tumor-specific promoter hypermethylation of hMLH1, p(16INK4a), or CDH1 in gastric carcinoma.

Expression of telomeric repeat binding factor 1 and 2 and TRF1-interacting nuclear protein 2 in human gastric carcinomas

Telomeric repeat binding factor 1 (TRF1) and 2 (TRF2) may play key roles in the maintenance of telomere function. TRF1 negatively regulates telomere elongation, while TRF2 protects the chromosome ends by inhibiting end-to-end fusions. We examined the expression of TRF1 and TRF2 in 20 gastric carcinomas by reverse transcription polymerase chain reaction and then analyzed the relation with telomerase activity and other telomerase components such as human telomerase reverse transcriptase (TERT), human telomerase RNA component (hTR), human telomerase-associated protein (TEP1) and TRF1-interacting, ankyrin-related ADP-ribose polymerase (tankyrase) as well as TRF1-interacting nuclear protein 2 (TIN2). Of 20 gastric carcinomas examined, 10 (50%) and 12 (60%) expressed TRF1 and TRF2 at higher levels than did non-neoplastic mucosa, respectively. No obvious correlation was observed between TRF1 expression and telomerase activity or expression of TERT, hTR and TEP1. Carcinomas with high TRF1 expression expressed significantly higher levels of tankyrase and TIN2 than did those with low TRF2 expression (p<0.05). The telomerase activities and the levels of TERT, hTR and TEP1 showed tendency to be lower in tumors expressing TRF1 at low levels, although it was not significant. On the other hand, carcinomas with short telomere length (shorter than 2 Kbp) expressed significantly stronger telomerase activities and higher TRF1 expression (p<0.05) and tended to express TRF2 and TIN2 at higher levels than those with long telomere length. The results suggest that gastric carcinomas with short telomeres need high levels of telomerase activity and large quantity of TRFs and TIN2, whereas those with long telomeres do not require high levels of telomerase activity and telomere associated proteins.

Inactivation of retinoic acid receptor beta by promoter CpG hypermethylation in gastric cancer

Inactivation of nuclear retinoic acid receptor beta (RARbeta) expression is implicated in tumorigenesis. We hypothesized that loss of RARbeta in gastric cancer cells may occur as a result of multiple factors, including epigenetic modifications which alter RARbeta promoter chromatin structure. We examined hypermethylation of CpG islands present in the RARbeta promoter by methylation-specific PCR and the expression of RARbeta in gastric cancer cell lines and tissues. Three (MKN-28, -45 and -74) out of eight gastric cancer cell lines had a loss of RAR expression associated with promoter methylation. RARbeta expression was retrieved in these cell lines by treatment with 5-azacytidine or by the histone deacetylase inhibitor trichostatin A. Promoter hypermethylation was detected in 64% (7/11) of gastric carcinoma tissues with reduced expression of RARbeta, whereas it was detected in 22% (2/9) of tumors with retained RARbeta expression. To investigate the functions of exogenous RARbeta in gastric cancer cells, we transfected a retroviral RARbeta expression vector (LNSbeta) into MKN-28 cells that have hypermethylation of the RARbeta promoter. Overexpression of RAR in MKN-28 cells appeared to regulate the expression of DNA methyltransferase and DNA demethylase and the acetylation of hitone H4. These results suggest that the transcriptional inactivation of the RARbeta by promoter CpG hypermethylation is frequently associated with gastric carcinoma. Our data also suggests that DNA methylation plays a pivotal role in establishing and maintaining an inactive state of RARbeta by rendering the chromatin structure inaccessible to the transcription machinery.

No mutations of the Bub1 gene in human gastric carcinomas

Chromosomal instability in colorectal cancers is associated with functional loss of a mitotic check point partly due to mutations of the Bub1, one of the mitotic check point genes. However, mutation of coding sequences of human Bub1 gene has not been fully elucidated in gastric carcinomas. We performed sequencing analysis on reverse transcriptase-polymerase chain reaction (RT-PCR) product of the Bub1 cDNA (entire coding sequence) from 5 human gastric carcinomas as well as on genomic PCR products of Bub1 kinase domain from 7 gastric carcinoma tissues. Although sequencing analysis of the Bub1 cDNA revealed several point mutations in 2 gastric carcinoma cases, we could not confirm the mutations by analyzing genomic DNA. Furthermore, genomic DNA sequencing revealed no mutations in the kinase domain of the Bub1 gene in any gastric carcinoma examined. These results suggest that mutational inactivation of the Bub1 gene might not play a key role in human stomach carcinogenesis.

