Cytogenetic findings in cervical carcinoma. A statistical approach

Automated detection and analysis of fluorescent in situ hybridization spots depicted in digital microscopic images of Pap-smear specimens

Fluorescence in situ hybridization (FISH) technology has been widely recognized as a promising molecular and biomedical optical imaging tool to screen and diagnose cervical cancer. However, manual FISH analysis is time-consuming and may introduce large inter-reader variability. In this study, a computerized scheme is developed and tested. It automatically detects and analyzes FISH spots depicted on microscopic fluorescence images. The scheme includes two stages: (1) a feature-based classification rule to detect useful interphase cells, and (2) a knowledge-based expert classifier to identify splitting FISH spots and improve the accuracy of counting independent FISH spots. The scheme then classifies detected analyzable cells as normal or abnormal. In this study, 150 FISH images were acquired from Pap-smear specimens and examined by both an experienced cytogeneticist and the scheme. The results showed that (1) the agreement between the cytogeneticist and the scheme was 96.9% in classifying between analyzable and unanalyzable cells (Kappa=0.917), and (2) agreements in detecting normal and abnormal cells based on FISH spots were 90.5% and 95.8% with Kappa=0.867. This study demonstrated the feasibility of automated FISH analysis, which may potentially improve detection efficiency and produce more accurate and consistent results than manual FISH analysis.

Detection of chromosomal aberrations by fluorescence in situ hybridization in cervicovaginal biopsies from women exposed to diethylstilbestrol in utero

Epidemiologic studies have associated estrogens with human neoplasms such as those in the endometrium, cervix, vagina, breast, and liver. Perinatal exposure to natural (17beta-estradiol [17beta-E(2)]) and synthetic (diethylstilbestrol [DES]) estrogens induces neoplastic changes in humans and rodents. Previous studies demonstrated that neonatal 17beta-E(2) treatment of mice results in increased nuclear DNA content of cervicovaginal epithelium that precedes histologically evident neoplasia. In order to determine whether this effect was associated with chromosomal changes in humans, the frequencies of trisomy of chromosomes 1, 7, 11, and 17 were evaluated by the fluorescence in situ hybridization (FISH) technique in cervicovaginal tissue from 19 DES-exposed and 19 control women. The trisomic frequencies were significantly elevated in 4 of the 19 (21%) DES-exposed patients. One patient presented with trisomy of chromosomes 1, 7, and 11, while trisomy of chromosome 7 was observed in one patient. There were two patients with trisomy of chromosome 1. Trisomy of chromosomes 1, 7, 11, and 17 was not observed in the cervicovaginal tissue taken from control patients. These data suggest that DES-induced chromosomal trisomy may be an early event in the development of cervicovaginal neoplasia in humans.

Microcell-mediated transfer of chromosome 4 into HeLa cells suppresses telomerase activity

Telomerase activity can be detected in most human cancers and immortal cell lines. In contrast, the lack of telomerase activity in normal diploid fibroblasts has been correlated with progressive reduction of telomere lengths to critically short sizes followed by the cessation of cell division and the onset of senescence. Several investigators have provided evidence for the localization of a telomerase suppressor gene on chromosome 3. The aim of our study was to determine whether other chromosomes are involved in telomerase repression. Beside human chromosome 3 (serving as positive control), chromosomes 4, 6, and 11 were introduced into HeLa cells via microcell-mediated chromosome transfer. Telomerase activity from different hybrid cell lysates was determined at an early time point after fusion using a Telomerase ELISA kit. Strong repression of telomerase activity was only found in a subset of HeLa hybrids in which chromosome 3 or chromosome 4 had been introduced. Telomerase suppression induced by chromosome 3 or 4 transfer was paralleled by a high frequency (30% or 43%, respectively) of a senescent-like phenotype. Chromosomes 6 and 11, the functional loss of which is also implicated in cervical cancer, had no effect. These results indicate that normal human chromosomes 3 and 4 carry a gene or genes that suppress telomerase activity and induce cellular senescence in HeLa cells.

