Recurrent deletions of chromosomes 11q and 3p in anal canal carcinoma

John Cunningham virus T-antigen expression in anal carcinoma

BACKGROUND

Anal carcinoma is thought to be driven by human papillomavirus (HPV) infection through interrupting function of cell regulatory proteins such as p53 and pRb. John Cunningham virus (JCV) expresses a T-antigen that causes malignant transformation through development of aneuploidy and interaction with some of the same regulatory proteins as HPV. JCV T-antigen is present in brain, gastric, and colon malignancies, but has not been evaluated in anal cancers. The authors examined a cohort of anal cancers for JCV T-antigen and correlated this with clinicopathologic data.

METHODS

Archived anal carcinomas were analyzed for JCV T-antigen expression. DNA from tumor and normal tissue was sequenced for JCV with viral copies determined by quantitative polymerase chain reaction and Southern blotting. HPV and microsatellite instability (MSI) status was correlated with JCV T-antigen expression.

RESULTS

Of 21 cases of anal cancer (mean age 49 years, 38% female), 12 (57%) were in human immunodeficiency virus (HIV)-positive individuals. All 21 cancers expressed JCV T-antigen, including 9 HPV-negative specimens. More JCV copies were present in cancer versus surrounding normal tissue (mean 32.54 copies/μg DNA vs 2.98 copies/μg DNA, P = .0267). There was no correlation between disease stage and viral copies, nor between viral copies and HIV-positive or -negative status (28.7 vs 36.34 copies/μg DNA, respectively, P = .7804). In subset analysis, no association was found between JCV T-antigen expression and HPV or MSI status.

CONCLUSIONS

Anal carcinomas uniformly express JCV T-antigen and contain more viral copies compared with surrounding normal tissue. JCV and its T-antigen oncogenic protein, presumably through interruption of cell regulatory proteins, may play a role in anal cancer pathogenesis.

Cancer risk in patients with constitutional chromosome deletions: a nationwide British cohort study

The finding of increased risks of specific cancers in individuals with constitutional deletions of chromosomes 11p and 13q led to the discovery of cancer predisposition genes at these locations, but there have been no systematic studies of cancer risks in patients with constitutional deletions, across the chromosome complement. Therefore, we assessed cancer incidence in comparison with national cancer incidence rates in a follow-up of 2561 patients with constitutional autosomal chromosome deletions diagnosed by microscopy or fluorescence in situ hybridisation in Britain during the period 1965-2002. Thirty cancers other than non-melanoma skin cancer occurred in the cohort (standardised incidence ratio (SIR)=2.4, 95% confidence interval (CI) 1.6-3.5). There were significantly increased risks of renal cancer in persons with 11p deletions (SIR=1869, 95% CI 751-3850; P=4 x 10(-21)), eye cancer with 13q deletions (SIR=1084, 95% CI 295-2775; P=2 x 10(-11)), and anogenital cancer with 11q deletions (SIR=305, 95% CI 63-890; P=3 x 10(-7)); all the three latter cancers were in the 11 subjects with 11q24 deletions. The results strongly suggest that in addition to suppressor genes relating to Wilms' tumour risk on 11p and retinoblastoma on 13q, there are suppressor genes around 11q24 that greatly affect anogenital cancer risk.

Anal intraepithelial neoplasia and other neoplastic precursor lesions of the anal canal and perianal region

Anal cancer is rare and this helps to explain why anal pre-neoplastic conditions are poorly understood, especially with regard to their natural history and management. Anal intraepithelial neoplasia is closely linked to human papillomavirus infection and is particularly common in homosexuals and in immunosuppressed patients, especially those with HIV/AIDS. The high regression rates of low-grade anal intraepithelial neoplasia may simply reflect inconsistent pathologic reporting. Higher grades of anal intraepithelial neoplasia may remain static for long periods of time in immunocompetent patients, but those with HIV/AIDS show early and rapid malignant transformation. In general, most anal pre-neoplastic conditions are best diagnosed by biopsy and treated by surgical excision, although local recurrence is a problem. In anal Paget's disease, it is important to ascertain, at the time of diagnosis, whether it is due to a primary in-situ apocrine-type of neoplasia of the anus or if the disease is secondary to an invasive primary carcinoma of the rectum.

