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

Overexpression of the hepatocyte growth factor (HGF) receptor (Met) and presence of a truncated and activated intracellular HGF receptor fragment in locally aggressive/malignant human musculoskeletal tumors

Enhanced hepatocyte growth factor (HGF) receptor (Met) signaling has been suggested to play an important role in the development and progression of various epithelial and nonepithelial tumors. N-terminally truncated forms of the HGF receptor have been shown to be constitutively activated and tumorigenic in animal experiments. In the present study, 102 benign and malignant human musculoskeletal tumors were examined for expression of the HGF receptor by Western blotting and/or immunohistochemistry. A clear predominance of HGF receptor expression was seen in malignant as compared to benign tumors (Western blotting, P < 0.001; immunohistochemistry, P < 0.02). For the first time we show HGF receptor expression in the following four tumor types: dermatofibrosarcoma protuberans, clear cell sarcoma of tendons, malignant primitive neuroectodermal tumor, and benign fibrous histiocytoma. In three cases of sarcoma with high HGF receptor expression by Western blotting, we found indications of a short 85-kd N-terminally truncated HGF receptor that was tyrosine phosphorylated and located in the cytoplasm. Although fragments of this length were seen in 18 of 65 tumors, most were not tyrosine-phosphorylated. Northern blotting revealed only the 7.5-kb full-length HGF receptor transcript, suggesting that the 85-kd fragment is generated by an alternative initiation of translation or by proteolytic cleavage. Southern blotting detected no amplification of the Hgfr/Met gene in the 35 tumors examined, in contrast to our recent report of Hgfr/Met gene amplification in 7, 12-dimethylbenz(a)anthracene (DMBA)-induced rat sarcomas. The present data suggest that the locally aggressive and malignant properties of human mesenchymal tumors maybe related, in part, to high levels of full-length HGF receptors, and in some cases to the occurrence of N-terminally truncated HGF receptors, activated independently of HGF.

Hepatocyte growth factor/scatter factor-induced intracellular signalling

Hepatocyte growth factor (HGF) identical to scatter factor (SF) is a glycoprotein involved in the development of a number of cellular phenotypes, including proliferation, mitogenesis, formation of branching tubules and, in the case of tumour cells, invasion and metastasis. This fascinating cytokine transduces its activities via its receptor encoded by the c-met oncogene, coupled to a number of transducers integrating the HGF/SF signal to the cytosol and the nucleus. The downstream transducers coupled to HGF/MET, most of which participate in overlapping pathways, determine the development of the cell's phenotype, which in most cell types is dual.

Molecular biology of gastric carcinoma: from laboratory to bedside

Although the advancement of molecular oncology in gastric cancer lags behind that of colorectal cancer, the rapid developments witnessed in recent years have improved our understanding of the carcinogenesis, aetiology, progression and metastasis of gastric cancer. The different molecular genetic alterations in intestinal and diffuse types of gastric cancer have further supported the concept that these two pathological types are different disease entities. The association of telomerase and cadherin changes with Helicobacter pylori infection reinforces its aetiological role. The mutated cadherin gene identified in familial gastric cancer has shone light onto the pathogenesis. Adhesion molecules have already been applied to daily clinical practice as prognostic markers. Future molecular studies will contribute to the screening, classification, disease monitoring and therapeutics of gastric cancer.

Dual roles of peptic ulcer in the carcinogenesis or extension of early gastric cancer

BACKGROUND

Early gastric cancer (EGC) often coexists with peptic ulcer. In this study we investigated the roles of peptic ulcer in the carcinogenesis and extension of gastric cancer.

METHODS

The clinicopathological characteristics of EGC and peptic ulcer and their relationship, as well as that of the background intestinal metaplasia, were compared among the following three groups: patients with peptic ulcer only inside the EGC (Contained group, 53 patients); patients with peptic ulcer only outside the EGC (Separate group, 26 patients); and patients of EGC with no peptic ulcer (Absent group, 43 patients).

RESULTS

In the Separate group, a male preponderance was observed (P = .006), and all EGCs developed in the middle or lower third of the stomach (P = .06). Most of the EGCs were an intestinal type of cancer with severe background intestinal metaplasia. Topographically, 88% of the peptic ulcers in the Separate group developed proximal to the EGC. On the other hand, in the Contained group, most EGCs developed in the middle third of the stomach with an intestinal/diffuse type ratio of 1:1. Peptic ulcers inside the EGC were significantly more shallow than those that developed outside the EGC (P = 0.008). Although the incidences of submucosal cancer were nearly the same among the three groups, the maximum cancer diameter tended to be increased in the Contained group compared to that in the Absent group, and the incidence of lymph node involvement tended to be higher in the Contained group (8%) as compared with the other two groups (4%-5%).

CONCLUSIONS

These results suggest that peptic ulcer outside the EGC contributes to the development of the intestinal type of EGC, with the background of more severe intestinal metaplasia during the peptic ulcer healing processes, whereas peptic ulcer inside the EGC develops secondary to EGC and favors cancer extension and metastasis. Peptic ulcer associated with EGC can be considered to exert different biological roles in the carcinogenesis or extension of ECG according to the location of the peptic ulcer.

Induction of c-met proto-oncogene expression at the metastatic site

In metastatic processes, gene expression may variously alter through interactions between tumor and host stromal cells at the metastatic site. Using a tail vein injection-lung metastatic model and differential display, we analyzed alteration of gene expression in experimentally metastasized lesions. We found that expression of the c-met proto-oncogene was elevated in the lungs metastasized by MC-1 cells. The up-regulation of c-met was also observed in the lungs metastasized by B16 melanoma cells. In situ hybridization analysis revealed that the elevation of c-met expression apparently occurred in tumor cells but did not in lung stromal cells at the metastatic site. The c-Met protein was also highly expressed and phosphorylated. The upregulation of c-met appeared to be caused by induction of gene expression but not to be due to preferential selection of tumor cells highly expressing c-met. These findings suggest that the c-met proto-oncogene is up-regulated at the transcription level through some interactions between tumor and host stromal cells.

