Screening and expression of associated genes in gastric dysplasia

Microsatellite instability in gastric cancer and pre-cancerous lesions

AIM: To investigate the microsatellite instability (MSI) in cancer and pre-cancerous lesions of the stomach and its mechanisms underlying the development of gastric cancer.

METHODS: Thirty-six gastric cancer samples were obtained from patients undergoing surgery. Forty-one gastric mucosa samples with dysplasia and 51 with intestinal metaplasia (IM) were obtained from patients with chronic gastritis undergoing gastro-endoscopy. Genomic DNA was extracted from the samples. Silver staining single strand conformation polymorphis-polymerize chain reaction (SSCP-PCR) was used to screen MSI markers at 5 loci (Bat-25, Bat-26, D5S346, D17S250, and D2S123) in fresh tissues and formalin-fixed, paraffin-embedded samples and their corresponding normal gastric mucosa.

RESULTS: The abnormal shifting of the single-strand DNA (MSI) was identified in 21 out of 36 (58.3%) gastric cancers. Seven cases showed high-level MSI (two or more loci altered) and 14 showed low-level MSI (one locus altered). Gastric cancer with MSI had a tendency to be located in the distal stomach. MSI was also detected in 11 out of 41 (26.8%) dysplasia samples and in 9 of 51 (17.6%) IM samples respectively. Three cases of dysplasia and one case of IM showed high-level MSI. Eight cases of dysplasia and 8 cases of IM displayed low-level MSI. MIS in IM was found only in moderate or severe-grade IM. No association was detected between MSI and dysplasia grade.

CONCLUSION: Accumulation of MSI in dysplasia and intestinal metaplasia of gastric mucosa may be an early molecular event during gastric carcinogenesis and may contribute to the acquisition of transformed cell phenotype and the development of gastric cancer.

Cloning and expression of gastric cancer related gene GCRG224 in E.coli

AIM: To express gastric cancer related gene GCRG224 by using thioredoxin fusion expression system.

METHODS: GCRG224 cDNA with complete open reading frame was amplified by PCR from plasmid pGEM-T, and then cloned into thioredoxin fusion expression vector pET102/D-TOPO. The recombinant plasmid was further transformed into E.coli BL21 strain. After induction with IPTG, thioredoxin-GCRG224 fusion protein was expressed in E.coli.

RESULTS: SDS-PAGE analysis showed the thioredoxin-GCRG224 fusion protein with a relative molecule mass of 16 800 was highly expressed. The thin layer gel scanning analysis showed that the yield of GCRG224 fusion protein was 22.3% of the total bacterial protein.

CONCLUSION: The GCRG224 recombinant fusion protein is successfully expressed in E.coli.

Expression of tyrosine kinase Syk and its clinical significance in gastric carcinoma

AIM: To evaluate the effects of the Syk mRNA expression in human gastric carcinoma on tumor growth and metastasis, and the correlation of expression of the Syk gene with p53.

METHODS: Using semi-RT-PCR technique, we detected specimens from 61 gastric carcinoma patients (tumor tissues, adjacent normal tissues) for their rate and level of Syk and p53 gene expression. Meanwhile, immunohistochemical staining was also used to detect Syk expression.

RESULTS: All normal gastric tissues were detected the expression of the Syk gene. Unlike normal tissue, 47 out of 61 breast cancer tissue did not show any detectable Syk mRNA expression, and there were significant difference between the two groups (χ² = 72.3, P < 0.05). The level of Syk mRNA in the primary gastric carcinoma tissues was significantly lower than that in the adjacent non-cancerous gastric tissues (t = 2.1, P < 0.05). Furthermore, only 3 gartric carcinoma tissues in 31 patients with lymph node metastasis had the Syk mRNA expression. The Syk mRNA expression was negatively correlated to lymph node metastasis (χ² = 4.85, P < 0.05). And the Syk expression was correlated to that of p53 (χ² = 22.03, P < 0.05).

CONCLUSION: The expression of the Syk gene may play an important role in suppressing growth and metastasis in gastric cancer. Syk gene expression is repressed in a p53-dependent manner.

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.

Expression of estrogen inducing gene PS2/TFF1 in gastric cancer and precancerous lesions

AIM

To determine the significance of PS2/TFF1 protein expression in chronic superficial gastritis (CSG), gastric ulcer (GU),gastric mucosal intestinal metaplasia (IM), gastric mucosal dysplasia and gastric cancer(GC).

METHODS

Pathologic specimens of 121 patients with gastric mucosal diseases and 20 healthy volunteers were immunostained for PS2/TFF1.

RESULTS

Positive PS2/TFF1 staining was seen throughout all epithelia with normal gastric mucosas, CSG, GU and in complete type of intestinal metaplasia (20/21). On the contrary, 11 of 20 incomplete type of intestinal metaplasia had positive staining (P <0.01). The expressions of PS2/TFF1 protein in CSG and GU were significantly higher than that in control group (P <0.01), while the expressions of PS2/TFF1 protein in IM,gastric mucosal dysplasia and GC were obviously lower than that in control group (P <0.01).

CONCLUSION

Our results indicate that PS2/TFF1 may play an important role in gastric mucosal protection,and loss of PS2/TFF1 expression may occur as an early event in the malignant transformation process of intestinal-type tumors.