Cytoplasmic/nuclear expression without mutation of exon 3 of the beta-catenin gene is frequent in the development of the neoplasm of the uterine cervix

HPV-driven oncogenesis-much more than the E6 and E7 oncoproteins

High-risk human papillomaviruses are well-established drivers of several cancer types including cervical, head and neck, penile as well as anal cancers. While the E6 and E7 viral oncoproteins have proven to be critical for malignant transformation, evidence is also beginning to emerge suggesting that both host pathways and additional viral genes may also be pivotal for malignant transformation. Here, we focus on the role of host APOBEC genes, which have an important role in molecular editing including in the response to the viral DNA and their role in HPV-driven carcinogenesis. Further, we also discuss data developed suggesting the existence of HPV-derived miRNAs in HPV + tumors and their potential role in regulating the host transcriptome. Collectively, while recent advances in these two areas have added complexity to the working model of papillomavirus-induced oncogenesis, these discoveries have also shed a light onto new areas of research that will be required to fully understand the process.

Multidimensional outlook on the pathophysiology of cervical cancer invasion and metastasis

Cervical cancer being one of the primary causes of high mortality rates among women is an area of concern, especially with ineffective treatment strategies. Extensive studies are carried out to understand various aspects of cervical cancer initiation, development and progression; however, invasive cervical squamous cell carcinoma has poor outcomes. Moreover, the advanced stages of cervical cancer may involve lymphatic circulation with a high risk of tumor recurrence at distant metastatic sites. Dysregulation of the cervical microbiome by human papillomavirus (HPV) together with immune response modulation and the occurrence of novel mutations that trigger genomic instability causes malignant transformation at the cervix. In this review, we focus on the major risk factors as well as the functionally altered signaling pathways promoting the transformation of cervical intraepithelial neoplasia into invasive squamous cell carcinoma. We further elucidate genetic and epigenetic variations to highlight the complexity of causal factors of cervical cancer as well as the metastatic potential due to the changes in immune response, epigenetic regulation, DNA repair capacity, and cell cycle progression. Our bioinformatics analysis on metastatic and non-metastatic cervical cancer datasets identified various significantly and differentially expressed genes as well as the downregulation of potential tumor suppressor microRNA miR-28-5p. Thus, a comprehensive understanding of the genomic landscape in invasive and metastatic cervical cancer will help in stratifying the patient groups and designing potential therapeutic strategies.

The immunolocalization of cadherins and beta-catenin in the cervix and vagina of cycling cows

The adherens junctions (AJs) maintain the epithelial cell layers' structural integrity and barrier function. AJs also play a vital role in various biological and pathological processes. AJs perform these functions through the cadherin-catenin adhesion complex. This study investigated the presence, cell-specific localization, and temporal distribution of AJ components such as classical type I cadherins and beta-catenin in the cow cervix and vagina during the estrous cycle. Immunohistochemistry and Western blot analysis results demonstrated that beta-catenin and epithelial (E)-, neural (N)-, and placental (P)-cadherins are expressed in the cow cervix and vagina during the estrous cycle. These adhesion molecules were localized in the membrane and cytoplasm of the ciliated and non-ciliated cervical cells and the stratified vaginal epithelial cells. Positive immunostaining for P-, N-cadherin, and beta-catenin was also observed in the vascular endothelial cells of the cervical and vaginal stroma. Quantitative immunohistochemistry examinations revealed that in the cervical and vaginal epithelia, P-cadherin's optical density values (ODv) were the highest; in contrast, the N-cadherin ODv were the lowest. The ODv of P-cadherin and beta-catenin in the cervical epithelium and E-cadherin in the vagina were significantly higher in the luteal phase versus the follicular phase of the estrous cycle. Furthermore, the ODv of P-cadherin, N-cadherin, and beta-catenin in the cervix's central and peripheral epithelial regions were different during the estrous cycle. These findings indicate that classical cadherins and beta-catenin in the cervix and vagina exhibit cell- and tissue-specific expression patterns under the influence of estrogen and progesterone hormones during the estrous cycle.

Sdy-1 Executes Antitumor Activity in HepG2 and HeLa Cancer Cells by Inhibiting the Wnt/β-Catenin Signaling Pathway

Demethylincisterol A₃ (Sdy-1), a highly degraded sterol that we previously isolated from Chinese mangrove Rhizophora mucronata endophytic Pestalotiopsis sp. HQD-6, exhibits potent antitumor activity towards a variety of cancer cells. In this study, we further verified that Sdy-1 effectively inhibited the proliferation and migration of human liver (HepG2) and cervical cancer (HeLa) cells in vitro and it can induce cell apoptosis and arrest the cell cycle in the G1-phase. Mechanistically, we demonstrated that Sdy-1 executes its function via inhibition of the Wnt/β-catenin signaling pathway. Sdy-1 may not inhibit the Wnt signaling pathway through the cascade reaction from upstream to downstream, but directly acts on β-catenin to reduce its transcription level, thereby reducing the level of β-catenin protein and further reducing the expression of downstream related proteins. The possible interaction between Sdy-1 and β-catenin protein was further confirmed by molecular docking studies. In the nude mouse xenograft model, Sdy-1 can also significantly inhibit tumor growth. These results indicated that Sdy-1 is an efficient inhibitor of the Wnt signaling pathway and is a promising antitumor candidate for therapeutic applications.

MicroRNA-135a-induced formation of CD133+ subpopulation with cancer stem cell properties in cervical cancer

Cancer stem cells (CSCs) play significant roles in tumor initiation. MicroRNA-135a (miR-135a) induced the formation of a CD133+ subpopulation from a human papillomavirus-immortalized cervical epithelial cell line. Compared with the CD133- cells, the CD133+ cells expressed higher levels of miR-135a and OCT4, exhibited significantly higher tumorsphere forming capacity and the time required for tumorsphere formation was shortened in the second generation. Serum induction suppressed the expression of CD133, OCT4 and miR-135a, but increased expression of involucrin in the miR-135a-induced CD133+ cells. The miR-135a-induced CD133+ cells were tumorigenic in a limiting dilution approach in vivo. The cells expressed significantly higher level of active β-catenin and OCT4 than the CD133- counterpart. Wnt3a enhanced the expression of OCT4 and CD133 in cervical cancer cells but failed to enhance CD133 transcription in normal cervical cells. Wnt3a stimulation also increased tumorsphere size and self-renewal of miR-135a-induced CD133+ subpopulation. Wnt/β-catenin inhibition suppressed tumorsphere formation while Wnt3a partially nullified the inhibitory effect. Taken together, miR-135a induced the formation of a subpopulation of cells with CSC properties both in vitro and in vivo and the Wnt/β-catenin signaling pathway is essential to maintain its tumorigenicity.

miR-326 inhibits the cell proliferation and cancer stem cell-like property of cervical cancer in vitro and oncogenesis in vivo via targeting TCF4

Background

Cervical cancer ranks as one of the most prevalent female malignancies globally, and its treatment with new targets has been the focus of current research. The present study set out to investigate the function of microRNA-326 (miR-326) in vitro and in vivo and to verify the direct targeting of transcription factor 4 (TCF4) by miR-326.

Methods

The detection of messenger RNA (mRNA) expressing miR-326 and TCF4 in cervical cancer cell lines and tumor samples was conducted using quantitative real-time polymerase chain (qRT-PCR). A dual-luciferase reporter assay was carried out to detect the target relationship of miR-326 with TCF4. A Cell Counting Kit-8 (CCK-8) assay was employed to detect the effect of miR-326 on CasKi cell viability. Flow cytometry and western blotting were employed to examine the effects of miR-326 on cancer stem cell (CSC)-like property. Tumor weight was measured in orthotopic xenograft mouse models. Immunohistochemistry was employed to analyze the protein expression levels of Ki-67, proliferating cell nuclear antigen (PCNA), CD44, and SRY-box 4 (SOX4).

