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

Combined Inhibition of Indolamine-2,3-Dioxygenase 1 and C-X-C Chemokine Receptor Type 2 Exerts Antitumor Effects in a Preclinical Model of Cervical Cancer

Cervical cancer is a public health problem diagnosed in advanced stages, and its main risk factor is persistent high-risk human papillomavirus infection. Today, it is necessary to study new treatment strategies, such as immunotherapy, that use different targets of the tumor microenvironment. In this study, the K14E7E2 mouse was used as a cervical cancer model to evaluate the inhibition of indolamine-2,3-dioxygenase 1 (IDO-1) and C-X-C chemokine receptor type 2 (CXCR-2) as potential anti-tumor targets. DL-1MT and SB225002 were administered for 30 days in two regimens (R1 and R2) based on combination and single therapy approaches to inhibit IDO-1 and CXCR-2, respectively. Subsequently, the reproductive tracts were resected and analyzed to determine the tumor areas, and IHCs were performed to assess proliferation, apoptosis, and CD8 cellular infiltration. Our results revealed that combined inhibition of IDO-1 and CXCR-2 significantly reduces the areas of cervical tumors (from 196.0 mm2 to 58.24 mm2 in R1 and 149.6 mm2 to 52.65 mm2 in R2), accompanied by regions of moderate dysplasia, decreased papillae, and reduced inflammation. Furthermore, the proliferation diminished, and apoptosis and intra-tumoral CD8 T cells increased. In conclusion, the combined inhibition of IDO-1 and CXCR-2 is helpful in the antitumor response against preclinical cervical cancer.

Multi-omics characterization of silent and productive HPV integration in cervical cancer

Cervical cancer (CC) that is caused by high-risk human papillomavirus (HPV) remains a significant public health problem worldwide. HPV integration sites can be silent or actively transcribed, leading to the production of viral-host fusion transcripts. Herein, we demonstrate that only productive HPV integration sites were nonrandomly distributed across both viral and host genomes, suggesting that productive integration sites are under selection and likely to contribute to CC pathophysiology. Furthermore, using large-scale, multi-omics (clinical, genomic, transcriptional, proteomic, phosphoproteomic, and single-cell) data, we demonstrate that tumors with productive HPV integration are associated with higher E6/E7 proteins and enhanced tumor aggressiveness and immunoevasion. Importantly, productive HPV integration increases from carcinoma in situ to advanced disease. This study improves our understanding of the functional consequences of HPV fusion transcripts on the biology and pathophysiology of HPV-driven CCs, suggesting that productive HPV integration should be evaluated as an indicator of high risk for progression to aggressive cancers.

Mechanistic Contributions of lncRNAs to Cellular Signaling Pathways Crucial to the Lifecycle of Human Papillomaviruses

Papillomaviruses are ubiquitous epitheliotropic viruses with double-stranded circular DNA genomes of approximately 8000 base pairs. The viral life cycle is somewhat unusual in that these viruses can establish persistent infections in the mitotically active basal epithelial cells that they initially infect. High-level viral genome replication ("genome amplification"), the expression of capsid proteins, and the formation of infectious progeny are restricted to terminally differentiated cells where genomes are synthesized at replication factories at sites of double-strand DNA breaks. To establish persistent infections, papillomaviruses need to retain the basal cell identity of the initially infected cells and restrain and delay their epithelial differentiation program. To enable high-level viral genome replication, papillomaviruses also need to hold the inherently growth-arrested terminally differentiated cells in a replication-competent state. To provide ample sites for viral genome synthesis, they target the DNA damage and repair machinery. Studies focusing on delineating cellular factors that are targeted by papillomaviruses may aid the development of antivirals. Whilst most of the current research efforts focus on protein targets, the majority of the human transcriptome consists of noncoding RNAs. This review focuses on one specific class of noncoding RNAs, long noncoding RNAs (lncRNAs), and summarizes work on lncRNAs that may regulate the cellular processes that are subverted by papillomavirus to enable persistent infections and progeny synthesis.

Nocardia rubra cell-wall skeleton influences the development of cervical carcinoma by promoting the antitumor effect of macrophages and dendritic cells

Background

As an immune enhancer, Nocardia rubra cell‐wall skeleton (Nr‐CWS) has been used to treat persistent human papillomavirus infection and cervical precancerous lesions. However, it is still unclear whether it can be used to treat cervical carcinoma.

Methods

In our study, the aim was to determine whether Nr‐CWS affects the apoptosis of cervical carcinoma cells by enhancing the antitumor effect of dendritic cells and macrophages in vivo and in vitro.

Results

The experimental results showed that Nr‐CWS can promote the activity of dendritic cells and macrophages and reduce their apoptosis. It also increased the cytokines IL‐6, IL‐12, TNF‐ɑ, and IL‐1β secreted by dendritic cells and macrophages and reduced their PD‐L1 expression. In vitro, Nr‐CWS inhibited the proliferation, colony forming ability of HeLa and SiHa cervical carcinoma cell lines cultured with macrophages, and more cells were blocked in G2/M phase. Nr‐CWS promoted TNF‐ɑ/TNFR1/caspase‐8‐mediated apoptosis by increasing macrophages secretion of TNF‐ɑ and inhibited cell migration and invasion regulated by the WNT/β‐catenin‐EMT pathway. Nr‐CWS also reduced the expression of the cervical carcinoma genes E6 and E7 thereby increasing expression of p53 gene and decreasing expression of PD‐L1 gene. In vivo, Nr‐CWS inhibited tumor growth and decreased the expression of E6, E7, PD‐L1, P16, Ki67, and PCNA in tumors.

Conclusions

Therefore, our results suggest that Nr‐CWS can promote apoptosis of cervical carcinoma cells by enhancing the antitumor effect of dendritic cells and macrophages.

