Frequent amplification of the c-met gene in scirrhous type stomach cancer

Cellular and molecular aspects of gastric cancer

Gastric cancer remains a global killer with a shifting burden from the developed to the developing world. The cancer develops along a multistage process that is defined by distinct histological and pathophysiological phases. Several genetic and epigenetic alterations mediate the transition from one stage to another and these include mutations in oncogenes, tumour suppressor genes and cell cycle and mismatch repair genes. The most significant advance in the fight against gastric caner came with the recognition of the role of Helicobacter pylori (H pylori) as the most important acquired aetiological agent for this cancer. Recent work has focussed on elucidating the complex host/microbial interactions that underlie the neoplastic process. There is now considerable insight into the pathogenesis of this cancer and the prospect of preventing and eradicating the disease has become a reality. Perhaps more importantly, the study of H pylori-induced gastric carcinogenesis offers a paradigm for understanding more complex human cancers. In this review, we examine the molecular and cellular events that underlie H pylori-induced gastric cancer.

MET Overexpression Turns Human Primary Osteoblasts into Osteosarcomas

The MET oncogene was causally involved in the pathogenesis of a rare tumor, i.e., the papillary renal cell carcinoma, in which activating mutations, either germline or somatic, were identified. MET activating mutations are rarely found in other human tumors, whereas at higher frequencies, MET is amplified and/or overexpressed in sporadic tumors of specific histotypes, including osteosarcoma. In this work, we provide experimental evidence that overexpression of the MET oncogene causes and sustains the full-blown transformation of osteoblasts. Overexpression of MET, obtained by lentiviral vector-mediated gene transfer, resulted in the conversion of primary human osteoblasts into osteosarcoma cells, displaying the transformed phenotype in vitro and the distinguishing features of human osteosarcomas in vivo. These included atypical nuclei, aberrant mitoses, production of alkaline phosphatase, secretion of osteoid extracellular matrix, and striking neovascularization. Although with a lower tumorigenicity, this phenotype was superimposable to that observed after transfer of the MET gene activated by mutation. Both transformation and tumorigenesis were fully abrogated when MET expression was quenched by short-hairpin RNA or when signaling was impaired by a dominant-negative MET receptor. These data show that MET overexpression is oncogenic and that it is essential for the maintenance of the cancer phenotype.

Amplification of MET may identify a subset of cancers with extreme sensitivity to the selective tyrosine kinase inhibitor PHA-665752

The success of molecular targeted therapy in cancer may depend on the selection of appropriate tumor types whose survival depends on the drug target, so-called "oncogene addiction." Preclinical approaches to defining drug-responsive subsets are needed if initial clinical trials are to be directed at the most susceptible patient population. Here, we show that gastric cancer cells with high-level stable chromosomal amplification of the growth factor receptor MET are extraordinarily susceptible to the selective inhibitor PHA-665752. Although MET activation has primarily been linked with tumor cell migration and invasiveness, the amplified wild-type MET in these cells is constitutively activated, and its continued signaling is required for cell survival. Treatment with PHA-665752 triggers massive apoptosis in 5 of 5 gastric cancer cell lines with MET amplification but in 0 of 12 without increased gene copy numbers (P = 0.00016). MET amplification may thus identify a subset of epithelial cancers that are uniquely sensitive to disruption of this pathway and define a patient group that is appropriate for clinical trials of targeted therapy using MET inhibitors.

Functional analysis of HGF/MET signaling and aberrant HGF-activator expression in diffuse large B-cell lymphoma

Inappropriate activation of MET, the receptor tyrosine kinase for hepatocyte growth factor (HGF), has been implicated in tumorigenesis. Although we have previously shown that HGF/MET signaling controls survival and proliferation of multiple myeloma (MM), its role in the pathogenesis of other B-cell malignancies has remained largely unexplored. Here, we have examined a panel of 110 B-cell malignancies for MET expression, which, apart from MM (48%), was found to be largely confined to diffuse large B-cell lymphomas (DLBCLs) (30%). No amplification of the MET gene was found; however, mutational analysis revealed 2 germ-line missense mutations: R1166Q in the tyrosine kinase domain in 1 patient, and R988C in the juxtamembrane domain in 4 patients. The R988C mutation has recently been shown to enhance tumorigenesis. In MET-positive DLBCL cells, HGF induces MEK-dependent activation of ERK and PI3K-dependent phosphorylation of PKB, GSK3, and FOXO3a. Furthermore, HGF induces PI3K-dependent α4β1 integrin-mediated adhesion to VCAM-1 and fibronectin. Within the tumor microenvironment of DLBCL, HGF is provided by macrophages, whereas DLBCL cells themselves produce the serine protease HGF activator (HGFA), which autocatalyzes HGF activation. Taken together, these data indicate that HGF/MET signaling, and secretion of HGFA by DLBCL cells, contributes to lymphomagenesis in DLBCL. (Blood. 2006;107:760-768)

Novel DNA amplification on chromosomes 2p25.3 and 7q11.23 in cholangiocarcinoma identified by arbitrarily primed polymerase chain reaction

PURPOSE

To detect and characterize amplified DNA sequences in cholangiocarcinoma (CCA).

PATIENTS AND METHODS

We extracted DNA from tumor and corresponding normal tissues of 30 patients with CCA and amplified with 30 random ten-mer arbitrary primers by the arbitrarily primed polymerase chain reaction (AP-PCR) technique.

RESULTS

Our results showed gains of genomic sequences at high frequency. Using the AX-11 arbitrary primer, we determined an amplified DNA fragment occurred frequently in the tumors analyzed. The DNA fragment was isolated and identified as two sequences mapped to chromosomes 2p25.3 and 7q11.23. Specific primers were designed employing these sequences and used for detecting amplification by real-time quantitative PCR. The amplification of the DNA sequences on chromosomes 2p25.3 and 7q11.23 was detected in 10 (33%) and 6 (20%) cases, respectively. Thirteen (43%) cases showed amplification on both or one of the chromosomes. In addition, amplification of the DNA on chromosome 2p25.3 was predominantly observed in poorly differentiated tumors.

CONCLUSIONS

Our findings suggest that the novel amplified DNA on chromosomal regions at 2p25.3 and 7q11.23 might be involved in the development and progression of CCA.

Chromosomal imbalances in wood dust-related adenocarcinomas of the inner nose and their associations with pathological parameters

Comparative genomic hybridization (CGH) was used to screen 42 wood dust-related sinonasal adenocarcinomas for chromosomal alterations. The tumour collection comprised 39 papillary-tubular cylinder cell adenocarcinomas (PTCCs; six cases G1, 23 G2, and ten G3), two alveolar goblet cell adenocarcinomas (AGCs), and one signet ring cell adenocarcinoma (SRC), according to the Kleinsasser and Schroeder classification. Copy number changes were detected in 41 tumours (97.6%). The one carcinoma without imbalances was a PTCC-G1. DNA gains were most frequently seen on chromosomes 12p (83%), 7q (74%), 8q (71%), and 20q (71%), 11q (61%), 22 (59%), and 1q (52%). Pronounced overrepresentations suggestive of high copy amplifications were detected on 8q (15 cases, 36%), 7q (six cases, 14%), 20q (five cases, 12%), 13q14 (three cases, 7%), 1q22, 5p, 12p and 20 (two cases, 5% each), and 2q24, 3q13, 3q22, 7p, 14q12, and 16q13 (one case, each 2%). Frequent chromosomal losses occurred at 5q (81%), 18q (76%), 4 (74%), 8p (61%), 9p (60%), 6q and 17p (52% each), and 3p, 13q, and 21 (50% each). There was a quantitative as well as a qualitative increase of alterations from PTCC-G1 to PTCC-G2 and finally PTCC-G3, confirming the usefulness of histopathological grading. While PTCC-G1 carried only a few alterations, namely gains on chromosomes 17 and 7 as well as losses of 4q and 13q, PTCC-G2 already carried many of the above-mentioned alterations, while PTCC-G3 showed significantly more gains of 7q, 8q, and 12p, and losses of 8p and 17p. Additionally, the latter subgroup was particularly prone to carry pronounced DNA gains. These data provide further evidence for a recurrent pattern of chromosomal imbalances in sinonasal adenocarcinomas and highlight distinct aberrations that are associated with tumour differentiation and progression.

