Loss of heterozygosity on chromosome 17p and mutant p53 in HPV-negative cervical carcinomas

Next-generation Sequencing Reveals Recurrent Somatic Mutations in Small Cell Neuroendocrine Carcinoma of the Uterine Cervix

Small cell neuroendocrine carcinoma (SCNEC) of the uterine cervix is a rare but extremely aggressive tumor. While high-risk human papillomavirus (HPV) is involved at an early stage of oncogenesis in many tumors, additional driving events have been postulated to facilitate the progression of SCNECs. Identification of oncogenic drivers could guide targeted therapy of this neoplasm. Clinicopathologic features of 10 cervical SCNECs are reported. Analyses included immunohistochemical evaluation of p16, p53, synaptophysin, and chromogranin expression; in situ hybridizations and polymerase chain reaction for high-risk HPV and/or HPV 18; and next-generation sequencing based on a 637-gene panel. The patients ranged in age from 28 to 68 years (mean, 45.6 y; median, 40.5 y). All tumors had diffuse p16 and synaptophysin expression. All but 1 tumor was positive for chromogranin (extent of staining ranged from focal to diffuse). HPV 18 was detected in 6 tumors and HPV 35 in 1 tumor. At least 1 driver mutation was detected in 8 tumors. Four cases harbored TP53 somatic mutations, 3 of which correlated with an aberrant p53 staining pattern. Four PIK3CA mutations (p.G106A, p.N345T, p.E545K, and p.E545D) were detected in 3 tumors, 2 of which also harbored TP53 mutations. Oncogenic driver mutations involving KRAS, Erbb2, c-Myc, NOTCH1, BCL6, or NCOA3 were detected in 4 tumors. Mutations in caretaker tumor suppressors PTEN, RB1, BRCA1, BRCA2, and ARID1B were also identified in 4 tumors that commonly coharbored activating oncogenic mutations. Targeted next-generation gene sequencing identified genetic alterations involving the MAPK, PI3K/AKT/mTOR, and TP53/BRCA pathways in SCNECs. The presence of genetic alterations that are amenable to targeted therapy in SCNECs offers the potential for individualized management strategies for treatment of this aggressive tumor.

Individual karyotypes at the origins of cervical carcinomas

Background

In 1952 Papanicolaou et al. first diagnosed and graded cervical carcinomas based on individual “abnormal DNA contents” and cellular phenotypes. Surprisingly current papilloma virus and mutation theories of carcinomas do not mention these individualities. The viral theory holds that randomly integrated, defective genomes of papilloma viruses, which are often untranscribed, cause cervical carcinomas with unknown cofactors 20–50 years after infection. Virus-free carcinomas are attributed to mutations of a few tumor-suppressor genes, especially the p53 gene. But the paradox of how a few mutations or latent defective viral DNAs would generate carcinomas with endless individual DNA contents, degrees of malignancies and cellular phenotypes is unsolved. Since speciation predicts individuality, we test here the theory that cancers are autonomous species with individual clonal karyotypes and phenotypes. This theory postulates that carcinogens induce aneuploidy. By unbalancing mitosis genes aneuploidy catalyzes chain reactions of karyotypic evolutions. Most such evolutions end with non-viable karyotypes but a few become new cancer karyotypes. Despite congenitally unbalanced mitosis genes cancer karyotypes are stabilized by clonal selections for cancer-specific autonomy.

Results

To test the prediction of the speciation theory that individual carcinomas have individual clonal karyotypes and phenotypes, we have analyzed here the phenotypes and karyotypes of nine cervical carcinomas. Seven of these contained papilloma virus sequences and two did not. We determined phenotypic individuality and clonality based on the morphology and sociology of carcinoma cells in vitro. Karyotypic individuality and clonality were determined by comparing all chromosomes of 20 karyotypes of carcinomas in three-dimensional arrays. Such arrays list chromosome numbers on the x-axis, chromosome copy numbers on the y-axis and the number of karyotypes arrayed on the z-axis. We found (1) individual clonal karyotypes and phenotypes in all nine carcinomas, but no virus-specific markers, (2) 1-to-1 variations between carcinoma-specific karyotypes and phenotypes, e.g. drug-resistance and cell morphology, (3) proportionality between the copy numbers of chromosomes and the copy numbers of hundreds of over- and under-expressed mRNAs, (4) evidence that tobacco-carcinogens induce cervical carcinomas via aneuploidy, consistent with the speciation theory.

Conclusions

Since the individual clonal karyotypes of nine carcinomas correlated and co-varied 1-to-1 with complex individual transcriptomes and phenotypes, we have classical genetic and functional transcriptomic evidence to conclude that these karyotypes encode carcinomas - much like the clonal karyotypes that encode conventional species. These individual karyotypes explain the individual “DNA contents”, the endless grades of malignancies and the complex individual transcriptomes and phenotypes of carcinomas.

p63 and epithelial biology

The transcription factor p63 is a homologue of the tumor suppressor p53. Unlike p53, which is dispensable for normal development, p63 is critical for the development of stratified epithelial tissues such as epidermis, breast, and prostate. p63 encodes multiple protein isoforms with both transactivating and transcriptional repressor activities that can regulate a wide spectrum of target genes. p63 is also implicated in tumor formation and progression in stratified epithelia, with evidence for both tumor suppressive and oncogenic properties. This review will examine current data and hypotheses regarding the role of p63 in the development, maintenance, and tumorigenesis of stratified epithelium.

