Transforming growth factors beta 1 and 2 transcriptionally regulate human papillomavirus (HPV) type 16 early gene expression in HPV-immortalized human genital epithelial cells

The role of transforming growth factor β in cervical carcinogenesis

Human papillomavirus (HPV) is involved in virtually all cases of cervical cancer. However, HPV alone is not sufficient to cause malignant development. The effects of chronic inflammation and the interaction of immune components with the microenvironment infected with the high-risk HPV type (HR) may contribute to cancer development. Transforming growth factor β (TGFB) appears to play an important role in cervical carcinogenesis. Protein and mRNA levels of this cytokine gradually increase as normal tissue develops into malignant tissue and are closely related to the severity of HPV infection. At the onset of infection, TGFB can inhibit the proliferation of infected cells and viral amplification by inhibiting cell growth and downregulating the transcriptional activity of the long control region (LCR) of HPV, thereby reducing the expression of early genes. When infected cells progress to a malignant phenotype, the response to the cell growth inhibitory effect of TGFB1 is lost and the suppression of E6 and E7 expression decreases. Subsequently, TGFB1 expression is upregulated by high levels of E6 and E7 oncoproteins, leading to an increase in TGFB1 in the tumor microenvironment, where this molecule promotes epithelial-to-mesenchymal transition (EMT), cell motility, angiogenesis, and immunosuppression. This interaction between HPV oncoproteins and TGFB1 is an important mechanism promoting the development and progression of cervical cancer.

Haplotype Structures and Protein Levels of TGFB1 in HPV Infection and Cervical Lesion: A Case-Control Study

This study aimed to verify the role of TGFB1 variants (c.-1638G>A, c.-1347C>T, c.29C>T, and c.74G>C) in HPV infection susceptibility and cervical lesions development, and their impact on TGFB1 cervical and plasma levels. TGFB1 genotypes were assessed with PCR-RFLP and haplotypes were inferred for 190 HPV-uninfected and 161 HPV-infected women. TGFB1 levels were determined with immunofluorimetric assay. Case-control analyses were performed with logistic regression adjusted for possible confounders. Women carrying -1347TT or -1347CT+TT as well as those with 29CT, 29CC, or 29CT+CC were more likely to have HPV than -1347CC and 29TT carriers, respectively. Regarding haplotypes, the most frequent were *4 (GCTG) and *3 (GTCG). Women *4/*4 were less likely to have HPV than those with no *4 copy. Comparing the inheritance of *3 and *4, carriers of *3/*4 or *3/*3 were more susceptible to HPV than *4/*4. The TGFB1 plasma and cervical levels were higher in the infected patients. Plasma levels were also higher in infected women with low-grade lesions. HPV-infected patients carrying *3/Other and *3/Other+*3/*3 presented lower TGFB1 plasma levels than those with no copy of *3. TGFB1 variants could contribute to the comprehension of the TGFB1 role in HPV-caused cervical disease.

Immunology of HPV-mediated cervical cancer: current understanding

Human papilloma virus (HPV) has emerged as a primary cause of cervical cancer worldwide. HPV is a relatively small (55 nm in diameter) and non-enveloped virus containing approximately 8 kb long double stranded circular DNA genome. To date, 228 genotypes of HPV have been identified. Although all HPV infections do not lead to the development of malignancy of cervix, only persistent infection of high-risk types of HPV (mainly with HPV16 and HPV18) results in the disease. In addition, the immunity of the patients also acts as a key determinant in the carcinogenesis. Since, no HPV type specific medication is available for the patient suffering with cervical cancer, hence, a deep understanding of the disease etiology may be vital for developing an effective strategy for its prevention and management. From the immunological perspectives, the entire mechanisms of disease progression still remain unclear despite continuous efforts. In the present review, the recent developments in immunology of HPV-mediated cervix carcinoma were discussed. At the end, the prevention of disease using HPV type specific recombinant vaccines was also highlighted.

Multidisciplinary Approach to the Management and Treatment of Anal Dysplasia

The incidence of anal intraepithelial neoplasia (AIN) has been increasing over the years. AIN acts as a precursor lesion for anal squamous cell cancer. Factors leading to progression of AIN into malignancy are complex and involve grade of the lesion, human papillomavirus and HIV coinfection, as well as patient-related risk factors such as immunocompromised state and men who have sex with men. The multifaced aspects of this disease make its management challenging, as it involves several disciplines including pathology, primary care, infectious disease, and colorectal specialties. Each of these fields brings its own expertize to the management of AIN, and their collaborative, coordinated work culminates into best practice and optimized outcomes in the care of the AIN patient.

Polymorphisms in the TGFB1 signal peptide influence human papillomavirus infection and development of cervical lesions

The main purpose was to assess the effect of c.29C>T and c.74G>C polymorphisms in the TGFB1 signal peptide on HPV infection and development of cervical lesions. Cervical swabs and blood samples were obtained from 349 outpatient women, along with socio-demographic and sexual behavioral data. The study population was stratified by absence or presence of HPV DNA, as tested by PCR, as well as by lesion grade. TGFB1 signal peptide polymorphisms were genotyped using PCR-restriction fragment length polymorphism. HPV DNA was detected in 172 (49.3%) patients. c.74GC and the combined c.29CC+CT/c.74GC genotype were more frequent in infected patients (35.1 and 15.7%) than in uninfected women (6.2 and 14.7%). Accordingly, these genotypes were associated with a higher risk of HPV infection, with odds ratio and 95% confidence interval of 2.81 and 1.35-5.86 (P = 0.004) for c.74GC and 3.14 and 1.42-6.94 (P = 0.004) for the combined genotype, respectively. High-grade lesions were also 2.48 times more likely to occur in c.29CC patients than in c.29TT patients, with a 95% confidence interval of 1.01-6.08 (P = 0.047). The data demonstrate that c.74G>C and c.29C>T polymorphisms are significantly associated with risk of HPV infection and high-grade squamous intraepithelial lesions, respectively. Thus, TGFB1 signal peptide polymorphisms are potential susceptibility markers.

Induction of Interferon Kappa in Human Papillomavirus 16 Infection by Transforming Growth Factor Beta-Induced Promoter Demethylation

Persistent high-risk human papillomavirus (HPV) infection is the major causal factor in cervical and other anogenital cancers. Because there are currently no therapeutics capable of preventing neoplastic progression of HPV infections, understanding the mechanisms of HPV-mediated persistence, including immune evasion, is a major research priority. The multifunctional growth factor transforming growth factor beta (TGFβ) has been shown to inhibit expression of early viral transcripts from cells harboring integrated HPV genomes or cells infected with retroviruses expressing HPV oncoproteins. However, the mechanism of TGFβ-induced inhibition has not been fully defined. In this study, we have observed a previously uncharacterized ability of TGFβ to repress the differentiation-induced upregulation of late HPV16 gene expression. In addition, interferon kappa (IFN-κ), a keratinocyte-specific, constitutively expressed cytokine suppressed by differentiation, can be transcriptionally induced by TGFβ1. TGFβ-mediated IFN-κ transcription only occurs in cells containing HPV16, and this is due to TGFβ1-mediated reversal of HPV-induced methylation of the IFN-κ promoter through active DNA demethylation mediated by thymine DNA glycosylase (TDG). This novel interaction between growth factor and innate immune signaling may shed light on the mechanisms of HPV persistence and how the virus manipulates both immune and growth factor signaling to promote its life cycle.IMPORTANCE Persistent infection by high-risk HPVs is the primary risk factor for development of HPV-induced cancers. Persistence involves viral evasion of the immune response, including the IFN response. HPV is also known to suppress TGFβ signaling, which inhibits viral gene expression. Here, we show that the TGFβ and IFN pathways are interrelated in the context of HPV16 infection through the upregulation of IFN-κ by TGFβ. The ability of TGFβ to induce IFN-κ promoter demethylation and transcriptional activation provides a new explanation for why HPV has evolved mechanisms to inhibit TGFβ in infected cells.