Result

Downregulation of the mRNA expression levels of miR-326 was observed in cervical cancer cell lines and tumor tissue, while the levels of TCF4 were upregulated. The dual-luciferase reporter assay revealed binding of miR-326 to the three prime untranslated region (3'-UTR) of TCF4. In vitro assays demonstrated that miR-326 inhibited CasKi cell proliferation through regulating TCF4. miR-326 also suppressed the CSC-like property of CasKi cells by targeting TCF4. Furthermore, the protein expression levels of cyclin D1, β-catenin, and c-Myc were decreased when miR-326 was added to TCF4-transfected cells. In vivo assays demonstrated that miR-326 inhibited tumor weight, growth, and the protein expression levels of Ki-67, PCNA, CD44, SOX4, and β-catenin.

Conclusions

miR-326 acted in a tumor-suppressive manner through its regulation of TCF4, and has potential as a biomarker or therapeutic target for cervical cancer.

β-Catenin immunocytochemical reactivity in cervicovaginal smears during regular menstrual cycles

Background

β-Catenin mediates cellular adhesion and the Wnt/β-catenin signaling mechanism, thereby controlling cell proliferation and differentiation. Studies of endometrial tissue suggest that there are differences in β-catenin expression during the course of regular menstrual cycles. However, differences in expression in squamous epithelial cells between the proliferative and secretory phases have hitherto remained unknown.

Objectives

To localize β-catenin in squamous epithelial cells in cervicovaginal smears during the course of regular menstrual cycles.

Methods

In this observational study, smears were taken from women (n = 102) with various gynecological complaints. Squamous epithelial cells were stained using a Papanicolaou method to evaluate their cytology and any infection. An anti-β-catenin antibody was used to localize immunoreactivity in the cell membrane, cytoplasm, and/or nucleus.

Results

Women with a regular menstrual cycle (n = 62) were divided into 2 groups: those in a proliferative phase (26/62, 42%) and those in a secretory phase (36/62, 58%). Cytoplasmic and nuclear β-catenin immunoreactivity was observed prominently in the proliferative phase (19/26, 73%), whereas low-level β-catenin immunoreactivity was seen in the secretory phase (9/36, 25%). Compared with the secretory phase, the mean H-scores for β-catenin immunoreactivity in the proliferative phase were significantly increased in the membrane (P = 0.039), the cytoplasm (P < 0.001), and the nucleus (P = 0.033). By contrast, β-catenin immunoreactivity was reduced from parabasal to superficial cells in both the proliferative and secretory phases.

Conclusions

Cytoplasmic and/or nuclear β-catenin immunoreactivity may indicate that the activity of the Wnt/β-catenin signaling pathway is cycle dependent.

β-Catenin: oncogenic role and therapeutic target in cervical cancer

Cervical cancer is a common and fatal malignancy of the female reproductive system. Human papillomavirus (HPV) is the primary causal agent for cervical cancer, but HPV infection alone is insufficient to cause the disease. Actually, most HPV infections are sub-clinical and cleared spontaneously by the host immune system; very few persist and eventually develop into cervical cancer. Therefore, other host or environmental alterations could also contribute to the malignant phenotype. One of the candidate co-factors is the β-catenin protein, a pivotal component of the Wnt/β-catenin signaling pathway. β-Catenin mainly implicates two major cellular activities: cell–cell adhesion and signal transduction. Recent studies have indicated that an imbalance in the structural and signaling properties of β-catenin leads to various cancers, such as cervical cancer. In this review, we will systematically summarize the role of β-catenin in cervical cancer and provide new insights into therapeutic strategies.

Molecular mechanisms in progression of HPV-associated cervical carcinogenesis

Cervical cancer is the fourth most frequent cancer in women worldwide and a major cause of mortality in developing countries. Persistent infection with high-risk human papillomavirus (HPV) is a necessary cause for the development of cervical cancer. In addition, genetic and epigenetic alterations in host cell genes are crucial for progression of cervical precancerous lesions to invasive cancer. Although much progress has been made in understanding the life cycle of HPV and it’s role in the development of cervical cancer, there is still a critical need for accurate surveillance strategies and targeted therapeutic options to eradicate these cancers in patients. Given the widespread nature of HPV infection and the type specificity of currently available HPV vaccines, it is crucial that molecular details of the natural history of HPV infection as well as the biological activities of viral oncoproteins be elucidated. A better understanding of the mechanisms involved in oncogenesis can provide novel insights and opportunities for designing effective therapeutic approaches against HPV-associated malignancies. In this review, we briefly summarize epigenetic alterations and events that cause alterations in host genomes inducing cell cycle deregulation, aberrant proliferation and genomic instability contributing to tumorigenesis.

Knockdown of PKM2 suppresses tumor progression in human cervical cancer by modulating epithelial-mesenchymal transition via Wnt/β-catenin signaling

Background

Pyruvate kinase isozyme type M2 (PKM2) is a key glycolytic enzyme and is upregulated in multiple human malignancies. However, the role of PKM2 in human cervical cancer (CC) remains elusive. Thus, this study explored the role of PKM2 in CC by detecting its expression patterns in human CC tissues and cell lines and investigated its effects on cell proliferation and invasion.

Materials and methods

Quantitative reverse transcription polymerase chain reaction (qRT-PCR), immunohistochemistry and western blotting assays were used to detect the expression of PKM2 in CC tissues and CC cells. In vitro, we overexpressed and knocked down PKM2 expression in CC cell lines and investigated the biological function and underlying mechanism of PKM2 in cervical carcinogenesis.

Results

The results showed that PKM2 mRNA and protein were highly expressed in CC tissues and cell lines. Furthermore, increasing PKM2 expression was closely correlated with the clinical stage (P=0.001) and lymph node metastasis (P=0.023). The functional roles of PKM2 were determined using Cell Counting Kit-8, colony formation, and transwell assays. The results showed that PKM2 knockdown inhibited cell proliferation and the migratory and invasive capacities of CC cells, suppressed epithelial–mesenchymal transition (EMT), and inhibited Wnt/β-catenin signaling in vitro. However, overexpression of PKM2 led to increased proliferation and invasion activity as well as the EMT in CC cells.

Conclusion

Taken together, our study results revealed that PKM2 may act as a molecular target for CC treatment.

Effects of secreted frizzled-related protein 1 on proliferation, migration, invasion, and apoptosis of colorectal cancer cells

Background

Secreted frizzled-related protein 1 (SFRP1) is a member of the SFRPs family that modulates the Wnt signal transduction pathway. Recent studies have showed down-regulation of SFRP1 expression in colorectal cancer (CRC). We aimed to evaluate the effect of SFRP1 on the proliferation, migration, invasion and apoptosis of CRC cells in vitro.

Materials and methods

We used real-time fluorescence quantification (RT-PCR) and Western blotting to detect SFRP1 expression in CRC, pericarcinomatous tissues and CRC cell lines. We assessed the influence of overexpression and knockdown of SFRP1 on CRC cell proliferation, migration, invasion, and apoptosis, Western blotting was used to evaluate protein levels of Wnt, β-catenin, and apoptosis-related proteins.