Comparison of real-time PCR signal-amplified in situ hybridization and conventional PCR for detection and quantification of human papillomavirus in archival cervical cancer tissue

Archival paraffin-embedded tumor specimens offer a wealth of information for both cancer research and for routine clinical applications. However, the use of formalin-fixed, paraffin-embedded specimens for quantitative real-time PCR is not yet a standard diagnostic method in many laboratories, in particular for the quantification of human papillomavirus (HPV). Particularly high-risk HPV types are involved in almost 100% of the carcinogenesis of cervical cancer. We compared the diagnostic applicability and sensitivity of real-time PCR to that of chromogenic tyramide-signal-amplified in situ hybridization and conventional PCR for the detection of HPV from archival tissue in 164 cases of carcinoma in situ and cervical cancer. Furthermore, we examined whether the viral load of HPV is of prognostic relevance. Our findings indicate that patients in tumor stage I with a lower viral load of HPV type 16 (HPV16; up to 1,000 copies/ng of DNA) had a significantly better survival than HPV 16-negative patients (P = 0.037). We observed a greater sensitivity of both real-time PCR and conventional PCR for the detection of HPV16 and -18 compared to signal amplified in situ hybridization. We found a considerable concordance between HPV16 (kappa = 0.661) and HPV18 (kappa = 0.781) status as measured by real-time PCR and conventional PCR, indicating similar sensitivities. We recognized an inhibitory effect of formalin fixation and paraffin embedding on the evaluation of real-time PCR quantification.

Polymorphism of the p53 codon 72 Arg/Pro and the risk of HPV type 16/18-associated cervical and oral cancer in India

Infection of high risk human papillomaviruses (HPVs) specifically the types 16 and 18 has been strongly implicated in the development of cervical cancer. The E6 oncoproteins of these high risk HPVs are known to bind and induce degradation of p53 tumour suppressor protein through the ubiquitin pathways. This degradation is controlled by a common polymorphism of the p53 gene encoding either a proline or an arginine at its codon 72 in exon 4. Recently, it has been demonstrated that the presence of homozygous arginine at codon 72 renders p53 about seven times more susceptible to E6-mediated proteolytic degradation as well as to cervical cancer than those with proline homozygotes or proline/arginine heterozygotes. In India, prevalence of HPV as well as cancers of the uterine cervix and the oral cavity are highest in the world. We have examined this allele-specific predisposition in cervical and oral cancer which is associated with HPV as well as in a non-HPV-linked cancer of the breast. We have carried out investigation in women comprising whole spectrum of cervical lesions with 128 HPV 16/18 positive and 35 HPV negative invasive cervical carcinomas and 34 cases of HPV (16/18) positive and 16 HPV negative cervical dysplasias (mild, moderate and severe) and 104 age-group-matched healthy women as controls. Additionally, we have analysed p53Arg-Pro polymorphism in 13 high risk HPV positive and 31 HPV negative oral cancers along with 20 normal controls and 77 breast cancers with 41 age-matched healthy controls. We observed more than two fold higher risk for homozygous arginine (chi2 = 6.3, df = 2, p = 0.04; OR = 2.3; 95% CI: 1.08-5.16) for HPV 16/18-positive cervical carcinomas when comparison was made only between HPV positive cervical cancers and normal controls but most interestingly, no significant association either in the frequency of homozygous arginine or proline alleles or their heterozygotes could be observed when all the three groups i.e. HPV-positive, HPV-negative cervical cancers and controls were considered simultaneously. No difference was also observed for either arginine or proline polymorphism between women with precancerous lesions of the uterine cervix carrying HPV 16/18 infection and controls. Similarly, increased risk of oral or breast cancer could not be correlated with the polymorphism of arginine/proline allele. Thus the interaction between HPV oncoproteins and the p53 gene polymorphism specifically, homozygous arginine at codon 72 appears to play no role in the development of either cervical or oral cancer and also it can not serve as a biomarker for early identification of cervical, oral or breast cancer.

Higher incidence of p53 mutation in cervical carcinomas with intermediate-risk HPV infection

OBJECTIVE

Inactivation of p53, either through mutation or interaction with human papillomavirus (HPV) E6 oncoprotein, is a characteristic feature of cervical carcinoma cell lines that have been previously studied. To elucidate the role of p53 in the carcinogenesis of Korean cervical carcinomas, 27 HPV-positive and 13 HPV-negative cervical carcinomas were studied in order to evaluate the status of the p53 gene.

STUDY DESIGN

The HPV status was ascertained by polymerase chain reaction (PCR) amplification using consensus primers designed from the E6 and E7 open reading frames (ORFs). The p53 mutation status was analyzed by direct sequencing of the PCR product in highly conserved exons 5-8.

RESULTS

There was no significant difference in the frequency of the p53 mutation between the HPV-positive and negative cases. All three mutations in the HPV-positive cases were associated with intermediate-risk viruses. The average age of the patients with the p53 mutation was 14 years older than that of patients without the p53 mutation.

