HPV-associated cervical cancers show frequent allelic loss at 3p14 but no apparent aberration of FHIT mRNA

Role of 5'-CpG island hypermethylation of the FHIT gene in cervical carcinoma

OBJECTIVE

The abnormal expression of fragile histidine triad (FHIT) gene has been frequently reported in a variety of epithelial malignancies including cervical carcinoma. Furthermore, in a recent study it was proposed that transcriptional inactivation of FHIT, as a consequence of aberrant 5'-CpG island methylation, plays an important role in the carcinogenesis of human cervical carcinoma. The authors sought to determine whether abnormal FHIT transcription occurs in human cervical carcinoma, and if so, whether this abnormal expression is associated with aberrant 5'-CpG island methylation. In addition, the clinical significance of FHIT inactivation was investigated in Korean women with cervical cancer.

METHODS

To examine for abnormal transcripts of the FHIT gene, quantitative RT-PCR, genomic DNA-PCR and nonisotopic RT-PCR-SSCP analysis were performed using the standard method. The methylation status was determined by methylation specific PCR and bisulfite DNA sequencing.

RESULTS

The FHIT gene was down-regulated in 15 of 58 (25.9%) cervical carcinomas. FHIT promoter hypermethylation was detected in 15 of 15 (100%) abnormally expression in cervical carcinomas. Bisulfite DNA sequencing confirmed these findings and a significant correlation was found between CpG site hypermethylation and low FHIT expression. However, no significant correlation was found between reduced FHIT expression and clinicopathological characteristics.

CONCLUSION

In this study, FHIT inactivation in cervical cancer was found to be strongly correlated with 5'-CpG island hypermethylation rather than a genetic alteration. Furthermore, no significant relation was found between a lack of FHIT expression and the prognostic factors of cervical cancer in our Korean cohort.

Chromosomal gain of 3q and loss of 11q often associated with nodal metastasis in early stage cervical squamous cell carcinoma

BACKGROUND/PURPOSE

Cervical cancer remains a health problem among women worldwide. Delineation of genetic changes is critical to understanding the molecular basis of tumor progression, as well as for identifying genetic markers for early identification of patients at high risk for a poor outcome.

METHODS

To provide comparative genomic hybridization data for cervical squamous cell carcinoma in Taiwan, and to gain further insight into genetic markers associated with lymph node metastasis of this disease, we performed comparative genomic hybridization analysis of 30 consecutive cases of cervical squamous cell carcinoma (24 stage IB and 6 stage IIB).

RESULTS

The results disclosed that higher staged tumors or those with lymph node metastasis had more chromosomal imbalances. The commonly recurrent chromosomal imbalances were gains of 3q (46.7%), 1q (36.7%) and 8q (20.0%) and losses of 11q (36.7%), 3p (33.3%), 6q (23.3%), and 2q (20.0%). The frequencies of these chromosomal imbalances in stage IB and IIB tumors did not differ significantly. However, when compared with tumors without lymph node metastasis, the loss of 11q14-q22 (5/9 vs. 3/21, p = 0.019) and gains of 3q11-q22 and 3q26-qter (6/9 vs. 5/21, p = 0.026) were significantly more prevalent in tumors with lymph node metastasis.

CONCLUSION

The results suggest that certain tumor-associated genes residing on 3q and 11q warrant further investigation to elucidate their role in the progression of this disease.

A novel approach to simultaneously scan genes at fragile sites

BACKGROUND

Fragile sites are regions of the genome sensitive to replication stress and to exposure to environmental carcinogens. The two most commonly expressed fragile sites FRA3B and FRA16D host the histidine triad (FHIT) and WW domain containing oxidoreductase (WWOX) genes respectively. There is growing evidence that both genes contribute to cancer development and they are frequently altered by allelic and homozygous deletions in a variety of tumors. Their status is linked to prognosis in several malignancies and they are thought to be involved in early tumorigenesis. The loci for FHIT and WWOX both span over a megabase but the genes encode for small transcripts. Thus the screening of intragenic deletion can be difficult and has relied on loss of heterozygosity LOH assays, or genomic arrays.

