A novel experimental mouse model of peritoneal dissemination of human gastric cancer cells: different mechanisms in peritoneal dissemination and hematogenous metastasis

Soluble factors in malignant ascites promote the metastatic adhesion of gastric adenocarcinoma cells

BACKGROUND

Adenocarcinoma of the proximal stomach is the fastest rising malignancy in North America. It is commonly associated with peritoneal accumulation of malignant ascites (MA), a fluid containing cancer and inflammatory cells and soluble proteins. Peritoneal metastasis (PM) is the most common site of gastric cancer (GC) progression after curative-intent surgery and is the leading cause of death among GC patients.

METHODS/RESULTS

Using a panel of gastric adenocarcinoma cell lines (human: MKN 45, SNU-5; murine: NCC-S1M), we demonstrate that prior incubation of GC cells with MA results in a significant (> 1.7-fold) increase in the number of cells capable of adhering to human peritoneal mesothelial cells (HPMC) (p < 0.05). We then corroborate these findings using an ex vivo PM model and show that MA also significantly enhances the ability of GC cells to adhere to strips of human peritoneum (p < 0.05). Using a multiplex ELISA, we identify MIF and VEGF as consistently elevated across MA samples from GC patients (p < 0.05). We demonstrate that agents that block the effects of MIF or VEGF abrogate the ability of MA to stimulate the adhesion of GC cells to adhere to human peritoneum and promote both ex vivo and in vivo metastases.

CONCLUSION

Agents targeting MIF or VEGF may be relevant to the treatment or prevention of PM in GC patients.

Peritoneal Metastatic Cancer Stem Cells of Gastric Cancer with Partial Mesenchymal-Epithelial Transition and Enhanced Invasiveness in an Intraperitoneal Transplantation Model

Objectives

This preliminary study is aimed at enriching and isolating peritoneal metastatic cancer stem cells (pMCSCs) of gastric cancer and assessing their epithelial-mesenchymal transition (EMT) phenotype and invasiveness.

Methods

Cancer stem cells of human gastric cancer (CSC-hGC) were previously isolated and transfected with green fluorescent protein and luciferase genes to validate the mouse model of peritoneal metastasis established via transplantation. The first and second generations ([G1] and [G2], respectively) of pMCSCs were isolated from intraperitoneally transplanted CSC-hGC (pMCSC-tGC) by spherical culture. CSC and EMT-related markers and regulators in the two generations of intraperitoneally transplanted tumors were examined by immunohistochemistry, immunofluorescence staining, and quantitative PCR. Cell mobility was examined by a transwell assay.

Results

The nude mouse model of intraperitoneally transplanted CSC-hGC was successful in establishing sequential formation of peritoneal tumors and enrichment of pMCSCs. CD44 and CD54 were consistently expressed in the two generations of transplanted tumors. In vitro cell (migration) assays and immunocytofluorescence assays showed that in pMCSC-tGC^[G2], E-cad, Survivin, and Vimentin expression was stable; α-SMA expression was decreased; and OVOL2, GRHL2, and ZEB1 expression was increased. PCR analysis indicated that in pMCSC-tGC^[G2], the mRNA expression of E-cad, α-SMA, MMP9, MMP2, and Vimentin was downregulated, while that of ZEB1, OVOL2, and GRHL2 was upregulated. In vivo tumor (homing) assays and immunohistochemical assays demonstrated that in pMCSC-tGC^[G2], E-cad and Snail were upregulated, while α-SMA was downregulated. The numbers of migrated and invaded pMCSC-tGC^[G1] and pMCSC-tGC^[G2] were significantly higher than those of CSC-hGC in migration and invasion assays.

Conclusions

pMCSCs might be a specific subpopulation that can be sequentially enriched by intraperitoneal transplantation. pMCSCs exhibited a tendency towards partial mesenchymal-epithelial transition, enhancing their invasiveness during homing and the formation of peritoneal tumors. However, these preliminary findings require validation in further experiments.