The results of the expression array studies correlate and enhance the known genetic basis of gastric and colorectal cancer

Gastric and colorectal cancers belong to the most frequent cancer types in the world today. This fact emphasizes the importance of identification of useful diagnostic and prognostic markers, in the earliest stage of the disease. The examination of gene expression profile in gastric and colorectal cancer may develop the bases of early diagnosis and of individual therapeutic strategies. In the microarray examinations done so far for these types of cancers, the expression of hundreds and thousands of genes were studied, however, both the sample collection and the results showed wide variations. The diversity of expression array methods and data analysis makes the comparison of microarray results difficult. Beside the exposition of the practical aspects of the chip technology, our aims are the systematization of data that are currently available in the international scientific literature and the description of the results in a comprehensive way. Microarray results show that the gene expression pattern, detected in gastric and colon cancers, highly depends on the histological type and heterogeneity of the sample, array type, and softwares, used for data analysis. Recent experiments point out not just the changes of the alterations of tumor suppression, apoptosis, cell-cycle regulation, and signal transduction, but tumor cell metabolism and cell-microenvironment interactions also. Results show connection to and make more complete the already known molecular background of gastric and colorectal cancers. Based on the accumulation of recent and further data, such kind of multifunctional diagnostic microarrays that can be suited for completing the conventional histological diagnostics and subtypization will certainly become available in the near future.

Effects of COX-2 inhibitor on growth of human gastric cancer cells and its relation to hepatocyte growth factor

It is known that hepatocyte growth factor binding to its receptor regulates gastric cancer progression and metastasis. HGF was found to up-regulate the expression of cyclooxygenase-2 gene and increases prostaglandin (PG) synthesis in gastric mucosa cells. Overexpression of COX-2 and increased PG secretion have also been found to be involved in the regulation of growth and metastasis of gastric cancer. Results from this study showed that c-Met and COX-2 are expressed in 28 cases (93.3%) and 16 cases (53.3%) of 30 human gastric cancer tissues, respectively. Expressions of c-Met positively correlated with that of COX-2 (r=0.41; P=0.024). Using in vivo and in vitro models to further examine the interaction between c-MET and COX-2, we found that HGF stimulated the growth of SC-M1 cells in a dose-dependent manner. COX-2-specific inhibitor-NS398 inhibited the growth of human gastric cancer SC-M1 cells as well as HGF stimulated the growth of SC-M1 cells in a dose-dependent manner. HGF treatment of SC-M1 cells increased the secretion of PGE2 and this stimulation was blocked by NS398. In vivo SC-M1 tumor model showed that HGF stimulated the tumor growth and NS398 retarded the tumor growth. These results suggest that COX-2-specific inhibitors may play some role on the therapy of gastric cancer patients with high serum HGF level and overexpression of c-Met in tumor.

Scatter factor/hepatocyte growth factor in brain tumor growth and angiogenesis

The multifunctional growth factor scatter factor/hepatocyte growth factor (SF/HGF) and its receptor tyrosine kinase c-Met have emerged as key determinants of brain tumor growth and angiogenesis. SF/HGF and c-Met are expressed in brain tumors, the expression levels frequently correlating with tumor grade, tumor blood vessel density, and poor prognosis. Overexpression of SF/HGF and/or c-Met in brain tumor cells enhances their tumorigenicity, tumor growth, and tumor-associated angiogenesis. Conversely, inhibition of SF/HGF and c-Met in experimental tumor xenografts leads to inhibition of tumor growth and tumor angiogenesis. SF/HGF is expressed and secreted mainly by tumor cells and acts on c-Met receptors that are expressed in tumor cells and vascular endothelial cells. Activation of c-Met leads to induction of proliferation, migration, and invasion and to inhibition of apoptosis in tumor cells as well as in tumor vascular endothelial cells. Activation of tumor endothelial c-Met also induces extracellular matrix degradation, tubule formation, and angiogenesis in vivo. SF/HGF induces brain tumor angiogenesis directly through only partly known mechanisms and indirectly by regulating other angiogenic pathways such as VEGF. Different approaches to inhibiting SF/HGF and c-Met have been recently developed. These include receptor antagonism with SF/HGF fragments such as NK4, SF/HGF, and c-Met expression inhibition with U1snRNA/ribozymes; competitive ligand binding with soluble Met receptors; neutralizing antibodies to SF/HGF; and small molecular tyrosine kinase inhibitors. Use of these inhibitors in experimental tumor models leads to inhibition of tumor growth and angiogenesis. In this review, we summarize current knowledge of how the SF/HGF:c-Met pathway contributes to brain tumor malignancy with a focus on glioma angiogenesis.

Recurrent chromosomal rearrangements at bands 8q24 and 11q13 in gastric cancer as detected by multicolor spectral karyotyping

AIM: To identify chromosomal translocations specific to gastric cancer (GC), spectral karyotyping (SKY) analysis was performed on established cell lines and cancerous ascitic fluids.

METHODS: SKY analysis of 10 established cell lines and seven cancerous ascitic fluid samples identified recurrent chromosomal breakpoints and translocations in GC, several of which involved chromosomal loci of oncogenes or tumor suppressor genes.

RESULTS: A total of 630 chromosomal breaks were identified. Chromosome no.8 was the most frequently involved in rearrangements (65 breaks), followed by chromosomes no.11 (53), no. 1 (49), no. 7 (46), no. 13 (37), no. 3 (36), no. 17 (33), and no. 20 (29). Frequent breakpoints were detected in 8q24.1 (30 breaks), 11q13 (29), 13q14 (16), 20q11.2 (14), 7q32 (13), 17q11.2 (13), 18q21 (12), 17q23 (9), 18q11.2 (9). SKY analysis identified a total of 242 chromosomal rearrangements including 190 reciprocal and non-reciprocal translocations. The recurrent combinations of chromosomal bands involved in translocations were 8q24.1 and 13q14 (3 cases), 8q24.1 and 11q13 (3), 11q13 and 17q11.2 (2), and 18q11.2 and 20q11.2 (2). Our study validated the ability of SKY to characterize in detail the chromosomal rearrangements in solid tumors and derived cell lines. Moreover, fluorescence in situ hybridization helped to identify the insertions, translocations, and homogeneously staining regions of MYC and CCND1 gene loci.

CONCLUSION: The non-random co-localization of certain cytogenetic bands suggests the importance of chromosomal translocations in gastric carcinogenesis, by serving as landmarks for the cloning of GC causing genes.

Association of expression of receptor for advanced glycation end products and invasive activity of oral squamous cell carcinoma

OBJECTIVES

The receptor for advanced glycation end products (RAGE) is a newly recognized factor regulating cancer cell invasion and metastasis. Nevertheless, the involvement of RAGE in the development and progression of oral squamous cell carcinomas has not been elucidated. This study investigated the expression of RAGE in ten oral squamous cell carcinoma cell lines including primary and metastatic cell lines and its association with invasion and metastasis.

METHODS

Reverse transcriptase-polymerase chain reaction, antisense phosphorothioate (S)-oligodeoxynucleotide assay, preparation of antibody, immunohistochemical staining, immunoblot analysis, migration assay, in vitro invasion assay, and wound-healing assay were used.

RESULTS

RAGE protein expression of metastatic cancer cells treated with RAGE antisense S-oligodeoxynucleotide was significantly reduced compared to that of sense S-oligodeoxynucleotide-treated cells. The migration assay showed that invasive activity was significantly reduced in metastatic cancer cells treated with RAGE antisense S-oligodeoxynucleotide. Similarly, during invasion assays, numbers of invading cells were also reduced with the addition of RAGE antisense S-oligodeoxynucleotide-treated cells. A wound-healing assay showed that only a few RAGE antisense S-oligodeoxynucleotide-treated cancer cells migrated into the scraped area, whereas sense S-oligodeoxynucleotide-treated cells showed many budding nests in the scraped area of the metastatic cell lines. Immunohistochemically, oral squamous cell carcinoma cells in the tumour mesenchymal border were often immunopositive, whereas basal cells in the normal mucosa were scarcely positive.

