The presence of methylation of the p16INK4A gene and human papillomavirus in high-grade cervical squamous intraepithelial lesions

Associations of P16INK4a promoter hypermethylation with squamous intra-epithelial lesion, cervical cancer and their clinicopathological features: a meta-analysis

To assess the associations of P16INK4a methylation status with low-grade squamous intra-epithelial lesion (LSIL), high-grade squamous intra-epithelial lesion (HSIL), cervical cancer (CC) and their clinicopathological features, a meta-analysis with 29 eligible studies was conducted. Pooled odds ratios (ORs) with their 95% confidence intervals (CIs) were estimated to assess the strength of the associations. Heterogeneity, sensitivity of pooled results and publication bias were also evaluated. Overall, there was an increasing trend of P16INK4a hypermethylation rates among LSIL (21.4%), HSIL (30.9%) and CC (35.0%) specimens. P16INK4a hypermethylation was significantly associated with the increased risk of LSIL, HSIL and CC, with the pooled ORs of 3.26 (95% CI: 1.86-5.71), 5.80 (95% CI: 3.80-8.84) and 12.17 (95% CI: 5.86-25.27), respectively. A significant association was also found between P16INK4a hypermethylation and smoking habit (OR = 3.88, 95% CI: 2.13-7.08). Taken together, meta-analysis results support P16INK4a hypermethylation as an epigenetic marker for the progression of cervical carcinogenesis.

Down-regulation of p16 and MGMT promotes the anti-proliferative and pro-apoptotic effects of 5-Aza-dC and radiation on cervical cancer cells

Cervical cancer is one of the most common malignancies of the female reproductive system. Therefore, it is critical to investigate the molecular mechanisms involved in the development and progression of cervical cancer. In this study, we stimulated cervical cancer cells with 5-aza-2'-deoxycytidine (5-Aza-dC) and found that this treatment inhibited cell proliferation and induced apoptosis; additionally, methylation of p16 and O-6-methylguanine-DNA methyltransferase (MGMT) was reversed, although their expression was suppressed. 5-Aza-dC inhibited E6 and E7 expression and up-regulated p53, p21, and Rb expression. Cells transfected with siRNAs targeting p16 and MGMT as well as cells stimulated with 5-Aza-dC were arrested in S phase, and the expression of p53, p21, and Rb was up-regulated more significantly. However, when cells were stimulated with 5-Aza-dC after transfection with siRNAs targeting p16 and MGMT, proliferation decreased significantly, and the percentage of cells in the sub-G1 peak and in S phase was significantly increased, suggesting a marked increase in apoptosis. But E6 and E7 overexpression could rescue the observed effects in proliferation. Furthermore, X-ray radiation caused cells to arrest in G2/M phase, but cells transfected with p16- and MGMT-targeted siRNAs followed by X-ray radiation exhibited a significant decrease in proliferation and were shifted toward the sub-G1 peak, also indicating enhanced apoptosis. In addition, the effects of 5-Aza-dC and X-ray radiation were most pronounced when MGMT expression was down-regulated. Therefore, down-regulation of p16 and MGMT expression enhances the anti-proliferative effects of 5-Aza-dC and X-ray radiation. This discovery may provide novel ideas for the treatment of cervical cancer.

Novel epigenetic changes in CDKN2A are associated with progression of cervical intraepithelial neoplasia

OBJECTIVE

To conduct a comprehensive mapping of the genomic DNA methylation in CDKN2A, which codes for the p16(INK4A) and p14(ARF) proteins, and 14 of the most promising DNA methylation marker candidates previously reported to be associated with progression of low-grade cervical intraepithelial neoplasia (CIN1) to cervical cancer.

METHODS

We analyzed DNA methylation in 68 HIV-seropositive and negative women with incident CIN1, CIN2, CIN3 and invasive cervical cancer, assaying 120 CpG dinucleotide sites spanning APC, CDH1, CDH13, CDKN2A, CDKN2B, DAPK1, FHIT, GSTP1, HIC1, MGMT, MLH1, RARB, RASSF1, TERT and TIMP3 using the Illumina Infinium array. Validation was performed using high resolution mapping of the target genes with HELP-tagging for 286 CpGs, followed by fine mapping of candidate genes with targeted bisulfite sequencing. We assessed for statistical differences in DNA methylation levels for each CpG loci assayed using univariate and multivariate methods correcting for multiple comparisons.

RESULTS

In our discovery sample set, we identified dose dependent differences in DNA methylation with grade of disease in CDKN2A, APC, MGMT, MLH1 and HIC1, whereas single CpG locus differences between CIN2/3 and cancer groups were seen for CDH13, DAPK1 and TERT. Only those CpGs in the gene body of CDKN2A showed a monotonic increase in methylation between persistent CIN1, CIN2, CIN3 and cancers.

