Decreased programmed cell death in the uterine cervix associated with high risk human papillomavirus infection

HPV infection and its correlation with p53 and Bcl-2 among pregnant mothers and their infants

The investigation of perinatal transmission of HPV is vital for early screening of cervical/oral cancers. Here, transmission of HPV from the pregnant women to their infants was studied. p53 and Bcl-2 expressions and their correlations with HPV infection were examined. HPV infection was detected in the cervical and oral swabs of 135 mother-baby pairs employing both PCR and HC-II methods. 1 year follow-up with an interim visit at 3 months for mothers and 6 months for babies was performed. Immunocytochemistry of p53 and Bcl-2 using the streptavidin-biotin peroxidase method was performed. Prevalence of HPV infection in the mothers was 28.14%, (38/135) and 30.37% (41/135) determined by the PCR and HC-II methods respectively. HPV 16 and/or 18 was identified in 81.57% (31/38) and 82.92% (34/41) of the HPV + women estimated by PCR and HC-II methods respectively. Prevalence rate of HPV 16 among the HPV + pregnant women was 63.15% (24/38) and 65.85% (27/41) determined by PCR and HC-II methods respectively. The frequency of perinatal transmission was 21.05% (8/38) and 21.95% (9/41) determined by PCR and HC-II methods respectively at birth. The HPV + infants in the follow up study cleared the infection within 6 weeks. An abnormal nuclear expression of p53 and cytoplasmic expression of Bcl-2 were observed in the HPV + mother-baby pairs. Cesarean section did not protect the infants against perinatal HPV transmission. The detection of p53 and Bcl-2 proteins in the HPV + mother-baby pairs suggests that these biomarkers may be important in the early screening of oral/cervix cancers in positive cases.

RBBP6 Is Abundantly Expressed in Human Cervical Carcinoma and May Be Implicated in Its Malignant Progression

RBBP6 is a novel gene encoding splicing-associated proteins. There are 3 protein isoforms (isoforms 1-3). RBBP6 isoforms 1 has been shown to interact with both p53 and Rb. It also plays a role in the induction of apoptosis and the regulation of the cell cycle. The expression of RBBP6 has been documented in several cancers but RBBP6 expression in cervical cancer has not been well studied. The aim of this study was to establish expression levels and tissue distribution of the RBBP6 gene products at both protein and messenger RNA (mRNA) levels in cervical cancer by immunocytochemistry and in situ hybridization (ISH). A link between RBBP6 expression, apoptosis, and cervical cancer progression was also investigated. RBBP6 mRNA was expressed in the nuclei and cytoplasm of normal and tumour cervical epithelium. In general, expression was high in the cytoplasm and nuclei of moderately differentiated and invasive carcinoma. Immunolabelling results were confirmed by image analysis and ISH experiments. Apoptosis assays using TUNEL correlated with the expression of the RBBP6 gene in all examined cases. This is the first report on the abundant expression of RBBP6 in cervical cancer and its involvement in the malignant progression of cervical cancer. Because of the high expression and corresponding pro-apoptotic activity observed in cervical cancer cells in this study, we suggest that RBBP6 is involved in the malignant progression of cervical cancer. RBBP6 proteins can therefore be targeted for therapeutic interventions against cervical cancer.

Production of interleukin‑4 in CD133+ cervical cancer stem cells promotes resistance to apoptosis and initiates tumor growth

The cancer stem cell (CSC) theory suggests that cancer growth and invasion is dictated by the small population of CSCs within the heterogenous tumor. The aim of the present study was to elucidate the cause for chemotherapy failure and the resistance of CSCs to apoptosis. A total of ~2.3% cluster of differentiation (CD)133⁺ cancer stem-like side population (SP) cells were identified in cases of uterine cervical cancer. These CD133⁺ SP cells were found to potently initiate tumor growth and invasion, as they exhibit transcriptional upregulation of stemness genes, including octamer-binding transcription factor-4, B-cell-specific Moloney murine leukemia virus insertion site-1, epithelial cell adhesion molecule, (sex determining region Y)-box 2, Nestin and anti-apoptotic B cell lymphoma-2. In addition, the CD133⁺ SP cells showed resistance to multi-drug treatment and apoptosis. The present study further showed that the secretion of interleukin-4 (IL-4) in CD133⁺ cervical cancer SP cells promoted cell proliferation and prevented the SP cells from apoptosis. Following the neutralization of IL-4 with anti-IL-4 antibody, the CD133⁺ SP cells were more sensitive to drug treatment and apoptosis. Therefore, the data obtained in the present study suggested that the autocrine secretion of IL-4 promotes increased survival and resistance to cell death in CSCs.

HPV16 E2-mediated potentiation of NF-κB activation induced by TNF-α involves parallel activation of STAT3 with a reduction in E2-induced apoptosis

Human papilloma virus is associated with cervical and other tumors, and several cellular conditions also play an important role in carcinogenesis. Human papilloma virus (HPV)-infected cells exhibit activation of NF-κB and STAT3 (mediators of inflammation), but little is known about their regulation by HPV. This study attempts to understand the role of HPV16 E2, an important early protein of HPV16, in the regulation of NF-κB and STAT3 by reporter assays, quantitative reverse transcriptase-polymerase chain reaction, and immunoblotting. We demonstrate that E2 enhances NF-κB activation induced by TNF-α, a proinflammatory cytokine, in both non-tumor- and tumor-derived epithelial cell lines besides potentiating STAT3 transcriptional activity induced by TNF-α in HEK293 cells. E2 increases the expression of RelA and its transcriptional activation, and retention of E2 was observed in the nucleus with significant interaction with RelA (immunoprecipitation) upon TNF-α treatment. Transfection with shRNA-RelA or pretreatment with a STAT3 inhibitor had a negative effect on the ability of E2 to enhance TNF-α-induced NF-κB activation. Experiments with co-expression of a mutant of STAT3 with E2 also suggested that the activation of STAT3 is indispensible for TNF-α-induced NF-κB activation. Inhibition of STAT3 activation enhanced E2-induced apoptosis, whereas parallel activation of NF-κB and STAT3 by the combined action of E2 and TNF-α increased the expression of their common targets, cyclin-D1, c-Myc, survivin, and Bcl-2, leading to a decrease in E2-induced apoptosis (viability and cell cycle). Our results reveal novel mechanisms by which E2 may regulate NF-κB and STAT3 activation in the presence of TNF-α with implications on the survival of HPV-infected cells.