Pressurized intraperitoneal aerosol chemotherapy and its effect on gastric-cancer-derived peritoneal metastases: an overview

This manuscript aspires to portray a review of the current literature focusing on manifest peritoneal metastasis (PM) derived from gastric cancer and its treatment options. Despite the development of chemotherapy and multimodal treatment options during the last decades, mortality remains high worldwide. After refreshing important epidemiological considerations, the molecular mechanisms currently accepted through which PM occurs are revised. Palliative chemotherapy is the only recommended treatment option for patients with PM of gastric cancer according to the National Comprehensive Cancer Network guidelines, although cytoreductive surgery in combination with hyperthermic intraperitoneal chemotherapy demonstrated promising results in selected patients with regional PM and localized intraabdominal tumor spread. A novel treatment named pressurized intraperitoneal aerosol chemotherapy may have a promising future in improving overall survival with an acceptable postoperative complication rate and stabilizing quality of life during treatment. Additionally, the procedure has been proved to be safe for the patient and medical personnel and a feasible, repeatable method to deter metastatic proliferation. This overview comprehensively addresses this novel and promising treatment in the context of a scientifically and clinically challenging disease.

Exosome-mediated extracellular release of polyadenylate-binding protein 1 in human metastatic duodenal cancer cells

Exosomes are small vesicles secreted from cells that transport their embedded molecules through bidirectional exocytosis- and endocytosis-like pathways. Expression patterns of exosomal molecules such as proteins and RNAs can be indicative of cell type since their signature is thought to be unique among cells. Using human primary (AZ-521) and metastatic (AZ-P7a) duodenal cancer cell lines, we conducted a comparative exosomal proteome analysis to identify proteins with metastatic marker potential. As determined by LC-MS/MS and Western blot analyses, polyadenylate-binding protein 1 (PABP1) was found to be predominantly abundant in AZ-P7a exosomes. The amount of exosomal PABP1 in AZ-P7a cells increased by treating the cells with inhibitors for the classical ER/Golgi secretory pathway (brefeldin A and monensin) and the ubiquitin-proteasome pathway (MG-132 and PYR-41). Treatment of AZ-P7a cells with the neutral sphingomyelinase inhibitor GW4869, which suppresses exosome release, not only reduced the amount of exosomal PABP1 but also produced PABP1-immunoreactive products cleaved via a proteolysis-like process. Taken together, these results suggest that AZ-P7a cells do not tolerate intracellular PABP1 accumulation and are thus exported into the extracellular milieu by the exosome-mediated pathway. In addition, PABP1 has a potential use as a biomarker for metastatic duodenal cancer.

A true orthotopic gastric cancer murine model using electrocoagulation

BACKGROUND

Orthotopic mouse models of human gastric cancer represent an important in vivo tool for testing chemotherapeutic agents and for studying intraluminal factors. Currently, orthotopic mouse models of gastric cancer require an operative procedure involving either injection or implantation of tumor cells in stomach layers. The resultant tumor does not grow from the stomach's mucosal surface, so it does not mimic the human disease process.

STUDY DESIGN

A low-dose gastric mucosal coagulation was done transorally in the body of stomach using a specially designed polyethylene catheter in 16 female severe combined immunodeficient mice. This was followed by the instillation of SNU-16 human gastric cancer tumor cells (1 × 10(6) cells). Five mice each were euthanized at 1 and 2 months, and 6 mice were euthanized at 3 months. Three control mice underwent electrocoagulation alone and 3 mice underwent cell line instillation alone.

RESULTS

Tumors were detected in 11 of 16 experimental mice, but not in the control mice. Tumors were noted in mice at 1 month. Over time, there was an increase in tumor growth and metastasis to lymph nodes and surrounding organs. Histopathologic evaluation showed that the tumors grew from the gastric mucosa.