Amplification and overexpression of the hepatocyte growth factor receptor (HGFR/MET) in rat DMBA sarcomas

In the present study subcutaneous fibrosarcomas were induced by the carcinogen 7,12-dimethylbenz(a)anthracene (DMBA) in rats from F1 generation cross breedings of two different inbred strains. Comparative genomic hybridization (CGH) analysis, which allows detection of DNA sequence copy changes, was applied to one of the tumors and it was found that there were increased copy numbers of sequences at chromosome 4q12-q21 in this tumor. We have previously determined that the loci for the hepatocyte growth factor (Hgf) and hepatocyte growth factor receptor (Hgfr/Met), a protooncogene, are situated in this particular chromosome region. Using probes for the two genes in FISH (fluorescence in situ hybridization) and in Southern blots we found that the Hgfr/Met gene was amplified in five of the 19 sarcomas studied, and that the Hgf gene was coamplified in two of them. Northern and Western blots and tyrosine phosphorylation analysis showed that the HGF receptor was overexpressed and functional in all five tumors, as well as in two additional tumors. In summary, both amplification and overexpression of the Hgfr/Met gene was found in about 25% of DMBA-induced experimental rat sarcomas, and HGF receptor overexpression alone was seen in two additional tumors. Possibly this reflects an involvement in paracrine or autocrine stimulation of growth and invasiveness by HGF. Our finding could provide a rodent model system to increased knowledge about causality and therapy, which may be applicable to the sizeable fraction of human musculoskeletal tumors displaying MET overexpression.

The prognostic significance of amplification and overexpression of c-met and c-erb B-2 in human gastric carcinomas

BACKGROUND

The c-met and the c-erb B-2 protooncogenes belong to a family of tyrosine kinase growth factor receptors. Abnormalities of these oncogenes and protein products have been reported in several cancers. The authors investigated the correlation between clinical factors and amplification or overexpression of the c-met and/or c-erb B-2 gene in Japanese patients with gastric carcinoma patients, with a focus on prognostic significance.

METHODS

Amplification and overexpression of c-met and c-erb B-2 were investigated retrospectively in 128 gastric carcinoma patients by using immunohistochemistry and Southern blot hybridization. Survival analysis was performed with the Kaplan-Meier test, and the log rank test was used for statistical analysis.

RESULTS

Overexpression of c-met and c-erb B-2 was observed in 46.1% and 16.4% of gastric carcinoma cases, respectively. Gene amplification of c-met and c-erb B-2 was detected in 10.2% and 11.7% of gastric carcinoma cases, respectively. Amplification and overexpression of c-met were correlated significantly with depth of tumor invasion and lymph node metastasis, whereas amplification and overexpression of c-erb B-2 were correlated significantly with histologic type. The survival rate of patients with amplification and/or overexpression of c-met or c-erb B-2 was significantly poorer than that of patients with no amplification or overexpression. Multivariate analysis revealed that c-met overexpression and lymph node metastasis were independent prognostic factors.

CONCLUSIONS

These data suggest that overexpression and/or gene amplification of c-met and c-erb B-2 may be prognostic factors in gastric carcinoma.

Chromosome band 16q24 is frequently deleted in human gastric cancer

We have analysed the loss of heterozygosity (LOH) on chromosome bands 16q22-q24 in 24 primary gastric cancer tissues and found three regions of frequent allelic loss (16q22, 16q24.1-q24.3 and 16q24.3). The region for the most frequent allelic loss (63%) was in 16q24.1-q24.3. LOH of this region had no relationship with histological subtype, but a significant association between LOH and microscopic lymphangial invasion was observed. Although not significant, vascular and gastric wall invasions are also associated with LOH. The region includes the locus for the H-cadherin gene. Therefore we examined the genetic and epigenetic alterations of this gene. Markedly reduced expression was observed in gastric cancer cell lines compared with that of normal gastric mucosa. However, no mutation was found in this gene in any of the gastric cancer tissues or the gastric cancer cell lines. Furthermore, we analysed the methylation status of the 5'-flanking region of the gene, but no significant association was found. We suggest that some other tumour suppressor gene(s) in 16q24.1-q24.3 may be responsible for gastric carcinogenesis.

Expression of cell-cycle regulators, cyclin E and p21WAF1/CIP1, potential prognostic markers for gastric cancer

AIMS

The deregulation of cyclin, cyclin-dependent kinases (CDKs) and their inhibitors could have a crucial role in the development of diverse human cancers.

METHODS

In this study, we analysed the expression of cyclin D1, cyclin E, p21WAF1/CIP1 and p27KIP1 in 84 surgically resected gastric cancers by immunohistochemistry with long-term follow-up (median 38 months). We also evaluated the relation between each cell cycle regulator and various clinicopathological findings, including age, sex, histological grade, tumour location, tumour type and stage and lymph-node metastasis.

RESULTS

Overexpression of cyclin D1 and E was detected in 21/84 (25%) and 34/84 (40.5%) patients, respectively. Normal gastric epithelium showed consistently positive immunostain for p21WAF1/CIP1 and p27KIP1 in more than 50% of nuclei. Loss of p21WAF1/CIP1 and p27KIP1 expression was noted in 45/84 (53.6%) and 44/84 (52.4%) patients, respectively. Among the various clinicopathological findings, overexpression of cyclin E was associated with lymph-node metastasis (P=0.003) and recurrence (P=0.043). Loss of p21WAF1/CIP1 expression was more frequent in diffuse type cancers (P=0.005) and was correlated with recurrence (P=0.002) and death (P=0.002). Overexpression of cyclin E and loss of p21WAF1/CIP1 expression were significantly correlated with decreased disease-free (P=0.037; P= 0.001) and overall (P=0.031; P=0.001) survival.

CONCLUSIONS

These results suggest that immunohistochemical analysis for cell cycle regulators, especially cyclin E and p21WAF1/CIP1, might be a useful prognostic indicator in gastric cancer.

