Proliferation and DNA aneuploidy in mild dysplasia imply early steps of cervical carcinogenesis

Aneuploidy: a common and early evidence-based biomarker for carcinogens and reproductive toxicants

Aneuploidy, defined as structural and numerical aberrations of chromosomes, continues to draw attention as an informative effect biomarker for carcinogens and male reproductive toxicants. It has been well documented that aneuploidy is a hallmark of cancer. Aneuploidies in oocytes and spermatozoa contribute to infertility, pregnancy loss and a number of congenital abnormalities, and sperm aneuploidy is associated with testicular cancer. It is striking that several carcinogens induce aneuploidy in somatic cells, and also adversely affect the chromosome compliment of germ cells. In this paper we review 1) the contributions of aneuploidy to cancer, infertility, and developmental abnormalities; 2) techniques for assessing aneuploidy in precancerous and malignant lesions and in sperm; and 3) the utility of aneuploidy as a biomarker for integrated chemical assessments of carcinogenicity, and reproductive and developmental toxicity.

Identification of a novel feline large granular lymphoma cell line (S87) as non-MHC-restricted cytotoxic T-cell line and assessment of its genetic instability

Feline large granular lymphocyte lymphomas are rare but very aggressive tumors with a poor prognosis. In this study, a cell line from an abdominal effusion of a cat with large granular lymphoma was characterized. Immunophenotype staining was positive for CD3 and CD45R, and negative for CD4, CD8, CD56, CD79α, BLA.36 and NK1. A TCR γ gene rearrangement was detectable by PARR. Neither FeLV antigen nor exogenous FeLV provirus could be detected. A chromosomal instability associated with a centrosome hyperamplification could also be determined. The cell line is able to lyse target cells without antigen presentation or interaction with antigen presenting cells. Therefore, these cells were classified as genetically instable non-MHC-restricted cytotoxic T cells with large granular lymphocyte morphology.

Human papillomavirus oncoproteins: pathways to transformation

An association between human papillomavirus (HPV) infection and the development of cervical cancer was initially reported over 30 years ago, and today there is overwhelming evidence that certain subtypes of HPV are the causative agents of these malignancies. The p53 and retinoblastoma proteins are well-characterized targets of the HPV E6 and E7 oncoproteins, but recent studies have shown that the alteration of additional pathways are equally important for transformation. These additional factors are crucial regulators of cell cycle progression, telomere maintenance, apoptosis and chromosomal stability. Understanding how HPV oncoproteins modify these activities provides novel insights into the basic mechanisms of oncogenesis.

The law of stage-by-stage development of human tumors, derived from the results of ploidometric studies

The ploidy of 56,000 epithelial cell nuclei was studied at different stages of carcinogenesis by Imager-CG computer image analyzer. The linear relationship between carcinogenesis stages and quantitative parameters (indexes of mean ploidy of cell nuclei) at a certain stage was detected and mathematically described. A step-by-step increase of DNA content in cell nuclei by one unit of ploidy leads to emergence of new biological properties, measured by the number of units surpassing the normal cell nuclear ploidy values, which was called "the malignancy code".

Oncogenic activities of human papillomaviruses

Infectious etiologies for certain human cancers have long been suggested by epidemiological studies and studies with experimental animals. Important support for this concept came from the discovery by Harald zur Hausen's group that human cervical carcinoma almost universally contains certain "high-risk" human papillomavirus (HPV) types. Over the years, much has been learned about the carcinogenic activities of high-risk HPVs. These studies have revealed that two viral proteins, E6 and E7, that are consistently expressed in HPV-associated carcinomas, are necessary for induction and maintenance of the transformed phenotype. Hence, HPV-associated tumors are unique amongst human solid tumors in that they are universally caused by exposure to the same, molecularly defined oncogenic agents, and the molecular signal transduction pathways subverted by these viral transforming agents are frequently disrupted in other, non-virus-associated human cancers.

