Expression of human papillomavirus type 16 E6 and E7 oncoproteins in primary foreskin keratinocytes is sufficient to alter the expression of angiogenic factors

Roles of PI3K/Akt and c-Jun signaling pathways in human papillomavirus type 16 oncoprotein-induced HIF-1α, VEGF, and IL-8 expression and in vitro angiogenesis in non-small cell lung cancer cells

Background and Objectives

Human papillomavirus (HPV)-16 infection may be related to non-smoking associated lung cancer. Our previous studies have found that HPV-16 oncoproteins promoted angiogenesis via enhancing hypoxia-inducible factor-1α (HIF-1α), vascular endothelial growth factor (VEGF), and interleukin-8 (IL-8) expression in non-small cell lung cancer (NSCLC) cells. In this study, we further investigated the roles of PI3K/Akt and c-Jun signaling pathways in it.

Methods

Human NSCLC cell lines, A549 and NCI-H460, were stably transfected with pEGFP-16 E6 or E7 plasmids. Western blotting was performed to analyze the expression of HIF-1α, p-Akt, p-P70S6K, p-P85S6K, p-mTOR, p-JNK, and p-c-Jun proteins. VEGF and IL-8 protein secretion and mRNA levels were determined by ELISA and Real-time PCR, respectively. The invitro angiogenesis was observed by human umbilical vein endothelial cells (HUVECs) tube formation assay. Co-immunoprecipitation was performed to analyze the interaction between c-Jun and HIF-1α.

Results

HPV-16 E6 and E7 oncoproteins promoted the activation of Akt, P70S6K, P85S6K, mTOR, JNK, and c-Jun. LY294002, a PI3K inhibitor, inhibited HPV-16 oncoprotein-induced activation of Akt, P70S6K, and P85S6K, expression of HIF-1α, VEGF, and IL-8, and invitro angiogenesis. c-Jun knockdown by specific siRNA abolished HPV-16 oncoprotein-induced HIF-1α, VEGF, and IL-8 expression and invitro angiogenesis. Additionally, HPV-16 oncoproteins promoted HIF-1α protein stability via blocking proteasome degradation pathway, but c-Jun knockdown abrogated this effect. Furthermore, HPV-16 oncoproteins increased the quantity of c-Jun binding to HIF-1α.

Conclusions

PI3K/Akt signaling pathway and c-Jun are involved in HPV-16 oncoprotein-induced HIF-1α, VEGF, and IL-8 expression and invitro angiogenesis. Moreover, HPV-16 oncoproteins promoted HIF-1α protein stability possibly through enhancing the interaction between c-Jun and HIF-1α, thus making a contribution to angiogenesis in NSCLC cells.

Antitumor and antiangiogenic activities of curcumin in cervical cancer xenografts in nude mice

To evaluate the effects of curcumin (CUR) on tumor progression and angiogenesis in cervical cancer- (CaSki-) implanted nude mice and on the angiogenic biomarkers: vascular endothelial growth factor (VEGF), cyclooxygenase-2 (COX-2), and epidermal growth factor receptor (EGFR). CaSki cells were subcutaneously injected in nude mice to establish subcutaneous tumors. One month after injection, mice were orally administered vehicle or 500, 1,000, and 1,500 mg/kg of CUR daily × 30 consecutive days. Tumor volume was measured every 3-4 days. At the end of the study, tumor microvasculature was observed under confocal microscope, and immunohistochemical analyses were performed to detect CD31, VEGF, COX-2, and EGFR. CUR at the doses of 1,000 and 1,500 mg/kg showed significant tumor growth retardation (21.03% and 35.57%) versus CaSki + vehicle group. The microvascular density (MVD) in CaSki + vehicle group was significantly increased versus Control + vehicle group and significantly reduced by CUR (1,000 and 1,500 mg/kg). VEGF, COX-2, and EGFR expressions were upregulated in CaSki + vehicle group and attenuated significantly by CUR (1,000 and 1,500 mg/kg). In conclusion, high dose CUR inhibited tumor growth and angiogenesis in CaSki-implanted mice probably mediated by the downregulation of VEGF, COX-2 and EGFR. CUR may have a role in treating human cervical cancer and should be explored further.

The PPARβ agonist L-165041 promotes VEGF mRNA stabilization in HPV18-harboring HeLa cells through a receptor-independent mechanism

Peroxisome Proliferator-Activated Receptor-β (PPARβ) is a ligand-inducible transcription factor activated by both natural (fatty acids and derivatives) and high affinity synthetic agonists. It is thought to play a role in angiogenesis development and Vascular Endothelial Growth Factor (VEGF) regulation but its contribution remains unclear. Until now, the PPARβ agonism effect on VEGF expression in cervical cancer cells was unknown. This led to our interest in assessing the effect of PPARβ activation on the regulation of different VEGF isoforms mRNA expression and the impact of E6 viral oncoprotein and its target p53 on this regulation in cervical cancer cells. Here, we showed that the PPARβ agonist L-165041 induces VEGF(121), VEGF(165) and VEGF(189) expression in HPV (Human Papillomavirus) positive HeLa cells but not in HPV negative cells. The underlying mechanisms did involve neither E6 oncoprotein nor p53. We highlighted a novel mode of PPARβ ligand action including a post-transcriptional regulation of VEGF mRNA expression through the p38 MAPK signaling pathway and the activation of the mRNA-stabilizing factor HuR. But most importantly, we clearly demonstrated that L-165041 acts independently of PPARβ since its effect was not reversed by a chemical inhibition with a specific antagonist and the siRNA-mediated knockdown of the nuclear receptor. As VEGF is crucial for cancer development, the impact of PPARβ ligands on VEGF production is of high importance. Thus, the molecular mechanism of their action has to be elucidated and as a result, PPARβ agonists currently in clinical trials should be carefully monitored.

Transcription expression and clinical significance of mRNA of vascular endothelial growth factor and endostatin in liquid-based preparation specimens from patients with cervical dysplasia and carcinoma

OBJECTIVES

The aim of this study was to assess the diagnostic usefulness of vascular endothelial growth factor (VEGF) and endostatin mRNA in cervical specimens of patients with cervical dysplasia and carcinoma.

STUDY DESIGN

Transcription levels of VEGF and endostatin were detected by RT-PCR in cervical liquid-based preparation specimens and compared with cytological assessments.

RESULTS

VEGF as well as endostatin mRNA expression was significantly associated with either cytological or histological diagnosis (p < 0.05). VEGF mRNA and endostatin mRNA were significantly more likely to be expressed in squamous cell carcinomas (SCC) than in cervical intraepithelial neoplasia (CIN) III (p < 0.01 and p < 0.05), and obviously also more likely to be expressed in CINII than in CINI and in CINIII than in CINII (p < 0.05). Eleven inflammation lesions gave positive results by cytology but negative results by RT-PCR for VEGF and endostatin mRNA. Twenty-four SCC lesions gave false-negative or precancerous lesion results by cytology but positive results by RT-PCR for VEGF and/or endostatin mRNA expression.

CONCLUSION

Transcription levels of VEGF and endostatin by RT-PCR may be an adjunct to cytology screening for early detection of cervical carcinomas and may determine the progressive potentiality of individual lesions, especially in high-risk patients.

Cervical carcinoma cells stimulate the angiogenesis through TSLP promoting growth and activation of vascular endothelial cells

PROBLEM

To explore whether cervical carcinomas cells-derived thymic stromal lymphopoietin (TSLP) modulates the biologic behavior of vascular endothelial cells and herein participates in the angiogenesis in the cervical cancer pathogenesis.