Mapping of chromosomal imbalances in gastric adenocarcinoma revealed amplified protooncogenes MYCN, MET, WNT2, and ERBB2

Gastric adenocarcinoma is a malignant tumor with a high incidence and a low survival rate. In order to identify genetic alterations associated with this tumor, we screened 23 gastric adenocarcinomas for recurrent chromosomal imbalances by using comparative genomic hybridization (CGH). The most common gains of chromosomal material were found on chromosome arms 20q (10 cases), 16p (7 cases), and 1q (4 cases) and on chromosome 11 (4 cases). Losses were observed on chromosome arms 4q, 5q, 9p, and 21q (3 cases each). Four tumors exhibited high-level amplifications localized on chromosome regions 2p23-p24, 7q31-q32, 8p21-p22, 10q25-q26, 11q13, 17q11-q21, and 20q. Based on the position of these amplifications, candidate (onco)genes were selected and subsequently tested by Southern blot analysis of the respective tumors. Of the seven tested candidates, MYCN, MET, WNT2, and ERBB2 were found to participate in the amplicons of the respective tumor samples. Of these four presumably activated oncogenes, two, MYCN and WNT2, were previously not assumed to play a pathogenic role in stomach cancer. Among the other regions of imbalance, gain of 20q seems particularly interesting, because it is found in almost half of the analyzed cases and is highly amplified. Our data allowed us to narrow the relevant region down to the commonly gained bands 20q12-q13.1. This and other imbalanced regions provide a basis for searching new putative oncogenes and tumor suppressor genes involved in the development or progression of gastric adenocarcinoma.

High levels of hepatocyte growth factor/scatter factor in diffuse-type bronchioloalveolar cell carcinoma

BACKGROUND

Hepatocyte growth factor/scatter factor (HGF/SF) is a potent mitogen for various neoplastic cells, including neoplastic bronchial epithelia.

METHODS

Immunoreactive hepatocyte growth factor/scatter factor (HGF/SF) was measured in extracts prepared from 129 nonsmall cell lung carcinoma (NSCLC) specimens, using an enzyme-linked immunosorbent assay. These specimens represented 5 cases of solitary/localized bronchioloalveolar cell carcinoma (BAC), 4 cases of diffuse/infiltrative BAC, 90 cases of non-BAC adenocarcinoma, 25 cases of squamous cell carcinoma, and 5 cases of large cell carcinoma.

RESULTS

The mean concentration of immunoreactive HGF/SF was more than 19-fold higher in tissue extracts from diffuse-type BAG (265.0 +/- 110.2 ng/100 mg protein) than in those from solitary-type BAC (13.9 +/- 15.9, P < 0.005), non-BAC adenocarcinoma (13.8 +/- 14.9, P < 0.001), squamous cell carcinoma (13.2 +/- 14.4, P < 0.001), or large cell carcinoma (11.2 +/- 6.5, P < 0.005). When immunohistochemical staining for HGF/SF was performed, intense HGF/SF staining was uniformly observed in diffuse-type BAC tumor cells, but not in solitary-type BAC.

CONCLUSIONS

Although BAC is included as a subtype of adenocarcinoma in the World Health Organization classification, diffuse-type BAC should be considered a distinct biologic entity, at least in terms of HGF/SF expression, from solitary-type BAC or non-BAC adenocarcinoma. In addition, the solitary and diffuse forms of BAC are known to be associated with different prognoses; for the latter, the prognosis is much poorer than for the former. The results of this study may at least partly explain this difference in prognosis.

Hepatocyte growth factor and the kidney: it is not just for the liver

Mesenchymal-epithelial interactions are important for many biological processes in epithelial organs such as the kidney. Hepatocyte growth factor (HGF) is a mesenchymally derived polypeptide cytokine that acts through its tyrosine kinase c-met receptor and is an important mediator of these interactions. This article reviews data showing the in vitro actions of HGF on renal epithelial cells that result in such diverse responses as mitogenesis, motogenesis, and morphogenesis. It also examines the in vivo evidence linking HGF and the c-met receptor to kidney development, regeneration following injury, and renal disease. Elucidating cellular mechanisms underlying the coordinated control of diverse HGF-induced phenotypic changes in renal epithelia in vitro should contribute to a clearer understanding of complex biological processes such as organogenesis, regeneration, and carcinogenesis in epithelial organs such as the kidney.

Alterative expression of the collagenase and adhesion molecules in the highly metastatic clones of human colonic cancer cell lines

Human colonic carcinoma cell lines, KM12C, KM12SM and KM12L4, were previously established and their in vivo metastatic potentials have been well evaluated. The highly metastatic cell lines KM12SM and KM12L4 were derived from the parental low metastatic cell line KM12C in vivo. To evaluate the metastatic behavior of these cell lines in vitro, we examined colony formation on monolayers of the pulmonary arterial endothelial (CPAE) cells. On day 4, the highly metastatic cell lines showed an approximately 2-fold increase in number of colonies on CPAE cell monolayers relative to the parental KM12C cell line. To investigate what evidence is correlated with their metastatic and invasive abilities, Northern blot analysis and flow cytometry were performed in all cell lines. According to the results of Northern blot analysis, the levels of matrix metalloproteinase (MMP)-2 and c-met mRNA expression were increased in highly metastatic cell lines as compared with the parental cell line. We also examined the cell-surface expression of several adhesion molecules by flow cytometry. The levels of expression of sialyl Lewisa antigen (sLe(a)) in KM12SM and KM12L4 were twice higher than that in KM12C. However, the levels of expression of E-cadherin in KM12SM and KM12L4 were decreased to half that in KM12C. The alterative expression of the collagenase and adhesion molecules might contribute to their metastatic/invasive abilities of these cell lines both in vivo and in vitro.

Prognostic factors in gastric cancer

BACKGROUND

Despite gastric cancer being common, its prognosis has not been improved significantly in recent years. Now, greater insight has been gained into the biological properties of tumour cells, how they become malignant and what mechanisms they may use to invade and metastasize. This involves tumour-associated protease systems, loss or mutation of adhesion molecules and changes in genetics. The view of gastric cancer is changing: it is not only a solid tumour but also exhibits a minimal residual disease component even in the early stages of disease. Such biological tumour characteristics may provide new prognostic factors and also potential new therapeutic options.

METHODS

This is an update of prognostic factors in gastric cancer, emphasizing new biological features, some of which have been investigated by this group over the past few years. Current results are discussed in the light of 212 references obtained from the Medline database from 1979 to 1997.

