Loss of heterozygosity on chromosome 6 in HPV-16 positive cervical carcinomas carrying the DRB1*1501-DQB1*0602 haplotype

CDYL loss promotes cervical cancer aggression by increasing PD-L1 expression via the suppression of IRF2BP2 transcription

BACKGROUND

Recurrent or metastatic cervical cancer have an extremely low 5-year survival rates about 17% due to limited therapeutic options. CDYL plays a critical role in multiple cancer development, as an oncogene or tumor suppressor in a context-dependent manner. However, the role of CDYL in cervical carcinogenesis has not yet been explored.

METHODS

CDYL expression was examined in cervical cancer and cell lines. The effect of CDYL/IRF2BP2/PD-L1 axis on malignant phenotypes of cervical cancer cells were tested with gain-of-function experiments. A mouse model of cervical cancer was developed to validate the in vitro results.

RESULTS

Clinical data analysis revealed that CDYL was downregulated and associated with a poor prognosis in cervical cancer patients. CDYL overexpression suppressed cervical cancer cells proliferation and invasion in vitro and vivo assays and enhanced the immune response by decreasing PD-L1 expression and reversing the tumor immunosuppressing microenvironment. Mechanistically, CDYL inhibited the PD-L1 expression through transcriptionally suppressing IRF2BP2 in cervical cancer cells.

CONCLUSIONS

Taken together, our findings established the crucial role of CDYL in cervical carcinogenesis and sensitivity for immune checkpoint blockade therapy, and supported the hypothesis that CDYL could be a potential novel immunotherapy response predictive biomarker for cervical cancer patients.

Allelic loss of HLA class I facilitates evasion from immune surveillance in cervical intraepithelial neoplasia

Loss of heterozygosity (LOH) has been reported to occur in HLA regions in cervical intraepithelial neoplasia (CIN) and cervical cancer. However, the details of how this is related to the progression of CIN have been unclear. In this study, we examined the human papillomavirus (HPV) antigen-presenting capacity of people with CIN and the significance of LOH of HLA class I in the progression of CIN. It was shown that differences in antigen-presenting capacity among each case depended on HLA types, not HPV genotypes. Focusing on the HLA type, there was a positive correlation between antigen-presenting capacity against HPV and the frequency of allelic loss. Furthermore, the lost HLA-B alleles had a higher HPV antigen-presenting capacity than intact alleles. In addition, frequency of LOH of HLA class I was significantly higher in advanced CIN (CIN2-3) than in cervicitis or early-stage CIN (CIN1): around half of CIN2-3 had LOH of any HLA class I. Moreover, the antigen-presenting capacity against E5, which is the HPV proteins that facilitate viral escape from this immune surveillance by suppressing HLA class I expression, had the most significant impact on the LOH in HLA-B. This study suggests that HPV evades immune surveillance mechanisms when host cells lose the capacity for antigen presentation by HLA class I molecules, resulting in long-term infection and progression to advanced lesions.

Cervical cancer risk profiling: molecular biomarkers predicting the outcome of hrHPV infection

INTRODUCTION

Cervical cancer affects half a million women worldwide annually. Given the association between high-risk human papillomavirus (hrHPV) infection and carcinogenesis, hrHPV DNA testing became an essential diagnostic tool. However, hrHPV alone does not cause the disease, and, most importantly, many cervical lesions regress to normal in a year because of the host immune system. Hence, the low specificity of hrHPV DNA tests and their inability to predict the outcome of infections have triggered a further search for biomarkers.

AREAS COVERED

We evaluated the latest viral and cellular biomarkers validated for clinical use as primary screening or triage for cervical cancer and assessed their promise for prevention as well as potential use in the future. The literature search focused on effective biomarkers for different stages of the disease, aiming to determine their significance in predicting the outcome of hrHPV infections.

EXPERT OPINION

Biomarkers such as p16/Ki-67, hrHPV genotyping, hrHPV transcriptional status, and methylation patterns have demonstrated promising results. Their eventual implementation in the screening programs may support the prompt diagnosis of hrHPV infection and its progression to cancer. These biomarkers will help in making clinical management decisions on time, thus, saving the lives of hrHPV-infected women, particularly in developing countries.

