Expression of cyclooxygenase-2 in human gastric adenomas and adenocarcinomas.

BACKGROUND AND OBJECTIVES: The increased expression of cyclooxygenase (COX)-2 has been implicated in the development and progression of colorectal cancer. We sought to determine the involvement of COX-2 in human gastric cancer. MATERIALS AND METHODS: COX-2 mRNA was assayed in both gastric cancer cell lines and biopsy specimens from 37 gastric adenocarcinomas, five gastric adenomas, and five hyperplastic polyps by reverse transcription-polymerase chain reaction. RESULTS: COX-2 mRNA was found in four of five gastric cancer cell lines, two from intestinal type and two from diffuse type. COX-2 mRNA was expressed in 19 of 37 (51%) human gastric cancer specimens. The tumor diameter was greater in patients with COX-2 expression than in those without (6.5 +/- 4.6 vs. 3.8 +/- 2.7 cm, P < 0.05). The incidence of COX-2 mRNA expression was significantly higher in patients with pT2-pT4 tumors than in those with pT1 tumors (71 vs. 35%, P < 0.05). Significantly higher expression of COX-2 mRNA was also observed in patients with lymph node involvement than in those without (75 vs. 40%, P < 0.05). COX-2 mRNA was found in one of five adenomas, while it was absent in five hyperplastic polyps. The paired normal gastric musosa did not express COX-2 mRNA in any of the 47 patients. CONCLUSIONS: These results provide clinical evidence that COX-2 may contribute to tumor progression in human gastric adenocarcinoma.

Cyclooxygenase-2 expression is related to prostaglandin biosynthesis and angiogenesis in human gastric cancer.

Although recent studies have demonstrated that cyclooxygenase (COX)-2 is overexpressed in various cancers including gastric cancer, the mechanisms underlying the contribution of COX-2 to tumorigenesis and tumor promotion still remain unclear. To determine the role of COX-2, we investigated the COX-2 expression, the prostaglandin (PG) levels, and the microvessel density in 42 patients with primary gastric adenocarcinoma. COX-2 protein was over-expressed in 31 (74%) of 42 gastric cancers based on an immunoblot analysis. The intensity of COX-2 expression was found to significantly correlate with lymph node involvement. The COX-2 overexpressed cases showed significantly elevated levels of prostaglandin E2 (PGE2) in cancer tissues in comparison with the normal gastric mucosa by an immunoassay (201 +/- 90 versus 161 +/- 57 ng/mg protein; P < 0.05). However, the COX-2 overexpression was not related to the levels of thromboxane B2 and 6-keto-prostaglandin F1alpha. The density of microvessel immunostained with CD34 was significantly higher in patients demonstrating COX-2 overexpression than in those without such expression (63 +/-21 versus 45 +/- 17/200 x; P < 0.01). Our data thus suggested COX-2 overexpression to be associated with increased PGE2 biosynthesis and angiogenesis in gastric cancer, which indicates that COX-2 may play a role in the development of gastric cancer.

Induction of apoptosis by JTE-522, a specific cyclooxygenase-2 inhibitor, in human gastric cancer cell lines.

An increased expression of cyclooxygenase (COX)-2 has been observed in various cancers including gastric cancer. Although specific COX-2 inhibitors have a chemopreventive effect on colon cancer, their molecular mechanisms remain unclear. To clarify these mechanisms, we investigated the effects of JTE-522, a newly developed COX-2-specific inhibitor, on gastric cancer cell lines (MKN28 and MKN45). The baseline levels of COX-2 expression were higher in MKN45 than in MKN28. JTE-522 obviously suppressed the levels of COX-2 mRNA, COX-2 protein and PGE2 at a dose of 250 microM in both cancer cells. Apoptosis was induced at 24 hours after treatment with JTE-522 (250 microM) in both cancer cells. To determine the mechanisms of apoptosis induction by JTE-522, the time course of the cell cycle and the apoptosis-related protein levels were examined. An increase in the G1 phase and a decrease in the S phase were observed prior to apoptosis. Moreover, an increase of c-myc protein and a decrease of bcl-2 protein were observed in both cells treated with JTE-522. These findings suggested that JTE-522 could induce apoptosis by blocking the cell cycle, enhancing c-myc expression and diminishing bcl-2 expression. JTE-522 also suppressed proliferation activity in both cell lines. These effects of JTE-522 were more dramatic in MKN45 than in MKN28. Since JTE-522 strongly suppresses cell growth by inducing apoptosis in gastric cancer cell lines, it may therefore serve as a chemopreventive agent.