Early genetic events in HPV immortalised keratinocytes

Cancer of the uterine cervix (CaCx) is the second most common cancer in women worldwide. More than 99% of all cervical cancers contain high-risk human papillomaviruses (HPVs), with type 16 predominating. HPV infection alone is not sufficient for neoplastic progression; the HPV-infected cell must undergo additional genetic changes. Cytogenetic analysis of CaCx has been limited due to difficulties in obtaining good-quality banded chromosome preparations. Oncogenic HPVs immortalise primary genital keratinocytes in vitro, and evidence suggests that the molecular genetic and cytogenetic abnormalities observed in HPV immortalised cells reflect the in vivo changes. Therefore, these lines represent suitable models for HPV-induced carcinogenesis. We have used both spectral karyotyping (SKY) and multiplex-FISH (M-FISH) analysis to identify karyotypic changes in HPV-16 immortalised keratinocyte cell lines and established CaCx lines. SKY and M-FISH identified chromosomal abnormalities in all cell lines examined, with a translocation of chromosome 10 or i(10q) occurring in 9 of the 12 cell lines investigated. Further studies with chromosome 10 band-specific probes identified the translocation event as involving 10q with the breakpoint at 10p11.2 in some cell lines or 10q11.2 in others. The pericentric region of chromosome 10 is known to contain duplicated sequences flanking the centromeric satellites. The duplicated sequences contain many zinc finger transcription factor encoding genes and disruption of these in HPV immortalised cell lines may alter the transcription with consequences for both cellular and viral gene expression.

Genetic alterations during the progression of squamous cell carcinomas of the uterine cervix

Most cervical carcinomas appear to arise from cervical intraepithelial neoplasia (CIN) lesions. In addition to infection with high-risk human papilloma viruses, which is indicative of an increased risk of progression, alterations of oncogenes and tumor suppressor genes play a role. Genetic studies of CIN lesions, primary cervical carcinoma, and metastases may shed light on the relative importance of various genetic alterations involved in the progression of CIN to invasive carcinoma. We examined tumor material from 10 patients with squamous cell carcinoma of the uterine cervix and synchronous CIN lesions and lymph node metastases. The CIN component, invasive carcinoma, and lymph node metastases were analyzed separately for loss of heterozygosity (LOH) on the following loci: VHL (3p21), HLA region (6p22-23), PGL (11q 22-24), E6 associated protein (15q11-13), TP53 (17p13), DCC (18q21.1), and chromosomes 1, 2, 4, 9, 20, and X. Using immunohistochemistry, the expression of the EGF receptor, ERBB2, and TP53 was determined. In CIN lesions, frequent LOH was found at chromosome arms 3p, 6p, and 11q. Primary invasive carcinoma showed additional LOH at chromosome arms 6q, 17p, and 18q. In lymph node metastases, an additional locus on the X chromosome displayed LOH. All carcinomas and synchronous lesions but one showed high expression levels of the EGF receptor. TP53 staining, when present, was found in all synchronous lesions. Focal staining of ERBB2 was found in one CIN lesion, two invasive carcinomas, and four metastases. The molecular alterations accumulated in a fashion that paralleled the progression of the tumors. These results indicate that cervical tumorigenesis occurs in a stepwise fashion, including infection and integration of oncogenic HPV and several specific genetic alterations. Genes Chromosomes Cancer 26:346-354, 1999.

Analysis of FHIT transcripts in cervical and endometrial cancers

Carcinoma of the uterine cervix is a common malignancy, and many affected women, have been found to exhibit loss of heterozygosity (LOH) in the chromosome 3p region. Recent studies have localized the FHIT (fragile histidine triad) gene in this region and also demonstrated a high frequency of abnormalities of this gene in various cancers. To determine the role of the FHIT gene in cervical and uterine carcinomas, 16 cases of cervical carcinoma and 7 cases of endometrial carcinoma, as well as nearby non-cancerous tissues in these patients, were analyzed by reverse transcription of the FHIT mRNA followed by polymerase chain reaction amplification and sequencing of the products. In this study, 13 of 16 cervical cancers and 4 of 7 endometrial cancers displayed abnormal FHIT transcripts, including a lack of 2 or more exons of the FHIT gene, the insertion of several bases in the deletion junctions, and a 282 bp deletion from cDNA 171 to 452, resulting in a frameshift. Moreover, 5 of 16 matched non-cancerous tissues from the cervical cancer patients and 4 of 7 non-cancerous tissues from endometrial cancer patients also showed the presence of abnormal transcripts lacking 3 or more exons of the FHIT gene. Only 1 of 23 paired samples exhibited LOH. Our results suggest that the abnormal transcript of the FHIT gene is common in both normal and tumor tissues of the uterus and cervix. We also checked for HPV infection in these samples and found no definite relationship between the abnormal transcript and human papillomavirus infection.