CONCLUSIONS

Our model is easy to create and overcomes the limitations of the existing models, as the tumor arises from the stomach's mucosal layer and mimics the human disease in terms of morphology and biologic behavior. This is the first report of a true orthotopic gastric cancer murine model. This model opens new doors for additional studies that were not possible earlier.

Animal models of gastric cancer

Gastric cancer is the second most common cause of cancer-related mortality (9.7% of the total) worldwide. Gastric carcinogenesis is a multiple-step process that involves multiple factors, such as bacteria, immune response and host factors. Animal models play a crucial role in the research of the biological behavior, diagnosis and treatment of gastric cancer. In this article we will review current advances in the development of animal models of gastric cancer in terms of microorganism-induced models, chemical carcinogen-induced models, tumor cell implantation, genetically modified models and in silico models.

Prognostic factors and oncologic outcome in 146 patients with colorectal peritoneal carcinomatosis treated with cytoreductive surgery combined with hyperthermic intraperitoneal chemotherapy: Italian multicenter study S.I.T.I.L.O

AIM

The present study was specifically designed to assess the major clinical and pathological variables of patients with colorectal peritoneal carcinomatosis in order to investigate whether currently used criteria appropriately select candidates for peritonectomy procedures (cytoreductive surgery) combined with hyperthermic intraperitoneal chemotherapy (HIPEC).

PATIENTS AND METHODS

Preoperative, operative and follow-up data on 146 consecutive patients presenting with peritoneal carcinomatosis of colorectal origin and treated by surgical cytoreduction combined with HIPEC in 5 Italian Hospital and University Centers were prospectively entered in a common database. Univariate and multivariate analyses were used to assess the prognostic value of clinical and pathologic factors.

RESULTS

Over a minimum 24-month follow-up, the overall morbidity rate was 27.4% (mortality rate: 2.7%) and was directly related to the extent of surgery. Peritoneal cancer index (PCI), unfavorable peritoneal sites, synchronous or previously resected liver metastasis and the completeness of cytoreduction, all emerged as independent prognostic factors correlated with survival.

CONCLUSIONS

Until research provides more effective criteria for selecting patients based upon the biomolecular features of carcinomatosis, patients should be selected according to the existing independent prognostic variables.

Let-7 microRNA family is selectively secreted into the extracellular environment via exosomes in a metastatic gastric cancer cell line

BACKGROUND

Exosomes play a major role in cell-to-cell communication, targeting cells to transfer exosomal molecules including proteins, mRNAs, and microRNAs (miRNAs) by an endocytosis-like pathway. miRNAs are small noncoding RNA molecules on average 22 nucleotides in length that regulate numerous biological processes including cancer pathogenesis and mediate gene down-regulation by targeting mRNAs to induce RNA degradation and/or interfering with translation. Recent reports imply that miRNAs can be stably detected in circulating plasma and serum since miRNAs are packaged by exosomes to be protected from RNA degradation. Thus, profiling exosomal miRNAs are in need to clarify intercellular signaling and discover a novel disease marker as well.

METHODOLOGY/PRINCIPAL FINDINGS

Exosomes were isolated from cultured cancer cell lines and their quality was validated by analyses of transmission electron microscopy and western blotting. One of the cell lines tested, a metastatic gastric cancer cell line, AZ-P7a, showed the highest RNA yield in the released exosomes and distinctive shape in morphology. In addition, RNAs were isolated from cells and culture media, and profiles of these three miRNA fractions were obtained using microarray analysis. By comparing signal intensities of microarray data and the following validation using RT-PCR analysis, we found that let-7 miRNA family was abundant in both the intracellular and extracellular fractions from AZ-P7a cells, while low metastatic AZ-521, the parental cell line of AZ-P7a, as well as other cancer cell lines showed no such propensity.