CONCLUSION

p53 mutations are higher in the so called intermediate-risk HPV positive than HPV 16 or 18 positive cervical carcinomas.

p53 from complexity to simplicity: mutant p53 stabilization, gain-of-function, and dominant-negative effect

Increasing the complexity of their models, p53s are stabilized either in order to function (wt p53) or due to the loss of function (mutant p53) with acquiring a mysterious prion-like ability to drive the normal p53 into the abnormal conformation to gain new functions. As already recognized, the loss of trans-activating function leads to a stabilization of mutant p53 because of the disappearance of the p53-inducible proteins, which otherwise directly (Mdm-2) or indirectly (p21) target p53 for degradation. Simplifying further, I will discuss that the loss of function results in a dominant-negative effect and gain-of-function (a dominant-positive effect). Thus, mutant p53 lacking trans-activation function nevertheless may retain the ability to repress transcription due to its competition with numerous transcription factors for their coactivators. When mutant p53 competes with wt p53, the inhibition of the wt p53-dependent transcription is perceived as a dominant-negative effect. Just like trans-repression, a dominant-negative effect requires an excess of p53 and, therefore, a 'dominant'-negative effect is not dominant. Furthermore, the stabilization of an endogenous mt p53 due to the loss of wt functions cannot occur in the presence of the wt p53 allele. Given the inability of mutant p53 to accumulate in the presence of wt p53, a dominant-negative effect does not naturally occur and, not surprisingly, heterozygous mt/wt cells are rare. The detection of a dominant-negative effect simply indicates that mutant p53 indeed has lost its function. Last, since mutant p53 loses some or most but not all activities and accumulates in the absence of wt allele, gain-of-function can be considered as an exaggeration of the remaining functions. Applications to cancer therapy are discussed. -Blagosklonny, M. V. p53 from complexity to simplicity: mutant p53 stabilization, gain-of-function, and dominant-negative effect.

Inhibition of human telomerase activity by antisense phosphorothioate oligonucleotides encapsulated with the transfection reagent, FuGENE6, in HeLa cells

Telomerase, a ribonucleoprotein, synthesizes telomeric repeats (TTAGGG) onto the ends of chromosomes to maintain the constant length of the telomere DNA, and its activity is detectable in approximately 85%-90% of primary human cancers. Thus, it is postulated that human telomerase might be associated with malignant tumor development and could be a highly selective target for antitumor drug design. Antisense phosphorothioate oligonucleotides (S-ODN) were investigated for their abilities to inhibit telomerase activity in the HeLa cell line. The S-ODN were designed to be complementary to nucleotides within the RNA active site of telomerase. As a transfection reagent, FuGENE6 (Boehringer Mannheim, Mannheim, Germany) was used to enhance the cellular uptake of the oligonucleotides in cell cultures. The S-ODN encapsulated with FuGENE6 clearly inhibited telomerase activity in HeLa cells and showed sequence-specific inhibition. The encapsulated S-ODN-3 with a 19-nucleotide, (nt) chain length had inhibitory effects similar to those of the 21-mer and 23-mer S-ODN sequences (S-ODN-4 and 5), but the 15-mer and 17-mer S-ODN sequences (S-ODN-1 and 2) failed to satisfactorily prevent telomerase activity. However, apoptotic HeLa cell death was not associated with telomerase inhibition. Furthermore, the encapsulated S-ODN did not appear to be cytotoxic in terms of the cell growth rate. The oligonucleotides encapsulated with the transfection reagent had enhanced cellular uptake, and cytoplasmic and nuclear localizations were observed. However, weak fluorescent signals were observed within the cytoplasms of HeLa cells treated with the free S-ODN-3. Thus, the activities of the S-ODN were effectively enhanced by using the transfection reagent. The transfection reagent, FuGENE6, may thus be a potentially useful delivery vehicle for oligonucleotide-based therapeutics and transgenes and is appropriate for use in vitro and in vivo.

Favorable clinical outcome of cervical cancers infected with human papilloma virus type 58 and related types

To determine whether the status of human-papillomavirus (HPV) infection affects the clinical outcome of cervical carcinoma (CC), HPV genotype was prospectively determined in 94 consecutive CC cases subsequently followed for a median duration of 37.5 months. With a consensus PCR-RFLP method of HPV genotyping, 81 (86.2%) cancers were positive for HPV DNA. They were classified, according to the phylogenic similarities, into HPV-16-related (type 16, n = 45; type 31, n = 2), HPV-58-related (type 58, n = 17; type 33, n = 3; type 52, n = 2) and HPV-18-related (type 18, n = 8; type 68, n = 1) groups, and analyzed in relation to clinical outcome. The following results were observed: (i) Type-58-related HPVs were more prevalent in the old age (older than the median age of 52) group than in the young age group (41% vs. 14.6%, p = 0.045); (ii) 63% (5/8) of patients with advanced stages (III and IV) were HPV-negative, a figure much higher than that (9.3%, 8/84) of patients with early stages (stage I and II) (p = 0.002); (iii) the occurrence of adenocarcinoma or adenosquamous carcinoma was higher in the HPV-18-related group (50%) than in the HPV-16-related (33.3%) or the HPV-58-related (16.7%) groups (p = 0.024); (iv) the status of lymph-node metastasis and tumor grade did not correlate with HPV status; (v) 5-year survival rates were 90.2%, 80% and 74% for HPV-58-, HPV-16- and HPV-18-related groups, respectively (p = 0.03, after adjustment for tumor stage); (vi) in comparison with the HPV-16-related group, the relative risk of death in the HPV-58- and the HPV-18-related groups were 0.32 [95% CI, 0.07-1.49] and 1.87 [0.36-14.9] respectively. HPV genotype appears to affect the clinical behavior and outcome of cervical cancer. HPV-58-related types are prevalent in the older population, and appear to confer a favorable prognosis. Int. J. Cancer (Pred. Oncol.) 84:553-557, 1999.