RESULTS

There is high probability that some of the factors reviewed, such as c-erbB-2, individual course and phenotyping of disseminated tumour cells will become significant new prognostic variables. This is true also, to a lesser extent, of cathepsin D, matrix metalloproteinase 2 combined with activators or tissue inhibitor of metalloproteinases 2, CD44, E-cadherin, p53 and cripto. Plasminogen activator inhibitor 1 (PAI-1), a member of the urokinase-type plasminogen activator (uPA) system, can already be defined as an established new prognostic factor in gastric cancer.

CONCLUSION

PAI-1 should be considered prognostically in addition to established tumour classifications. Moreover, the uPA system is a target for future therapeutic concepts. Further analysis of factors describing tumour biology should lead to new, functionally orientated, tumour classifications in gastric cancer.

Frequency of chromosome 7 gain in human breast cancer cells: correlation with the number of metastatic lymph nodes and prognosis

Trisomy 7 has been reported in various malignant neoplasms, but there are no reports in breast cancer. In order to evaluate the contribution of chromosome 7 gain to breast cancer, we investigated the relationship of numerical abberation of chromosome 7 with clinicopathological variables and prognosis in seventy-nine breast cancer cases (invasive carcinomas) using the technique of fluorescence in situ hybridization (FISH) on paraffin-embedded sections. A significant correlation of the frequency of cells with extra copies of chromosome 7 (percent polysomy 7 cell score) was found with tumor size, regional lymph node status, tnm stage, histological extension, estrogen receptor (ER), and DNA ploidy. The number of metastatic lymph nodes was positively correlated with percent polysomy 7 cell score (correlation coefficient=0.623, p < 0.01). Furthermore, cases with a high percent polysomy 7 cell score had a shorter disease-free survival and overall survival times, especially in the lymph node-positive group. It was demonstrated that percent polysomy 7 cell value was closely associated with lymph node metastasis and prognosis and might be a useful prognostic predictor of breast cancer patients.

Correlation of hepatocyte growth factor-induced proliferation and calcium-activated potassium current in human gastric cancer cells

Hepatocyte growth factor (HGF) has been found to stimulate proliferation and migration of human gastric carcinoma cells. Whether the HGF-induced responses are correlated with the expressed level of HGF receptors or the changes of ionic currents is not clear. The present study investigated the effects of HGF on the proliferation and ionic currents of two human gastric adenocarcinoma cell lines, which were found to express different amounts of HGF receptor. Results showed that HGF induced a dose-dependent growth stimulation and accelerated cell cycle progression in SC-M1 cells. In patch clamp study, HGF treatment induced an outward K+ current and increased the slope conductance at -80 mV from 110+/-15 pS/pF to 207+/-15 pS/pF. The HGF-induced K+ current was abolished when tetraethylammonium chloride was added in bathing solution or a low Ca2+ solution was included in the recording pipette. Furthermore, HGF (10 ng/ml) induced an oscillatory Ca2+-activated K+ current with a lag period of 5+/-3 min in SC-M1 cells. In contrast, HGF did not induce mitogenesis, cell cycle progression and changes in ionic currents in KATO-III cells, although this cell line expressed a higher level of HGF receptors than SC-M1 cells did. These findings provide evidence that the activity of Ca2+-activated K+ channel may be involved in the HGF-induced cell proliferation in human gastric cancer cells, but it did not correlate with the density of HGF receptors.

Expression of c-met proto-oncogene in primary colorectal cancer and liver metastases

We have examined the expression of c-met mRNA in tissue from 27 colorectal cancers and ten liver metastases using the reverse transcriptase-polymerase chain reaction method. The expression of c-met mRNA in these tissues was quantified and the copy number of c-met mRNA to 10(8.0) copies of beta-actin mRNA was calculated. Mean copy numbers of c-met mRNA in cancer tissue and normal mucosa were 10(5.5) and 10(4.5) respectively. The c-met expression of cancer was significantly higher than that of normal mucosa (P < 0.0001). In 20 of 22 samples in which c-met expression of both tumor and corresponding normal tissue were examined, c-met was overexpressed in the cancer tissue. No correlation was found between c-met expression and the clinicopathologic background. The mean copy numbers of c-met mRNA in the tissue from the ten liver metastases and normal liver were 10(6.1) and 10(6.2) respectively. Although c-met expression in metastatic tissue was higher than that in the primary cancer tissue, the increase was not statistically significant. In three of four patients with synchronous liver metastases, c-met was overexpressed in the metastatic tissue compared with that in the corresponding primary cancer tissue. These results show that c-met is overexpressed in both primary colorectal cancer and liver metastases and suggest that c-met plays a role in the development of colorectal cancer liver metastases.

17q12-21 amplicon, a novel recurrent genetic change in intestinal type of gastric carcinoma: a comparative genomic hybridization study

We studied DNA copy number changes in gastric cancer (GC) using comparative genomic hybridization (CGH) analysis on 35 resected gastric carcinomas (22 of the intestinal type and 13 of the diffuse type). Eighty-three percent of the cases showed DNA copy number changes. Gains were more common than losses (median of 3 and 1 in primary tumors of the intestinal and diffuse type, respectively). The most common gains were detected on 20q [46%; 12 intestinal type (55%) and four diffuse type (31%)], 8q [37%; 10 intestinal type (45%) and three diffuse type (23%)], and 17q12-21 [29%; all but one intestinal type (41%)]. The most frequent losses were detected on 18q [26%; all intestinal type (41%)] and on 4q [23%; all intestinal type (32%)]. High-level amplifications were observed in the intestinal type of tumors at 17q12-21 (three tumors), 20q (three tumors). 2q (one tumor), and 18q (one tumor). In the diffuse type, high-level amplification was detected once at 13q.

Gastric cancer associated with overexpression of parathyroid hormone-related peptide (PTHrP) and PTH/PTHrP receptor in relation to tumor progression

Parathyroid hormone-related peptide (PTHrP) is involved in cell proliferation in both neoplastic and non-neoplastic tissues. We describe an autopsy case of gastric cancer in a patient who showed serum hypercalcemia and overexpression of PTHrP and PTH/PTHrP receptor in the metastatic tumor cells. The primary gastric tumor was poorly differentiated adenocarcinoma, and multiple metastases were present in the bone, multiple visceral organs, peritoneum, and lymph nodes. PTHrP and its mRNA were detected only in the metastatic tumor cells, but not in primary gastric tumor. PTH/PTHrP receptor was also demonstrated immunohistologically in metastatic tumor cells. This case suggests that the expression of PTHrP is related to tumor progression and the poor prognosis in tumors associated with humoral hypercalcemia.