Genomic instability and telomerase activity in human bronchial epithelial cells during immortalization by human papillomavirus-16 E6 and E7 genes

Human papilloma virus types 16 and 18 contribute to the development of cervical carcinomas in which the E6 and E7 genes are frequently retained and expressed in the tumors. Our study explored the ability of the E6 and/or E7 genes to immortalize normal human bronchial epithelial (NHBE) cells and to reactivate telomerase expression in these cells. We have introduced the human papillomavirus type 16 E6 or E7 genes alone or in combination (E6/E7) into NHBE cells using the retroviral construct pLXSN. Cells expressing either the E6 or the E7 oncoproteins alone displayed an increased colony-forming efficiency and a slightly extended in vitro life span before entering a crisis, from which immortalized cell lines were not obtained. Telomerase activity was not detected in cells expressing either E6 or E7 individually. Cells expressing the E6/E7 oncoproteins in combination had a substantially increased life span before entering crisis. A subpopulation of these cells escaped from crisis and achieved 130 population doublings, suggesting immortalization. Telomerase activity was detected in these postcrisis cells, but was not detected prior to crisis. In addition, karyotypic analysis showed evidence of genomic instability in mass cultures as well as clones expressing E6, E7, or E6/E7. Abnormalities included numerous monosomies and trisomies, chromatid gaps and breaks, double minutes, and aberrant chromosomes. These results demonstrate that expression of E6 and/or E7 is sufficient to induce genomic instability and an extended life span to NHBE cells, but the presence of both E6 and E7, along with at least one additional genetic or epigenetic event achieved during crisis, was required for reactivation of telomerase and the immortalization in this human cell type.

Specific chromosomal imbalances in human papillomavirus-transfected cells during progression toward immortality

High risk human papillomaviruses (HPVs) known to be closely associated with cervical cancer, such as HPV16 and HPV18, have the potential to immortalize human epithelial cells in culture. Four lines of HPV-transfected keratinocytes were analyzed by comparative genomic hybridization at different time points after transfection. A number of chromosomal imbalances was found to be highly characteristic for the cultures progressing toward immortality. Whereas several of these were new and previously not found as recurrent aberrations in cervical tumors, some were identical to chromosomal changes observed during cervical carcinogenesis. The data put new emphasis on the studied cell system as a relevant model for HPV-induced pathogenesis.

Interphase karyotypic analysis of chromosomes 11, 17 and X in invasive squamous-cell carcinoma of the cervix: morphological correlation with HPV infection

Human papillomavirus (HPV) infection has been widely implicated in cervical carcinogenesis, but it appears to be an early event, with other genetic abnormalities being required for biological transformation. In this study, interphase cytogenetic analysis of numerical abnormalities of chromosomes 11, 17 and X was performed on paraffin-embedded tissue sections from 25 invasive squamous-cell carcinomas of the cervix and compared with both histopathological features and the morphological distribution of HPV sequences as determined by in situ hybridisation. Numerical differences between chromosomes were identified in 76% of cases, with underrepresentation of chromosomes 11 and/or 17 relative to X in 64% of the total; 22 of 25 cases were HPV-positive, containing either HPV 16, 18 or 31. There was no relationship between the distribution of viral sequences and chromosomal pattern, suggesting that HPV infection precedes karyotypic changes. Our findings suggest that relative reduction in number of chromosomes 11 and 17 is important in the development of invasive cervical neoplasia and are consistent with the putative presence of relevant tumour-suppressor genes on these chromosomes.

Molecular cytogenetic analysis of five newly established cervical cancer cell lines using G banding and fluorescence in situ hybridization

Cervical tumors nearly all have complex karyotypes and more precise cytogenetic information is required to establish whether specific rearrangements occur, and if they are related to the type of HPV infection found. The karyotypes of five recently established cervical cancer cell lines, three from squamous cell carcinomas (two HPV 16 +ve and one HPV 18 +ve), one from an adenocarcinoma (HPV -ve), and one from an adenosquamous carcinoma (HPV 16 +ve), have been analysed using fluorescence in situ hybridization (FISH), with 23 chromosome specific paints, YACs and cosmids as probes, in addition to conventional G banding, in order to identify markers and clarify the breakpoints. Chromosomes 1 and 3 were rearranged in all cell lines. Breakpoints in the squamous lines were all in 3q. but in different regions. Small metacentrics involving chromosome 5 were a del(5q) in one line, and a t(X;5) in another, rather than i(5p). The region 6q21 was involved in three cases and chromosome 9 was rearranged in four. An i(8q) was found in three squamous carcinoma cell lines. Structural changes of 11q were found only in two cases, but a marker 11 representing amplification in the 11q14-22 region was duplicated in the adenosquamous line.