Human papillomavirus infection and tumours of the anal canal: correlation of histology, PCR detection in paraffin sections and serology

Human papillomavirus infection is an important etiological factor in squamous cell carcinoma of the anus (SCCA). Different histological variants of anal carcinomas displaying squamous differentiation, previously classified as separate tumours, were recently reclassified as SCCA by the WHO. In our recent study the presence of HPV was detected by PCR in biopsy specimens of 42 different anal tumours, including SCCA and its histological variants (n=22), adenocarcinomas (n=5), tubulovillous adenomas (n=5) and anal condylomas (n=10). HR HPV16 (high risk - HR) was detected in 18 of SCCA specimens (81.8%). All histological variants, i.e. tumours with basaloid, squamous and mixed histological patterns, were represented among the HPV-positive cancers. Four tumours (18.2%) were HPV negative. Low-risk (LR) HPV types were not detected within the SCCA group. HPV16 was identified in one adenocarcinoma, while four cases were HPV negative. Two adenomas showed presence of HPV16; one showed simultaneous positivity for HPV33. The remaining three tumours were HPV negative. Seven anal condylomas (70%) were LR HPV 6 and/or 11 positive, while three were HPV negative. The presence of HR HPV types was not observed in anal condylomas. Our results provide further evidence in support of the etiological role of HR HPV infection in the development of SCCA regardless of its histological appearance.

Molecular biology of squamous cell carcinoma of the anus

BACKGROUND

Squamous cell carcinoma of the anal canal provides a model for studying the contribution of human papillomavirus (HPV) and human immunodeficiency virus (HIV) infection to the development of neoplasia. This paper reviews the existing literature relating to the molecular biology of anal squamous cell carcinoma and proposes a theory of pathogenesis.

METHODS

A Medline literature search was performed to identify English articles on the pathogenesis of squamous cell carcinoma of the anus; further articles were obtained from the references quoted in the literature initially reviewed.

RESULTS

HPV infection and subsequent HPV DNA integration are necessary, but not sufficient, to cause cancer progression. Loss of heterozygosity at 11q23 is the most consistent genomic change observed. Loss of heterozygosity at 17p, 18q and 5q is frequently observed in tumours of HIV-negative patients, but not in those of HIV-positive patients. Current data suggest that mutations in p53, DCC and APC tumour suppressor genes contribute to the stepwise progression of anal squamous cell carcinoma in immunocompetent individuals.

CONCLUSION

In comparison with immunocompetent individuals, HIV-positive patients have persistent HPV infection in the anal canal. In this population, microsatellite instability, rather than chromosomal instability, appears to be a preferred pathway for rapid progression towards invasive carcinoma.

Prognostic factors in anal carcinoma

The pathologist's role in the evaluation of patients with anal squamous carcinoma is now largely restricted to establishing the diagnosis on small biopsies. Staging is performed by imaging techniques and grading is uncertain as the biopsy may not be representative of the whole tumour. Histological subtyping is unreliable and has not been proven to be of prognostic significance. A considerable effort resulting in nearly 50 reports on cytogenetic, flow cytometric, immunohistochemical and other investigations has given new insight into pathogenesis but little guidance with regard to the individual prognosis or choice of treatment. It is concluded that future research should concentrate on larger, probably multicentre series using standardised methods and criteria for evaluation.

Loss of heterozygosity and HIV infection in patients with anal squamous-cell carcinoma

PURPOSE

This study was designed to determine whether loss of heterozygosity and/or microsatellite instability correlate with HIV infection and tumor recurrence after chemoradiation therapy in patients with squamous-cell carcinoma of the anus.