Reduced MAGI3 level by HPV18E6 contributes to Wnt/β-catenin signaling activation and cervical cancer progression

Human papillomavirus type 18 (HPV18) has high carcinogenic power in invasive cervical cancer (ICC) development. However, the underlying mechanism remains elusive. The carcinogenic properties of HPV18 require the PDZ‐binding motif of its E6 oncoprotein (HPV18 E6) to degrade its target PSD95/Dlg/ZO‐1 (PDZ) proteins. In this study, we demonstrated that the PDZ protein membrane‐associated guanylate kinase, WW and PDZ domain containing 3 (MAGI3) inhibited the Wnt/β‐catenin pathway, and subsequently cervical cancer (CC) cell migration and invasion, via decreasing β‐catenin levels. By reducing MAGI3 protein levels, HPV18 E6 promoted CC cell migration and invasion through activation of Wnt/β‐catenin signaling. Furthermore, HPV18 rather than HPV16 was preferentially associated with the downregulation of MAGI3 and activation of the Wnt/β‐catenin pathway in CC. These findings shed light on the mechanism that gives HPV18 its high carcinogenic potential in CC progression.

Expression and Role of E-Cadherin, β-Catenin, and Vimentin in Human Papillomavirus-Positive and Human Papillomavirus-Negative Oropharyngeal Squamous Cell Carcinoma

Oropharyngeal squamous cell carcinoma (OPSCC) is subclassified by the World Health Organization into two different entities: human papillomavirus (HPV)-positive and HPV-negative tumors. HPV infection promotes the epithelial-to-mesenchymal transition (EMT) and transformation of keratinocyte stem cells into cancer stem cells. EMT is a crucial process in the carcinogenesis of epithelial-derived malignancies, and we aimed to study the role of its markers in OPSCC. This study consists of 202 consecutive OPSCC patients diagnosed and treated with curative intent. We examined E-cadherin, β-catenin, and vimentin expression using immunohistochemistry and compared these with tumor and patient characteristics and treatment outcome. We found that the cell-membranous expression of β-catenin was stronger in HPV-positive than in HPV-negative tumors, and it was stronger in the presence of regional metastasis. The stromal vimentin expression was stronger among HPV-positive tumors. A high E-cadherin expression was associated with tumor grade. No relationship between these markers and survival emerged. In conclusion, β-catenin and vimentin seem to play different roles in OPSCC: the former in the tumor tissue itself, and the latter in the tumor stroma. HPV infection may exploit the β-catenin and vimentin pathways in carcinogenic process. More, β-catenin may serve as a marker for the occurrence of regional metastasis:

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.

E7 oncoprotein from human papillomavirus 16 alters claudins expression and the sealing of epithelial tight junctions

Tight junctions (TJs) are cell-cell adhesion structures frequently altered by oncogenic transformation. In the present study the role of human papillomavirus (HPV) 16 E7 oncoprotein on the sealing of TJs was investigated and also the expression level of claudins in mouse cervix and in epithelial Madin-Darby Canine Kidney (MDCK) cells. It was found that there was reduced expression of claudins -1 and -10 in the cervix of 7-month-old transgenic K14E7 mice treated with 17β-estradiol (E₂), with invasive cancer. In addition, there was also a transient increase in claudin-1 expression in the cervix of 2-month-old K14E7 mice, and claudin-10 accumulated at the border of cells in the upper layer of the cervix in FvB mice treated with E₂, and in K14E7 mice treated with or without E₂. These changes were accompanied by an augmented paracellular permeability of the cervix in 2- and 7-monthold FvB mice treated with E₂, which became more pronounced in K14E7 mice treated with or without E₂. In MDCK cells the stable expression of E7 increased the space between adjacent cells and altered the architecture of the monolayers, induced the development of an acute peak of transepithelial electrical resistance accompanied by a reduced expression of claudins -1, -2 and -10, and an increase in claudin-4. Moreover, E7 enhances the ability of MDCK cells to migrate through a 3D matrix and induces cell stiffening and stress fiber formation. These observations revealed that cell transformation induced by HPV16 E7 oncoprotein was accompanied by changes in the pattern of expression of claudins and the degree of sealing of epithelial TJs.

Wnt Signaling in Gynecologic Malignancies

Gynecologic malignancies, including ovarian cancer, endometrial cancer, and cervical cancer, affect hundreds of thousands of women worldwide every year. Wnt signaling, specifically Wnt/β-catenin signaling, has been found to play an essential role in many oncogenic processes in gynecologic malignancies, including tumorigenesis, metastasis, recurrence, and chemotherapy resistance. As such, the Wnt/β-catenin signaling pathway has the potential to be a target for effective treatment, improving patient outcomes. In this review, we discuss the evidence supporting the importance of the Wnt signaling pathways in the development, progression, and treatment of gynecologic malignancies.

Cancer cell-intrinsic function of CD177 in attenuating β-catenin signaling

Aiming to identify immune molecules with a novel function in cancer pathogenesis, we found the cluster of differentiation 177 (CD177), a known neutrophil antigen, to be positively correlated with relapse-free (RFS), metastasis-free (MFS) or overall survival (OS) in breast cancer. Additionally, CD177 expression is correlated with good prognosis in several other solid cancers including prostate, cervical, and lung. Focusing on breast cancer, we found that CD177 is expressed in normal breast epithelial cells and is significantly reduced in invasive cancers. Loss of CD177 leads to hyperproliferative mammary epithelium and contributes to breast cancer pathogenesis. Mechanistically, we found that CD177-deficiency is associated with an increase in β-Catenin signaling. Here we identified CD177 as a novel regulator of mammary epithelial proliferation and breast cancer pathogenesis likely via the modulation of Wnt/β-Catenin signaling pathway, a key signaling pathway involved in multiple cancer types.