Human papillomavirus infection and its possible correlation with p63 expression in cervical cancer in Japan, Mongolia, and Myanmar

Although human papillomavirus (HPV) 16 is the cause of cervical cancer in most countries including Japan, the involvement of cervical cancer with HPV types in Mongolian and Myanmar populations is largely unknown. We examined the expression of HPV in formalin-fixed and paraffin-embedded cervical tissues from 40 Japanese, 32 Mongolian, and 30 Myanmar cervical cancer patients. We performed immunohistochemistry using anti-HPV16 and anti-HPV 1, 6, 11, 16, 18 and 31 cocktail and then correlated it with the expression of Ki-67 and p63. HPV 16 was detected in 72%, 65% and 50% of Japanese, Mongolian and Myanmar cervical cancer patients, respectively, whereas 5 (13%) of the 40 patients, 8 (25%) of the 32 patients and 7 (23%) of the 30 patients in HPV 16-negative cancers were positive for other HPV types included in the cocktail, respectively. Ki-67 labeling index (LI) as well as p63 LI was significantly higher in HPV 16-positive patients than in HPV 16-negative ones in the Japanese and Mongolian samples. p63 expression was significantly associated with stage III and IV in Japan and Mongolia. These findings suggest that HPV 16 may be associated with cell proliferative activity and tumor progression, possibly depending upon the expression of p63 in the cervical cancer. In addition, immunohistochemical detection for distinguishing the type of HPV may also be useful for cervical cancer in the clinical setting.

Gene expression profile of cervical and skin tissues from human papillomavirus type 16 E6 transgenic mice

Background

Although K14E6 transgenic mice develop spontaneous tumors of the skin epithelium, no spontaneous reproductive tract malignancies arise, unless the transgenic mice were treated chronically with 17β-estradiol. These findings suggest that E6 performs critical functions in normal adult cervix and skin, highlighting the need to define E6-controlled transcriptional programs in these tissues.

Methods

We evaluated the expression profile of 14,000 genes in skin or cervix from young K14E6 transgenic mice compared with nontransgenic. To identify differentially expressed genes a linear model was implemented using R and the LIMMA package. Two criteria were used to select the set of relevant genes. First a set of genes with a Log-odds ≥ 3 were selected. Then, a hierarchical search of genes was based on Log Fold Changes.

Results

Microarray analysis identified a total of 676 and 1154 genes that were significantly up and down-regulated, respectively, in skin from K14E6 transgenic mice. On the other hand, in the cervix from K14E6 transgenic mice we found that only 97 and 252 genes were significantly up and down-regulated, respectively. One of the most affected processes in the skin from K14E6 transgenic mice was the cell cycle. We also found that skin from transgenic mice showed down-regulation of pro-apoptotic genes and genes related to the immune response. In the cervix of K14E6 transgenic mice, we could not find affected any gene related to the cell cycle and apoptosis pathways but did observe alterations in the expression of immune response genes. Pathways such as angiogenesis, cell junction and epidermis development, also were altered in their gene expression profiles in both tissues.

Conclusion

Expression of the HPV16 E6 oncoprotein in our model alters expression of genes that fell into several functional groups providing insights into pathways by which E6 deregulate cell cycle progression, apoptosis, the host resistance to infection and immune function, providing new opportunities for early diagnostic markers and therapeutic drug targets.

p53 Loss synergizes with estrogen and papillomaviral oncogenes to induce cervical and breast cancers

Whereas the tumor suppressor p53 gene is frequently mutated in most human cancers, this is not the case in human papillomavirus (HPV)-associated cancers, presumably because the viral E6 oncoprotein inactivates the p53 protein. The ability of E6 to transform cells in tissue culture and induce cancers in mice correlates in part with its ability to inactivate p53. In this study, we compared the expression of the HPV16 E6 oncogene to the conditional genetic disruption of p53 in the context of a mouse model for cervical cancer in which estrogen is a critical cofactor. Nearly all of the K14Crep53(f/f) mice treated with estrogen developed cervical cancer, a stark contrast to its complete absence in like-treated K14E6(WT)p53(f/f) mice, indicating that HPV16 E6 must only partially inactivate p53. p53-independent activities of E6 also contributed to carcinogenesis, but in the female reproductive tract, these activities were manifested only in the presence of the HPV16 E7 oncogene. Interestingly, treatment of K14Crep53(f/f) mice with estrogen also resulted in mammary tumors after only a short latency, many of which were positive for estrogen receptor alpha. The majority of these mammary tumors were of mixed cell types, suggestive of their originating from a multipotent progenitor. Furthermore, a subset of mammary tumors arising in the estrogen-treated, p53-deficient mammary glands exhibited evidence of an epithelial to mesenchymal transition. These data show the importance of the synergy between estrogen and p53 insufficiency in determining basic properties of carcinogenesis in hormone-responsive tissues, such as the breast and the reproductive tract.

Analyses of Bcl-2, Survivin, and CD44v6 expressions and human papillomavirus infection in cervical carcinomas

Infection with human papillomaviruses (HPV), and suppression of apoptosis and cell adhesion are putative aetiological factors to cervical carcinogenesis. However, controversial results have been reported with respect to their relationships with cervical carcinomas. Here we analysed papillomavirus infection, apoptotic index (AI), expressions of the anti-apoptotic proteins Bcl-2 and Survivin, and expression of the cell-adhesion protein CD44 in cervical tissue samples from individuals with and without cervical carcinomas. Although both HPV16 and HPV18 are reportedly important aetiological factors, we found that cervical carcinomas were highly associated with HPV16 but not HPV18 infection. Immunohistochemistry showed that the percentages of cells expressing Bcl-2, Survivin, and CD44v6 were greatly increased in samples of cervical carcinomas. Furthermore, the expression rates of Survivin and CD44v6 increased whereas that of Bcl-2 declined as cervical cancers developed into more advanced clinical or histopathological stages. Surprisingly, there was little difference in AI between control and cervical cancer samples. These observations provide further evidence that HPV infection, apoptosis and cell adhesion abnormalities are related to cervical cancers. They also suggest that Bcl-2, Survivin and CD44v6 expressions, and HPV16 infection could be useful indices in screening of cervical carcinomas.

