ALLELIC IMBALANCE AT NME1 IN MICRODISSECTED PRIMARY AND METASTATIC HUMAN COLORECTAL CARCINOMAS IS FREQUENT BUT NOT ASSOCIATED WITH METASTASIS TO LYMPH-NODES OR LIVER

Allelic imbalance at the NME locus on chromosome 17q21 was analyzed in colorectal cancer patients using a highly polymorphic microsatellite repeat sequence within NME1 itself. Duplicate samples of carcinoma and adjacent normal tissue were obtained by microdissection from 6 to 7-m u m paraffin sections of 94 primary carcinomas (treatment gears 1979-1 993) and available lymph node and liver secondaries. In 55 patients in formative (heterozygous) at this locus, allelic imbalance was examined in primary and secondary carcinomas. Microsatellite instability preve nted assessment of allelic balance in two casts, and there was no evid ence of homezygous loss at NME1 in any case analyzed. Allelic imbalanc e at the NME locus in carcinomas was frequent (27/53; 51%), and concor dant results were obtained between primary carcinoma and secondary dep osits in 30 of 33 (91%) cases. Three discordant cases showed allelic i mbalance in secondary deposits but not the primary lesion. Although fr equent, allelic imbalance at NME1 had no relationship to Dukes' stage at presentation or with subsequent hepatic metastasis, nor with the pr imary carcinoma site (proximal versus distal), tumor size, or mitotic or apoptotic index. Moreover, neither disease-free nor overall surviva l differed between patients with carcinomas showing NME1 allelic imbal ance and patients with carcinomas that did not. Our results show that although allelic imbalance is frequent at the NME locus in primary and secondary colorectal carcinomas, there is no evidence to link this wi th clinical or pathological features or with metastatic potential. Mic rosatellite PCR and microdissection of enriched populations of carcino ma cells allowed uniformly successful analysis of samples from archiva l formalin-fixed paraffin-embedded tissue up to 15 years old and clear assessment of allelic imbalance in tumor specimens. Target sequences (e.g., microsatellites and minisatellites) up to approximate to 200-25 0 bp may be reliably analyzed for allelic balance, suggesting that thi s method is of general utility in the genetic analysis of primary and metastatic neoplasia.