METHOD OF STUDY

We analyzed expression of TSLP and its receptor (TSLPR) in cervical cancer cells by immunohistochemistry, ELISA, and flow cytometry, respectively. We further investigated the effects of TSLP on the proliferation, apoptosis, activation, and angiogenesis in vitro of human umbilical vein endothelial cells (HUVECs).

RESULTS

It has been found that the cervical cancer cells translate TSLP and endothelial cells express TSLPR in cervical cancer tissues. Both HeLa and CaSki cells secret TSLP in a time-dependent manner, and the ratio of TSLPR-positive HUVECs is about 30%. It has been showed that recombinant human TSLP (rhTSLP) can significantly increase Ki67 and CD62E expression in HUVECs and interleukin-6 (IL-6) levels from HeLa and CaSki cells; on the contrary, anti-human TSLP or TSLPR neutralizing antibody down-regulates the expression of Ki67, angiogenesis-relative molecules CD62E, and CD105 in HUVECs cocultured with HeLa or CasKi cells and inhibits IL-6 secretion from HeLa and CaSki cells. Moreover, both rhTSLP and endogenous TSLP from HeLa or CaSki cells obviously stimulate the proliferation, activation, and angiogenesis, but not influence the apoptosis of HUVECs in vitro.

CONCLUSION

This study has demonstrated that TSLP secreted by cervical carcinomas cells is involved in the angiogenesis of cervical cancer in a paracrine manner.

HIF proteins connect the RB-E2F factors to angiogenesis

Recently, we showed that E2F7 and E2F8 (E2F7/8) are critical regulators of angiogenesis through transcriptional control of VEGFA in cooperation with HIF.¹ Here we investigate the existence of other novel putative angiogenic E2F7/8-HIF targets, and discuss the role of the RB-E2F pathway in regulating angiogenesis during embryonic and tumor development.

Human papillomavirus up-regulates MMP-2 and MMP-9 expression and activity by inducing interleukin-8 in lung adenocarcinomas

Human papillomavirus (HPV) infection is associated with non-smoking female lung cancer. Our previous report demonstrated that HPV 16 promotes lung tumor cell progression by up-regulating interleukin-17 (IL-17). IL-17 and its downstream signaling mediator, interleukin-8 (IL-8), have been implicated to modulate a variety of pro-angiogenic factors and play important roles in tumor angiogenesis and metastasis. Accordingly, we hypothesized that HPV infection may potentiate tumorigenic and metastatic characteristics of the infected cells through IL-8. The goal of the present study was to determine whether HPV infection in lung adenocarcinoma cells can promote the expression of IL-8 and metalloproteinases (MMPs) to make the transformed cells equipped with angiogenic and metastatic characteristics. The expression of IL-8 and MMPs in HPV 16 E6-transfected H1299 cells was analyzed to examine the hypothesis. HPV 16 E6 up-regulates pro-angiogenic MMP-2 and MMP-9 through inducing IL-8 expression in lung cancer cells. The results indicate that, in addition to cell proliferation-related machinery, HPV infection promotes the expression and activities of angiogenic and metastatic molecules in lung adenocarcinoma cells. The cytokines induced by HPV infection may work together to confer the malignant and tumorigenic potentials on the infected cells by promoting machineries of growth, angiogenic and metastatic characteristics.

Tissue biomarkers as prognostic variables of cervical cancer

The most important prognostic variables of cervical carcinoma are FIGO stage, lymph node status and clinical-pathological features of primary tumor. Recently, there has been increasing interest in the identification of biomarkers able to predict both response to treatment and survival. The aim of this review is to critically evaluate current published evidence on the ability of various tissue biomarkers to predict the clinical outcome of patients with cervical carcinoma. In particular, the paper takes into account DNA content, cell-cycle and apoptosis-regulatory proteins, epidermal growth factor receptor [EGFR], vascular endothelial growth factor [VEGF], cyclooxygenase [COX]-2, signal transducer and activator of transcription [Stat]3, human papilloma virus [HPV] status, tumor hypoxia, tumor infiltrating lymphocytes [TIL], microarray technology and microRNA (miRNA). The presence of HPV-18 genotype and an elevated VEGF expression appear to be poor prognostic factors in women with early disease treated with primary surgery, whereas the expression of EGFR, VEGF, COX-2 and tumor hypoxia may have a major impact on the survival of patients treated with definitive radiotherapy or chemoradiation. The data supporting the reliability of ΔNp73 and TAp73α as novel biomarkers of response to radiotherapy are interesting but still limited. DNA microarray technology could offer new laboratory tools for a rationale planning of treatment strategy, and miRNAs might represent new candidate targets to be investigated for both prognostic and therapeutic purposes. Moreover, the assessment of different types of TIL and their ligands in tumor biopsies could enable the identification of a subset of high-risk patients, paving the way to novel immune therapies aimed at blocking T-reg cell activity.

Molecularly targeted therapies in cervical cancer. A systematic review

Cervical cancer represents the third most common cause of female cancer mortality. Even with the best currently available treatment, a significant proportion of patients will experience recurrence and eventually die. Evidently, there is a clear need for the development of new agents with novel mechanisms of action in this disease. A number of biological agents modulating different signal transduction pathways are currently in clinical development, inhibiting angiogenesis, targeting epidermal growth factor receptor, cell cycle, histone deacetylases, cyclooxygenase-2 (COX-2), or mammalian target of rapamycin (mTOR). This is the first systematic review of the literature to synthesize all available data emerging from trials and evaluate the efficacy and safety of molecularly targeted drugs in cervical cancer. However, it should be stressed that relatively fewer molecularly targeted agents have been tested in cervical cancer in comparison with other cancer types; of note, no related phase 3 trials have been published and consequently no agent has been approved for use in clinical practice. Nevertheless, the promising results of bevacizumab in therapeutic trials for cervical cancer have shown that targeting the VEGF pathway is an attractive therapeutic strategy. As knowledge accumulates on the molecular mechanisms underlying carcinogenesis in the cervix, the anticipated development and assessment of molecularly targeted agents may offer a promising perspective for cervical cancer.

Human papillomavirus 18 E6 inhibits phosphorylation of p53 expressed in HeLa cells

Background

In HPV infected cells p53 function is abrogated by E6 and even ectopically expressed p53 is unable to perform tumor suppressor functions. In addition to facilitating its degradation, E6 may also inhibit p53 transactivity, though the mechanisms are still poorly understood. It has been reported that inhibition of p300, an acetyltransferase responsible for p53 acetylation is inactivated by E6. Activation of overexpressed p53 to cause cell growth inhibition is facilitated by its phosphorylation. Previously, we reported that non-genotoxically overexpressed p53 in HeLa cells needs to be phosphorylated to perform its cell growth inhibitory functions. Since over expressed p53 by itself was not activated, we hypothesized an inhibitory role for E6.

Results

Majority of reports proposes E6 mediated degradation of p53 as a possible reason for its inactivation. However, results presented here for the first time demonstrate that overexpressed p53 is not directly associated with E6 and therefore free, yet it is not functionally active in HPV positive cells. Also, the stability of overexpressed p53 does not seem to be an issue because inhibition of proteasomal degradation did not increase the half-life of overexpressed p53, which is more than endogenous p53. However, inhibition of proteasomal degradation prevents the degradation of endogenous p53. These findings suggest that overexpressed p53 and endogenous p53 are differentially subjected to proteasomal degradation and the reasons for this discrepancy remain unclear. Our studies demonstrate that p53 over expression has no effect on anchorage independent cell-growth and E6 nullifies its cell growth inhibitory effect. E6 overexpression abrogates OA induced p53 occupancy on the p21 promoter and cell death as well. E6 did not decrease p53 protein but phospho-p53 level was significantly reduced.