Coexpression of Notch1 and NF-κB signaling pathway components in human cervical cancer progression

OBJECTIVES

Features of deregulated Notch1 signaling and NF-kappaB activation have independently been reported in cervical cancers. Here, we have extended these observations and examined both these pathways simultaneously in human cervical cancer tissue. Further, we have investigated the potential cross-talk between these pathways in a human cervical cancer derived cell line CaSki, which mirrors features of Notch activation as in the majority of human cervical cancers.

METHODS

Cervical tissue samples were analyzed for the expression of Notch1, Jagged 1, Hes1, pAKT, NF-kappaB p50, NF-kappaB p65, IkappaB-alpha, Bcl-2, CyclinD1, Cdk9, c-Fos, and p53 by immunohistochemistry. A total of 352 samples were analyzed which included 69 normal cervical tissue, 132 preinvasive lesions and 151 squamous cell carcinomas of the uterine cervix. Dual immunofluorescent analysis was performed to evaluate the coexpression of Notch1 and NF-kappaB. Transcriptional reporter assays and xenografts were undertaken with CaSki cells.

RESULTS

Features of Notch1 activation as measured by intracellular Notch1, high levels of Jagged1, Hes1 and Cdk9 were paralleled by nuclear translocation of both NF-kappaB p50 and p65 with target gene expression (IkappaB-alpha, Bcl-2, and CyclinD1) in human cervical cancer sections. Reporter assays in CaSki cells are consistent with Notch being an upstream regulator of NF-kappaB. Further, the xenografts recreate key aspects of human cancer tissue.

CONCLUSIONS

Results from this study suggest that there is a co-activation of Notch1 and NF-kappaB signaling pathways at the cellular level in the majority of human cervical cancers, with Notch as an upstream regulator.

Infection of human immunodeficiency virus and intracellular viral Tat protein exert a pro-survival effect in a human microglial cell line

The interaction of human immunodeficiency virus type 1 (HIV-1) with CD4+ T lymphocytes is well studied and typically results in virally induced cytolysis. In contrast, relatively little is known concerning the interplay between HIV-1 and microglia. Recent findings suggest that, counter-intuitively, HIV-1 infection may extend the lifespan of microglia. We developed a novel cell line model system to confirm and mechanistically study this phenomenon. We found that transduction of a human microglial cell line with an HIV-1 vector results in a powerful cytoprotective effect following apoptotic challenge. This effect was reproduced by ectopic expression of a single virus-encoded protein, Tat. Subsequent studies showed that the pro-survival effects of intracellular Tat could be attributed to activation of the PI-3-kinase (PI3K)/Akt pathway in the microglial cell line. Furthermore, we found that expression of Tat led to decreased expression of PTEN, a negative regulator of the PI-3-K pathway. Consistent with this, decreased p53 activity and increased E2F activity were observed. Based on these findings, a model of possible regulatory circuits that intracellular Tat and HIV-1 infection engage during the cytoprotective event in microglia has been suggested. We propose that the expression of Tat may enable HIV-1 infected microglia to survive throughout the course of infection, leading to persistent HIV-1 production and infection in the central nervous system.

Germline genetic polymorphisms of CYP1A1, GSTM1 and GSTT1 genes in Indian cervical cancer: Associations with tumor progression, age and human papillomavirus infection

OBJECTIVES

Host genetic factors may play a role in human papillomavirus (HPV)-associated tumorigenesis, although the issue continues to be a focus of much debate. Biotransformation is critical in carcinogenic activity of numerous environmental carcinogens. It is therefore possible that polymorphisms of genes producing functional changes in xenobiotic metabolizing enzymes may be susceptible factors in cervical carcinogenesis. This study looked into possible relationships among these factors.

METHODS

In this case-control study, we analyzed leukocyte DNA from a total of 312 subjects for germline polymorphisms of CYP1A1 (m1 and m2), GSTM1 and GSTT1 at various stages of the cervical tumor progression spectrum, using PCR and RFLP.

RESULTS

Both m1 and m2 polymorphisms of the CYP1A1 gene were more frequent among cases (36.1% for m1 and 38.1% for m2) compared to control subjects (18.2% and 17.6% respectively). The odds ratio of a subject with homozygous CYP1A1 m1 and m2 variant being a case was highest (m1 OR = 4.77 [95% CI = 1.28-17.77]; P = 0.02 and m2 OR = 5.48 [95% CI = 1.49-20.19]; P = 0.011) respectively. The distribution of m1 and m2 CYP1A1 genotypes was also studied as a function of age and in relation to the presence of HPV 16 infection. The risk due to CYP1A1 m1 genotype, when adjusted for HPV status, showed a significantly increased risk (OR = 3.58, 95% CI = 1.88-6.81; P = 0.0001). Similar results were observed in the case of CYP1A1 m2 variant and HPV 16. There was a significant over-representation of both m1 (25.9% vs. 13.9%) and m2 (27.9% vs. 13.3%) polymorphisms in older women (46 years or more). GSTM1 and GSTT1 deletions were also prominent among cases (53.7% and 16.3% respectively) compared to controls (32.7% and 9.7% respectively). A higher proportion of both GSTT1 and GSTM1 deletions were also detected in HPV-16-positive subjects.

CONCLUSIONS

These results suggest that polymorphisms in the CYP1A1, GSTM1 and GSTT1 genes may render women more susceptible to the development of cervical cancer. The association between this susceptibility and the presence of human papillomavirus infection further emphasizes the significance of the genetic polymorphisms.