Comparative Gene Expression Profiling of Tobacco-Associated HPV-Positive versus Negative Oral Squamous Carcinoma Cell Lines

Background: HPV-positive oral squamous cell carcinomas (OSCCs) are specific biological and clinical entities, characterized by a more favorable prognosis compared to HPV-negative OSCCs and occurring generally in non-smoking and non-drinking younger individuals. However, poor information is available on the molecular and the clinical behavior of HPV-positive oral cancers occurring in smoking/drinking subjects. Thus, this study was designed to compare, at molecular level, two OSCC cell lines, both derived from drinking and smoking individuals and differing for presence/absence of HPV infection. Methods: HPV-negative UPCI-SCC-131 and HPV16-positive UPCI-SCC-154 cell lines were compared by whole genome gene expression profiling and subsequently studied for activation of Wnt/βCatenin signaling pathway by the expression of several Wnt-target genes, βCatenin intracellular localization, stem cell features and miRNA let-7e. Gene expression data were validated in head and neck squamous cell carcinoma (HNSCC) public datasets. Results: Gene expression analysis identified Wnt/βCatenin pathway as the unique signaling pathway more active in HPV-negative compared to HPV-positive OSCC cells and this observation was confirmed upon evaluation of several Wnt-target genes (i.e., Cyclin D1, Cdh1, Cdkn2a, Cd44, Axin2, c-Myc and Tcf1). Interestingly, HPV-negative OSCC cells showed higher levels of total βCatenin and its active form, increase of its nuclear accumulation and more prominent stem cell traits. Furthermore, miRNA let-7e was identified as potential upstream regulator responsible for the downregulation of Wnt/βCatenin signaling cascade since its silencing in UPCI-SCC-154 cell resulted in upregulation of Wnt-target genes. Finally, the analysis of two independent gene expression public datasets of human HNSCC cell lines and tumors confirmed that Wnt/βCatenin pathway is more active in HPV-negative compared to HPV-positive tumors derived from individuals with smoking habit. Conclusions: These data suggest that lack of HPV infection is associated with more prominent activation of Wnt/βCatenin signaling pathway and gain of stem-like traits in tobacco-related OSCCs.

Association of iRhom1 and iRhom2 expression with prognosis in patients with cervical cancer and possible signaling pathways

Several proteins in the iRhom family function as oncogenic regulators in certain cancers. However, the function of these proteins in cervical cancer (CC) is unknown. The relationship of iRhom1 and iRhom2 expression with the clinicopathological features and prognosis of patients with CC was investigated, and their possible molecular mechanisms were examined using in vitro experiments. The expression of iRhom1 and iRhom2 in CC samples of 83 patients was determined by immunohistochemistry (IHC), and the associations of their expression with the clinicopathological features of patients were determined. The relationship of iRhom1, iRhom2, and Ki-67 expression with survival rates was determined using Kaplan-Meier analysis and Cox regression analyses. HeLa cells were analyzed using MTT assays, cell cycle analysis, and apoptosis assays. The results revealed that CC tissues had higher levels of iRhom1 and iRhom2 than adjacent normal tissues. Increased expression of iRhom1, iRhom2, and K-i67 was significantly associated with tumor stage, size, and parametrium invasion. High expression of iRhom1, iRhom2 and Ki-67 was correlated with poor outcomes. Cancer stage and iRhom2 expression were independent prognostic indicators of CC. Knockdown of iRhom1 and iRhom2 in HeLa cells inhibited cell proliferation, promoted the G1 phase and relieved S-phase arrest, and induced apoptosis. Genomic microarray analysis indicated that iRhom2 knockdown altered several pathways with roles in oncogenesis, including the expression of five genes in the Wnt/β-catenin pathway. Western blotting in HeLa cells revealed that iRhom1 knockdown significantly suppressed the expression of β-catenin, Myc, p-EGFR and TGFBR2, and increased the expression of FAS; iRhom2 knockdown significantly suppressed the expression of β-catenin, GSK3β, p-EGFR and Myc. These results were consistent with the genomic microarray data. Collectively, the results indicated that iRhom1 and iRhom2 may function as oncogenes in CC and are potential therapeutic targets.

NHERF1 inhibits beta-catenin-mediated proliferation of cervical cancer cells through suppression of alpha-actinin-4 expression

Cervical cancer is one of the most lethal types of cancer in female. Aberrant activation of Wnt/β-catenin signaling pathway has been found to be involved in cervical cancer development and progression, whereas the underlying molecular mechanisms remain poorly understood. The present study showed that NHERF1 was a novel gene associated with both cell proliferation and Wnt signaling pathway in cervical cancer by analysis of differential gene expression and gene cluster for the cervical cancer specimens from GEO data sets. It was further demonstrated in cellular study that NHERF1 inhibition of cervical cancer cell proliferation through Wnt/β-catenin signaling was dependent on α-actinin-4 (ACTN4) expression. A negative association between NHERF1 expression and levels of ACTN4 and β-catenin was found in mouse xenograft model and cervical cancer specimens. Low levels of NHERF1 in cervical cancer specimens were found to associate with activation of cell proliferation and Wnt/β-catenin signaling by gene set enrichment analysis, and also were an independent predictive factor for worse prognosis of cervical cancer patients by Cox regression analysis. These findings demonstrate that NHERF1 inhibits Wnt signaling-mediated proliferation of cervical cancer via suppression of ACTN4, and NHERF1 downregulation may contribute to the progression of cervical cancer. These findings may also shed some lights for understanding the underlying mechanisms of cisplatin resistance and worse prognosis of HPV-inactive cervical cancer patients.

Wnt signaling in cervical cancer?

Cervical cancer (CC) is the second most common malignant cancer in women. CC is difficult to diagnose, has a high recurrence rate, and is resistant to systemic therapies; as a result, CC patients have a relatively poor prognosis. One potential link to CC is the Wnt signaling pathway and its downstream effectors, which regulate cell differentiation, proliferation, migration, and fate. The aberrant activation of Wnt signaling is associated with various cancers, including CC. Recent studies have shown that activating or inhibiting the intracellular signal transduction in this pathway can regulate cancer cell growth and viability. This review will summarize the experimental evidence supporting the significance of the Wnt signaling pathway in CC, and will also discuss the current clinical role of Wnt signaling in CC diagnosis, therapy, and prognosis.

DNA methylation regulated microRNAs in HPV-16-induced head and neck squamous cell carcinoma (HNSCC)

INTRODUCTION

Epigenetic modifications have been reported to play an important role in regulating gene expression and these modifications become critical when they have a role in controlling another important layer of epigenetic regulation namely microRNAs. In the present study, we have identified the microRNAs that may be regulated by promoter DNA methylation and histone acetylation in Human papilloma virus-positive head and neck squamous cell carcinoma.