Genetic and epigenetic changes in stomach cancer

Genetic and epigenetic alterations of multiple cancer-related genes and molecules are implicated in the development and progression of human gastric carcinomas. Reactivation of telomerase, inactivation of p53 tumor suppressor gene, overexpression of cyclin E, and reduced expression of p27 KIP1 by disorganized degradation in proteasome are common events of both well-differentiated and poorly differentiated gastric adenocarcinomas. Inactivation of hMLH1 mismatch repair gene by CpG hypermethylation resulting in microsatellite instability, amplification of c-erbB2 oncogene, inactivation of APC tumor suppressor gene, and K-ras mutations are preferentially associated with well-differentiated gastric cancer. Conversely, reduction or loss of E-cadherin and catenins by both mutation and CpG hypermethylation and K-sam and c-met oncogene amplification are necessary for the development and progression of poorly differentiated or scirrhous gastric carcinomas. Interaction between cancer cells expressing c-met and hepatocyte growth factor from stromal cells is implicated in morphogenesis of gastric cancer.

Overexpression of retinoic acid receptor beta induces growth arrest and apoptosis in oral cancer cell lines

Expression of retinoic acid receptor beta (RARbeta) is reported to be absent or down-regulated in oral squamous cell carcinomas. Recently, we found that the growth-inhibitory effect of 9-cis-retinoic acid (9CRA) on oral squamous cell carcinoma may depend on the expression levels of endogenous RARbeta. In order to clarify the role of RARbeta in growth and differentiation, we transfected RARbeta expression vector into oral squamous carcinoma cell lines, HSC-4 and Ho-1-N-1. Both RARbeta-transfected cell lines displayed growth inhibition. Moreover, RARbeta-transfected clones underwent morphological changes, and RARbeta-transfected HSC-4 clones underwent apoptosis even in the absence of 9CRA treatment. In contrast, RARbeta-transfected Ho-1-N-1 clones exhibited cell cycle arrest without undergoing apoptosis initially; however, apoptosis was induced in these cells after 6 days of 9CRA treatment. RARalpha and RARgamma expression was reduced at both the protein and mRNA levels in RARbeta transfectants, whereas the expression of retinoid X receptor alpha (RXRalpha) was not altered. RARb transfectants exhibited alterations in the levels of cell cycle-associated proteins, histone acetyltransferase (HAT) and apoptosis-associated proteins. After 6 days of 9CRA treatment, RARbeta transfectants overexpressed Waf1 / Cip1 / Sdi1 / p21, Kip1 / p27, chk1, p300 / CBP, BAX, Bak, Apaf 1, caspase 3 and caspase 9. Conversely, E2F1, cdc25B and HDAC1 were down-regulated in these transfectants. In addition, histone H4 acetylation was induced in RARb transfectants. These findings suggest that histone acetylation mediated by histone acetyltransferase and p300 / CBP may play a role in the growth arrest and apoptosis induced by RARbeta transfection in oral squamous cell carcinoma.

Effect of trichostatin A on cell growth and expression of cell cycle- and apoptosis-related molecules in human gastric and oral carcinoma cell lines

The effect of trichostatin A (TSA), histone deacetylase inhibitor, on cell growth and the mechanism of growth modulation was examined in 8 gastric and 3 oral carcinoma cell lines which included 9-cis-retinoic acid resistant (MKN-7 and Ho-1-N-1) and IFN-beta resistant cell lines (MKN-7, -28 and -45). TSA inhibited growth in all cell lines examined. Apoptotic cell death was confirmed by apoptotic ladder formation and induction of a cleaved form (85 kDa) of poly (ADP-ribose) polymerase (PARP) induction. TSA enhanced the protein expression of p21(WAF1), CREB-binding protein, cyclinE, cyclin A, Bak and Bax, while it reduced the expression of E2F-1, E2F-4, HDAC1, p53 and hyperphosphorylated form of Rb. Furthermore, TSA induced morphological changes, such as elongation of cytoplasm and cell-to-cell detachment, in gastric and oral carcinoma cell lines. These results suggest that TSA may inhibit cell growth and induce apoptosis of gastric and oral carcinoma cells through modulation of the expression of cell cycle regulators and apoptosis-regulating proteins.