The human papillomavirus E7 oncoprotein as a regulator of transcription

High-risk human papillomaviruses (HPVs) encode oncoproteins which manipulate gene expression patterns in the host keratinocytes to facilitate viral replication, regulate viral transcription, and promote immune evasion and persistence. In some cases, oncoprotein-induced changes in host cell behavior can cause progression to cancer, but a complete picture of the functions of the viral oncoproteins in the productive HPV life cycle remains elusive. E7 is the HPV-encoded factor most responsible for maintaining cell cycle competence in differentiating keratinocytes. Through interactions with dozens of host factors, E7 has an enormous impact on host gene expression patterns. In this review, we will examine the role of E7 specifically as a regulator of transcription. We will discuss mechanisms of regulation of cell cycle-related genes by E7 as well as genes involved in immune regulation, growth factor signaling, DNA damage responses, microRNAs, and others pathways. We will also discuss some unanswered questions about how transcriptional regulation by E7 impacts the biology of HPV in both benign and malignant conditions.

The Interaction Between Human Papillomaviruses and the Stromal Microenvironment

Human papillomaviruses (HPVs) are small, double-stranded DNA viruses that replicate in stratified squamous epithelia and cause a variety of malignancies. Current efforts in HPV biology are focused on understanding the virus-host interactions that enable HPV to persist for years or decades in the tissue. The importance of interactions between tumor cells and the stromal microenvironment has become increasingly apparent in recent years, but how stromal interactions impact the normal, benign life cycle of HPVs, or progression of lesions to cancer is less understood. Furthermore, how productively replicating HPV impacts cells in the stromal environment is also unclear. Here we bring together some of the relevant literature on keratinocyte-stromal interactions and their impacts on HPV biology, focusing on stromal fibroblasts, immune cells, and endothelial cells. We discuss how HPV oncogenes in infected cells manipulate other cells in their environment, and, conversely, how neighboring cells may impact the efficiency or course of HPV infection.

Transforming growth factor-β1 in carcinogenesis, progression, and therapy in cervical cancer

Transforming growth factor β1 (TGF-β1) is a multifunctional cytokine that plays important roles in cervical tumor formation, invasion, progression, and metastasis. TGF-β1 functions as a tumor inhibitor in precancerous lesions and early stage cancers of cervix whereas as a tumor promoter in later stage. This switch from a tumor inhibitor to a tumor promoter might be due to various alterations in TGF-β signaling pathway, such as mutations or loss of expression of TGF-β receptors and SMAD proteins. Additionally, the oncoproteins of human papillomaviruses have been shown to stimulate TGF-β1 expression, which in turn suppresses host immune surveillance. Thus, in addition to driving tumor cell migration and metastasis, TGF-β1 is believed to play a key role in promoting human papillomavirus infection by weakening host immune defense. In this article, we will discuss the role of TGF-β1 in the expression, carcinogenesis, progression, and therapy in cervical cancers. A better understanding of this cytokine in cervical carcinogenesis is essential for critical evaluation of this cytokine as a potential prognostic marker and therapeutic target.

Early Defensive Mechanisms against Human Papillomavirus Infection

Cervical cancer is the fourth most common cancer in women and is almost exclusively caused by human papillomavirus (HPV) infection. HPV is also frequently associated with other cancers arising from mucosal epithelium, including anal and oropharyngeal cancers, which are becoming more common in both men and women. Viral persistence and progression through precancerous lesion stages are prerequisites for HPV-associated cancer and reflect the inability of cell-mediated immune mechanisms to clear infections and eliminate abnormal cells in some individuals. Cell-mediated immune responses are initiated by innate pathogen sensing and subsequent secretion of soluble immune mediators and amplified by the recruitment and activation of effector T lymphocytes. This review discusses early defensive mechanisms of innate responders to natural HPV infection, their influence on response polarization, and the underappreciated role of keratinocytes in this process.

Curcumin and emodin down-regulate TGF-β signaling pathway in human cervical cancer cells

Cervical cancer is the major cause of cancer related deaths in women, especially in developing countries and Human Papilloma Virus infection in conjunction with multiple deregulated signaling pathways leads to cervical carcinogenesis. TGF-β signaling in later stages of cancer is known to induce epithelial to mesenchymal transition promoting tumor growth. Phytochemicals, curcumin and emodin, are effective as chemopreventive and chemotherapeutic compounds against several cancers including cervical cancer. The main objective of this work was to study the effect of curcumin and emodin on TGF-β signaling pathway and its functional relevance to growth, migration and invasion in two cervical cancer cell lines, SiHa and HeLa. Since TGF-β and Wnt/β-catenin signaling pathways are known to cross talk having common downstream targets, we analyzed the effect of TGF-β on β-catenin (an important player in Wnt/β-catenin signaling) and also studied whether curcumin and emodin modulate them. We observed that curcumin and emodin effectively down regulate TGF-β signaling pathway by decreasing the expression of TGF-β Receptor II, P-Smad3 and Smad4, and also counterbalance the tumorigenic effects of TGF-β by inhibiting the TGF-β-induced migration and invasion. Expression of downstream effectors of TGF-β signaling pathway, cyclinD1, p21 and Pin1, was inhibited along with the down regulation of key mesenchymal markers (Snail and Slug) upon curcumin and emodin treatment. Curcumin and emodin were also found to synergistically inhibit cell population and migration in SiHa and HeLa cells. Moreover, we found that TGF-β activates Wnt/β-catenin signaling pathway in HeLa cells, and curcumin and emodin down regulate the pathway by inhibiting β-catenin. Taken together our data provide a mechanistic basis for the use of curcumin and emodin in the treatment of cervical cancer.

Interaction between Chronic Inflammation and Oral HPV Infection in the Etiology of Head and Neck Cancers

Incidences of oral tongue, base of the tongue, and tonsil cancers have been increasing steadily in many parts of the world in spite of declining rates of tobacco use over the last four decades. A better understanding of the etiology, interactions between risk factors, and new approaches to prevention and treatment are necessary to change this course. This paper will present evidence supporting a potential role of chronic inflammation in the etiologies of oral human papillomavirus infection and head and neck squamous cell carcinoma, and it will discuss the implications for prevention and treatment.