Conclusion

We report for the first time that E6 de-activates p53 by inhibiting its phosphorylation. This prevents p53 binding to p21 promoter and thereby restraining its cell-growth inhibitory functions. Our study provides new evidence indicating that viral protein E6 inhibits p53 transactivity by mechanism independent of degradation pathway.

Lysophosphatidic acid receptor 2/3-mediated IL-8-dependent angiogenesis in cervical cancer cells

The expression of lysophosphatidic acid (LPA)-specific receptors in cervical cancer has not been clearly defined. In this study, we identified LPA1, LPA2 and LPA3 receptors' mRNA in SiHa, HeLa and CaSki cell lines by RT-PCR. These receptors were not associated with tumor cell proliferation in vitro. We then used a xenograph animal model to evaluate the effects of these receptors on in vivo cervical cancer tumorigenicity. When SiHa cells with different receptor expression patterns were seeded on the backs of SCID mice, the resulting knockout of both LPA2 and LPA3 significantly attenuated tumor growth; this decrease in tumor growth was found to be linked with decreased angiogenesis (microvessel density), suggesting that LPA2 and LPA3 are crucial for in vivo tumor growth through an angiogenic mechanism. We further investigated this mechanism of LPA receptor 2/3-mediated angiogenic capability by analyzing angiogenic factors in protein lysates from receptor knockout tumors, by detecting interleukin (IL-8) mRNA expression after treating with siRNA, by evaluating the biological role of LPA-enhanced IL-8 via endothelial cell tube formation, monolayer permeability, migration and cell growth assays, and by IL-8 knockout xenograft mice modeling. We found that the angiogenesis is mediated through IL-8. Finally, we evaluated the regulation pathways involved in LPA-induced IL-8 expression. We found that LPA receptor 2/3-mediated IL-8 expression occurs through Gi/PI3K/AKT, Gi/PKC and IκB/NF-κB signaling. In conclusion, we propose that LPA2 and LPA3 might play an important role in cervical cancer tumor growth through IL-8-dependent angiogenesis.

Hypoxia inducible factor-1 alpha expression is increased in infected positive HPV16 DNA oral squamous cell carcinoma and positively associated with HPV16 E7 oncoprotein

Background

There is increasing evidence for the role of High Risk (HR) Human PapillomaVirus (HPV) in the pathogenesis of Oral Squamous Cell Carcinoma (OSCC). The E6 and E7 oncogenes from HR HPVs are responsible for the deregulation of p53 and pRB proteins involved in cell cycle and apoptotic pathways. In cell lines experiments, the HPV E7 protein seems to be able to enhance Hypoxia Inducible Factor-1 alpha (HIF-1α) activity, normally involved in the response to hypoxia and able to enhance angiogenesis.

Results

We studied tumor specimens from 62 OSCC; a higher prevalence of tumors in TNM stage II and also in pT2 class between OSCC infected positive HPV16 DNA than non-infected ones was observed. HIF-1α positivity was detected throughout the analysed fields, not associated with areas of necrosis and also observed in cells immediately adjacent to blood vessels. A significant increase in mean values of the HIF-1α labeling indexes was observed for pT1-T2, as well for stage I-II, in the infected positive HPV16 DNA tumors than non-infected ones. HIF-1α and HPV16 E7 labeling indexes showed a significantly positive correlation which suggested a positive association between HPV16 E7 and HIF-1α expression.

Conclusions

In our specimens HIF-1α immunoreactivity hints for an O₂-independent regulatory mechanism in infected positive HPV16 DNA tumors, especially for pT1-T2 and stage I-II tumors, suggesting a very early involvement in the development of HPV-induced OSCC. HIF-1α and HPV16 E7 labeling indexes suggest also a positive association between the two proteins in infected positive HPV16 DNA OSCC.

Viruses as key regulators of angiogenesis

Angiogenesis is an important physiological process that is controlled by a precise balance of growth and inhibitory factors in healthy tissues. However, environmental and genetic factors may disturb this delicate balance, resulting in the development of angiogenic diseases, tumour growth and metastasis. During the past decades, extensive research has led to the identification and characterization of genes, proteins and signalling pathways that are involved in neovascularization. Moreover, increasing evidence indicates that viruses may also regulate angiogenesis either directly, by (i) producing viral chemokines, growth factors and/or receptors or (ii) activating blood vessels as a consequence of endothelial cell tropism, or indirectly, by (iii) modulating the activity of cellular proteins and/or (iv) inducing a local or systemic inflammatory response, thereby creating an angiogenic microenvironment. As such, viruses may modulate several signal transduction pathways involved in angiogenesis leading to changes in endothelial cell proliferation, migration, adhesion, vascular permeability and/or protease production. Here, we will review different mechanisms that may be applied by viruses to deregulate the angiogenic balance in healthy tissues and/or increase the angiogenic potential of tumours.

Overexpression of human papillomavirus (HPV) type 16 oncoproteins promotes angiogenesis via enhancing HIF-1α and VEGF expression in non-small cell lung cancer cells

HPV-16 infection may play an important role in the development of non-small cell lung cancer (NSCLC) among never-smokers. Due to the critical role of angiogenesis in NSCLC development, we describe here the effect of HPV-16 oncoproteins on angiogenesis in NSCLC and the underlying mechanisms. We found that overexpression of HPV-16 E6 and E7 oncoproteins in NSCLC cells significantly promoted angiogenesis both in vitro and in vivo, and correspondingly, an enhanced expression of HIF-1α and VEGF, important pro-angiogenic factors in tumor angiogenesis. Meanwhile, overexpression of HPV-16 oncoproteins also led to HIF-1α-dependent increases in the secretion of several other pro-angiogenic factors, including IL-8. Our findings suggest that HPV-16 oncoproteins contribute to the development of NSCLC possibly by promoting HIF-1α/VEGF-mediated tumor angiogenesis.

Pathway profiling and rational trial design for studies in advanced stage cervical carcinoma: a review and a perspective

Multiple genetic abnormalities will have occurred in advanced cervical cancer and multiple targeting is likely to be needed to control tumor growth. To date, dominant therapeutic targets under scrutiny for cervical cancer treatment have been EGFR pathway and angiogenesis inhibition as well as anti-HPV vaccines. The potentially most effective targets to be blocked may be downstream from the membrane receptor or at the level of the nucleus. Alterations of the pathways involved in DNA repair and in checkpoint activations, as well as the specific site of HPV genome integration, appear worth assessing. For genetic mutational analysis, complete exon sequencing may become the norm in the future but at this stage frequent mutations (that matter) can be verified by PCR analysis. A precise documentation of relevant alterations of a large spectrum of protein biomarkers can be carried out by reverse phase protein array (RPPA) or by multiplex analysis. Clinical decision-making on the drug(s) of choice as a function of the biological alteration will need input from bio-informatics platforms as well as novel statistical designs. Endpoints are yet to be defined such as the loss (or reappearance) of a predictive biomarker. Single or dual targeting needs to be explored first in relevant preclinical animal and in xenograft models prior to clinical deployment.

