Chromosome and oncogene studies in human rectal and colon carcinomas.

Cytogenetic examinations of 48 rectal and 17 colon carcinomas and analyses of proto-oncogene activation on 67 of the former and 8 of the latter tumors were performed. Besides a general considerable heterogeneity of chromosome counts, some chromosomes were found to contribute non-randomly to hypersomies (# 2, 3, 7, 9, 19, 20 and 6) and to hyposomies (# 14, 15, Y, 21, and 18) in this material. Chromosomal markers non-randomly involved breakpoint clusters on 17p11, 13q11, 7p, 1p11, and 1p36 and on the centromeric regions of chromosomes 1, 8, 14, 15 and 21. Cytogenetic equivalents of gene amplification ("double minutes") were present in only rather small cell fractions (less than 20%) of 50% of the studied tumors. Using a cDNA technique and a battery of respective probes, proto-oncogene overexpression was screened for in the tumor samples, but also in 24 samples of inconspicuous mucosae of tumor patients and in two mucosae of healthy individuals. Simultaneous overexpression of several proto-oncogenes was the most characteristic finding in the tumor cells. However several of the mucosa samples obtained from tumor patients also just exhibited clear signals of proto-oncogene overexpression, which were not found in epithelial cells from non-tumor patients.