Transforming growth factor-beta and hepatocyte growth factor produced by gastric fibroblasts stimulate the invasiveness of scirrhous gastric cancer cells

Scirrhous gastric carcinoma is characterized by cancer cells that infiltrate rapidly in the stroma with extensive growth of fibroblasts. In the present study, we examined the effect of gastric fibroblasts on the invasiveness of a scirrhous gastric cancer cell line, OCUM-2D, using an invasion assay. Gastric fibroblast-derived conditioned medium (CM) significantly stimulated the invasiveness of OCUM-2D cells, as did transforming growth factor-beta (TGF-beta) and hepatocyte growth factor (HGF). The stimulating activity of gastric fibroblast-derived CM was inhibited significantly by anti-TGF-beta neutralizing antibody or anti-HGF neutralizing antibody. TGF-beta and HGF were detected in the gastric fibroblast-derived CM, and TGF-beta receptor and C-met (HGF receptor) were expressed on OCUM-2D cells. Thus, TGF-beta and HGF produced by gastric fibroblasts appear to affect the invasiveness of scirrhous gastric cancer cells. TGF-beta was also detected in the conditioned medium derived from OCUM-2D cells, though HGF was not. TGF-beta appears to affect the invasiveness of OCUM-2D cells in both paracrine and autocrine fashions.

Diverse tumorigenesis associated with aberrant development in mice overexpressing hepatocyte growth factor/scatter factor

Hepatocyte growth factor/scatter factor (HGF/SF) is a mesenchymally derived, multifunctional paracrine regulator possessing mitogenic, motogenic, and morphogenetic activities in cultured epithelial cells containing its tyrosine kinase receptor, Met. c-met has been implicated in oncogenesis through correlation of expression with malignant phenotype in specific cell lines and tumors. Paradoxically, however, HGF/SF can also inhibit the growth of some tumor cells. To elucidate the oncogenic role of HGF/SF in vivo, transgenic mice were created such that HGF/SF was inappropriately targeted to a variety of tissues. HGF/SF transgenic mice developed a remarkably broad array of histologically distinct tumors of both mesenchymal and epithelial origin. Many neoplasms arose from tissues exhibiting abnormal development, including the mammary gland, skeletal muscle, and melanocytes, suggesting a functional link between mechanisms regulating morphogenesis and those promoting tumorigenesis. Most neoplasms, especially melanomas, demonstrated overexpression of both the HGF/SF transgene and endogenous c-met, and had enhanced Met kinase activity, strongly suggesting that autocrine signaling broadly promotes tumorigenesis. Thus, subversion of normal mesenchymal-epithelial paracrine regulation through the forced misdirection of HGF/SF expression induces aberrant morphogenesis and subsequent malignant transformation of cells of diverse origin.

Increase in the circulating level of hepatocyte growth factor in gastric cancer patients

We measured serum concentrations of hapatocyte growth factor (HGF) in patients with gastric cancer and compared these with the histological findings and conventional tumour markers, including CEA, CA19-9 and CA125, for evaluation of the significance of serum HGF levels as a tumour marker. The HGF levels were measured by an enzyme-linked immunosorbent assay (ELISA) system. The average levels of serum HGF in 89 healthy control subjects, 104 patients with primary gastric cancer and 15 patients with recurrent gastric cancer were 0.31 +/- 0.11 ng ml(1), 0.42 +/- 0.50 ng ml(-1) and 0.92 +/- 0.39 ng ml(-1) respectively. The average level in patients with recurrent disease was significantly higher than in healthy control subjects and in primary cancer patients (P< 0.001 and P< 0.003 respectively). Of 104 patients with primary gastric cancer, 35 (33.7%) showed an aberrant increase in the circulating level of HGF. The increased HGF levels were significantly associated with the degrees of histological tumour invasion and venous invasion. Of 15 patients with recurrent gastric cancer, 14 (93.3%) showed an aberrant increase. No correlation was found between serum HGF levels and CEA levels, CA19-9 levels and CA125 levels. However, the rate of the aberrant increase in HGF levels was significantly higher than that of any other tumour markers, including CEA, CA19-9 and CA125, in primary gastric cancer patients. In conclusion, the circulating levels of HGF were elevated in approximately one-third of patients with primary gastric cancer, particularly in those with high grades of histological tumour invasion and venous invasion, and frequently in patients with distant metastases, suggesting that HGF might play important roles in the tumour progression of gastric cancer. Furthermore, serum HGF levels may be of value as a tumour marker in patients with gastric cancer.

Involvement of hepatocyte growth factor in increased integrin expression on HepG2 cells triggered by adhesion to endothelial cells

Adhesion of cancer cells to vascular endothelium is an important step in haematogenous metastasis of cancer. A human hepatocellular carcinoma cell line, HepG2, strongly adheres to human umbilical vein endothelial cells (HUVECs) through the interaction of E-selectin and its carbohydrate ligand sialyl Lewis X. In this study, we investigated alteration in integrin expression on HepG2 cells, which follows the selectin-mediated initial adhesion of HepG2 cells to HUVECs. Expression of alpha2beta1 integrin was markedly increased when the HepG2 cells adhered to HUVECs. Among the tested cytokines that are known to be produced by endothelial cells, recombinant hepatocyte growth factor (rHGF) could replace the effect of HUVECs, and a similar increase in integrin expression was observed by the addition of 20 ng ml-1 rHGF to HepG2. The increment of alpha2beta1 integrin expression was significantly inhibited by anti-HGF neutralizing antibody treatment. HepG2 cells expressed alpha2, alpha6, beta1, and beta4 integrin subunits, but expression of integrins other than alpha2beta1 was not affected by the rHGF treatment. The rHGF treatment of HepG2 cells resulted in augmented adhesion to immobilized collagen. This augmentation in adhesion to collagen was completely blocked by the addition of anti-alpha2- or anti-beta1-integrin antibody. In double-chamber chemoinvasion experiments, transmigration of the HepG2 cells through extracellular matrix (ECM) gel was significantly accelerated by co-cultivation with HUVECs. A similar level of enhancement in transmigration activity of the cancer cells was observed by the addition of rHGF. Our interpretation of the results described above is that the cancer cells received stimulation from cytokines, such as HGF, presented by vascular endothelial cells, following the initial adhesion of cancer cells via selectins. This resulted in the secondary increment in the expression of cell adhesion molecules, such as the alpha2beta1 integrin, and led to the augmented adhesive activities of cancer cells towards extracellular matrices at vascular walls. We suggest that this sequence of events is involved in the facilitated migration of some cancer cells to extravascular tissues.