CONCLUSION

Our data suggests a novel link between early cervical disease progression and DNA methylation in a region downstream of the CDKN2A transcription start site that may lead to increased p16(INK4A)/p14(ARF) expression prior to development of malignant disease.

The association of HPV genotype with the regression, persistence or progression of low-grade squamous intraepithelial lesions

BACKGROUND

Human papillomavirus (HPV) is a highly prevalent sexually transmitted virus causing cytological alterations that precede cervical cancer. Approximately 130 genotypes have been sequenced. Low-grade squamous intraepithelial lesions (LSIL) are the most frequent cytological alteration and have an uncertain behavior.

OBJECTIVES

To analyze the frequency of HPV types in LSIL and their association with the regression, persistence or progression of these lesions.

METHODS

A cohort study of forty patients with LSIL cytology was conducted from December 2007 to March 2011. The follow-up lasted two years and included cytology and colposcopy. HPV detection was performed using PCR, and genotyping was performed using PCR-specific and RFLP techniques.

RESULTS

DNA-HPV was detected in 87% (35/40) of the cases, with oncogenic HPV accounting for 76%; type 16 in 32% (11/35) and type 18 in 20%. LSIL regression, persistence and progression rates at the end of the study were 60%, 23% and 17%, respectively. There was 50% regression in lesions in the high oncogenic risk group (types 16 and 18).

CONCLUSION

HPV 16 was the most frequent genotype found in LSIL. The persistence and progression of the LSIL were related to the persistence of oncogenic HPV. The longer the follow-up time, the lower the LSIL persistence rate and the higher its regression rate; the progression rate remained stable. In addition to the presence of oncogenic HPV, other factors are necessary for the progression of LSIL.

HPV infection and p16 promoter methylation as predictors of ASC-US/LSIL progression

BACKGROUND

Although patients found to have atypical squamous cells of undetermined significance (ASC-US) and low-grade squamous intraepithelial lesions (LSILs) on Papanicolaou (Pap) testing are treated conservatively, 5.2% to 18.8% of them progress to high-grade squamous intraepithelial lesions (HSILs). The objective of the current study was to identify predictors of progression to HSIL and determine what percentage of ASC-US/LSIL cases harbor cervical intraepithelial neoplasia of grade 2 or higher.

METHODS

The current study included 381 consecutive cases with ASC-US/LSIL. After the exclusion of 87 cases because of a history of dysplasia or loss to follow-up, 165 cases with follow-up cytology were used to analyze predictive factors of progression to HSIL, and 129 cases that underwent immediate tissue biopsy were subjected to correlation analysis between cytology and histology. Disease regression was defined as a reversion to normal or benign cellular changes, disease persistence as maintenance at ASC-US/LSIL, and disease progression as progression to HSIL. Data regarding clinical parameters were obtained from medical records. Methylation-specific polymerase chain reaction was performed using cytology samples to evaluate methylation of the p16 promoter.

RESULTS

Of 165 cases, 131 (79.4%) regressed, 23 (13.9%) were persistent, and 11 cases (6.7%) progressed. Human papillomavirus infection was more common in women with disease progression than in those with disease regression or persistence (P = .033). Promoter methylation of p16 in the cytology sample was more common in cases that progressed (5 of 6 cases) than in cases that regressed (0 of 8 cases). Twenty-three of 129 cases (17.8%) were found to harbor cervical intraepithelial neoplasia of grade 2 or higher on immediate tissue biopsy.

CONCLUSIONS

Human papillomavirus infection and p16 promoter methylation might be valuable surrogate markers of disease progression from ASC-US/LSIL to HSIL.

HPV DNA genotyping and methylation of gene p16 INK4A in cervical LSIL

BACKGROUND

DNA methylation is the most important epigenetic change involved in the control of gene expression in human cells. Methylation of the p16(INK4a) gene occurs early in the development of cervical cancer. Low-grade squamous intraepithelial lesions (LSILs) are prevalent, and their behavior is variable.

OBJECTIVE

To identify the HPV DNA type, detect the methylation status of the p16(INK4A) gene, and analyze their association with the cytological evolution of LSIL over a period of two years.

METHODS

We conducted a cohort study with 40 participants. Cervical scrapings were collected for cytological and molecular analysis. HPV DNA detection and typing were performed by means of polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP). Methylation-specific PCR was performed to detect methylation.

RESULTS

HPV DNA was detected in 87% of the cases, and type 16 was the most frequent type. Methylation was detected in 11% of the cases and did not exhibit a significant correlation with the HPV type. Unfavorable cytological evolution exhibited a significant association with the presence of methylation.

CONCLUSION

HPV 16 was the most frequently detected type of HPV in LSIL. Methylation of the p16(INK4A) gene was infrequent and occurred independent of the presence of HPV DNA. Methylation of the p16(INK4a) gene exhibited a significant correlation with persistence/progression of LSIL.

