CYTOGENETIC FINDINGS IN METASTASES FROM COLORECTAL CANCER Georgia BARDI 1,3,6 *, Luis Antonio PARADA 1 , Lilian BOMME 3 , Nikos PANDIS 1,3,6 , Bertil JOHANSSON 1 , Roger WILLE ´ N 2 , Claus FENGER 4 , Ole KRONBORG 5 , Felix MITELMAN 1 and Sverre HEIM 1,3,7 1 Department of Clinical Genetics, University Hospital, Lund, Sweden 2 Department of Pathology, University Hospital, Lund, Sweden 3 Department of Medical Genetics, Odense University, Odense, Denmark 4 Department of Pathology, Odense University, Odense, Denmark 5 Department of Gastrointestinal Surgery, Odense University, Odense, Denmark 6 Department of Genetics, G. Papanicolaou Research Center, Saint Savas Hospital, Athens, Greece 7 Department of Genetics, The Norwegian Radium Hospital and Institute for Cancer Research, Oslo, Norway Eighteen tumor samples from 11 patients with metastatic colorectal cancer were cytogenetically analyzed after short- term culturing. Of the 13 metastases examined, 11 were from lymph nodes, 1 from the peritoneum and 1 from the lung. In 5 of the 11 patients, matched samples from the primary tumor and lymph node metastases were analyzed. Cytogenetic similarities between the primary and secondary lesions were found in all 5 cases, indicating that many of the chromosomal aberrations presumably occurred before dis- ease spreading took place. Compared with the primaries, the metastasesappeared to exhibit decreased clonal heterogene- ity but, concurrently, an increase in the karyotypic complex- ity of individual clones. Among the aberrations recurrently found in metastatic lesions were del(1)(p34), i(17)(q10), 218, 2Y, 221, 17 and 120, all of which have been seen repeatedly in previous series of primary colorectal carcinomas, and del(10)(q22) and add(16)(p13), which so far have not been associated with primary tumorsand which may play a particu- lar pathogenetic role in the metastatic process. Int. J. Cancer 72:604–607, 1997. r 1997 Wiley-Liss, Inc. The major cause of death in colorectal-cancer patients is metastasis rather than localized disease. It is therefore clear that a better understanding of the metastatic process and the finding of ways/tools to prevent it stand out as prime goals in colorectal- cancer research. Few studies utilizing genetic techniques have focused on metas- tastic lesions from large bowel carcinomas. Pairs of primary and metastatic tumors from the same patient have been examined for total DNA content using flow cytometry (Koha et al., 1992; Vijayan and Goh, 1995), for allelic loss (Ding et al., 1994; Jen et al., 1994) and for TP53 mutations (Peller et al., 1995). The chromosomal characteristics of metastases from colorectal carcino- mas are largely unknown as less than 10 cases have been reported (Reichman et al., 1981; Muleris et al., 1987; Bardi et al., 1993). In contrast, about 320 primary malignant colorectal tumors with clonal chromosomal aberrations have been described (Mitelman, 1994). The only karyotypic data on primary and metastatic tumors from the same patients derive from 2 studies on established cell lines (Gre ´goire et al., 1993; Gagos et al., 1995). The aim of the present study was to provide additional information on the karyotypic characteristics of colorectal-cancer metastases, with special emphasis on comparisons between primary and secondary tumors in the same individuals. MATERIAL AND METHODS Fresh tumor samples from 15 cases of metastatic colorectal cancer were processed for cytogenetic investigation after short- term culturing. In 4 of the cases, results were obtained only from the primary tumors; these cases are not included in this study. The analysis was successful in 18 samples from 11 patients, all of Dukes’ stage C, except for cases 6 and 8, which were stage D. The primary tumor, always an adenocarcinoma, was located in the rectum in cases 1, 2, 4, 5, 10 and 11 and in the colon in the remaining cases. The presence of carcinoma cells in the tissue sent for chromosomal analysis was checked by imprint cytology and routine histopathology. In total, cytogenetic data on 13 metastases are presented: 11 derived from lymph nodes, 1 from the peritoneum and 1 from the lung. In 5 of the cases, samples from matched primary tumors and their lymph node metastases were analyzed successfully. In case 1, samples from 2 different lymph node metastases were examined. In case 6, samples from one metastasis to a lymph node and another to the peritoneum were investigated. Short-term cultures were initiated as previously described (Bardi et al., 1993). After 3–10 days in culture, the cells were harvested, chromosome preparations were made and the chromosomes were G-banded with Wright’s stain. The clonality criteria and the description of the tumor karyotypes followed the recommendations of ISCN (1995). RESULTS The tumor karyotypes are listed in Table I. Common chromo- somal aberrations were found in all 5 pairs of primary tumor/ matched lymph node metastases. In case 6, the 2 metastatic lesions had cytogenetically related abnormal clones. In case 1, 2 abnormal clones were found in lymph node 1: one was hypertriploid (Fig. 1) and identical to the one detected in the primary tumor, the other was hyperdiploid and similar to the clone detected in lymph node 2. In case 2, 3 abnormal clones, 2 triploid and 1 hexaploid, were found in the primary tumor, whereas only a hypertriploid clone was found in the metastasis. In case 3, 2 related hyperdiploid clones were detected, one with trisomy 12 as the only change (Fig. 2), the other with both 18 and 112. In the metastasis of that case, only the clone with trisomy 12 was detected. In case 4, 3 abnormal clones were seen, one with trisomy 20 as the only change, the 2 others highly complex with structural re-arrange- ments of all chromosomes, double minutes and rings. The near- diploid complex clone also was found in the metastatic sample. In case 5, 2 abnormal clones, one hypodiploid and one hypotetraploid, were found in both the primary and metastatic samples. In case 6, one hypotetraploid and one near-octaploid clone were detected in the lymph node sample, whereas only the near-octaploid clone was found in the peritoneal metastasis. Simple chromosomal changes were found in the lymph nodes of cases 7 and 9 and in the lung metastasis of case 8, whereas highly complex abnormal karyotypes were identified in the lymph nodes of cases 10 and 11. Contract grant sponsors: Swedish Cancer Society; Norwegian Cancer Society. *Correspondence to: Department of Genetics, Saint Savas Hospital, 171 Alexandras Ave., 115 22 Athens, Greece. Fax: 30-1-6420146. E-mail: Georgia.Bardi@Genet.ath.forthnet.gr Received 23 January 1997; revised 17 March 1997 Int. J. Cancer: 72, 604–607 (1997) r 1997 Wiley-Liss, Inc. Publication of the International Union Against Cancer Publication de l’Union Internationale Contre le Cancer