METHODS

Multiplex ligation dependent probe amplification MLPA, allows for the detection of deletions/duplications and relative quantification of up to 40 specific probes in a single assay. A FHIT/WWOX MLPA assay was designed, applied and validated in five esophageal squamous cell carcinoma ESCC, cell lines established in South Africa where this cancer is of high prevalence. Sixteen probes covered all FHIT exons and 7 probes covered WWOX.

RESULTS

Both homozygous and hemizygous deletions were detected in FHIT, in four of the cell lines with a preferential deletion of exons 5 and 4. Chromosome 3 short arm was present in normal copy number indicating that deletions were site specific. In contrast WWOX was not altered in any cell lines. RT-PCR expression pattern paralleled the pattern of deletions. Ten primary ESCC tumor specimens were subsequently screened with this assay. FHIT exon deletions were found in four of them.

CONCLUSION

This method offers an alternative to loss of heterozygosity studies. Simultaneous scanning of FHIT and WWOX exons in the context of early tumorigenesis and tumor progression, may help clarify the mechanistic events related to cancer development which are not revealed by immuno histochemistry assays. The presence of site specific deletions of FHIT in these cell lines and primary tumors support its possible role in South African ESCC and justifies a wider screening.

5'-CpG island methylation of the FHIT gene is associated with reduced protein expression and higher clinical stage in cervical carcinomas

Aberrant transcription of the FHIT gene has been observed in many solid tumors, suggesting that 5'-CpG island methylation of the FHIT gene is involved in tumor development. The authors investigated the status of the 5'-CpG island methylation of the FHIT gene and protein expression in a series of 40 cervical carcinomas and 10 normal cervical epithelial samples, and correlated the data with clinicopathological findings. Methylation-specific PCR was applied to detect the incidence of the 5'-CpG island methylation, and immunohistochemistry was used for FHIT protein staining. 5'-CpG island methylation of the FHIT gene was detected in 40% (16/40) of the cervical cancer samples and in none of normal cervical epithelial specimens. Furthermore, the 5'-CpG island methylation was positively associated with clinical stage (p=.002). All the normal cervical epithelial samples (10/10) and 90% (36/40) of the cervical carcinomas were positive when the unmethylated primer pair was applied. Of the 16 cervical carcinomas with 5'-CpG island methylation of the FHIT gene by PCR, 15 showed reduced FHIT protein expression. This study suggests that 5'-CpG island methylation plays an important role in inactivation of the FHIT gene in cervical cancer.

Hypermethylation of the tumor suppressor gene RASSFIA and frequent concomitant loss of heterozygosity at 3p21 in cervical cancers

Loss of heterozygosity (LOH) at chromosome 3p21 is frequent in cervical cancers. The candidate tumor suppressor gene, RASSF1A located at 3p21.3, is found to be inactivated in several major human cancers, implicating its significance in carcinogenesis. We aimed to investigate the status of RASSF1A in cervical cancers. The mutation and methylation status of RASSF1A were analysed in 4 cervical cancer cell lines, 50 primary cervical cancers including 33 squamous cell carcinoma (SCC), 17 adenocarcinoma (AC) and 11 normal controls. The primary cancer samples were also detected for LOH at 3p21 and human papillomavirus (HPV). Hypermethylation of RASSF1A was detected in 30% of SCC, 12% of AC and in 1 of the 4 cancer cell lines but was absent in all normal cases. Methylation of the cancer cell line was associated with loss of gene expression, which was restored by demethylation. About 67% (8 of 12) of hypermethylated primary cancers showed concomitant LOH at 3p21. No somatic mutation was found in all primary cancer samples or cell lines but 2 cases showed germline polymorphism at codon 133. Oncogenic HPV DNAs were found in most cancer samples. No correlation was detected between RASSF1A-hypermethylation or LOH at 3p21 and age of patient, HPV genotype, tumor grade and stage. Hypermethylation of RASSF1A occurs in a subset of cervical cancers, among which concomitant LOH at 3p21 is common. The results supported that RASSF1A may be one of the cervical cancer-related tumor suppressor genes located at 3p21 regions.