The human papillomavirus E7 oncoprotein

The human papillomavirus (HPV) E7 oncoprotein shares functional similarities with such proteins as adenovirus E1A and SV40 large tumor antigen. As one of only two viral proteins always expressed in HPV-associated cancers, E7 plays a central role in both the viral life cycle and carcinogenic transformation. In the HPV viral life cycle, E7 disrupts the intimate association between cellular differentiation and proliferation in normal epithelium, allowing for viral replication in cells that would no longer be in the dividing population. This function is directly reflected in the transforming activities of E7, including tumor initiation and induction of genomic instability.

Analysis of centrosome overduplication in correlation to cell division errors in high-risk human papillomavirus (HPV)-associated anal neoplasms

High-risk HPV-associated anal neoplasms are difficult to treat and biomarkers of malignant progression are needed. A hallmark of carcinogenic progression is genomic instability, which is frequently associated with cell division errors and aneuploidy. The HPV-16 E7 oncoprotein has been previously shown to rapidly induce centriole and centrosome overduplication and to cooperate with HPV-16 E6 in the induction of abnormal multipolar mitoses. Based on this function, it has been suggested that HPV-16 E7 may act as a driving force for chromosomal instability. However, a detailed analysis of centrosome overduplication in primary HPV-associated neoplasms has not been performed so far. Here, we determined the frequency of centrosome overduplication in HPV-associated anal lesions using a recently identified marker for mature maternal centrioles, Cep170. We detected centrosome overduplication in a small but significant fraction of cells. Remarkably, centrosome overduplication, but not aberrant centrosome numbers per se or centrosome accumulation, correlated significantly with the presence of cell division errors. In addition, our experiments revealed that in particular pseudo-bipolar mitoses may play a role in the propagation of chromosomal instability in high-risk HPV-associated tumors. These results provide new insights into the role of centrosome aberrations in cell division errors and encourage further studies on centrosome overduplication as a predictive biomarker of malignant progression in HPV-associated anal lesions.

Aberrant, highly hyperdiploid cells in human papillomavirus-positive, abnormal cytologic samples are associated with progressive lesions of the uterine cervix

BACKGROUND

Infection with oncogenic-type human papillomavirus (HPV) and consecutive cytologic abnormalities of the uterine cervix precede the evolution of carcinoma. However, the specificity of both changes is too low to predict the true malignant potential of the change in a given time point, because the majority of the HPV infections revert to normal with time. In preliminary studies, the authors demonstrated that, among many dysregulatory phenomena at the cytologic level, the occurrence of significant DNA content aberrations were in good correlation with progressive cervical changes; and, as a marker for this, the significance of cells with nuclear DNA content > 9c (9c cells) was investigated using slide-based cytometry. The objective of the current study was to determine whether 9c cells in cytologic samples that presented with dysplasia and with high-risk HPV types were associated with the development of higher grade cervical intraepithelial neoplasia (CIN II+).

METHODS

Samples with positive cytologic diagnoses (atypical squamous cells of undetermined significance, low-grade squamous intraepithelial lesion [LSIL], and high-grade squamous intraepithelial lesion [HSIL]) were evaluated for both parameters and were related to outcomes and, if available, to histology results over a follow-up of up to 4 years.

RESULTS

Although the presence of high-risk HPV was demonstrable in almost all samples with CIN II+ (96.7%), the virus genome alone proved to have a poor positive predictive value (56.1%) for higher grade CIN. Cytology and the demonstration of 9c cells resulted in less sensitivity compared with the occurrence of high-risk HPV (70.4% and 73.7%, respectively) but in significantly greater specificity (91.3% and 89.2%, respectively). Moreover, a positive predictive value of 81.8% for CIN II+ could be calculated for 9c cells. HSIL morphology, unfavorable HPV type, and DNA cytometry together excluded the highest rate of CIN > or = II with 100% sensitivity and 91.3% specificity.