Expression of multidrug-resistance-associated protein (MRP) and chemosensitivity in human gastric cancer

Evidence has accumulated that, in addition to the MDR1 gene-coded P-glycoprotein (Pgp), multidrug resistance-associated protein (MRP) also mediates the multidrug resistance (MDR) of various human tumors. In the case of gastric cancer, there is little or no involvement of P-glycoprotein, and the mechanisms of MDR remain to be understood. To search for a possible relationship between expression of MRP and sensitivity to anti-cancer agents in gastric cancer, 4 gastric cancer cell lines, 43 human gastric carcinomas and 17 adjacent normal gastric tissue samples were analyzed. Expression of MRP mRNA was evaluated using reverse transcription PCR (RT-PCR) and Southern hybridization. Sensitivity of the test samples to the anti-cancer drugs cisplatin (CDDP), doxorubicin (DXR) and etoposide (VP-16) was examined using the MTT¿3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl [2H]-tetrazolium bromide¿ assay. Immunohistochemical staining with the use of the MRP antibody (MRPr1) was done to confirm the findings regarding the expression of mRNA levels. The MRP expression evaluated with RT-PCR and Southern hybridization as well as with immunohistochemical staining revealed that 23 of 43 gastric-cancer tissues (53.5%), 15 of 17 normal gastric tissues (88%) and 3 of 4 gastric-cancer cell lines (75%) were positive. The MTT assay showed that DXR was significantly more sensitive (p < 0.01) in gastric carcinoma tissues lacking MRP expression than in those with positive expression. The same tendency was seen with the other agents used. Of the cell lines, one which showed no MRP expression also had a higher sensitivity to CDDP, DXR and VP-16 than the other positive cases. These results show that MRP expression is involved in MDR of human gastric cancer and is inversely related to the chemosensitivity of tumor cells against some anticancer drugs.

Hepatoblastoma in an adult associated with c-met proto-oncogene imbalance

A rare case of hepatoblastoma in a 61-year-old Japanese housewife is described. This liver tumor mainly consisted of two tissue components: embryonal hepatocytes and primitive mesenchymal tissue. Fetal hepatocytes with alpha-fetoprotein production, gland formation, cartilage and osteoid were also found in a small portion. Molecular analysis by slot blot method revealed increased copy numbers of c-met and K-sam proto-oncogenes and cyclin D1 genes. These findings suggest that alterations of these oncogenes might play a role in the development of adult hepatoblastoma.

Expression of multidrug-resistance-associated protein (MRP) and chemosensitivity in human gastric cancer

Evidence has accumulated that, in addition to the MDR1 gene-coded P-glycoprotein (Pgp), multidrug resistance-associated protein (MRP) also mediates the multidrug resistance (MDR) of various human tumors. In the case of gastric cancer, there is little or no involvement of P-glycoprotein, and the mechanisms of MDR remain to be understood. To search for a possible relationship between expression of MRP and sensitivity to anti-cancer agents in gastric cancer, 4 gastric cancer cell lines, 43 human gastric carcinomas and 17 adjacent normal gastric tissue samples were analyzed. Expression of MRP mRNA was evaluated using reverse transcription PCR (RT-PCR) and Southern hybridization. Sensitivity of the test samples to the anti-cancer drugs cisplatin (CDDP), doxorubicin (DXR) and etoposide (VP-16) was examined using the MTT¿3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl [2H]-tetrazolium bromide¿ assay. Immunohistochemical staining with the use of the MRP antibody (MRPr1) was done to confirm the findings regarding the expression of mRNA levels. The MRP expression evaluated with RT-PCR and Southern hybridization as well as with immunohistochemical staining revealed that 23 of 43 gastric-cancer tissues (53.5%), 15 of 17 normal gastric tissues (88%) and 3 of 4 gastric-cancer cell lines (75%) were positive. The MTT assay showed that DXR was significantly more sensitive (p < 0.01) in gastric carcinoma tissues lacking MRP expression than in those with positive expression. The same tendency was seen with the other agents used. Of the cell lines, one which showed no MRP expression also had a higher sensitivity to CDDP, DXR and VP-16 than the other positive cases. These results show that MRP expression is involved in MDR of human gastric cancer and is inversely related to the chemosensitivity of tumor cells against some anticancer drugs.

Hepatocyte growth factor/scatter factor-Met signaling in tumorigenicity and invasion/metastasis

Hepatocyte growth factor/scatter factor (HGF/SF) is a pleiotropic effector of cells expressing the Met tyrosine kinase receptor. While HGF/SF-Met signaling clearly plays a role in a variety of normal cellular process, this signaling pathway has also been implicated in the generation and metastatic spread of tumors. This review discusses in detail several model systems that have been developed to investigate the role of HGF/SF-Met signaling in malignancy and describes additional data regarding the expression of these molecules in human tumors. Collectively the findings support a role for this receptor-ligand pair in human malignancy.

