Loss of heterozygosity of SMAD4/DPC4 in gastric carcinoma

Change of Smad4 expression in gastric carcinogenesis and its clinicopathological significance

AIM: To characterize the changes of Smad4 expression in the multistage carcinogenesis of gastric cancer and investigate the correlations between these changes and the clinicopatholo-gical features.

METHODS: The expression of Smad4 was detected by immunohistochemisty in the paraffin-embedded samples from 103 patients with gastric carcinoma (16 cases in early stage, 87 cases in progressive stage). The result was comparatively analyzed with the histopathology.

RESULTS: Among 103 gastric carcinoma samples, 28 cases with intestinal metaplasia and 13 cases with atypical hyperplasia were determined. In 2 cases, intestinal metaplasia and atypical hyperplasia were simultaneously determined in the same tissue. Normal gastric mucosa showed positive Smad4 expression. Smad4 expression decreased in different degrees of lesions, and the reduced rate increased with the lesion progression (P < 0.05). The positive rates of Smad4 expression in intestinal metaplasia and atypical hyperplasia were 89.3% and 76.9% respectively, while it was 54.4% in carcinoma cells. Positive expression of Smad4 was found in 10 (62.5%) of early carcinoma and 46 (52.9%) of advanced one. The expression of Smad4 in gastric carcinoma showed a significant correlation with the differentiation of carcinoma (P < 0.01). The reduced rate of Smad4 expression in poorly-differentiated carcinoma was higher than that in well-differentiated one (63.0% vs 31.6%, P < 0.01). Positive expression of Smad4 was found in 15 of 20 gastric cardia carcinoma (75%), which was significantly higher than that in the other positional carcinoma (P < 0.05). The positive rates of Smad4 expression in gastric carcinoma of fundus, corpus and antrum were 50%, 53.6% and 46.7% respectively. Smad4 expression had no marked correlations with the age of patients, gender, tumor size, lymph node metastasis and the depth of tumor invasion (P > 0.05).

CONCLUSION: Reduced expression of Smad4 is a frequent molecular event in gastric carcinogenesis, and closely correlated with the progression of lesions and differentiation of carcinoma.

Loss of fragile histidine triad protein expression and its clinicopathological significance in gastric cancer

AIM: To investigate the expression of fragile histidine triad protein, Fhit and the possible relationship between its expression and clinicopathological indices in gastric carcinoma.

METHODS: Fhit protein expression was detected in 76 cases of gastric carcinoma, 58 dysplasia and 10 normal mucosae by immunohistochemical method to analyse its relationship to histological grade, clinical stage, metastatic status and prognosis.

RESULTS: The loss of Fhit protein expression was detected in 48/76 (63.2%) cases of cancer tissue, 36/58 (62.1%)cases of adjacent dysplastic tissue and 0/10 cases of normal gastric mucosa. There was a significant difference in the expression of Fhit protein between cancer or adjacent dysplastic tissue and normal gastric mucosa (P=0.000). It was also showed that loss of Fhit protein expression was found first in 35.7% (10/28) of grade I-II, and in 79.2% (38/48) of grade III (P = 0.000); second in 43.8% (14/32)of stage I-II, whereas in 77.3% (34/44) of stage III-IV (P = 0.004); and last in 36.4% (8/22) of tumors without metastasis but in 74.1% (40/54) of those with metastasis (P = 0.003). The significant difference in the loss of expression of Fhit was found between cancers on different histological grade, clinical stage and metastatic status, respectively. Follow-up data showed that there was a significant difference in median survival time between carcinomas with loss of Fhit (33 mos) and those without (71 mos) (Log rank = 20.78; P = 0.000).

CONCLUSION: Fhit protein is an important tumor suppressor protein. Loss of Fhit protein expression may be associated with carcinogenesis, invasion, metastasis and prognosis in gastric carcinoma.