INTRATUMOR DISTRIBUTION OF 1P DELETIONS IN HUMAN COLORECTAL ADENOCARCINOMA IS COMMONLY HOMOGENEOUS - INDIRECT EVIDENCE OF EARLY INVOLVEMENTIN COLORECTAL TUMORIGENESIS

BACKGROUND. Cytogenetics and molecular biology studies have indicated that a large subset of human colorectal adenocarcinomas have distal 1p chromosome arm deletions. The aim of this study was to evaluate the i ntratumor distribution of 1p deletions under the assumption that homog eneity is an indication of early occurrence. METHODS. Seventy-nine his tologically selected primary sectors (40 superficial and 39 deep) and 3 lymph node metastases obtained from 20 human sporadic adenocarcinoma s were analyzed. Interphase two-color fluorescence in situ hybridizati on (FISH) was applied to cytocentrifuged nuclei using a centromeric pr obe for chromosome 1 and a telomeric probe mapping to the 1p36 band. R ESULTS. Deletions at 1p were observed in 35 of 82 tumor samples corres ponding to 9 of 20 adenocarcinomas analyzed (45%). Seven of the 9 aden ocarcinomas with 1p deletions showed an intratumor presence of these a berrations in all the different tumor sectors. CONCLUSIONS. These data , acquired by FISH interphase cytogenetics, confirm that 1p deletions in colorectal adenocarcinoma are common and suggest that this structur al chromosomal aberration occurs mainly as an early event in colorecta l tumorigenesis. Cancer 1998;83:415-22. (C) 1998 American Cancer Socie ty.