METHODOLOGY

HPV-negative cell line (UPCI:SCC-116) and HPV-16 +ve cell line (UPCI:SCC-090) were treated with methylation inhibitor (5-aza-2'-deoxycytidine, AZA) and acetylation inhibitor (Trichostatin-A, TSA), followed by micro-array analysis. The differentially expressed miRNAs were validated in control (n = 10), HPV-16 +ve (n = 30), and HPV -ve (n = 30) HNC, TCGA (n = 529) tissue samples, and two HPV -ve (SCC116 and Hacat) and two HPV +ve (SCC090 and SiHa) cell lines. Methylation-specific PCR (MSP) and chromatin immunoprecipitation assay (CHIP) were performed to validate their regulation. In silico and in vitro analyses of identified miRNAs were done to study putative pathways they target and their possible role in carcinogenesis.

RESULTS

Among 10 miRNAs specifically up-regulated in microarray analysis of AZA-treated SCC090 cells, we observed significantly decreased expression of hsa-miR-181c-5p, hsa-miR-132-5p, hsa-miR-658 in HPV +ve HNC cohort, TCGA tissue samples, and cell lines as compared to their HPV -ve counterpart, and their promoter region also possesses CpG islands. MSP and analysis of TCGA data (MethHC) revealed increased frequency of methylation at the promoter of hsa-miR-132-5p that is negatively correlated with its expression. In TSA-treated SCC090 cells, out of 7 miRNAs, two namely Hsa-miR-129-2-3p and Hsa-miR-449a were found to be up-regulated as compared to HPV -ve cells. However, the levels of enrichment by anti-acetyl-H3 and anti-acetyl-H4 were significantly low in cell lines compared to respective controls and both were up-regulated in HPV +ve compared to HPV -ve TCGA tissue samples. In silico analysis revealed hsa-miR-132-5p targeted canonical β-catenin/wnt pathway and modulation of down-stream genes of the pathway was observed on over-expression/inhibition of hsa-miR-132-5p.

CONCLUSION

This study suggests the role of epigenetic modifications in regulating expression of miRNAs in HPV +ve HNSCC.

Transgenic Mouse Models of Tumor Virus Action

Genetically engineered mice (GEMs) have provided valuable insights into the carcinogenic properties of various human tumor viruses, which, in aggregate, are etiologically associated with over 15% of all human cancers. This review provides an overview of seminal discoveries made through the use of GEM models for human DNA tumor viruses. Emphasis is placed on the discoveries made in the study of human papillomaviruses, Merkel cell carcinoma-associated polyomavirus, Epstein-Barr virus, and Kaposi's sarcoma-associated herpesvirus, because GEMs have contributed extensively to our understanding of how these DNA tumor viruses directly contribute to human cancers.

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.

Emergence of CTNNB1 mutation at acquired resistance to KIT inhibitor in metastatic melanoma

PURPOSE

The KIT inhibitor, imatinib, has shown promising efficacy in patients with KIT-mutated melanoma; however, acquisition of resistance to imatinib occurs rapidly in the majority of patients. The mechanisms of acquired resistance to imatinib in melanoma remain unclear.

METHODS

We analyzed biopsy samples from paired baseline and post-treatment tumor lesions in one patient with KIT-mutated melanoma who had had an initial objective tumor regression in response to imatinib treatment followed by disease progression 8 months later.

RESULTS

Targeted deep sequencing from post-treatment biopsy samples detected an additional mutation in CTNNB1 (S33C) with original KIT L576P mutation. We examined the functional role of the additional CTNNB1 S33C mutation in resistance to imatinib indirectly using the Ba/F3 cell model. Ba/F3 cell lines transfected with both the L576P KIT mutation and the CTNNB1 S33C mutation demonstrated no growth inhibition despite imatinib treatment, whereas growth inhibition was observed in the Ba/F3 cell line transfected with the L576 KIT mutation alone.

CONCLUSIONS

We report the first identification of the emergence of a CTNNB1 mutation that can confer acquired resistance to imatinib. Further investigation into the causes of acquired resistance to imatinib will be essential to improve the prognosis for patients with KIT-mutated melanoma.

Transcription factor AP-2β suppresses cervical cancer cell proliferation by promoting the degradation of its interaction partner β-catenin

Transcription factor AP-2β mediates the transcription of a number of genes implicated in mammalian development, cell proliferation, and carcinogenesis. Although the expression pattern of AP-2β has been analyzed in cervical cancer cell lines, the functions and molecular mechanism of AP-2β are unknown. Here, we found that AP-2β significantly inhibits TCF/LEF reporter activity. Moreover, AP-2β and β-catenin interact both in vitro through GST pull-down assays and in vivo by co-immunoprecipitation. We further identified the interaction regions to the DNA-binding domain of AP-2β and the 1-9 Armadillo repeats of β-catenin. Moreover, AP-2β binds with β-TrCP and promotes the degradation of endogenous β-catenin via the proteasomal degradation pathway. Immunohistochemistry analysis revealed a negative correlation between the two proteins in cervical cancer tissues and cell lines. Finally, functional analysis showed that AP-2β suppresses cervical cancer cell growth in vitro and in vivo by inhibiting the expression of Wnt downstream genes. Taken together, these findings demonstrated that AP-2β functions as a novel inhibitor of the Wnt/β-catenin signaling pathway in cervical cancer.