Fluorescence in situ hybridization in cervical smears: detection of numerical aberrations of chromosomes 7, 3, and X and relationship to HPV infection

BACKGROUND

Human papillomavirus (HPV) is known to play a pivotal role in cervical carcinogenesis. Chromosomal aberrations are known to be related to different biological behaviors of malignant lesions. We analyzed whether numerical chromosomal aberrations, related to more aggressive tumor types, are found not only in high-grade squamous intraepithelial lesions (HSIL) but also in low-grade SIL (LSIL) of the cervix and evaluated their relationship to HPV infection.

METHODS

Eighty women (19 to 74 years of age) were included in this study and grouped according to the Bethesda System: within normal limits (WNL), LSIL, and HSIL. By FISH, chromosomes 7 and X, and in part chromosome 3, were analyzed for numerical aberrations. Using the hybrid capture system HPV detection was performed.

RESULTS

All 20 patients with cervical smear WNL had regular diploid chromosomal pattern and were negative for HPV. Thirteen of the 29 (41.2%) patients with LSIL showed trisomy 7, in association with trisomy X in 4 cases (12.9%). Single trisomy X was detected in 4 cases (12.9%). In 3 of 15 (20%) cases analyzed for chromosome 3 trisomy was observed. Trisomy 3 was associated with trisomy 7 and X or with trisomy 7 alone. The hybrid capture test was performed in 16 patients of this group. Two patients were positive for HPV probe A, 9 for probe B, and 2 for A and B, and 3 patients were negative. Twenty-three of the 29 patients (79.3%) with HSIL showed trisomy 7. Twelve of the 29 patients (41.3%) had an additional trisomy X. Single trisomy X was seen in only 2 cases (6. 9%). Twenty-two patients with HSIL were tested also for chromosome 3. Nine of the 22 patients (40.9%) showed trisomy 3, associated with trisomy 7 or with trisomy 7 and X. In 25 of the 29 patients HPV detection by the hybrid capture system was performed. HPV probe B was positive in 15 cases (60%). One patient was positive for both probes, A and B. Nine (36%) of the patients with HSIL were negative for both HPV probes. No positivity was observed for HPV probe A alone.

CONCLUSION

Our data confirm the pivotal role of HPV in cervical carcinogenesis as it seems to cause changes in the chromosomal pattern of premalignant lesions. Additionally, trisomy 7 may be considered an early event in cervical carcinogenesis, persisting and increasing with progression of the lesion. The roles of trisomy 3 and X need further evaluation.

The molecular genetics of cervical carcinoma

In the pathogenesis of cervical carcinoma there are three major components, two of them related to the role of human papillomaviruses (HPV). First, the effect of viral E6 and E7 proteins. Second, the integration of viral DNA in chromosomal regions associated with well known tumour phenotypes. Some of these viral integrations occur recurrently at specific chromosomal locations, such as 8q24 and 12q15, both harbouring HPV18 and HPV16. And third, there are other recurrent genetic alterations not linked to HPV. Recurrent losses of heterozygosity (LOH) have been detected in chromosome regions 3p14-22, 4p16, 5p15, 6p21-22, 11q23, 17p13.3 without effect on p53, 18q12-22 and 19q13, all of them suggesting the alteration of putative tumour suppressor genes not yet identified. Recurrent amplification has been mapped to 3q+ arm, with the common region in 3q24-28 in 90% of invasive carcinomas. The mutator phenotype, microsatellite instability, plays a minor role and is detected in only 7% of cervical carcinomas. The development of cervical carcinoma requires the sequential occurrence and selection of several genetic alterations. The identification of the specific genes involved, and their correlation with specific tumour properties and stages could improve the understanding and perhaps the management of cervical carcinoma.

p53 codon 72 polymorphism and risk of cervical cancer in UK

BACKGROUND

A polymorphism at codon 72 of the human tumour-suppressor gene, p53, results in translation to either arginine or proline. A recent report suggested that the risk of human-papillomavirus-associated cervical cancer in white women is higher for those homozygous for the arginine allele than for those who are heterozygous. We examined a similar number of cervical cancers and a larger control group for their p53 codon 72 polymorphism status to see if we could confirm this result.

METHODS

Three different groups of UK white women were studied: 96 who had volunteered to take part in a trial of ovarian-cancer screening; 150 attending for routine antenatal care in the Oxford region; and 50 women with cervical cancer. DNA from peripheral blood samples and from archival tissue samples was examined by PCR with allele-specific primers.

FINDINGS

The proportions of individuals homozygous for the arginine allele, homozygous for the proline allele, and heterozygous for the two alleles were 59%, 4%, and 36% among women screened for ovarian cancer; 65%, 8%, and 27% among the antenatal-care group; and 54%, 6%, and 40% in women with cervical cancer. Chi2 analysis showed no significant differences in these proportions.

