KARYOTYPIC CHARACTERIZATION OF COLORECTAL ADENOCARCINOMAS

Cytogenetic analysis of short-term cultures from 52 primary colorectal adenocarcinomas revealed clonal chromosome aberrations in 45 tumors, whereas the remaining 7 had a normal karyotype. More than I abnormal c lone was detected in 26 tumors; in 18 of them, the clones were cytogen etically unrelated. The modal chromosome number was near-diploid in 32 tumors and near-triploid to near-tetraploid in 13. Only numerical abe rrations were identified in 13 carcinomas, only structural aberrations in 3, and 29 had both numerical and structural changes. The most comm on numerical abnormalities were, in order of decreasing frequency, gai ns of chromosomes 7, 13, 20, and Y and losses of chromosomes 18, Y, 14 , and 15. The structural changes most often affected chromosomes 1, 17 , 8, 7, and 13. The most frequently rearranged chromosome bands were, in order of decreasing frequency, 13q10, 17p10, 1p22, 8q10, 17p11, 7q1 1, 1p33, 7p22, 7q32, 12q24, 16p13, and 19p13. Frequently recurring abe rrations affecting these bands were del(l)(p22), i(8)(q10), i(13)(q10) , and add(17)(p11-13). The most common partial gains were from chromos ome arms 8q, 13q, and 17q and the most common partial losses from chro mosome arms 1p, 8p, 13p, and 17p. A correlation analysis between the k aryotype and the clinicopathologic features in our total material, whi ch consists of altogether 153 colorectal carcinomas, including 116 wit h an abnormal karyotype, showed a statistically significant associatio n (P < 0.05) between the karyotype and tumor grade and site. Carcinoma s with structural chromosome rearrangements were often poorly differen tiated; well and moderately differentiated tumors often had only numer ical aberrations or normal karyotypes. Abnormal karyotypes were more c ommon in rectal carcinomas than in carcinomas situated higher up. Near -triploid to near-tetraploid karyotypes were more than twice as freque nt in tumors of the distal colon as in those of the proximal colon and rectum. The cytogenetic data indicate that carcinomas located in the proximal colon and rectum, which often are near-diploid with simple nu merical changes and cytogenetically unrelated clones, probably arise t hrough different mechanisms than do tumors located in the distal colon , which more often have complex near-triploid to near-tetraploid karyo types. (C) 1995 Wiley-Liss, Inc.