Investigation of Cervical Tumor Biopsies for Chromosomal Loss of Heterozygosity (LOH) and Microsatellite Instability (MSI) at the HLA II Locus in HIV-1/HPV Co-infected Women

Background: A subgroup of women who are co-infected with human immunodeficiency virus type 1 (HIV-1) and human papillomavirus (HPV) progress rapidly to cervical disease regardless of high CD4 counts. Chromosomal loss of heterozygosity (LOH) and microsatellite instability (MSI) are early frequent genetic alterations occurring in solid tumors. Loss of an allele or part of a chromosome can have multiple functional effects on immune response genes, oncogenes, DNA damage-repair genes, and tumor-suppressor genes. To characterize the genetic alterations that may influence rapid tumor progression in some HIV-1-positive women, the extent of LOH and MSI at the HLA II locus on chromosome 6p in cervical tumor biopsy DNA samples with regard to HIV-1/HPV co-infection in South African women was investigated.

Methods: A total of 164 women with cervical disease were recruited for this study, of which 74 were HIV-1-positive and 90 were HIV-1-seronegative. DNA from cervical tumors and matched buccal swabs were used for analyses. Six fluorescently-labeled oligonucleotide primer pairs in a multiplex PCR amplification were used to study LOH and MSI. Pearson chi-squared test for homogeneity of proportions using an exact p value, a two-proportion Z-score test, ROC curves and a logistic regression model were used for statistical analyses. All p-values were corrected for false discovery rate (FDR) using the Benjamini-Hochberg test and the adjusted p-values (q-values) were reported. All tests were significant when both p and q < 0.05.

Results: Tumor DNA from HIV-1/HPV co-infected women demonstrated a higher frequency of LOH/MSI at the HLA II locus on chromosome 6p21.21 than tumor DNA from HIV-1-seronegative women (D6S2447, 74.2 vs. 42.6%; p = 0.001, q = 0.003), D6S2881 at 6p21.31 (78.3 vs. 42.9%; p = 0.002, q = 0.004), D6S2666 at 6p21.32 (79 vs. 57.1%; p = 0.035, q = 0.052), and D6S2746, at 6p21.33 (64.3 vs. 29.4%; p < 0.001, q < 0.001), respectively.

Conclusions: HPV infection alone can induce LOH/MSI at the HLA II locus in cervical tumor DNA, whereas HIV-1 co-infection exacerbates it, suggesting that this may accelerate cervical disease progression in a subgroup of HIV-1-positive women.

Genetic predictors of cervical dysplasia in African American HIV-infected women: ACTG DACS 268

OBJECTIVE

To examine genome-wide associations in HIV-infected women with a history of cervical dysplasia compared with HIV-infected women with no history of abnormal Papanicolaou (Pap) tests.

DESIGN

Case-control study using data from women analyzed for the HIV Controllers Study and enrolled in HIV treatment-naïve studies in the AIDS Clinical Trials Group (ACTG).

METHODS

Genotyping utilized Illumina HumanHap 650 Y or 1MDuo platforms. After quality control and principal component analysis, ~610,000 significant single nucleotide polymorphisms (SNPs) were tested for association. Threshold for significance was P < 5 × 10(-8) for genome-wide associations.

RESULTS

No significant genomic association was observed between women with low-grade dysplasia and controls. The genome-wide association study (GWAS) analysis between women with high-grade dysplasia or invasive cervical cancer and normal controls identified significant SNPs. In the analyses limited to African American women, 11 SNPs were significantly associated with the development of high-grade dysplasia or cancer after correcting for multiple comparisons. The model using significant SNPs alone had improved accuracy in predicting high-grade dysplasia in African American women compared to the use of clinical data (area under the receiver operating characteristic curve for genetic and clinical model = 0.9 and 0.747, respectively).

CONCLUSIONS

These preliminary data serve as proof of concept that there may be a genetic predisposition to developing high-grade cervical dysplasia in African American HIV-infected women. Given the small sample size, the results need to be validated in a separate cohort.

Genetic variants in HLA-DP/DQ contribute to risk of cervical cancer: a two-stage study in Chinese women

OBJECTIVE

Human leukocyte antigens (HLA) play an important role in presenting virus antigens to immune cells that are responsible for the clearance of virus-infected cells and tumor cells. Herein, we evaluated whether genetic variants of HLA-DP and HLA-DQ are associated with cervical cancer risk.

METHODS

We genotyped four single nucleotide polymorphisms (SNPs) in HLA-DP (rs3077 and rs9277535) and HLA-DQ (rs2856718 and rs7453920) in a two-stage case-control study with a total of 2317 cervical cancer cases and 2109 cancer-free controls using TaqMan allelic discrimination assay.

