Cytogenetic study of rectosigmoidal adenocarcinomas

Evolutionary patterns of chromosomal instability and mismatch repair deficiency in proximal and distal colorectal cancer

AIM

Colorectal carcinomas (CRCs) progress through heterogeneous pathways. The aim of this study was to analyse whether or not the cytogenetic evolution of CRC is linked to tumour site, level of chromosomal imbalance and metastasis.

METHOD

A set of therapy-naïve pT3 CRCs comprising 26 proximal and 49 distal pT3 CRCs was studied by combining immunohistochemistry of mismatch repair (MMR) proteins, microsatellite analyses and molecular karyotyping as well as clinical parameters.

RESULTS

A MMR deficient/microsatellite-unstable (dMMR/MSI-H) status was associated with location of the primary tumour proximal to the splenic flexure, and dMMR/MSI-H tumours presented with significantly lower levels of chromosomal imbalances compared with MMR proficient/microsatellite-stable (pMMR/MSS) tumours. Oncogenetic tree modelling suggested two evolutionary clusters characterized by dMMR/MSI-H and chromosomal instability (CIN), respectively, for both proximal and distal CRCs. In CIN cases, +13q, -18q and +20q were predicted as preferentially early events, and -1p, -4 -and -5q as late events. Separate oncogenetic tree models of proximal and distal cases indicated similar early events independent of tumour site. However, in cases with high CIN defined by more than 10 copy number aberrations, loss of 17p occurred earlier in cytogenetic evolution than in cases showing low to moderate CIN. Differences in the oncogenetic trees were observed for CRCs with lymph node and distant metastasis. Loss of 8p was modelled as an early event in node-positive CRC, while +7p and +8q comprised early events in CRC with distant metastasis.

CONCLUSION

CRCs characterized by CIN follow multiple, interconnected genetic pathways in line with the basic 'Vogelgram' concept proposed for the progression of CRC that places the accumulation of genetic changes at centre of tumour evolution. However, the timing of specific genetic events may favour metastatic potential.

Assessment of Cytogenetic Aberrations and Comet Assay in Colorectal Adenocarcinomas

Aims, Background and Study Design

Few studies have investigated the karyotypes of colorectal carcinomas with emphasis on the correlation between cytogenetic findings and clinicopathologic features. The aim of our study involving 20 colorectal adenocarcinomas was to determine their genomic alterations at the chromosomal level by correlating the cytogenetic findings with the extent of DNA damage and clinicopathologic parameters and to compare the results with those of healthy controls.

Results

Cytogenetic evaluation of patients and controls revealed 10 abnormal karyotypes in patients with adenocarcinomas located in the rectum, sigmoid and rectosigmoid regions. Four had numerical and six had structural abnormalities.

Conclusions

Statistical analysis revealed a significant difference compared with controls (P <0.01). The karyotypes and the extent of DNA damage assessed by the comet assay were also significantly correlated with tumor stage (P <0.01) using the Kruskal-Wallis non-parametric test, while no statistical significance was observed in relation to patient age and smoking.

Assessments of clonal composition of colorectal adenomas by FISH analysis of chromosomes 1, 7, 13 and 20

Chromosome banding analysis has shown that numerical aberrations, in particular gains of chromosomes 7, 13 and 20, are common in colorectal adenomas but cannot provide reliable information on the size of the abnormal clones in vivo. We examined interphase nuclei from 70 colorectal adenomas, of which 64 had been previously karyotyped, using fluorescence in situ hybridization (FISH) with probes for the pericentromeric regions of chromosomes 1, 7, 13 and 20. Gain of chromosome 7 was seen in 34% of the analyzed adenomas, +13 was seen in 44% and trisomy 20 was found in 32% of the adenomas, verifying that the trisomies are in vivo phenomena. The median proportion of cells with trisomy was larger than 50%. A comparison with the G-banding analysis showed a good correlation between the results yielded by the 2 methods. Based on the clonal size and karyotypic findings, a likely order of events during clonal evolution could be ascribed to each case. More than 1 numerical aberration was detected by FISH analysis in 16 adenomas. In 6 adenomas, a clone with only trisomy 7 was present alongside a clone with additional gain(s) of chromosomes 13 and/or 20. Seven cases had gain of chromosome 13 and/or gain of chromosome 20 in the largest clone, suggesting that a clone with either of these changes was present before the changes in chromosome 7 copy number took place. On the basis of the results of this combined meta- and interphase cytogenetic study, we conclude that gains of chromosomes 7, 13 and 20 are common in colorectal adenomas and that the trisomies usually are present in a large proportion of the cells. They seem to be primary chromosome aberrations in some adenomas, whereas in others they arise secondarily as part of the clonal evolution. Although the first gain usually is of chromosome 7, it is evident that it is the end result of the chromosomal aberrations, not the exact sequence in which they occur, that determines the pathogenetic consequences.