Evaluation of the New American Joint Committee on Cancer/International Union against cancer classification of lymph node metastasis from gastric carcinoma in comparison with the Japanese classification.

BACKGROUND: A new system for the classification of gastric carcinoma, based on the number of metastatic lymph nodes, has been adopted by the current American Joint Committee on Cancer/International Union Against Cancer (AJCC/UICC) TNM system (1997). The purpose of this study was to evaluate the rationality of this classification in comparison with the Japanese classification, which is based on the location of positive lymph nodes. METHODS: The authors analyzed 587 patients who underwent clinically curative gastrectomy with D2 lymphadenectomy for gastric carcinoma and each had 15 or more lymph nodes histologically examined from 1982 to 1992. Multivariate analysis with the Cox proportional hazards model was carried out to determine which classification was more effective. RESULTS: Within the pN1 or pN2 category of the new AJCC/UICC system, no significant difference in the survival rates existed between n1 patients and n2 patients of the Japanese classification. On the other hand, the survival rates significantly decreased, in the order of pN1, pN2, and pN3 (from greatest to smallest decrease), within the n1 and n2 categories. In multivariate analysis, lymph node involvement by the AJCC/UICC classification was selected as the most significant prognostic determinant, whereas the Japanese lymph node classification was not significantly prognostic. When survival rates were calculated within the pT1, pT2, and pT3-4 categories, no differences existed between pN0 and pN1. There was some discrepancy between the survival rate for each pT and pN category and the corresponding stage. CONCLUSIONS: The new AJCC/UICC classification for lymph node involvement of gastric carcinoma is basically acceptable and considered superior to the Japanese classification. Further analysis involving a greater number of cases may be necessary to confirm the applicability of this staging system.

Expression of cyclooxygenase-2 protein in gastric adenocarcinoma.

BACKGROUND AND OBJECTIVES: Epidemiological studies have suggested that the regular use of nonsteroidal antiinflammatory drugs, which inhibit cyclooxygenase (COX), reduces the risk of colon cancer. The inducible COX-2 isoform has been reported to be upregulated in colorectal carcinomas and may play a role in colorectal carcinogenesis. The purpose of this study was to investigate the expression of COX-2 protein in human gastric adenocarcinomas. METHODS: COX-2 protein expression was examined in 23 patients with gastric adenocarcinoma by immunoblotting and immunohistochemistry. RESULTS: There was an increase in COX-2 protein levels in 19 of the 23 carcinomas (83%) compared with the paired normal gastric mucosa by an immunoblot analysis. There was no correlation between tumor histology and COX-2 protein expression. An immunohistochemical study in the 19 cases showed diffuse COX-2 staining in the cytoplasm of cancer cells. Mononuclear cells or fibroblasts of the cancer stroma were not stained with COX-2. Sporadic staining for COX-2 was observed in the normal fundic or metaplastic glandular cells in all cases. CONCLUSIONS: COX-2 protein expression was elevated in most human gastric adenocarcinomas in comparison to the normal mucosa. COX-2 may therefore play an important role in gastric carcinogenesis.

Thymidylate synthase inhibition by an oral regimen consisting of tegafur-uracil (UFT) and low-dose leucovorin for patients with gastric cancer.