BACKGROUND

The molecular mechanisms leading to the progression of HIV-related squamous-cell carcinoma of the anus are poorly understood. In particular, genetic alterations responsible for resistance to chemoradiation have important clinical and functional implications.

METHODS

In a case-control study, we analyzed normal and tumor DNA samples of four patients with squamous-cell carcinoma of the anus who were successfully treated with chemoradiotherapy and four patients with radio-resistant squamous-cell carcinoma of the anus who required abdominoperineal resection for local recurrence. To determine the presence of microsatellite instability, we used the reference panel of five pairs of microsatellite primers recommended for colorectal cancer specimens. These include the microsatellite markers BAT25, BAT26, D5S346 (APC), D2S123 (hMSH2), and D17S250 (P53). In addition, we used microsatellite markers for loss of heterozygosity analyses that were tightly linked to tumor suppressor genes. These included D3S1611 (hMLH1), D17S513 (P53), D18S46 and 18qTA (DCC/SMAD4), D5S107 (APC), and CA5 (hMSH2).

RESULTS

There were two HIV-positive and two HIV-negative patients in each group. Three HIV-positive patients (one in the chemoradiotherapy group and two in the nonchemoradiotherapy group) demonstrated loss of heterozygosity. In the chemoradiotherapy group, one HIV-positive patient demonstrated loss of heterozygosity at the hMLH1 locus. In the nonchemoradiotherapy group, two HIV-positive patients exhibited a total of four instances of loss of heterozygosity. One tumor had loss of heterozygosity at hMSH2 and DCC/SMAD4; another tumor demonstrated loss of heterozygosity at hMSH2 and APC. Microsatellite instability-low was found in two HIV-positive patients. No instances of loss of heterozygosity and microsatellite instability were detected in HIV-negative patients.

CONCLUSION

Loss of heterozygosity and microsatellite instability, which reflect inactivation of tumor-suppressor genes and genomic instability, occur with increased frequency in HIV-associated squamous-cell carcinoma. These data demonstrate for the first time evidence of loss of heterozygosity at the APC and DCC/SMAD4 gene loci in anal carcinoma. Although the findings presented here need to be expanded in a larger study, the recurrent loss of heterozygosity at D2S123, which was demonstrated in HIV-positive patients with radio-resistant squamous-cell carcinoma of the anus, is notable.

A recurrent pattern of chromosomal aberrations and immunophenotypic appearance defines anal squamous cell carcinomas

Squamous cell carcinomas of the anus are rare neoplasias that account for about 3% of large bowel tumours. Infections with human papillomaviruses are frequently detected in these cancers, suggesting that pathogenic pathways in anal carcinomas and in carcinomas of the uterine cervix are similar. Little is known regarding recurrent chromosomal aberrations in this subgroup of squamous cell carcinomas. We have applied comparative genomic hybridization to identify chromosomal gains and losses in 23 cases of anal carcinomas. A non-random copy number increase of chromosomes 17 and 19, and chromosome arm 3q was observed. Consistent losses were mapped to chromosome arms 4p, 11q, 13q and 18q. A majority of the tumours were aneuploid, and most of them showed increased proliferative activity as determined by staining for Ki-67 antigen. p53 expression was low or undetectable, and expression of p21/WAF-1 was increased in most tumours. Sixteen cancers were satisfactorily tested for the presence of HPV by consensus L1-primer polymerase chain reaction; nine were HPV positive, of which eight were positive for HPV 16.