Transforming activity of a novel mutant of HPV16 E6E7 fusion gene

An optimized recombinant HPV16 E6E7 fusion gene (HPV16 ofE6E7) was constructed according to codon usage for mammalian cell expression, and a mutant of HPV16 ofE6E7 fusion gene (HPV16 omfE6E7) was generated by site-directed mutagenesis at L57G, C113R for the E6 protein and C24G, E26G for the E7 protein for HPV16 ofE6E7 [patent pending (CN 101100672)]. The HPV16 omfE6E7 gene constructed in this work not only lost the transformation capability to NIH 3T3 cells and tumorigenicity in SCID mice, but also maintained very good stability and antigenicity. These results suggests that the HPV16 omfE6E7 gene should undergo further study for application as a safe antigen-specific therapeutic vaccine for HPV16-associated tumors.

Vascular Endothelial Growth Factor Gene Polymorphisms and Risk of Cervical Intraepithelial Neoplasia

Objective:

To evaluate the association between 3 vascular endothelial growth factor (VEGF) gene polymorphisms and susceptibility of cervical intraepithelial neoplasia (CIN).

Materials and Methods:

This prospectively collected case-control study investigates three common VEGF gene polymorphisms (ie, VEGF −460 [rs833061], VEGF +405 [rs2010963], and VEGF +936 [rs3025039]) in 203 women with CIN and 209 healthy women by DNA pyrosequencing. Associations between polymorphisms and CIN risk are evaluated with univariate and multivariable models and haplotype analysis.

Results:

In a multivariable regression model, the variant VEGF +405C allele was associated (odds ratio [OR], 2.5; 95% confidence interval [CI], 1.2-5.1], P = 0.02) with increased susceptibility of CIN independent of number of sexual partners (OR, 2.2; 95% CI, 1.1-4.6; P = 0.03) and smoking (OR, 3.3; 95% CI, 1.6-6.6; P = 0.001). The haplotype VEGF −460C - +405C - +936C was associated with an OR of 5.2 (95% CI, 1.2-52.7) for the susceptibility of CIN.

Conclusions:

The presence of the variant VEGF +405C allele and the haplotype VEGF −460C - +405C - +936C are independently associated with higher susceptibility of CIN.

Down-regulation of HPV18 E6, E7, or VEGF expression attenuates malignant biological behavior of human cervical cancer cells

To investigate the effect of down-regulation of VEGF (vascular endothelial growth factor) and HPV18 E6/E7 by hairpin RNA (shRNA) on cell proliferation, apoptosis, migration, invasion, and adhesion abilities of cervical carcinoma cells, recombinant plasmids including pS-E6 shRNA, pS-E7 shRNA, and pS-VEGF shRNA were constructed and transfected into HeLa cells. The levels of E6 mRNA, E7 mRNA, or VEGF mRNA were significantly reduced after transfection of pS-E6 shRNA (76.0%), pS-E7 shRNA (74.4%), and pS-VEGF shRNA (46.7%). VEGF expression was down-regulated by pS-E6 shRNA (55.1%) and pS-E7 shRNA (46.6%). The apoptosis of HeLa cells was increased, and the proliferation, invasion, and adhesion abilities were decreased significantly. For in vivo study, cancer cells that stably expressed the plasmids were cultured. Cells were transplanted subcutaneously into nude mice to establish xenograft tumor model. Finally, expression of E6 shRNA, E7 shRNA, and VEGF shRNA in cancer cells led to inhibition of the growth of xenograft. Hence, RNA interference could effectively suppress the expression of HPV18 E6/E7 and VEGF in human cervical cancer cells. This suppression attenuates malignant biological behavior of human cervical cancer cells. RNA interference of HPV E6/E7 or VEGF expression implies an effective anti-cervical cancer strategy.

Hypoxia-Inducible Factor 1α Polymorphisms and Early-Stage Cervical Cancer

Background:

Human papillomavirus can stabilize and induce hypoxia-inducible factor 1α (HIF-1α) protein, which is associated with diminished response to treatment and poor prognosis for cervical cancer. Hypoxia-inducible factor 1α polymorphisms (1772C>T and 1790G>A) in the N-terminal transactivation domain generate significantly increased transcriptional activity and have been linked to poor outcome in various malignancies.

Objective:

The aim of this study was to analyze the possible influence of HIF-1α genetic polymorphisms on cancer susceptibility, tumor aggressiveness, and survival of patients with early-stage cervical cancer.

Methods:

One hundred ninety-nine patients with early-stage cervical cancer who were treated with surgical resection were retrospectively investigated. Hypoxia-inducible factor 1α 1772C>T and 1790G>A genetic polymorphisms were compared with 205 healthy subjects and correlated with the clinical outcome of patients with early-stage cervical cancer.

Results:

The risk of cervical cancer was not affected by HIF-1α 1772C>T and 1790G>A polymorphisms. However, lymph node metastasis was significantly increased in patients who had the 1790 variant (adjusted odds ratio, 5.01; 95% confidence interval, 1.05-23.88;P= 0.043). In survival analysis, HIF-1α 1772C>T and 1790G>A polymorphisms were not related to disease-free survival and overall survival.

Conclusions:

Although HIF-1α genetic polymorphisms had little association with cervical cancer risk and prognosis, individual variance of HIF-1α gene may be associated with cervical cancer invasiveness.

Expression of human papillomavirus type 16 E7 is sufficient to significantly increase expression of angiogenic factors but is not sufficient to induce endothelial cell migration

Tumor suppressors negatively regulate angiogenesis, an essential step in tumor progression. Together, HPV 16 E6 and E7 proteins, which target p53 and pRb family members, respectively, for degradation, increase the expression of two angiogenic inducers, VEGF and IL-8, in primary foreskin keratinocytes (HFKs). Conditioned media from such cells are sufficient to alter endothelial cell behavior. Here, the individual contribution of E6 and E7 to angiogenesis was investigated. E7 and, to a lesser extent E6, increased expression of VEGF and IL-8. Nevertheless, neither conditioned media from HPV 16 E6 nor E7-expressing HFKs were sufficient to induce migration of endothelial cells. Conditioned media from HFKs expressing the HPV 16 E6 and the E7 mutant E7C24G, which can target p107 and p130 but not pRb for degradation, contained increased levels of VEGF and IL-8. The results suggest that the mechanism of HPV 16 E7-mediated increased levels of VEGF is pRb-independent.

Human papillomavirus E7 enhances hypoxia-inducible factor 1-mediated transcription by inhibiting binding of histone deacetylases

Infection by human papillomaviruses (HPV) leads to the formation of benign lesions, warts, and in some cases, cervical cancer. The formation of these lesions is dependent upon increased expression of proangiogenic factors. Angiogenesis is linked to tissue hypoxia through the activity of the oxygen-sensitive hypoxia-inducible factor 1α (HIF-1α). Our studies indicate that the HPV E7 protein enhances HIF-1 transcriptional activity whereas E6 functions to counteract the repressive effects of p53. Both high- and low-risk HPV E7 proteins were found to bind to HIF-1α through a domain located in the N-terminus. Importantly, the ability of E7 to enhance HIF-1 activity mapped to the C-terminus and correlated with the displacement of the histone deacetylases HDAC1, HDAC4, and HDAC7 from HIF-1α by E7. Our findings describe a novel role of the E7 oncoprotein in activating the function of a key transcription factor mediating hypoxic responses by blocking the binding of HDACs.