Results

The expression of SFRP1 was significantly decreased in CRC tissues. Among the six CRC cell lines (sw-480, sw1116, caco-2, ht-29, colo-205, and hct-116), RT-PCR revealed that sw1116 cells had the lowest expression of SFRP1, while caco-2 cells had the highest SFRP1 expression. SFRP1 overexpression in sw1116 cells significantly suppressed cell proliferation while SFRP1 knockdown in caco-2 cells significantly increase the cell proliferation. In addition, overexpression of SFRP1 in sw1116 cells remarkedly suppressed cell migration and invasion, whereas knockdown of SFRP1 in caco-2 cells resulted in significant enhancement of migration and invasion. Furthermore, SFRP1 overexpression in sw1116 cells promoted cell apoptosis. Western blotting showed that SFRP1 overexpression significantly decreased the protein levels of Wnt, β-catenin and apoptosis-related proteins, including MMP2, MMP9, Twist, CDK1, TGF, and Bcl2.

Conclusion

Our results demonstrate that SFRP1 suppresses cell proliferation, migration and invasion, and promotes apoptosis in CRC cells.

Downregulation of nuclear and cytoplasmic Chibby is associated with advanced cervical cancer

Chibby has been identified as a putative tumor suppressor and antagonist to β-catenin, thereby controlling the Wnt signaling pathway. Chibby is typically downregulated in numerous types of cancer and may be associated with tumorigenesis. The present study aimed at clarifying the following: i) Whether Chibby antagonizes β-catenin in cervical cancer; ii) whether Chibby and β-catenin mRNA expression is associated with cancer progression; and iii) whether Chibby and β-catenin expression may be used as a biomarker. A total of 87 paraffin-embedded cervical sections with distinct cervical intraepithelial neoplasia (CIN) stages (chronic cervicitis, CIN 1, CIN 2, CIN 3 and invasive squamous cell carcinoma) were collected between June 2004 and October 2012 The mRNA expression level of Chibby and β-catenin was determined using the polymerase chain reaction. Protein expression and cellular localization of Chibby and β-catenin were determined using immunohistochemistry. Chibby and β-catenin were analyzed for possible association with the progression of cervical cancer. Chibby mRNA expression and the Chibby/β-catenin ratio were identified to be downregulated in invasive tumors. Positive cytoplasmic and nuclear staining for Chibby was associated with CIN staging and decreased as the CIN stage increased. In addition, the cytoplasmic and membrane intensity of β-catenin was associated with invasive tumors, in which a significantly increased level of protein expression was detected. Chibby may be a tumor suppressor in cervical cancer, since the dysregulation of Chibby expression is associated with tumorigenesis in cervical cancer. Chibby and β-catenin expression together may potentially to a biomarker for disease progression in cervical cancer.

Wnt/β‑catenin pathway activation and silencing of the APC gene in HPV‑positive human cervical cancer‑derived cells

Although persistent infections with high-risk human papilloma virus (HPV) constitute the most significant cofactor for the development of cervical cancer, they are insufficient on their own. Mutations or epigenetic inactivation of the tumor suppressor adenomatous polyposis coli (APC), the two acting as prominent oncogenic mechanisms in a number of types of cancer, are frequently associated with aberrant activation of the Wnt/β-catenin pathway. According to these observations, it was hypothesized that APC alteration may lead to β-catenin deregulation and the abnormal expression of direct targets of the Wnt pathway in HPV-infected cervical cancer cells. The present study confirmed that the stabilization of β-catenin correlates with enhanced transcriptional activity of the β-catenin/T-cell factor complex in cervical cancer cell lines. Sequence analysis of the ‘hot-spot’ in the mutation cluster region did not exhibit genetic alterations that may be associated with APC gene inactivation. In addition, it was identified that there was a good correlation with the hypermethylation status of the APC promoter 1A and the abnormal accumulation of endogenous β-catenin in cell lines and biopsies infected with HPV16, although not HPV18. Removal of the epigenetic markers led to an increase in APC levels and a reduction of β-catenin expression in two transcriptional targets of the Wnt pathway: Matrix metalloproteinase-7 and vascular endothelial growth factor. The present study suggested that the increase in Wnt activity in certain cervical cancer-derived cells may be associated with an alteration in the methylation status of the APC gene promoter 1A.

Activation of the Wnt/β-catenin signaling pathway may contribute to cervical cancer pathogenesis via upregulation of Twist

The Wnt signaling pathway regulates a number of biological processes. In the present study, the association between the Wnt signaling pathway and the pathogenesis of cervical cancer was investigated in the human cervical cancer CaSki cell line. An MTT assay was used to screen various concentrations of lithium chloride for use in subsequent experiments. Following incubation of CaSki cells with 0.05 and 0.1 mol/l lithium chloride, Twist and β-catenin were markedly upregulated at the mRNA and protein levels, respectively, compared with the untreated group, as measured by reverse transcription-polymerase chain reaction and western blotting. The results of the present study indicate that Wnt activation (which was induced by lithium chloride) and the subsequent upregulation of Twist may represent one of the molecular mechanisms underlying the occurrence and development of cervical cancer.

Tracking the origin of simultaneous endometrial and ovarian cancer by next-generation sequencing - a case report

Background

Endometrioid adenocarcinoma of the uterus and ovarian endometrioid carcinoma share many morphological and molecular features. Differentiation between simultaneous primary carcinomas and ovarian metastases of an endometrial cancer may be very challenging but is essential for prognostic and therapeutic considerations.

Case Presentation

In the present case study of a 33 year-old patient we used targeted amplicon next-generation re-sequencing for clarifying the origin of synchronous endometrioid cancer of the corpus uteri and the left ovary. The patient developed a metachronous lung metastasis of an endometrioid adenocarcinoma four years after hyster- and adnexectomy, vaginal brachytherapy and treatment with the synthetic steroid tibolone. Removal of the metastasis and megestrol treatment for seven years led to a complete remission.

A total of 409 genes from the Ampliseq Comprehensive Cancer Panel (Ion Torrent, Thermo Fisher) were analysed by next generation sequencing and mutations in 10 genes, including ARID1A, CTNNB1, PIK3CA and PTEN were identified and confirmed by Sanger sequencing. Primary endometrial as well as ovarian cancer showed an identical mutational profile, suggesting the presence of an ovarian metastasis of the endometrial cancer, rather than a simultaneous endometrial and ovarian cancer. The metachronous lung metastasis showed a different mutational profile compared to the primary cancer. Immunohistochemical staining of the corresponding proteins suggested that the tumour development was driven by alterations in the protein function rather than by changes of the protein abundance in the cell.

Conclusions

Our results have demonstrated next generation sequencing as a valuable tool in the differentiation of synchronous primary tumours and metastases, which has an important impact on the clinical decision making process. Similar to breast cancer, targeted therapies based on mutational tumour profiling will become increasingly important in endometrial and ovarian cancer. In summary, our results support the usage of next generation sequencing as a supplementary diagnostic tool, assisting in personalized precision medicine.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-017-3054-6) contains supplementary material, which is available to authorized users.

MicroRNA-320 regulates the radiosensitivity of cervical cancer cells C33AR by targeting β-catenin

Cervical cancer is the second most common malignancy in women worldwide and always has recurrence owing to radioresistance. MicroRNA (miRNA or miR) has been identified to relate to the sensitivity of cancer radiotherapy. Here, we investigated the potential of miRNA-320 as a biomarker for radiosensitivity by targeting β-catenin in cervical cancer. A radioresistant cervical cancer cell line, C33AR, was established, and the radioresistance of C33AR cells was confirmed by a colony-formation assay. The expression of miRNA-320 was detected by reverse transcription-quantitative polymerase chain reaction, and compared between C33A and C33AR. β-catenin, the target of miRNA-320, was determined at the protein level by western blotting after transfecting the inhibitor of miRNA-320. The expression of miRNA-320 was markedly decreased in C33AR cells, which appeared to be more radioresistant, compared with its parental cell line C33A. Target prediction suggested that miRNA-320 negatively regulated the expression of β-catenin. Knockdown of β-catenin increased C33AR radiosensitivity, which revealed that the inhibition of β-catenin could rescue the miRNA-320-mediated cell radioresistance. On the other hand, overexpressing miRNA-320 increased C33AR radiosensitivity. In conclusion, miRNA-320 regulated the radiosensitivity of C33AR cells by targeting β-catenin. This finding provides evidence that miRNA-320 may be a potential biomarker of radiosensitivity in cervical cancer.