Deletions of the short arm of chromosome 3 in solid tumors and the search for suppressor genes

The concept that cells can become malignant upon the elimination of parts of chromosomes inhibiting cell division dates back to Boveri in 1914. Deletions occurring in tumor cells are therefore considered a first indication of possible locations of tumor suppressor gene. Approaches used to localize and identify the paradigm of tumor suppressors, RB1, have also been applied to localize tumor suppressor genes on 3p, the short arm of chromosome 3. This review discusses the methodological advantages and limitations of the various approaches. From a review of the literature on losses of 3p in different types of solid tumors it appears that some tumor types show involvement of the same region, while between others the regions involved clearly differ. Also discussed are results of functional assays of tumor suppression by transfer of part of chromosome 3 into tumor cell lines. The likelihood that a common region of deletions would contain a tumor suppressor is strongly enhanced by coincidence of that region with a chromosome fragment suppressing tumorigenicity upon introduction in tumor cells. Such a situation exists for a region in 3p21.3 as well as for one or more in 3p12-p14. The former region is considered the location of a lung cancer suppressor. The same gene or a different one in the same region may also play a role in the development of other cancers including renal cell cancer. In the latter cancer, there may be additional roles of the VHL region and/or a 3p12-p14 region. The breakpoint region of a t(3;8) originally found to be constitutively present in a family with hereditary renal cell cancer now seems to be excluded from such a role. Specific genes on 3p have been suggested to act as suppressor genes based on either their location in a common deletion region, a markedly reduced expression or presence of aberrant transcripts, their capacity to suppress tumorigenicity upon transfection in to tumor cells, the presumed function of the gene product, or a combination of several of these criteria. A number of genes are evaluated for their possible role as a tumor suppressor according to these criteria. General agreement on such a role seems to exist only for VHL. Though hMLH1 plays an obvious role in the development of specific mismatch repair-deficient cancers, it cannot revert the tumor phenotype and therefore cannot be considered a proper tumor suppressor. The involvement of VHL and MLH1 also in some specific hereditary cancers allowed to successfully apply linkage analysis for their localization. TGFBR2 might well have a tumor suppressor function. It does reduce tumorigenicity upon transfection. Other 3p genes coding for receptor proteins THRB and RARB, are unlikely candidates for tumor suppression. Present observations on a possible association of FHIT with tumor development leave a number of questions unanswered, so that provisionally it cannot be considered a tumor suppressor. Regions that have been identified as crucial in solid tumor development appear to be at the edge of synteny blocks that have been rearranged through the chromosome evolution which led to the formation of human chromosome 3. Although this may merely represent a chance occurrence, it might also reflect areas of genomic instability.

A case of isodicentric 7p as sole abnormality in a patient with acute myeloid leukemia

The detection of isochromosomes in the leukemias and in solid tumors has been well described in the literature, the most common being the i(17q), which is found in the blast crisis of CML and terminal stages of acute myeloid leukemia. Reports of isochromosome 7 have, however, been less well represented, particularly isochromosomes of the short arm of chromosome 7, which represent approximately 1% of all reported isochromosomes in neoplasia. We present here a case report of an elderly female patient with AML-M2 who manifested an idic(7p) in the majority of her bone marrow cells. Fluorescence in situ hybridization (FISH) studies with both centromere-7--and chromosome-7--specific DNA probes verified the diagnosis of idic(7p). To the best of our knowledge, this is the first report of this type of leukemia with an acquired idic(7p) as the sole cytogenetic abnormality.

Allelic imbalance in gastric cancer: an affected site on chromosome arm 3p

In order to detect regions of DNA containing tumor suppressor genes involved in the development of gastric cancer, we performed an allelotype study on 78 gastric adenocarcinomas from a population composed largely of Texan Hispanics and Anglos, two ethnic groups that have a ratio of incidence rates of gastric cancer of approximately 2:1. In total, 42 microsatellite markers were employed, which detected at least one site per arm of each autosome in the human genome. These included several markers linked to known tumor suppressor genes (TP53, APC, DCC, RB1, and BRCA1). Sites showing quantitative allelic imbalance (AI) greater than 30% were located on 3p (36%), 11q (31%), 12q (38%), 13q (33%), 17p near TP53 (74%), and 17q near BRCAI (32%). Among the 22% of cases showing microsatellite instability (MI), a subset (4 of 17) showed instability at 59% or more of sites tested. No ethnic bias was detected in cases showing MI or in cases with AI at sites with rates of AI above 30%. Tumors of the intestinal subtype were significantly more likely than diffuse tumors to show AI at DI3S170 (P = 0.01). A deletion map of chromosome arm 3p was prepared for tumors with AI at D3S1478. These data indicate that a tumor suppressor gene on chromosome arm 3p is involved in the development of a subset of gastric cancers.