CONCLUSIONS

These results suggest that RAGE expression appears to be closely associated with the invasiveness of oral squamous cell carcinoma and represents a promising candidate for assessing the future therapeutic potential in treating patients with oral carcinoma.

Expression of the c-Met in advanced epithelial ovarian cancer and its prognostic significance

The purpose of this study was to evaluate the prognostic significance of c-Met expression in advanced cases of epithelial ovarian carcinoma. Paraffin-embedded tissues from 41 stage IIIC primary ovarian adenocarcinoma were stained immunohistochemically for c-Met expression. The expression of c-Met was correlated with conventional clinicopathologic parameters and with overall survival of the patients. c-Met expression was found in 60.9% of cases. This clinicopathologic study showed that epithelial ovarian carcinomas with c-Met expression had higher histologic tumor grade and were more frequently associated with para-aortic lymph node metastasis (P < 0.05). In multivariate analysis, c-Met expression remained as a statistically significant predictor for survival with histologic grade. The patients with stage IIIC epithelial ovarian cancers whose tumors expressed c-Met were more likely to have high-grade tumors, have more para-aortic lymph node involvement, and have a significantly worse overall survival than those whose tumors were c-Met negative. In conclusion, c-Met expression might be a potential prognostic marker for patients with advanced-stage epithelial ovarian cancers.

Suppression of peritoneal implantation of gastric cancer cells by adenovirus vector-mediated NK4 expression

Peritoneal dissemination is the most common mode of metastasis in gastric cancer. We previously reported the importance of milky spots (MS), peritoneal lymphoid tissues, as selective sites of cancer implantation in peritoneal dissemination. In the present study, we first demonstrated that intraperitoneal injection of adenovirus vector encoding the GFP gene into tumor-free nude mice resulted in GFP expression at omental and mesenteric MS; MS macrophages were target cells for adenovirus infection. We confirmed that intraperitoneal injection of adenovirus vector encoding the NK4 gene (AdNK4) resulted in NK4 production localized to the peritoneal cavity, especially the omentum. Adenovirus vector-mediated MS-selective transgene expression was markedly impaired in tumor-bearing mice whose MS had already been replaced by infiltrating cancer cells. However, prior injection of AdNK4 successfully inhibited MS-selective cancer cell implantation, resulting in suppression of peritoneal dissemination and prolongation of survival. Adenovirus vector-mediated MS-selective delivery of a therapeutic gene may prevent peritoneal dissemination of gastric cancer.

c-Met as a target for human cancer and characterization of inhibitors for therapeutic intervention

Receptor tyrosine kinase (RTK) targeted agents such as trastuzumab, imatinib, bevacizumab, and gefitinib inhibitors have illustrated the utility of targeting this protein class for treatment of selected cancers. A unique member of the RTK family, c-Met, also represents an intriguing target for cancer therapy that is yet to be explored in a clinical setting. The proto-oncogene, c-Met, encodes the high-affinity receptor for hepatocyte growth factor (HGF) or scatter factor (SF). c-Met and HGF are each required for normal mammalian development and have been shown to be particularly important in cell migration, morphogenic differentiation, and organization of three-dimensional tubular structures (e.g. renal tubular cells, gland formation, etc.) as well as cell growth and angiogenesis. Both c-Met and HGF have been shown to be deregulated in and to correlate with poor prognosis in a number of major human cancers. New data describing the constitutive phosphorylation of c-Met in a number of human tumors is presented here along with a variety of mechanisms by which c-Met can become activated, including mutation and gene amplification. In support of the clinical data implicating c-Met activation in the pathogenesis of human cancers, introduction of c-Met and HGF (or mutant c-Met) into cells conferred the properties of motility, invasiveness, and tumorgenicity to the transformed cells. Conversely, the inhibition of c-Met with a variety of receptor antagonists inhibited the motility, invasiveness, and tumorgenicity of human tumor cell lines. Consistent with this observation, small-molecule inhibitors of c-Met were developed that antagonized c-Met/HGF-dependent phenotypes and tumor growth in mouse models. This review will address the potential for development of c-Met inhibitors for treatment of human cancers with particular emphasis on recent findings with small-molecule inhibitors.

Genetic alterations in 102 primary gastric cancers by comparative genomic hybridization: gain of 20q and loss of 18q are associated with tumor progression

Gastric cancer is one of the most common cancers. Molecular events in the carcinogenesis of gastric cancer remain, however, largely undefined. We investigated changes in DNA copy number in 102 gastric cancers by CGH. We found changes in DNA copy number in all cases, with frequent (> or =30% of patients) gains at 20q, 8q, 20p, 7q, 17q, 5p, and 13q. Frequent (> or =20%) losses were found at 19p, 18q, 5q, 21q, 4p, 4q, 15q, and 17p. The mean number of total alterations was significantly lower in grade 3 and scirrhous-type carcinomas (10.81 in grade 3 vs 13.98 in grade 1 and grade 2, 9.31 in scirrhous-type vs 13.18 in medullary- and intermediate-type). The mean number of losses and total alterations were higher in tumors at pT2, pT3 and pT4 (4.68 and 12.77 in pT2, pT3, and pT4 vs 2.55 and 9.22 in pT1). The mean number of losses was higher in carcinomas with lymph node metastasis (4.83). The mean number of gains and total alterations were higher in carcinomas with venous invasion (8.44 and 13.28). Several chromosomal alterations were linked in a statistically significant manner to specific clinicopathological parameters. Gain of 17q, 20p, and 20q and loss of 4p were associated with the pattern of the cancer-stroma relationship; loss of 18q was associated with pT category; gain of 5p was associated with pN category; loss of 4q and loss of 21q were associated with lymphatic invasion; gain of 7p and loss of 4q and 18q were associated with venous invasion; and loss of 18q was associated with pathological stage. These data suggest that gain of 20q and loss of 18q might play an important role in the development and progression of gastric cancer. Moreover, some genes on 20q and 18q might be target genes of gastric cancer.

Adenoviral-mediated gene transduction of the hepatocyte growth factor (HGF) antagonist, NK4, suppresses peritoneal metastases of gastric cancer in nude mice

The competitive inhibitory effects of NK4 (a specific hepatocyte growth factor (HGF)-antagonist) on the interaction between HGF and the c-Met/HGF receptor has been shown in HGF-mediated invasion of some distinct types of human cancer cells. Furthermore, NK4 has inhibitory effects on the angiogenic pathways driven by basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF), as well as by HGF. In this study, to evaluate the therapeutic efficacy of adenoviral-mediated NK4 gene treatment, we employed animal models of peritoneal metastasis using two gastric cancer cell lines, the strongly c-Met expressing MKN45 cell line and the weakly c-Met-expressing cell line, TMK1. In both models, the total number and weight of peritoneal tumours per mouse and ascites treated early with AxCANK4 (administered 3 times 2, 7 and 12 days after the tumour inoculation) were significantly reduced compared with those treated with phosphate-buffered solution (PBS) and AxCALacZ (P < 0.05). In Factor-VIII-related-antigen-stained sections from peritoneal metastatic tumours, the inhibition of intratumour vessels was observed in tissues from tumours of MKN45 and TMK1 treated with AxCANK4. We also compared the therapeutic effect of early AxCANK4 treatment with that of late treatment (at 7, 12 and 17 days). Peritoneal metastases and ascites treated late with AxCANK4 showed less of an improvement than those treated early with AxCANK4 in both models. In addition, the inhibitory effect of cisplatin (CDDP) on peritoneal metastasis was significantly enhanced by AxCANK4, suggesting that the combination of intraperitoneal (i.p.) chemotherapy with NK4 gene therapy might be effective, even in cases of advanced peritoneal metastasis from gastric cancer. To conclude, these results show clearly that NK4 gene therapy inhibits peritoneal metastases from gastric cancer, regardless of the level of c-Met/HGF receptor expression in the tumour cells, and especially in the early stages of peritoneal metastasis.