Identification of differentially expressed proteins in retinoblastoma tumors using mass spectrometry-based comparative proteomic approach

In India, retinoblastoma is among the top five childhood cancers. Children mostly present with extraocular extension and high risk features that results in unsatisfactory treatment and low survival rate. In addition, lack of potential therapeutic and prognostic targets is another challenge in the management of retinoblastoma. We studied comparative proteome of retinoblastoma patients (HPV positive and negative (n=4 each) and controls (n=4), in order to identify potential retinoblastoma-specific protein targets. 2D-DIGE coupled MALDI-TOF/TOF mass spectrometry identified 39 unique proteins. Highly deregulated proteins were GFAP,RBP3,APOA1,CRYAA,CRABP1,SAG and TF. Gene ontology (Panther 7.0) revealed majority of proteins to be associated with metabolic processes (26%) and catalytic activity (38%). 8 proteins were significantly upregulated in HPV positive vis-a-vis HPV negative cases. Patient group exhibited 12 upregulated and 18 downregulated proteins compared to controls. Pathway and network analysis (IPA software) revealed CTNNB1 as most significantly regulated signalling pathway in HPV positive than HPV negative retinoblastoma. The trends in transcriptional change of 9 genes were consistent with those at proteomic level. The Western blot analysis confirmed the expression pattern of RBP3,GFAP and CRABP1. We suggest GFAP,RBP3,CRABP1,CRYAAA,APOA1 and SAG as prospective targets that could further be explored as potential candidates in therapy and may further assist in studying the disease mechanism.

SIGNIFICANCE

In this study we evaluated tumor tissue specimens from retinoblastoma patients and identified 39 differentially regulated proteins compared to healthy retina. From these, we propose RBP3, CRABP1, GFAP, CRYAA, APOA1 and SAG as promising proteomic signatures that could further be explored as efficient prognostic and therapeutic targets in retinoblastoma. The present study is not only a contribution to the ongoing endeavour for the discovery of proteomic signatures in retinoblastoma, but, may also act as a starting point for future studies aimed at uncovering novel targets for further therapeutic interventions and improving patient outcomes.

Effects of mutations in Wnt/β-catenin, hedgehog, Notch and PI3K pathways on GSK-3 activity-Diverse effects on cell growth, metabolism and cancer

Glycogen synthase kinase-3 (GSK-3) is a serine/threonine kinase that participates in an array of critical cellular processes. GSK-3 was first characterized as an enzyme that phosphorylated and inactivated glycogen synthase. However, subsequent studies have revealed that this moon-lighting protein is involved in numerous signaling pathways that regulate not only metabolism but also have roles in: apoptosis, cell cycle progression, cell renewal, differentiation, embryogenesis, migration, regulation of gene transcription, stem cell biology and survival. In this review, we will discuss the roles that GSK-3 plays in various diseases as well as how this pivotal kinase interacts with multiple signaling pathways such as: PI3K/PTEN/Akt/mTOR, Ras/Raf/MEK/ERK, Wnt/beta-catenin, hedgehog, Notch and TP53. Mutations that occur in these and other pathways can alter the effects that natural GSK-3 activity has on regulating these signaling circuits that can lead to cancer as well as other diseases. The novel roles that microRNAs play in regulation of the effects of GSK-3 will also be evaluated. Targeting GSK-3 and these other pathways may improve therapy and overcome therapeutic resistance.

A novel prediction model for human papillomavirus-associated oropharyngeal squamous cell carcinoma using p16 and subcellular β-catenin expression

BACKGROUND

p16 overexpression is a highly sensitive yet moderately specific biomarker for predicting human papillomavirus (HPV)-associated oropharyngeal squamous cell carcinoma (OPSCC). Nuclear β-catenin translocation has been linked to HPV-positive OPSCC. However, whether the strategy of combining β-catenin with p16 can better predict HPV-associated OPSCC remains unknown.

METHODS

We evaluated the expression of p16 and β-catenin (nuclear and membrane) by immunohistochemistry staining in 101 OPSCC tissues and HPV status by HPV DNA in situ hybridization. Logistic regression models were used to evaluate single or multiple biomarkers for HPV prediction. The prediction power, sensitivity, and specificity were determined by receiver operating characteristic (ROC) analyses.

RESULTS

Our data showed that upon univariate analysis, p16 and nuclear β-catenin were positively correlated with HPV status, while membrane β-catenin was inversely correlated with HPV status (P < 0.01). p16 showed the highest HPV predictive power, with area under the curve (AUC) of 0.9074 compared to 0.6762 for nuclear β-catenin and 0.7635 for membrane β-catenin, respectively, indicating differential accuracies for HPV prediction. Multivariable analysis showed that p16 was significantly correlated with HPV, while nuclear and membrane β-catenin showed marginal significance. The three-biomarker model was similarly sensitive (98.9% vs. 100%) but more specific (88.9% vs. 81%) than p16 alone, which also showed a good predictive value for overall (P = 0.0002) survival and disease-free (P = 0.0158) survival.

CONCLUSION

Our study suggests a novel model of combining p16 and subcellular β-catenin for prediction of HPV-associatred OPSCC, and this finding deserves further validation.

Cervical cancer stem cells

The concept of cancer stem cells (CSC) has been established over the past decade or so, and their role in carcinogenic processes has been confirmed. In this review, we focus on cervical CSCs, including (1) their purported origin, (2) markers used for cervical CSC identification, (3) alterations to signalling pathways in cervical cancer and (4) the cancer stem cell niche. Although cervical CSCs have not yet been definitively identified and characterized, future studies pursuing them as therapeutic targets may provide novel insights for treatment of cervical cancer.

The relevance of molecular biomarkers in cervical cancer patients treated with radiotherapy

BACKGROUND

Radiotherapy (RT) plays an integral role in the combined-modality management of cervical cancer. Various molecular mechanisms have been implicated in the adaptive cellular response to RT. Identification of these molecular processes may permit the prediction of treatment outcome and enhanced radiation-induced cancer cell killing through tailoring of the management approach, and/or the employment of selective inhibitors of these pathways.

METHODS

PubMed was searched for studies presenting biomarkers of cervical cancer radioresistance validated in patient studies or in laboratory experimentation.

RESULTS

Several biomarkers of cervical cancer radioresistance are validated by patient survival or recurrence data. These biomarkers fall into categories of biological function including hypoxia, cell proliferation, cell-cell adhesion, and evasion of apoptosis. Additional radioresistance biomarkers have been identified in exploratory experiments.

CONCLUSIONS

Biomarkers of radioresistance in cervical cancer may allow molecular profiling of individual tumors, leading to tailored therapies and better prognostication and prediction of outcomes.

