E-钙粘附素在胃癌表达的临床意义
癌症 2000年第1期第19卷 临床研究
作者：张成武 徐文娟 赵仲生 邹寿椿
单位：张成武 徐文娟 赵仲生 邹寿椿（浙江省人民医院普外科，浙江杭州310014）
关键词：胃肿瘤；E-钙粘附素；预后；异型增生
摘 要：目的：探讨E-钙粘附素(E-CD)表达与胃癌发生发展及预后的关系。方法：采用SP免疫组化染色技术，检测20例正常胃粘膜上皮，43例异型增生和101例胃癌组织E-CD的表达情况。结果：正常胃粘膜和异型增生组织E-CD呈强阳性表达，88.1％(89/101)胃癌E-CD表达减弱，E-CD表达与胃癌分化差、浸润型生长显著相关(P＜0.05)，ECD表达正常的胃癌病人术后3、5年生存率显著高于减弱者(P均＜0.05)。结论：ECD减弱表达与胃癌细胞分化差、浸润型生长及预后较差密切相关。
分类号：R735.2 文献标识码：A
文章编号：1000－467X(2000)01－0057－04
Clinical significance of E-cadherin expression in gastric cancer
ZHANG Cheng-wu, XU Wen-juan, ZHAO Zhong-sheng, et al.
(Departmant of General Surgery,Zhejiang Provincial People s Hospital Hoangzhou 310014,P.R.China)
Abstract：Objective：To investigate the role of the expression of E-cadherin (E-CD) in carcinogenesis and progre-ssion of gastric cancer.Methods：The E-CD expression was studied immunohistochemistrically in 20 specimens of normal gastric mucosa, 101 Ro-resected gastric carcinomas and 43 of dysplasimucosa surrounding tumors. Results： The normal and dysplastic gastric mucosae strongly expressed E-CD, whereas 88.1％ (89/101) gastric cancers showed reduced or no expression of E-CD. The significant relationship was observed between low E-CD expression and cellular dedifferentiation and infiltrative groth pattern (P＜0.05). The 3 and 5-year survival rates of patients with normal E-CD expression were significantly higher than those of patients with reduced or negative expression (P＜ 0.05).Conclusion：The decreased expression of E-CD might be responsible for the cellular dedifferentiation, the infiltrative growth and poor prognosis of gastric carcinomas.
Key words：Gastric neoplasm; E-cadherin; Prognosis; Dysplasia ▲
Gastric cancer is one of the most frequent malignancies in China.Invasion and metastasis,the main causes of cancer therapeutic failure and patient death, are the greatest obstacles to increase survival rate of gastric cancer.Litea et al. considered that cellular adhesion,matrix proteolysis,and cell migration are the major three steps during the process of invasion and metastasis, and the initial step is the deattachment of cancer cells from the primary tumor[1]. It has been shown that a number of different steps in the complex metastatic process are associated with alterations in the adhesive properties of the tumor cells.E-cadherin, a calcium dependent cell adhesive molecule mediating homotypic adhesion between epithelial cells, plays an important role in establishing and maintaining intercellualr connections. Many previous reports have suggested that E-CD protein expression is decreased or even absent in various human primary carcinomas,and the reduced expression of E-CD has been significantly correlated with tumor invasion,metastasis and poor prognosis[2].
In the present study, we investigated the expression of E-CD in gastric cancer,using streptavidin-peroxidase immunohistochemistry, attem-pting to evaluate the role of E-CD in carcinogenesis, progression and the clinical value of E-CD expression for the prediction of prognosis.
1 MATERIALS AND METHODS
1.1 Tissue specimens
A total of 101 gastric carcinomous specimens came from consecutive patients which underwent potentially curative surgery for gastric cancer form June 1986 to December 1996. Control groups included 43 specimens of tgastric mucosa surrounding tumor tissues with dysplasia and 20 normal gastric mucosa specimens from peptic ulcer disease. All cases were verified by the operation and pathology.Tissues of all cases were fixed in buffered formalin and embedded in paraffin. Fourmicrometer-thick serial sections were prepared. Sections were stained with hemotoxylin-eosin for evaluation of pathological parameters,and with streptavidin-peroxidase technology using the murine monoclonal antibody against E-CD to detect the expression of E-CD.