Hepatocyte growth factor and c-Met expression in rat and human liver fibrosis

BACKGROUND

Hepatocyte growth factor (HGF) is a potent mitogen for hepatocytes in vitro.

AIMS

Substitution of HGF was suggested for human liver disease on the basis of animal experiments. The cellular sources of HGF and its receptor, c-Met, in liver disease in vivo are not well defined.

METHODS

We characterised HGF and c-Met expression in normal and cirrhotic human livers and rat livers at various time points after CCl4 administration by in situ hybridisation and immunohistology. HGF transcripts were restricted to resting and activated stellate cells in rat and human liver.

RESULTS

In rat liver, HGF showed peak levels 6-12 h following acute intoxication, and remained increased after repeated CCl4 injury. HGF transcript levels were very low in normal human liver, but excessively raised in fibrosis/cirrhosis. In contrast, HGF immunoreactivity was found not only in perisinusoidal/periductular cells but also in cholangiocytes of proliferating ductules. c-Met RNA and protein was expressed in hepatocytes, cholangiocytes, and arteriolar endothelial cells.

CONCLUSIONS

The HGF-specific immunostaining of proliferating cholangioles in the absence of HGF RNA suggests c-Met-mediated uptake of HGF and paracrine stimulation of cholangiocellular proliferation. Mitogenic effects of HGF on hepatocytes may therefore be accompanied by undesired cholangiogenesis and angiogenesis limiting its therapeutic value in chronic liver disease.

DEGA/AMIGO-2, a leucine-rich repeat family member, differentially expressed in human gastric adenocarcinoma: effects on ploidy, chromosomal stability, cell adhesion/migration and tumorigenicity

We have discovered DEGA, a novel cDNA differentially expressed in human gastric adenocarcinomas. The DEGA gene product contains a signal peptide, five leucine-rich repeat motifs and a single IgG, and transmembrane domain, suggesting its residence on the plasma membrane. Transfection of 293 cells with a DEGA-GFP fusion construct confirmed its cell surface localization. Although the cytosolic portion of the DEGA gene product does not contain known protein domains, approximately one-fifth of these residues are either a serine or a threonine, suggesting that DEGA may play a role in signal transduction. BLAST searches revealed DEGA to be an exact match to AMIGO-2, a recently identified, but functionally uncharacterized protein related to AMIGO, a leucine-rich repeat containing cell adhesion molecule implicated in axon tract development. In this report, we show that DEGA/AMIGO-2 mRNA is differentially expressed in approximately 45% of tumor versus normal tissue from gastric adenocarcinoma patients. Stable expression of a DEGA/AMIGO-2 antisense construct in the gastric adenocarcinoma cell line, AGS, led to altered morphology, increased ploidy, chromosomal instability, decreased cell adhesion/migration, and a nearly complete abrogation of tumorigenicity in nude mice. These findings suggest a potential etiologic role for DEGA/AMIGO-2 in gastric adenocarcinoma.

Genetic lineage of poorly differentiated gastric carcinoma with a tubular component analysed by comparative genomic hybridization

Analysis of cell lineage is based on the use of genetic markers inherent to the lineage to be analysed. The breakpoints of unbalanced translocations, and the pattern of chromosomal loss/gain determined by comparative genomic hybridization (CGH), have been previously used to demonstrate lineages in diffuse-type gastric carcinoma. Signet ring cell carcinoma was shown to progress to poorly differentiated adenocarcinoma, and early diffuse-type gastric carcinoma to advanced diffuse-type gastric carcinoma. The present study focuses on poorly differentiated adenocarcinoma with a tubular component to clarify its derivation. CGH and array CGH were applied to DNA extracted from multiple portions of individual tumours and amplified by degenerate oligonucleotide-primed (DOP) PCR and the changes common to the samples in each tumour (stemline changes) were compared between the tumours with and those without a tubular component. Within individual tumours, the samples from the tubular component and those from the other components had common stemline changes and a very similar frequency pattern of chromosomal changes, indicating their common derivation. Frequent stemline changes were 8q+, 7p+, 3q+, 20q+, and 10p+, and these were different from those in the tumours without a tubular component. It was noticed that there were two subgroups in the tumours with a tubular component: one with 5p+, 6p+, 7p+, and 10p+, and the other without these changes. The latter had cytogenetic and clinicopathological features similar to those of the tumours without a tubular component. Analysis of the clonal evolution process by constructing dendrograms for each tumour gave results consistent with the notion that the latter subgroup may derive from signet ring cell carcinoma and the former from tubular adenocarcinoma.

The genomic damage estimated by arbitrarily primed PCR DNA fingerprinting is useful for the prognosis of gastric cancer

BACKGROUND & AIMS

Genomic instability and the accompanying alteration of cancer genes play a major role in tumorigenesis. We evaluated the prognostic significance in gastric cancer of the degree of accumulation of relative genomic damage, assessed by arbitrarily primed polymerase chain reaction DNA fingerprinting.

METHODS

Genomic damage was assessed by comparative analysis of paired normal and tumor tissue DNA fingerprints. The total number of alterations, scored as decreases and increases of band intensity with 2 arbitrary primers, were used as an estimation of the genomic damage fraction in 74 primary gastric cancers. Increases in DNA copy number were also analyzed by array comparative genomic hybridization in a subset of 30 cases.

RESULTS

The number of altered bands varied among the tumors from none or a few to more than one third of the approximately 40 fingerprint bands. The relative values of genomic damage were consistent with the quantitative chromosomal alterations observed by array comparative genomic hybridization. When the tumors were stratified into 2 groups-above or below the cutoff of 0.22 for average genomic damage fraction-genomic damage fraction was a valuable prognostic indicator regardless of microsatellite instability status. Multivariate Cox analysis showed that the genomic damage fraction was a prognostic indicator, as well as a stage indicator (P = 0.0189). Survival was significantly diminished in tumors with a genomic damage fraction >0.22 (P = 0.0009). Moreover, in the 46 curative cases, genomic damage fraction was the only independent factor for predicting survival (P = 0.0061).

CONCLUSIONS

Our results indicate that the degree of genomic damage estimated by arbitrarily primed polymerase chain reaction fingerprinting is a useful prognostic indicator for gastric cancer.

Up-regulation of cytoskeletal-associated protein 2 in primary human gastric adenocarcinomas

BACKGROUND AND METHOD

We performed differential-display polymerase chain reaction to find up-regulated sequences in primary human gastric cancers, and cloned one up-regulated sequence, which was expressed in all the gastric cancer cells that we examined. The cloned sequence was identified as cytoskeletal-associated protein 2 (CKAP2). We also cloned a shorter splice variant, CKAP2-s. The CKAP2 or CKAP2-s protein in HeLa cells was localized to microtubule organizing centers (MTOC) and microtubules. This co-localization pattern was disrupted by nocodazole, a microtubule-destabilizing agent.

RESULTS

These observations suggested that CKAP2 might be associated with microtubule networks. CKAP2 protein was detected in neither normal GI tract nor normal gastric mucosa. However, both CKAP2 and CKAP2-s mRNAs were up-regulated in 55% (23 out of 42 samples) of primary human gastric cancers by reverse transcriptase-polymerase chain reaction (RT-PCR). Moreover, CKAP2 proteins were detected in immunohistochemical staining in all the gastric cancer samples that we examined. CKAP2 protein-expressing cells were also found in gastric adenomas. The average number of CKAP2 protein-positive cells in adenocarcinomas was 48.8%, which was significantly higher than the number in tubular adenomas, 9.1%.

CONCLUSION

When these points were taken together, we concluded that CKAP2 is up-regulated in primary human gastric adenocarcinomas at high frequency and might be useful for diagnosing and discriminating adenocarcinomas from tubular adenomas of the stomach.