RESULTS

We found consistently significant associations of HLA-DP rs3077 and rs9277535 with increased risks of cervical cancer (dominant genetic model: adjusted OR=1.51, 95% CI=1.32-1.71 for rs3077; adjusted OR=1.29, 95% CI=1.12-1.49 for rs9277535). When combining the effects of HLA-DP rs3077 and rs9277535, subjects carrying "≥1" variant alleles had a 1.55-fold increased risk of cervical cancer (95% CI=1.32-1.81), compared with those carrying "0" variant allele. And cervical cancer risk significantly increased with the increasing number of variant alleles of the two SNPs in a dose-dependent manner (P for trend=4.33×10(-10)). However, there were no significant associations for HLA-DQ rs2856718 and rs7453920 in our population.

CONCLUSIONS

These findings indicate that HLA-DP rs3077 and rs9277535 were candidate susceptibility markers for cervical cancer in Chinese females. Further validation studies with different ethnic background, biological function analyses and especially HPV typing together were needed.

HLA-DRB1*1501 and HLA-DQB1*0301 alleles are positively associated with HPV16 infection-related Kazakh esophageal squamous cell carcinoma in Xinjiang China

Multiple determinant factors are involved in the occurrence and progression of esophageal squamous cell carcinoma (ESCC). Human papillomavirus (HPV) and human leukocyte antigen (HLA) polymorphism were identified as important factors. This study examined the associations between the development of Kazakh ESCC and the determinant factors including HLA-DRB1*0901, 1501; DQB1*0301, 0602; high-risk HPV infection in the area of Xinjiang, China. 200 Kazakh patients with ESCC and 150 controls were recruited, and polymerase chain reaction (PCR) was performed to detect HLA-DRB1*0901, 1501 and DQB1*0301,0602 using sequence-specific primers (SSPs). HPV16 was detected in esophageal specimens using PCR. HPV16 infection rate in Kazakh ESCC case group was 41 %, significantly higher than that of control group 14 % (OR = 3.62; 95 % CI, 2.15-6.09; P < 0.001). A positive association between ESCC and HLA-DRB1*1501 (OR = 2.46, P < 0.0125) or HLA-DQB1*0301 (OR = 3.34, P < 0.0125) alleles was observed. Similar tendencies were observed for HLA-DRB1*1501 (OR = 3.095, P < 0.0125) and HLA-DQB1*0301 (OR = 2.410, P < 0.0125) alleles with HPV16-positive ESCC. HLA-DRB1*1501, HLA-DQB1*0301 and DQB1*0602 were significantly associated with ESCC when the age was ≥55 years (P < 0.0125 for all), whereas only HLA-DQB1*0301 was significantly associated with ESCC when the age was <55 years (P < 0.0125). HLA-DRB1*1501 and HLA-DQB1*0301 were significantly associated with an increase in ESCC occurrence in females (P < 0.0125), whereas only HLA-DQB1*0301 was significantly associated with ESCC in males. Moreover, the occurrence of HLA-DQB1*0602 gene in poorly differentiated ESCC group (68.8 %) was slightly higher than that of well-differentiated squamous cell carcinoma group (31.2 %). The difference was not statistically significant (P > 0.0125). The study suggests that HLA-DRB1*1501 and HLA-DQB1*0301 may influence the immune response to specific tumor and HPV-encoded epitopes and affect the risk of Kazakh ESCC in XinJiang, China.

Risks for persistence and progression by human papillomavirus type 16 variant lineages among a population-based sample of Danish women

BACKGROUND

Little is known about factors determining HPV16 persistence and progression, but several studies have suggested that genetic variants may play a role.

METHODS

HPV16-positive women with normal cytology in a large Danish cohort were reassessed for HPV16 status at 2 years and followed-up for cervical intraepithelial neoplasia 3 or worse (CIN3+) over 11 years through linkage with a national pathology database. Relative risks for clearance, persistence, and progression were compared with different HPV16 variant lineages based upon E6 gene sequencing.

RESULTS

Sixty-two (23.7%) of 261 HPV16 infections were persistent at 2 years, and 32 (51.6%) persistent infections progressed to CIN3+. The majority of baseline infections belonged to the European lineage (97.3%), with EUR-350T and EUR-350G accounting for 61.3% and 36.0% of infections, respectively. At two years, the proportion of HPV16 infections that persisted was significantly higher for EUR-350T (28.2%) than EUR-350G (15.9%) variants (odds ratio = 2.06, 95% CI, 1.04-4.25). This increased risk for persistence was consistent both in the absence (OR = 2.16, 95% CI, 0.84-6.26) or presence (OR = 1.89, 95% CI, 0.76-5.15) of progression to CIN3+. Among persistent HPV16 infections, there was no significant difference in risk of progression to CIN3+ between EUR-350T and EUR-350G sub-lineages, which were both associated with a substantial absolute risk (>50%) of CIN3+.