Effect of trichostatin A on cell growth and expression of cell cycle- and apoptosis-related molecules in human gastric and oral carcinoma cell lines

The effect of trichostatin A (TSA), histone deacetylase inhibitor, on cell growth and the mechanism of growth modulation was examined in 8 gastric and 3 oral carcinoma cell lines which included 9-cis-retinoic acid resistant (MKN-7 and Ho-1-N-1) and IFN-beta resistant cell lines (MKN-7, -28 and -45). TSA inhibited growth in all cell lines examined. Apoptotic cell death was confirmed by apoptotic ladder formation and induction of a cleaved form (85 kDa) of poly (ADP-ribose) polymerase (PARP) induction. TSA enhanced the protein expression of p21(WAF1), CREB-binding protein, cyclinE, cyclin A, Bak and Bax, while it reduced the expression of E2F-1, E2F-4, HDAC1, p53 and hyperphosphorylated form of Rb. Furthermore, TSA induced morphological changes, such as elongation of cytoplasm and cell-to-cell detachment, in gastric and oral carcinoma cell lines. These results suggest that TSA may inhibit cell growth and induce apoptosis of gastric and oral carcinoma cells through modulation of the expression of cell cycle regulators and apoptosis-regulating proteins.

Molecular characteristics of eight gastric cancer cell lines established in Japan

Molecular characterization of eight gastric cancer cell lines established in Japan are summarized according to the genetic and epigenetic alterations and growth factor status. TMK-1 poorly differentiated adenocarcinoma cell line harbors mutant p53 tumor suppressor gene and rearrangement of p15MTS2. MKN-1 adenosquamous carcinoma line with mutant p53 reveals silencing of E-cadherin by promoter CpG hypermethylation. MKN-7 well-differentiated adenocarcinoma cell line has amplification of c-erbB2 oncogene and cyclin E gene. MKN-28 well-differentiated adenocarcinoma cell line reveals mutations in p53 and APC tumor suppressor genes and silencing of CD44. The MKN-45 poorly differentiated adenocarcinoma cell line with wild-type p53 is characterized by homozygous deletion of p16CDKN2/MTS1/INK4A and p15MTS2, amplification of c-met oncogene and promoter mutation of E-cadherin. MKN-74 derived from moderately differentiated tubular adenocarcinoma has wild-type p53. KATO-III signet ring cell carcinoma line has genomic deletion of p53, amplification of K-sam and c-met oncogene and mutation of E-cadherin. HSC-39 signet ring cell carcinoma cell line harboring p53 missense mutation has homozygous deletion of p16CDKN2/MTS1/INK4A and p15MTS2, amplifications of c-myc, c-met, K-sam and CD44 gene and mutation in beta-catenin gene.

Distribution of germline BAT-40 poly-adenine tract microsatellite variants in the Japanese

Distribution of allelic variants of a poly-adenine tract microsatellite named BAT-40, locating at intron 2 of 3-beta-hydroxysteroid dehydrogenase gene, were investigated in 412 Japanese individuals free from mismatch repair gene defect. Out of them, 60 (14.6%) were heterozygotes for BAT-40, which is significantly lower than that reported in Europeans. Observed allelic variants in the Japanese ranged from 17- to 46-adenine repeats with different distribution pattern from those reported in the Americans or Europeans. These data will provide significant background knowledge for the evaluation of microsatellite instability in cancer DNA from the Japanese population.

Genetic and epigenetic alterations in multistep carcinogenesis of the stomach

An accumulation of multiple genetic and epigenetic alterations of oncogenes, tumor suppressor genes, DNA repair genes, cell cycle regulators, cell adhesion molecules, and the growth factor/receptor system is involved in the course of multistep conversion of normal epithelial cells to clinical gastric cancer. Some of them differ depending on the histological type, well-differentiated (intestinal) and poorly differentiated (diffuse) types, suggesting the presence of two distinct genetic pathways. Genetic instability, chromosomal instability (telomere reduction), and immortality (activation of telomerase and expression of telomerase reverse transcriptase: TERT) participate in the initial step of stomach carcinogenesis. Because TERT protein expression precedes the telomerase activities in precancerous lesions, TERT expression may be a prerequisite for telomerase activation. The cyclin E gene is amplified in 15%-20% of gastric cancer. Reduced expression of a cyclin-dependent kinase (CDK) inhibitor, p27Kip1, is frequently found in gastric cancer associated with high grade malignancy. E2F-1, an important downstream target of cyclins/CDKs, is overexpressed in about 40% of gastric carcinomas, whereas gene amplification of E2F-1 rarely occurs. Loss of heterozygosity (LOH) of p73, the p53-related new tumor suppressor gene, preferentially occurs in well-differentiated adenocarcinomas of foveolar type expressing pS2, a gastric-specific trefoil factor, indicating the importance of p73 LOH in the genesis.