CONCLUSIONS

Biologic parameters, in addition to cytology, help to define the nature of cervical dysplasias more accurately. Oncogenic HPV types and hyperdiploid cells with DNA content > 9c disclosed cytologic changes with the greatest malignant potential. Cancer

Exploratory analysis of quantitative histopathology of cervical intraepithelial neoplasia: Objectivity, reproducibility, malignancy-associated changes, and human papillomavirus

BACKGROUND

As part of a project to evaluate emerging optical technologies for cervical neoplasia, our group is performing quantitative histopathological analyses of biopsy specimens from 1,190 patients. Objectives in the interim analysis are (a) quantitatively assessing progression of the neoplastic process of cervical intraepithelial neoplasia (CIN)/squamous intraepithelial lesions (SIL), (b) detecting malignancy-associated changes (MACs), and (c) phenotypically measuring human papillomavirus (HPV) detected by DNA testing.

METHODS

The diagnostic region of interest (ROI) from immediately adjacent sections were imaged, and the basal lamina and surface of the superficial layer were delimited. Nonoverlapping quantitatively stained nuclei were selected from 1,190 samples with histopathological characteristics of normal (929), koilocytosis (130), CIN 1 (40), CIN 2 (23), and CIN 3/carcinoma in situ (CIS) (68). A fully automatic procedure located and recorded the center of every nucleus in the region of interest (ROI). We used linear discriminant analysis to assess the changes between normal and CIN 3/CIS.

RESULTS

Scores computed from the cell-by cell features and the clinical grade of CIN/SIL were highly correlated, as were those of the architectural features and the clinical grade of CIN/SIL. We found even higher correlations between a combination of cell-by-cell and architectural scores, and clinical grade. Using these scores, we found MACs in the normal biopsy specimens from patients with high-grade CIN/SIL. Furthermore, the same scores correlated with the molecular detection of HPV.

CONCLUSIONS

Quantitative histopathology can be used in large clinical trials as an objective and reproducible measure of CIN/SIL. Detectable phenotypic changes correlate well with CIN/SIL neoplastic progression. It can also be used to infer the presence of CIN/SIL (MACs) and molecular changes associated with increased risk of cancer development (high-risk HPV).

Determination of features indicating progression in atypical squamous cells with undetermined significance: human papillomavirus typing and DNA ploidy analysis from liquid-based cytologic samples

BACKGROUND

The Bethesda System of cervical cytologic findings introduced the term ASCUS (atypical squamous cells of undetermined significance) to cover the broad zone separating normal cytomorphology from definitive squamous intraepithelial lesions (SILs). The management of patients with ASCUS is particularly problematic as approximately 10% of ASCUS patients develop SIL and 1 per 1000 develop cervical carcinoma.

METHODS

Our aim was to demonstrate the combined use of polymerase chain reaction for human papillomavirus (HPV) typing and laser scanning cytometry for DNA content measurements in the subcategorization of ASCUS cases according to the risk for progression toward cancer. Liquid- based monolayer preparation (ThinPrep, Cytyc, Boston, MA) of the cytologic material was used for cytomorphologic analysis. DNA content measurements using laser scanning cytometry and direct sequencing of HPV using the consensus primers GP5+/GP6+ and MY09/MY11 were performed from the same material.

RESULTS

Twelve of the 44 cases (27.2%) with ASCUS carried a high-risk HPV genome whereas only 3 of the 195 normal control cases (1.5%) showed positivity for a high-risk HPV genome. Six of 12 (50%) of the high-risk HPV-positive ASCUS cases presented isolated cells with a DNA content above 5c, whereas cells with a DNA content above 9c were found in 3 of 12 cases (25%) and were exclusively found in combination with high-risk HPV infection. In these three cases, the histologic follow-up resulted in cervical intraepithelial neoplasia (CIN) I (one case) and CIN III (two cases). None of the other ASCUS or normal cases displayed DNA aneuploidy above 9c. They returned to normal cytology (within normal limits/benign cellular changes) in the follow-up.

CONCLUSIONS

Human papillomavirus typing and DNA content measurements may delineate a distinct group of ASCUS. Our preliminary data suggest that ASCUS cases with high-risk HPV positivity and with rare cells with abnormally high DNA content represent similar biologic features as high-grade SIL and are at elevated risk to develop cancer.