BCL2 family of apoptosis-related genes: functions and clinical implications in cancer

One of the most effective ways to combat different types of cancer is through early diagnosis and administration of effective treatment, followed by efficient monitoring that will allow physicians to detect relapsing disease and treat it at the earliest possible time. Apoptosis, a normal physiological form of cell death, is critically involved in the regulation of cellular homeostasis. Dysregulation of programmed cell death mechanisms plays an important role in the pathogenesis and progression of cancer as well as in the responses of tumours to therapeutic interventions. Many members of the BCL2 (B-cell CLL/lymphoma 2; Bcl-2) family of apoptosis-related genes have been found to be differentially expressed in various malignancies, and some are useful prognostic cancer biomarkers. We have recently cloned a new member of this family, BCL2L12, which was found to be differentially expressed in many tumours. Most of the BCL2 family genes have been found to play a central regulatory role in apoptosis induction. Results have made it clear that a number of coordinating alterations in the BCL2 family of genes must occur to inhibit apoptosis and provoke carcinogenesis in a wide variety of cancers. However, more research is required to increase our understanding of the extent to which and the mechanisms by which they are involved in cancer development, providing the basis for earlier and more accurate cancer diagnosis, prognosis and therapeutic intervention that targets the apoptosis pathways. In the present review, we describe current knowledge of the function and molecular characteristics of a series of classic but also newly discovered genes of the BCL2 family as well as their implications in cancer development, prognosis and treatment.

DNA damaging drugs-induced down-regulation of Bcl-2 is essential for induction of apoptosis in high-risk HPV-positive HEp-2 and KB cells

DNA damaging chemotherapeutic agents like carboplatin (Carb) and 5-fluorouracil (5-FU), whose effects are mediated through diverse intracellular targets, induce apoptosis in various cancer cells including human papillomavirus (HPV) positive HEp-2 and KB cells. The present work reports the involvement of Bcl-2 in response to the exposure of HEp-2 and KB cells to Carb or 5-FU. We demonstrate that both these drugs are potent inducers of apoptosis. Apoptosis was preceded by decrease in Bcl-2 protein level accompanied by caspase-9 activation and poly(ADP-ribose) polymerase (PARP) cleavage without altering Bax expression. Further analysis revealed down-regulation of Bcl-2 mRNA as well as protein in drugs treated cells. Ectopic expression of Bcl-2 protected cells against drugs mediated DNA damage-induced apoptosis. Overall, data indicates that genotoxic stress leads to down-regulation of Bcl-2 in HEp-2 and KB cells, which plays a decisive role in the outcome of stress in these cells.

Human papillomavirus and disease mechanisms: relevance to oral and cervical cancers*

Oral squamous cell carcinoma (OSCC) is the sixth most common malignancy and is a major cause of cancer morbidity and mortality worldwide. Carcinoma of the uterine cervix is the most common female malignancy in the world. While cervical cancer is a worldwide disease, oral cancer has the highest incidence in developing countries, especially among tobacco and alcohol users and betel quid chewers. A strong association of cervical and oral cancer with high-risk human papillomavirus (HPV) 16 and 18 infections underlines the importance of the virus in the pathogenesis of these squamous cell carcinomas. Functionally high-risk HPV infection contributes to carcinogenesis and tumor progression predominantly through the actions of two viral oncogenes, E6 and E7. The E6 and E7 genes have been studied in different patient populations and a number of variants have been described. More than 40 variants have been classified and may be related to differences in progression of squamous intraepithelial lesions. The transcription factor, NFkappaB and its activation pathways are frequently targeted by viruses and aberrant constitutive activation of NFkappaB is frequently found in human tumors of diverse tissue origin. Diet-gene interactions are also likely to contribute considerably to the observed inter-individual variations in HPV associated cancer risk, in response to exposures to the nutritional factors that have the potential to promote or protect against cancer.

Expression of Ki-67 and squamous intraepithelial lesions are related with HPV in endocervical adenocarcinoma

To estimate the association between human papillomavirus (HPV) status and the expression of p53, Ki-67 and bcl-2 in cases of endocervical adenocarcinoma, and the relation with squamous intraepithelial lesions (SIL) and age, 229 cases were selected, treated between 1995 and 2003 in the Hospital Nossa Senhora da Conceiçao. All samples were evaluated by polymerase chain reaction to determine HPV status. Immunohistochemical technique was used to investigate the expression of p53, Ki-67 and bcl-2. The joint occurrence of endocervical adenocarcinoma and SIL were estimated too. In the 229 evaluated cases, 182 cases (79.48%) were associated with the presence of the HPV. The most common types were HPV18 (93 cases - 51.09%) and HPV16 (62 cases - 34.06%). Expression of Ki-67 (p=0.009) and the presence of SIL (p=0.018) were associated to HPV infection. Expression of p53 (p=0.647) and bcl-2 (p=0.671) were not related to HPV status. The mean age of the patients was 53.2 years, without clear correlation between age group and HPV (p=0.095). The presence of HPV, especially type 18 in endocervical adenocarcinoma suggests that this agent can be an important cofactor in the development and progression of glandular neoplasms of the uterine cervix. The joint occurrence of endocervical adenocarcinoma and SIL may support this hypothesis. HPV may promote an increased proliferation index in endocervical adenocarcinoma, shown by the expression of Ki-67.

Estrogen receptor, progesterone receptor, and bcl-2 are markers with prognostic significance in CIN III

There are no known biological markers or technologies to predict the natural history of an individual CIN III. The probability of progression is considered greater with the persistence of high-risk human papillomavirus (HPV) infection and age. p53 polymorphism has been associated with cervical carcinogenesis. Hormone-induced cervical cancer is mediated by estrogen receptor (ER) and progesterone receptor (PR). In cervical cancer, increased bcl-2 and Bax immunoreactivity is generally associated with a better prognosis. The purpose of this study was to evaluate the value of HPV 16 and HPV 18 typing and p53 codon polymorphism genotyping by polymerase chain reaction and ER, PR, bcl-2, and Bax expression by immunohistochemistry in predicting the CIN III clinical behavior of CIN III lesions. We studied the expression of these prognostic factors in the CIN III adjacent to squamous cell microinvasive carcinomas of the cervix (MIC) from 29 patients with FIGO stage IA1 cervical cancer and in 25 patients with CIN III and no documented focus of invasion. In the MIC group, only the CIN III was considered at least 2 mm away from the microinvasive complex. The ER, PR, bcl-2, and Bax immunoreactivity was scored as positive (>10% staining cells) and negative (<10% staining cells). No significant difference was observed between MIC and CIN III group concerning HPV infection and p53 polymorphism. The ER, PR, bcl-2, and Bax immunohistochemical expression was stronger and more frequent in the CIN III group. After multivariable analysis, coexpression of ER, PR, and bcl-2 was the only independent factor in defining low risk of progression for CIN III. Our study suggests that coexpression of ER, PR, and bcl-2 may be a useful tool in identifying the CIN III lesions with low risk of progression to cervical cancer.

