Chromosome arm 20q gains and other genomic alterations in colorectal cancer metastatic to liver, as analyzed by comparative genomic hybridization andfluorescence in situ hybridization

Comprehensive information about the molecular cytogenetic changes in metast ases of colorectal cancer is not yet available,To define such changes in me tastases, we measured relative DNA sequence copy numbers by comparative gen omic hybridization (CGH). Samples from 27 liver metastases and 6 synchronou s primary tumors were analyzed. An average of 9.9 aberrations per tumor was found in the metastases. Gains of chromosome arms 20q (85%), 13q (48%), 7p (44%), and 8q (44%) and losses of chromosome arms 18q (89%) 8p (59%), Ip ( 56%), and 18p (48%) were detected most frequently. Chromosomes 14 and 15 we re lost in 26% and 30% of the metastases, respectively No consistent differ ences were observed between primary tumors and synchronous metastases. Fluo rescence in situ hybridization (FISH) was used for further characterization of gains of chromosome arm 20q. Touch preparations of 13 tumors that had d emonstrated 20q gain with CGH were examined with FISH by use of a set of pr obes mapping to different parts of 20q. A probe for 20p was used as a refer ence. FISH showed relative gain of at least one 20q locus in 12 of the tumo rs. High-level gains were detected in 38% of the tumors, preferentially for probes mapping to band 20q 13. Our CGH data indicate that colorectal metas tases show chromosomal changes similar to those that have been reported for primary tumors. Chromosomal losses were seen at higher frequency, particul arly for chromosomes 14 and 15. Ey FISH, we identified subregions on chromo some arm 20q that are frequently involved in DNA amplifications in colorect al cancer and that may harbor candidate proto-ancogenes. (C) 1999 Wiley-Lis s, Inc.