Frizzled7: A Promising Achilles' Heel for Targeting the Wnt Receptor Complex to Treat Cancer

Frizzled7 is arguably the most studied member of the Frizzled family, which are the cognate Wnt receptors. Frizzled7 is highly conserved through evolution, from Hydra through to humans, and is expressed in diverse organisms, tissues and human disease contexts. Frizzled receptors can homo- or hetero-polymerise and associate with several co-receptors to transmit Wnt signalling. Notably, Frizzled7 can transmit signalling via multiple Wnt transduction pathways and bind to several different Wnt ligands, Frizzled receptors and co-receptors. These promiscuous binding and functional properties are thought to underlie the pivotal role Frizzled7 plays in embryonic developmental and stem cell function. Recent studies have identified that Frizzled7 is upregulated in diverse human cancers, and promotes proliferation, progression and invasion, and orchestrates cellular transitions that underscore cancer metastasis. Importantly, Frizzled7 is able to regulate Wnt signalling activity even in cancer cells which have mutations to down-stream signal transducers. In this review we discuss the various aspects of Frizzled7 signalling and function, and the implications these have for therapeutic targeting of Frizzled7 in cancer.

Comparative analysis of micro-RNAs in human papillomavirus-positive versus -negative oropharyngeal cancers

BACKGROUND

Oncogenic mechanisms of human papillomavirus (HPV)-positive oropharyngeal cancer are still poorly characterized. Analysis of their microRNA expression profile might provide valuable information.

METHODS

The microRNA expression profiles were analyzed by micro-arrays in 26 oropharyngeal cancers. A microRNA signature specific to HPV-status was identified by analyzing a learning/training set consisting of 16 oropharyngeal cancers. The robustness of this signature was further confirmed by blind case-by-case classification of a validation set composed of 10 independent tumors. Putative targeted molecular pathways were proposed using DIANA miRPath online software (http://microrna.gr/mirpath).

RESULTS

We have identified 25 miRNA signatures, which discriminates HPV16-positive oropharyngeal cancer from their HPV-negative counterparts. These 25 microRNAs play a potential role in Wnt and PI3K-pathways, cell-adhesion/cell-polarity, and the cytoskeleton regulation.

CONCLUSION

Our study contributes to a better understanding of pathogenic mechanisms involved in the development of HPV-positive oropharyngeal cancer and in the identification of potential therapeutic molecular targets. © 2016 Wiley Periodicals, Inc. Head Neck 38: 1708-1716, 2016.

The relationship between beta-catenin and apoptosis: A cytological and immunocytochemical examination

Disruption of the adhesive role of beta-catenin by caspases has been reported; however, the relationship between the Wnt/beta-catenin signaling pathway and apoptosis remains unclear. Therefore, we aimed to evaluate squamous epithelial cells in cervicovaginal smears by using cytological and immunocytochemical methods to observe changes in the presence and localization of beta-catenin during apoptosis, death receptor-, and mitochondria-mediated apoptosis. We investigated 224 cervicovaginal smears using the Papanicolaou method. Anti-beta-catenin and anti-cleaved caspase 3, 8, and 9 antibodies were used for immunocytochemical staining. Apoptotic cells were negative for beta-catenin. This showed that the Wnt/beta-catenin signaling pathway was inactive in apoptotic cells. However, beta-catenin showed intense positivity in the membrane, cytoplasm, and nucleus of non-apoptotic epithelial cells around these apoptotic cells. Therefore, the Wnt/beta-catenin signaling pathway was active in non-apoptotic epithelial cells, and this activity in non-apoptotic cells may have been induced by apoptotic cells. A highly significant association between the presence of death receptor-mediated apoptosis and the activity of the Wnt/beta-catenin signaling pathway was also found (P<0.001). In conclusion, the Wnt/beta-catenin signaling pathway was found to be inactive in apoptotic cells, but apoptotic cells may induce the Wnt/beta-catenin signaling pathway in non-apoptotic cells to compensate for a decrease in epithelial cells because of apoptosis in order to maintain epithelial tissue integrity.

Wnt-11 overexpression promoting the invasion of cervical cancer cells

Wnt-11 is a positive regulator of the Wnt signaling pathway, which plays a crucial role in carcinogenesis. However, Wnt-11 expression in cervical cancer has not been well investigated. The aim of this study was to investigate the role of Wnt-11 in cervical tumor proliferation and invasion. This study examined 24 normal cervical squamous epithelia, 29 cervical intraepithelial neoplasia (CIN), and 78 cervical cancer samples. The expression of Wnt-11 was investigated by immunohistochemistry and quantitative reverse transcription-polymerase chain reaction analysis. The expression of the high-risk human papilloma virus (HR-HPV) E6 oncoprotein was also investigated by immunohistochemistry. In addition, the expression of Wnt-11, HR-HPV E6, JNK-1, phosphorylated JNK-1(P-JNK1), and β-catenin was examined by western blot analysis following Wnt-11 knockdown or overexpression in HeLa or SiHa cells, respectively. The promotion of cervical cancer cell proliferation and invasion was investigated using the cell counting kit-8 and Matrigel invasion assay, respectively. Wnt-11 and HR-HPV E6 expression increased in a manner that corresponded with the progression of cervical cancer and was significantly correlated with the International Federation of Gynecology and Obstetrics cancer stage, lymph node metastasis, tumor size, and HPV infection. Wnt-11 protein expression was positively associated with HR-HPV E6 protein expression in all 78 cervical cancer samples (P < 0.001). Furthermore, Wnt-11 was positively associated with P-JNK1 expression and promoted cervical cancer cell proliferation and invasion. These observations suggest that the increased Wnt-11 expression observed in cervical cancer cells may lead to the phosphorylation and activation of JNK-1 and significantly promote tumor cell proliferation and cell migration/invasion through activation of the Wnt/JNK pathway. Consequently, Wnt-11 may serve as a novel target for cervical cancer therapy.

Precise Classification of Cervical Carcinomas Combined with Somatic Mutation Profiling Contributes to Predicting Disease Outcome

Introduction

Squamous cell carcinoma (SCC), adenocarcinoma (AC), and adenosquamous carcinoma (ASC) are the most common histological subtypes of cervical cancer. Differences in the somatic mutation profiles of these subtypes have been suggested. We investigated the prevalence of somatic hot-spot mutations in three well-defined cohorts of SCC, AC, and ASC and determined the additional value of mutation profiling in predicting disease outcome relative to well-established prognostic parameters.

Materials and Methods

Clinicopathological data were collected for 301 cervical tumors classified as SCC (n=166), AC (n=55), or ASC (n=80). Mass spectrometry was used to analyze 171 somatic hot-spot mutations in 13 relevant genes.

Results

In 103 (34%) tumors, 123 mutations were detected (36% in SCC, 38% in AC, and 28% in ASC), mostly in PIK3CA (20%) and KRAS (7%). PIK3CA mutations occurred more frequently in SCC than AC (25% vs. 11%, P=0.025), whereas KRAS mutations occurred more frequently in AC than SCC (24% vs. 3%, P<0.001) and ASC (24% vs. 3%, P<0.001). A positive mutation status correlated with worse disease-free survival (HR 1.57, P=0.043). In multivariate analysis, tumor diameter, parametrial infiltration, and lymph node metastasis, but not the presence of a somatic mutation, were independent predictors of survival.

