[Polymorphism/loss of heterozygosity of APC gene in GERD-Barrett's metaplasia-dysplasia-adenocarcinoma sequence].

UNLABELLED

The incidence of esophageal adenocarcinoma (ADC) has been increasing rapidly over the past few decades. Gastro-esopageal reflux disease (GERD), Barrett's esophagus (BE) and Barrett-associated dysplasia are a risk factor for esophageal cancer, but endoscopic surveillance have only a limited influence on cancer mortality. There is a great need to find molecular biomarkers predicting increased progression risk in GERD-Barrett's metaplasia-dysplasia-adenocarcinoma sequence to improve risk assessment and stratification of patients to surveillance program.

AIM OF THE STUDY

To evaluate the polymorphism and prevalence of loss of heterozygosity (LOH) of APC tumor suppressor gene in mataplasia, dysplasia and adenocarcinoma.

MATERIAL AND METHODS

In esophageal mucosal samples of 79 patients with: GERD (n=33), BE (n=27), BE+dysplasia (n=8) and ADC (n=11) we have studied LOH of APC tumor suppressor gene using PCR-restriction fragment length polymorphism (RFLP). A 133 bp fragment, spanning exon 11 of the APC gene was amplified, and Rsal digestion of the PCR product defined the alleles as either homozygous 133 bp (Rsa(-/-)) or 87 and 46 bp (Rsa(+/+)) fragments, and heterozygous (Rsa(+/-)) exhibiting the three fragments. Control peripheral blood cell DNA samples have been collected from 60 normal healthy subjects.

RESULTS

Among 79 patients, there were 16 heterozygous (20%) for APC gene. In 16 informative heterozygous LOH was detected in 7 cases: 2/5 with GERD, 3/7--with BE, 1/2--with BE+dysplasia and 1/2--with ADC. There were no statistical differences between studied groups (NS). Distribution of the three alleles, Rsa(+/-), Rsa(+/+), and Rsa(-/-) was: 38, 47 and 15% in the healthy individuals, 25%, 25% and 50%--in GERD patients, 29%, 41% and 29%--in BE, 36%, 45% and 18% in BE+dysplasia and 25%, 67% and 8% in ADC patients, respectively. The frequency of heterozygous cases in control group was significantly higher than in patients group (p = 0.018), whereas Rsa (-/-) were the most frequent in patients group (p = 0.008). Rsa (-/-) were seen significantly more often in GERD compared to ADC patients (p = 0.005), in opposite to Rsa (+/+), which were significantly more frequent in ADC vs. GERD (p = 0.007).

CONCLUSIONS

APC gene inactivation concerns minority of patients with esophageal adenocarcinoma, however, its detection indicates higher risk of progression to ADC. APC alternations appear to be early in GERD-BE-dysplasia-ADC sequence. The specific polymorphism may identify patients with high risk of progression into BE.