HPV DNA and survivin expression in epithelial oral carcinogenesis: a relationship?

HPV has been thought to be involved in the development of several oral diseases, such as premalignant mucosal lesions and oral carcinoma. Survivin is a recently characterized IAP protein, which is abundantly expressed in most solid and haematological malignancies, but undetectable in normal adult tissues. Aim of this study was to investigate survivin expression and HPV presence in oral premalignant lesions and oral carcinoma. 47 samples of oral tissue including 11 squamous cell carcinomas (OSCC), 16 oral leukoplakias (OL) and 20 normal oral mucosa specimens, after investigation of HPV presence by nested PCR (consensus MY/GP primers) and viral genotype identification by direct sequencing were investigated by immunohistochemistry to detect survivin expression. Survivin expression was evident in 4/7 (57.1%) HPV+ and 4/4 (100%) HPV- OSCC, 6/7 (85.7%) HPV+ and 5/9 (55.5%) HPV- OL and in 0/20 (0%) control samples. Data showed high levels of survivin expression in HPV-positive SCCs, even if mean values were lower than HPV-negative ones, which in particular showed survivin expression in 100% of cases. Conversely, survivin expression was greater in HPV+ precancerous lesions than in HPV- ones. Our findings suggest that survivin may be involved in HPV- mediated deregulation during maturation of squamous epithelium through modulation of the apoptotic processes and, conversely, HPV may have a direct or indirect effect on the regulation of the survivin expression level. In particular, the results of this study suggest distinguishing between cancerous and precancerous oral lesions with respect to survivin expression when HPV infection is present. The most unfavourable behaviour is likely to be for the HPV- OSCC.

Co-overexpression of p53 and bcl-2 proteins in HPV-induced squamous cell carcinoma of the uterine cervix

OBJECTIVE

The aim of this study was to analyze aberrant expression of both apoptotic protein p53 and antiapoptotic protein bcl-2 in squamous cell carcinoma (SCC) of the uterine cervix with HPV infection and its significance as a marker for progression of cervical lesions.

METHODS

One hundred and five cervical lesions and 20 normal (age matched) cervical epithelium from patients with complaints other than cervical lesions were investigated immunocytochemically for aberrant expression of p53 and bcl-2 using the streptavidin-biotin-peroxidase method with respective monoclonal antibodies. HPV status was also anlayzed using type-specific primers for HPV 16/18 and HPV 6/11 by polymerase chain reaction (PCR). The statistical correlation analysis was carried out using Spearman's correlation test and univariate analysis by the SPSS system.

RESULTS

An abnormal nuclear expression of tumor-suppressor protein p53 and cytoplasmic expression of bcl-2 were observed using immunocytochemistry in biopsies of cervical lesions but not in normal subjects. The intensity of immunoreactivity for both p53 and bcl-2 proteins varied between different histopathological grades of cervical lesions and the correlation analysis showed a highly significant positive correlation for their expression level with different stages from mild dysplasia to invasive cancer with r = 0.88842; P = 0.00001 and r = 0.86929; P = 0.00001, respectively. A highly significant positive correlation was also observed between the expression of both p53 and bcl-2 proteins and HPV infection. The current study indicates a very good significant direct correlation (r = 0.83925; P = 0.00001) between p53 expression and bcl-2 expression in the study population, suggesting the co-overexpression of these proteins in HPV-associated cervical cancer.

CONCLUSIONS

From the observations it is suggested that the immunodetection of both p53 and bcl-2 proteins in squamous cell carcinoma of the uterine cervix can be used as an independent diagnostic marker for cervical cancer associated with HPV infection. The highly significant association of these proteins with HPV infection suggests that the high-risk HPV infection may be responsible for the co-overexpression of p53 and bcl-2 in cervical cancer even though both of them are antagonistic in their function. This study thus helps to understand the molecular mechanism underlying cervical carcinogenesis and which in turn may improve the therapeutic approach.

Expression of folate receptors and heterogeneous nuclear ribonucleoprotein E1 in women with human papillomavirus mediated transformation of cervical tissue to cancer

AIMS

Folate receptors (FRs) mediate cellular uptake of folates in many cancer cells and in folate deficiency heterogeneous nuclear ribonucleoprotein E1 (hnRNP-E1) mediates translational upregulation of FR in cultured cervical cancer cells. hnRNP-E1 can also interfere with human papillomavirus 16 (HPV-16) viral capsid protein synthesis (and thereby HPV proliferation) in vitro. This study aimed to evaluate prospectively the relevance of FR and hnRNP-E1 expression in the normal cervix, cervical dysplasia, and cancer.

METHODS

Cervical tissues from 12 women with normal histology and 69 consecutive women with varying grades of cervical dysplasia and cancer were prospectively evaluated for immunohistochemical expression of FR, hnRNP-E1, proliferating cell nuclear antigen (PCNA), and HPV. There were 22 women with low grade squamous intraepithelial lesions (LGSIL), 22 with high grade squamous intraepithelial lesions (HGSIL), and 25 with invasive cervical carcinoma.

RESULTS

Among normal subjects, 100% and 92% expressed hnRNP-E1 and FR, respectively. FR expression decreased from 91% in LGSIL to 68% and 64% in women with HGSIL and cancer, respectively. Similarly, hnRNP-E1 expression decreased from 86% in LGSIL to 68% and 40% in HGSIL and cancer, respectively. There was a highly significant positive correlation between the extent of FR and hnRNP-E1 expression, and an inverse correlation between HPV infection and hnRNP-E1 expression during progression of cervical dysplasia to cancer.