Cytogenetic analysis of colorectal adenomas: karyotypic comparisons of synchronous tumors

The phenotypic progression of colorectal tumors is driven by their step-by-step acquisition of genomic alterations. These pathogenetically important mutations are at the same time markers of tumor clonality. The aim of this study was to describe the clonal relation among synchronous colorectal adenomas. Twenty-four colorectal adenomas from 11 patients were subjected to chromosome banding analysis. Clonal chromosome abnormalities were found in 20 tumors. Recurrent structural rearrangements involved chromosomes 1, 13, 17, and 18. The most common numerical changes were gain of chromosomes 7, 13, 20, and 3 and loss of chromosome 18. Eight adenomas had subclones as evidence of clonal evolution. Similar clones in separate polyps were seen in tumors from 6 patients; these adenomas were always located in the same part of the large bowel. In 2 patients, both with one rectal adenoma and one adenoma in the colon, no karyotypic similarity between the lesions was found. Our findings indicate that whereas close, but macroscopically distinct, synchronous colorectal adenomas usually have a common pathway of progression, perhaps even the same clonal origin, large bowel adenomas at a considerable distance from one another exhibit karyotypic differences, indicating that they arise independently.

Chromosome abnormalities in colorectal adenomas: two cytogenetic subgroups characterized by deletion of 1p and numerical aberrations

Cytogenetic analysis of short-term cultures from 34 benign colorectal polyps, all histologically verified as adenomas, revealed clonal chromosome aberrations in 21 of them. Eight polyps had structural rearrangements, whereas only numerical changes were found in 13. A combination of structural and numerical chromosomal aberrations was found in three polyps. The most common numerical change was gain of chromosome 7, found either as the sole anomaly (five polyps), together with other numerical changes (six polyps), or together with structural rearrangements (two polyps). Other recurrent numerical changes were +20, +13, and monosomy 18, found in six, five, and two adenomas, respectively. Rearrangement of chromosome 1 was the most common structural change. Abnormalities involving 1p were seen in six adenomas, leading to visible loss of material in three. One adenoma had one clone with a large and another with a small 1p deletion. In three adenomas, del(1)(p36) was the only cytogenetic aberration, supporting the authors' previous conclusion that loss of one or more gene loci in band 1p36 is a common early change in colorectal tumorigenesis. Chromosome 8 was involved in structural changes in two adenomas; in one this led to loss of 8p and in the other to gain of 8q. The cytogenetic findings did not correlate in a statistically significant manner with clinicopathologic parameters, such as grade of dysplasia, macroscopic or microscopic adenoma structure, tumor size and location, or the patients' sex and age.

Overrepresentation of 3q and 8q material and loss of 18q material are recurrent findings in advanced human ovarian cancer

In order to define the ability of comparative genomic hybridization (CGH) to detect and map genetic imbalances, we investigated 47 malignant ovarian tumors and 2 ovarian tumors of low malignant potential. The most common genetic changes in order of frequency included DNA gains of chromosome arms 8q (53%), 3q (51%), 20q (43%), 1p (32%), 19q (30%), 1q (28%), 12p (28%), 6p (21%), and 2q (19%). The smallest regions of overrepresentation could be defined in 3q26-qter, 8q23-qter, 1p35-pter, 12p 12, and 6p21-22, respectively. Losses were detected on 18q (23%), chromosome 4 (23%), 13q (17%), and 16q (17%) with the smallest underrepresented regions on 18q22-qter, 13q21, and 16q23-qter. Also, losses of the X chromosome (19%) were detected, correlating with higher ages of the patients. Therefore, some of these X chromosome losses might be due to a well-known aging phenomenon and in these cases will be more preferably lost during cell division and tumor progression. Our findings show that ovarian carcinomas reveal consistent chromosomal abnormalities. Further detailed studies of these regions with specific molecular genetic techniques may lead to the identification of oncogenes and/or tumor suppressor genes playing an important role in the tumorigenesis of ovarian carcinomas.

