[Recent data on the cytogenetics of colorectal adenocarcinoma]

A brief description of the results obtained by cytogenetic analyses of cancer cells from colorectal adenocarcinomas is reported. Two distinct patterns of chromosomal anomalies are observed. The major one, called "monosomic type", because many chromosomes losses exist, is characterised by the losses or deletions of the following chromosomes 18, 17 (short arm = p), 1p, 4, 14, 5 (long arm = q) and 21. It frequently evolves towards polyploidy, by duplication of all remaining chromosomes. The minor one, called "trisomic type", is characterised by the gain of several chromosomes: 7, 12, X, 5 and 8. The chromosomal anomalies observed seem to have no topological relationships with oncogenes, and other interpretations for their occurrence were investigated. The numerous and frequent deletions of some chromosomes, like 17p and 18, may indicate the involvement of recessive genes, like in the anti-oncogene system. In addition, it is observed that most deletions involve genes for "de novo" pathways whereas gains involve genes for salvage pathways of the synthesis of nucleotides. A correlated cytogenetic and enzymologic study was thus developed, and the first results show that the chromosomal pattern may well indicate the metabolic deviations. Monosomic type tumors have, on the average, a relatively low "de novo" and a high salvage pathways, and trisomic type tumors a high "de novo" and salvage pathways. Since chemotherapy is principally orientated against "de novo" pathways of the synthesis of nucleotides, these results may help to understand the difficulties of chemotherapy in colorectal cancers and perhaps to adapt it better.