CONCLUSION

These results are consistent with a hypothesis that reduced hnRNP-E1 expression may be permissive for HPV proliferation and progression to cervical cancer, and support the need for prospective longitudinal studies of hnRNP-E1 expression in HPV-16 infected women.

Activated Notch1 inhibits p53-induced apoptosis and sustains transformation by human papillomavirus type 16 E6 and E7 oncogenes through a PI3K-PKB/Akt-dependent pathway

Activated Notch1 (AcN1) alleles cooperate with oncogenes from DNA tumor viruses in transformation of epithelial cells. AcN1 signaling has pleiotropic effects, and suggested oncogenic roles include driving proliferation through cyclin D1 or the generation of resistance to apoptosis on matrix withdrawal through a phosphatidylinositol 3-kinase (PI3K)-PKB/Akt-dependent pathway. Here, we extend the antiapoptotic role for AcN1 by showing inhibition of p53-induced apoptosis and transactivation. Chemical inhibitors of the PI3K pathway block AcN1-induced inhibition of p53-dependent apoptosis and nuclear localization of Hdm2. We show that expression of wild-type p53 does not inhibit synergistic transformation by AcN1 and human papillomavirus E6 and E7 oncogenes. We suggest that activation of Notch signaling may serve as an additional mechanism to inhibit wild-type p53 function in papillomavirus-associated neoplasia.

Genetic alterations in the coding region of the bak gene in uterine cervical carcinoma

A significant frequency of mutations (six missense and one silent) was found, for the first time, at the coding region of the bak gene (exons 3, 4 and 6) in 42 carcinomas of the uterine cervix, while no mutations were detected in 32 non-neoplastic cervix tissues. Bak mutations were observed more frequently in the advanced stage and mutated cancer tissues were more resistant to radiotherapy, although trends were not statistically significant because of small sample size.

NF-kappaB is constitutively activated in high-grade squamous intraepithelial lesions and squamous cell carcinomas of the human uterine cervix

We demonstrate, for the first time, that the transcription factor NF-kappaB is constitutively activated during human cervical cancer progression. Immunohistochemical analysis was done using 106 paraffin-embedded cervical tissue specimens of different histological grades. In normal cervical tissue and low-grade squamous intraepithelial lesions, p50, RelA and IkappaB-alpha were mainly localized in the cytosol, whereas in high-grade lesions and squamous cell carcinomas, p50-RelA heterodimers translocated into the nucleus with a concurrent decrease in IkappaB-alpha protein. By Western blot analysis, p50 and RelA were detectable mainly in the cytosolic and nuclear extracts in normal and cancer tissues, respectively, and cytosolic IkappaB-alpha expression was detectable in normal but not in cancer cervical tissues. NF-kappaB DNA-binding activity increased during cervical cancer progression and the binding complex was mainly composed of the p50-RelA heterodimers as revealed by electrophoretic mobility shift assays. Semiquantitative RT-PCR analysis, however, showed increased levels of IkappaB-alpha mRNA in cancer samples presumably because of feedback regulation as a result of enhanced NF-kappaB DNA-binding activity and a consequent functional activation of NF-kappaB. Further immunohistochemical analysis with an antibody to phospho IkappaB-alpha revealed that phosphorylation occurs mainly in squamous intraepithelial lesions, suggesting that the IkappaB-alpha gets phosphorylated initially and degraded as the tumor progressed.

The role of human papillomavirus oncoproteins E6 and E7 in apoptosis

The oncogenic potential of 'high risk' human papillomaviruses can be mainly attributed to two small proteins called E6 and E7. Even these oncoproteins have a low molecular size, they are highly promiscuous and are capable to interact with a whole variety of host cellular regulator proteins to elicit cellular immortalization and ultimately complete malignant transformation. To avoid reiterations in summarizing the biochemical and molecular biological properties of E6/E7 in terms of their influence on cell cycle control, the present review is mainly an attempt to describe some regulatory principles by which human papillomavirus (HPV) oncoproteins can interfere with apoptosis in order to escape immunological surveillance during progression to cervical cancer. The models derived from these basic cellular and molecular studies are relevant to our understanding of HPV-induced carcinogenesis. Conversely, experimental procedures aimed at relieving apoptosis resistance, can facilitate the eradication of immunologically suspicious cells and may prevent the accumulation of cervical intraepithelial cell abnormalities in future prophylactic or therapeutic approaches.

Human papillomavirus type 16 E6 and E7 gene variations in Indian cervical cancer

OBJECTIVES

Human papillomavirus type 16 is a causative factor for development of cervical cancer. The E6 and E7 genes of HPV 16 are critical to the process of immortalization and transformation of host cells. Recent reports suggest that variants of these two genes may contribute to the risk of malignant progression of cancer in the uterine cervix. However, no data exist on sequence variations of HPV 16 E6 and E7 genes that may exist in India. Therefore, we examined intratype variations in the E6 and E7 viral genes in DNA isolated from HPV 16-positive cervical scrapes and biopsies.

METHODS

The open reading frames of the E6 and E7 genes were amplified by PCR and then directly sequenced by the fluorescent dye dideoxy termination method.Results. In addition to the prototype E6 gene sequence, five sets of mutations of the E6 gene were identified. The European prototype (350T) was detected in 9.1% of the study group while the European variant (350G) was seen in 28% of patients. The remaining variants (a combination of the 350G mutation with 335T, 145T, or 419G) were significantly associated with cases compared to controls. The 350G + 145T variant was found at much higher incidence in cases in younger women, suggesting that this variant may be associated with aggressive tumor behavior. Interestingly the 350G + 419G combination was found only in controls. There was no significant association between the four genotypes of E7 and any stage of tumor progression or age.

CONCLUSIONS

The results indicate that specific mutations in the E6 gene are found in young Indian women with high-grade squamous intraepithelial lesions and invasive cancer, suggesting that these mutations represent more oncogenically active HPV 16. Whether this increased oncogenecity is due to differences in p53 inactivation, ineffective keratinocyte differentiation, and/or altered response to the immune system by these oncogenic E6 mutants remains to be clarified.

Evidence of an association between human papillomavirus and impaired chemotherapy-induced apoptosis in cervical cancer cells

OBJECTIVES

The aim of this study was to determine cervical cancer cell sensitivity to chemotherapy-induced apoptosis based on human papillomavirus (HPV) status.