Deletion of 1p loci and microsatellite instability in colorectal polyps

Previous cytogenetic studies have indicated that a subset of large bowel adenomas have distal 1p deletions. We addressed this question by examining 70 sporadic polyps (63 adenomas, 5 hyperplastic polyps, and 2 polyps of undetermined histology) from 55 patients for alterations at eight loci on the short arm of chromosome 1 and found allelic imbalance (AI) or loss of one allele (LOH) in 14 (20%). The locus most frequently changed was MSI, which maps to 1p33-35. Fluorescence in situ hybridisation with centromeric and telomeric probes for chromosome 1, performed for 11 polyps, did not yield an abnormal number of signals, in accordance with the interpretation that the observed AI and LOH were the result of interstitial deletions in 1p. Whereas allelic imbalance at five other loci (mapping to 5q, 8p, 10p, 11p and 17q) was found less frequently, and then mainly in large (> 2 cm) tumours, the 1p alterations were equally distributed among small (< 1 cm) and large polyps. They were preferentially found in left-side tumours. Instability at microsatellite loci--the mutator phenotype--is demonstrated by shifts in the electrophoretic mobility of normal alleles. The mutator phenotype was first associated with hereditary nonpolyposis colorectal cancer but is also occasionally found in sporadic colorectal carcinomas; however, it is still uncertain when in the adenoma-carcinoma sequence in this type of genomic instability arises. We therefore looked for it at 12 dinucleotide repeat loci and found that seven tumours (six adenomas and one hyperplastic polyp) from seven patients had acquired new alleles not seen in the patients' corresponding normal DNA. Our results suggest that inactivation of a putative suppressor gene distally in chromosome arm 1p is an early event in colorectal tumourigenesis. They also show that microsatellite instability can be detected in large bowel polyps, indicating that this phenomenon, too, probably plays a pathogenic role for some colorectal tumours early in the adenoma-carcinoma sequence.

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 1 abnormal clone was detected in 26 tumors; in 18 of them, the clones were cytogenetically unrelated. The modal chromosome number was near-diploid in 32 tumors and near-triploid to near-tetraploid in 13. Only numerical aberrations were identified in 13 carcinomas, only structural aberrations in 3, and 29 had both numerical and structural changes. The most common numerical abnormalities were, in order of decreasing frequency, gains 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, 7q11, 1p33, 7p22, 7q32, 12q24, 16p13, and 19p13. Frequently recurring aberrations affecting these bands were del(1)(p22), i(8)(q10), i(13)(q10), and add(17)(p11-13). The most common partial gains were from chromosome arms 8q, 13q, and 17q and the most common partial losses from chromosome arms 1p, 8p, 13p, and 17p. A correlation analysis between the karyotype and the clinicopathologic features in our total material, which consists of altogether 153 colorectal carcinomas, including 116 with an abnormal karyotype, showed a statistically significant association (P < 0.05) between the karyotype and tumor grade and site. Carcinomas with structural chromosome rearrangements were often poorly differentiated; well and moderately differentiated tumors often had only numerical aberrations or normal karyotypes. Abnormal karyotypes were more common in rectal carcinomas than in carcinomas situated higher up. Near-triploid to near-tetraploid karyotypes were more than twice as frequent 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 numerical changes and cytogenetically unrelated clones, probably arise through different mechanisms than do tumors located in the distal colon, which more often have complex near-triploid to near-tetraploid karyotypes.