CONCLUSIONS

Significant differences in risk for persistence exist between the HPV16 variants that predominate in Europe.

IMPACT

Understanding the genetic basis of HPV16 persistence and carcinogenicity may help unravel important interactions between HPV16 and the host immune system.

Mitochondrial C150T polymorphism increases the risk of cervical cancer and HPV infection

During a survey of control region (D-loop) sequence variances in 142 cervical cancer (CC) patients and 136 controls, all Chinese women, including both HPV-positive (human papillomavirus) and HPV-negative subjects, we determined that the C150T polymorphism increased the CC risk in a case-control study (OR=3.0, 95% CI=1.8-5.0, P<0.05). HPV-positive individuals were more likely to carry the C150T polymorphism than HPV-negative controls (OR=5.8, 95% CI=2.6-13.2, P=2.3×10(-5)). HPV-positive CC patients were more likely to carry the C150T polymorphism than HPV-negative controls (OR=4.9, 95% CI=2.6-9.3, P=9.9×10(-7)). In all subjects, an increased risk of HPV infection was also associated with the C150T polymorphism (OR=4.5, 95% CI=2.5-8.1, P=6.6×10(-7)). However, no significant difference in the frequency of other alleles was found at the variable sites in D146, D152, D310 and D514. These results indicated that the C150T polymorphism increased the risk of HPV infection and CC progression. Additionally, we assessed the association of mtDNA copy number with CC risk or the C150T polymorphism in 45 CC patients and 43 controls. There was no significant association of mtDNA copy number with CC risk or the C150T polymorphism. To the best of our knowledge, this is the first report to suggest that mtDNA C150T polymorphism was positively associated with HPV infection and subsequent CC risk among Chinese women.

HPV variants and HLA polymorphisms: the role of variability on the risk of cervical cancer

Human papillomavirus (HPV) infection is linked to the development of cervical cancer, and several cofactors contribute to the risk of disease. Research on the intratypic variability of HPVs has defined variants that are associated with persistent infections and are potentially more oncogenic, translating to a higher risk of malignant disease. The genetic variability of the host also plays a role in the risk of cervical cancer, especially genes controlling the immune response, such as HLA class I and II. These highly polymorphic genes are important risk determinants of HPV persistence and disease progression. The interaction between host and viral factors is complex and needs to be further investigated, paving the way to better define the patients at the highest risk of developing malignant diseases linked to HPV infection.

CDYL bridges REST and histone methyltransferases for gene repression and suppression of cellular transformation

The neuronal gene repressor REST/NRSF recruits corepressors, including CoREST, to modify histones and repress transcription. REST also functions as a tumor suppressor, but the mechanism remains unclear. We identified chromodomain on Y-like (CDYL) as a REST corepressor that physically bridges REST and the histone methylase G9a to repress transcription. Importantly, RNAi knockdown of REST, CDYL, and G9a, but not CoREST, induced oncogenic transformation of immortalized primary human cells and derepression of the proto-oncogene TrkC. Significantly, transgenic expression of TrkC also induced transformation. This implicates CDYL-G9a, but not CoREST, in REST suppression of transformation, possibly by oncogene repression. CDYL knockdown also augments transformation in a cell culture model of cervical cancer, where loss of heterozygosity of the CDYL locus occurs. These findings demonstrate molecular strategies by which REST carries out distinct biological functions via different corepressors and provide critical insights into the role of histone-modifying complexes in regulating cellular transformation.

Some but not all of HLA-II alleles are associated with cervical cancer in Chinese women

Cervical cancer (CC) is closely associated with the human papillomavirus (HPV). Although most patients are able to clear the infection over time, some eventually develop cancer, suggesting the existence of other factors that determine malignant progression. Such factors may include genetic susceptibility. To determine whether human leukocyte antigen (HLA) class II is related to CC among Han race population in the Guangdong region of China, HLA class II typing were carried out by polymerase chain reaction in 126 patients with CC and 88 selected controls. The allele and haplotype frequencies in both the study and control groups were calculated. The occurrence of DPB1 *1301 [odds ratio (OR), 2.66; 95% confidence interval (CI), 1.12-6.29], DPB1 *0202 (OR, 3.65; CI, 1.04-12.80), DQB1 *030302(OR, 1.85; CI, 1.04-3.27), and DQB1 *050301(OR, 3.94; CI, 1.48-10.46) alleles were more common in the study group than control. This suggests that these alleles may confer susceptibility to CC in the Guangdong Province. In a similar fashion, the occurrence of DRB1 *13-DQB1 *06 (OR, 0.17; 95% CI, 0.04-0.80) haplotype was significantly lower in the study patients compared with the controls and may confer a decreased risk of CC among Han race population in the Guangdong Province of China.