[Carcinogenesis through abnormalities of DNA repair genes]

Mechanisms of carcinogenesis through abnormalities of DNA repair genes are overviewed. Inactivation of DNA mismatch repair(MMR) gene(s) observed in tumors of hereditary non-polyposis colorectal cancer induces frameshift mutator mutation in MMR genes themselves, growth inhibitory genes and apoptosis inhibitory genes providing favorable genetic background for a malignant clone to be expanded. Deficiency of nucleotide excision repair that is usually employed for the removal of pyrimidine dimer formed by ultraviolet-irradiation in xeroderma pigmentosum (XP) causes hypersensitivity of the skin to sunlight as well as increased risk of skin cancer. Strand specificity and absence of hot spots for p53 tumor suppressor gene mutations was reported in ultraviolet induced skin cancers of XP model mice.

Effect of 9-cis-retinoic acid on oral squamous cell carcinoma cell lines

Retinoic acid (RA) has been shown to be effective in suppressing premalignant lesions and preventing second primary malignancies in patients cured of squamous cell carcinoma of the head and neck. However, the precise mechanisms of these effects are still uncertain. In the present study, we examined the effect of 9-cis-RA on the growth of six oral cancer cell lines (HSC-2, HSC-3, HSC-4, Ca9-22, Ho-1-N-1 and Ho-1-u-1). In addition, the relationship among growth and differentiation of tumor cells, RA responsiveness and the expression of nuclear retinoic acid receptors were also investigated. Among the six cell lines examined, five (HSC-2, HSC-3, HSC-4, Ca9-22 and Ho-1-u-1) displayed growth inhibition after treatment with 1x10(-6) M 9-cis-RA, while Ho-1-N-1 cells were resistant to 9-cis-RA. The expression level of RARbeta in 9-cis-RA resistant Ho-1-N-1 cells was very low in comparison with the sensitive cell lines. On the other hand, all of the six the cell lines expressed RARalpha, RARgamma, and RXRalpha at various levels. 9-cis-RA induced accumulation of cell population in G1 phase in HSC-3 cells on the 6th day of the treatment, followed by a marked reduction in the levels of hyperphosphorylated pRB, whereas p53 level was not altered. Interestingly, 9-cis-RA induced transiently the expression of p21(Waf1/Cip1), p27(Kip1), p300, CBP, BAX, Bak and bcl-2 proteins, respectively. This effect was associated with reduction of cyclin D1, cdk4 and CDK-activating kinase (cyclin H and cdk7) protein in HSC-3 cells. These results suggest that the growth inhibitory effect of 9-cis-RA on oral squamous cell carcinoma may depend on the expression levels of RARs, especially RARbeta proteins and RXRalpha proteins, and that 9-cis-RA may provide a powerful therapeutic agent for head and neck cancers.

Helicobacter pylori infection and carcinogenesis of the stomach

INTRODUCTION

Human stomach carcinogenesis occurs after a multi-step process of genetic and epigenetic alterations in oncogenes, tumor-suppressor genes, cell-adhesion molecules, telomere and telomerase activity as well as genetic instability at several microsatellite loci.

RESULTS AND DISCUSSION

These sequential alterations found in gastric cancer differ between the two histological types, indicating that different genetic pathways exist for well-differentiated or intestinal-type and poorly differentiated or diffuse-type gastric cancers, even though both types of gastric cancer may arise from epithelial "stem cells", which express human telomerase reverse transcriptase (hTERT) protein and telomerase activity. Infection with Helicobacter pylori, which evidently causes the release of reactive oxygen species (ROMs) and reactive nitrogen species (NO), may be a strong trigger for "stem cell" hyperplasia in intestinal metaplasia, followed by telomere reduction and increased telomerase activity as well as hTERT overexpression. They may precede DNA replication error, DNA hypermethylation, CD44 abnormal transcript, and p53 mutations, all of which occur in at least 30% of intestinal metaplasias as early events of multi-step pathogenesis of well-differentiated type gastric cancer. Here, we propose a new concept for gastric preneoplasic lesion, "metaplastic dysplasia", based on our molecular observations.