Inhibition of the epidermal growth factor receptor by erlotinib prevents immortalization of human cervical cells by Human Papillomavirus type 16

The Human Papillomavirus type-16 (HPV-16) E6 and E7 oncogenes are selectively retained and expressed in cervical carcinomas, and expression of E6 and E7 is sufficient to immortalize human cervical epithelial cells. Expression of the epidermal growth factor receptor (EGFR) is often increased in cervical dysplasia and carcinoma, and HPV oncoproteins stimulate cell growth via the EGFR pathway. We found that erlotinib, a specific inhibitor of EGFR tyrosine kinase activity, prevented immortalization of cultured human cervical epithelial cells by the complete HPV-16 genome or the E6/E7 oncogenes. Erlotinib stimulated apoptosis in cells that expressed HPV-16 E6/E7 proteins and induced senescence in a subpopulation of cells that did not undergo apoptosis. Since immortalization by HPV E6/E7 is an important early event in cervical carcinogenesis, the EGFR is a potential target for chemoprevention or therapy in women who have a high risk for cervical cancer.

The role of inflammation in HPV carcinogenesis

The role of inflammation in human papillomavirus (HPV) infection and disease is complex since it involves responses capable of preventing initial infections, clearing those ongoing as well as promoting persistence and progression of associated lesions. Avoiding the immune response has been considered a key aspect of HPV persistence which is the main factor leading to HPV-related neoplasia. HPVs have evolved different ways of targeting immune signaling pathways. Moreover, host inflammatory response may promote lesion progression and affect tumor fate by diverse mechanisms including the direct participation of inflammatory cells. In this review, we discuss the interplay between HPV oncogenic proteins and an array of inflammatory responses that ultimately may lead to cancer.

Interferon regulatory factor (IRF)-2 activates the HPV-16 E6-E7 promoter in keratinocytes

Interferon regulatory factors (IRFs) are critical mediators of gene expression, cell growth and immune responses. We previously demonstrated that interferon (IFN) induction of early viral transcription and replication in several mucosal HPVs requires IRF-1 binding to a conserved interferon response element (IRE). Here we show that the IRF-2 protein serves as a baseline transactivator of the HPV-16 major early promoter, P97. Cotransfections in IRF knockout cells confirmed that basal HPV-16 promoter activity was supported by both IRF-1 and IRF-2 complexes interacting with the promoter-proximal IRE in a dose-dependent manner. Furthermore, HPV-16 E7 expression downregulates the IRF-2 promoter, thus linking IRF-2 levels to viral transforming gene expression through a negative feedback mechanism. Taken together, these observations reveal a complex viral strategy utilizing multiple signal transduction pathways during the establishment and maintenance of HPV persistence.

Epithelial raft cultures for investigations of virus growth, pathogenesis and efficacy of antiviral agents

The organotypic epithelial raft cultures, originally developed to study keratinocytes differentiation, represent a novel approach to the study of viruses able to infect epithelial cells. Organotypic epithelial raft cultures accurately reproduce the process of epithelial differentiation in vitro and can be prepared from normal keratinocytes, explanted epithelial tissue, or established cell lines. This culture system permits cells to proliferate and fully differentiate at the air-liquid interface on a dermal-equivalent support. Normal primary human keratinocytes (PHKs) stratify and fully differentiate in a manner similar to the normal squamous epithelial tissues, while transformed cell lines exhibit dysplastic morphologies similar to the (pre)neoplastic lesions seen in vivo. This three-dimensional (3D) culture system provides an essential tool for investigations of virus growth, virus-host cell interactions, for the genetic analysis of viral proteins and regulatory sequences, and for the evaluation of antiviral agents. The 3D epithelial cultures have proven a breakthrough in the research on papillomaviruses, since their life cycle is strictly linked to the differentiation of the host epithelium. In the last years, several reports have shown the usefulness of the 3D epithelial cultures for the study of other viruses that target at least during a part of their life cycles epithelial cells. The 3D epithelial cultures allow the analysis of virus-host cell interactions in stratified epithelia that more closely resemble the in vivo situation. In this review we describe the advances on research on 3D epithelial cultures for the study of virus growth and pathogenesis of different families of viruses, including papilloma-, herpes-, pox-, adeno-, and parvoviruses.

Oncogenic activities of human papillomaviruses

Infectious etiologies for certain human cancers have long been suggested by epidemiological studies and studies with experimental animals. Important support for this concept came from the discovery by Harald zur Hausen's group that human cervical carcinoma almost universally contains certain "high-risk" human papillomavirus (HPV) types. Over the years, much has been learned about the carcinogenic activities of high-risk HPVs. These studies have revealed that two viral proteins, E6 and E7, that are consistently expressed in HPV-associated carcinomas, are necessary for induction and maintenance of the transformed phenotype. Hence, HPV-associated tumors are unique amongst human solid tumors in that they are universally caused by exposure to the same, molecularly defined oncogenic agents, and the molecular signal transduction pathways subverted by these viral transforming agents are frequently disrupted in other, non-virus-associated human cancers.

Integration of high-risk human papillomavirus: a key event in cervical carcinogenesis?

An important occurrence in cervical carcinogenesis is deregulated expression of the high-risk human papillomavirus (HR-HPV) oncogenes E6 and E7. Several risk factors for cervical neoplastic progression are likely to contribute to viral oncogene deregulation, particularly integration of HR-HPV into the host genome. Integration represents a by-product of viral infection that is detected in almost 90% of cervical carcinomas. The mechanism of integration is not fully understood, although there is a clear predilection for chromosomal common fragile sites, most likely due to their accessibility for insertion of foreign DNA. Recent work has suggested that an important intermediate stage in cervical carcinogenesis is characterized by transcriptionally silent HR-HPV integrants, which co-exist with viral episomes in infected cells. As episome-derived E2 protein inhibits integrant transcription, clearance of episomes (eg by host innate immunity) is associated with loss of integrant silencing and integrant selection. The process of integration and subsequent clonal selection of integrants can therefore be considered as two independent and biologically distinct events. Indeed, integrated HPV may be viewed as selectable because it represents a form of the virus that is resistant to host mechanisms of viral clearance, enabling infected cells to maintain viral oncogene expression and avoid cell death. Care should be taken in interpreting studies of HPV integration frequency in clinical samples, as the techniques used have assessed either the presence of integrated viral DNA or evidence of transcriptional activity from integrants, but not both.

Id-1 modulates senescence and TGF-beta1 sensitivity in prostate epithelial cells

BACKGROUND INFORMATION

Loss of sensitivity to TGF-beta1 (transforming growth factor beta1)-induced growth arrest is an important step towards malignant transformation in human epithelial cells, and Id-1 (inhibitor of differentiation or DNA binding-1) has been associated with cell proliferation and cell-cycle progression. Here, we investigated the role of Id-1 in cellular sensitivity to TGF-beta1.

RESULTS

Using an immortalized prostate epithelial cell line, NPTX cells, we suppressed Id-1 expression through antisense strategy. We found that inhibition of Id-1 expression suppressed cell proliferation and at the same time induced cellular senescence and G2/M cell-cycle arrest. In addition, inactivation of Id-1 made cells more vulnerable to TGF-beta1-induced growth arrest. The sensitization effect on TGF-beta1 was associated with up-regulation of two downstream effectors of the TGF-beta1 pathway, p21WAF1/Cip1 and p27KIP1.