TIMP-2 gene methylation in cervical precursor and invasive lesions

OBJECTIVE

To analyze the presence of HPV-DNA and TIMP-2 gene methylation in cervical precursor and invasive lesions, as well as to study the associations among the latter, the presence of HPV-DNA, and the clinical evolution of such lesions.

METHODS

Cross-sectional study that includes 49 biopsy or brush smear samples from women with a normal cervix, LSIL, HSIL, microinvasive carcinoma and invasive carcinoma. The presence of HPV-DNA and specific methylation was analyzed using PCR. Thirty-eight biopsy samples for HSIL, microinvasive carcinoma and frank invasive carcinoma as well as 11 brush smear samples for LSIL and normal cervices were analyzed.

RESULTS

TIMP-2 gene methylation was detected in 86.8% (33/38) of the samples from the group with lesions and 50% (4/8) of the normal samples (p=0.03). HPV-DNA was detected in 81.6% (31/38) of the samples from the group with lesions and 25% (2/8) of the normal samples (p=0.003). HPV-DNA was more frequent in the methylated samples (50%), and the group with methylation had a higher risk of unfavorable evolution than the group without methylation; however, such observations were not statistically significant (p=0.19).

CONCLUSION

TIMP-2 gene methylation and the presence of HPV-DNA were characteristic of the group with cervical lesions. Methylation was not associated with the presence of HPV-DNA or an unfavorable clinical evolution.

Patterns of cellular and HPV 16 methylation as biomarkers for cervical neoplasia

Aberrant promoter methylation of biologically relevant genes in cervical cancer and uneven CpG distribution within the human papillomavirus 16 (HPV 16) enhancer region have been reported. Cervical samples and questionnaires from 151 women screened for cervical cancer in Appalachian Ohio were analyzed. Methylation was measured by bisulfite sequencing in candidate gene sites in ESR1, DCC, p16, and LINE1 elements. Among 89 HPV 16-positive women, CpG sites in the E6 promoter and enhancer regions and the L1 region of the HPV 16 genome were measured. Methylation levels were compared by cervical cytology and HPV 16 status. HPV methylation was low regardless of cytology status, however E6 methylation was significantly higher in women with normal cytology. ESR1 and DCC methylation were significantly higher in HPV 16-positive women. Increased methylation at sites in the E6 promoter region was associated with lower odds of abnormal cytology. Increased methylation in candidate genes was associated with higher odds of abnormal cytology, particularly DCC region 2.4, DCC region 2.6, ESR1 region 3.2, and LINE1 site 1.2. HPV 16 genome CpG methylation was low except for the L1 region. In general, lower HPV 16 methylation and higher candidate gene methylation levels were associated with higher odds of abnormal cytology.

Prediction of clinical outcome using p16INK4a immunocytochemical expression in low-grade squamous intraepithelial lesions and high-risk HPV-positive atypical squamous cells of undetermined significance in patients with and without colposcopic evident cervical disease

p16INK4a as a diagnostic marker of a cervical intraepithelial neoplasia of grade 2+ (CIN2+) in atypical squamous cells of undetermined significance (ASC-US) and low-grade squamous intraepithelial lesion (LSIL) cytological samples has been analyzed, but has not yet been included in clinical routine practice. One hundred and ninety-one patients with an abnormal Pap test (84 ASC-US and 107 LSILs) who underwent colposcopy were selected for this study. At enrollment, 96 patients (Group 1) had a positive colposcopy and therefore underwent a cervical biopsy, while 95 (Group 2) had a negative colposcopy and were followed up for up to 1 year. Both groups were tested for p16INK4a using immunocytochemical methods, and the p16INK4a results were correlated with histology or follow-up outcome. In Group 1 ASC-US cases, 82% of lesions less than CIN2 were p16INK4a-negative and all CIN2 cases were p16INK4a-positive (p=0.00044). In Group 1 LSIL cases, 71% of lesions less than CIN2 were p16INK4a-negative and 87% of CIN2/3 were p16INK4a-positive (p=0.00033). Seventy-seven percent of Group 2 ASC-US patients with a negative 1-year follow-up (NF-U) were p16INK4a-negative at enrollment, while all patients with positive follow-up (PF-U) were p16INK4a-positive (p=0.00113). In Group 2 LSIL cases, 83% of patients with NF-U were p16INK4a-negative, while 65% of patients with PF-U were p16INK4a-positive at enrollment (p=0.0014). In fact, 39% of the positive p16INK4a LSIL patients had CIN2+ histological lesions. The positive predictive value of p16INK4a for CIN2+ was 50% in ASC-US and 52% in LSIL cases; the negative predictive value was 100 and 94%, respectively. In conclusion, in our patients, a negative p16INK4a appears to be a marker of the absence of CIN3, while a positive p16INK4a can be correlated with the presence of histological CIN2+ found at enrollment or during the subsequent follow-up. Thus, its clinical predictive value is independent from the colposcopic aspect at enrollment.