Nonrandom chromosomal numerical abnormality predicting prognosis of gastric cancer: a retrospective study of 51 cases using pathology archives

Chromosomal or centromerical numerical abnormality (CNA) is a well-known characteristic of human cancer, but the extensive and specific documentation of CNA in gastric cancer is still sparse, partly because of difficulty in obtaining cytogenetic information. Taking advantage of a recently developed fluorescence in situ hybridization protocol for formalin-fixed paraffin-embedded tissues, we investigated CNA of 51 gastric cancer cases with a panel of 18 chromosome-specific alpha-satellite probes (for chromosomes 1-4, 6-12, 15-18, 20, X and Y) and region specific probes (c-myc and p53) to enumerate respective chromosome numbers in interphase nuclei. The involved chromosomes exhibiting CNA were nonrandom in gastric cancer. Aberrations of chromosomes 1, 8, 17, 20, and X were frequent regardless of histologic types, whereas aberrations chromosomes 10, 15, and 18 occurred less often (p < 0.001). From a histopathologic standpoint, the mucocellular type had stable CNA in comparison with the tubular type (mucocellular type vs tubular type carcinoma: 21.0 +/- 10.63% vs 62.8 +/- 12.79%, p < 0.001). Interestingly, there was less extensive CNA in women (men vs women: 54.3 +/- 9.49% versus 24.9 +/- 12.23%, p < 0.001). A dramatic difference in the outcome was detected according to the involvement of chromosomes 3, 10, 11, 12, 17, and Y; that is, the cases with CNA of these chromosomes had worse prognosis.

Tyrosine-kinase expression profiles in human gastric cancer cell lines and their modulations with retinoic acids

Many protein tyrosine kinases are key regulators involved in cellular growth, differentiation, development, apoptosis and signal transduction pathways. Obtaining a comprehensive tyrosine-kinase expression profile in tumour cells is essential to learning more about their oncogenic potentials and responses to various chemotherapeutic reagents - such as retinoic acid, which has been shown to suppress the growth of gastric cancer cells and modulate gene expression. Expression of tyrosine kinases in retionic acid-treated cancer cells was investigated by reverse trancriptase-polymerase chain reaction (RT-PCR) and a novel restriction analysis of gene expression (RAGE) display technique. We first established comprehensive tyrosine-kinase profiles in different human gastric cancer cell lines. In cells treated with 9-cis-retinoic acid or all-trans-retinoic acid, we found that two PTKs (Eph and Hek5) appeared to be upregulated. In the present study, we demonstrate an efficient and simple RAGE approach for examining tyrosine kinases' expression in tumour cells and their alterations following drug treatments.

Overexpression of hepatocyte growth factor receptor in renal carcinoma cells indirectly stimulates tumor growth in vivo

We examined the role of increased expression of HGFR kinase in in vivo growth of renal carcinoma. Human renal carcinoma cell line, ACHN cells, was transfected with plasmid encoding wild-type HGFR gene to generate cell lines with increased HGFR protein. ACHN cells with elevated HGFR expression, denoted clones 8 and 10, respectively, showed higher basal kinase activities of HGFR and PI3-kinase than those of empty-vector (mock)-transfected cells. Clone 8 and 10 cells grew similar to mock cells in culture. In mice, tumors of these clones grew more rapidly than those of mock cells. Microvessel density of clone 8 or 10 tumors was higher than that of mock tumors. Clone 8 and 10 cells secreted vascular endothelial growth factor-A (VEGF-A) more than mock cells and the secretion was PI3-kinase inhibitor, LY294002-sensitive. Anti-VEGF-A neutralizing antibody significantly inhibited tumor growth of clones 8 and 10 in mice. These results indicate for the first time that overexpression of HGFR tyrosine kinase in renal carcinoma cells participates in rapid tumor growth in vivo.

c-Met expression in gastric cancer with liver metastasis

Liver metastasis is one of the poor prognostic factors for gastric cancer. Hepatocyte growth factor (HGF) and its receptor, c-Met, have been reported to be related to the proliferation of carcinoma cells. We examined c-Met and HGF expression in stage IV gastric cancers (n = 121) and compared the results in groups with liver metastasis (n = 47, LM group) and without liver metastasis (n = 74, no-LM group). The survival rate for the LM group was significantly poorer than for the no-LM group (p < 0.01). We found a high frequency of c-Met expression in the LM group compared with the no-LM group at protein level detected by immunohistochemistry (p = 0.0005) and at mRNA level detected by semiquantitative reverse transcriptase-polymerase chain reaction (p = 0.0386) in primary gastric tumors. Furthermore, we evaluated HGF expression in both carcinoma cells and stromal cells in gastric cancers. There was no significant difference in the HGF expression between the LM and no-LM groups. The labeling index of proliferating cell nuclear antigen for the carcinomas in the LM group was higher than that in the no-LM group (47.1 +/- 24.5 vs. 26.2 +/- 24.5%, p < 0.0001). Thus, the high frequency of c-Met overexpression in carcinoma cells may be involved in the mechanism of liver metastasis in gastric cancers. Moreover, the evaluation of c-Met expression might be a useful indicator of liver metastasis in patients with gastric cancer.

Genome-wide screening of laser capture microdissected gastric signet-ring cell carcinomas

Gastric signet-ring cell carcinoma comprises a distinct category of gastric cancers and has been reported to have poor prognosis. In an attempt to define genetic changes involved in the pathogenesis of this lesion in an in vivo state, we isolated signet-ring cell carcinoma cells from freshly fixed smears of tumor tissues of 7 primary gastric signet-ring cell carcinomas by laser capture microdissection and applied comparative genomic hybridization (CGH) to screen for DNA sequence copy number changes. Frequent chromosomal gains were detected on 2q, 5p, 7q, 14q and 20q, each in 6/7 cases, on 9q, 12q, 17q, and 19q, each in 5/7 cases, and on 18p in 4/7 cases. Frequent losses were observed on 6p and 17p, each in 5/7 cases, on 6q, and 21p, each in 4/7 cases, and on 3p, 8p and 8q, each in 3/7 cases. Losses on 6p have rarely been observed in conventional types of gastric carcinomas reported in the literature. These data provide the first evidence for the occurrence of specific genomic aberrations in gastric signet-ring cell carcinomas. Our observation of frequent losses on 6p chromosomal arm may provide novel abnormalities of potential significance in gastric signet-ring cell carcinomas, suggesting the involvement of genes residing in this region in the genesis of the disease.

Molecular and biologic basis of upper gastrointestinal malignancy. Gastric carcinoma

Gastric cancer is one of the world's most common cancers and is a leading cause of cancer death worldwide. Neoplasia of the stomach is mainly composed of adenocarcinomas, which for more than 95% of cases. Although mesenchymal tumors (i.e., stromal tumors, leiomyomas and leiomyosarcomas, and schwannomas), primary lymphomas, and carcinoid tumors can also arise in the stomach, malignant tumors of these types occur much less often.

Hepatocyte growth factor promotes hepatocarcinogenesis through c-Met autocrine activation and enhanced angiogenesis in transgenic mice treated with diethylnitrosamine

Hepatocyte growth factor (HGF) is a mitogen for hepatocytes, but it is not clear whether HGF stimulates or inhibits hepatocarcinogenesis. We previously reported that HGF transgenic mice under the metallothionein gene promoter developed benign and malignant liver tumors spontaneously after 17 months of age. To elucidate the role of HGF in hepatocarcinogenesis, diethylnitrosamine (DEN) was administered to HGF transgenic mice. HGF overexpression accelerated DEN-induced hepatocarcinogenesis, often accompanied by abnormal blood vessel formation. In this study, 59% of transgenic males (versus 20% of wild-type males) and 39% of transgenic females (versus 2% of wild-type females) developed either benign or malignant liver tumors by 48 weeks (P<0.005, P<0.001, respectively). Moreover, 33% of males and 23% of female transgenic mice developed hepatocellular carcinoma (HCC), while none of the wild-type mice developed HCC (P<0.001, P<0.005, respectively). Enhanced kinase activity of the HGF receptor, Met, was detected in most of these tumors. Expression of vascular endothelial growth factor (VEGF) was up-regulated in parallel with HGF transgene expression. Taken together, our results suggest that HGF promotes hepatocarcinogenesis through the autocrine activation of the HGF-Met signaling pathway in association with stimulation of angiogenesis by HGF itself and/or indirectly through VEGF.