Isolation and functional analysis of five HPVE6 variants with respect to p53 degradation

Persistent infection with high risk human papillomavirus is a necessary risk factor in the etiology of invasive cervical carcinoma. With regard to molecular details, the best studied types are HPV16 and HPV18 which are found in 70% of cervical cancer worldwide, however factors associated with the progression of individual cervical intraepithelial neoplasias into cancer are still poorly understood. Intratype amino acid variations in the immortalizing and transforming early proteins E6 and E7 were described to be associated with progressive disease and linked to increased viral persistence or progression. One of the key actions of high risk HPVE6 proteins is the inhibition of the function of p53, a tumor suppressor protein, by enhancing its degradation through the ubiquitin pathway. In this study, variants of five HPV type E6 proteins (HPV35, 53, 56, 66, and 70) isolated from patient materials are described and functional analysis of them were done with respect to p53 degradation. Interestingly the E6 protein of HPV type 53, which has no consistent risk classification in the literature showed the highest variability in our study. The analysis of all variants revealed no differences with regard to the degradation ability for p53 compared to the prototype E6 proteins, suggesting that the variants tested revealed no altered functions related to the carcinogenicity of the respective HPV types. It therefore seems more likely that variations in the E6 gene sequence may allow evasion from the hosts immune system, supporting increased viral persistence.

Immune concept of human papillomaviruses and related antigens in local cancer milieu of human cervical neoplasia

It is presently the right time for clarifying human papillomavirus (HPV)-associated cellular immunity and clinical implications before global HPV vaccination programs begin. Infection with oncogenic HPV associates with the progression of cervical neoplasia. Both cellular and humoral immune responses are essential for the clearance of HPV-associated cervical lesions. There is increasing evidence that the immune system plays a pivotal role in determining the outcome of HPV infection. Viruses and associated neoplastic cells are proposed to have evolved mechanisms to avoid immune attack. T-cell-mediated immune responses against oncogenic HPV are believed to play a central role in cervical carcinogenesis. The presence of HPV-specific cytotoxic T lymphocytes (CTL) in a majority of human cervical cancer patients provides an approach for further study of their functional role in modulating this malignancy. Tumor-infiltrating lymphocytes (TIL) develop as manifestations of the recognition and defense against malignant cells by the host immune system. Cancer cells may overcome immune surveillance, either by downregulating the proliferation of HPV-specific CTL, or altering the effector compositions of immune cells against HPV infections. TIL in the tumor microenvironment can be functionally inhibited and lose the ability of clonal proliferation as a result of depressed expression of IL-2Ralpha. The upregulation of inhibitory signaling relates to the modulation of the virus- and/or tumor-specific immune responses. Alteration of host genetic susceptibility may also lead to abnormal immune response as a general genomic instability resulting from virus persistence. Induction of HPV-specific immune responses is anticipated as an intimate point for the treatment of cervical neoplasia.

Increased risk for cervical disease progression of French women infected with the human papillomavirus type 16 E6-350G variant

To test the significance of human papillomavirus (HPV) type 16 and HPV16 E6 variants as risk factors for viral persistence and progression to high-grade lesion, we did a nested case-control study within a cohort study of >15,000 Caucasian French women. Three groups infected with high-risk HPV were compared: (a) women with cleared infection (controls, n = 201), (b) women with persistent infection (cases, n = 87), and (c) women who progressed into high-grade lesion (cases, n = 58). Women with persistent HPV infection and those that progressed into high-grade lesions were likelier to harbor HPV16 than other high-risk HPV types [odds ratio (OR), 2.4; 95% confidence interval (95% CI), 1.3-4.3 and OR, 4.2; 95% CI, 2.2-8.1, respectively]. Notably, especially elevated ORs of persistence (3.0; 95% CI, 1.4-6.7) and progression (6.2; 95% CI, 2.7-14.3) were found among women who harbored the HPV16 350G variant. Thus, HPV type and HPV16 variant seem to be risk factors for viral persistence and progression of infections into high-grade cervical lesions.