DNA hypermethylation at the pS2 promoter region is associated with early stage of stomach carcinogenesis

pS2, a member of the trefoil peptide family, has been suggested to be a gastric-specific tumor suppressor. We examined the expression of pS2 in gastric carcinomas, adenomas and non-neoplastic mucosa and analyzed the DNA methylation in the pS2 promoter. Reduced expression of pS2 was frequently associated with well-differentiated adenocarcinomas. The CpG sites within the promoter region of the pS2 gene were methylated in pS2-negative gastric carcinoma cell lines whereas it was not in pS2-positive cell line. The promoter methylation was detected in gastric carcinoma tissues and intestinal metaplasia with reduced pS2 expression whereas none of the carcinomas with preserved pS2 expression showed the promoter methylation. These findings suggest that reduced expression of pS2 due to the promoter methylation may participate in an early stage of stomach carcinogenesis, especially of well differentiated type.

Chromophobe renal cell carcinoma with osseous metaplasia: a case report

A 60-year-old Japanese male with a chromophobe cell carcinoma of his left kidney is reported. The tumor, 18 x 27 mm in size, was incidentally found by abdominal ultrasonography. Computed tomography and magnetic resonance imaging demonstrated a well-demarcated solid tumor arising from the lower pole of the left kidney. Histopathological examination of the surgically removed tumor revealed that it was composed of solid sheets of cancer cells having abundant and slightly eosinophilic reticular cytoplasm with accentuated cell membranes making up a plant cell-like appearance. Electron microscopic examination demonstrated numerous intracytoplasmic microvesicles. Although the tumor cells were positive for cytokeratin and epithelial membrane antigen, they did not show vimentin immunoreactivity. The unique histological finding of this tumor from other reported renal chromophobe carcinomas was that it had a peripheral fibrotic area with a focus of metaplastic ossification.

Microsatellite instability in squamous cell carcinomas and dysplasias of the esophagus

Microsatellite instability (MSI) caused by the defective functions of mismatch repair genes plays an important role in the carcinogenesis of gastrointestinal tumors. However, little is known about the role of MSI in esophageal carcinogenesis. In the present study, we conducted microsatellite assays on 41 esophageal carcinomas and also on 44 dysplasias of the esophagus with 7 separate microsatellite loci. MSI was detected in 17 cases (42%) among 41 esophageal carcinomas. MSI negative cases revealed greater lymph node metastasis, metastasis at a more advanced stage, a higher recurrence level and a poorer prognosis (statistically not significant). In the analysis of dysplasias, MSI was detected in 26 lesions (59%) among 44 lesions. Interestingly, MSI was detected in 21 lesions (78%) from the mutator phenotype dysplasias, but detected in only 5 lesions (29%) from the non-mutator phenotype cases. Although the significance of MSI in esophageal carcinoma was not clear, these results indicate that MSI occurs in the early stage of esophageal carcinogenesis.

Cloning of a human hepatocyte growth factor/scatter factor transcription variant from a gastric cancer cell line HSC-39

A new transcription variant of hepatocyte growth factor/scatter factor (HGF/SF) was cloned from human gastric cancer cell line HSC-39. Northern blot analysis of eight human gastric cancer cell lines (TMK-1, MKN-1, MKN-7, MKN-28, MKN-45, MKN-74, KATO-III and HSC-39) demonstrated that HSC-39 cells expressed a 1.3 kb abnormal HGF/SF transcript. Screening of 1 x 10(6) colonies of cDNA library from HSC-39 constructed in pAP3neo mammalian expression vector selected four positive clones containing HGF/SF transcript. Among them, two contained a 1.3 kbp insert detecting the identical transcript to that obtained with HGF/SF probe by Northern blotting. Deoxynucleotide sequencing of the 1.3 kbp insert revealed that it was composed of a part of HGF/SF cDNA from exon 14 to exon 18, corresponding to the whole sequence of HGF/SF light chain, with 5' 75 nucleotides unrelated to any sequence involved in HGF/SF.