GSK3β mediates the carcinogenic effect of HPV16 in cervical cancer

Cervical cancer is one of the most prevalent and fatal cancers among women and infection of the human papillomavirus (HPV) is the most important risk factor. This study investigated how HPV16 regulated GSK3β expression and function to promote cervical cancers. The expression of GSK3β was analyzed by quantitative PCR and western blot. The proliferation, invasion, and clonogenic survival of cells with different E6/E7 levels were measured by MTT, transwell invasion assays, and soft agar colony-forming assays, respectively. The levels of GSK3β were correlated with the copy numbers and expression levels of HPV16 E6/E7 genes. HPV16 E6/E7 genes regulated GSK3β transcription through an element located in the promoter 85 and 250 base pairs upstream of the transcription start site. The abilities of cell proliferation, invasion, and clonogenic survival were increased in C33A cells by ectopic HPV16 E6/E7 and decreased in CaSki cells by knocking down HPV16 E6/E7 levels. Meanwhile, LiCl increased GSK3β transcript levels and the proliferation of CaSki cells in a HPV16-dependent manner. These data indicated that GSK3β may participated in HPV16 mediated deregulation of wnt/β-catenin and other signaling pathways promoting the progression and invasion of cervical cancers.

Wnt signalling in gynaecological cancers: A future target for personalised medicine?

The three major gynaecological cancers, ovarian, uterine and cervical, contribute a significant burden to global cancer mortality, and affect women in both developed and developing countries. However, unlike other cancer types that have seen rapid advances and incorporation of targeted treatments in recent years, personalised medicine is not yet a reality in the treatment of gynaecological cancers. Advances in sequencing technology and international collaborations and initiatives such as The Cancer Genome Atlas are now revealing the molecular basis of these cancers, and highlighting key signalling pathways involved. One pathway which plays a role in all three cancer types, is the Wnt signalling pathway. This complex developmental pathway is altered in most human malignancies, and members of this pathway, particularly the recently linked ROR receptor tyrosine kinases may be attractive future therapeutic targets. This review provides an up-to-date summary of research into Wnt signalling and ovarian, uterine and cervical cancers, and discusses the potential of the Wnt pathway as a future target for personalised medicine in gynaecological cancers.

Regulation of the Wnt/β-Catenin Signaling Pathway by Human Papillomavirus E6 and E7 Oncoproteins

Cell signaling pathways are the mechanisms by which cells transduce external stimuli, which control the transcription of genes, to regulate diverse biological effects. In cancer, distinct signaling pathways, such as the Wnt/β-catenin pathway, have been implicated in the deregulation of critical molecular processes that affect cell proliferation and differentiation. For example, changes in β-catenin localization have been identified in Human Papillomavirus (HPV)-related cancers as the lesion progresses. Specifically, β-catenin relocates from the membrane/cytoplasm to the nucleus, suggesting that this transcription regulator participates in cervical carcinogenesis. The E6 and E7 oncoproteins are responsible for the transforming activity of HPV, and some studies have implicated these viral oncoproteins in the regulation of the Wnt/β-catenin pathway. Nevertheless, new interactions of HPV oncoproteins with cellular proteins are emerging, and the study of the biological effects of such interactions will help to understand HPV-related carcinogenesis. This review addresses the accumulated evidence of the involvement of the HPV E6 and E7 oncoproteins in the activation of the Wnt/β-catenin pathway.

Klotho expression in cervical cancer: differential expression in adenocarcinoma and squamous cell carcinoma

AIMS

Klotho is a trans-membrane protein that serves as a tumour suppressor in a wide array of malignancies. Recent data suggest it as an epigenetically silenced tumour suppressor in cervical cancer. Yet, the expression pattern of klotho in cervical cancer has not been determined. We aimed to study the expression of klotho in squamous cell carcinomas (SQCC) and adenocarcinoma (ADC) of the cervix.

METHODS

Klotho expression was analysed by immunohistochemistry in 44 SQCC samples, 38 ADC samples and the adjacent normal tissue. For each sample, percentage of positive stained cells, staining intensity and a combined staining score were recorded. Staining was validated by measuring klotho mRNA levels, using quantitative RT-PCR, in 18 of the samples.

RESULTS

Klotho expression was high in all endocervical and exocervical normal tissues adjacent to tumour. No expression of klotho was noted in 7 out of 38 (18.4%) ADC samples and in 2 out of 44 (4.5%) SQCC samples. Staining intensity, number of positively stained cells and combined intensity score were all lower in tumours compared with normal adjacent tissues in ADC and SQCC. Klotho mRNA levels highly correlated with immunohistochemical (IHC) staining (p=0.008).

CONCLUSIONS

We found reduced klotho expression in cervical carcinoma, especially in ADC, compared with normal adjacent tissue. Our results support the role of klotho as a potential tumour suppressor in cervical cancer. Further studies are required in order to establish the therapeutic role of klotho in cervical carcinoma and identify patients who may benefit from it.

Generation of K14-E7/∆N87βcat double transgenic mice as a model of cervical cancer

Nearly all cervical cancers are initiated by a subset of high-risk human papilloma viruses (HPVs). However, cervical cancers develop only in a small fraction of women who are infected with these viruses. HPV is required, but not sufficient for developing cervical cancer. Activation of complementary signaling pathways appears to be necessary for malignant transformation of cervical epithelial cells that are immortalized by HPV. Here, we describe the creation and maintenance of a double transgenic mouse model that is based on constitutively active Wnt/β-catenin signaling in cervical epithelial cells expressing the HPV oncoprotein E7. These mice develop invasive cervical squamous carcinomas within 6 months with an average penetrance of 94 %.

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.

Clinical significance of inactivated glycogen synthase kinase 3β in HPV-associated cervical cancer: Relationship with Wnt/β-catenin pathway activation

PROBLEM

To determine the role of inactivated GSK3β with respect to Wnt/β-catenin pathway activation in HPV-16/18-associated cervical cancer.

METHOD OF STUDY

The expression of active (pGSK3β-Try(216)), inactive (pGSK3β-Ser(9)), and c-Myc as well as HPV-16/18 infection was analyzed in cervical intra-epithelial neoplasia (CIN), squamous cell carcinoma (SCCs) and normal by immunohistochemistry and multiplex PCR. The proteins level was also compared with β-catenin and APC expression.