CONCLUSIONS/SIGNIFICANCE

The enrichment of let-7 miRNA family in the extracellular fractions, particularly, in the exosomes from AZ-P7a cells may reflect their oncogenic characteristics including tumorigenesis and metastasis. Since let-7 miRNAs generally play a tumor-suppressive role as targeting oncogenes such as RAS and HMGA2, our results suggest that AZ-P7a cells release let-7 miRNAs via exosomes into the extracellular environment to maintain their oncogenesis.

Allele polymorphisms of tumor integrins correlate with peritoneal carcinosis capability of gastric cancer cells in radically resected patients

BACKGROUND

Preclinical studies suggested that integrins are relevant for gastric cancer diffusion. We investigated integrins polymorphisms role in determining peritoneal carcinosis or hematogenous metastases in radically resected gastric cancer.

PATIENTS AND METHODS

Integrins genotyping was carried out on pT3 radically resected gastric tumors recurring with either peritoneal-only carcinosis or hematogenous metastases.

RESULTS

The following factors resulted independently associated with peritoneal carcinosis or hematogenous metastases: the A genotype of rs2269772 (ITGA3) [odds ratio (OR) for peritoneal carcinosis: 22.2, 95% confidence interval 1.2-40, P=0.03], the G genotype of rs2269772 (ITGA3) (OR for hematogenous metastases: 5.5, 95% confidence interval 2.2-14.15, P=0.0003), the C genotype of rs11902171 (ITGV) (OR for peritoneal carcinosis: 6.8, 95% confidence interval 1.3-33.4, P=0.01), the G genotype of rs11902171 (ITGV) (OR for hematogenous metastases: 2.5, 95% confidence interval 1.1-5.7, P = 0.02), diffuse histology (OR for peritoneal carcinosis: 4.7, 95% confidence interval 1.9-11.3, P=0.0005) and intestinal histology (OR for hematogenous metastases: 4.2, 95% confidence interval 1.9-9.9, P=0.0008).

CONCLUSIONS

Tumor histology represents a crucial issue conditioning tumoral behavior; genotyping of rs2269772 (ITGA3) and rs11902171 (ITGV) may be a further asset in the definition of high-risk patients for peritoneal carcinosis among those relapsing after curative resection. The selection tool deriving from this analysis may allow an optimal use of innovative treatment strategies.

OB glue paste technique for establishing nude mouse human gastric cancer orthotopic transplantation models

AIM: To establish nude mouse human gastric cancer orthotopic transplantation models using OB glue paste technique.

METHODS: Using OB glue paste technique, orthotopic transplantation models were established by implanting SGC-7901 and MKN-45 human gastric cancer cell strains into the gastric wall of nude mice. Biological features, growth of the implanted tumors, the success rate of transplantation and the rate of auto-metastasis of the two models were observed.

RESULTS: The success rates of orthotopic transplan-tation of the two models were 94.20% and 96%. The rates of hepatic metastasis, pulmonary metastasis, peritoneal metastasis, lymphocytic metastasis and splenic metastasis were 42.13% and 94.20%, 48.43% and 57.97%, 30.83% and 36.96%, 67.30% and 84.06%, and 59.75% and 10.53%, respectively. The occurrence of ascites was 47.80% and 36.96%.

CONCLUSION: OB glue paste technique is easy to follow. The biological behaviors of the nude mouse human gastric cancer orthotopic transplantation models established with this technique are similar to the natural processes of growth and metastasis of human gastric cancer, and, therefore, can be used as an ideal model for experimental research of proliferative metastasis of tumors.

Inhibitory effect of endothelin A receptor blockade on tumor growth and liver metastasis of a human gastric cancer cell line

BACKGROUND

With metastatic progression, gastric cancer is incurable. Using a DNA microarray, we performed differential gene expression analysis of established highly metastatic gastric cancer cell lines and compared the findings with those from a low-metastatic parental cell line. The results demonstrated that the endothelin A receptor (ET-A) gene was the only one from the highly metastatic cell lines that was generally up-regulated.