Loss of chromosome 3p arm differentiating tumorigenic from non-tumorigenic cells derived from the same SV40-transformed human mammary epithelial cells

After immortalization of human normal mammary epithelial cells by replication-defective SV40 genome integration, 2 cultures were developed independently. Both had the same integration site, in band 9q21, but rapidly diverged karyotypically. After a few passages, one, designated SC2T2, exhibited near-diploid (a) and the other, designated SL2T2, near-tetraploid (b) karyotypes. The simplest formulas were 44, X, -X, der(3;22) (q10;q10), der(4) t(4;9)(q34;q12), +8, +9, add(13)(p1), der(19) t(8;19)(q21;p13.3), add(22)(p1) for karyotype (a) and 93, XXXX, add(1)(q12), add(11)(q13), +20 for karyotype (b). A number of alterations were further acquired with passages. Both cell cultures were tumorigenic, but their efficiency of grafting in nude mice largely differed: it was low for SL2T2 and high for SC2T2 cultures. All cultures of the xenografted tumors, obtained from either SL2T2 or SC2T2, exhibited the same clonal anomalies as those characterizing karyotype (a). It was concluded that only cells with karyotype (a) were tumorigenic, and that the difference in the tumorigenic potential of cultures SC2T2 and SL2T2 was related to their richness in cells with this karyotype. The comparison of the various karyotypes, together with data obtained in other cell types transformed by SV40, suggests that the acquisition of tumorigenicity in S2T2 mammary epithelial cells may be related to the loss of chromosome 3p arm.

Malignant anal tumours

Anal tumours represent 5 per cent of anorectal cancers and exist as two clinical entities: tumours of the anal canal and those of the anal margin. Smoking and sexual behaviour, particularly homosexual anal intercourse, are important aetiological factors. This association is related to anal warts and human papillomavirus infection, notably type 16, which is found in around 70 per cent of warts. Symptoms are non-specific and are frequently attributed to benign conditions. Rectal examination reveals a characteristically infiltrating lesion and any suspicious anal area should be biopsied. There are two histological types. Squamous carcinoma comprises approximately 95 per cent of anal tumours and includes the 35 per cent of tumours derived from the anal transition zone (cloacogenic tumours), containing a mixture of squamous and mucinous elements. The remaining 5 per cent of anal tumours are adenocarcinoma. Squamous cell tumours of the anal canal are probably best treated using radiotherapy (with chemotherapy) as complete response rates, 5-year survival rates, and incidences of normal sphincter function and significant toxicity are around 80, 70, 75 and 20 per cent respectively. Treatment failures may be salvaged by surgery. The 5-year survival and local recurrence rates for radical surgery are around 60 and 25 per cent respectively; there are few indications for local excision. In contrast, 60 per cent of anal margin tumours are suitable for local excision, the 5-year survival rate being in excess of 80 per cent. Combining radiotherapy with surgery may give additional benefit. Current randomized controlled trials should further clarify the relative merits and demerits of the treatment options.