PURPOSE: 5-Fluorouracil (5-FU) remains a standard therapy for patients with advanced gastric cancer. There has been no study using an oral regimen with a combination of tegafur, a masked compound of 5-FU, and leucovorin in gastric cancer. The purpose of this study was to determine whether orally administered low-dose leucovorin enhances thymidylate synthase (TS) inhibition when added to tegafur-uracil (UFT) in patients with gastric cancer. METHODS: A group of 26 patients with resectable gastric cancer were assigned to one of two regimens: UFT alone or UFT plus leucovorin. UFT, equivalent to 400 mg/day tegafur, with or without 30 mg/day leucovorin, was administered orally in divided daily doses every 12 h for 3 consecutive days prior to surgery. Tumor specimens were taken immediately following gastrectomy, and the TS inhibition rate (TSIR) was determined using a ligand-binding assay. RESULTS: The TSIR was significantly higher in the UFT plus leucovorin group than in the UFT alone group (P < 0.01). The TSIR in the patients treated with UFT alone ranged between 14% and 50%, while six of the eight patients treated with UFT plus leucovorin had a TSIR of 55% or higher. The remaining two patients in the group treated with UFT plus leucovorin, with a TSIR of 31% and 44%, had undifferentiated tumors. CONCLUSION: Our results suggest that orally administered low-dose leucovorin can add to the efficacy of UFT in patients with gastric cancer, and provide preliminary data for a randomized clinical trial.

Clinical and prognostic characteristics of papillary clear carcinoma of stomach.

Papillary clear carcinoma (PCC), a variant of gastric papillary adenocarcinoma, demonstrates the histologic features of cancer cells with clear cytoplasm and no nuclear polarity, resembling the primitive gut epithelium of the fetus. To clarify the clinical and prognostic characteristics of PCC, we examined operative specimens from 73 patients with gastric papillary adenocarcinoma. Light microscopic examination of hematoxylin and eosin (H&E) stained sections of specimens from 15 patients revealed the features of PCC. The patients with PCC demonstrated a higher incidence of Type 3 gross appearance, tumor invasion into the muscularis propria or beyond, involvement of distal lymph nodes, liver metastasis, elevated serum AFP concentrations, and palliative resections. In two subsets of patients who underwent curative resections of tumors invading the muscularis propria or beyond, those with PCC were found to have a significantly lower survival rate than those with other types of papillary adenocarcinoma (P < 0.05). PCC histology was a significant prognostic determinant according to multivariate analysis with the Cox proportional hazards model. We conclude that this subclassification of papillary adenocarcinoma, based on the cellular findings, is a useful prognostic indicator, and that intensive adjuvant therapy may be indicated for patients with the features of PCC, even if they have undergone curative resections.

Surgical strategy for patients with gastric carcinoma with submucosal invasion. A multivariate analysis.

BACKGROUND: Early gastric cancer can be treated by endoscopic excision or simple wedge surgical resection. Standard gastrectomy often is advised if submucosal invasion is found, even though only 15-25% of these patients have lymph node metastases. In this study, the risk of lymph node involvement was examined by multivariate analysis to develop a simple discriminant function for surgical decision making in this setting. METHODS: The authors determined factors significantly correlated with lymph node involvement in a retrospective review of 196 patients with gastric adenocarcinoma invading into, but not beyond, the submucosa. Depth and horizontal spread of cancer in the submucosa were evaluated in addition to ordinary pathologic factors. Discriminant analysis for lymph node involvement was performed using explanatory variables chosen from the results of the univariate analyses. RESULTS: Lymph node involvement correlated significantly with larger tumor size; greater dimension of submucosal invasion; deeper submucosal invasion; gross appearance of Type I, IIc + III or IIa + IIc; and severity of vessel invasion. Of the variables, the amount of lymphatic invasion, macroscopic appearance, and maximum dimension of submucosal infiltration were selected as effective predictors of lymph node involvement according to discriminant analysis. A correct discrimination of 74.8% was obtained with a linear discriminant function using these variables. Lymph node involvement was observed in 50% of the cases with a discriminant score less than -1 and in 25% of those with a score between -1 and 0, whereas no lymph node involvement was observed in those with a score greater than 2. CONCLUSIONS: Discriminant function as used in this study provided a useful criterion for additional surgery for patients with gastric carcinoma invading the submucosa who were treated initially by localized excision. Prophylactic lymph node dissection may not be necessary for a discriminant score greater than 2, whereas extended lymphadenectomy would be recommended for a score less than -1.