Inhibition of cervical cancer cell growth in vitro and in vivo with dual shRNAs

RNA interference (RNAi)-based gene silencing is widely used in laboratories for gene function studies and also holds a great promise for developing treatments for diseases. However, in vivo delivery of RNAi therapy remains a key issue. Lentiviral vectors have been employed for stable gene transfer and gene therapy and therefore are expected to deliver a stable and durable RNAi therapy. But this does not seem to be true in some disease models. Here, we showed that lentivirus delivered short-hairpin RNA (shRNA) against human papillomavirus (HPV) E6/E7 oncogenes were effective for only 2 weeks in a cervical cancer model. However, using this vector to carry two copies of the same shRNA or two shRNAs targeting at two different but closely related genes (HPV E6 and vascular endothelial growth factor) was more effective at silencing the gene targets and inhibiting cell or even tumor growth than their single shRNA counterparts. The cancer cells treated with dual shRNA were also more sensitive to chemotherapeutic drugs than single shRNA-treated cells. These results suggest that a multi-shRNA strategy may be a more attractive approach for developing an RNAi therapy for this cancer.

Persistence of human papillomavirus infection: keys to malignant progression

Human papillomaviruses (HPVs) are the etiologic agents of cervical and other epithelial cancers. Persistence of infections by high-risk HPV types is the single greatest risk factor for malignant progression. Although prophylactic vaccines have been developed that target high-risk HPV types, there is a continuing need to understand better the virus-host interactions that underlie persistent benign infection and progression to cancer. In this review we summarize the molecular events that facilitate the differentiation-dependent HPV life cycle, how the life cycle is organized to facilitate virus persistence, and how the activities of HPV regulatory proteins result in malignancy.

VEGF polymorphisms in early cervical cancer susceptibility, angiogenesis, and survival

OBJECTIVE

Vascular endothelial growth factor (VEGF) plays an important role in cervical carcinogenesis. We hypothesized that VEGF genetic polymorphisms may affect cancer susceptibility, angiogenesis, and survival in patients with early cervical cancer.

METHODS

Among 215 healthy subjects and 199 early cervical cancer patients who were treated with surgical resection, we specifically investigated four genetic polymorphisms within the VEGF gene (-2578C>A, -460 T>C, +405G>C, and +936C>T). VEGF and CD31 microvessel density (MVD) were measured using tissue microarrays constructed from 117 patients who had available tissue.

RESULTS

Risk of cervical cancer was decreased in subjects with the VEGF -2578A/A genotype (adjusted OR=0.39, 95% CI 0.16-0.96). Angiogenesis measured by CD31 MVD was significantly decreased in patients with the VEGF +405C/C genotype and VEGF -2578C - -460 T - +405C haplotype (recessive model; adjusted OR=0.32, 95% CI 0.11-0.99, equally). Moreover, VEGF +405C/C and VEGF -2578C - -460 T - +405C haplotype were significantly related to shorter disease-free survival (adjusted HR=3.18, 95% CI 1.13-8.94, equally) and overall survival (adjusted HR=8.86, 95% CI 1.40-56.08, equally) by multiple Cox regression analysis.

CONCLUSION

Polymorphisms of VEGF genes may affect cancer susceptibility and survival of early cervical cancer by modulating tumor angiogenesis. Prospective study among homogeneously treated patients is warranted.

Human papillomavirus type 16 E5 oncoprotein as a new target for cervical cancer treatment

Human papillomavirus (HPV) infection is considered to be the necessary cause of cervical cancer. E6 and E7 oncoproteins of HPV have been known to play major roles in malignant transformation of cervical cells, inhibiting the tumor suppressors p53 and Rb. However, the role of E5 oncoprotein has been relatively less defined. HPV 16 E5 is a hydrophobic membrane-bound protein which associates with the Golgi apparatus, endoplasmic reticulum and perinuclear membrane. Accumulating evidences have suggested that E5 oncoprotein may also contribute to cervical carcinogenesis through modulating cellular signaling pathways in addition to augmenting the immortalization potential of E6 and E7. Multiple mechanisms, including activation of EGFR or inflammatory cell signaling pathway, have been implicated in malignant transformation by HPV 16 E5. Therefore, targeting E5 may be a rational approach for chemoprevention and treatment of cervical cancer, and understanding its oncogenic processes may help us to design novel therapeutic strategies. In this review, we discussed the roles of HPV 16 E5 in cervical carcinogenesis, altering several cellular signaling pathways involved in cell proliferation, angiogenesis and apoptosis.

Stromal issues in cervical cancer: a review of the role and function of basement membrane, stroma, immune response and angiogenesis in cervical cancer development

The carcinogenesis of cervical carcinoma implies an intricate interplay of neoplastic, human papillomavirus infected epithelial cells and stromal tissue, in which different factors have distinct but interacting influence. Persistent infection with an oncogenic human papillomavirus type may lead to epithelial dysplasia with progressive severity. To access the adjacent stromal tissue, tumour cells have to breach the basement membrane. The stroma partly controls tumour growth, invasion and angiogenesis. Last but not least there is considerable influence of the immune response. In this review we describe the importance of various stromal factors in carcinogenesis of cervical cancer.

Dendrosome-based delivery of siRNA against E6 and E7 oncogenes in cervical cancer

Although small interfering RNA (siRNA) treatment holds great promise for the treatment of cancers, the field has been held back by the availability of suitable delivery vehicles. For cervical cancer the E6 and E7 oncogenes are ideal siRNA targets for treatment. The purpose of the present study was to explore the potential of dendrosomes for the delivery of siRNA targeting E6 and E7 proteins of cervical cancer cells in vitro. Optimization of dendrimer generation and nitrogen-to-phosphate (N/P) ratio was carried out using dendrimer-fluorescein isothiocyanate oligo complexes. The optimized N/P ratios were used in formulating complexes between dendrimers and siRNA targeting green fluorescence protein (siGFP). Although formulation 4D100 (dendrimer-siRNA complex) displayed the highest GFP knockdown, it was also found to be highly toxic to cells. In the final formulation 4D100 was encapsulated into dendrosomes so as to mask these toxic effects. The optimized dendrosomal formulation (DF), DF3 was found to possess a siGFP-entrapment efficiency of 49.76% +/- 1.62%, vesicle size of 154 +/- 1.73 nm, and zeta potential of +3.21 +/- 0.07 mV. The GFP knockdown efficiency of DF3 (dendrosome) was found to be almost identical to that of 4D100, but the former was completely nontoxic to the cells. DF3 containing siRNA against E6 and E7 was found to knock down the target genes considerably, as compared with the other formulations tested. Our results imply that dendrosomes hold potential for the delivery of siRNA and that a suitable targeting strategy could be useful for applications in vivo.

FROM THE CLINICAL EDITOR

siRNA treatment holds great promise for the treatment of cancers, but overall, the availability of suitable delivery vehicles remains a major issue. The purpose of this study was to explore the potential of dendrosomes for the delivery of siRNA targeting specific proteins in cervical cancer cells in vitro. The results suggest that dendrosomes hold potential for the delivery of siRNA and a suitable targeting strategy could be useful for applications in vivo.

Profiling pancreatic cancer-secreted proteome using 15N amino acids and serum-free media

OBJECTIVES

A new method of determining protein turnover by labeling protein with N amino acids was used in conjunction with serum-free cell culture to profile secreted proteins that are released by MIA PaCa-2 pancreatic cancer cells in culture.