[Cancer of the anal canal; role of radiotherapy and combinations of chemotherapy and radiotherapy]

Carcinoma of the anal canal is a rare disease, more common in women than in men. The mean age distribution at presentation is about 60 years. The natural history is mainly loco-regional, distant metastases being uncommon. Histologically, most cancer are of the squamous cell type of different keratinization. The pre treatment evaluation is mainly performed by methodical clinical examination. There is no widely accepted staging system for these tumours. Three statistically significant prognostic factors are admitted: tumour size, regional nodal involvement and histological grade. The french school (Tenon, Institut Gustave Roussy, Institut Curie, Lyon) and the experience at the "Princess Margaret Hospital" at Toronto have shown that irradiation of these tumours is an adequate therapy. In Europe, irradiation has always played a more important role in the therapy of these tumours, than in North America where surgery was often preferred as the initial therapy. With the introduction of combined modality treatment, the use of pre-operative concomitant radiochemotherapy, in North America, has again changed the treatment policy towards a conservative radiotherapeutic approach. The present study analyses the modalities and the results from radiation therapy alone and the preliminary results from concomitant irradiation and chemotherapy.

11q deletions in human colorectal carcinomas: cytogenetics and restriction fragment length polymorphism analysis

Deletions and/or allelic losses of a portion of the long arm of chromosome 11 were discovered by cytogenetic and restriction fragment length polymorphism analyses in 23 of 39 (59%) informative cases of colorectal carcinoma. By comparing the patterns of loss of heterozygosity and chromosome rearrangements in different patients, we could map a common target region to 11q22-23. This region may contain a tumor suppressor gene, the inactivation of which may be involved in the development of tumors of the large intestine. The subgroup of malignancies with 11q alterations seemed to be enriched by tumors that were located in the rectum, that were Dukes' stage A, and that were well differentiated and mucin producing.

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.

Anal cancers. Squamous and melanoma

The total experience at Memorial Sloan-Kettering Cancer Center with two types of anal cancers--squamous and malignant melanoma--is reviewed. The squamous type is much more common, and its anatomic distinction between that of the anal margin and the anal canal is important in its respective clinical and surgical management. The historical, purely surgical management of canal lesions has evolved into the current chemoirradiation management, followed by the surgical approach with improvement of the 5-year survival rate and salvage of rectums. Malignant melanoma, which is the much rarer anal cancer, is still occasionally salvageable, with the use of standard abdominoperineal resection.

Cytogenetic studies of eight squamous cell carcinomas of the head and neck. Deletion of 7q, a possible primary chromosomal event

Cytogenetic analysis was performed on the metaphase spreads obtained from primary cultures of eight squamous cell carcinomas (SCCa) of the head and neck. Despite a variety of tumor sites and clinical stages, four of eight tumors studied showed the same interstitial deletion of a portion of the q arm of chromosome 7, i.e., del(7)(q22q34). In one tumor, this was the sole chromosome abnormality present. Three tumors showed multiple chromosome rearrangements, including deletion at 7q. Three tumors showed multiple rearrangements but did not have del(7q). One tumor had an apparently, normal karyotype. The implications for del(7q) as a primary chromosomal event in SCCa are discussed.

Complementation of a DNA repair deficiency in six human tumor cell lines by chromosome 11

Human tumor cells, after x-irradiation during the G2 phase of the cell cycle, show an abnormally high frequency of persistent chromatid breaks and gaps resulting from deficient DNA repair. Addition of a single human chromosome 11 from normal fibroblasts by micro-cell fusion to cell lines from six different tumors resulted in efficient repair of the radiation-induced damage to the level in normal cells. For one of the cell lines, addition of the long arm of chromosome 11 was sufficient to restore repair efficiency. In four of the six tumor lines, restoration of efficient DNA repair by chromosome 11 was associated with tumor suppression in nude mice. These results suggest that chromosome 11 carries a DNA repair gene or genes that complement the repair deficiency of tumor cells and that this gene for at least one tumor is localized to the long arm.

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.

Translocation (X;12)(q27;q14) in a lipoma

Cytogenetic analysis by short-term culture of a lipoma from the posterior neck region of a 63-year-old man showed a t(X;12)(q27;q14) as the sole chromosomal abnormality. Rearrangement of band 12q14 is nonrandom in lipomas, although its involvement with a sex chromosome has not been reported earlier.