Comparative genomic hybridization, allelic imbalance, and fluorescence in situ hybridization on chromosome 8 in prostate cancer

Due to problems with primary tumor cell culture, conventional cytogenetics has yielded little insightful information on chromosomal alterations in prostate cancer. The primary aim of this study was to define the ability of comparative genomic hybridization (CGH) to detect and map genetic deletions in prostate tumors. A secondary aim was to apply multiple assays to individual tumors as a means of deciphering the mechanisms of genetic alterations in prostate cancer. CGH results were compared with allelic imbalance measurements at 29 distinct loci on chromosome 8 in 18 specimens (17 malignant and 1 benign). CGH detected no changes in cases where all informative PCR/RFLP loci were retained and detected all p arm deletions consisting of at least two loci. We estimate that in this study, the smallest deletions detected by CGH were approximately 20-30 cM. Physical mapping of subchromosomal arm deletions by CGH correlated well with allelic imbalance mapping by PCR/RFLP: The data agreed at 88% of loci on 8p and 92% of loci on 8q. Fluorescence in situ hybridization (FISH) with multiple centromere probes and DNA content flow cytometry (FCM) also was performed on selected specimens. FISH revealed two cases of chromosome 8 aneusomy. In these two cases and three others, CGH showed simultaneous p arm deletion and q arm gain, suggesting isochromosome 8q formation. Together, these data suggested that, simple chromosomal aberrations were responsible for allelic losses on 8p and allelic gains on 8q in a significant number of prostate tumors. We also used CGH to examine relative DNA sequence copy number throughout the genome. Changes frequently associated with 8p loss include gains of 8q and losses of 13q, 16p, 16q, 17p, 17q, 20q, and Y. Cases with 8p loss exhibited five times the number of alterations as did cases without 8p loss.

Clonal karyotypic abnormalities in colorectal adenomas: clues to the early genetic events in the adenoma-carcinoma sequence

Cytogenetic analysis of short-term cultures from colorectal adenomas revealed acquired clonal chromosome aberrations in 14 of 17 tumors. In 4 adenomas, only numerical changes were found, whereas 10 had structural rearrangements. Trisomy 7 was found as the sole change in one of the tumors and together with other numerical changes in another. A +7 was also present in one case with structural aberrations. Other recurrent numerical aberrations were -14 and -18, both found in 2 adenomas with structural karyotypic changes; in addition, one chromosome 14 was lost in one of the tumors with only numerical changes. The chromosome most often involved in structural aberrations was chromosome 1. In 6 cases, the rearrangements led to changes in 1p, always with loss of material. The breakpoints were at 1p32-36. One adenoma had deletion of 1p as the only change. Other chromosomes that were involved in changes in more than 2 cases were chromosomes 8, 13, and 17. These rearrangements typically led to gain of 8q and 13q and loss of 17p. The adenomas with structural abnormalities were generally larger and had a higher degree of dysplasia than did the adenomas with numerical changes only or those with a normal karyotype. All adenomas with a tubulovillous or villous architecture had structural rearrangements. Our findings confirm that a subset of colorectal adenomas exists that have only numerical chromosome aberrations. They also support our previous conclusion that loss of material from distal 1p is an early event in colorectal tumorigenesis, but that other cytogenetic aberrations follow and typically are present already at the adenomatous stage.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of four new gastric cancer cell lines

Four well differentiated gastric adenocarcinoma cell lines from German patients have been established from primary tumors (St 23132, St 3051) and lymph node metastases (St 2474, St 2957). The tumor cells were isolated by enzymatic or mechanical treatment. All four lines grew as solid tumors in nude mice and formed colonies in soft agar. The doubling time of the cells in culture was 25-32 h. Further characteristics of the lines were a considerable chromosomal aneuploidy, (the chromosomal numbers varying from 30-109 with many numerical and structural abnormalities), a stable keratin expression (Ck 8, 18, 19), the expression and secretion of CEA and CA-19-9 and the overexpression of c-myc. The four stomach cancer cell lines described here are not only a useful addition to the small number of existing lines, but also represent ideal tools for studying tumorigenicity of human stomach cancers in vitro and in vivo.

Cytogenetic analysis of 52 colorectal carcinomas--non-random aberration pattern and correlation with pathologic parameters

Cytogenetic analysis of short-term cultures from 52 colorectal carcinomas revealed a normal karyotype in 13 and clonal chromosome aberrations in 39 tumors. In the abnormal group, 13 tumors had simple numerical changes only, whereas 26 had at least one structural rearrangement with or without concomitant numerical changes. The most common numerical abnormalities were, in order of decreasing frequency, +7, -18, -Y, +8, +13 and -14. The most common structural rearrangements affected, again in order of decreasing frequency, chromosomes 8, 1, 6, 7, 17, 3, 11, 13, 14, 16, 2 and 10. The chromosome bands most frequently involved in the structural changes were 8q10, 17p11, 11q13, 8p11, 6q21, 7p15, 7q36, 12q13, 13q10, and 16q13. The most frequent genomic imbalances brought about by the structural rearrangements were losses from chromosome arms 8p, 1p, 6q, 17p, 7p, and 16q, as well as gains of 7q, 8q, 13q, and 11q. A statistically significant (p < 0.05) correlation between the karyotypic pattern and tumor grade was found, with the poorly differentiated carcinomas generally having more massive chromosomal abnormalities.