Roles of histological findings and serum AFP levels in the prognosis of AFP-producing gastric cancers.

We investigated the roles of histological findings and serum AFP levels in the prognosis of gastric cancers which produce AFP. We considered the typical features of such gastric cancers to be the medullary growth of undifferentiated cancer cells with clear, or slightly eosinophilic, abundant cytoplasm and pleomorphic large round nuclei, forming either papillary clear carcinomas or hepatoid carcinomas. Seventeen patients with AFP-producing gastric cancers were observed in the period, 1979-1991. They were divided into two groups: those with (n 5) and those without (n 12) the typical histological features mentioned above. Their clinicopathological findings and prognoses were compared. Both groups showed a male dominance, gross Borrmann's type 2 or 3 appearances, diagnoses made at an advanced stage and metastatic involvements of the liver. The patients with the typical histological features showed a significantly higher AFP serum level and a significantly shorter survival. The patients who lacked the typical findings, and with serum AFP levels > or = 100 ng/ml, had poorer prognoses, while those lacking the typical histological features, and serum AFP levels < 100 ng/ml had better prognoses. The combination of histological findings and serum AFP level appeared to be useful in predicting the prognosis of AFP-producing gastric cancers. Intensive adjuvant therapy, e.g., chemotherapy administered via hepatic arterial infusion, may be indicated for patients at a high risk of recurrence following curative surgery.

Comparison of the prognostic significance between the number of metastatic lymph nodes and nodal stage based on their location in patients with gastric cancer.

PURPOSE: To determine which is the better prognostic determinant in gastric cancer: number of positive metastatic lymph nodes or current nodal stage. PATIENTS AND METHODS: Seven hundred seventy-seven patients who underwent potentially curative resections for gastric cancer were divided into three groups according to the depth of invasion. The influence of the number of positive nodes on their survival rate was analyzed. A multivariate analysis by the Cox proportional hazards model was used to determine independent prognostic factors. RESULTS: A decreased survival rate was associated with an increased number of positive nodes in all of the subjects and in each of the three groups. Patients with one to three positive nodes had as good a prognosis as those without nodal involvement when each of the three groups was analyzed separately. Using a multivariate analysis in the patients with four or more positive nodes, we found that the number of positive nodes was the most important prognostic determinant (P < .0001), followed by the depth of invasion (P < .02), and that the nodal stage was not significantly prognostic. Further multivariate analysis in the patients with one to three positive nodes showed that nodal stage and number of positive nodes were not significantly prognostic. CONCLUSION: The number of metastatic nodes should be adopted for classification of nodal stage in gastric cancer.

Proposal of a risk score for recurrence in patients with curatively resected gastric cancer.

In this study, 168 patients who underwent curative resection for gastric cancer with prognostic serosal invasion [ps(+)] and 150 without prognostic serosal invasion [ps(-)] were analyzed separately to determine the prognostic importance of clinicopathological factors, and identify which patients were at high risk of recurrence. A multivariate analysis of survival time using Cox's proportional hazard model revealed the important prognostic factors to be: Lymph node involvement, the classification of gross appearance, macroscopic serosal invasion, and interstitial connective tissue in the ps(+) group; and lymph node involvement, macroscopic serosal invasion, and venous invasion in the ps(-) group. We proposed a risk score of recurrence based on the results of a further multivariate analysis called Hayashi's Quantification Analysis II, in which recurrence was chosen as an objective variable and the above prognostic factors were chosen as explanatory variables. Eighty-four percent of the patients with a score of 0 or higher in the ps(+) group and 83% of those with a score of +6 or higher in the ps(-) group showed recurrence. Thus, we believe that this score is useful for identifying those patients at high risk of recurrence, who should receive intensive chemotherapy even after curative resection.