1.2 Evaluation of clinicopathological parameters
Immunohistochemical results were compared with a variety of generally accepted prognostic parameters. The tumor growth pattern was defined according to Ming classification and the tumor staging for each gastric cancer was evaluated according to the TNM staging system indicating the extent of tumor spread. Furthermore, tumor diameter,differentiation, grading and vessel invasion were determined. The grade of dysplasia was determined according to the dysplastic grading standard of Chinese Gastric Cancer Cooperative Group. In addition,follows-up were carried out, and 34％ (35/101) of the patients were lost during folows-up, leaving 66 patients for the final study, the median follow-up time was 34.6 months,with a range of 3 months to 12 years.
1.3 Immunohistochemistry
The section were dewaxed in xylene and rehydrated in graded ethanols. Endogenous peroxidase activity was blocked by immersion in 0.3％ methanolic peroxide for 10 min under room temperature. Immuno-reactivity of target antigens was enhanced using micro-wave antigen retrieval.The sections were placed in a micro-wave oven containing 0.01 M sodium citrate buffer (pH6.0),heated to 98-100℃ for 20 min by 250 w, and then cooled, followed by incubation with 10％ bovine serum for 10 min. The sections were then incubated with primary monoclonal antibody (diluted 1∶8) for 24 hours under 4℃ ,then incubated with secondary biotinylated antibody for 30 min. After incubation with streptavidin-biotin-peroxidase complex for 30 min,the bound complexes were visualized by the application of a 0.05％ solution of 3.3-diaminobe-nzidin (DAB),containing 0.3％ hydrogen peroxide as a substrate. The reaction was stopped in tap water, cells were counterstained with hematoxylin,dehydrated, and coverslipped, then viewed under microscopy.
1.4 Evalution of E-CD expression
Expression of E-CD was semiquantitatively categorized into four groups： (1) negative(－)： no expression of E-CD;(2)weakly positive(＋)： less than 25％ of positive tumor cells;(3) moderately positive (＋ ＋)： 25～ 75 per cent of positive tumor cells;(4) strongly positive(＋ ＋ ＋)： ＞75 per cent of positive tumor cells. All sections were evaluated by two different pathologists without knowledge of the clinical outcome.
1.5 Statistical analysis
Comparision of the distribution of E-CD for different groups were performed using the chi-square test or the Wilcoxon test.Analyses of survival were performed using the life table method and the differences among the groups of patients were measured by the Logrank test.P values ＜0.05 were considered significant.
2 RESULTS
The normal and dysplastic gastric mucosae strongly expressed E-CD at the cell-cell bounderies, whereas 88.1％ (89/101) gastric tumors showed reduced or absent E-CD expression.
The significant correlation was observed between low E-CD expression and cellular dedifferentiation (P＜0.05) and Ming's infiltrative type of gastric cancer (P＜0.01),no significant correlation was found between E-CD expression and depth of invasion,venous and lymphatic vessel invasion, lymph node metastatic status and tumor size (P ＞0.05)(Table 1).
Table 1 E-CD expression and correlation with different
clinicopathological parameters
| parameters |
n |
Intensity of E-CD expression N(％ ) |
P Value |
| - |
+ |
++ |
+++ |
| Grading |
|
| G1/G2 |
52 |
13(20.5) |
25(48.1) |
8(15.4) |
6(11.5) |
＜0.025 |
| G3/G4 |
49 |
21(42.9) |
16(32.7) |
6(12.2) |
6(12.2) |
| Growth Pattern(Ming's) |
|
| expansive |
48 |
9(18.8) |
26(54.2) |
5(10.3) |
8(16.7) |
＜0.01 |
| infiltrative |
53 |
25(47.2) |
15(28.3) |
9(17.0) |
4(7.5) |
| Lymphatice vessel invasion |
|
| negative |
29 |
11(37.9) |
12(41.5) |
3(10.3) |
3(10.3) |
＞0.05 |
| positive |
73 |
23(31.9) |
29(40.3) |
11(15.3) |
9(12.5) |
| Venous vessel invasion |
|
| negative |
76 |
25(32.9) |
33(43.4) |
10(13.2) |
8(10.5) |
＞0.05 |
| positive |
25 |
9(36.0) |
8(32.0) |
4(16.0) |
4(16.0) |
| PN category |
|
| node-negative |
36 |
14(38.9) |
13(36.1) |
4(11.1) |
5(13.9) |
＞0.05 |
| node-positive |
65 |
20(30.8) |
28(43.1) |
10(15.4) |
7(10.8) |
| PT category |
|
| T1/T2 |
48 |
15(31.3) |
23(47.9) |
4(8.3) |
6(12.5) |
＞0.05 |
| T3/T4 |
53 |
19(35.8) |
18(34.0) |
10(18.9) |
6(11.3) |
| Tumor size |
|
| ≤5cm |
77 |
25(32.5) |
31(40.3) |
12(15.6) |
9(11.7) |
＞0.05 |
| ＞5cm |
24 |
9(37.5) |
10(41.7) |
2(8.3) |
3(12.5) |
| TNM staging |
|
| Ⅰ |
24 |
10(37.0) |
11(40.7) |
2(7.4) |
4(14.8) |
＞0.05 |
| Ⅱ |
17 |
6(35.3) |
9(52.9) |
2(11.8) |
0(0) |
| Ⅲ |
33 |
10(30.3) |
11(33.3) |
7(21.2) |
5(15.2) |
| Ⅳ |
24 |
8(33.3) |
9(37.5) |
4(16.7) |
3(12.5) |