Abnormal FHIT expression profiles in cervical intraepithelial neoplastic (CIN) lesions

Abnormal fragile histidine triad transcripts were found in 20-30% of CIN2/3 lesions and 11% of normal cervical biopsies by RT-PCR. Bi-allelic loss of the fragile histidine triad gene and the loss of fragile histidine triad protein expression detectable by immunochemical staining with a polyclonal fragile histidine triad specific antibody was rare. The genomic changes showed no association with the presence of human papillomavirus types which carry high risk for cervical cancer (high risk human papillomavirus) as assessed by a type-specific multiplex PCR. The presence of abnormal fragile histidine triad transcripts in a subset of CIN2/3 lesions with no high risk human papillomavirus suggests that this could be an independent risk factor associated with an alternative carcinogenic pathway.

The molecular biology of cervical cancer

Cervical cancer remains a major worldwide health problem, especially in developing countries. Over the last few decades many advancements have been made in determining the molecular genetics of the development of cancer. This paper attempts to summarize the major disturbances in cellular function known to date to play a role in the development of cervical cancer. The role of human papillomavirus (HPV) infection in the development of cervical cancer is a major player in the genetic abnormalities described thus far. The effects of HPV E6 and E7 on important cell cycle genes are discussed. As oncogenes and tumor suppressor genes have been described in the different types of cancer, their possible role in cervical cancer has been investigated. The possible role of angiogenesis and angiogenic factors is described. Because of the importance of HPV infection in the development of cervical cancer, the role of the body's immune function in this cancer is also under study, and the results of these findings are summarized. Although a complete paradigm of the development of cervical cancer from normal cervical epithelium is not yet known, continued study in this area will hopefully lead to a defined progression of molecular and immunologic abnormalities that cause the disease. The goal would be to use this information to help prevent and/or treat cervical cancer in the future.

Expression of truncated FHIT transcripts in cervical cancers and in normal human cells

To analyse FHIT transcription patterns in cervical cancer, a series of primary cervical tumors and normal control samples were studied using RT-PCR. Full length and truncated FHIT transcripts were detectable in all samples tested. Interestingly, the expression of truncated FHIT transcripts by primary epithelial cells in vitro was associated with confluency. The breakpoints of most transcript deletions coincided with genuine splice site sequences, suggesting that they resulted from alternative splicing. These findings demonstrate that truncated FHIT transcripts are commonly detected in both normal and tumor tissues, and suggest that these altered transcripts are not causally related to tumorigenesis in cervical cancer.

FHIT (fragile histidine triad) gene analysis in cervical intraepithelial neoplasia

OBJECTIVE

Recently a candidate tumor suppressor gene, FHIT (fragile histidine triad), was identified at chromosome 3p14.2. Abnormality of this gene has been observed in a variety of human tumors. Although aberrant FHIT transcripts in a substantial percentage of cervical cancer cell lines and primary cervical tumors were also noted, some other studies revealed different results. Therefore, its association with the development of cervical cancer is still debatable. Because allelic loss in chromosome 3p is also a frequent finding in cervical intraepithelial neoplasia (CIN), we compared the transcription pattern and expression of FHIT in the preinvasive cervical lesions and normal cervical epithelia to investigate its possible role in cervical carcinogenesis.

METHODS

Thirty-five consecutive CIN lesions taken from conization specimens and 33 normal cervical epithelial tissues taken from hysterectomy for benign diseases were included in this study. Total RNA was extracted from the pathology-confirmed tissue samples and first-strand cDNA was synthesized. It was amplified using a nested reverse transcription polymerase chain reaction (RT-PCR) method. The PCR products were then subjected to subcloned sequence analysis. Paraffin blocks from all of the samples were selected and prepared for immunohistochemical study with an anti-FHIT polyclonal antibody.

RESULTS

All the cDNAs of CIN and normal cervical epithelial tissues showed the expected size of RT-PCR product. However, 7 of the 35 (20%) CIN lesions and 5 of the 33 (15%) normal cervical epithelia also presented aberrant transcripts in addition to the normal-sized transcript of FHIT. Deletion of the cDNA segment covering exon 4 to exon 8 was the most frequent finding in the cases that showed abnormal FHIT transcripts. FHIT protein was intermediately or strongly expressed in most of the CIN lesions and normal squamous epithelia. However, reduced or absent FHIT expression was observed heterogeneously in the 7 CIN lesions and 5 normal cervices in which aberrant FHIT transcripts were detected.