Acquisition of invasive phenotype in gallbladder cancer cells via mutual interaction of stromal fibroblasts and cancer cells as mediated by hepatocyte growth factor

Growth and motility of carcinoma cells are regulated through their interactions with host stromal cells, i.e., tumor-stromal interactions. Hepatocyte growth factor (HGF), a ligand for c-Met tyrosine kinase, is a stromal-derived regulator of growth, motility, and morphogenesis. HGF stimulated proliferation and motility of GB-d1 gallbladder carcinoma cells from a patient with gallbladder cancer. HGF induced in vitro invasion of GB-d1 cells into a collagen gel matrix, and this potent, invasive effect was not seen with epidermal growth factor, transforming growth factor-beta 1, basic fibroblast growth factor, or platelet-derived growth factor. Although GB-d1 did not produce HGF, the cells did produce a factor which enhances HGF production in human skin fibroblasts, and this factor proved to be interleukin-1 beta (IL-1 beta). When GB-d1 cells were co-cultured with fibroblasts such that a collagen gel matrix was layered between the GB-d1 cells and fibroblasts, GB-d1 cells invaded the gel, but invasion of the cells in the co-culture system was inhibited by antibodies against HGF and partially inhibited by antibodies against IL-1 beta. Thus, GB-d1 cell-derived IL-1 beta stimulates HGF production in stromal fibroblasts and HGF up-regulated in the fibroblasts induces invasion of GB-d1 cells. The looped interaction of carcinoma cells and stromal fibroblasts mediated by HGF and a HGF-inducer such as IL-1 beta may be one mechanism which would explain the acquisition of malignant phenotype through tumor-stromal interactions.

Expression of immunoreactive human hepatocyte growth factor in human esophageal squamous cell carcinomas

Hepatocyte growth factor (HGF) is a potent mitogen for epithelial cells that promotes cell motility and invasiveness. In this study, we report that the human esophageal squamous cell carcinoma (SCC) shows a significant elevation of HGF concentration (600 +/- 416 ng/100 mg protein), compared to normal mucosa (80 +/- 183 ng/100 mg protein) (P < 0.01). An association could be established between levels of HGF and decreasing differentiation of 37 SCCs. The 2-year crude survival rates were 51.1% and 68.4% at high and low HGF concentrations, respectively. The results indicate that HGF is significantly increased in human esophageal SCCs, especially of poorly differentiated type. HGF might thus be useful as a biological biomarker for characterization of human esophageal SCCs.

Frequent amplification of the cyclin E gene in human gastric carcinomas

We searched for genetic alterations of the cyclin D1 and cyclin E genes in 45 human gastric carcinoma tissues. Expression of cyclin E mRNA and protein was also analyzed in eight of them by Northern and Western blots and immunohistochemical staining. The cyclin E gene was amplified 3-10 fold in seven gastric cancer tissues (15.6%), of which six were advanced gastric cancers. All of the cases with the cyclin E gene amplification displayed lymph node metastasis. Moreover, the case with the gene amplification overexpressed the cyclin E mRNA and protein. One of eight gastric cancer cell lines, MKN-7, shared the cyclin E gene amplification, and all of the gastric cancer cell lines expressed high levels of the cyclin E mRNA and protein even without gene amplification. Amplification of the cyclin D1 gene was not observed in any of the gastric carcinoma tissues or gastric carcinoma cell lines. These results suggest that the gene amplification and overexpression of cyclin E play an important role in the abnormal growth and progression of gastric carcinoma.

Molecular biology of gastric cancer

Gastric cancer involves changes in multiple oncogenes and multiple suppressor genes, and it causes genetic instability. Aberrant expression and amplification of the c-met gene, inactivation of the p53 gene, and CD44 abnormal transcripts are common events of both well differentiated and poorly differentiated gastric cancers. Amplification of the cyclin E gene is also observed in gastric cancer regardless of histologic type. Decreased expression of the pic1 (p21) gene occurs independent of the p53 mutations. In addition, K-ras mutations, c-erbB-2 gene amplification, loss of heterozygosity (LOH) and mutations of the APC gene, LOH of the bcl-2 gene, and LOH at the DCC locus are preferentially associated with well differentiated gastric cancer. Moreover, LOH on chromosome 1q is involved in the progression of well differentiated cancer. Precancerous lesions, including hyperplastic polyp, intestinal metaplasia, and adenoma, share genetic changes found in well differentiated cancers. Conversely, genetic instability may be involved in the first step of stomach carcinogenesis of the poorly differentiated type. Reduction or loss of cadherin and catenins, K-sam gene amplification, and c-met gene amplification are necessary for the development and progression of poorly differentiated or scirrhous carcinoma. Interaction between cell-adhesion molecules in the c-met expressed tumor cells and hepatocyte growth factor from stromal cells is implicated in the morphogenesis of two types of gastric cancer.(ABSTRACT TRUNCATED AT 250 WORDS)

Genetic alterations in human gastrointestinal cancers. The application to molecular diagnosis

Gastrointestinal cancers involve genetic alterations in multiple oncogenes, multiple tumor suppressor genes, and multiple DNA repair genes. However, common and different genetic changes are observed in esophageal, gastric, and colorectal carcinomas, respectively. Inactivation of the p53 gene and expression of CD44 abnormal transcripts are common events that serve as a powerful tool for cancer diagnosis. Gene amplification of cyclin D is found preferentially in esophageal cancer, whereas gene amplification of cyclin E and c-met is frequently associated with gastric cancer. Mutations of the cyclin-dependent kinase inhibitor genes also occur in esophageal and gastric cancers. However, the scenario of multiple gene changes differs depending on the two histologic types of gastric cancer, because they may have different genetic pathways. Interestingly, the frequency of genetic instability is also quite different between the two types of gastric cancer. A new strategy of molecular diagnosis for gastrointestinal cancers, which started as routine work at Hiroshima City Medical Association Clinical Laboratory last August, may provide a new approach to cancer diagnosis for the next decade.

The Met-HGF/SF autocrine signaling mechanism is involved in sarcomagenesis

Hepatocyte growth factor/scatter factor (HGF/SF) can elicit a wide variety of effects upon cells expressing its receptor, the tyrosine kinase proto-oncogene product Met, including mitogenicity, motility, and morphogenesis. Normally, met expression is restricted to epithelial cells and is activated in a paracrine fashion by HGF/SF secreted from cells of mesenchymal origin. In this chapter, we review data showing that: (i) met over-expression in HGF/SF-expressing NIH/3T3 fibroblasts leads to sarcomagenesis and metastasis via an autocrine mechanism; (ii) Met-HGF/SF autocrine signalling occurs to a low level in normal fibroblasts and to a much greater extent in human sarcomas and sarcoma cell lines; (iii) met expression is enhanced as p53-deficient fibroblasts are passaged in vitro and (iv) met and HGF/SF over-expression are selected for during tumorigenesis of p53-deficient late-passage fibroblasts. Thus, loss of p53 predisposes a mesenchymal cell to over-express met and high level Met-HGF/SF autocrine signaling in mesenchymal cells promotes both sarcomagenesis and metastasis through inappropriate induction of the pleiotropic responses to Met-HGF/SF stimulation.