Idiopathic granulomatous meningoencephalitis presenting as an intracranial tumor

A 2-year-old girl presented with a single episode of generalized seizure. Magnetic resonance imaging examination showed an intracranial mass with a diameter of 2.5 cm in the right parieto-occipital region of the cerebrum. These clinicoradiological findings were suggestive of intracranial tumor. Histologically, fibroblastic proliferation of storiform pattern was noted, associated with epithelioid granulomas. The etiological pathogens for the granulomas could not be detected even though investigation of special histochemical staining, immunohistochemical study and DNA analysis of Mycobacterium tuberculosis by polymerase chain reaction technique was performed. On electron microscopic examination, the area appearing as a storiform pattern consisted of fibroblasts showing much dilated rough endoplasmic reticulum and slender tappering cytoplasmic processes without cellular junctional complex. No organisms were identified in the granulomatous area of the lesion. From those findings the diagnosis as idiopathic granulomatous meningoencephalitis was made.

Microsatellite instability and hMSH2 gene mutation in a triple cancer (colon cancer, endometrial cancer, ovarian cancer) patient in hereditary non-polyposis colorectal cancer (HNPCC) kindred

A patient who had triple cancer (colon cancer, endometrial cancer, and ovarian cancer) in HNPCC kindred is reported. Her family history revealed the occurrence of colon cancer in her paternal aunt and in two cousins, fulfilling the minimum HNPCC criteria. Microsatellite instability analysis revealed replication error (RER)+ in all cancer lesions at 2 microsatellite loci (D1S191, BAT 40). SSCP analysis suggested germline mutation in exon 2 of the hMSH2 gene. This case showed the importance of complete family-history investigations to identify HNPCC patients. In the near future, definitive diagnosis of HNPCC will be possible on the basis of DNA studies.

Alterations of p73 preferentially occur in gastric adenocarcinomas with foveolar epithelial phenotype

To establish the possible involvement of p73, a newly discovered p53-related candidate as a tumor-suppressor gene in human stomach carcinogenesis, the allelic status, allele-specific expression and mutations of the gene were investigated using PCR-restriction fragment length polymorphism (PCR-RFLP) analysis, RT-PCR SSCP analysis and direct DNA sequencing in 95 gastric adenocarcinomas. Of these, 32 exhibited the heterozygous p73 allele for the StyI restriction site in exon 2. Among these, the cancer DNA of 12 revealed loss of heterozygosity (LOH) of p73. All of the cancers with p73 LOH exhibited phenotypes of foveolar epithelium of the stomach. RT-PCR SSCP analysis of p73 heterozygous cases demonstrated not only bi-allelic expression of the gene but also relatively reduced expression of the affected allele in 6 of 8 tumors with p73 LOH. No gene mutation was detected in the remaining allele of LOH-positive cancers. Our results suggest that alterations of p73, including LOH and abnormal expression, may play roles in the genesis of foveolar-type gastric adenocarcinomas, though this is not in line with a classical Knudson's "2-hit" model.

Alterations of p73 preferentially occur in gastric adenocarcinomas with foveolar epithelial phenotype

To establish the possible involvement of p73, a newly discovered p53-related candidate as a tumor-suppressor gene in human stomach carcinogenesis, the allelic status, allele-specific expression and mutations of the gene were investigated using PCR-restriction fragment length polymorphism (PCR-RFLP) analysis, RT-PCR SSCP analysis and direct DNA sequencing in 95 gastric adenocarcinomas. Of these, 32 exhibited the heterozygous p73 allele for the StyI restriction site in exon 2. Among these, the cancer DNA of 12 revealed loss of heterozygosity (LOH) of p73. All of the cancers with p73 LOH exhibited phenotypes of foveolar epithelium of the stomach. RT-PCR SSCP analysis of p73 heterozygous cases demonstrated not only bi-allelic expression of the gene but also relatively reduced expression of the affected allele in 6 of 8 tumors with p73 LOH. No gene mutation was detected in the remaining allele of LOH-positive cancers. Our results suggest that alterations of p73, including LOH and abnormal expression, may play roles in the genesis of foveolar-type gastric adenocarcinomas, though this is not in line with a classical Knudson's "2-hit" model.