CONCLUSION

Because the normal-sized FHIT transcript was present robustly in all of the CIN lesions and the abnormal FHIT transcripts occurred with similar frequency and pattern in the CIN lesions and normal cervical tissues, we suggest that abnormal FHIT transcription might not be causal in the early process of cervical carcinogenesis.

Primary cervical carcinomas show 2 common regions of deletion at 3P, 1 within the FHIT gene: evaluation of allelic imbalance at FHIT, RB1 and TP53 in relation to survival

Chromosome arm 3p is re-arranged in many tumor types, including cervical carcinomas. Putative tumor-suppressor genes on 3p have been proposed, including the FHIT gene, which maps to chromosome band 3p14.2. We have analyzed 79 primary cervical carcinomas for allelic imbalance (AI) at 17 chromosome 3 loci, including 3 within the FHIT gene. Expression of the FHIT gene was evaluated after immunohistochemistry with an antibody against the pFHIT protein. Previously determined human papillomavirus status, defined after in situ hybridization, showed type 16 or 18 in 56/77 tumors. Tumors were also analyzed for AI at loci within the RB1 (chromosome band 13q14.2) and the TP53 (17p13) genes for AI. AI was found at 1 or more 3p loci in 50/79 tumors, at frequencies ranging from 30% to 52% at the individual loci. Two smallest regions of overlapping deletion (SROs) were found, 1 including parts of the FHIT gene (SRO flanked by D3S1481 and D3S1313) and another more distal SRO between D3S32 and D3S1286. FHIT protein expression was reduced in 57/69 (83%) tumors but not associated with AI at FHIT loci (p = 0.56). AI was found in TP53 and RB1 in 18% and 29% of the samples, respectively. Relapse-free survival was associated with AI in the TP53 gene in both a univariate (p = 0.0003) and a multivariate (p = 0.004) analysis. This study confirms a high frequency of AI at chromosome arm 3p in primary cervical carcinomas. The AI results and the reduced FHIT protein staining indicate that FHIT alterations are important in cervical carcinogenesis.

FHIT gene mutations and single nucleotide polymorphism in Indian oral and cervical squamous cell carcinomas

Genetic alterations at the FHIT (fragile histidine triad) tumor suppressor gene have been found in various human cancers. We have made an attempt to find point mutations of this gene in two different cancers from India, with entirely different etiologic factors: oral cancer (55 samples) caused by chewing tobacco and cervical cancer (43 samples) caused mainly by HPV (human papilloma virus) infection. Analysis of tumor DNA by the polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) method was performed on each of FHIT exons 5-9 individually, using exon-flanking primers. Two different mutations were identified in both oral and cervical tumors: one at the second nucleotide 3' to the termination codon (TGA) in exon 9 and the other at the ninth nucleotide upstream to the beginning of exon 9. These results indicate that mutations in the FHIT gene are rare events in these tumors in India (approximately 4%). In addition, we found a single nucleotide FHIT gene polymorphism which is due to T/A replacement at 17 nucleotides upstream to exon 9 where the A allele is 0.6 of the population.

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.

Allelic losses at chromosome 3p are seen in human papilloma virus 16 associated transitional cell carcinoma of the cervix

OBJECTIVE

Transitional cell carcinomas (TCCs) of the cervix are rare neoplasms of the female genital tract. Although these tumors display urothelial differentiation, there is controversy regarding their histogenetic relationship to squamous cell carcinomas (SCC) of the cervix versus transitional cell carcinomas of the bladder.

METHODS

We performed partial allelotyping of five TCCs of the cervix using 23 polymorphic markers located on chromosomes 3p and 9, which demonstrate frequent and early losses in cervical SCC and urothelial TCC, respectively. Multiplex polymerase chain reaction was used on DNA extracted from archival paraffin-embedded tissue using precise microdissection. Additionally, P53 gene mutation analysis was performed using single-strand confirmation polymorphism (SSCP) and the presence of human papilloma virus (HPV) sequences was analyzed using general and specific (types 16 and 18) primers.