Human leukocyte antigen class II alleles and risk of cervical cancer in China

Human leukocyte antigen (HLA) class II alleles have been associated with an increased or decreased risk of developing cervical cancer through infection with oncogenic forms of human papillomavirus (HPV). To verify whether HLA class II allelic polymorphism is related to cervical cancer in China, 133 cervical cancers and 98 healthy controls were analyzed for HLA typing. Our results showed that DPB1*1301 allele frequency was significantly higher in the cervical cancers compared with healthy controls (OR, 3.793; p = 0.002; Pc = 0.04). A significant relationship was found between DRB1*150101-DQB1*0602 haplotype (OR, 0.180; p < 0.0001; Pc < 0.003), DRB1*070101-DQB1*0201 haplotype (OR, 0.110; p = 0.001; Pc = 0.03), and decreased risk for cervical cancer. Similar tendencies were observed for DRB1*150101-DQB1*0602 haplotype with HPV16 positive cervical cancers (OR, 0.182; p = 0.001; Pc = 0.021), and for DRB1*070101-DQB1*0201 haplotype (OR, 0.144; p =0.003; Pc = 0.063). These results indicate that HLA-DPB1*1301 may confer susceptibility to cervical cancer, and the haplotypes DRB1*150101-DQB1*0602 and DRB1*070101-DQB1*0201 may contribute to the resistance to the development of cervical cancer among Chinese women. The study suggests that specific HLA class II alleles and haplotypes may influence the immune response to specific HPV-encoded epitopes and affect the risk of cervical cancer in a Chinese population from an area with a high incidence of this neoplasia.

Human papillomavirus type 16 integration in cervical carcinoma in situ and in invasive cervical cancer

Integration of human papillomavirus type 16 (HPV-16) into the host DNA has been proposed as a potential marker of cervical neoplastic progression. In this study, a quantitative real-time PCR (qRT-PCR) was used to examine the physical status of HPV-16 in 126 cervical carcinoma in situ and 92 invasive cervical cancers. Based on criteria applied to results from this qRT-PCR assay, HPV-16 was characterized in carcinoma in situ cases as episomal (61.9%), mixed (i.e., episomal and integrated; 29.4%), and integrated (8.7%) forms. In invasive cervical cancer samples, HPV-16 was similarly characterized as episomal (39.1%), mixed (45.7%), and integrated (15.2%) forms. The difference in the frequency of integrated or episomal status estimated for carcinoma in situ and invasive cervical cancer cases was statistically significant (P = 0.003). Extensive mapping analysis of HPV-16 E1 and E2 genes in 37 selected tumors demonstrated deletions in both E1 and E2 genes with the maximum number of losses (78.4%) observed within the HPV-16 E2 hinge region. Specifically, deletions within the E2 hinge region were detected most often between nucleotides (nt) 3243 and 3539. The capacity to detect low-frequency HPV-16 integration events was highly limited due to the common presence and abundance of HPV episomal forms. HPV-16 E2 expressed from intact episomes may act in trans to regulate integrated genome expression of E6 and E7.

HPV-mediated cervical carcinogenesis: concepts and clinical implications

Persistent infection with a high-risk human papillomavirus (hrHPV) is generally accepted as a necessary cause of cervical cancer. However, cervical cancer is a rare complication of an hrHPV infection since most such infections are transient, not even giving rise to cervical lesions. On average, it takes 12-15 years before a persistent hrHPV infection may ultimately, via consecutive premalignant stages (ie CIN lesions), lead to an overt cervical carcinoma. This argues that HPV-induced cervical carcinogenesis is multi-step in nature. In this review, the data from hrHPV-mediated in vitro transformation studies and those obtained from analysis of clinical specimens have been merged into a cervical cancer progression model. According to this model, a crucial decision maker in the early stages following infection involves individual susceptibility for certain HPV types depending on the genetic make-up of immune surveillance determinants. Once a CIN lesion has developed, altered transcriptional regulation of the viral E6/E7 oncogenes, resulting in genomic instability and distinguishing the process of cell transformation from a productive viral infection, probably provides the subsequent important step towards malignancy. The additional (epi)genetic alterations that subsequently accumulate in high-grade CIN lesions may result in overt malignancy via immortality and growth conditions that gradually become less sensitive to growth-modulating influences mediated by cytokines and cell-cell and cell-matrix adhesions. The potential implications of hrHPV testing and some other biomarkers deduced from this model for cervical screening and the clinical management of CIN disease are also discussed.