METHODS

To investigate the role that ET-A plays in gastric cancer metastasis, we studied the effect of an ET-A-selective antagonist, YM598, on cell proliferation, tumor growth, and liver metastasis of the highly liver metastatic cell line AZ-H5c, established from the low metastatic human gastric cancer cell line AZ-521.

RESULTS

An in vivo study using nude mice demonstrated that YM598 had a significant growth inhibition effect on AZ-H5c at doses of 0.5-10.0 mg/kg. The liver metastatic rate was also significantly reduced by YM598: control, 83.3%; 1 mg/kg dosage, 16.7%; 10 mg/kg, 20%; and pretreatment at 1 mg/kg, 16.7%. There was no evidence of gross toxicity resulting from the YM598 treatment.

CONCLUSION

The ET-A blockade by YM598 had a strong inhibitory effect against tumor growth and liver metastasis of the gastric cancer cell lines. These data suggest that YM598 has potential as a novel therapeutic agent for inhibiting liver metastasis of gastric cancer.

Treatment of peritoneal carcinomatosis by cytoreductive surgery and intraperitoneal hyperthermic chemoperfusion (IHCP): postoperative outcome and risk factors for morbidity

BACKGROUND

Cytoreductive surgery with limited or extended peritonectomy associated with intraperitoneal hyperthermic chemoperfusion (IHCP) has been proposed for treatment of peritoneal carcinomatosis (PC) from abdominal neoplasms.

METHODS

Fifty-nine patients with PC from abdominal neoplasms underwent 61 treatments using this technique from January 2000 to August 2005. Surgical debulking, completed by partial or total peritonectomy, was performed in most cases. In 16 patients with positive peritoneal cytology without macroscopic peritoneal disease, IHCP was performed in order to prevent peritoneal recurrence. IHCP was carried out throughout the abdominopelvic cavity for 60 minutes using a closed abdomen technique. Intra-abdominal temperature ranged between 41 degrees C and 43 degrees C; mitomycin C (25 mg/mq) and cisplatin (100 mg/mq) were the anticancer drugs generally used, and they were administered with a flow rate of 700-800 ml/minute.

RESULTS

Mean hospital stay was 13 +/- 7 (range 7-49) days. Postoperative complications occurred in 27 patients (44.3%); of these, major morbidity was observed in 17 (27.9%). The most frequent complications were wound infection (9 cases), grade 2 or greater hematological toxicity (5 cases), intestinal fistula (5 cases), and pleural effusion requiring drainage (5 cases). Reoperation was necessary in 5 patients (8.2%). One patient with multiorgan failure died in the postoperative period (mortality rate: 1.6%). Multivariate analysis of several variables identified completeness of cancer resection (CCR-2/3 vs. CCR-0/1, relative risk: 9.27) and age (relative risk: 1.06 per year) as independent predictors of postoperative morbidity. Preliminary follow-up data indicate that survival probability may be high in patients with ovarian or colorectal cancer and low in patients with gastric cancer.

CONCLUSIONS

IHCP combined with cytoreductive surgery involves a high risk of morbidity, but postoperative complications could be resolved favorably in most cases with correct patient selection and adequate postoperative care. Tumor residual and advanced age significantly increase the risk of morbidity after this procedure.

Treatment of peritoneal carcinomatosis by cytoreductive surgery and intraperitoneal hyperthermic chemoperfusion (IHCP): postoperative outcome and risk factors for morbidity

BACKGROUND

Cytoreductive surgery with limited or extended peritonectomy associated with intraperitoneal hyperthermic chemoperfusion (IHCP) has been proposed for treatment of peritoneal carcinomatosis (PC) from abdominal neoplasms.