Deletion mapping of the short arm of chromosome 8 in non-small cell lung carcinoma

Frequent losses of heterozygosity observed at several chromosomal loci in primary lung cancers have indicated the existence of several tumor suppressor genes associated with this type of cancer. We have examined loss of heterozygosity on chromosomal arm 8p in 49 cases of non-small cell lung carcinoma, using 14 restriction fragment length polymorphism markers. Of 42 cases informative with at least one marker, 21 showed allelic loss, including 15 of 32 adenocarcinomas and 5 of 9 squamous cell carcinomas. The frequency of allelic loss on 8p was similar at all clinical stages. Deletion mapping defined a single common region of deletion in these tumors within an 8 cM interval at 8p21.3-p22 flanked by the loci defined by cMSR-32 and cC18-245.

Interstitial deletion of the short arm of chromosome 3 as a primary chromosome abnormality in carcinomas of the breast

Interstitial deletions of the short arm of chromosome 3 were found in short-term cultures of five breast carcinomas (of 41 breast cancers with clonal aberrations analyzed by us during the same period). They were the only clonal structural change in three tumors; in the remaining two, the clone with 3p-coexisted with seemingly unrelated clones that had other structural and numerical aberrations. The deletions were identical, del(3)(p12p14), in four cases. The fifth tumor seemed to have a smaller deletion, interpreted as del(3)(p13p14). Our findings constitute karyotypic evidence that 3p deletions are relatively common in breast carcinomas and concur with the molecular genetic detection of loss of heterozygosity in this chromosome arm. The fact that the deletions were found as solitary changes indicates that loss of genetic information from 3p loci is an early, possibly primary, event in tumorigenesis.

Cytogenetic aberrations in colorectal adenocarcinomas and their correlation with clinicopathologic features

BACKGROUND

Little is known about the karyotypes of colorectal carcinomas and, in particular, about how the cytogenetic findings correlate with clinicopathologic features.

METHODS

Short-term cultures from 49 colorectal adenocarcinomas were analyzed cytogenetically. The karyotypes were correlated with grade, stage, lymphocytic infiltration, and site (using the chi-square test), with patient age and tumor size (using the Student t test), and with survival (using the log-rank or Mantel-Haenszel test).

RESULTS

Normal karyotypes were detected in 17, simple numeric changes in 22, and multiple structural and numeric abnormalities in 10. The most common numeric aberrations were +7, -Y, -18, and -22. The most common structural rearrangements were, in decreasing order of frequency, of chromosomes 1 (eight samples, leading to loss of 1p material in five), 3, 11, 17, 6, 8, 13, and 20. Marked or moderate lymphocytic infiltration was seen significantly less often (P < 0.05) in tumors with complex chromosomal abnormalities than in those with simple anomalies or normal karyotypes. The subset of patients who had tumors with multiple chromosomal abnormalities had a significantly shorter survival time (P < 0.025) than those who had lesions with simple changes or normal karyotypes.

CONCLUSIONS

Loss of 1p material is the most consistent chromosomal change in colorectal carcinomas but probably represents a progressional rather than a primary event. Structural changes of chromosomes 3 and 11 seem to be more common in tumors located in the distal part of the large intestine. The significantly shorter survival time of patients with complex aberrations indicates that the karyotype could be used as a prognostic parameter in patients with colorectal cancer.