METHODS

CaSki (HPV-positive) and C33A (HPV-negative) cells were treated with camptothecin or cisplatin. Cellular viability was determined by trypan blue exclusion. Apoptotic indexes were determined by flow cytometric analysis of annexin V labeling and morphological changes. Mitochondrial release of cytochrome c was determined by immunofluorescence using confocal microscopy. Caspase 3 activation and bax expression were assessed by immunoblotting.

RESULTS

CaSki cells displayed chemoresistance to both camptothecin and cisplatin. Low response to apoptogenic stimuli was evidenced by a marginal increase in the apoptotic cell fraction after camptothecin treatment (22.9 +/- 2.56%) compared with control (17.8 +/- 1.95%). Cisplatin (14.8 +/- 1.01%) caused a slight decrease in apoptosis. Mitochondrial release of cytochrome c and cleavage of caspase 3 could not be demonstrated in CaSki cells after treatment. Despite p53 mutation, C33A cells were sensitive to the antiproliferative effects of camptothecin and cisplatin. Mean apoptotic events were 17.5 +/- 0.33 for control, 42 +/- 1.76 for cisplatin, and 38.1 +/- 0.75 for camptothecin. An intact cytochrome c pathway was demonstrated in C33A cells leading to cleavage of caspase 3 after camptothecin treatment. The constitutive bax expression demonstrated in both cell lines displayed no change after camptothecin treatment.

CONCLUSION

HPV-positive cervical cancer cells have an inherent resistance to chemotherapy-induced apoptosis. HPV-dependant inactivation of apoptotic regulators such as p53 and blockage of downstream events such as cytochrome c release and caspase 3 activation might be elemental to this cellular survival advantage provided by high-risk oncogenic papillomavirus.

Cellular manifestations of human papillomavirus infection in laryngeal tissues

BACKGROUND AND OBJECTIVES

Although epidemiologic studies have suggested human papillomavirus (HPV) to be an etiological agent in laryngeal carcinogenesis, little is known on the cellular manifestations of HPV infection in these tumors. In this study, we investigated the frequency of HPV infection in various neoplastic and non-neoplastic laryngeal tissue and its association with expression of the proliferating cell nuclear antigen (PCNA) and the tumor suppressor protein p53.

METHODS

Tissues were analyzed by polymerase chain reaction (PCR) for the presence of HPV and by immunocytochemistry for the expression of p53 and PCNA.

RESULTS

None of the six normal laryngeal tissues showed the presence of HPV. Thirteen out of the 16 papillomas were positive for HPV, while 15 out of the 44 invasive cancers were HPV positive. PCNA expression increased as the lesion progressed through increasing histological abnormality (r = 0.64400, P = 0.00000). The correlation between the type of laryngeal neoplasm and p53 accumulation was significant (r = 0.54839, P = 0.00000). Significant correlation was also evident between presence of HPV and p53 accumulation (r = 0.34259, P = 0.00424) and PCNA expression (r = 0.036024, P = 0.00266) indicating that HPV positive tumors showed significant p53 accumulation and increased proliferation. There was also correlation between p53 and PCNA expression (r = 0.67475, P = 0.00000) indicating that in all tumors with p53 accumulation, there was a corresponding increase in PCNA expression.

CONCLUSIONS

The results suggests that changes in p53 and PCNA expression may be associated with HPV infection, and could play a role in laryngeal carcinogenesis.

Restoration of p53 expression sensitizes human papillomavirus type 16 immortalized human keratinocytes to CD95-mediated apoptosis

To understand the function of the individual oncogenes of HPV16 in modulating the cellular response to apoptogenic signals, we used human keratinocytes immortalized with either E6, E7 or E6/E7 oncoproteins as model system. Applying CD95 antibodies or recombinant CD95 ligand, only the E7-immortalized cells underwent extensive apoptosis. In contrast, E6- and E6/E7-expressing keratinocytes were resistant. Dominance of E6 correlated with significant down-regulation of p53, c-Myc, p21 and Bcl-2. CD95 was found to be reduced in resistant HPV-positive cells, while there were no quantitative differences in expression levels of FADD, FLICE/caspase-8 or caspase-3. Notably, in contrast to primary human keratinocytes, all immortalized cells showed a general reduction of c-FLIP, an inhibitory protein which normally prevents unscheduled CD95-induced apoptosis. E6- and E6/E7-positive keratinocytes, however, can be sensitized to CD95 apoptosis by blocking proteasome-mediated proteolysis. CD95-resistant HPV-positive cells underwent apoptosis within 3-5 h upon co-incubation with MG132 and agonistic antibodies or CD95 ligand, which was preceded by a strong re-expression of p53 and c-Myc, but not of other half-life controlled proteins such as Bax or IkappaBalpha. Blockage of proteasomal activity alone did not result in apoptosis, although the same set of pro-apoptotic proteins was up-regulated. Performing similar experiments with cervical carcinoma cells expressing mutated p53 (C33a) or with p53-'null' lung carcinoma cells (H1299), no CD95 cell killing occurred even though c-Myc was strongly induced. These data indicate that the reduced bioavailability of p53 is a key-regulatory event in perturbation of CD95 signaling in HPV16 immortalized keratinocytes.

Steroid-mediated inhibition of radiation-induced apoptosis in C4-1 cervical carcinoma cells is p53-dependent

In human papillomavirus (HPV) infected cervical epithelial cells the synthetic steroid dexamethasone inhibits radiation-induced apoptosis and increases the transcription of HPV E6/E7, enhancing p53 degradation. The aim of this study was to determine if suppression of apoptosis was mechanistically linked to changes in p53. HPV 16 E6 or E6/E7 expression vectors were transiently transfected into C4-1 HPV 18-positive cervical carcinoma cells to mimic the enhanced transcription following steroid treatment. After irradiation, apoptosis was suppressed in these cells comparable to the effect observed after steroid treatment alone. To confirm whether loss of p53 was responsible for the inhibition of apoptosis, residual p53 in C4-1 cells was targeted by stable transfection with a dominant-negative p53 mutant. While radiation-induced apoptosis increased after mutant transfection, inhibition of programmed cell death by steroid treatment was either eliminated or substantially reduced. Steroid-dependent inhibition of radiation-induced apoptosis in carcinoma of the cervix involves E6 modulation of p53 expression and may adversely affect treatment.