Frequent HLA class I loss is an early event in cervical carcinogenesis

Loss at chromosome 6p21.3, the human leukocyte antigen (HLA) region, is the main cause of HLA downregulation, occurring in the majority of invasive cervical carcinomas. To identify the stage of tumor development at which HLA class I aberrations occur, we selected 12 patients with cervical carcinoma and adjacent cervical intraepithelial neoplasia (CIN). We investigated HLA class I and beta2-microglobulin expression by immunohistochemistry in tumor and adjacent CIN. Loss of heterozygosity (LOH) was studied using microsatellite markers covering the HLA region. Fluorescent in situ hybridization with HLA class I probes was performed to investigate the mechanism of HLA loss. Immunohistochemistry showed absent or weak HLA class I expression in 11/12 cases. In 10 of these 11 cases, downregulation occurred in both tumor and CIN. Only in one case did the concomitant CIN lesion show normal expression. In 9/12 cases, LOH was present for at least one marker in both tumor and CIN, 1 case showed only LOH in the CIN lesion, and 1 case showed retention of heterozygosity for all markers in both tumor and CIN. We conclude that HLA class I aberrations occur early and frequently in cervical carcinogenesis. This might allow premalignant CIN lesions to escape immune surveillance and progress to invasive cancer.

Polymorphic amino acids at codons 9 and 37 of HLA-DQB1 alleles may confer susceptibility to cervical cancer among Chinese women

Cervical cancer is strongly associated with the infection by oncogenic forms of human papillomavirus (HPV). Although most women are able to clear HPV infection, some develop persistent infections that may lead to cancer, implying genetic susceptibility factors for malignant progression. To verify whether HLA class II DQB1 polymorphism is related to cervical cancer in Chinese population, HLA-DQB typing was carried out by PCR-SBT for 258 patients with cervical cancer and 284 healthy controls, and the allele frequencies were calculated. In this study, HLA-DQB1*060101 and DQB1*0602 alleles were significantly higher in the HPV16 infected patients with cervical cancer compared with healthy controls (chi(2) = 31.7452, p < 0.0001; chi(2) = 12.7838, p(c) = 0.0066), but DQB1*050201 allele was significantly lower (chi(2) = 26.2187, p < 0.0001). This result indicates that HLA-DQB1*060101 and DQB1*0602 may confer susceptibility to cervical cancer, and DQB1*050201 may contribute to the resistance to the development of cervical cancer among Chinese women. Sequence analysis reveals that DQB1*060101 allele encodes Leu at position 9 and Asp at position 37, unique to the susceptibility to cervical cancer, whereas the other DQB1 alleles encode Phe or Tyr and Ile or Tyr at the same two positions, respectively. This finding implies that polymorphic amino acids at the putative antigen binding residues 9 and 37 of HLA-DQB1 alleles may play an important role in the development of cervical cancer.

Resistance to microtubule-stabilizing drugs involves two events: beta-tubulin mutation in one allele followed by loss of the second allele

Resistance to Taxol (paclitaxel) or the epothilones (Epo) occurs via the acquisition of point mutations in beta-tubulin residues important for drug-tubulin binding. We have isolated four drug-resistant clones selected with Taxol or Epo A, which harbor distinct beta-tubulin mutations. During the development of a stable drug-resistant phenotype, early clones expressing both wild-type (wt) and mutant beta-tubulin sequences exhibited a 10-fold drug resistance, while more advanced clones expressing only the mutant beta-tubulin sequence exhibited 30 to 50-fold drug resistance. The drug-sensitive parental 1A9 ovarian carcinoma cell line and the drug resistant clones (1A9-A8, 1A9-PTX10 and 1A9-PTX22) were evaluated for loss of heterozygosity (LOH) for beta-tubulin (6p25) by single nucleotide polymorphism (SNP) and fluorescent in situ hybridization (FISH) analyses. Functional assays such as drug-induced tubulin polymerization, cell cycle analysis by FACS, DNA sequencing for beta-tubulin and mitotic index by immunofluorescence were performed to correlate the beta-tubulin LOH status with drug response in the early- and late-step drug-resistant clones. Late-step drug resistant clones revealed LOH in one allele for wt beta-tubulin in addition to a beta-tubulin mutation in the other allele leading to increased levels of drug resistance, while the early-step clones that contained both a wt and a mutant beta-tubulin allele were considerably less drug resistant. The LOH and functional assays revealed cell response that was proportional to the tubulin gene and heterozygosity status. Acquired tubulin mutations in conjunction with LOH for the wt tubulin resulted in a highly resistant phenotype, revealing a new mechanism for taxane resistance.