Role of the hepatocyte growth factor receptor, c-Met, in oncogenesis and potential for therapeutic inhibition

Receptor tyrosine kinases have become important therapeutic targets for anti-neoplastic molecularly targeted therapies. c-Met is a receptor tyrosine kinase shown to be over-expressed and mutated in a variety of malignancies. Stimulation of c-Met via its ligand hepatocyte growth factor also known as scatter factor (HGF/SF), leads to a plethora of biological and biochemical effects in the cell. There has been considerable knowledge gained on the role of c-Met-HGF/SF axis in normal and malignant cells. This review summarizes the structure of c-Met and HGF/SF and their family members. Since there are known mutations of c-Met in solid tumors, particularly in papillary renal cell carcinoma, we have summarized the various mutations and over-expression of c-Met known thus far. Stimulation of c-Met can lead to scattering, angiogenesis, proliferation, enhanced cell motility, invasion, and eventual metastasis. The biological functions altered by c-Met are quite unique and described in detail. Along with biological functions, various signal transduction pathways, including the cytoskeleton are altered with the activation of c-Met-HGF/SF loop. We have recently shown the phosphorylation of focal adhesion proteins, such as paxillin and p125FAK in response to c-Met stimulation in lung cancer cells, and this is detailed here. Finally, c-Met when mutated or over-expressed in malignant cells serves as an important therapeutic target and the most recent data in terms of inhibition of c-Met and downstream signal transduction pathways is summarized.

Expression of receptors for advanced glycation end-products (RAGE) is closely associated with the invasive and metastatic activity of gastric cancer

The receptor for advanced glycation end-products (RAGE) is a newly recognized factor regulating cancer cell invasion and metastasis. This study investigated the expression of RAGE in gastric carcinomas and its association with invasion and metastasis. Of eight gastric cancer cell lines examined, seven constitutively expressed RAGE messenger ribonucleic acid (mRNA), MKN45 being the exception. RAGE protein expression of MKN28 cells treated with RAGE antisense S-oligodeoxynucleotide was nine times less than that of sense S-oligodeoxynucleotide-treated cells. Growth of cells under RAGE antisense S-oligodeoxynucleotide treatment was not different from that seen under sense S-oligodeoxynucleotide treatment in MKN28 (a cell line producing high levels of RAGE) and MKN45 (a non-RAGE-expressing cell line). RAGE antisense S-oligodeoxynucleotide treatment suppressed the invasive activity of RAGE-positive MKN28 cells, as estimated by in vitro invasion assay. The number of MKN28 cells invading the type IV collagen-coated membrane under RAGE antisense S-oligodeoxynucleotide treatment was significantly lower than under RAGE sense S-oligodeoxynucleotide treatment (p<0.0001). In contrast, antisense and sense S-oligodeoxynucleotide-treated RAGE-negative MKN45 cells showed no difference. A wound-healing assay showed that no RAGE antisense S-oligodeoxynucleotide-treated MKN28 cells migrated into the scraped area, whereas sense S-oligodeoxynucleotide-treated cells showed many budding nests in the scraped area. Immunohistochemistry of gastric carcinoma tissue showed that 62 (65%) of the 96 cases examined were RAGE-positive and that poorly differentiated adenocarcinomas preferentially expressed RAGE protein (38/42, 90%) (p<0.0001). Strong RAGE immunoreactivity was also correlated with depth of invasion and lymph node metastasis (p<0.0001). RAGE-positive cancer cells tended to be distributed at the invasive front of primary tumours and were detected in all metastatic foci in lymph nodes. In contrast, a major RAGE ligand, amphoterin, was expressed in 82 (85%) of the 96 cases, regardless of histological type and disease progression. RAGE expression appears to be closely associated with invasion and metastasis in gastric cancer.

High-density allelotype of the commonly studied gastric cancer cell lines

Gastric cancer is one of the leading causes of death from cancer throughout the world, and studies to elucidate the genetic defects found in this type of cancer are growing in number. Increasingly sophisticated techniques and the sequencing of the human genome have had an impact on the scope of such studies. While the use of tumor specimens remains popular, more emphasis is being placed on cell lines as model systems where specific data can be directly combined with results from other studies. This article describes a genetic survey of the most widely used gastric adenocarcinoma cell lines. The allelotype at 351 polymorphic loci in 14 cell lines was obtained, and the results from the 4,900 polymerase chain reactions are displayed. In addition to confirming loss of heterozygosity on chromosome arms 6p, 7q, 17p, and 18, additional deletions on arm 5p and the pericentromeric regions of chromosomes 1 and 10 were detected. Areas that might contain homozygous deletions or amplifications also were mapped. The rate of microsatellite instability was quantified and shown to vary greatly among the different cell lines. Most important, this study serves as a genetic scaffold for the integration of past and future studies on the nature of the genetic defects in gastric cancer.

Absence of tpr-met and expression of c-met in human gastric mucosa and carcinoma

The c-met proto-oncogene, encoding the hepatocyte growth factor receptor, can be activated by various mechanisms. These include, among others, gene amplification with concomitant overexpression and the tpr-met oncogenic rearrangement. In the case of gastric cancer, contradictory results on the presence of the tpr-met oncogenic rearrangement have been published. The current study aimed therefore to assess the prevalence of tpr-met expression in Caucasian gastric adenocarcinomas, to evaluate the importance of this oncogene in their carcinogenesis. In addition, the level of c-met expression was determined, to evaluate the role of this alternative mode of activation of the proto-oncogene. A series of Caucasian gastric adenocarcinomas (n=43) and normal gastric mucosal samples (n=14) was analysed for tpr-met and c-met expression. Expression of tpr-met mRNA in the samples was performed by two reverse transcriptase polymerase chain reaction (RT-PCR) assays, with excellent correlation. The specificity of both methods was confirmed by direct sequencing of the PCR products of the MNNG-HOS cell line, which is known to contain the rearrangement. The level of c-met expression was assessed using semi-quantitative RT-PCR assays and immunohistochemistry (IHC). None of the normal gastric mucosal or gastric adenocarcinoma samples expressed tpr-met mRNA, as determined by both RT-PCR assays. Seventy per cent of the adenocarcinomas showed overexpression of c-met, according to elevated c-met mRNA levels, compared with the expression level of normal gastric mucosa. A significant correlation was found between the level of c-met mRNA and protein expression. In conclusion, these results strongly suggest that tpr-met activation does not play a role in Caucasian gastric carcinogenesis, while overexpression of the c-met gene occurs in the majority of Caucasian gastric adenocarcinomas.

DNA sequence copy number aberrations associated with histological subtypes and DNA ploidy in gastric carcinoma

We have analyzed DNA sequence copy number aberrations (DSCNAs) and DNA ploidy by using comparative genomic hybridization and laser scanning cytometer in gastric carcinomas (GCs) to elucidate the genomic aberrations in relation to clinicopathological parameters. Thirty-two out of 33 cases showed one or more DSCNAs with a mean number of 11.7 per tumor. High-level gains were detected at 2p, 3q, 6p, 7p, 7q, 8q, 12p, 13q, 19q, and 20q. Frequency of gross genomic abnormalities and chromosome regions that have genomic aberrations were similar in both intestinal- and diffuse-type GCs, except aberrations at 8p, 9p, 12q, and 20q. The overall number of DSCNAs was significantly greater in DNA aneuploid tumors than that in DNA diploid tumors. We detected genomic aberrations characterized by histological subtype, tumor location, and DNA ploidy status: gain of 20q and losses of 8p and 9p in intestinal-type GCs, gains of 8p and 12q in diffuse-type GCs, gain of 20q in the lower third GCs, and loss of 5q, 9p, 10q, 16q, and 18q in DNA aneuploid GCs. Furthermore, 5q loss is associated with DNA aneuploidy (P = 0.0001) or the total number of losses (P = 0.001), gain + losses (P = 0.004), and high-level gains (P = 0.001) in GCs. Among these loci, chromosome 8p was unique. Gain of 8p was more common in diffuse-type GC, whereas loss of 8p was more frequently detected in intestinal-type GC. In conclusion, we describe chromosomal regions of 5q, 8p, and 20q, which are of interest for further investigation of GCs.