Recurrent chromosome aberrations in human lung squamous cell carcinomas

Cytogenetic study of seven cases of previously untreated lung squamous cell carcinomas (SQC) is reported. Chromosome numbers vary from 38 to 538, with a majority of hypotriploid karyotypes with complex rearrangements. The numbers of recurrent imbalances were evaluated in considering the average number of chromosomes or chromosome segments in each analyzed metaphase and for each case. In decreasing order of frequency, deficiencies for 3p, 5q, 8p, Y, 5p, 10p, 13, and, to a lesser degree, for 8q, 9, 10q, 11pter, 14, 15, and 21 were observed; the excesses principally involve 1q, 3q, and 7q. In three tumors, homogeneously staining regions were observed at various chromosome sites. Most chromosome rearrangements occurred after breakage in constitutive heterochromatin, and no recurrent breakpoints were found in euchromatin except 11p15. The major consequences of these anomalies may be chromosomal imbalances, leading to hemizygosity and perhaps related to gene dosage, rather than to alterations of genes.

Current status--perianal and anal canal neoplasms

A large variety of neoplasms are found in the anal canal and perianal region. Most are distinctly uncommon and may, therefore, pose the question of suitable therapy. For some neoplasms, the treatment of choice is clear cut, while for others it is controversial. Certainly for squamous cell carcinoma of the anal canal, there has been a major rethinking of the treatment of choice. This review highlights the types of lesions found in the anal region and the current status regarding their appropriate treatment.

Frequent rearrangement of chromosomal bands 1p22 and 11q13 in squamous cell carcinomas of the head and neck

We report the finding of clonal structural chromosome abnormalities in short-term cultures from 15 squamous cell carcinomas of the head and neck region. When the distribution of chromosomal breakpoints in these 15 tumors and in the 16 head and neck carcinomas previously described are assessed, a marked clustering is seen at bands 1p22 and 11q13, which are rearranged in eight and nine tumors, respectively. No other band was involved in aberrations in more than five tumors. Cytogenetic evidence of gene amplification was seen in four tumors, three times in the form of homogeneously staining regions (twice located in 11q13), and in one tumor as double minutes. Among the candidate genes for such amplification are BCLI, INT2, and HSTI, all of which map to 11q13, and NRAS, which maps to 1p22. All these oncogenes have previously been shown to be amplified in subsets of head and neck carcinomas. We conclude that bands 1p22 and 11q13 are nonrandomly involved in chromosomal rearrangements in head and neck carcinomas and suggest that activation of oncogenes located in these bands may proceed via cytogenetic mechanisms.

Marker chromosome stability associated with neoplastic transformation of human uroepithelial cells

Chromosome studies were performed on three independently derived tumor cell lines established from carcinomas induced in nude mice after innoculation of SV40 immortalized human uroepithelial cells that had been treated with methylcholanthrene. Tumor 1 was an undifferentiated carcinoma, while tumors 7 and 9 were both squamous carcinomas. After six to eight passages in vitro the tumor cells were each reinoculated into other nude mice to yield secondary tumors (1.1 and 7.1). Chromosome studies on both primary and secondary tumors demonstrated the same distinctive chromosome markers. Tumors 1 and 1.1 shared the same histopathology in addition to the same modal chromosome number and identical chromosomal duplications and deficiencies; the same was true of tumors 7 and 7.1. Tumor 9, which did not yield a secondary tumor, nevertheless showed the same chromosome pattern in different passages. The stability of the characteristic marker chromosomes in the three tumor cell lines distinguishes these malignant lines from the nonmalignant SV40 transformed parent line from which the three tumors derived because the parent line was characterized by extreme marker instability. This suggests that the stable marker chromosomes that characterize the tumor cell lines may be critical for their tumorigenicity, and that evolution of an adaptive neoplastic genome may select for cytogenetic stability as long as there are no new selective pressures.