RESULTS

General HPV sequences were demonstrated in all cases, but the oncogenic strain HPV 16 was present in only three (60%) of the five tumors; no HPV 18 was detected in any sample. Three of five TCCs, all harboring HPV 16 sequences, demonstrated concurrent allelic losses at several 3p loci (specifically 3p12, 3p14.2 [the FHIT gene locus], 3p21.3, and 3p22-24.2). LOH at a single locus on 9q32-qter was demonstrated in one tumor; no other deletions were seen on chromosome 9. P53 gene mutations in exons 5-8 were absent by SSCP analysis.

CONCLUSIONS

The infrequent involvement of chromosome 9 in TCCs of the cervix, along with the concurrent presence of 3p LOH and oncogenic HPV 16 in a subset of tumors, suggests a closer histogenetic relationship of this neoplasm to cervical SCCs rather than urothelial TCCs.

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.

Frequent aberration of the transforming growth factor-beta receptor II gene in cell lines but no apparent mutation in pre-invasive and invasive carcinomas of the uterine cervix

The type II transforming growth factor-beta (TGF-beta) receptor (RII) gene located at 3p22 plays an important role in regulating growth and differentiation of epithelium, including that of the uterine cervix. Loss-of-function mutations of RII have frequently been found in gastrointestinal cancers, with a replication-error (RER) phenotype characterized by the presence of microsatellite instability (MI). In this study, genomic PCR, SSCP and DNA sequencing were conducted to investigate the coding sequences of the RII gene in cell lines (n = 5) and tissues (n = 15) of squamous carcinomas of the uterine cervix. Intragenic deletions were noted in 2 of 5 cervical-cancer cell lines (ME180 and HeLa cells). However, no mutation, other than DNA polymorphisms, was found in 15 cervical cancers with either alleleic loss at 3p22 (n = 11) or MI (n = 4). Further analysis of squamous intraepithelial lesions (SIL) with (n = 12) or without (n = 4) MI for the (A)10 change, a prototypic mutation found in over 90% of RER-positive colon cancers, also showed no aberration. Our study concludes that the RII gene is frequently disrupted in cervical-cancer cell lines, but is rarely mutated in CC and SIL tissues, including those showing MI or alleleic loss at 3p22. The underlined mechanism of genomic instability in CC and SIL may thus differ from that of colorectal cancer. The allelic loss at 3p22-24 in CC does not involve the coding sequence of the RII gene. The non-coding sequence of RII or an unidentified gene may be responsible for it.

Monoclonality and surface lesion-specific microsatellite alterations in premalignant and malignant neoplasia of uterine cervix: a local field effect of genomic instability and clonal evolution

Invasive squamous carcinoma of the uterine cervix (CC) arises from sequential progression of low-grade (L) and high-grade (H) squamous intraepithelial lesions (SILs). In clinical observations, these lesions are frequently found as synchronous multiple foci. The nature and evolutionary mechanism of these lesions are largely unknown. We have performed allelotyping of three 3p markers (at 3p14, 3p22-24, and 3p25) on 22 LSILs and 15 HSILs microdissected from patients with multiple (n = 21) or uniform (n = 6) cervical lesions. The results were analyzed together with our previous allelotyping of 57 deeply invasive CCs. Loss of heterozygosity at one of the three markers was observed in 23%, 27%, and 31 % of LSILs, HSILs, and CCs, respectively. Frequent and early allelic loss was noted (in 30% of LSILs and 50% of HSILs) at 3p14, which may harbor tumor suppressor genes involved in early stages of cervical carcinogenesis. A high frequency of microsatellite alteration (MA) was found in LSIL (41%) and HSIL (67%) but not in CC (5.3%). In particular, MA was more frequently found in low-grade lesions in association with invasive cancers (75%, 6/8) than in those associated with SILs (29%, 4/14) (P < 0.05). Together with the finding of a monoclonal origin of premalignant and malignant cervical lesions, the present results allow us to propose a model of local field effect of genomic instability that progressively affects the clonal evolution of SIL of uterine cervix.