CONCLUSION

Our results indicate that endogenous Id-1 levels might be a crucial factor in the development of resistance to TGF-beta1-induced growth suppression in human prostate epithelial cells.

Glucocorticoids regulate tristetraprolin synthesis and posttranscriptionally regulate tumor necrosis factor alpha inflammatory signaling

Glucocorticoids are used to treat various inflammatory disorders, but the mechanisms underlying these actions are incompletely understood. The zinc finger protein tristetraprolin (TTP) destabilizes several proinflammatory cytokine mRNAs by binding to AU-rich elements within their 3' untranslated regions, targeting them for degradation. Here we report that glucocorticoids induce the synthesis of TTP mRNA and protein in A549 lung epithelial cells and in rat tissues. Dexamethasone treatment leads to a sustained induction of TTP mRNA expression that is abrogated by RU486. Glucocorticoid induction of TTP mRNA is also blocked by actinomycin D but not by cycloheximide, suggesting a transcriptional mechanism which has been confirmed by transcription run-on experiments. The most widely characterized TTP-regulated gene is the AU-rich tumor necrosis factor alpha (TNF-alpha) gene. Dexamethasone represses TNF-alpha mRNA in A549 cells and decreases luciferase expression of a TNF-alpha 3' untranslated region reporter plasmid in an orientation-dependent manner. Small interfering RNAs to TTP significantly prevent this effect, and a cell line stably expressing a short-hairpin RNA to TTP conclusively establishes that TTP is critical for dexamethasone inhibition of TNF-alpha mRNA expression. These studies provide the molecular evidence for glucocorticoid regulation of human TTP and reflect a novel inductive anti-inflammatory signaling pathway for glucocorticoids that acts via posttranscriptional mechanisms.

Biology of HPV in HIV infection

HIV-positive men and women are at increased risk of anogenital and oral HPV infection. The risks for HPV-associated high-grade intra-epithelial neoplasia (IN) and cancer are also increased. The prevalence of oral, anal, and cervical HPV infection in HIV-positive individuals compared with HIV-negative individuals increases with progressively lower CD4+ levels, as does incident high-grade IN. In contrast to IN, development of cancer is not related to lower CD4+ level. With increasing grades of IN and cancer, the proportion of tissues with copy-number abnormalities (CNA) increases, with one of the most common genetic changes being amplification of chromosome 3q. The presence of CNA is associated with the integration of HPV DNA into the host genome, with loss of HPV E2 and/or E2 rearrangement. This suggests a link between CNA and increased HPV-induced chromosomal instability mediated through de-repressed E6 and E7 expression consequent to loss of functional E2 protein. In addition, epigenetic changes occur with increasing frequency in high-grade IN and cancer, such as hypermethylation leading to down-regulation of potential tumor suppressor genes. Analysis of these data together suggests that immune suppression plays a more prominent role in the earlier stages of HPV-associated disease, up to and including incident high-grade IN. Persistent high-grade IN and development of cancer may be more strongly related to the cumulative effect of HPV-associated genetic instability and the resulting host genetic changes. There are few data to suggest a direct role for HIV in the pathogenesis of HPV-associated neoplasia, but HIV-associated attenuation of HPV-specific immune responses may allow for persistence of high-grade IN and sufficient time for accumulation of genetic changes that are important in progression to cancer.

A cell-based high-throughput assay for screening inhibitors of human papillomavirus-16 long control region activity

Cervical carcinomas express human papillomavirus (HPV) E6 and E7 oncoproteins, which are required to maintain the proliferative state of cancer cells. Repression of E6 and E7 expression results in acquisition of senescent phenotype and in the rescue of functional p53 and p105(Rb) pathways; therefore, therapies directed against either viral protein may be beneficial. However, the systems to study HPV in vitro are technically difficult and not convenient for screening of antiviral compounds. This has hampered the discovery of drugs against HPV. Here we describe the generation and use of a high-throughput screening system based on keratinocytes stably transfected with a reporter construct containing the regulatory sequence of E6 and E7 gene transcription (LCR) that allows easy detection of inhibitors of E6 and E7 expression in libraries of synthetic or biological compounds. The assay was used to screen a wide panel of cytokines: among them, IL-4, IL-13, TGF-beta1, TGF-beta2, TGF-beta3, TNF-alpha, IFN-alpha, and IFN-beta were found to induce a strong inhibition of the LCR activity. Our assay provides a validated tool in the search for drugs against HPV-associated cervical carcinomas and allowed the first systematic analysis of the effect of cytokines on the HPV-16 LCR transcriptional activity.

Immune responses to human papillomavirus in genital tract of women with cervical cancer

OBJECTIVES

To address a question whether immune responses to HPV infection play a role in control of cervical cancer, we analyzed systemic and mucosal immune responses to HPV in women who underwent radical hysterectomy for cervical cancer (HCC) or loop conization due to cervical dysplasia (LOOP), or had hysterectomy for other reasons (HNN).

METHODS

HPV-specific antibodies in sera and vaginal washes were determined by ELISA using recombinant HPV 16 E7 oncoprotein. Cytokines in vaginal washes were assayed by Linco cytokine multiplex method using Luminex technology. Differential gene expression profiling in cervical tumor was determined by microarray analysis and Real-time RT-PCR.

RESULTS

While levels of HPV-16 E7-specific IgG in vaginal wash were significantly higher in women undergoing HCC and HNN, the levels of the HPV-16 E7-specific IgA in vaginal wash of women with cervical cancer and cervical dysplasia were lower as compared to patients in HNN. Proinflammatory cytokines, such as IL-6 and IL-8, were dominant in vaginal washes of all subjects studied. However, no pattern of Th1-type and Th2-type cytokine induction was observed as demonstrated by protein analysis as well as differential gene expression profiling in cervical tumor.

CONCLUSIONS

These results suggest a selective down-regulation of local HPV-specific IgA responses in women with cervical cancer.

NFI-Ski interactions mediate transforming growth factor beta modulation of human papillomavirus type 16 early gene expression