The 1,3 and 5-year survival rates of five cases with gastric cancer expressed E-CD normally was 100％ respectively, whereas the 1,3 and 5-year survival rates of 61 cases with tumors of low E-CD expression was 83.11％ , 61.2％ and 58.8％ , respectively. The 3 and 5-year survival rates of patient with gastric cancer expressed E-CD normally was significantly higher than those of patients with reduced or negative expression of E-CD (P＜0.05).3 DISCUSSION
Cadherins are cell surface molecules which are responsible for calcium-dependent cell-cell adhesion. Their adhesive properties,involving homophilic interactions are essental for establishing and maintaining intercellular connections in cooperation with other associated molecules, such as α-and β-catenins[3]. E-CD is a member of the cadherin family which is predominantly expressed in epithelial cell and plays a key role in the controlling of epithelial cell polarity and differentiation and the organization of tissue structure.However, as shown by a number of studies in vitro and in vivo, the E-CD gene is also expressed in tumors, where it plays a role as an invasion-suppressor. The invasiveness of epithelial tumor cell lines could be inhibited in vitro by exposure to anti-E-CD Mabs.Based on these adta,it seems reasonable to assume that E-CD may also render tumor cells less invasive in vivo, exerting a positive effect on survival[4]. Recently, results of several studies have revealed that loss or reduced expression of E-CD in human head and neck, bladder and esophageal cancers was associated closely with poor differentiation and invasive capacity or highly metastatic potential of tumor cells, and normal expression of E-CD was positively correlated with better 5-year survival rate[2]. Compared with normal gastric mucosa,the percentage of gastric cancers with a reduced E-CD expression varies from 17％ to 92％ , and the expression of E-CD was directly correlated with the grade of tumor differentiation[5]. The current study showed that normal and dysplastic gastric mucosae strongly expressed E-CD at the cell-cell bounderies,whereas 88.1％ (89/101) of the gastric tumors showed reduced or absent expression of E-CD.The significant correlation was found between low E-CD expression and cellular dedifferentiation and Ming s infiltrative type of gastric cancer.The results are consistent with other studies, which suggest that E-CD expression may be an early event in metastatic cascade.
Although the relationship between E-CD expression and tumor invasion and metastasis of gasric cancer remains controversial, major studies suggest that down-regulation of E-CD is correlated significantly with poor prognosis.Yoshida reported a closely correlation between reduced expression of E-CD and invasion and metastasis of gastric cancer[6], whereas Gabbert and Mayer could not find any correlation between E-CD expression and tumor progression of gastric cancer, but all of their studies have shown that the survival rates of patients with E-CD-positive tumor were significantly higher than those of patients with E-CD-negative tumors[5]. Our results indicated that no significant correlation was found between E-CD expression and depth of invasion, venous and lymphatic vessel invasion,lymph node status and tumor size. And the three and five-year survival rates of patients with gastric cancer expressed E-CD normally were significantly higher than those of tumors with reduced or negative expression of E-CD. Our finding are consistent with the observations of Gabbert et al. The underlying biological mechanisms by which E-CD functions are not yet completely understood so far. The observation that E-CD expression is correlated with patient's prognosis, but not with tumor invasion and metastasis of gastric cancer, suggests that the effects of E-CD on prognosis of gastric carcinomas may be carried out by more complicate molecular biological mechanisms.The speculation is supported by the most recent studies showing that E-CD mediated cell-cell adhesion system was associated with the Wingless-Wnt signals transduction system[7].
In summary,the present knowledge on E-CD functions remains basic and further studies are necessary. Our present study on 101 gastric cancer patients has shown that the down-regulated expression of E-CD is significantly correlated with cellular dedifferentiation and infiltrative growth of gastric cancer and with lowered 3-and 5-year survival rate. Our retrospective study may therefore,encourage further investigation to verify the prognostic role of E-CD expression under prospective conditions as well.
*通讯作者：
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收稿日期：1999-01-20
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