Characterization of HPV genotype profile in squamous cervical lesions in Portugal, a southern European population at high risk of cervical cancer

A different prevalence of human papillomavirus (HPV) types has been reported in distinct populations. Although Portugal has a relatively high incidence of cervical cancer within the European Union, no studies have been reported in the Portuguese population. Recently, a clinical trial using a vaccine targeted against HPV-16 demonstrated a high efficacy in preventing HPV-16 cervical lesions. The aim of the present study was the characterization of HPV genotype profile in squamous intraepithelial lesions (SIL) and invasive cervical cancer (ICC) from 608 patients using polymerase chain reaction (PCR) methodology. We frequently detected HPV-6/11 and HPV-16 in low-grade SIL (HPV-6/11, 18.9%; HPV-16, 44.2%). In high-grade SIL, HPV-16 was demonstrated in 74.2% of those lesions and in 80.0% of the cases with ICC. HPV-18 was found in 3.1%, 0.8% and in 15.0% of low, high SIL and ICC, respectively. The overall prevalence of multiple infections with high-risk HPV was 7.2%. Other types of HPV were detected in 7.0% of all cases. Our results demonstrate a high prevalence of HPV-16 in SIL and ICC in Portuguese women. Therefore, a prophylactic HPV-16/18 vaccine may be effective in the prevention of cervical cancer in a significant number of women from this southern European population.

The influence of smoking and other cofactors on the time to onset to cervical cancer in a southern European population

Cervical cancer is a complex and multifactorial disease. Although there are substantial data supporting the causative role of persistent human papillomavirus (HPV) infection in the development of cervical cancer, the complete course of the disease has never been completely understood. Several risk cofactors have been suggested with controversial results. Portugal has the highest incidence of squamous cell carcinoma (SCC) within western Europe and there are no known studies regarding the role of cofactors in SCC. The aim of our study was to evaluate the role of smoking, sexual behaviour, reproductive and contraceptive history, in the time-to-onset (TTO) of severe cervical lesions (HGSIL/SCC) in the Portuguese population. We verified that age of first sexual intercourse under 18 years (odds ratio (OR) 2.8), pregnancy (OR 2.9), first pregnancy under 21 years (2.6), number of pregnancies (OR 2.3-5.4) and parity (OR 1.9-5.7) are risk factors in the development of cervical neoplasia. Smoke exposure index (SEI) was significantly different (P=0.002) between cases and controls. Our results regarding time-to-onset demonstrate that smoking (P<0.001, log rank test), number of sexual partners (P<0.001, log rank test) and use of oral contraceptives (P<0.001, log rank test) are important determinants in the earlier onset of severe cervical lesions. Using this approach, our findings may help to clarify the role of smoking and other cofactors in the persistence and progression of cervical lesions.

HPV-mediated transformation of the anogenital tract

Infection with high-risk human papillomavirus (HR-HPV) has been associated with intraepithelial neoplasia and carcinomas at various sites of the anogenital tract, including the cervix, vulva, vagina, penis and anus. Although HR-HPV is a necessary cause for cervical cancer, the majority of anal cancers and a subset of cancers at other genital sites, additional (epi)genetic events are required for malignant transformation. HPV-mediated transformation of human epithelial cells has been recognized as a multi-step process resulting from deregulated transcription of the viral oncogenes E6 and E7 in the proliferating cells. Interference of E6 and E7 with cell cycle regulators induces genetic instability, which drives the continuous selection of oncogenic alterations providing cells with a malignant phenotype. Early genetic events during cervical carcinogenesis associated with immortalization, include deletions at chromosomes 3p, 6 and 10p, whereas amongst others gain of chromosome 3q, loss of chromosome 11 and epigenetic alterations such as inactivation of the TSLC1 tumor suppressor gene represent later events associated with tumor invasion.

Loss of heterozygosity in the HLA class I region in human pancreatic cancer

An altered human leukocyte antigen (HLA) class I expression constitutes an important tumor-escape mechanism counteracting T-cell mediated immune responses. We utilized the technique of microsatellite analysis to characterize the loss of heterozygosity (LOH) in the HLA class I region in 24 samples of patients with human ductal pancreatic carcinoma. The expression of HLA class I and the infiltration by T cells were studied in parallel by standard immunohistochemistry. The present study demonstrates LOH in the HLA class I region in five patients with pancreatic carcinoma. Immunohistochemical analysis showed that pancreatic carcinomas were frequently characterized by a total or partial loss of expression in HLA class I antigen. The positive or negative LOH status corresponded with the expression analysis in eight cases. Reduction of HLA class I expression without LOH was found in 14 cases. Lymphocyte infiltration with CD3+, CD4+, and CD8+ T cells did not show significant differences between LOH-positive and LOH-negative tumors. In conclusion, LOH does not seem to be the only factor for the reduced expression of HLA class I antigen as well as for the T-cell infiltration in this type of tumor.