Numerical aberrations of chromosome 1 in cervical intraepithelial neoplasia are strongly associated with infection with high-risk human papillomavirus types

The aims of this study were to assess the relationships between numerical aberrations of chromosome 1 and the presence of high-risk human papillomavirus (HPV). Five normal samples, 11 CIN1, 13 CIN2, 18 CIN3, and nine carcinomas were studied by in situ hybridization (ISH), using a DNA probe for the centromere of chromosome 1 (cen#1) and a DNA probe cocktail for HPV types 16 and 18. A short fragment polymerase chain reaction hybridization line probe assay (SPF-PCR-LiPA) technique was used to detect 25 HPV types. The mean number of cen#1 per nucleus (chromosome index, CI) was measured, and the fractional areas of dysplastic epithelium with HPV16/18 infection and with cen#1 aneusomy were estimated. Disomy was found in all normal epithelium and in 36% of CIN1. Tetrasomy was observed in 64% of CIN1, 15% of CIN2, and 17% of CIN3. Hyper-tetrasomy was observed in 77% of CIN2, 83% of CIN3, and 100% of invasive carcinomas. High-risk HPVs were present in 20%, 75%, and 94% of disomic, tetrasomic, and hyper-tetrasomic lesions, respectively. The mean CI value was significantly higher in the lesions infected with high-risk HPV than in the lesions not infected by high-risk HPV (p < 0.001), due to the significantly higher prevalence of hyper-tetrasomy. The ISH study disclosed that HPV16/18 was exclusively found within dysplastically altered epithelium. The area with aneusomy is mostly enclosed within the area infected with HPV. In 83% of the HPV16/18-positive CIN lesions, the fractional area of HPV-infected epithelium was equal to, or larger than, the fractional area with aneusomy. In conclusion, aneusomy for chromosome 1 is strongly associated with high-grade CIN lesions and infection with high-risk HPV; it is likely that the occurrence of numerical aberrations of chromosome 1 is preceded by infection with high-risk HPV.

Human papillomaviruses and centrosome duplication errors: modeling the origins of genomic instability

The majority of human cancers are genomically unstable, often with gains or losses of whole chromosomes. In high-risk human papillomavirus (HPV)-associated cervical neoplasia, the two HPV-encoded oncoproteins E6 and E7 have been implicated in mitotic infidelity by their ability to induce centrosome-related mitotic disturbances. However, the mechanisms by which HPV E6 and E7 subvert centrosome homeostasis are strikingly different. Whereas the E7 oncoprotein rapidly drives centrosome duplication errors in cells that appear phenotypically normal, expression of the HPV E6 oncoprotein results in an accumulation of supernumerary centrosomes in multinucleated cells. The primary centrosome duplication defect in HPV E7 expressing cells may be linked to the ability of E7 to disrupt regulatory nodes that govern both the host cell division cycle machinery and the initiation of centrosome duplication. Most importantly, the E7 oncoprotein has been shown to dysregulate cdk2 activity, a major determinant for the initiation of centrosome duplication. HPV-induced centrosome abnormalities, multipolar mitoses, and aneuploidy often occur at early stages during cervical carcinogenesis and increase with malignant conversion. These findings suggest that HPV oncoprotein-induced chromosomal instability increases the risk for genetic changes that may ultimately facilitate carcinogenic progression.

Comparative cytotoxicity of low-osmolar nonionic and high-osmolar ionic contrast media to dog gallbladder epithelial cells

BACKGROUND

Most studies of the adverse effects of x-ray contrast media used in ERCP have focused on post-ERCP pancreatitis. However, the biliary epithelial cells are also exposed to contrast media during ERCP and acute cholangitis is also a serious complication of ERCP. The present study compared the cytotoxicity with gallbladder epithelial cells of ionic and nonionic contrast agents.

METHODS

A high-osmolar ionic contrast agent (meglumine ioxithalamate) and a low-osmolar nonionic contrast agent (iopromide) were tested. Monolayer cell cultures of dog gallbladder epithelial cells were used. The cells were exposed to the 2 contrast agents with increasing iodine concentration and osmolality for 2 days. Cell number, S-phase fraction, aneuploidy, and supernatant LDH activities were measured each day.