RESULTS

The dramatic decrease of pGSK3β-Try(216) expression but ectopic overexpression of pGSK3β-Ser(9) and c-Myc was observed both in CIN and SCCs samples compared to normal tissues. 57/67 CIN and 132/153 SCCs showed HPV-16 infection, while 3/67 CIN and 4/153 SCCs were harbored with HPV-18 infection. Both the proteins were significantly upregulated in HPV-16 infected cases (P = 0.0001; P = 0.001) and also positively correlated with nuclear β-catenin (P = 0.0001; P = 0.0001).

CONCLUSION

The process of generation of HPV-16-associated cervical tumorigenesis is synergized with GSK3β inactivation and overactivation of Wnt/β-catenin pathway.

Tanshinone IIA inhibits viral oncogene expression leading to apoptosis and inhibition of cervical cancer

Human papilloma virus (HPV) is the well-established etiological factor of cervical cancer. E6 and E7 oncoproteins expressed by HPV are known to inactivate tumor suppressor proteins p53 and pRb, respectively. Tanshinone IIA (Tan IIA) is a diterpenoid naphthoquinone found in the traditional Chinese medicine Danshen (Salvia sp.). Tan IIA has been shown to possess anti-tumor activity against several cancer types. In this study we show that Tan IIA potently inhibited proliferation of the human cervical cancer CaSki, SiHa, HeLa and C33a cells. Mechanistically in HPV positive CaSki cells, Tan IIA was found to (i) downregulate expression of HPV E6 and E7 genes and modulate associated proteins E6AP and E2F1, (ii) cause S phase cell cycle arrest, (iii) induce accumulation of p53 and alter expression of p53-dependent targets, (iv) modulate pRb and related proteins, and (v) cause p53-mediated apoptosis by moderating Bcl2, Bax, caspase-3, and PARP cleavage expressions. In vivo, Tan IIA resulted in over 66% reduction in tumor volume of cervical cancer xenograft in athymic nude mice. Tan IIA treated tumor tissues had lower expression of proliferation marker PCNA and changes in apoptosis targets were in agreement with in vitro studies, further confirming reduced proliferation and involvement of multiple targets behind anti-cancer effects. This is the first demonstration of Tan IIA to possess significant anti-viral activity by repressing HPV oncogenes leading to inhibition of cervical cancer. Together, our data suggest that Tan IIA can be exploited as a potent therapeutic agent for the prevention and treatment of cervical and other HPV-related cancers.

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.

Requirement of estrogen receptor alpha DNA-binding domain for HPV oncogene-induced cervical carcinogenesis in mice

Cervical cancer is caused by human papillomavirus (HPV) in collaboration with other non-viral factors. The uterine cervix is hormone responsive and female hormones have been implicated in the pathogenesis of the disease. HPV transgenic mice expressing HPV16 oncogenes E6 (K14E6) and/or E7 (K14E7) have been employed to study a mechanism of estrogen and estrogen receptor α (ERα) in cervical carcinogenesis. A chronic exposure to physiological levels of exogenous estrogen leads to cervical cancer in the HPV transgenic mice, which depends on ERα. The receptor is composed of multiple functional domains including a DNA-binding domain (DBD), which mediates its binding to estrogen-responsive elements (EREs) on target genes. A transcriptional control of genes by ERα is mediated by either DBD-dependent (classical) or DBD-independent (non-classical) pathway. Although molecular mechanisms of ERα in cancer have been characterized extensively, studies investigating importance of each pathway for carcinogenesis are scarce. In this study, we employ knock-in mice expressing an ERα DBD mutant (E207A/G208A) that is defective specifically for ERE binding. We demonstrate that the ERα DBD mutant fails to support estrogen-induced epithelial cell proliferation and carcinogenesis in the cervix of K14E7 transgenic mice. We also demonstrate that cervical diseases are absent in K14E7 mice when one ERα DBD mutant allele and one wild-type allele are present. We conclude that the ERα classical pathway is required for cervical carcinogenesis in a mouse model.

A viral-human interactome based on structural motif-domain interactions captures the human infectome

Protein interactions between a pathogen and its host are fundamental in the establishment of the pathogen and underline the infection mechanism. In the present work, we developed a single predictive model for building a host-viral interactome based on the identification of structural descriptors from motif-domain interactions of protein complexes deposited in the Protein Data Bank (PDB). The structural descriptors were used for searching, in a database of protein sequences of human and five clinically important viruses; therefore, viral and human proteins sharing a descriptor were predicted as interacting proteins. The analysis of the host-viral interactome allowed to identify a set of new interactions that further explain molecular mechanism associated with viral infections and showed that it was able to capture human proteins already associated to viral infections (human infectome) and non-infectious diseases (human diseasome). The analysis of human proteins targeted by viral proteins in the context of a human interactome showed that their neighbors are enriched in proteins reported with differential expression under infection and disease conditions. It is expected that the findings of this work will contribute to the development of systems biology for infectious diseases, and help guide the rational identification and prioritization of novel drug targets.

Nip the HPV encoded evil in the cancer bud: HPV reshapes TRAILs and signaling landscapes

HPV encoded proteins can elicit ectopic protein–protein interactions that re-wire signaling pathways, in a mode that promotes malignancy. Moreover, accumulating data related to HPV is now providing compelling substantiation of a central role played by HPV in escaping immunosurveillance and impairment of apoptotic response. What emerges is an intricate network of Wnt, TGF, Notch signaling cascades that forms higher-order ligand–receptor complexes routing downstream signaling in HPV infected cells. These HPV infected cells are regulated both extracellularly by ligand receptor axis and intracellularly by HPV encoded proteins and impair TRAIL mediated apoptosis. We divide this review into different sections addressing how linear signaling pathways integrate to facilitate carcinogenesis and compounds that directly or indirectly reverse these aberrant interactions offer new possibilities for therapy in cancer. Although HPV encoded proteins mediated misrepresentation of pathways is difficult to target, improved drug-discovery platforms and new technologies have facilitated the discovery of agents that can target dysregulated pathways in HPV infected cervical cancer cells, thus setting the stage for preclinical models and clinical trials.