Factors controlling growth, motility, and morphogenesis of normal and malignant epithelial cells

Factors that control epithelial growth, motility, and morphogenesis play important roles in malignancy and in normal development. Here we discuss the molecular nature and the function of two types of molecules that control the development and maintenance of epithelia: Components that regulate epithelial cell adhesion; and soluble factors and their receptors that regulate growth, motility, differentiation, and morphogenesis. In development, the establishment of epithelial cell characteristics and organization is crucially dependent on cell adhesion and the formation of functional adherens junctions. The integrity of adherens junctions is frequently disturbed late in tumor progression, and the resulting loss of epithelial characteristics correlates with the metastatic potential of carcinoma cells. Various soluble factors that induce epithelial growth, motility, or differentiation in cell culture, function via tyrosine kinase receptors. We concentrate here on receptors that are expressed exclusively or predominantly on epithelia, and on ligands that are derived from the mesenchyme. In development, these receptors and their ligands function in mesenchymal-epithelial interactions, which are known to govern growth, morphogenesis, and differentiation of epithelia. During tumor development, mutations or overexpression of the receptors are frequently observed; these alterations contribute to the development and progression of carcinomas.

Frequent loss of heterozygosity of the long arm of chromosome 7 is closely associated with progression of human gastric carcinomas

Loss of heterozygosity (LOH) on the long arm of chromosome 7 was examined using 5 polymorphic marker probes on 98 gastric carcinomas to elucidate a novel locus for development and progression of the tumors. Twenty-six (32%) of 82 informative cases showed LOH on 7q on at least one locus of 5 loci. Among 5 loci, LOH at D7S95 locus was most frequent, the incidence being 53% in well-differentiated gastric carcinomas and 33% in poorly differentiated and scirrhous gastric carcinomas respectively. At 3 loci, c-met, D7S63 and D7S22, the incidence of LOH was about 30% and 10% in well-differentiated and poorly differentiated gastric carcinoma cases respectively. In contrast, LOH at D7S64 was not detected in any gastric-carcinoma cases. Deletion mapping of 7q revealed that D7S95 locus was the essential region of LOH. Eight (62%) of 13 cases with LOH at D7S95 locus belonged to the most advanced stage grouping. Furthermore, 6 (75%) of 8 cases with abdominal dissemination showed LOH at D7S95. Therefore, cases with LOH at D7S95 showed significantly worse prognosis than the cases without the LOH in the stage-III and stage-IV groups. These findings overall suggest that D7S95 locus on 7q may contain a candidate suppressor gene for the progression of gastric carcinoma.

Effect of hepatocyte growth factor on the expression of E- and P-cadherin in gastric carcinoma cell lines

Hepatocyte growth factor (HGF), identical to scatter factor, (SF) is a secretory glycoprotein from fibroblasts which dissociates and increases the motility of various types of epithelial cells. After treatment of three gastric carcinoma cell lines (MKN-28, MKN-45 and TMK-1) with HGF (10 ng/ml), TMK-1 cells lost their tight cell to cell contact and showed marked scattering, while the two other cell lines remained unaffected. To learn about the underlying mechanism of the HGF induced scattering, we examined the expression of adhesion molecules and growth factor/receptor systems at the mRNA and protein level. The observed scattering of treated TMK-1 cells was associated with a reduction in the expression of E- and P-cadherin protein. The respective mRNA levels remained unchanged after HGF/SF treatment. In the two other cell lines, which showed no scattering, there were no changes in the expression of E- and P-cadherin. All other growth factors and their receptors examined (TGF-alpha, EGFR, c-met and c-erbB2) remained constant and were not affected by HGF treatment. The results suggest that HGF/SF may regulate cell adhesion in gastric carcinomas via E- and P-cadherin expression at the protein level.

Hepatocyte growth factor/scatter factor, liver regeneration and cancer metastasis

Hepatocyte growth factor (HGF) is the most potent stimulator of hepatocyte growth and DNA synthesis identified; it is now known to be the same molecule as scatter factor, which increases the motility of a variety of cell types. HGF is becoming recognized as one of the most important factors in the regulation of liver regeneration after surgical resection or chemical damage. HGF is produced by several tissues, including neoplasms; it can therefore provide a stimulus for increased motility of malignant cells by both a paracrine and autocrine mechanism. The receptor for HGF has been identified as the product of the oncogene c-met, raising the possibility that this gene plays a key role in facilitating cellular invasion. HGF may therefore be important not only for liver cell growth but also in metastasis. This article summarizes the current position of research on HGF, and presents both clinical and scientific evidence that strongly implicates this factor in liver regeneration and cancer invasion and metastasis.

Aberrant expression of c-met mRNA in human gastric carcinomas

We examined mRNA expression for c-met encoding hepatocyte growth factor receptor in 8 gastric carcinoma cell lines and 31 surgically resected gastric carcinoma tissues by Northern-blot analysis. Two forms of the transcript, sized 7.0 kb and 6.0 kb, were found in gastric carcinomas. Transcripts of both sizes were detected at various levels in all the gastric carcinoma cell lines except the MKN-74 line, which expressed only the 7.0-kb form. Of the 31 gastric carcinomas, 15 (48%) over-expressed the 7.0-kb transcript when compared with non-neoplastic mucosa. The 6.0-kb transcript of the c-met gene was expressed at considerable levels in 52% of the gastric carcinoma tissues, whereas it was only slightly expressed in non-neoplastic mucosa of a small number of cases. An important finding was that expression of the 6.0-kb transcript was closely correlated with tumor staging, lymph-node metastasis and depth of tumor invasion. These results, overall, suggest that the 6.0-kb transcript of the c-met gene might participate in the development and progression of gastric carcinomas.