INTERPRETATION

In the population studied, individuals homozygous for the arginine variant of codon 72 of the p53 gene were not at increased risk of cervical cancer.

Absence of p53 mutations in benign and pre-malignant male genital lesions with over-expressed p53 protein

Mutations of the tumor-suppressor gene p53 are common in epithelial tumors. Clonal mutations of p53 have been found in cervical and vulvar carcinomas negative for human papillomavirus (HPV), though at least in cervical cancer HPV infection and p53 mutations are not mutually exclusive. We have previously shown that about 40% of male genital warts and bowenoid papulosis lesions exhibit immunohistochemically detectable aberrant p53 protein, irrespective of the presence of HPV DNA. We studied p53 mutations in exons 4-8 with SSCP and sequencing in 13 male patients with 1 to 3 therapy-resistant genital warts or intra-epithelial neoplasias each and in 4 patients with penile squamous cell carcinoma. Thus, 13 genital warts, 6 bowenoid papulosis, 1 Queyrat's erythroplasia and 1 carcinoma in situ were studied. p53 protein was detected immunohistochemically, and HPV status was analyzed with DNA in situ hybridization and amplification of HPV-specific DNA. There was no correlation between p53 protein expression and HPV status. No mutations in exons 5-8 of the p53 gene were found in any of the lesions, and furthermore, no exon 4 mutations were found in lesions positive in p53 immunohistochemistry. In conclusion, overexpression of p53 does not indicate a p53 mutation in male genital warts, pre-malignant lesions or malignant squamous cell carcinomas. Our study thus suggests that p53 mutations are not important, or at least not early, events in male genital carcinogenesis.

Loss of heterozygosity in clinical stage IB cervical carcinoma: relationship with clinical and histopathologic features

Loss of heterozygosity (LOH) has been shown to be an important prognostic factor in a variety of malignant neoplasms. The relationship between LOH and established histopathological prognostic factors in cervical carcinoma has not been examined. We studied LOH in 58 FIGO stage IB cervical cancers treated by radical hysterectomy. In a randomly selected subset of 37 of these cases, LOH was examined using markers for all 41 chromosomal arms. Seventy-six percent of the 58 cases and 95% of the extensively studied cases showed LOH at one or more loci. The three most common sites of LOH were 3p21, 6p24-p23, and 11q23.3. In the extensively studied group, LOH on 11q was associated with extensive lymphvascular space invasion (P = .009) and less deeply invasive tumor (P = .042). There was a trend for tumors with LOH on 11q to recur, but this was not statistically significant. No correlation between the presence of LOH on 3p or 6p and lymphvascular space invasion or tumor depth was present. There was no correlation between the number of sites of LOH or between the presence of LOH on 3p, 6p, and 11q and the presence of metastatic tumor in regional lymph nodes, histologic type (squamous v nonsquamous), tumor differentiation, maximum tumor size, degree of inflammation, pattern of invasion, mitotic rate, or clinical recurrence. In summary, tumors with 11q LOH may behave in a more aggressive fashion. Future studies of LOH in cervical carcinoma should include histopathological prognostic information so that the relationship between LOH and these factors can be determined on larger numbers of patients.

Molecular events in uterine cervical cancer

OBJECTIVE

To review the literature regarding the molecular events which occur in the development of uterine cervical cancer, with particular reference to human papillomavirus (HPV) infection.

METHODOLOGY

Bibliographic searches of Medline and the ISI citation databases using appropriate keywords, including the following: papillomavirus, cervix, pathology, cyclin, chromosome, heterozygosity, telomerase, smoking, hormones, HLA, immune response, HIV, HSV, EBV.

CONCLUSIONS

It has become clear that most cervical neoplasia, whether intraepithelial or invasive, is attributable in part to HPV infection. However, HPV infection alone is not sufficient, and, in a small proportion of cases, may not be necessary for malignant transformation. There is increasing evidence that HPV gene products interfere with cell cycle control leading to secondary accumulation of small and large scale genetic abnormalities. This may explain the association of viral persistence with lesion progression but, in many patients, secondary factors, such as smoking and immune response, are clearly important. However, the mechanisms involved in the interaction between HPV and host factors are poorly understood.

Loss of heterozygosity for defined regions on chromosomes 3, 11 and 17 in carcinomas of the uterine cervix