RESULTS

Cell growth was more severely inhibited by ioxithalamate than iopromide (p < 0.05) and strongly dependent on the osmolality of contrast agent. The cytostatic effect estimated by S-phase fraction was more pronounced for ioxithalamate. Chromosomal damage determined by aneuploidy was more frequently detected with ioxithalamate.

CONCLUSIONS

High-osmolar ionic contrast media are more cytotoxic than low-osmolar nonionic contrast media to gallbladder epithelial cells. Animal and clinical studies are needed to estimate the clinical implications of these findings.

The mitotic machinery as a source of genetic instability in cancer

Development and growth of all organisms involves the faithful reproduction of cells and requires that the genome be accurately replicated and equally partitioned between two cellular progeny. In human cells, faithful segregation of the genome is accomplished by an elaborate macromolecular machine, the mitotic spindle. It is not difficult to envision how defects in components of this complex machine molecules that control its organization and function and regulators that temporally couple spindle operation to other cell cycle events could lead to chromosome missegregation. Recent evidence indicates that the persistent missegregation of chromosomes result in gains and losses of chromosomes and may be an important cause of aneuploidy. This form of chromosome instability may contribute to tumor development and progression by facilitating loss of heterozygocity (LOH) and the phenotypic expression of mutated tumor suppressor genes, and by favoring polysomy of chromosomes that harbor oncogenes. In this review, we will discuss mitotic defects that cause chromosome missegregation, examine components and regulatory mechanisms of the mitotic machine implicated in cancer, and explore mechanisms by which chromosome missegregation could lead to cancer.

Chromosome division figures reveal genomic instability in tumorigenesis of human colon mucosa

A variety of chromosomal gains and losses has been detected with comparative genomic hybridization during tumorigenesis in the colon mucosa. The aim of this investigation was to corroborate increasing genomic instability and to elucidate those lesions in which the record from comparative genomic hybridization has remained unexpectedly negative. Replicate paraffin-embedded samples were investigated in detail using image microphotometry. Crucial to the recent approach was the fact that the histological compartments were exactly matched and that the single-cell measurements were highly accurate (CV at 0.05). Feulgen DNA was quantified in interphase nuclei and chromosome division figures, which were found in all cases of high-grade dysplasia and, with increased frequency, of colon carcinoma. The genomic imbalance in chromosome division figures was quantified by the sensitive 4.5 c exceeding rate (where c is the haploid genome equivalent), which was also positive in cases with a negative record from comparative genomic hybridization. The DNA content of chromosome division figures was measured with a mean 4.5 c exceeding rate of 25.8 +/- 4.4% standard error in 12 cases of high-grade dysplasia and of 62.1 +/- 7.1% in colon carcinoma (16 cases). The chromosome division figures were considered to be the first morphological manifestation of genomic instability attending precancerous conditions in the colon. Telophase-like chromosome division figures with unequal amounts of DNA in their hemispheres revealed gross somatic mutations before clonal selection.

The DNA content of chromosome division figures and interphase nuclei classifies ulcerative colitis

Long-standing ulcerative colitis is considered to be a precancerous condition. Therefore, a practical and reliable method is required for monitoring the progress of the disease. Liberation of the S-phase from karyokinesis occurs in DNA amplification and endoreplication, producing nuclei with more than 4 c DNA. The amount of Feulgen DNA was quantified with an image microphotometer in 8 microns sections for interphase nuclei and in 15 microns sections for chromosome division figures (CDFs). Development of ulcerative colitis was investigated in low grade dysplasia (n = 93 cases; score 3-7) and high grade dysplasia (n = 22; score 8-10). Bacterial colitis (n = 34) and invasive adenocarcinoma (n = 26) provided a basis for data interpretation in dysplasia. Lymphocyte nuclei served as an internal DNA standard. CDFs represent a novel type of aberrant 'mitoses'; they are different from and much more frequent than figures with multipolar spindles. Endoreplication began with low grade dysplasia in interphase nuclei as well as with CDFs; it was fully established in high grade dysplasia and carcinoma. Endoreplicated interphase nuclei and CDFs represent an early morphological mosaic of genomic instability. Both characteristics support a reproducible two-level classification of low and high grade dysplasia in ulcerative colitis.