Expression of p53 protein as a prognostic indicator of reduced survival time in diffuse-type gastric carcinoma

To determine whether p53 expression is different in intestinal and diffuse types of gastric carcinoma, we investigated p53 immunohistochemical expression in 178 primary gastric carcinomas. Overexpression of p53 was observed in 50 out of 100 intestinal-type tumors (50.0%) and in 27 out of 78 diffuse-type tumors (34.6%). A significant difference was found in the timing of p53 overexpression between the two types of carcinomas. Overexpression of p53 occurred often in the early stage of intestinal-type tumors, and there was no significant difference in expression between early and advanced cancers. In contrast, p53 overexpression did not occur often in the early stage of diffuse-type tumors, but it increased progressively as the tumor advanced. Analysis of patient survival revealed that p53 overexpression correlates significantly with a poor prognosis in diffuse-type gastric carcinoma (P = 0.003) but not in intestinal-type. Multivariate analysis showed that only pathological stage was an independent prognostic indicator. Our results suggest that p53 overexpression plays a different role in tumor carcinogenesis and progression of these two types of gastric cancers.

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 the c-met protooncogene in human gastric carcinoma--correlation to clinical features

Overexpression of hepatocyte growth factor receptor (c-met) has been detected in many human tumors. To investigate the possible involvement of c-met in human gastric carcinogenesis, we examined c-met expression in 45 patients with gastric carcinoma using Northern blot analysis, reverse transcription-polymerase chain reaction (RT-PCR), and immunohistochemical staining. The c-met mRNA expression was increased twofold and sevenfold in gastric carcinoma tissues compared to the adjacent normal tissues by Northern blot analysis and RT-PCR, respectively. In the immunohistochemical study, c-met protein was detected in 32 of 45 (71.1%) patients, with marked overexpression in gastric carcinoma compared with matched normal gastric tissues. The c-met-positive immunoreactivities were more frequently encountered in serosa-exposed and serosa-infiltrating gastric cancer (p = 0.003). In addition, tumor stage was another statistically significant parameter that was observed between the two groups (p = 0.02). Multivariate analyses revealed that the tumor stage (p = 0.014) and c-met overexpression (p = 0.031) were independently correlated with survival. These data suggest that overexpression of c-met may play a part in gastric carcinogenesis and may represent a prognostic factor for gastric cancer.

CD44 is a potential target of amplification within the 11p13 amplicon detected in gastric cancer cell lines

Classical cytogenetic approaches have revealed many of the chromosomal aberrations that may occur in gastric cancers (GC), although few alterations of specific genes have been identified so far. Genes that affect progression of this disease need to be identified if clinicians are to achieve optimal management of patients with GC. As the first step toward the cloning of gene(s) that may be involved in gastric carcinogenesis, we examined 25 GC cell lines for aberrations in DNA copy number to detect chromosomal gains and losses, as well as gene amplifications, by comparative genomic hybridization (CGH). Our CGH study revealed high-level amplifications in chromosomal regions that had been well defined in GC but also in sites that had not, including 3p24, 5p15, 11p11.2-14, 13q34, 15q26, Xp24, and Xq26-28. The minimal common region at 11p13, within the 11p11.2-14 amplicon, harbors the CD44 gene. Northern and Western blot analyses showed that an alternatively spliced form of CD44, with variant exons 8-10 (CD44E), was overexpressed in all cell lines bearing the 11p13 amplicon. However, cell adhesion activity was no greater in these lines than in cell lines without amplifications at the CD44 locus, suggesting that the major property of upregulated CD44 in these cases might be to transduce signals critically associated with growth and proliferation of the tumor cells.

Tyrosine kinases and gastric cancer

Carcinoma of the stomach is one of the most prevalent cancer types in the world today. Two major forms of gastric cancer are distinguished according to their morphological and clinicopathological classifications (well differentiated/intestinal type and poorly differentiated/diffuse type), characteristics that could also be attributed to the altered expression of different types of oncogenes or tumor suppressor genes. Significant differences exist for gastric cancer incidence comparing people of different ethnic origins, implicating various genetic and epigenetic factors for gastric oncogenesis. There are only a limited number of molecular markers available for gastric cancer detection and prognostic evaluation, among which are tyrosine kinases. There is convincing evidence that tyrosine kinases are involved in oncogenesis and disease progression for many human cancers. Amplifications of certain tyrosine kinases (c-met, k-sam and erbB2/neu) have been associated with human gastric cancer progression. Alternatively spliced transcripts and enhanced protein-expression levels for some of these tyrosine kinases are correlated with clinical outcomes for gastric cancer patients. With advent of high throughput techniques, it is now possible to detect nearly all expressed tyrosine kinases in a single screen. This increases the chance to identify additional tyrosine kinases as predictive markers for gastric cancers. In this article, we will first review the literature data concerning certain tyrosine kinases implicated in gastric carcinogenesis and then summarize more recent work which provide comprehensive tyrosine kinase profiles for gastric cancer specimens and cell lines. Two new gastric cancer molecular markers (tie-1 and mkk4) have been identified through the use of these profiles and demonstrated effective as clinical prognostic indicators.

Protein-tyrosine kinase and protein-serine/threonine kinase expression in human gastric cancer cell lines

Protein kinases play key roles in cellular functions. They are involved in many cellular functions including; signal transduction, cell cycle regulation, cell division, and cell differentiation. Alterations of protein kinase by gene amplification, mutation or viral factors often induce tumor formation and tumor progression toward malignancy. The identification and cloning of kinase genes can provide a better understanding of the mechanisms of tumorigenesis as well as diagnostic tools for tumor staging. In this study, we have used degenerated polymerase-chain-reaction primers according to the consensus catalytic domain motifs to amplify protein kinase genes (protein-tyrosine kinase, PTK, and protein-serine/threonine kinase, PSK) from human stomach cancer cells. Following amplification, the protein kinase molecules expressed in the gastric cancer cells were cloned into plasmid vectors for cloning and sequencing. Sequence analysis of polymerase-chain-reaction products resulted in the identification of 25 protein kinases, including two novel ones. Expression of several relevant PTK/PSK genes in gastric cancer cells and tissues was further substantiated by RT-PCR using gene-specific primers. The identification of protein kinases expressed or activated in the gastric cancer cells provide the framework to understand the oncogenic process of stomach cancer.

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.

The hepatocyte growth factor/Met pathway in development, tumorigenesis, and B-cell differentiation

This article summarizes the structure, signal transduction and physiologic functions of the HGF/Met pathway, as well as its role in tumor growth, invasion, and metastasis. Moreover, it highlights recent studies indicating a role for the HGF/Met pathway in antigen-specific B-cell development and B-cell neoplasia.

The use of molecular biology in diagnosis and prognosis of gastric cancer

The investigation of molecular and genetic changes in gastric cancer has brought new insights into the pathogenesis of the disease. Knowledge of the genetic abnormalities and altered molecules could be used for differential diagnosis in case of an unknown primary tumor, allows their evaluation as prognostic factors, and could open novel avenues for more specific clinical interventions. Clinically relevant molecules whose expression or structure is altered include the plasminogen activator and its inhibitor plasminogen activator inhibitor type 1, the cell cycle regulator cyclin E, epidermal growth factor, the apoptosis inhibitor bcl-2, the cell adhesion molecule E-cadherin, and the multifunctional protein beta-Catenin. In addition, genetic instability is commonly seen. Gene amplification and protein overexpression of the growth factor receptors c-erbB2 and K-sam may be prognostic factors for intestinal- and diffuse-type gastric cancer, respectively. There has long been evidence for a genetic predisposition to gastric cancer by epidemiological studies and case reports. Very recently, germ line mutations of E-cadherin have been identified that are responsible for a dominantly inherited from of diffuse-type gastric cancer and could be used to identify individuals that are at high risk. The clinical implications of the recent findings for diagnosis, prognosis, therapy, and risk assessment are discussed.

