RELAXATION OF INSULIN-LIKE GROWTH-FACTOR-2 GENE IMPRINTING IN ESOPHAGEAL CANCER

Paternal allele-specific expression is identified for the insulin-like growth factor 2 (IGF2) gene. Relaxation or loss of ICF2 imprinting, h owever, has been reported in several neoplasms. We studied the express ion of ICF2 mRNA in 35 squamous cancers of the esophagus and searched for the presence or absence of relaxation of IGF2 imprinting. In 28 (8 0%) cases, IGF2 mRNA was overexpressed in the tumor tissues (T) compar ed to the normal tissues (N). The patients whose tumor invaded the adv entitia showed a higher T/N ratio than those whose tumor was restricte d to the musculi propria layer. Heterozygosity was determined by using the Apa I polymorphism in exon 9. Thirteen of 35 cases showed heteroz ygosity. in these 13 cases, a similar analysis was performed on cDNA o btained by reverse transcriptase-polymerase chain reaction. Consequent ly, 7 cases disclosed relaxation of IGF2 imprinting in the tumor tissu e. The cases of esophageal cancer with relaxation of IGF2 imprinting s howed a higher T/N ratio and deeper invasion than those without relaxa tion. The results suggest that overexpression of IGF2 mRNA plays an im portant role in esophageal cancer and, in certain cases, is associated with relaxation of IGF2 imprinting. (C) 1996 Wiley-Liss, Inc.