Genomic instability in 1p and human malignancies

Both cytogenetic and molecular genetic approaches have unveiled non-random genomic alterations in 1p associated with a number of human malignancies. These have been interpreted to suggest the existence of cancer-related genes in 1p. Earlier studies had employed chromosome analysis or used molecular probes mapped by in situ hybridization. Further, studies of the various tumor types often involved different molecular probes that had been mapped by different technical approaches, like linkage analysis, radioactive or fluorescence in situ hybridization, or by employing a panel of mouse x human radiation reduced somatic cell hybrids. The lack of maps fully integrating all loci has complicated the generation of a comparative and coherent picture of 1p damage in human malignancies even among different studies on the same tumor type. Only recently has the availability of genetically mapped, highly polymorphic loci at (CA)n repeats with sufficient linear density made it possible to scan genomic regions in different types of tumors readily by polymerase chain reaction (PCR) with a standard set of molecular probes. This paper aims at presenting an up-to-date picture of the association of 1p alterations with different human cancers and compiles the corresponding literature. From this it will emerge that the pattern of alterations in individual tumor types can be complex and that a stringent molecular and functional definition of the role that Ip alterations might have in tumorigenesis will require a more detailed analysis of the genomic regions involved.

Acute myelogenous leukemia with dup(1)(p22p36),dup(1)(p22p36): a novel case?

A case of acute myelogenous leukemia (AML) French-American-British (FAB)-type M5b is described, secondary to myelodysplastic syndrome (MDS), in which a primary clone containing a dup(1)(p22p36) and a subclone containing dup(1)(p22p36), were identified. This is believed to be a novel mutation in AML.

Molecular cytogenetics of human papillomavirus-negative cervical carcinoma cell lines

Cervical cancer is a malignancy closely associated with human papillomavirus (HPV). However, some cervical carcinomas occur in the absence of the virus. Two HPV-negative cervical carcinoma cell lines, C-33A and HT-3, were examined by G-banding and fluorescence in situ hybridization (FISH) using several whole chromosome and satellite probes. Combined conventional banding and FISH analysis significantly enhanced identification of complex and cryptic chromosome rearrangements. Common to both cell lines were translocations of chromosome 1, involving a specific site on the short arm and partial or complete loss of the short arm of chromosome 9, as well as loss of chromosome 13. The C-33A line had a relatively simple chromosomal constitution, with chromosome 1 being involved in translocations with chromosomes 9, 18, and 21. Karyotype reconstruction of G-banded and painted chromosomes indicate a net loss of DNA as a result of unbalanced translocations, which occurred only at site 9p24 and loss of one copy of chromosomes 13 and 14. In contrast, HT-3 cells had complex rearrangements and deletions of chromosomes 1p, 3p, 9p, 10q/p, 11p/q, and 17p, all regions with known tumor suppressor genes. The deletions observed in these HPV-negative cervical carcinomas will be important in delineating regions of tumor suppressor genes.

Human papillomaviruses (HPV) in gynaecological cytology: from molecular biology to clinical testing

Molecular epidemiological and pathological studies show that different HPV types are associated with different cervical lesions allowing classification of the viruses into types associated with 'high', 'intermediate' and 'low' risk of cervical neoplasia. However, HPV infection often regresses and, where it is associated with neoplasia, is an early event. This suggests that other factors are involved in the carcinogenic process, and there is some mechanistic basis for the interaction of epidemiologically defined factors with HPV infection in the process of cervical carcinogenesis. With the refinement of techniques for HPV detection in clinical material, HPV testing is now a realistic possibility, but how this should be performed and in what clinical situation(s) is still uncertain. Particular areas of interest are: (i) the assessment of patients with borderline cytological changes or mild dyskaryosis; and (ii) the definition of those patients at greater risk of invasive disease. Clinical trials are needed before the utility of HPV testing can be properly assessed.