METHODS

Fifty-nine patients with PC from abdominal neoplasms underwent 61 treatments using this technique from January 2000 to August 2005. Surgical debulking, completed by partial or total peritonectomy, was performed in most cases. In 16 patients with positive peritoneal cytology without macroscopic peritoneal disease, IHCP was performed in order to prevent peritoneal recurrence. IHCP was carried out throughout the abdominopelvic cavity for 60 minutes using a closed abdomen technique. Intra-abdominal temperature ranged between 41 degrees C and 43 degrees C; mitomycin C (25 mg/mq) and cisplatin (100 mg/mq) were the anticancer drugs generally used, and they were administered with a flow rate of 700-800 ml/minute.

RESULTS

Mean hospital stay was 13 +/- 7 (range 7-49) days. Postoperative complications occurred in 27 patients (44.3%); of these, major morbidity was observed in 17 (27.9%). The most frequent complications were wound infection (9 cases), grade 2 or greater hematological toxicity (5 cases), intestinal fistula (5 cases), and pleural effusion requiring drainage (5 cases). Reoperation was necessary in 5 patients (8.2%). One patient with multiorgan failure died in the postoperative period (mortality rate: 1.6%). Multivariate analysis of several variables identified completeness of cancer resection (CCR-2/3 vs. CCR-0/1, relative risk: 9.27) and age (relative risk: 1.06 per year) as independent predictors of postoperative morbidity. Preliminary follow-up data indicate that survival probability may be high in patients with ovarian or colorectal cancer and low in patients with gastric cancer.

CONCLUSIONS

IHCP combined with cytoreductive surgery involves a high risk of morbidity, but postoperative complications could be resolved favorably in most cases with correct patient selection and adequate postoperative care. Tumor residual and advanced age significantly increase the risk of morbidity after this procedure.

Identification of oligopeptides binding to peritoneal tumors of gastric cancer

This is a report of in vivo intraperitoneal biopanning, and we successfully identified a novel peptide to target the multiple peritoneal tumors of gastric cancer. A phage display library was injected directly into the abdominal cavity of mice bearing peritoneal tumors of human gastric cancer, and phages associated with the tumors were subsequently reclaimed from isolated samples. The tumor-associated phages were amplified and the biopanning cycle was repeated five times to enrich for high affinity tumor-selective binding peptides. Finally, a tri-peptide motif, KLP, which showed homology with laminin 5 (a ligand for alpha3beta1 integrin), was identified as a binding peptide for peritoneal tumors of gastric cancer. Phage clones displaying the sequence KLP showed 64-fold higher binding to peritoneal tumors than control phage and were preferentially distributed in tumors rather than in normal organs after intraperitoneal injection into mice. In addition, the KLP phages were more likely to bind to cancer cells in malignant ascites derived from a patient with recurrent gastric cancer. Synthesized peptide containing the motif KLP (SWKLPPS) also showed a strong binding activity to peritoneal tumors without cancer growth effect. Liposomes conjugated with SWKLPPS peptide appeared significantly more often in tumors than control liposomes after intraperitoneal injection into mice. Furthermore, modification of liposomes with SWKLPPS peptide enhanced the antitumor activity of adriamycin on gastric cancer cells. The peptide motif KLP seems a potential targeting ligand for the treatment of peritoneal metastasis of gastric cancer.

Prediction of recurrence after radical surgery for gastric cancer: a scoring system obtained from a prospective multicenter study

OBJECTIVE

The aim of this prospective multicenter study was to define a scoring system for the prediction of tumor recurrence after potentially curative surgery for gastric cancer.

SUMMARY BACKGROUND DATA

The estimation of the risk of recurrence in individual patient may be relevant in clinical practice, to apply adjuvant therapies after surgery, and plan an adequate follow-up program. Only a few studies, most of which were retrospective or performed on a limited number of patients, have developed a prognostic score in patients with gastric cancer.