Human papillomaviruses (HPVs) are present in virtually all cervical cancers. An important step in the development of malignant disease, including cervical cancer, involves a loss of sensitivity to transforming growth factor beta (TGF-beta). HPV type 16 (HPV16) early gene expression, including that of the E6 and E7 oncoprotein genes, is under the control of the upstream regulatory region (URR), and E6 and E7 expression in HPV16-immortalized human epithelial cells is inhibited at the transcriptional level by TGF-beta. While the URR contains a myriad of transcription factor binding sites, including seven binding sites for nuclear factor I (NFI), the specific sequences within the URR or the transcription factors responsible for TGF-beta modulation of the URR remain unknown. To identify potential transcription factors and binding sites involved in TGF-beta modulation of the URR, we performed DNase I footprint analysis on the HPV16 URR using nuclear extracts from TGF-beta-sensitive HPV16-immortalized human keratinocytes (HKc/HPV16) treated with and without TGF-beta. Differentially protected regions were found to be located around NFI binding sites. Electrophoretic mobility shift assays, using the NFI binding sites as probes, showed decreased binding upon TGF-beta treatment. This decrease in binding was not due to reduced NFI protein or NFI mRNA levels. Mutational analysis of individual and multiple NFI binding sites in the URR defined their role in TGF-beta sensitivity of the promoter. Overexpression of the NFI family members in HKc/HPV16 decreased the ability of TGF-beta to inhibit the URR. Since the oncoprotein Ski has been shown to interact with and increase the transcriptional activity of NFI and since cellular Ski levels are decreased by TGF-beta treatment, we explored the possibility that Ski may provide a link between TGF-beta signaling and NFI activity. Anti-NFI antibodies coimmunoprecipitated endogenous Ski in nuclear extracts from HKc/HPV16, confirming that NFI and Ski interact in these cells. Ski levels dramatically decreased upon TGF-beta treatment of HKc/HPV16, and overexpression of Ski eliminated the ability of TGF-beta to inhibit the URR. Based on these studies, we propose that TGF-beta inhibition of HPV16 early gene expression is mediated by a decrease in Ski levels, which in turn dramatically reduces NFI activity.

Decreased expression of human papillomavirus E2 protein and transforming growth factor-beta1 in human cervical neoplasia as an early marker in carcinogenesis

BACKGROUND AND OBJECTIVES

Human papillomavirus (HPV) is thought to be one of the possible causative factors in cervical carcinogenesis, and cervical carcinoma cells are refractory to tumor transforming growth factor (TGF)-beta1. The purpose of this study is to investigate the possible cause-effect association between HPV and TGF-beta1 during cervical tumorigenesis.

METHODS

We assessed the expression of HPV capsid proteins, HPV-16 E7, HPV-16 E2 (C and N terminals), TGF-beta1, and their receptors TGF-beta RI and RII by immunohistochemistry in 48 paraffin-embedded blocks of tumor tissue derived from patients of cervical neoplasia.

RESULTS

Expression of TGF-beta1 decreased as tumor cells progressed from cervical intraepithelial neoplasia (CIN)1, CIN2, CIN3, to microinvasive carcinoma (P < 0.05). Levels of TGF-betaRI and TGFbeta-RII stayed the same in all cases. HPV was found in 89.6% of the studied sections, and cervical lesions without HPV infection expressed significantly less TGF-beta1 (P < 0.05). By comparing the expression pattern of TGF-beta1 and HPV in the neoplastic cells with that of normal cervical epithelium in each section, we found loss of HPV-16 E2 higher in CIN3 (15/24) than in CIN1 or CIN2 (3/7), and there is a significant trend that loss of HPV-16 E2 expression correlated with a >50% loss of TGF-beta1 at the lesion site (P < 0.05).

CONCLUSIONS

Our result showed co-suppression of HPV and TGF-beta1 expression during progression of cervical squamous cell cancer. Using antibody against HPV-16 E2 may be an auxiliary tool for the investigation of cervical tumor progression.

A functional interferon regulatory factor-1 (IRF-1)-binding site in the upstream regulatory region (URR) of human papillomavirus type 16

We recently identified a new enhancer element (HIRE-1, HPV-Interferon Responsive Element-1) in the upstream regulatory region (URR) of human papillomavirus (HPV) type 16. HIRE-1 is located upstream from and in close proximity to the TATA box. HIRE-1 is 1 nt shorter in its 5' sequence in comparison to a consensus IRF-1 binding site (IRF-E). Gel shift analyses clearly demonstrated that HIRE-1 is capable of binding IRF-1 in response to interferon-gamma (IFN-gamma) treatment. In a reporter system, HIRE-1 stimulated transcription in response to IRF-1 or IFN gamma from both a heterologous or the homologous (p97) promoter in a dose-dependent manner. Mutations in the core binding sequence strongly decreased this enhancer activity. Interestingly, HIRE-1 stimulated transcription in the context of the full URR in a cell-type-specific manner, thereby suggesting the role of other cell-type-specific factors that might counteract with its function. Thus, our results may explain the inconsistent clinical and experimental results observed following IFN treatment of cervical lesions or cells. Also, this new enhancer may have an important function during inflammatory responses against HPV type 16.

Papillomaviruses and cancer: from basic studies to clinical application

Links between human papillomaviruses (HPVs) and cervical cancer were first suspected almost 30 years ago. DNA of specific HPV types has since been found in almost all cervical cancer biopsies. HPV oncogenes that are expressed in these cells are involved in their transformation and immortalization, and are required for the progression towards malignancy. Epidemiological studies have underlined that HPVs are the main aetiological factor for cervical cancer. But how has this knowledge been translated into the clinic to allow the prevention, screening and treatment of cervical cancer?

Cytokines in cervicovaginal washing fluid from patients with cervical neoplasia

Human papillomavirus (HPV) infections play an important role in the development of cervical neoplasia. To get to a better understanding of the role of cytokines in the development of these neoplasias, we analysed the presence of various cytokines in cervicovaginal washings of healthy volunteers (n=22), cervical intraepithelial neoplasia (CIN) patients (n=63) and cervical cancer patients (n=33). IL-12p40, IL-10, TGF-beta1, TNF-alpha and IL-1beta levels were significantly higher in patients with cervical cancer than in controls and CIN patients. The levels of IFN-gamma were not different. Our data demonstrate alterations in the local cervical immune environment in cervical cancer patients. This could have important consequences for the further development of immune modulating therapies and vaccination strategies.

Surrogate endpoint biomarkers and their modulation in cervical chemoprevention trials

BACKGROUND

Surrogate endpoint biomarkers (SEBs) are used as intermediate indicators of a reduction in cancer incidence in chemoprevention studies. SEBs should be expressed differentially in normal and high risk tissue; appear at a well defined stage of carcinogenesis; be studied with reasonable sensitivity, specificity, and accuracy; and be modulated in chemoprevention trials. The concept of SEBs may be useful in the trials of many new therapies.

METHODS

The current review includes a comprehensive review of the literature. Many SEBs have been the subject of intense study and include quantitative histopathology and cytology, proliferation markers, regulation markers, differentiation markers, general genomic instability markers, and tissue maintenance markers. Because of the critical biologic and epidemiologic role of the human papillomavirus (HPV) in cervical carcinogenesis, the relation between these markers and HPV should be considered. In addition, biomarkers of HPV infection and its regression should be sought.

RESULTS

Several chemoprevention trials have been published that have included the use of SEBs. The biomarkers that appear most promising in these clinical trials can be measured quantitatively and reproducibly: quantitative histology and cytology, proliferating cell nuclear antigen (PCNA), MIB-1, MPM-2, HPV viral load, epidermal growth factor receptor, polyamines, and ploidy. The markers that have been demonstrated to be modulated in chemoprevention trials in the literature are quantitative histology and cytology, PCNA, MPM-2, HPV viral load, and polyamines.

CONCLUSIONS

The surrogate endpoint biomarkers of most interest in future research should correlate well with HPV infection, be modulated by several therapeutic agents, and have limited variability and ease in measurement.