Loss of heterozygosity (LOH) frequently occurs in squamous cell carcinomas of the uterine cervix and indicates the probable sites of tumour-suppressor genes that play a role in the development of this tumour. To define the localization of these tumour-suppressor genes, we studied loss of heterozygosity in 64 invasive cervical carcinomas (stage IB and IIA) using the polymerase chain reaction with 24 primers for polymorphic repeats of known chromosomal localization. Chromosomes 3, 11, 13, 16 and 17, in particular, were studied. LOH was frequently found on chromosome 11, in particular at 11q22 (46%) and 11q23.3 (43%). LOH on chromosome 11p was not frequent. On chromosome 17p13.3, a marker (D17S513) distal to p53 showed 38% LOH, whereas p53 itself showed only 20% LOH. On the short arm of chromosome 3, LOH was frequently found (41%) at 3p21.1. The beta-catenin gene is located in this chromosomal region. Therefore, expression of beta-catenin protein was studied in 39 cases using immunohistochemistry. Staining of beta-catenin at the plasma membrane of tumour cells was present in 38 cases and completely absent in only one case. The tumour-suppressor gene on chromosome 3p21.1 may be beta-catenin in this one case, but (an)other tumour-suppressor gene(s) must also be present in this region. For the other chromosomes studied, 13q (BRCA-2) and 16q (E-cadherin), only sporadic losses (< 15% of cases) were found. Expression of E-cadherin was found in all of 37 cases but in six cases the staining was very weak. No correlation was found between clinical and histological parameters and losses on chromosome 3p, 11q and 17p. In addition to LOH, microsatellite instability was found in one tumour for almost all loci and in eight tumours for one to three loci. In conclusion, we have identified three loci with frequent LOH, which may harbour new tumour-suppressor genes, and found microsatellite instability in 14% of cervical carcinomas.

Loss of heterozygosity of the retinoblastoma and p53 genes in primary cervical carcinomas with human papillomavirus infection

OBJECTIVE

Paired DNA samples from 55 primary uterine cervical carcinomas and normal bloods were studied for chromosomal allelic loss (loss of heterozygosity; LOH) of the retinoblastoma (Rb) and p53 gene loci by polymerase chain reaction (PCR) or PCR-restriction fragment length polymorphism analysis. All the study samples contained at least one of the oncogenic human papillomavirus (HPV) type 16 and/or 18 sequences. And the relationships between allelic losses of these genes and conventional clinicopathological parameters were evaluated.

METHODS

In order to detect LOH of the Rb gene in cervical cancers, we analyzed four polymorphic intronic sites (intron 1, 17, 20, and 25) of the Rb gene and one additional microsatellite near the Rb locus (D13S118). For detection of the LOH in p53, three intragenic polymorphisms (exon 1, exon 4, intron 6) and one microsatellite distal to the p53 gene (D17S5) were examined.

RESULTS

By analyzing this system, we could increase the heterozygosity of the Rb and p53 loci up to 0.91 and 1, respectively. The observed allelic loss rates of the Rb and p53 loci in informative cases were 14% (7/50) and 5.5% (3/55), respectively. The patients with LOH at the D13S118 locus also had the allelic loss of the Rb gene, whereas only one of the four patients with LOH at the D17S5 locus showed a concomittant allelic loss of the p53 gene. The frequency of cervical cancer with one LOH at the Rb or p53 loci was 20% (11/55). No shifted bands were observed in the PCR-single-strand conformation polymorphism analysis of the p53 gene. The LOH of the Rb or p53 gene was not significantly associated with other parameters including clinical stage, histological type, degree of differentiation, status of HPV infection, and p53 gene mutation.

CONCLUSION

Concerning the results above, we conclude that the allelic imbalance of the Rb or p53 gene itself is not implicated as a major contributing factor in the malignant transformation or the tumor progression in HPV-positive uterine cervical cancers.

Cytogenetics of carcinoma of the cervix uteri: a review

Cytogenetic studies on carcinoma of the cervix have shown the nonrandom involvement in structural changes of a number of chromosomes, particularly chromosomes 1, 3, 5, 11, and 17. Apart from chromosome 5, where a short-arm isochromosome is the commonest derivative, these chromosomes most often undergo short-arm deletions. Notably, chromosome 17 may have undergone structural changes that result in loss of the tumor suppressor gene TP53 on 17p; chromosomal translocations may in some tumors perform the function that in others is provided by human papillomavirus protein complexing with and inactivating this gene. The chromosome 1 changes may sometimes result in the duplication of long-arm material. Although there have been few comparable studies on the preinvasive stages of cancer of the cervix, it is clear from earlier chromosome and quantitative DNA studies that, except perhaps in the "mild dysplasias," there already is clonal development that has resulted in an aneuploid population with a mode that, as in carcinomas, is either in the diploid or (in 50% or more) triploid-tetraploid range; spindle defects are prominent and may result in unequal segregation of the chromosomes into the daughter cells. Further characterization of the chromosomal changes in carcinoma of the cervix, and more particularly its preinvasive stages, using the new molecular DNA techniques is eagerly awaited.

Molecular biology of cervical cancer and its precursors

Cervical cancer develops from well-defined precursor lesions referred to as either cervical intraepithelial neoplasia or squamous intraepithelial lesions. It is now known that specific types of human papillomaviruses (HPV) are the principal etiologic agents for both cervical cancer and its precursors. The high-oncogenic-risk HPV types associated with invasive cervical cancer produce two oncoproteins, designated E6 and E7, which interact with endogenous cell cycle regulatory proteins, including p53 and Rb. The interaction of virally derived and endogenous cellular proteins converges in deregulation of cell cycle progression and appears to be critical for the development of cervical cancers. However, the development of cervical cancer is a multistep process that cannot be explained simply by infection with specific types of HPV. One additional event that appears to play a role in tumor progression is integration of HPV DNA into the host genome. Integration of HPV DNA frequently disrupts the E2 open reading frames, resulting in overexpression of the E6 and E7 oncoproteins and possibly causing genomic instability. Additional cofactors and mutational events may be important in the pathogenesis of invasive cervical cancers and may include chromosomal rearrangements, loss of constitutional heterozygosity, and proto-oncogene activation.