METHODS

A total of 536 patients who underwent UICC R0 resection between 1988 and 1998 at 3 surgical departments in Italy were considered. All patients were followed up using a standard protocol after discharge from the hospital. The mean follow-up period was 56 +/- 44 months, and 94 +/- 29 months for surviving patients. The scoring system was calculated on the basis of a logistic regression model, where the presence of the recurrence was the dependent variable, and clinicopathologic variables were the covariates.

RESULTS

Recurrence occurred in 272 of 536 patients (50.7%). The scoring system for the prediction of the risk in individual cases gave values ranging from 1.4 to 99.9; the model distributed most cases in the extremes of the range. The risk of recurrence increased remarkably with score values; it was only 5% in patients with a score below 10, up to 95.4% in patients with a score of 91 to 100. No recurrence was observed in 43 patients with a score below 4, whereas all of the 56 patients with a score over 97 presented a recurrence. The model correctly predicted recurrence in 227 of 272 patients (sensitivity, 83.5%), whereas the absence of recurrence was correctly predicted in 214 of 264 patients (specificity, 81.1%); the overall accuracy was 82.2%. Prognostic score was clearly superior to UICC tumor stage in predicting recurrence. The high effectiveness of the score was confirmed in preliminary data of a validation study.

CONCLUSIONS

The scoring system obtained with a regression model on the basis of our follow-up data is useful for defining subgroups of patients at a very low or very high risk of tumor recurrence after radical surgery for gastric cancer. Final results of the validation study are essential for a clinical application of the model.

Prospective study of peritoneal recurrence after curative surgery for gastric cancer

BACKGROUND

Peritoneal carcinomatosis is a common cause of failure after surgery for gastric cancer. The present longitudinal study was designed to evaluate the incidence and potential predictors of peritoneal recurrence after curative resection for gastric cancer.

METHODS

Four hundred and forty-one patients who underwent potentially curative resections for gastric cancer in three surgical centres between 1988 and 1996 were evaluated. All patients were followed using a standard protocol following discharge from hospital. The correlation between tumour recurrence and clinicopathological variables was studied by univariate and multivariate analyses.

RESULTS

Gastric cancer recurred in 215 (49 per cent) of 441 patients. Peritoneal recurrence was observed in 77 patients (17 per cent), locoregional recurrence in 96 patients and haematogenous recurrence in 75. Multivariate logistic regression analysis of factors associated with peritoneal recurrence identified diffuse-mixed histological type (relative risk (RR) 4.31, P < 0.001), infiltration of the serosa (RR 3.36, P = 0.001), lymph node involvement (RR 2.67, P = 0.023) and tumour size (RR 1.11, P = 0.050) as significant independent variables. In the diffuse-mixed histological subtype, the 5-year cumulative risk of peritoneal recurrence was 12 per cent in the absence of serosal invasion, and 69 per cent in patients with infiltration of the serosa; in the intestinal subtype, the cumulative risk in patients with serosa-negative and -positive tumours was 4 and 21 per cent respectively.

CONCLUSION

Radical surgery offers a low probability of cure in patients with diffuse-mixed type of gastric cancer and involvement of the serosa, due to a high risk of peritoneal recurrence. These patients might benefit from adjuvant therapies to prevent peritoneal carcinomatosis.

A new liver metastatic and peritoneal dissemination model established from the same human pancreatic cancer cell line: analysis using cDNA macroarray

To elucidate the mechanisms of metastasis, we established two sublines HPC-1H5 with a highly liver metastatic cell line and HPC-1P5a with a highly peritoneal disseminating cell line, which were sequentially selected from the parental pancreatic cancer cell line HPC-1. Using these three cell lines, we investigated several biological properties and mRNA levels of differentially-expressed genes involved in cancer metastasis by cDNA macroarray. Microscopic findings for the three cell lines were the same. The tumorigenicity, in vitro growth ability, motile activity, adhesive activity and the production of IL-8 of metastatic sublines were higher than those of parental HPC-1 cells. Particularly, HPC-1H5 cells showed clearly higher levels of IL-8 expression and tumors of HPC-1H5 cells grew faster and bigger than those of HPC-1P5a cells. In cDNA macroarray analysis of HPC-1H5 cells, 22 genes were up-regulated and 44 genes were down-regulated compared with parental HPC-1 cells. In HPC-1P5a cells, 9 genes were up-regulated and 28 genes were down-regulated compared with parental HPC-1 cells. This study provides a demonstration of global gene expression analysis of pancreatic cancer cells with liver metastasis and peritoneal dissemination. Furthermore, our results provide a new insight into the study of liver metastasis and peritoneal dissemination of human pancreatic cancer.