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.

The papillomavirus E7 proteins

E7 is an accessory protein that is not encoded by all papillomaviruses. The E7 amino terminus contains two regions of similarity to conserved regions 1 and 2 of the adenovirus E1A protein, which are also conserved in the simian vacuolating virus 40 large tumor antigen. The E7 carboxyl terminus consists of a zinc-binding motif, which is related to similar motifs in E6 proteins. E7 proteins play a central role in the human papillomavirus life cycle, reprogramming the cellular environment to be conducive to viral replication. E7 proteins encoded by the cancer-associated alpha human papillomaviruses have potent transforming activities, which together with E6, are necessary but not sufficient to render their host squamous epithelial cell tumorigenic. This article strives to provide a comprehensive summary of the published research studies on human papillomavirus E7 proteins.

AMPK activators suppress cervical cancer cell growth through inhibition of DVL3 mediated Wnt/β-catenin signaling activity

Recent evidence has suggested that AMPK activators may be applied as therapeutic drugs in suppressing cancer cell growth. However, the molecular mechanism of their suppressive function in cancer cells is still unclear. Here we show that AMPK activators impair cervical cancer cell growth through the reduction of DVL3, a positive regulator in Wnt/β-catenin signaling and an oncogenic player in cervical cancer tumorigenesis. By western blot and immunohistochemical analyses, we demonstrated that DVL3 was frequently upregulated and significantly associated with elevated β-catenin (P = 0.009) and CyclinD1 (P = 0.009) expressions in cervical cancer. Enforced expression of DVL3 elevated β-catenin and augmented cervical cancer cell growth, verifying that DVL3-mediated Wnt/β-catenin activation is involved in cervical cancer oncogenesis. On the other aspect, we noted that the cervical cancer cell growth was remarkably suppressed by AMPK activators and such cell growth inhibition was in concomitant with the reduction of DVL3 protein level in dose- and time-dependent manners. Besides, impaired mTOR signaling activity also reduced DVL3 expression. In contrast, co-treatment with Compound C (AMPK inhibitor) could significantly abrogate metformin induced DVL3 reduction. In addition, co-treatment with AM114 or MG132 (proteosomal inhibitors) could partially restore DVL3 expression under the treatment of metformin. Further in vivo ubiquitination assay revealed that metformin could reduce DVL3 by ubiquitin/proteasomal degradation. To our knowledge, this is the first report showing the probable molecular mechanisms of that the AMPK activators suppress cervical cancer cell growth by impairing DVL3 protein synthesis via AMPK/mTOR signaling and/or partially promoting the proteasomal degradation of DVL3.

WNT signalling pathways as therapeutic targets in cancer

Since the initial discovery of the oncogenic activity of WNT1 in mouse mammary glands, our appreciation for the complex roles for WNT signalling pathways in cancer has increased dramatically. WNTs and their downstream effectors regulate various processes that are important for cancer progression, including tumour initiation, tumour growth, cell senescence, cell death, differentiation and metastasis. Although WNT signalling pathways have been difficult to target, improved drug-discovery platforms and new technologies have facilitated the discovery of agents that can alter WNT signalling in preclinical models, thus setting the stage for clinical trials in humans.

Phytochemicals attenuating aberrant activation of β-catenin in cancer cells

Phytochemicals are a rich source of chemoprevention agents but their effects on modulating the Wnt/β-catenin signaling pathway have remained largely uninvestigated. Aberrantly activated Wnt signaling can result in the abnormal stabilization of β-catenin, a key causative step in a broad spectrum of cancers. Here we report the modulation of lithium chloride-activated canonical Wnt/β-catenin signaling by phytochemicals that have antioxidant, anti-inflammatory or chemopreventive properties. The compounds were first screened with a cervical cancer-derived stable Wnt signaling reporter HeLa cell line. Positive hits were subsequently evaluated for β-catenin degradation, suppression of β-catenin nuclear localization and down-regulation of downstream oncogenic targets of Wnt/β-catenin pathway. Our study shows a novel degradation path of β-catenin protein in HeLa cells by Avenanthramide 2p (a polyphenol) and Triptolide (a diterpene triepoxide), respectively from oats and a Chinese medicinal plant. The findings present Avenanthramide 2p as a potential chemopreventive dietary compound that merits further study using in vivo models of cancers; they also provide a new perspective on the mechanism of action of Triptolide.

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.

Nuclear expression of Rac1 in cervical premalignant lesions and cervical cancer cells

Background

Abnormal expression of Rho-GTPases has been reported in several human cancers. However, the expression of these proteins in cervical cancer has been poorly investigated. In this study we analyzed the expression of the GTPases Rac1, RhoA, Cdc42, and the Rho-GEFs, Tiam1 and beta-Pix, in cervical pre-malignant lesions and cervical cancer cell lines.

Methods

Protein expression was analyzed by immunochemistry on 102 cervical paraffin-embedded biopsies: 20 without Squamous Intraepithelial Lesions (SIL), 51 Low- grade SIL, and 31 High-grade SIL; and in cervical cancer cell lines C33A and SiHa, and non-tumorigenic HaCat cells. Nuclear localization of Rac1 in HaCat, C33A and SiHa cells was assessed by cellular fractionation and Western blotting, in the presence or not of a chemical Rac1 inhibitor (NSC23766).

Results

Immunoreacivity for Rac1, RhoA, Tiam1 and beta-Pix was stronger in L-SIL and H-SIL, compared to samples without SIL, and it was significantly associated with the histological diagnosis. Nuclear expression of Rac1 was observed in 52.9% L-SIL and 48.4% H-SIL, but not in samples without SIL. Rac1 was found in the nucleus of C33A and SiHa cells but not in HaCat cells. Chemical inhibition of Rac1 resulted in reduced cell proliferation in HaCat, C33A and SiHa cells.

Conclusion

Rac1 is expressed in the nucleus of epithelial cells in SILs and cervical cancer cell lines, and chemical inhibition of Rac1 reduces cellular proliferation. Further studies are needed to better understand the role of Rho-GTPases in cervical cancer progression.