METHODS

MIA PaCa-2 cells were first cultured in Dulbecco modified Eagle medium (Gibco by Invitrogen, Carlsbad, Calif) with 10% fetal bovine serum, then in serum-free modified Eagle medium with or without 50% N algal amino acid mixture. The effect of oxythiamine chloride on secreteome was studied. Secreteome from cell culture media was analyzed by 2-dimensional (2D) gel electrophoresis. Differentially expressed proteins were detected and identified. Protein turnover rates were calculated according to the newly established method. Western blot and enzyme-linked immunosorbent assay were used to validate identified proteins.

RESULTS

Among the 14 differentially expressed proteins after oxythiamine treatment, tissue inhibitor of metalloproteases-1 and cytokeratin-10 were identified as 2 newly synthesized secreted proteins caused by substantial N incorporation. The inhibition of tissue inhibitor of metalloproteases-1 expression in MIA PaCa-2 cells by oxythiamine treatment was first demonstrated by 2D gel electrophoresis and further validated by Western blotting and enzyme-linked immunosorbent assay analyses.

CONCLUSIONS

Our method of labeling protein with N amino acids in conjunction with serum-free cell culture allows the identification of actively secreted proteins from pancreatic cancer cells and is a useful method for serum biomarker discovery.

Defining molecular phenotypes of human papillomavirus-associated oropharyngeal squamous cell carcinoma: validation of three-class hypothesis

OBJECTIVE

The purpose of this study was to determine if oropharyngeal squamous cell carcinoma (OSCC) classified into three groups based on human papillomavirus (HPV) 16 DNA presence and p16 expression display different protein expression patterns.

STUDY DESIGN

Cross-sectional study.

SETTING

A laboratory-based study of patients with OSCC treated at a tertiary care academic medical center.

SUBJECTS AND METHODS

Paraffin-embedded OSCC specimens from 77 patients classified into the three-class model (HPV negative, HPV inactive [HPV16+/p16-], and HPV active [HPV16+/p16+]) were queried for the expression of 14 tumor progression proteins using AQUA (HistoRx, New Haven CT). Protein expression between groups was assessed by analysis of variance. Global expression patterns were determined by unsupervised hierarchical clustering.

RESULTS

There were significant differences in expression of beta-catenin (P = 0.009), epidermal growth factor receptor (P = 0.009), and vascular endothelial growth factor (P = 0.028) between groups. HPV-active tumors had overexpression of beta-catenin. Hierarchical clustering showed HPV-negative and HPV-inactive tumors displayed association patterns distinct from HPV-active tumors.

CONCLUSIONS

Tumors classified by HPV DNA presence and p16 expression have different molecular phenotypes. This is the first demonstration of overexpression of beta-catenin (also found in HPV-caused cervical cancer) in HPV-active OSCC. HPV-active OSCC may share a similar ontogeny to HPV-caused cervical cancer.

A phase II study of sunitinib in patients with locally advanced or metastatic cervical carcinoma: NCIC CTG Trial IND.184

OBJECTIVE

Vascular endothethial growth factor (VEGF) and stem cell factor (c-KIT) signaling may play a role in the development and progression of cervical carcinoma. Sunitinib malate is an oral, multi-targeted tyrosine kinase inhibitor that inhibits receptors for VEGF, c-Kit and platelet-derived growth factor. This multi-centre phase II study was performed to evaluate the activity of sunitinib in women with locally advanced or metastatic cervical carcinoma who had received up to one prior line of chemotherapy for advanced disease.

METHODS

Sunitinib, 50 mg/day, was administered in 6-week cycles (4 weeks on followed by 2 weeks off treatment). The primary endpoint was the objective response rate.

RESULTS

Sixteen (84%) of 19 patients enrolled had stable disease (median duration 4.4 months, 2.3-17 months), but no objective response was observed. Median time to progression was 3.5 months (range, 2.7-7.0 months). Four patients had fistulae develop on study treatment and an additional patient developed a fistula 3.5 months after discontinuation of therapy. All five patients had received either prior chemoradiation or radiation.

CONCLUSIONS

A higher rate of fistula formation (26.3%) was observed than would be expected and is of concern. Sunitinib has insufficient activity as a single agent in cervical cancer to warrant further investigation.

Large-scale analysis of protein expression changes in human keratinocytes immortalized by human papilloma virus type 16 E6 and E7 oncogenes

Background

Infection with high-risk type human papilloma viruses (HPVs) is associated with cervical carcinomas and with a subset of head and neck squamous cell carcinomas. Viral E6 and E7 oncogenes cooperate to achieve cell immortalization by a mechanism that is not yet fully understood. Here, human keratinocytes were immortalized by long-term expression of HPV type 16 E6 or E7 oncoproteins, or both. Proteomic profiling was used to compare expression levels for 741 discrete protein features.

Results

Six replicate measurements were performed for each group using two-dimensional difference gel electrophoresis (2D-DIGE). The median within-group coefficient of variation was 19–21%. Significance of between-group differences was tested based on Significance Analysis of Microarray and fold change. Expression of 170 (23%) of the protein features changed significantly in immortalized cells compared to primary keratinocytes. Most of these changes were qualitatively similar in cells immortalized by E6, E7, or E6/7 expression, indicating convergence on a common phenotype, but fifteen proteins (~2%) were outliers in this regulatory pattern. Ten demonstrated opposite regulation in E6- and E7-expressing cells, including the cell cycle regulator p16^INK4a; the carbohydrate binding protein Galectin-7; two differentially migrating forms of the intermediate filament protein Cytokeratin-7; HSPA1A (Hsp70-1); and five unidentified proteins. Five others had a pattern of expression that suggested cooperativity between the co-expressed oncoproteins. Two of these were identified as forms of the small heat shock protein HSPB1 (Hsp27).

Conclusion

This large-scale analysis provides a framework for understanding the cooperation between E6 and E7 oncoproteins in HPV-driven carcinogenesis.

Oncogenic activities of human papillomaviruses

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

Hypoxia-specific stabilization of HIF-1alpha by human papillomaviruses

Human papillomaviruses (HPV) are the causative agents of cervical cancer and have been shown to increase expression of pro-angiogenic factors from infected cells. Many angiogenic factors are regulated by hypoxia inducible factor 1alpha (HIF-1alpha). We investigated whether HPV31 affects the levels of HIF-1alpha under normal and hypoxic conditions. Our studies indicate that cells containing complete HPV31 genomes showed enhanced levels of HIF-1alpha upon treatment with the hypoxia mimic DFO, which resulted from protein stabilization and led to increased expression of some but not all HIF-1alpha target genes. Both HPV E6 and E7 were able independently to enhance induction of HIF-1alpha upon DFO treatment. Enhancement of HIF-1alpha stability was not restricted to high-risk HPV types, as HPV11, a low risk HPV type, mediated a similar effect. These findings shed light on mechanisms by which HPV contributes to angiogenesis both in benign cervical lesions and in cervical cancers.

Markers of angiogenesis in high-risk, early-stage cervical cancer: A Gynecologic Oncology Group study

OBJECTIVES

To determine whether markers of tumor angiogenesis were associated with progression-free survival (PFS) and overall survival (OS) in women with high-risk, early-stage cervical cancer treated on a phase III trial.