A novel nude mouse model of liver metastasis and peritoneal dissemination from the same human pancreatic cancer line

INTRODUCTION

Recently, several mice models have been used for investigating cancer metastasis. However, there are no metastatic and peritoneal dominated variants from the same parental cell line.

AIM AND METHODOLOGY

To elucidate the mechanisms of metastasis, we established highly liver metastatic and peritoneal disseminated models in nude mice, and then characterized several factors related to metastasis in these cells. We established a series of well-characterized sublines that showed metastatic potentials to different organ sites of nude mice. Two sublines were selected sequentially from the parental pancreatic cancer cell line, HPC-4, resulting in a highly liver metastatic cell line, HPC-4H4, and a highly peritoneal disseminated cell line, HPC-4P4a. Using these three cell lines, we investigated several biologic properties and mRNA levels of differentially expressed genes involved in cancer metastasis.

RESULTS

The tumorigenicity, the motile activity, and the adhesive activity of metastatic sublines were higher than those of parental HPC-4 cells. Macroscopic and microscopic findings and the DNA ploidy pattern were the same among the three cell lines. In addition, HPC-4H4 cells expressed clearly higher levels of vascular endothelial growth factor and IL-8 expression than did HPC-4P4a cells. In fluorescence-activated cell sorter analysis of adhesion molecules, the expression of integrin-alpha2 was enhanced in HPC-4 cells, integrin-alphavbeta5 was enhanced in HPC-4H4 cells, and integrin-alpha3 was enhanced in HPC-4P4a cells. Osteopontin, vascular endothelial growth factor, and hepatocyte growth factor were among the genes that were upregulated in HPC-4H4 cells compared with HPC-4P4a cells. HPC-4P4a cells did not metastasize to the liver by intrasplenic injection. Conversely, HPC-4H4 cells metastasized remarkably to the peritoneum by intraabdominal injection.

CONCLUSION

These sublines are the first reported liver metastatic and peritoneal disseminated models derived from the same parental cell lines. The results of our study suggest that the process of hematogenous metastasis is not the same as that of peritoneal dissemination.

A novel experimental mouse model of peritoneal dissemination of human gastric cancer cells: analysis of the mechanism of peritoneal dissemination using cDNA macroarrays

We established a new cell line, NUGC-3P4T, with high peritoneal metastatic disseminating potential in nude mice. NUGC-3P4T cells were derived from the human gastric carcinoma line NUGC-3, which has low capacity for peritoneal dissemination. NUGC-3P4T cells developed peritoneal dissemination in 10 / 10 (100%) mice, whereas the parental NUGC-3 cells developed dissemination in 1 / 5 (20.0%) mice. The metastatic foci in the peritoneum showed essentially the same histological appearance as those induced by parental cells. The tumorigenicity, the motile activity and the adhesive activity to the laminin of NUGC-3P4T cells were stronger than those of NUGC-3 cells. Production of IL-8 was significantly higher in NUGC-3P4T than in NUGC-3. cDNA macroarrays analysis showed that a variety of cytokines, interleukins, and other immunomodulators and their receptors were up- or down-regulated at the mRNA level in NUGC-3P4T cells, compared with NUGC-3 cells. Thus, this unique cell line and in vivo model might be useful to study the biology of peritoneal dissemination of human gastric cancer.