Conclusion

Potentially targetable somatic mutations occurred in 34% of cervical tumors with different distributions among histological subtypes. Precise classification of cervical carcinomas in combination with mutation profiling is valuable for predicting disease outcome and may guide the development and selection of tumor-specific treatment approaches.

Expression of WNT genes in cervical cancer-derived cells: Implication of WNT7A in cell proliferation and migration

According to the multifactorial model of cervical cancer (CC) causation, it is now recognized that other modifications, in addition to Human papillomavirus (HPV) infection, are necessary for the development of this neoplasia. Among these, it has been proposed that a dysregulation of the WNT pathway might favor malignant progression of HPV-immortalized keratinocytes. The aim of this study was to identify components of the WNT pathway differentially expressed in CC vs. non-tumorigenic, but immortalized human keratinocytes. Interestingly, WNT7A expression was found strongly downregulated in cell lines and biopsies derived from CC. Restoration of WNT7A in CC-derived cell lines using a lentiviral gene delivery system or after adding a recombinant human protein decreases cell proliferation. Likewise, WNT7A silencing in non-tumorigenic cells markedly accelerates proliferation. Decreased WNT7A expression was due to hypermethylation at particular CpG sites. To our knowledge, this is the first study reporting reduced WNT7A levels in CC-derived cells and that ectopic WNT7A restoration negatively affects cell proliferation and migration.

HPV16 E6 and E6AP differentially cooperate to stimulate or augment Wnt signaling

The present study investigated the roles of E6 and E6AP in the Wnt pathway. We showed that E6 levels are markedly reduced in cells in which Wnt signaling is activated. Coexpression of wild-type or mutant E6AP (C820A) in Wnt-activated cells stabilized E6 and enhanced Wnt/β-catenin/TCF transcription. Expression of E6AP alone in nonstimulated cells elevated β-catenin level, promoted its nuclear accumulation, and activated β-catenin/TCF transcription. A knockdown of E6AP lowered β-catenin levels. Coexpression with E6 intensified the activities of E6AP. Further experiments proved that E6AP/E6 stabilize β-catenin by protecting it from proteasomal degradation. This function was dependent on the catalytic activity of E6AP, the kinase activity of GSK3β and the susceptibility of β-catenin to GSK3β phosphorylation. Thus, this study identified E6AP as a novel regulator of the Wnt signaling pathway, capable of cooperating with E6 in stimulating or augmenting Wnt/β-catenin signaling, thereby possibly contributing to HPV carcinogenesis.

miR-135a leads to cervical cancer cell transformation through regulation of β-catenin via a SIAH1-dependent ubiquitin proteosomal pathway

Human papillomaviruses (HPVs) is the principal etiological agent of cervical cancer (CC). However, exposure to the high-risk type HPV alone is insufficient for tumor formation, and additional factors are required for the HPV-infected cells to become tumorigenic. Dysregulated microRNAs (miRNAs) expression is frequently observed in cancer but their roles in the formation of CC have not been fully revealed. In this study, we compared the expression of miR-135a in laser capture microdissected cervical specimens and confirmed overexpression of the miRNA in malignant cervical squamous cell carcinoma compared with precancerous lesions. Transient force-expression of miR-135a induced growth in low-density culture, anchorage-independent growth, proliferation and invasion of a HPV-16 E6/E7-immortalized cervical epithelial cell line, NC104-E6/E7. The observed effects were due to the inhibitory action of miR-135a on its direct target seven in absentia homolog 1 (SIAH1) leading to upregulation of β-catenin/T cell factor signaling. miR-135a force-expression enhanced the growth of HeLa- and NC104-E6/E7-derived tumor in vivo. The effect of miR-135a could be partially nullified by SIAH1 force-expression. More importantly, the expression of SIAH1 and β-catenin correlated with that of miR-135a in precancerous and cancerous lesions of cervical biopsies. By comparing the tumorigenic activities of miR-135a in E6/E7 positive/negative cell lines and in NC104-E6/E7 with or without E6/E7 knockdown, we demonstrated that HPV E6/E7 proteins are prerequisite for miR-135a as an oncomiR. Taken together, miR-135a/SIAH1/β-catenin signaling is important in the transformation and progression of cervical carcinoma.

Reduced expression of DKK3 is associated with adverse clinical outcomes of uterine cervical squamous cell carcinoma

OBJECTIVE

The aim of this study was to assess the expression of DKK3 protein and its target, beta-catenin, in uterine cervical squamous cell carcinoma and to determine potential clinical correlations.

MATERIALS AND METHODS

Six carcinoma in-situ (CIS) tissues and 88 invasive cervical cancer tissues were included in the study. Twenty-two normal cervical tissues and one gastric cancer tissue were used as controls. The expression of DKK3 and beta-catenin proteins was evaluated by immunohistochemical analysis. Clinical and pathological parameters were obtained from medical records. Survival data were estimated using Kaplan-Meier estimates and compared with a log-rank test. Multivariate analysis was performed using the Cox regression method.

RESULTS

DKK3 was predominantly present in the cytoplasm. Beta-catenin was observed only on the cellular membrane of both normal and cancer cells in contrast to earlier reports, in which beta-catenin was localized to the cytoplasm and nucleus of cancer cells. The expressions of beta-catenin and DKK3 were not correlated. Three of 6 CIS (50%) and 57 of 88 invasive cancer specimens (64.8%) had lower DKK3 expression than normal controls. DKK3 expression was decreased in a stage-dependent manner (P = 0.021). The patients with low expression of DKK3 were older than those with high expression of DKK3 (P < 0.01). Moreover, the patients with low DKK3 expression had a significantly lower 5-year disease-free survival rate than those with high DKK3 expression (P = 0.026). A multivariate analysis showed that International Federation of Gynecology and Obstetrics clinical stage and parametrial involvement were independent prognostic factors.

CONCLUSION

Decreased DKK3 expression was associated with advanced International Federation of Gynecology and Obstetrics clinical stages and was predictive of lower disease-free survival in patients with cervical squamous cell carcinoma. DKK3 may be implicated in cervical carcinogenesis through a beta-catenin-independent mechanism.

Epigenetic modulation of signal transduction pathways in HPV-associated HNSCC

OBJECTIVE

Human papilloma virus (HPV) positive and HPV negative head and neck squamous cell cancer (HNSCC) are biologically distinct with a prognostic advantage for HPV positive patients compared to HPV negative cases. DNA promoter methylation is central to human diseases such as cancer, including HNSCC, with reported genome-wide hypomethylaton and promoter hypermethylation in HPV positive HNSCC tumors. The goal of this study was to identify differentially methylated genes in HPV positive versus HPV negative primary HNSCC genomes with clues to signaling networks.

STUDY DESIGN

Laboratory-based study.

SETTING

Primary care academic health care system.

SUBJECTS AND METHODS

DNA from 4 HPV positive and 4 HPV negative freshly frozen primary HNSCC were subject to comprehensive genome-wide methylation profiling. Differentially methylated gene lists were examined using the Signal Transduction Pathways (canonical) filter in the Genomatix Pathway System (GePS).

RESULTS

Twofold methylation differences were observed between HPV positive and HPV negative cases for 1168 genes. Pathway analysis applied to investigate the biological role of the 1168 differentially methylated genes revealed 8 signal transduction pathways forming a network of 66 genes, of which 62% are hypermethylated.