METHODS

One hundred seventy-three tumor specimens were analyzed by semi-quantitative immunohistochemical (IHC) staining for vascular endothelial growth factor (VEGF, pro-angiogenesis factor), thrombospondin-1 (TSP-1, anti-angiogenesis factor), CD31 (non-specific endothelial marker), and CD105 (tumor-specific endothelial marker). Tumoral histoscores (HS) were calculated for VEGF using the formula: [% cells positivex(intensity+1)]. TSP-1 specimens were categorized as negative or positive. CD31 and CD105 microvessel density (MVD) "hotspots" were counted in three 20x high-power fields. Associations between angiogenesis markers and survival were evaluated.

RESULTS

TSP-1 expression was observed in 65% of cases while 66% expressed high VEGF (>or=200), 34% exhibited high CD31 (CD31>or=110) and 66% displayed high CD105 (CD105>or=28). In univariate analyses CD31 MVD, but not tumor TSP-1, was associated with improved PFS (HR=0.37; 95% CI=0.18-0.76; p=0.007) and OS (HR=0.37; 95% CI=0.17-0.79; p=0.010). After adjusting for prognostic clinical covariates, high CD31 MVD, but not TSP-1, VEGF or CD105 MVD, was an independent prognostic factor for PFS (HR=0.36; 95% CI=0.17-0.75; p=0.006) and OS (HR=0.36; 95% CI=0.17-0.79; p=0.010).

CONCLUSIONS

Tumor angiogenesis measured by CD31 MVD is an independent prognostic factor for both PFS and OS in high-risk, early-stage cervical cancer. We hypothesize that this finding may be explained by improved treatment response in well-vascularized, well-oxygenated tumors.

The human papillomavirus E7 oncoprotein

The human papillomavirus (HPV) E7 oncoprotein shares functional similarities with such proteins as adenovirus E1A and SV40 large tumor antigen. As one of only two viral proteins always expressed in HPV-associated cancers, E7 plays a central role in both the viral life cycle and carcinogenic transformation. In the HPV viral life cycle, E7 disrupts the intimate association between cellular differentiation and proliferation in normal epithelium, allowing for viral replication in cells that would no longer be in the dividing population. This function is directly reflected in the transforming activities of E7, including tumor initiation and induction of genomic instability.

Gene silencing with siRNA targeting E6/E7 as a therapeutic intervention in a mouse model of cervical cancer

OBJECTIVE

Selective silencing of HPV oncogenes using short interfering RNA (siRNA) blocks E6/E7 expression and restores normal p53 and Rb function. Our objective was to determine if siRNA targeting E6/E7 would inhibit the growth of established tumors in a mouse model of cervical cancer.

METHODS

In vitro studies were performed using unique siRNA sequences to confirm their ability to target and reduce E6/E7 mRNA and restore functioning p53. Next, siRNA targeting lamin was injected daily for three days into tumors established from HPV 16 positive CaSki human cervical cancer cells. Immunohistochemistry and branched DNA gene quantification were used to determine distribution and duration of activity of these siRNA. For our therapeutic studies tumors were directly injected with siRNA targeting E6/E7, non-targeting control siRNA, or saline. In preliminary experiments injections were daily or every three days for a total of three doses. A second therapeutic experiment utilized every three day dosing for 35 days. Tumor volume, growth curves and E7 mRNA levels were assessed.

RESULTS

The two most active siRNA sequences resulted in a 67% and 71% reduction in E6/E7 mRNA. Fluorescent lamin siRNA was visualized up to 120 h after the initial tumor injection and was evenly distributed throughout the tumors. IHC showed lamin expression to be inhibited by 68% and 75% when compared to controls at 54 and 120 h respectively. In our preliminary therapeutic intervention experiments there was no significant difference in tumor growth between the treatment groups when mice were treated with three daily injections (p=0.41). However, when treated every third day for three injections final tumor volume was less in animals injected with siRNA sequences A (78% reduction; p<0.0001) and G (60% reduction; p=0.005) compared to saline injection. Tumors showed a corresponding decrease in E6/E7 mRNA. Extended treatment with siRNA completely or nearly eradicated tumors in 70% of the animals.

CONCLUSION

Therapeutic siRNA targeting E6/E7 significantly inhibits tumor growth in this mouse model of cervical cancer. Further investigation is needed to determine optimal dosing and route of delivery.

Genome wide expression analysis in HPV16 cervical cancer: identification of altered metabolic pathways

Background

Cervical carcinoma (CC) is a leading cause of death among women worldwide. Human papilloma virus (HPV) is a major etiological factor in CC and HPV 16 is the more frequent viral type present. Our aim was to characterize metabolic pathways altered in HPV 16 tumor samples by means of transcriptome wide analysis and bioinformatics tools for visualizing expression data in the context of KEGG biological pathways.

Results

We found 2,067 genes significantly up or down-modulated (at least 2-fold) in tumor clinical samples compared to normal tissues, representing ~3.7% of analyzed genes. Cervical carcinoma was associated with an important up-regulation of Wnt signaling pathway, which was validated by in situ hybridization in clinical samples. Other up-regulated pathways were those of calcium signaling and MAPK signaling, as well as cell cycle-related genes. There was down-regulation of focal adhesion, TGF-β signaling, among other metabolic pathways.

Conclusion

This analysis of HPV 16 tumors transcriptome could be useful for the identification of genes and molecular pathways involved in the pathogenesis of cervical carcinoma. Understanding the possible role of these proteins in the pathogenesis of CC deserves further studies.

The human papillomavirus type 18 E6 oncoprotein induces Vascular Endothelial Growth Factor 121 (VEGF121) transcription from the promoter through a p53-independent mechanism

Altered angiogenic response is associated with high-grade cervical dysplasia and with invasive squamous carcinoma of the cervix. Vascular Endothelial Growth Factor (VEGF) is one of the most potent inducers of angiogenesis and is up-regulated in carcinoma of the cervix. Infection by high-risk human papillomavirus and persistent expression of viral oncogene E6 are etiologically linked to the development of cervical cancer. E6 is able to immortalize cells and induce malignant transformation by inactivating p53. In cervical cancer, regulation of VEGF expression is poorly described. Thus, we investigated whether E6 oncoprotein could regulate VEGF expression in HPV18-positive cervical cancer-derived HeLa cells harboring a wild-type p53. The alternative splicing of vegf mRNA renders three major isoforms of 121, 165 and 189 amino-acids in humans. We have designed isoform specific real time QRT-PCR assays to quantitate vegf transcripts and VEGF121 was the predominant isoform. Silencing HPV18 E6 mRNA with specific siRNA reduced VEGF121 expression by at least 50% whereas silencing of p53 did not alter its expression. Treatment with cycloheximide did not inhibit E6-induced VEGF121 expression. Collectively, these results suggest that HPV18 E6 oncoprotein contributes to tumor angiogenesis by inducing VEGF transcription from the promoter in a p53-independent manner.

Overexpression of human papillomavirus type 16 oncoproteins enhances hypoxia-inducible factor 1 alpha protein accumulation and vascular endothelial growth factor expression in human cervical carcinoma cells

PURPOSE

Human papillomavirus (HPV)-16 oncoproteins, E6 and E7, are associated with enhanced tumor angiogenesis in human cervical cancers. The purpose of this study was (a) to investigate whether expression of HPV-16 E6 and E7 oncoproteins induces hypoxia-inducible factor 1 alpha (HIF-1 alpha) and vascular endothelial growth factor expression in cervical cancer cells; and (b) to assess the effect of resveratrol on 16 E6- and E7-induced HIF-1 alpha and VEGF gene expression.