Loss of heterozygosity occurs at the D11S29 locus on chromosome 11q23 in invasive cervical carcinoma

Allelotypic detection of loss of heterozygosity (LOH) has been used to identify putative tumour-suppressor genes. Loci on human chromosome 11q23 are frequently altered in malignant disease, and LOH has been reported at an anonymous D11S29 locus at 11q23 in a proportion of breast and ovarian cancers and malignant melanomas. Previous studies have reported a high frequency of LOH in cervical carcinoma mapping to 11q23. Using polymerase chain reaction techniques employing probes for a recently described polymorphic dinucleotide microsatellite within this locus, we have searched for LOH in 69 cases of invasive cervical carcinoma. Genomic material was microdissected from sections cut from archival paraffin-embedded material, using the patients' constitutional genotype as a control Sixty-two (90%) of the cases were informative, and LOH occurred in 25/62 (40%) of tumours. Loss of an arm or single chromosome 11 is a well-recognised event in cervical carcinoma, and by employing other microsatellite polymorphisms mapping to 11q13 and 11p11-p12 we excluded those cases with widespread allelic loss. By doing so, LOH at D11S29 was found in 16/53 (30%) of tumours. The findings suggest a putative tumour-suppressor gene on 11q involved in cervical carcinogenesis.

Study of numerical aberrations of chromosome 1 by fluorescent in situ hybridization and DNA content by densitometric analysis on (pre)-malignant cervical lesions

In an attempt to determine whether the fluorescent in situ hybridization (FISH) can be used as a rapid approach for the identification of aneuploidy in premalignant cervical smears, a centromeric probe for chromosome 1 was used. The results from the FISH experiments were compared with measurements of the overall DNA content obtained by means of an image analysis system. With progression to neoplasia, a decrease of the frequency of cells with two spots was observed, due to an increasing polysomy of chromosome 1. As far as the DNA content was concerned, an increasing DNA index and 5C-exceeding ratio (fraction of cells with a DNA content higher than 5C) was observed. Classification of the FISH results by a linear discriminant analysis revealed that 67.6% of the cases were classified in agreement with the CIN classification. These data suggest that chromosome 1 may be considered as a marker chromosome for pre-malignant cervical lesions and that the DNA content measurements are complementary to the FISH results.

i(5p) and del(6q) are nonrandom abnormalities in carcinoma cervix uteri. Cytogenetics of two newly developed cell lines

The karyotypes of two recently developed cell lines derived from squamous cell carcinomas of uterine cervix have been analyzed and are described here. Several clonal rearrangements were identified in both cell lines. Abnormalities common to these two cell lines were i(5)(p10) and del(6)(q15q26). The i(5p) was confirmed by use of whole chromosome 5 painting probe in fluorescence in situ hybridization. Based on these findings and review of published data on the cytogenetics of carcinoma of uterine cervix these two lesions are considered to be nonrandom abnormalities associated with this tumor.

Detection of premalignant stages in cervical smears with a biotinylated probe for chromosome 1

Fluorescence in situ hybridization with (peri-)centromeric probes is an easy method to detect numerical aberrations in nonmitotic and mitotic cells. In this study, cervical smears of premalignant and malignant stages (26 controls, 15 CIN I, 12 CIN II, and 15 CIN III cervical smears) were analyzed for the presence of numerical aberrations of chromosome 1 with a centromeric DNA probe (1q12). With more severe stages a decrease of disomy was observed, merely due to a gain of extra copies of chromosome 1; in some cases, however, monosomy was detected. The frequencies of disomy for chromosome 1 ranged from 65.3% to 95.0% in the controls, from 71.3% to 94.3% in CIN I, from 59.2% to 91.5% in CIN II, and from 23% to 96.2% in CIN III. Polysomy ranged from 0% to 5.7% in the controls, from 0% to 14.4% in CIN I, from 0.9% to 30.8% in CIN II, and from 0.8% to 69.6% in CIN III. Monosomy ranged from 2.6% to 34.1% in the controls, from 0% to 17.5% in CIN I, from 3.6% to 27.5% in CIN II, and from 0.9% to 31.4% in CIN III. The results show that screening for aneuploidy of chromosome 1 allows a good discrimination between control samples and dysplasia. These data suggest that chromosome 1 may be a marker chromosome. They are in accordance with previous cytodensitometric analyses, where already in the preneoplastic stages an increased DNA content (polyploidization with subsequent aneuploidization) is observed.

Herpes simplex virus and human papillomavirus sites correlate with chromosomal breakpoints in human cervical carcinoma

The distribution of 1,912 breakpoints observed in a series of 148 cervical cancers was analyzed. Fifty bands were shown to be nonrandomly involved in chromosome structural rearrangements. One hundred thirty-three breaks were noted in bands known to contain a human papillomavirus integration site, and 454 breaks were noted in bands containing a herpes simplex virus breakage site. We suggest that herpes simplex viruses and, possibly, papillomaviruses play an important role in the carcinogenesis and/or development of cytogenetic abnormalities in cervical cancers.