CONCLUSION

Our study reveals a predominant hypermethylation profile for genes in signal transduction pathways of HPV positive HNSCC tumor genomes. Because signaling events in the cell play a critical role in the execution of key biological functions, insights into how complex cellular signaling cascades and networks may be programmed in HNSCC are likely to be critical in the development of new biological agents designed to hit multiple targets.

Progeny of Lgr5-expressing hair follicle stem cell contributes to papillomavirus-induced tumor development in epidermis

Epidermal keratinocytes and hair follicle (HF) stem cells (SCs) expressing oncogenes are competent at developing squamous cell carcinomas (SCCs) in epidermis and HFs, respectively. To determine whether bulge and hair germ (HG) SCs from HF contribute to SCC generation at distant epidermis, the most frequent epidermal region where these lesions arise in human skin, we used a skin cancer mouse model expressing E6 and E7 oncoproteins from Human papillomavirus (HPV) 16 in SCs and basal keratinocytes. This previously described mouse model recapitulates the human skin papillomavirus-induced SCC pathology. We show that E6 and E7 expression promote the expansion of keratin 15 (K15)-expressing cells. These K15(+) aberrant cells exhibit some HGSC markers and diminished expression of Tcf3 and Sox9 hair SC specification genes, which are accumulated in HFs and mislocalized to interfollicular epidermis. Leucine-rich G-protein-coupled receptor 5 (Lgr5)-expressing SCs, localized in the bulge and HG, are the origin of the expanded K15(+) cell population. A large subset of the Lgr5(+) SC progeny, expressing K15 and P-cadherin, is aberrantly mobilized to the upper region of HFs and the epidermis, and accumulates at E6/E7-induced pre-neoplastic lesions and epidermal tumors. These findings indicate that aberrant accumulation of altered SCs in HFs and their subsequent migration to the epidermis contribute to HPV-induced tumor development.

Klotho inhibits the capacity of cell migration and invasion in cervical cancer

Aberrant activation of the Wnt/β-catenin signaling pathway is common in human cervical cancers. However, the mechanisms of Wnt activation in cervical cancer remain largely unknown. In the present study, we demonstrate that Klotho, a Wnt antagonist, is downregulated in invasive human cervical tumors and in a cell line we analyzed. Our data demonstrated that in vivo Klotho expression was not observed in invasive cervical carcinoma. In vitro restoration of Klotho expression in SiHa cells resulted in a decreased cell motility and invasiveness through upregulation of E-cadherin, downregulation of N-cadherin and reduced expression of MMP7 and -9. Ectopic expression of Klotho also reduced the expression of the epithelial-to-mesenchymal transition (EMT) transcription factors Slug and Twist. Furthermore, Klotho causes a significant inhibition of the Wnt/β-catenin pathway in cervical cancer cells, as supported by the expression of Wnt/β-catenin transcriptional target genes such as c-Myc and cyclin D1. Consequently, our findings demonstrate for the first time that Klotho regulates tumor invasion through the EMT process and provide novel mechanistic insights into the role of Klotho in cervical cancer progression and contribute to treatment for metastatic cervical cancer patients.

The E6 oncoprotein from HPV16 enhances the canonical Wnt/β-catenin pathway in skin epidermis in vivo

The contribution of the Wnt signaling pathway to human papilloma virus (HPV)-induced carcinogenesis is poorly understood. In high-grade dysplastic lesions that are caused by high-risk HPVs (HR-HPV), β-catenin is often located in the cell nucleus, which suggests that Wnt pathway may be involved in the development of HPV-related carcinomas. Most of the oncogenic potential of HR-HPVs resides on the PDZ-binding domain of E6 protein. We hypothesized that the PDZ-binding domain of the HPV16-E6 oncoprotein induces the nuclear accumulation of β-catenin due to its capacity to degrade PDZ-containing cellular targets. To test this hypothesis, we evaluated the staining pattern of β-catenin in the skin epidermis of transgenic mice expressing the full-length E6 oncoprotein (K14E6 mice) and measured LacZ gene expression in K14E6 mice that were crossed with a strain expressing LacZ that was knocked into the Axin2 locus (Axin2(+/LacZ) mice). Here, we show that the E6 oncoprotein enhances the nuclear accumulation of β-catenin, the accumulation of cellular β-catenin-responsive genes, and the expression of LacZ. None of these effects were observed when a truncated E6 oncoprotein that lacks the PDZ-binding domain was expressed alone (K14E6ΔPDZ mice) or in combination with Axin2(+/LacZ). Conversely, cotransfection with either E6 or E6ΔPDZ similarly enhanced canonical Wnt signaling in short-term in vitro assays that used a luciferase Wnt/β-catenin/TCF-dependent promoter. We propose that the activation of canonical Wnt signaling could be induced by the HPV16-E6 oncoprotein; however, the participation of the E6 PDZ-binding domain seems to be important in in vivo models only.

Beta-catenin accelerates human papilloma virus type-16 mediated cervical carcinogenesis in transgenic mice

Human papilloma virus (HPV) is the principal etiological agent of cervical cancer in women, and its DNA is present in virtually all of these tumors. However, exposure to the high-risk HPV types alone is insufficient for tumor development. Identifying specific collaborating factors that will lead to cervical cancer remains an unanswered question, especially because millions of women are exposed to HPV. Our earlier work using an in vitro model indicated that activation of the canonical Wnt pathway in HPV-positive epithelial cells was sufficient to induce anchorage independent growth. We therefore hypothesized that constitutive activation of this pathway might function as the "second hit." To address this possibility, we developed two double-transgenic (DT) mouse models, K14-E7/ΔN87βcat and K14-HPV16/ΔN87βcat that express either the proteins encoded by the E7 oncogene or the HPV16 early region along with constitutively active β-catenin, which was expressed by linking it to the keratin-14 (K14) promoter. We initiated tumor formation by treating all groups with estrogen for six months. Invasive cervical cancer was observed in 11% of the K14-ΔN87βcat mice, expressing activated β-catenin and in 50% of the animals expressing the HPV16 E7 oncogene. In double-transgenic mice, coexpression of β-catenin and HPV16 E7 induced invasive cervical cancer at about 7 months in 94% of the cases. We did not observe cervical cancer in any group unless the mice were treated with estrogen. In the second model, K14-HPV16 mice suffered cervical dysplasias, but this phenotype was not augmented in HPV16/ΔN87βcat mice. In summary, the phenotypes of the K14-E7/ΔN87βcat mice support the hypothesis that activation of the Wnt/β-catenin pathway in HPV-associated premalignant lesions plays a functional role in accelerating cervical carcinogenesis.

Wnt inhibitory factor 1 induces apoptosis and inhibits cervical cancer growth, invasion and angiogenesis in vivo

Aberrant activation of Wingless-type (Wnt)/β-catenin signaling is widespread in human cervical cancer. However, the underlying mechanisms of Wnt activation and the therapeutic potential of Wnt inhibition remain largely unknown. Here, we demonstrate that the Wnt inhibitory factor 1 (WIF1), a secreted Wnt antagonist, is downregulated in all human primary cervical tumors and cell lines analyzed. Our data reveal that WIF1 downregulation occurs due to promoter hypermethylation and is an early event in cervical oncogenesis. WIF1 re-expression upon 5-aza-2'-deoxycytidine treatment or WIF1 gene transfer induces significant apoptosis and G(2)/M arrest, and inhibits cervical cancer cell proliferation in vitro. Consistent with this, treatment of established mice tumor xenografts with peritumoral WIF1 gene transfer results in a significant inhibition of cancer growth and invasion. WIF1 treatment causes a significant decrease in intracellular WNT1 and TCF-4 proteins revealing novel Wnt-regulatory mechanisms. Thus, WIF1 causes a major cellular re-distribution of β-catenin and a significant inhibition of the Wnt/β-catenin pathway in tumor cells, as documented by a remarkable reversion in the expression of Wnt/β-catenin transcriptional target genes (E-cadherin, c-Myc, cyclin D1, CD44 and VEGF). Consequently, multiple critical events in tumor progression and metastasis such as cell proliferation, angiogenesis and invasion were inhibited by WIF1. In addition, WIF1 modulated the expression of specific anti-apoptotic and apoptotic proteins, thereby inducing significant apoptosis in vivo. Our findings demonstrate for the first time that WIF1 downregulation by epigenetic gene silencing is an important mechanism of Wnt activation in cervical oncogenesis. Of major clinical relevance, we show that peritumoral WIF1 gene transfer reduces not only cancer growth but also invasion in well-established tumors. Therefore, our data provide novel mechanistic insights into the role of WIF1 in cervical cancer progression, and the important preclinical validation of WIF1 as a potent drug target in cervical cancer treatment.