Chromosome 3p tumor-suppressor gene alterations in cervical carcinomas

Loss of heterozygosity (LOH) on chromosome 3p is a common event in cervical cancer and typically occurs in a dispersed pattern involving several loci. This implies that more than one resident tumor-suppressor gene is involved in the genesis of these tumors; however, specific targets remain to be identified. The region of 3p14.2-pter encompasses a region of frequent loss and contains at least three tumor-suppressor genes: fragile histidine triad (FHIT), transforming growth factor-beta receptor II (T beta R-II), and Von Hippel-Lindau. To identify those loci within 3p14.2-pter that are important in cervical cancer, invasive tumors were first subjected to high-density LOH analysis. With 25 microsatellite markers, LOH was detected in seven of 15 cervical carcinomas (47%). Losses always included markers mapping to 3p22, and markers at this location were exclusively lost in two tumors, implicating this as a site of a cervical tumor-suppressor gene. Because it is a known tumor-suppressor gene located at 3p22 and thus a potential target for inactivation in these tumors, the T beta R-II gene was subsequently screened for mutation and altered expression levels. Whereas no tumor-derived mutations were detected in any of the tumors, six of ten tumors showed T beta R-II transcript levels reduced by > or = 50% when compared with normal cervical epithelium. Nine of 15 (60%) tumors exhibited LOH at 3p22 or reduced expression of T beta R-II, suggesting that reduced T beta R-II levels contribute to cervical tumorigenesis. Two cases exhibited silent germline polymorphisms of T beta R-II: one corresponding to a C1167T transversion and the other to an A1266G transition. The FHIT gene, which is located at 3p14.2, also frequently incurred LOH and abnormal transcription in these tumors. LOH of FHIT was observed in five of the 15 tumors analyzed. Neither mutations nor homozygous deletions of FHIT were detected in the tumors. However, aberrantly short transcripts of the FHIT gene were evident in six of nine (67%) tumors. Only one of these also displayed LOH, indicating that this gene was altered in at least 10 of 15 (67%) tumors. These results provide evidence that the inactivation of two known tumor-suppressor genes, TbetaR-II and FHIT, on chromosome 3p is involved in cervical carcinogenesis. Mol. Carcinog. 30:159--168, 2001.

Decreased synthesis and expression of TGF-beta1, beta2, and beta3 in epithelium of HPV 16-positive cervical precancer: a study by microdissection, quantitative RT-PCR, and immunocytochemistry

Cervical carcinogenesis is a multistep process initiated by 'high-risk' human papillomaviruses (HR-HPVs), most commonly HPV 16. Transforming growth factor-beta (TGF-beta) inhibits epithelial proliferation and down-regulates transcription of E6/E7 genes of HPV. Altered TGF-beta expression may be important in carcinogenesis. Quantitative RT-PCR was used to investigate TGF-beta1, beta2, and beta3 mRNA levels in nine specimens of normal cervix and 15 cervical precancers (eight HPV-positive, including five HPV 16-positive). Immunocytochemical expression of TGF-beta1, beta2, and beta3 was examined in cervical intraepithelial neoplasia (CIN) positive for HPV 16 (26), and in HPV-negative, normal ectocervical epithelium (9); reserve cell hyperplasia (12); and immature (7) and mature (15) squamous metaplasia. The intensity of staining for TGF-beta1 was measured using grey-scale image analysis. Microdissection was used to investigate epithelial and stromal (excluding crypts) levels of TGF-beta1 mRNA in HPV 16-positive cervical precancer. Normal cervix, including reserve cells and immature and mature metaplasia, showed strong immunocytochemical expression of all TGF-beta isoforms. Expression was decreased in the basal third of the epithelium in CIN 1, in the basal and middle thirds in CIN 2, and in all layers in CIN 3. Quantitative analysis of TGF-beta1 expression showed that the changes in CIN compared with normal ectocervix and mature metaplasia were statistically highly significant (p<0.001, ANOVA). TGF-beta1, beta2, and beta3 mRNA levels showed a significant decrease only in the five HPV 16-positive CIN samples when compared with normal (p=0. 0034, 0.0033, and 0.029, respectively). TGF-beta mRNA levels in HPV 16-positive epithelium also decreased from normal through low-grade to high-grade precancer. Stromal TGF-beta1 was absent or very low compared with epithelial production and was not altered in HPV 16 precancer. Progressive loss of epithelial TGF-beta expression and synthesis may be important in HPV 16-associated human cervical carcinogenesis.

TGF-beta-mediated cell cycle arrest of HPV16-immortalized human ectocervical cells correlates with decreased E6/E7 mRNA and increased p53 and p21(WAF-1) expression

Transforming growth factor beta (TGF-beta) suppresses proliferation and potentiates apoptosis of HPV16-immortalized human cervical epithelial cells (ECE16-1). Exposure of ECE16-1 to TGF-beta1 increased expression of p53 and induced cell cycle arrest. We examined, by Western blotting, expression of p53 and related cell cycle regulatory proteins after treatment. p53 levels increased as a function of time and dose. Increased p53 appeared to be active, since TGF-beta1 treatment increased the activity of a p53 transcriptional response element in a luciferase reporter plasmid. Additionally, the proteins of the p53-regulated genes, p21(WAF1), mdm2, and Bax, were increased with similar time and dose responses. We did not observe consistent changes in protein levels of cyclin D, cyclin E, CDK4, CDK6, CDK2, p27(Kip1), p16(INK4a), or RNA levels of p15(INK4b). Activity of CDK4 or 6, measured by phosphorylation of an Rb fragment, remained constant during the response period; however, activity of CDK2 (phosphorylation of histone H1) decreased. Concordantly, increased levels of p21(WAF1) were immunoprecipitated with anti-CDK2 antibodies. During treatment, the phosphorylation state of Rb shifted to a hypophosphorylated form. mRNA for the HPV E6/E7 genes decreased; however, significant changes in the E7 protein were not observed, while increased levels of Rb immunoprecipitated with anti-E7 antibodies were observed. These data are consistent with the following model. In ECE16-1 cells, there exists a fine balance between inhibitory levels of p53 and Rb and the antagonists, E6 and E7. TGF-beta1 treatment decreases steady-state levels of E6/E7 mRNA, which results in a shifted balance (lowered activity of E6) in favor of increased p53 expression, resulting in activation of the cell cycle inhibitory gene, p21(WAF1). This protein binds the cyclin E/CDK2 complex that maintains Rb in a phosphorylated state. Rb shifts to a hypophosphorylated state, resulting in G1 arrest, presumably by binding E2F transcription factors.

Endocervical cancer is associated with an increase in the ligands and receptors for transforming growth factor-beta and a contrasting decrease in p27(Kip1)

OBJECTIVE

The aim of this study was to investigate the relationship between the expression of the TGF-beta ligands and TGF-beta receptors to the expression of p27(Kip1), a TGF-beta-regulated gene, in endocervical cancer.

METHODS

To examine the expression of TGF-beta and p27(Kip1) in malignant transformation of the uterine endocervix, a panel of 23 formalin-fixed and paraffin-embedded human cervical specimens, including 8 with benign endocervical glands, 8 with cervical adenocarcinoma in situ, and 7 with cervical adenocarcinomas, was used. Tissues were immunostained with polyclonal antibodies that react specifically with TGF-beta 1, TGF-beta 2, TGF-beta 3, TGF-beta RI, TGF-beta RII, and p27(Kip1).