Translocations (17;20) in colorectal adenocarcinomas

We describe new recurrent chromosome translocations (17;20) observed in 3 of 19 colorectal tumors. Two of them were identical: der(20)t(17;20)(q21;p12), resulting in the loss of 17(pter-->q21) and the third was a dicentric dic(17;20)(p11;p12). A similar dicentric was described previously in one tumor [1], but we report der(20)t(17;20)(q21;p12) for the first time.

t(13q;17p) and del(5q): possibly specific changes in Chinese patients with colorectal cancers

Cytogenetic study of 18 colorectal carcinomas confirmed the extensive heterogeneity and the complexity of the karyotypic picture in this type of tumor. Karyotypic analysis showed that chromosomes 17p and 5q, in both numerical and structural aspects, were the most frequently involved chromosomes and prone to losses. The most common structurally rearranged forms were translocations of 17p with other chromosomes, especially t(13q;17p), which constituted over 50% of all 17p rearrangements, and an interstitial deletion of 5q that made up as much as 73% of all structural abnormalities of 5q. According to the results, we conclude that chromosomes 17 and 5 may play important roles in the evolution of colorectal cancer and t(13q;17p) and del(5q) may be possibly specific to Chinese patients with colorectal cancer.

Direct chromosome analysis of seven primary colorectal carcinomas

Chromosome studies were performed on direct preparations of seven cases of primary colorectal carcinomas. Two cases had relatively simple chromosome changes: 48,XY,+8,+21/51, XY,+8,+9,+10,+i(17q),+21, and 47,der(X)t(X;14)(q11;q11)-Y,t(6;18)(p22;q24)+7,+8,der(19)t (19;?)(q13;?). The five others had complicated deletions and translocations; 1p- was noted in five cases, and i(17q) was noted in three cases.

Deletions in the short arm of chromosome 8 are present in up to 90% of human colorectal cancer cell lines

Cytogenetic analyses of human colon cancer cells have revealed non-random deletions in chromosome arm 8p, among other chromosomal changes. By using 8p-specific DNA probes we could identify allelic loss in 87% of colon cancer cell lines. Corresponding analyses in direct preparations of colon tumor tissues revealed a minimal value of 40% of allelic loss but were obstructed in many instances by contaminating normal tissue. These findings add to the number of non-random genetic alterations occurring during colon carcinogenesis.

Cytogenetic, oncogenetic, and histopathologic characteristics of colorectal carcinomas with 17p abnormalities

From a total of 65 colorectal adenocarcinomas studied by cytogenetic methods, 33 were selected for the present study; in addition to other karyotypic anomalies, these 33 showed a loss of the short arm of chromosome 17. This loss was either the result of a deletion or rearrangement, or caused by the loss of a whole chromosome 17. The 17p- tumors were characterized by a high grade of karyotypic abnormality including a high incidence of cases with double minutes. A gain of chromosomes 2, 7, 19, and 20, and the loss of chromosome 18 and the Y-chromosome were the most frequent numerical anomalies associated with 17p-, as were structural changes of chromosomes 1 and 5. The most impressive difference in the pattern of proto-oncogene over-expression between the 17p- tumors and those without this anomaly was the significantly increased frequency of cases with c-erbB over-expression. Some significant, but also loose, associations were found between cytogenetic/oncogenetic and histopathologic or clinical features of these tumors. The patterns of genetic changes in cells of colorectal carcinomas may thus reflect the potential of the future development, rather than the present clinical features, of the respective tumor. Therefore, the character of the change seems to be more prognostic than diagnostic.

Involvement of chromosome 5 in large bowel cancer

We present here 3 of 30 cases of large bowel cancer cytogenetically studied, with deletion of chromosome 5. One of them presented a terminal deletion and the other two an interstitial deletion of chromosome 5q. In all three cases the segment 5q12-22 was deleted. Our findings may show that the segment 5q12-22 is important for a subgroup of colorectal cancers.

Numerical chromosome changes in 165 malignant tumors. Evidence for a nonrandom distribution of normal chromosomes

The numbers of normal copies of each of the chromosomes in representative karyotypes from 165 malignant tumors of the bladder, breast, cervix, colorectum, and testis studied in this laboratory or described in the literature were assessed to determine whether particular chromosomes were over- or underrepresented. For each chromosome, the mean number of copies was expressed as a percentage of the number expected on the basis of the total number of chromosomes in the karyotypes. The most highly represented autosomes in the tumors as a whole were, in descending order of frequency, numbers 7, 20, 12, 19, 21, and 3, while those most underrepresented were numbers 10, 1, 4, 5, 14, 17, 11, and 18. In tumors of males, the Y tended to be underrepresented. The X was highly represented in the testicular tumors (there were usually two or more copies) and in colorectal tumors of males, but not in the other tumor categories studied. For the tumors as a whole, statistically significant differences could be demonstrated between pairs of autosomes that were at opposite ends of the frequency range. Differences between tumors at the different sites studied were not demonstrable. It is suggested that the determination of the number of normal copies of chromosomes, i.e., whether there are more or fewer than expected, may usefully complement observations on structural changes by reflecting the presence of oncogenes and tumor-suppressor genes, respectively. It may also point to chromosomes that are involved in significant genic changes in which cytogenetic observations on structural changes are equivocal.