Transfection of interleukin-8 increases angiogenesis and tumorigenesis of human gastric carcinoma cells in nude mice

The growth and spread of tumour cells depends on adequate vasculature. We have previously reported that the expression of interleukin-8 (IL-8) directly correlates with the vascularity of human gastric carcinomas. To provide evidence for a causal role of IL-8 in angiogenesis and tumorigenicity of human gastric cancer, we used the lipofectin method to stably transfect the human TMK-1 gastric carcinoma cells (low endogenous IL-8) with an IL-8 expression vector or control vector. Transfection with IL-8 did not affect the proliferation of cultured cells, yet the culture supernatants of the transfected (but not control) cells stimulated proliferation of human umbilical vein endothelial cells. The IL-8-transfected and control cells were injected into the gastric wall of nude mice. IL-8-transfected cells produced rapidly growing, highly vascular neoplasms as compared to control cells. These results provide direct evidence for the role of IL-8 in the angiogenesis and tumorigenicity of human gastric carcinomas.

Expression of p27Kip1, cyclin E and E2F-1 in primary and metastatic tumors of gastric carcinoma

The cell cycle is controlled by positive and negative regulators. Gene abnormalities and aberrant expressions of various cyclins/CDKs and CDK inhibitors may play a pivotal role in stomach carcinogenesis. To clarify the role of cyclin E, CDK inhibitor p27Kip1 and their target molecule, E2F-1 in tumor metastasis, we examined immunohistochemically the expression of cyclin E, p27Kip1 and E2F-1 in 23 gastric carcinomas and metastatic tumors of the lymph node. Most of gastric carcinomas with lymph node metastasis showed reduced p27Kip1 expression. p27Kip1 was negative in 39% (9/23) of primary tumors, while it was so in 52% (12/23) of lymph node metastases. By comparison of p27Kip1 expression in primary and metastatic tumors in individual cases, metastatic tumor cells in the lymph nodes were expressed at weaker levels than in those in primary tumors in 43% (10/23) of the cases. On the other hand, over 70% (17/23) and 50% (12/23) of the cases expressed cyclin E and E2F-1 at nearly the same levels in both primary tumor and lymph node metastasis, respectively. These results suggest that tumor cells with reduced p27Kip1 expression may selectively metastasize to lymph node or distant organs.

Molecular-pathological diagnosis of gastrointestinal tissues and its contribution to cancer histopathology

Multiple genetic and epigenetic alterations of cancer-related genes and molecules are involved in the course of the development and progression of gastrointestinal cancers. These include telomerase activation, genetic instability, and abnormalities of oncogenes, tumor suppressor genes, cell cycle regulators, cell adhesion molecules and DNA repair genes. By analyzing these alterations in pathology specimens, we can improve differential diagnosis of cancer, obtain information of grade of malignancy, and identify patients at high risk for developing multiple primary cancers. Since 1993, a system of molecular-pathological diagnosis was established, and has been performed as a routine service in collaboration with Hiroshima City Medical Association Clinical Laboratory. More than 10 000 cases of gastrointestinal biopsy and surgery have been analyzed, and additional information of differential diagnosis, biological malignancy and tumor multiplicity could be obtained. Molecular-pathological diagnosis may provide a new approach to cancer diagnosis and novel therapeutics for the 21st century. Furthermore, the analysis of the genetic and epigenetic abnormalities in clinical materials may clarify the molecular mechanism of carcinogenesis and comparative morphological changes. From the analyses of p27KIP1 and telomerase in gastrointestinal adenomas, we have learned that morphological abnormality of the nucleus is an indicator for cells with immortality and malignant potential that must participate in super-early diagnosis (detection of true precancerous lesions) of gastrointestinal cancer. Molecular-pathological diagnosis thus contributes to detailed understanding of cancer histopathology and improves the histopathological diagnosis.

Expression of cell-cycle-regulating transcription factor E2F-1 in colorectal carcinomas

The expression of E2F-1 in human colorectal carcinomas was examined immunohistochemically, and the correlation of E2F-1 expression with clinicopathological findings and with the expression of p27(Kip1) was analyzed to elucidate the role of E2F-1 in the development and progression of colorectal carcinomas. In nonneoplastic mucosa, a small number of epithelial cells in the proliferative zone were weakly positive for E2F-1. Weak expression of E2F-1 was detected in many adenoma cells. Most of the colorectal carcinomas expressed E2F-1 at various levels, and strong expression of E2F-1 was detected in 56% (49/88) of the cases. There was no correlation between the expression of E2F-1 and any clinicopathological parameters such as tumor stage, depth of tumor invasion and lymph node metastasis. Reduced expression of p27(Kip1) was confirmed to be significantly correlated with deep tumor invasion and presence of metastasis. No correlation was evident between overexpression of E2F-1 and reduced p27(Kip1) expression.