Expression of p53 protein related to human papillomavirus and DNA ploidy in superficial esophageal carcinoma

We examined the p53 protein and human papilloma virus (HPV) by immunohistochemistry and DNA ploidy by cytofluorometry in paraffin-embedded esophageal carcinoma tissue specimens. Sixty-one patients with superficial esophageal carcinoma were operated on between 1983 and 1991 without any prior treatment. Immunostaining of the anti-p53 protein antibody (CM1) was positive in 32 carcinomas (52%). Patients with p53-positive tumors had a poorer outcome than those with p53-negative tumors (P < 0.05). In addition, patients with p53-positive tumors did not have any characteristic site of relapse. Only 5 of the 61 patients (8.2%) had HPV-positive tumors. One of these 5 carcinomas expressed both p53 protein and HPV. Three patients with HPV-positive tumors which had invaded the submucosal layer died of relapse. A determination of DNA ploidy revealed 30 patients with aneuploid tumors, 13 with polyploid tumors and 18 with diploid tumors. The outcome of the patients with aneuploid tumors was worse than that of the patients with diploid tumor (P < 0.05). p53 protein expression was not associated with DNA ploidy; however, the 16 patients who had both p53-positive and aneuploid tumors had a worse prognosis than patients with p53-negative and aneuploid tumors (P < 0.01). These findings suggest that p53 protein expression in conjunction with DNA ploidy may be a useful indicator in evaluating the prognosis of patients with superficial esophageal carcinoma.

p53 mutation and MDM2 amplification are rare even in human papillomavirus-negative cervical carcinomas

BACKGROUND

Mutation of the p53 tumor suppressor gene is the most commonly found genetic alteration in human cancer. The E6 gene product of human papillomavirus (HPV) 16 and 18 can inactivate the p53 protein by promoting its degradation. Because most HPV-positive cervical carcinoma cell lines contain wild-type p53 whereas HPV-negative cell lines have point mutations in the p53 gene, a major role in the development of HPV-negative cervical cancer has been attributed to p53. Recent studies, however, have observed no consistent presence of p53 mutation in HPV-negative primary cervical carcinomas. The MDM2 oncogene, which forms an autoregulatory loop with the wild-type p53 protein, has been found amplified in a high percentage of human sarcomas, thus abolishing the antiproliferative function of p53.

METHODS

Forty-three primary cervical carcinomas and 10 autopsy-derived distant metastases from one patient were examined for p53 mutation and MDM2 amplification. These tumors had been selected from 238 cervical cancers that had been HPV-typed by Southern blot hybridization and polymerase chain reaction as a representative sample for their HPV status and their clinicopathologic characteristics. Seventeen of the cases had a remarkably good or poor clinical outcome. Human papillomavirus DNA sequences had been detected in 30 of these 43 primary tumors and 13 were negative for HPV by both methods. p53 mutation in the highly conserved exons 5-8 was studied by single-strand conformation polymorphism analysis and direct sequencing. MDM2 amplification was analyzed by Southern blot hybridization.

RESULTS

Only two missense point mutations and one nucleotide sequence polymorphism were detected: a TAC-->TGC transition in codon 234 in exon 7, resulting in a Tyr-->Lys substitution, a CGT-->TGT transition in codon 273 in exon 8, resulting in an Arg-->Cys substitution and a polymorphism (CGA-->CGG) in codon 213 in exon 6. Both tumors revealing the point mutations were HPV-negative carcinomas. Amplification of the MDM2 gene was observed in 1 of the 53 specimens tested.

CONCLUSIONS

In contrast to data derived from cultured cervical carcinoma cell lines and primary sarcomas, these results indicate that p53 mutation and amplification of the MDM2 oncogene are rare even in HPV-negative primary cervical carcinomas. However, to the authors; knowledge, this is the first observation of MDM2 amplification in humans outside sarcomas and neuroepithelial tumors.

Chromosome abnormalities and p53 expression in a small cell carcinoma of the bladder

Chromosome studies on a highly malignant tumor, a small cell carcinoma of the bladder (the first to be studied cytogenetically), showed a hypertriploid mainline and a hypertetraploid minor line. Extensive chromosomal rearrangements were present in both lines, some rearranged chromosomes being seen in only one of the lines, while others, derived from chromosomes 6, 9, 11, 13, and 18, were seen in both. Although different giant chromosomes were present in the two lines, they shared a possibly significant common feature: multiple copies of 2q. DNA flow cytometry confirmed that the tumor had a hypertriploid main mode and showed that dysplastic surface epithelium present in the histologic material also had a hypertriploid DNA index. p53 expression in the tumor was demonstrated by flow cytometry.

Loss of heterozygosity on the short arm of chromosome 17 in uterine cervical carcinomas

DNA samples from 26 cervical carcinoma and normal tissue pairs were studied by restriction fragment length polymorphism (RFLP) analysis to determine the frequency of loss of heterozygosity (LOH) on 17p. Allelic loss in the p13.1 region of chromosome 17, known to contain the TP53 locus, was not detected in any of 10 informative cases. Instead, LOH was detected on 17p13.3 in eight (40%) of 20 informative cases with at least one of two 17p13.3 markers. Examination of the intragenic region of p53 in the same samples using polymerase chain reaction (PCR)-RFLP analysis showed no LOH in the gene (none of 16 informative individuals).