EXPERIMENTAL DESIGN

Human cervical cancer cell lines C-33A and HeLa were transiently cotransfected with pSG5-HPV-16 E6 or 16 E7 constructs along with HIF-1 alpha small interfering RNA (siRNA) or nonspecific siRNA. The expression of HIF-1 alpha/VEGF was measured using real-time PCR, Western blot analysis, or ELISA. The in vitro angiogenic activity induced by 16 E6- and E7-transfected cells was examined. The effect of resveratrol on oncoprotein-induced HIF-1 alpha/VEGF expression and in vitro angiogenesis was investigated.

RESULTS

HPV-16 E6- and E7-transfected cervical cancer cells express increased HIF-1 alpha protein and VEGF expression. These stimulatory effects were abrogated by cotransfection with either HIF-1 alpha siRNA or treatment with resveratrol. Blocking extracellular signal-regulated kinase 1/2 (ERK 1/2) and phosphoinositide-3-kinase by PD98059 and LY294002, respectively, abolished 16 E6- and E7-induced HIF-1 alpha and VEGF expression. Functionally, we showed that HPV-16 E6- and E7-transfected cervical cancer cells stimulated in vitro capillary or tubule formation, and these angiogenic effects could be abolished either by cotransfection with HIF-1 alpha siRNA or by treatment with resveratrol.

CONCLUSION

HPV-16 oncoproteins contribute to enhanced angiogenesis in cervical cancer cells via HIF-1 alpha-dependent VEGF expression. Resveratrol suppresses 16 E6- and E7-induced HIF-1 alpha-mediated angiogenic activity and, thus, is a promising chemotherapeutic agent for human cervical cancer.

Human papillomavirus type 16 E7 oncoprotein associates with the cullin 2 ubiquitin ligase complex, which contributes to degradation of the retinoblastoma tumor suppressor

Human papillomavirus type 16 (HPV16) and other high-risk HPVs are etiologically linked to the development of cervical carcinomas and contribute to a number of other tumors of the anogenital tract, as well as oral cancers. The high-risk HPV E6 and E7 oncoproteins are consistently expressed in cervical cancer cells and are necessary for the induction and maintenance of the transformed phenotype. An important aspect of HPV16 E7's oncogenic activities is destabilization of the retinoblastoma tumor suppressor (pRB) through a ubiquitin/proteasome-dependent mechanism, although the exact molecular mechanism is unknown. Here, we report that HPV16 E7 is associated with an enzymatically active cullin 2 ubiquitin ligase complex and that the HPV16 E7/pRB complex contains cullin 2. Depletion of cullin 2 by RNA interference causes increased steady-state levels and stability of pRB in HPV16 E7-expressing cells, and ectopic expression of HPV16 E7 and the cullin 2 complex leads to pRB ubiquitination in vivo. Hence, we propose that the HPV16 E7-associated cullin 2 ubiquitin ligase complex contributes to aberrant degradation of the pRB tumor suppressor in HPV16 E7-expressing cells.

Human papillomavirus causes an angiogenic switch in keratinocytes which is sufficient to alter endothelial cell behavior

One of the requirements for tumor growth is the ability to recruit a blood supply, a process known as angiogenesis. Angiogenesis begins early in the progression of cervical disease from mild to severe dysplasia and on to invasive cancer. We have previously reported that expression of human papillomavirus type 16 E6 and E7 (HPV16 E6E7) proteins in primary foreskin keratinocytes (HFKs) decreases expression of two inhibitors and increases expression of two angiogenic inducers [Toussaint-Smith, E., Donner, D.B., Roman, A., 2004. Expression of human papillomavirus type 16 E6 and E7 oncoproteins in primary foreskin keratinocytes is sufficient to alter the expression of angiogenic factors. Oncogene 23, 2988-2995]. Here we report that HPV-induced early changes in the keratinocyte phenotype are sufficient to alter endothelial cell behavior both in vitro and in vivo. Conditioned media from HPV16 E6E7 expressing HFKs as well as from human cervical keratinocytes containing the intact HPV16 were able to stimulate proliferation and migration of human microvascular endothelial cells. In addition, introduction of the conditioned media into immunocompetent mice using a Matrigel plug model resulted in a clear angiogenic response. These novel data support the hypothesis that HPV proteins contribute not only to the uncontrolled keratinocyte growth seen following HPV infection but also to the angiogenic response needed for tumor formation.

High human papillomavirus oncogene mRNA expression and not viral DNA load is associated with poor prognosis in cervical cancer patients

PURPOSE

Cervical cancer is now known to be caused by infection with an oncogenic type of the human papillomavirus (HPV). However, little is known about the continued role of HPV once cancer has been established. Here, we describe the quantitative relation between HPV DNA copy number and mRNA expression of the viral oncogenes (E6 and E7) and the prognostic value of both measures in cervical cancer patients.

EXPERIMENTAL DESIGN

We studied the number of viral DNA copies and the level of HPV E6/E7 mRNA expression in 75 HPV 16-positive or HPV 18-positive International Federation of Gynecology and Obstetrics stage Ib and IIa cervical cancer patients. Measurements were done with quantitative PCR. DNA copy number analysis was done on pure tumor cell samples enriched with flow sorting. mRNA expression data were compensated for the percentage of tumor cells included.

RESULTS

The number of viral DNA copies was not predictive of survival in cervical cancer patients. In contrast, high HPV E6/E7 mRNA expression was strongly related to an unfavorable prognosis (P = 0.006). In a multivariate Cox model for overall survival, including all known prognostic variables and stratified for HPV type, the level of E6/E7 mRNA expression was an independent prognostic indicator, second only to lymph node status. No correlation was observed between DNA copy number and the level of HPV E6/E7 mRNA expression, which reflects that not all DNA copies are equally transcriptionally active.

CONCLUSIONS

Cervical cancer patients with high HPV E6/E7 oncogene mRNA expression have a worse survival independently from established prognostic factors.

Cidofovir administered with radiation displays an antiangiogenic effect mediated by E6 inhibition and subsequent TP53-dependent VEGF repression in HPV18+ cell lines

Therapeutic administration of the antiviral agent cidofovir with radiation markedly enhanced the antitumor effect of ionizing radiation in cells of two HPV18+ human cervical carcinoma cell lines. Although this potent radiosensitizing effect was associated with repression of the viral oncoproteins E6/ E7 and restoration of TP53 as shown previously, additional mechanisms may be involved. In the present study, we investigated the antiangiogenic effect of the combination of cidofovir and radiation in cells of two HPV18+ cervical cancer cell lines, HeLa and ME180, and assessed the molecular mechanisms associated with the antiangiogenic effect observed. Cells were exposed to cidofovir (10 microg/ml) and irradiated (1-9 Gy). The angiogenic response was studied in vitro by a matrigel invasion assay. Modulations of E6, TP53 and VEGF mRNA and protein levels were studied by real-time RT-PCR, Western blot analysis and ELISA, respectively. Then a double RNA interference approach was used to analyze the connection between E6/TP53 and VEGF. The combination of cidofovir and radiation had a potent antiangiogenic effect. It induced E6 inhibition, restoration of TP53, and reduction of the proangiogenic phenotype of HPV18+ cells associated with VEGF inhibition. A siRNA strategy showed an anti-VEGF action of the combination mediated directly by E6 inhibition and TP53 restoration, since E6 siRNA inhibited VEGF whereas co-transfection with E6 and TP53 siRNA abrogated the anti-VEGF effect. This study showed that the combination of cidofovir with ionizing radiation has an antiangiogenic effect associated with VEGF inhibition subsequent to E6 inhibition and TP53 restoration.