Dendritic cells induce the death of human papillomavirus-transformed keratinocytes

Although human papillomavirus (HPV) antigens are expressed in a majority of (pre)neoplastic lesions (squamous intraepithelial lesions; SILs) of the uterine cervix, progression to invasive cancer may occur, which suggests that the presentation of viral antigens to the immune system is deficient in some SILs. To determine whether professional antigen-presenting cells die in SILs, we assayed for the apoptosis of immature dendritic cells (DC) in organotypic cultures of HPV-transformed keratinocytes, which reproduce many features of in vivo observed SILs. Unexpectedly, the infiltration of organotypic cultures by DC specifically induced the apoptosis of HPV+ tumor cells, whereas DC were not affected. In the same conditions and in coculture experiments, apoptosis was not observed in normal keratinocytes. The induction of apoptosis required membrane contacts between DC and HPV-transformed keratinocytes. Although the HPV+cell lines were sensitive to the effects of TRAIL, soluble TRAILR2-Fc did not block the DC-induced apoptosis. Furthermore, although FasL and Fas were detected on DC and HPV+ cell lines, respectively, functional analysis revealed that this pathway is not responsible for the apoptosis induced by the DC. All together these results suggest that DC may be at the interface between innate and adaptive immunity by inducing the apoptosis of (pre)neoplastic cells.

Human papillomavirus infections: epidemiology, pathogenesis, and therapy

BACKGROUND

Human papillomaviruses (HPV) are common human pathogens and are classified into more than 80 different types. These viruses produce benign warts in many cases and aggressive squamous cell carcinomas in other cases.

OBJECTIVE

The goal of this review is to update the reader on the epidemiology, pathogenesis, and therapy of HPV infections. Nonanogenital warts are transmitted by skin-to-skin contact while anogenital warts are usually transmitted sexually. Both types of warts produce much morbidity but rarely undergo malignant transformation. They are commonly treated with surgical or cytodestructive therapy, but immunomodulatory agents, such as imiquimod, have been proven to be very effective in anogenital warts and are being evaluated in nonanogenital warts. Other types of HPV have marked oncogenic potential such that over 99% of all cervical cancers and over 50% of other anogenital cancers are due to infection with oncogenic HPV. Many cofactors, such as cigarette smoking, genetics, and helper viruses, have potential roles in HPV oncogenesis, but their relative contributions are poorly understood. Other control measures for warts and HPV-associated cancers are under study, but the greatest future potential may be from the development of prophylactic and therapeutic vaccines.

CONCLUSIONS

Infection with HPV is very prevalent as are the clinical manifestations of this family of pathogens. Improved therapies for warts (e.g., imiquimod) have recently become available. Vaccines for HPV offer hope for future interventions for warts as well as for prevention of anogenital malignancies.

Oestrogen and progesterone increase the levels of apoptosis induced by the human papillomavirus type 16 E2 and E7 proteins

Human papillomavirus (HPV) type 16 infects the genital tract and is generally acknowledged to be a causative agent of cervical cancer. HPV infection alone is not sufficient to induce cervical cancer and other factors such as steroid hormones are thought to play a role in the establishment and/or progression of this disease. The HPV-16 E2 protein is required for virus replication and modulates viral gene expression whereas the HPV-16 E7 protein is required for cell transformation. We and others have shown that both the E2 and E7 proteins can induce apoptotic cell death in HPV-transformed and non-HPV transformed cell lines. Here we show that the steroid hormones oestrogen and progesterone can both increase the levels of E2- and E7-induced apoptosis. The oestrogen metabolite 16 alpha-hydroxyoestrone also increases E2- and E7-induced cell death and the dietary component indole-3-carbinol, which reduces the formation of 16alpha-hydroxyoestrone from oestrogen, blocks the effects of oestrogen. Thus the metabolism of oestrogen to 16 alpha-hydroxyoestrone appears to be required for the effects of this hormone on E2- and E7-induced cell death. We also show that the oestrogen receptor antagonist 3-hydroxytamoxifen blocks the effects of oestrogen on E2- and E7-induced cell death, whereas the anti-progesterone RU486 blocks the effects of both progesterone and oestrogen. We discuss these results in terms of the origin and progression of cervical cancer.

Development of a condemned mucosa syndrome and pathogenesis of human papillomavirus-associated upper aerodigestive tract and uterine cervical tumors

High-risk human papillomaviruses (HPVs) have been shown to be involved in the pathogenesis of many squamous carcinomas, particularly those of the uterine cervix. A number of random studies have also reported association of high-risk HPV subtypes with cancers of the oral cavity, larynx, hypopharynx, and esophagus. The roles of other molecular factors involved during HPV infection in these tumors still remain unclear. Recent findings from our laboratories have suggested possible mechanisms associated with HPV-mediated carcinogenesis. Both p53 mutation-dependent and mutation-independent pathways may be associated with HPV-mediated carcinogenesis, the former mainly in upper aerodigestive tract tumors (UADT) and the latter in cervical tumors. In cervical tumors, inactivation of the p53 tumor suppressor protein by the E6 gene product of high-risk HPVs and mutation of the p53 gene in UADT is associated with alterations in the apoptotic regulatory bcl-2 and bax genes, leading to downregulation of programmed cell death (PCD) and increased cell proliferation. HPV infection is also associated with increased tissue angiogenesis and activation of telomerase. Altered kinetics of telomere fragments is evident in HPV-infected tissue. We therefore believe that the combined manifestations of all these factors may contribute to development of a "condemned mucosa syndrome" facilitating development UADT and cervical cancers. A distinct step in the pathogenesis of both types of tumors may only be in the mode of p53 inactivation, whereas all other events appear to be strongly correlated to the presence of HPV. The development and validation of such a molecular model has significant clinical priority. It can be used to identify target populations or individuals for intervention, to monitor effects of intervention, and to determine which individuals or groups are at increased risk of developing cancer.