Diverse mechanisms for activation of Wnt signalling in the ovarian tumour microenvironment

Wnt signalling pathways have been shown to play key roles in both normal development and tumorigenesis. Progression of many human cancers is associated with defined mutations in Wnt pathway components that result in dysregulated β-catenin-mediated gene transcription. Although Wnt pathway mutations are rare in epithelial ovarian cancer (with the exception of the endometrioid histotype), accumulating evidence supports a role for Wnt signalling in ovarian tumorigenesis in the absence of genetic mutations. The present review summarizes evidence in support of activated Wnt signalling in ovarian tumours and discusses alternative mechanisms for Wnt pathway activation in the ovarian tumour microenvironment.

Promoter methylation analysis of WNT/β-catenin signaling pathway regulators to detect adenocarcinoma or its precursor lesion of the cervix

OBJECTIVE

Cervical adenocarcinoma (AdCA) and adenocarcinoma in situ (ACIS) are frequently missed in cytology-based screening programs. Testing for high-risk human papillomavirus (hrHPV) improves their detection, but novel ACIS/AdCA specific biomarkers are needed to increase specificity for these lesions. Novel markers may be deduced from the WNT/β-catenin signaling pathway, which is aberrantly activated during cervical carcinogenesis.

METHODS

Promoter methylation of nine WNT-antagonists (APC, AXIN2, DKK3, SFRP2, SFRP4, SFRP5, SOX17, WIF1 and WNT5A) was evaluated by methylation-specific PCR (MSP) on a small series of cervical tissue specimens, including AdCA and SCC. To estimate the diagnostic potential of the genes most frequently methylated in AdCA an extended series of ACIS, AdCA, CIN3, SCC, and normal cervical tissue specimens (n=131) as well as 49 hrHPV-positive scrapings were analyzed by quantitative MSP (qMSP).

RESULTS

The frequency of DKK3 and SFRP2 methylation was significantly higher in AdCA compared to SCC, i.e. 82% vs. 18% (p<0.01) and 84% vs. 39% (p<0.01), respectively, while SOX17 methylation frequency was significantly higher in SCC than AdCA, i.e. 89% vs. 62% (p<0.05). Methylation of WIF1 was common in both AdCA (71%) and SCC (54%). Methylation frequencies ranged from 4% to 55% in precursor lesions and from 0% to 5% in normal biopsies. When tested on HPV-positive cervical scrapings, qMSP of the best ACIS/AdCA discriminator genes, i.e. DKK3 and SFRP2, detected all women with underlying ACIS/AdCA, compared to 3% of controls.

CONCLUSIONS

DKK3 and SFRP2 promoter methylation is highly indicative for the presence of ACIS/AdCA, thereby providing promising triage markers for HPV-positive women at risk of ACIS/AdCA.

The anti-aging gene KLOTHO is a novel target for epigenetic silencing in human cervical carcinoma

BACKGROUND

Klotho was originally characterized as an anti-aging gene that predisposed Klotho-deficient mice to a premature aging-like syndrome. Recently, KLOTHO was reported to function as a secreted Wnt antagonist and as a tumor suppressor. Epigenetic gene silencing of secreted Wnt antagonists is considered a common event in a wide range of human malignancies. Abnormal activation of the canonical Wnt pathway due to epigenetic deregulation of Wnt antagonists is thought to play a crucial role in cervical tumorigenesis. In this study, we examined epigenetic silencing of KLOTHO in human cervical carcinoma.

RESULTS

Loss of KLOTHO mRNA was observed in several cervical cancer cell lines and in invasive carcinoma samples, but not during the early, preinvasive phase of primary cervical tumorigenesis. KLOTHO mRNA was restored after treatment with either the DNA demethylating agent 2'-deoxy-5-azacytidine or histone deacetylase inhibitor trichostatin A. Methylation-specific PCR and bisulfite genomic sequencing analysis of the promoter region of KLOTHO revealed CpG hypermethylation in non-KLOTHO-expressing cervical cancer cell lines and in 41% (9/22) of invasive carcinoma cases. Histone deacetylation was also found to be the major epigenetic silencing mechanism for KLOTHO in the SiHa cell line. Ectopic expression of the secreted form of KLOTHO restored anti-Wnt signaling and anti-clonogenic activity in the CaSki cell line including decreased active beta-catenin levels, suppression of T-cell factor/beta-catenin target genes, such as c-MYC and CCND1, and inhibition of colony growth.

CONCLUSIONS

Epigenetic silencing of KLOTHO may occur during the late phase of cervical tumorigenesis, and consequent functional loss of KLOTHO as the secreted Wnt antagonist may contribute to aberrant activation of the canonical Wnt pathway in cervical carcinoma.

HPV16 E6 augments Wnt signaling in an E6AP-dependent manner

In this study we investigated the effect of HPV16 E6 on the Wnt/beta-catenin oncogenic signaling pathway. Luciferase reporter assays indicated that ectopically expressed E6 significantly augmented the Wnt/beta-catenin/TCF-dependent signaling response in a dose-dependent manner. This activity was independent of the ability of E6 to target p53 for degradation or bind to the PDZ-containing E6 targets. Epistasis experiments suggested that the stimulatory effect is independent of GSK3beta or APC. Coexpression, half-life determination, cell fractionation and immunofluorescence analyses indicated that E6 did not alter the expression levels, stability or cellular distribution of beta-catenin. Further experiments using E6 mutants defective for E6AP binding and E6AP knockdown cells indicated the absolute requirement of the ubiquitin ligase E6AP for enhancement of the Wnt signal by E6. Thus, this study suggests a role for the E6/E6AP complex in augmentation of the Wnt signaling pathway which may contribute to HPV induced carcinogenesis.

Clinical significance and prognostic value of serum Dickkopf-1 concentrations in patients with lung cancer

BACKGROUND

Dickkopf-1 (DKK1), a secreted protein, is known as a negative regulator of the Wnt signaling pathway, which has been implicated in the development of several types of cancers. Clinical significance of serum DKK1 in lung cancer remains to be determined.

METHODS

A novel time-resolved immunofluorometric assay was developed. By use of this method, we investigated the serum concentrations of DKK1 in 592 patients with malignancies, 72 patients with benign lung disease, and 120 healthy controls. Serum cytokeratin 19 fragment and neuron-specific enolase values were obtained.