Trisomy 7 in short-term cultures of colorectal adenocarcinomas

Cytogenetic analysis of short-term cultures from six adenocarcinomas of the colon revealed trisomy 7 as a recurrent clonal chromosomal abnormality. In three tumors, +7 was the sole change. In the fourth carcinoma, two aberrant clones with simple numerical aberrations were detected; one with +7 and one with +3. Tumors 5 and 6 both displayed two completely different abnormal clones; one had numerous numerical and structural abnormalities and thus was undoubtedly representative of the cancer parenchyma, and the other had only +7. The karyotypic differences between the coexisting clones in the latter two cases seem to argue against an evolutionary scenario in which the karyotypically more complex clones have evolved from the clones carrying trisomy 7 only. Furthermore, in tumor 6 the metaphases with trisomy 7 were found in colonies of fibroblast-like cells whereas those with a large number of abnormalities grew in colonies of epithelial-like cells. The combined results indicate that mitoses with trisomy 7 as the sole chromosomal change do not represent the neoplastic parenchyma of colorectal adenocarcinomas.

Karyotype peculiarities of human colorectal adenocarcinomas

The data of the chromosome abnormalities in 15 colorectal tumors are presented. Rearrangements of the short arm of chromosome 17, leading to deletions of this arm or its part were noted in 12 tumors; in 2 other cases, one of the homologs of pair 17 was lost. The losses of at least one homolog of other chromosomal pairs were also found: chromosome 18, in 12 out of 13 cases with fully identified numerical abnormalities; chromosome 5, in 6 tumors; chromosome 21, in 5 cases; chromosomes 4, 15, and 22, in 4 cases each. Additional homologs of pair 20 were observed in 6 tumors, extra 8q was found in 5 tumors, and extra 13q in 6 cases. Rearrangements of the short arm of chromosome 1 and the long arm of chromosome 11 characterized 6 tumors each. The data recorded in our series differ from the data of other authors in two respects: the high incidence of the loss of sex chromosomes and the rearrangements of the long arm of chromosome 9. X chromosomes were missing in 4 out of 7 tumors in females, and Y chromosomes were absent in 5 out of 8 tumors in males. The long arm of chromosome 9 was rearranged in 8 cases, in 5 of them the breakpoint being at 9q22. Cytological manifestations of gene amplification (double minutes or multiple microchromosomes) were noted in 6 tumors.

Isochromosome (8q) in four patients with adenocarcinoma of the lung

We report an isochromosome, i(8q), in combination with many other cytogenetic changes in tumor cells from four patients with lung cancer. In each case, the tumor subtype was adenocarcinoma. This isochromosome has not been identified in primary tumors from patients with other histological types of lung cancer. Among the few previously reported cytogenetic analyses of pulmonary adenocarcinomas, i(8q) has been observed in four additional patients. Therefore, i(8q) represents a recurring change in this specific type of lung cancer. In addition to i(8q), tumor cells from each of our four patients had different abnormalities of 17p, and two patients had alterations of 3p as well.

Chromosome studies in eleven colorectal tumors

Cytogenetic analysis is presented on seven freshly derived colorectal tumors and four established cell lines (SW 742, SW 480, SW 948, and HT 29). No chromosome change was common to all tumors, although previous nonrandom findings were confirmed. Single chromosome abnormalities were identified in two cases, 47,XX,+i(7p) and 46,XX,-17,+der(17),t(17;?)(p;?), and their relevance to tumor origin and development is discussed. The association of i(8q) with tumors of the rectosigmoidal region is confirmed, and it is suggested that other rearrangements involving loss of 8p may have the same association. Abnormalities resulting in loss of 20p and duplication of 20q, not previously reported as a nonrandom change, were seen in seven out of 11 cases.