Surrogate endpoint biomarkers for cervical cancer chemopreventive trials

Cervical intraepithelial neoplasia (CIN) represents a spectrum of epithelial changes that provide an excellent model for developing chemopreventive interventions for cervical cancer. Possible drug effect surrogate endpoint biomarkers are dependent on the agent under investigation. Published and preliminary clinical reports suggest retinoids and carotenoids are effective chemopreventive agents for CIN. Determination of plasma and tissue pharmacology of these agents and their metabolites could serve as drug effect intermediate endpoints. In addition, retinoic acid receptors could serve a both drug and biological effect intermediate endpoints. Possible biological effect surrogate endpoint biomarkers include cytomorphological parameters, proliferation markers, genomic markers, regulatory markers, and differentiation. Given the demonstrated causality of human papillomavirus (HPV) for cervical cancer, establishing the relationship to HPV will be an essential component of any biological intermediate endpoint biomarker. The pathologic effect surrogate endpoint biomarker for cervical cancer is CIN, used clinically for years. The desired effect for chemopreventive trials is complete regression or prevention progression. In planning chemoprevention trials, investigators need to consider spontaneous regression rates, the subjective nature of detecting CIN, and the impact of biopsy on regression. If intermediate endpoint biomarkers that met the above criteria were available for cervical cancer, then new chemopreventive agents could be rapidly explored. The efficacy of these new agents could be determined with a moderate number of subjects exposed to minimal risk over an acceptable amount of time. The impacts on health care for women would be significant.

Derivative chromosome, der(17;22)(q10;q10), in two carcinomas of the cervix uteri and one of the skin

In a previous study, we described 17p+ chromosomes in about 40% of carcinomas of the cervix, but it was usually not possible to identify the additional material on the short arm of the chromosome 17. Here we report an apparently identical rearranged chromosome in two squamous cell carcinomas of the cervix and one of the skin, in which the whole of 17p has been replaced by the long arm of a chromosome 22: der(17;22)(q10;q10), suggesting that this rearrangement may represent a significant step in the development of carcinomas of the cervix and other sites.

p53 mutations in cervical carcinogenesis--low frequency and lack of correlation with human papillomavirus status

p53 gene aberrations are common in human malignancies, and recent studies suggest that in cervical carcinoma p53 function is inactivated either by complex formation with human papillomavirus (HPV) E6 product or by gene mutation. Using polymerase chain reaction (PCR) followed by denaturing gradient gel electrophoresis (DGGE), we examined the mutational status of the four 'hotspot' regions of the p53 gene in 47 primary cervical carcinomas. HPV status was determined, also by PCR. In 20 of these cases, we examined for loss of heterozygosity (LOH) on chromosome 17p13. In the 47 carcinomas, and in a further 68 biopsy specimens from normal, premalignant and malignant cervix, we investigated aberrant immunocytochemical expression of p53. Immunocytochemically, abnormal p53 expression was detected in 13 of 115 cases (8/57 carcinomas). Somatic mutation in p53 was detected in 1 of 47 cervical carcinomas; 36 were positive for HPV 16, 18 or 33. A low level of allele loss (3 out of 20 cases) was detected on chromosome 17p, occurring in both HPV-positive and HPV-negative cases, and in cases with and without p53 mutations. We conclude that somatic mutation in the hotspot regions of the p53 gene occurs infrequently in cervical carcinomas; that immunocytochemically detectable levels of p53 are also infrequent; and that there is no consistent correlation between p53 mutational status, LOH on chromosome 17p or HPV status in these cancers.

The polymerase chain reaction. Applications in dermatology

Within the space of the last 5 years, application of the revolutionary in vitro method of deoxyribonucleic acid (DNA) amplification known as the polymerase chain reaction (PCR), has become ubiquitous. The rapidly increasing number of clinical and research articles utilizing this technology, both in the dermatologic and general medical literature, requires one to have at least a basic understanding of how the PCR is conducted, what it has to offer, and the potential shortcomings. Such knowledge will hopefully allow a more critical appraisal of an increasingly complex literature. This review aims to describe the methodology and medical applications of this powerful technique with special consideration to the increasing role PCR may have on dermatologic research and practice.

Cervical carcinoma: low frequency of allele loss at loci implicated in other common malignancies

Twenty cervical carcinomas were examined for loss of heterozygosity (LOH) using 22 RFLP markers, which mapped to regions of putative oncosuppressor gene loci, identified as candidates in other common solid tumours. Allele losses were identified in six of the eight chromosomal arms examined, but at a significantly lower frequency than that reported in other common solid tumours. No association was observed between allele losses at any chromosomal location and the presence or integration of 'high risk' types of HPV determined by a sensitive, specific PCR method. HPV 16, 18 or 33 were found in the majority (75%) of these tumours. We have looked at only a limited subset of chromosomal regions, but the results, so far, imply that carcinoma of the cervix may arise by different molecular events than other common solid tumours, and support the view that one of the distinctive events may be infection with HPV. Alternatively, similar molecular events may be occurring, but in regions of the genome not yet identified as targets in other solid tumours.