| ObjectiveTo detect Loss of heterozygosity ( LOH ) and microsatellite instabilities (MI) of FHIT gene and its relationship with the clinical pathological characteristics. To examine FHIT transcripts and the expression of Fhit protein and EBV infection in gastric cancer. To evaluate the role of FHIT gene and the relationship between FHIT gene and EBV infection in gastric cancer.MethodsLoss of heterozygosity (LOH) and microsatellite instabilities (MI) of FHIT was detected at four microsaterUite loci D3S1300, D3S4103, D3S1481 and D3S1234 using PCR in matched normal and cancerous tissues from 50 patients with primary gastric cancer. FHIT transcripts was detected by nest RT - PCR in 30 cases of gastric cancer and its products was sequenced. FHIT gene encoding protein was detected by western blot in 10 cases of gastric cancer. EBV infection was detected using PCR in 50 cases of gastric cancer.ResultsThe average frequency of LOH in gastric cancer was 32.4% , and the highest rate at D3S4103 was 43. 6%. LOH of FHIT gene was found at all four micro-saterllite loci. The average frequency of MI in gastric cancer was 26.4% , and the highest rate at D3S4103 was 36. 8%. MI of FHIT gene was detected in 11cases of gastric cancer at two or more loci. LOH of FHIT gene in gastric cancer had no relation to histological classification, Bormann classification, Lauren classification and lymph node metastases. LOH of FHIT gene in gastric cancer was related to invasive depth , The incidence of LOH in gastric cancers with se-rosa penetrated was significantly higher than that not with serosa penetrated (73.5% vs 37.5% , P <0.05). MI of FHIT gene in gastric cancer had no relation to histological type, Bormann type, Lauren type and depth of invasion. MI of FHIT gene in gastric cancer was related to the lymph nodes metastases, The incidence of MI in gastric cancer with no metastases to the lymph nodes was significantly higher than that with metastases to the lymph nodes (66. 7% vs 34. 3%, P<0.05).The wild type transcripts were detected in matched normal tissues of 30 cases of gastric cancer. Aberrant transcripts was found in 36.7% (11/30) gastric cancer tissues. FHIT gene transcripts of 5 cases less than 500bp. 1 cases was detected e deletion of whole transcripts. Wild - type transcripts of FHIT gene was found in 3/11 (27.2% ) cases of gastric cancer tissues. Sequence analysis of the aberrant fragments showed that there was a RT - PCR product missing ex-on 5 -7 in one case of gastric cancer, deletion length of 297bp, resulting in a junction between exon 4 and exon 8. The other aberrant trancript fragment included product missing exon 4-7, deletion length of 389bp,resulting in a junction between exon 3 and exon 8. The beginning of deletion was splicing site of exon. 40.0% (4/10) of gastric cancers showed loss or absence of Fhit protein expression compared with their matched normal tissues.EBV was detected in 10% (5/50) gastric cancers. Among 5 cases of EBV - associated gastric cancer ( EB VaGC) , 3 cases was advanced gastric cancer with poorly differentiated and lymph nodes metastases, 1 case was advanced gastric cancer with moderately differentiated and lymph nodes metastases, 1 case was middle stage gastric cancer with poorly differentiated and lymph nodes metastases. LOH of FHIT gene was found at all four microsaterllite loci in these 5 cases of EBVaGC, the frequency was D3S4103 (4/5), D3S1300 (3/5), D3S1481 (2/5) and D3S1234 (2/5). MI was detected at three microsaterlliteloci of D3S1300 (1/5), D3S1481 (1/5), D3S1234 (1/5). 4 cases of EB-VaGC was found aberrant transcripts of FHIT gene.ConclusionLOH and MI of FHIT gene revealed the genomic instabilities of gastric cancer cell, and participated in the carcinogenesis, progression of gastric cancer. LOH of FHIT gene was correlated with invasive depth. MI of FHIT gene was correlated with lymph node metastases. It is suggested that MI of FHIT gene play an important role in carcinogenesis of gastric cancer. LOH of FHIT gene play an important role in dev...
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