RESULTS

Serum DKK1 concentrations were significantly higher in patients with lung cancer than in patients with other malignant tumors or benign lung diseases and healthy controls. Serum concentrations of DKK1 were decreased significantly in groups of patients with gastric cancer, colorectal cancer, ovarian cancer, and cervical adenocarcinoma compared with healthy controls. Application of both DKK1 and cytokeratin 19 fragment increased sensitivity, correctly identifying 89.6% of the non-small cell lung cancer patients as positive. The use of both DKK1 and neuron-specific enolase increased sensitivity to detect small cell lung cancer to 86.2%. DKK1 concentrations increased with stage, tumor class, and presence of lymph node and distant metastases, regardless of histology and patient age and sex. Patients with a DKK1 concentration of 22.6 microg/L or higher had a statistically significantly diminished survival compared with patients whose DKK1 values were lower.

CONCLUSIONS

DKK1 was preferentially expressed in lung cancer. Increasing concentrations of DKK1were significantly associated with tumor progression and decreased survival in patients with lung cancer. .

SFRP1 and SFRP2 suppress the transformation and invasion abilities of cervical cancer cells through Wnt signal pathway

OBJECTIVES

Aberrant activation of the Wnt/beta-catenin signaling pathway is common in human cancers, including cervical cancer. The secreted frizzled-related proteins (SFRPs) function as Wnt antagonists and play important implications in carcinogenesis. Recently, we have shown that SFRP1 and SFRP2 are frequently downregulated through promoter hypermethylation. However, the function of SFRP1 and SFRP2 in cervical cancer remains unclear.

METHODS

To improve our understanding of the role of SFRP1 and SFRP2 in cervical cancer cells, we use overexpression or shRNA approach in cervical cancer cell lines.

RESULTS

Restoration of the expression of SFRP1 and SFRP2 attenuated Wnt signaling in CaSki cells, decreased abnormal accumulation of free beta-catenin in the nucleus, and suppressed cancer cell growth. In addition, different statuses of beta-catenin accumulation in the cytoplasm of CaSki or HeLa3rd cells were observed, suggesting that different Wnt pathways are executed. Furthermore, we demonstrated that SFRP1 and SFRP2 enhance the expression of the epithelial marker E-cadherin, through inhibition of the expression of SLUG, TWIST and SNAIL, three transcription factors involved in the epithelial mesenchymal transition (EMT) program. Finally, in a xenograft animal model, we showed that SFRP1 suppresses tumorigenicity of cancer cells in vivo.

CONCLUSIONS

Taken together, these data strongly suggest that epigenetic silencing of SFRP genes leads to oncogenic activation of the Wnt pathway and contributes to cervical cancer progression through the EMT program.

Promoter methylation of SFRPs gene family in cervical cancer

OBJECTIVES

Oncogenic activation of the Wnt/beta-catenin signaling pathway is common in human cancers, including cervical cancer. The secreted frizzled-related proteins (SFRPs) function as negative regulators of Wnt signaling and play an important role in carcinogenesis. Frequent promoter hypermethylation of SFRPs has been identified in human cancers; however, the precise role of SFRPs in cervical cancer is not clear.

METHODS

The methylation status of SFRPs gene family was analyzed in two cervical cancer cell lines and a full spectrum of cervical neoplasia, including 45 low-grade squamous intraepithelial lesions (LSIL), 49 high-grade squamous intraepithelial lesions (HSIL), 109 squamous cell carcinomas (SCC), and 45 normal controls.

RESULTS

The SFRP1 promoter was hypermethylated in 33.9% of SCC, 8.2% of HSIL, 2.2% of LSIL, but not in normal tissues. The SFRP2 promoter was hypermethylated in 80.7% of SCC, 16.3% of HSIL, 15.6% LSIL and 4.4% normal tissues. The SFRP4 promoter was hypermethylated in 67.9% of SCC, 36.7% of HSIL, 4.4% of LSIL, but not in normal tissues. The SFRP5 promoter was hypermethylated in 10.1% of SCC, 4.1% of HSIL, 13.3% of LSIL and 4.4% normal tissues. The frequency of SFRP1, SFRP2 and SFRP4 promoter methylation in tumors was significantly higher than in normal, LSIL, and HSIL samples (P<0.0001). SFRP5 methylation was significantly different in patients with or without lymph-node metastases (0% vs 15.2%, respectively, P<0.05).

CONCLUSIONS

Our data suggest that promoter hypermethylation of SFRP1, SFRP2 and SFRP4 is associated with cervical carcinogenesis, which could be used for molecular screening of cervical neoplasias in future.

Second hit in cervical carcinogenesis process: involvement of wnt/beta catenin pathway

The Human papillomavirus plays an important role in the initiation and progression of cervical cancer. However, it is a necessary but not sufficient cause to develop invasive carcinoma; hence, other factors are required in the pathogenesis of this malignancy. In this review we explore the hypothesis of the deregulation of wnt/beta-catenin signaling pathway as a "second hit" required to develop cervical cancer.

Epigenetic silencing of the WNT antagonist DICKKOPF-1 in cervical cancer cell lines

OBJECTIVE

Our study was designed to demonstrate that DICKKOPF-1 (DKK-1), encoding a secreted Wnt antagonist, is transcriptionally repressed by epigenetic alterations in cervical carcinoma cell lines.

METHODS

Methylation-specific PCR for 8 human cervical cancer cell lines and bisulfite sequencing for 4 cell lines exhibiting significant difference in methylation levels were used to determine CpG-island methylation status at the 5'-end region of DKK-1. The chromatin immunoprecipitation assay was performed to determine whether HeLa cells recruit histone deacetylation for DKK-1 silencing.

RESULTS

Two out of eight cervical cancer cell lines examined were found to be regulated by independent epigenetic inactivation mechanisms; promoter CpG hypermethylation constitutes a major epigenetic alteration in SNU-703, and histone deacetylation in HeLa cells.

CONCLUSION

Our study suggests that cervical cancer cell lines exploit cell line-dependent, differential epigenetic mechanisms for DKK-1 silencing.

Association of p53 Arg72Pro polymorphism and beta-catenin accumulation in mycosis fungoides

BACKGROUND

Aberrant activation of beta-catenin contributes to the onset of a variety of tumours. There are many tumours that display beta-catenin accumulation in the absence of mutations in its gene. Recently, abnormal accumulation of wild-type beta-catenin has been associated with mutational inactivation of the p53 tumour suppressor.

OBJECTIVES

To investigate the potential role of p53 and its homologue p63 in beta-catenin deregulation and to correlate this with disease outcome.

METHODS

We analysed a panel of 24 samples of mycosis fungoides (MF), the most frequent manifestation of cutaneous T-cell lymphoma (CTCL), for beta-catenin, p53 and p63 protein expression by immunohistochemistry. Based on the immunostaining results for beta-catenin protein, 11 positive cases were selected for laser microdissection, genomic DNA isolation and subsequent mutation analysis of beta-catenin exon 3 and p53 exons 4-8.

RESULTS

Our findings revealed overexpression of beta-catenin, p53 and p63 in 46%, 38% and 17% of cases, respectively. The number of p53-positive cases of MF was significantly higher (P < 0.05) in the beta-catenin-positive group (73%). Sequence analysis demonstrated that wild-type beta-catenin accumulation in MF is not associated with mutational inactivation of the p53 gene and, more importantly, our data provide evidence that a common polymorphic form of p53 (Arg72Pro) is significantly associated with beta-catenin overexpression (P < 0.05). No significant differences in the three genotypes were observed between the CTCL cases and the control group, demonstrating that Arg72Pro polymorphism of the p53 gene is not associated with the risk of developing cutaneous lymphomas (P > 0.05).

CONCLUSIONS

We found an association of beta-catenin and p53 overexpression without detection of structural alteration in the genes, suggesting that p53 mutation is not an important mechanism for beta-catenin activation in primary CTCL. Additionally, we speculate that the p53 codon 72 polymorphism may influence negative feedback control involving beta-catenin and p53.