RESULTS

Immunostaining for TGF-beta 1, TGF-beta 2, TGF-beta 3, TGF-beta RI, TGF-beta RII, and p27(Kip1) was detected in normal endocervix, with the TGF-betas showing weak cytoplasmic staining, while p27(Kip1) showed strong nuclear staining. Expression of TGF-beta increased significantly upon neoplastic transformation with the TGF-beta ligands and receptors showing strong cytoplasmic staining in adenocarcinoma in situ compared to normal endocervix. Interestingly, expression of TGF-beta was lower in adenocarcinoma than in adenocarcinoma in situ, but still significantly higher than in normal endocervix. TGF-beta 2 and TGF-beta 3 showed higher levels of immunostaining than TGF-beta 1 in adenocarcinomas. In contrast, p27(Kip1) protein expression decreased with progressive malignancy, with lower p27(Kip1) protein levels detected in adenocarcinoma than in adenocarcinoma in situ, while normal endocervix showed the highest level of p27(Kip1) protein expression.

CONCLUSION

Elevated expression of the TGF-beta ligands and receptors is found in both cervical adenocarcinoma in situ and adenocarcinoma compared to normal endocervix. In contrast, a progressive decrease in p27(Kip1) occurs upon neoplastic transformation of the normal endocervix to cervical adenocarcinoma. These results suggest that neoplastic transformation of the endocervix may be related to dysregulation of TGF-beta and p27(Kip1) seen as an elevation of TGF-beta and a reduction of p27(Kip1) expression that may lead to loss of cell cycle control.

Retinoic acid resistance at late stages of human papillomavirus type 16-mediated transformation of human keratinocytes arises despite intact retinoid signaling and is due to a loss of sensitivity to transforming growth factor-beta

In our in vitro model of human cell carcinogenesis, normal human foreskin keratinocytes (HKc) transfected with human papillomavirus type 16 DNA (HKc/HPV16) progress toward malignancy through several phenotypically defined and reproducible "steps" that include immortalization, growth factor independence (HKc/GFI), differentiation resistance (HKc/DR), and ultimately malignant conversion. While HKc/HPV16 are very sensitive to growth inhibition by all-trans-retinoic acid (RA) at early passages, they lose their sensitivity to RA during progression in culture. However, gel mobility shift assays using the retinoid response elements DR1 and DR5 showed no changes in binding activity of nuclear extracts obtained from HKc/HPV16 at different stages of in vitro progression. Similarly, Western blot analyses for retinoic acid receptor gamma-1 and the retinoid X receptors failed to reveal any decreases in the levels of these retinoid receptors throughout progression. In addition, luciferase activity driven by the SV40 promoter with a DR5 enhancer element was activated following RA treatment of HKc/DR that were resistant to growth inhibition by RA. Since RA induces transforming growth factor-beta2 (TGF-beta2) in normal HKc and HKc/HPV16, we investigated whether this response changed during progression. Again, RA induced TGF-beta2 mRNA in early and late passage HKc/HPV16, HKc/GFI, and HKc/DR approximately to the same extent, confirming that the RA signaling pathways remained intact during in vitro progression despite the fact that the cells become resistant to growth inhibition by RA. We then investigated the sensitivity of HKc/HPV16 to growth inhibition by TGF-beta. While early passage HKc/HPV16 were as sensitive as normal HKc to growth inhibition by TGF-beta1 and TGF-beta2, the cells became increasingly resistant to both TGF-beta isotypes during in vitro progression. In addition, while both RA and TGF-beta produced a decrease in the levels of mRNA for the HPV16 oncogenes E6 and E7 in early passage HKc/HPV16, this effect was also lost at later stages of progression. Finally, blocking anti-TGF-beta antibodies partially prevented RA inhibition of growth and E6/E7 expression in early passage HKc/HPV16. Taken together, these data strongly suggest that inhibition of growth and HPV16 early gene expression in HKc/HPV16 by RA is mediated by TGF-beta and that a loss of RA sensitivity is linked to TGF-beta resistance rather than alterations in RA signaling.

Monocyte-chemo-attractant-protein-1 (MCP-1)-gene expression in cervical intra-epithelial neoplasias and cervical carcinomas

Chemokines play a central role in the chemotactic activation of immunological effector cells. One of the currently best characterized chemokines is the monocyte-chemo-attractant protein-1 (MCP-1), which is involved in the cross-talk with cells of the monocyte-macrophage lineage. Since macrophages and macrophage-derived cytokines appear to be important in the transcriptional regulation of "high-risk" types of human papillomaviruses (HPV), we monitored MCP-1 expression by in situ hybridization (ISH) in histologically distinct stages of cervical intra-epithelial neoplasms (CIN), cervical cancer and non-HPV-associated cases of erosive endocervicitis. Here, we demonstrate that high-grade dysplasia (CIN III, n = 9) completely lacks both MCP-1 expression and CD68+-macrophage infiltration, while MCP-1-specific signals were occasionally detectable in one out of 5 CIN-II and in one out of 3 CIN-I lesions. Inspection of hyperplastic squamous epithelium adjacent to cervical carcinomas reveals high MCP-1 expression and accumulation of infiltrating macrophages. In contrast, no macrophages could be detected in corresponding hyperplastic tissue areas surrounding CIN-II and CIN-III lesions, although MCP-1 was found to be highly expressed. Finally, in agreement with our earlier in vitro data, invasive carcinomas of the cervix uteri showed MCP-1-specific hybridization signals and macrophage infiltration only in the stroma surrounding the carcinoma cells and in endothelial cells of capillaries, especially at the invasion front of the tumor, while the inner mass of the carcinomas was completely negative. On the other hand, ISH and histochemical evaluation of inflammatory, non-HPV-associated cases of erosive endocervicitis indicate strong MCP-1 expression, which is regularly accompanied by chemotactic appearance of macrophages. These observations indicate that dysregulation of MCP-1-gene expression may represent an important step during HPV-linked carcinogenesis, allowing the escape of virus-positive cells from local immune response.

Structural alterations of transforming growth factor-beta receptor genes in human cervical carcinoma

The development and progression of invasive uterine cervical carcinomas appear to be associated with the progressive loss of sensitivity to transforming growth factor-beta (TGFbeta)-mediated cell cycle arrest. In order to identify possible molecular mechanisms responsible for TGFbeta resistance, we screened the 7 exons of the type II (TbetaR-II) TGFbeta receptor and the 9 exons of the type I (TbetaR-I) TGFbeta receptor genes for mutations in 16 paraffin-embedded primary invasive cervical carcinoma specimens. In one of these carcinomas, we found a novel G-->T transversion in exon 3 of TbetaR-II that introduces a premature stop codon (E142Stop) and presumably results in the synthesis of a truncated soluble exoreceptor. In one tumor, a silent A-->C transversion mutation that may affect mRNA splicing was present in exon 6 of TbetaR-I. In addition, 7 of 16 cases were heterozygous for a G-->A polymorphism in intron 7 of TbetaR-I. Finally, we identified a 9 base pair in-frame germline deletion in exon 1 of TbetaR-I resulting in loss of 3 of 9 sequential alanine residues at the N-terminus in 6 of 16 cases. Analysis of specimens from case-control studies indicated that carriers of this del(GGC)3 TbetaR-I variant allele may be at a increased risk for the development of cervical carcinoma (p=0.22). Furthermore, the response of cells expressing the variant receptor to TGFbeta was diminished. Our results support the notion that diverse alterations in the TGFbeta signaling pathway may play a role in the development of cervical cancer.