Frequency of TPR-MET rearrangement in patients with gastric carcinoma and in first-degree relatives

BACKGROUND

The activation of the c-met protooncogene through a rearrangement has been detected previously in gastric carcinoma tissue and precancerous lesions. In the current study the authors analyzed the rearrangement of TPR-MET in gastric carcinoma patients and in first-degree relatives to evaluate the potential role and timepoint of this genetic alteration in the process of gastric carcinogenesis and its potential value in identifying those individuals with an increased risk of developing gastric carcinoma.

METHODS

The presence of TPR-MET mRNA was determined in gastric tissue from 19 patients with gastric carcinoma and in the gastric mucosa of 18 first-degree relatives without gastric carcinoma and in the gastric mucosa of 18 first-degree relatives without gastric carcinoma using a nested reverse transcriptase-polymerase chain reaction (RT-PCR) and Southern blot analysis. A 205-base pair (bp) cDNA fragment and a 70-bp cDNA fragment spanning the breakpoint were amplified by nested PCR. Amplification products were hybridized with an oligonucleotide labeled at the 3'-end with DIG-11-dUTP spanning the breakpoint using Southern blot analysis. The MNNG-HOS cell line served as a positive control.

RESULTS

TPR-MET mRNA was detected in nine gastric carcinoma patients (47%). Among these patients, TPR-MET mRNA was present in the both tumor and tumor free tissues in 5 patients (26%), in the tumor tissue only in 2 patients (11%), and in the tumor free gastric mucosa only in 2 patients (11%). It is interesting to note that TPR-MET rearrangement also was detected in the gastric corpus mucosa of 1 first-degree relative (6%), but in none of the control subjects.

CONCLUSIONS

The data from the current study indicate that TPR-MET activation may be an early event in gastric carcinogenesis and may be useful for the identification of individuals with an increased risk of developing gastric carcinoma.

Sequential numerical changes of chromosomes 7 and 18 in diffuse-type stomach cancer cell lines: combined comparative genomic hybridization, fluorescence in situ hybridization, and ploidy analyses

Sequential changes of chromosomal copy number were analyzed retrospectively in five diffuse-type gastric cancer cell lines by comparative genomic hybridization (CGH), DNA cytometry, and fluorescence in situ hybridization (FISH) with centromeric and painting probes. By CGH, we found loss of 18q21 in all of the cell lines and gains of 7p11-q31, 20q, and 22 in four of the five cell lines. Actual copy numbers of chromosomes 7 and 18 were determined by FISH: disomy 18 with (partial) loss of 18q in the two DNA-diploid cell lines (AGS and MKN-45), trisomy 7 in MKN-45, disomy 18 and tetrasomy 7 with one-copy loss of 7p and one-copy gain of 7q tip in DNA-triploid HSC-39/40A, and trisomy 18 and hexasomy 7 with one-copy loss of 7q in DNA-tetraploid KATO-III. Because the DNA aneuploidy is thought to result through tetraploidization, and the duplicated chromosomal changes in DNA aneuploid tumors seem to precede tetraploidization, the duplicated gain of chromosome 7 and one-copy loss of 7q in KATO-III were inferred to have occurred before and after tetraploidization, respectively. Similarly, HSC-39/40A were inferred to be preceded by the DNA-diploid stage with disomy 7 and monosomy 18. As the loss of 18q21 and the gain of 7p11-q31 were inferred to have occurred already in the DNA diploid stage in at least four and two of the cell lines, respectively, the 18q21 loss may be more important than the 7q gain as an earlier event in the genesis of diffuse-type stomach cancer. The combined CGH, FISH, and ploidy analyses thus give us a clue to extract important earlier events from the chromosomal changes that were screened by CGH alone.

c-met tyrosine kinase receptor expression is associated with abnormal beta-catenin expression and favourable prognostic factors in invasive breast carcinoma

AIMS

Receptor-type tyrosine kinases are important in cell signal transduction and proliferation. Abnormal expression of tyrosine kinases often leads to malignant transformation. c-met is a tyrosine kinase receptor and its ligand is hepatocyte growth factor (HGF). In this study, we have evaluated c-met expression in 69 invasive breast carcinomas and statistically analysed this expression with known clinicopathological prognostic parameters and patients' survival. We also studied for the first time c-met expression in association with E-cadherin and beta-catenin expression.

METHODS AND RESULTS

Immunohistochemistry (ABC-HRP method) was peformed for the detection of c-met, E-cadherin and beta-catenin. c-met immunoreactivity was observed in 58% of cases and was associated with the lobular type of breast carcinomas (P = 0.012), low histological grade ductal carcinomas (P = 0.05), favourable prognostic and predictive factors such as oestrogen and progesterone receptor immunohistochemical expression and negative c-erbB-2 expression (P = 0.05, P = 0.014 and P = 0.03, respectively). c-met immunoreactivity did not correlate with lymph node status, tumour size and stage of the disease. Cox's proportional hazard regression model demonstrated that tumours with positive c-met immunoreactivity correlated significantly with favourable patients' survival (P = 0.028). When c-met staining was compared with E-cadherin and beta-catenin expression, a statistical significant correlation was established between c-met immunoreactivity and abnormal beta-catenin expression (P = 0.025) suggesting possible involvement of c-met in the downregulation of the E-cadherin-catenin complex, possibly through tyrosine phosphorylation of beta-catenin.

CONCLUSION

c-met immunohistochemical expression seems to be associated with abnormal beta-catenin expression, good prognostic and predictive factors and favourable outcome in breast cancer patients.

Genetic alterations of gastric cancer: comparative genomic hybridization and fluorescence In situ hybridization studies

Genetic changes leading to the development of gastric cancers are still in dispute. In the following study, we used comparative genomic hybridization (CGH) to screen for DNA copy number changes along all chromosomes in 37 gastric carcinomas, and fluorescence in situ hybridization (FISH) with the C-MYC and TP53 probes in 14 cases for comparison. The aim of this study was to identify those chromosome regions that contain genes important for the development of gastric carcinomas and to identify genetic markers associated with tumor progression. The most often involved gains were 2q, 7pq, 8pq, 13q, 17q, 18q, and 20pq. The most commonly deleted regions were 17p. The pattern of genetic changes was different depending on the existence of nodal metastasis and histologic types. Gains in 8q and losses in 17p were the most common features of the CGH changes. However, only 3 among the available 10 cases (30%) showed an amplification of the C-MYC gene by FISH. Allelic loss of TP53 was found in 2 of 4 cases (50%). This difference might be due to another rearrangement of these 2 genes which cannot be detected by FISH, or other possible genes in that area may be involved in the tumorigenesis and nodal metastasis of gastric carcinomas.

Absence of mutations in the kinase domain of the Met gene and frequent expression of Met and HGF/SF protein in primary gastric carcinomas

Hepatocyte growth factor/scatter factor (HGF/SF) and its receptor, Met, are known to play important roles in tumor cell migration, invasion, and metastasis. We analyzed the expression of these genes and the mutations in the kinase domain of the Met gene in 43 gastric carcinomas. Of the 43 cases, the Met and HGF/SF protein were expressed in 29 (67%) and 22 (51%), respectively. All of the cases with HGF/SF immunopositivity also expressed Met. Of 22 cases with HGF/SF immunopositivity, 13 (59%) expressed HGF/SF in tumor cells as well as fibroblasts. We detected no aberrant single-strand conformational polymorphism patterns, suggesting that there are no genetic alterations in the kinase domain of the Met gene. These results indicate that HGF/SF-mediated autocrine and/or paracrine stimulation and overexpression rather than structural alteration of its receptor may contribute to the development and progression of gastric carcinoma, and that expression of Met and HGF/SF may confer a growth advantage to neoplastic cells.