Clinical models of chemoprevention for cervical cancer

Cervical carcinoma creates a worldwide, significant population burden that potentially could be reduced by new preventive strategies for cervical cancer such as chemoprevention. Given the vast array of clinical and molecular information available relating to cervical cancer and the precursor lesions along with a growing number of new molecular techniques, a model is needed to guide further investigation. Such a model would facilitate research design, guide hypothesis development and testing, and focus the use of molecular data collection and analysis. This article reviews the clinical and molecular data of cervical cancer and the precursor lesions in order to develop a model for chemoprevention research in cervical cancer.

Genetic integrity of transforming growth factor beta (TGF-beta) receptors in cervical carcinoma cell lines: loss of growth sensitivity but conserved transcriptional response to TGF-beta

Transforming growth factor beta (TGF-beta) exerts an inhibitory effect on the growth of most epithelial cell types, and the loss of responsiveness to this growth inhibition has been implicated in the development of a variety of human cancers. The genetic alteration of TGF-beta receptors is known to play a critical role in this escape from growth regulation. We asked whether there is a correlation between TGF-beta sensitivity and the genetic status of TGF-beta type I and type II receptors (RI and RII, respectively) in human cervical carcinoma cell lines. Among 8 cell lines examined, 3 (ME-180, C-33A and HeLaS3) showed resistance to TGF-beta and 3 (SiHa, CaSki and HeLa229) showed minimal response to the growth inhibitory effect of TGF-beta; the other cell lines (HeLa and HT-3) were sensitive. Northern blot analysis revealed that the RII mRNA was not expressed in 2 TGF-beta-resistant cell lines (ME-180 and C-33A) but was expressed in the other cell lines. Southern blot analysis of RI and RII revealed a homozygous deletion of the entire TGF-beta RII gene in the cell line ME-180. We then asked whether the other TGF-beta-resistant or refractory cell lines had microsatellite instability and/or poly-adenine tract mutations of RII. We also checked for point mutations in the individual exons of the entire RII using polymerase chain reaction-single-strand conformational polymorphism (PCR-SSCP). Although C-33A exhibited poly-adenine microsatellite instability, its RII gene showed no signs of mutation. The molecular integrity of the TGF-beta, receptors in all cell lines, except ME-180 and C-33A, could be confirmed by examining the distinct transcriptional induction of plasminogen activator inhibitor-1 (PAI-1), p21(WAF1/CIP1) and, in some cases, the accompanying downregulation of c-myc in response to TGF-beta. Our observations, taken together, indicate that inactivation of the RII contributes to the resistance to TGF-beta of some cervical carcinoma cell lines. Loss of or attenuated sensitivity to TGF-beta growth inhibition in other cells may be attributed to the disruption of distal components in the TGF-beta signal pathway, but not to the receptor system.

Cytokine expression in squamous intraepithelial lesions of the uterine cervix: implications for the generation of local immunosuppression

We have addressed the notion that the progression of cancer of the uterine cervix is associated with a preferential constraint on the development of a type 1 cellular mediated response, which is necessary to efficiently eliminate (pre)neoplastic cells. Based on the importance of cytokines in the regulation of an appropriate immune response, we have evaluated the expression of IL-12p40, IL-10 and transforming growth factor-beta 1 (TGF-beta1). Using reverse transcriptase-polymerase chain reaction (RT-PCR), the expression of these three cytokines was evaluated in both low-grade (LG) and high-grade (HG) cervical squamous intraepithelial lesions (SIL) and in normal exocervix and transformation zone biopsies. Our results show that the average level of IL-12 increases within both the LG and HG SIL, compared with both control groups. Interestingly, the percentage of HG SIL expressing IL-12p40 was lower compared with LG SIL. In contrast, the expression of IL-10 increased in parallel with the severity of the lesion to a maximal level in HG SIL. Using immunohistochemistry, we ascertained the presence of IL-12 protein in SIL and IL-10 protein in the transformation zone and SIL biopsies. Both IL-12- and IL-10-producing cells were localized in the stroma, not within the SIL. Furthermore, in this study we also observed that the region of the cervix the most sensitive to lesion development, the transformation zone, was associated with higher average levels of the immunosuppressive cytokines IL-10 and TGF-beta1.

Transforming growth factor-beta 1 induces apoptosis through down-regulation of c-myc gene and overexpression of p27Kip1 protein in cervical carcinoma

Transforming growth factor-beta 1 (TGF-beta 1) is known to be a potent growth inhibitor for many cell types, including most epithelial cells. In skin keratinocytes, TGF-beta 1 has been shown to inhibit growth and to rapidly reduce c-myc expression. However, the molecular mechanism of TGF-beta 1 action on cell growth of cervical carcinoma has not yet been elucidated. We thus assessed the effect of TGF-beta 1 on the growth of cervical carcinoma cell lines. Two cervical squamous carcinoma cell lines, CUMC-3 and CUMC-6, were incubated with varying concentrations of TGF-beta 1, and growth inhibition was evaluated with tetrazolium-based colorimetric assay. After culture in TGF-beta 1 for 24 h, inhibition of growth was detected in a dose-dependent manner at concentrations of 0.1-10 ng/ml in both cell lines. This effect of TGF-beta 1 on cultured carcinoma cells was associated with apoptotic process including oligonucleosomal ladder DNA and apoptotic body formations. Northern blot analysis revealed c-myc mRNA expression was suppressed by 10 ng/ml of TGF-beta 1 following 3 h of treatment in both cell lines. Western blot analysis showed that the level of p27Kip1 protein was increased after TGF-beta 1 treatment in both cell lines. These results suggest that the mechanisms by which TGF-beta 1 inhibits the growth of cervical carcinoma are complex and may include effects on down-regulation of c-myc gene, and overexpression of p27Kip1 protein.

The genetic program of genital human papillomaviruses in infection and cancer

Human papillomavirus (HPV) infection has been recognized as the major cause of cervical cancer. This article summarizes the functions of HPV gene products that cause abnormal cell growth--E6 and E7--and reviews how cellular and viral factors influence their synthesis. E6 and E7 inactivate two cellular tumor-suppressor gene products, p53 and RB. In cervical cancer, E6-E7 gene control is deranged by mutations in viral control sequences and in integrated HPV fragments by the disruption of the viral repressor E2. Elimination of this sequence makes E6-E7 mRNAs unstable, and deranges cellular regulation at the integration site. It is apparent that an intricate interplay of cellular and viral factors determines whether the outcome is active papillomavirus infection, viral latency, or ultimately, genital cancer.