Apoptosis induced by an antagonist peptide against HPV16 E7 in vitro and in vivo via restoration of p53

A novel intracellular nanobody against HPV16 E6 oncoprotein

Cervical cancer occurs as a result of the persistent infection of high-risk human papillomavirus (HPV). HPV16 oncoproteins E6 and E7 exert different and concerted pro-tumor actions in cell transformation and malignance maintenance in various m echanisms. Nanobody expressed as "intracellular antibodies" (intrabodies) can target intracellular antigens to hamper their function efficaciously and specifically. In this work, phage-display approach was employed to select the high affinity HPV16 E6-specific nanobody, nanobody Nb9 against HPV16 E6 was selected. Nb9 has high affinity (Kaff =6.3 × 10⁸ M^-) and can specifically bind endogenous HPV16 E6 protein in HPV16 positive CaSki and SiHa cells. In Nb9 overexpressed SiHa and CaSki cells, nucleus localization of HPV16 E6 was inhibited, p53 inactivation was prevented and increased apoptosis was observed. Moreover, tumor growth was inhibited in mouse xenograft model. Taken together, our results suggested that nanobody Nb9 could be a useful inhibitor for HPV16 E6 function and particularly appropriate for the treatment of HPV-associated disease.

Generation of affibody molecules specific for HPV16 E7 recognition

Cervical cancer caused by infection with high-risk human papillomavirus remains to be the most deadly gynecologic malignancy worldwide. It is well documented that persistent expression of two oncogenes (E6/E7) plays the key roles in cervical cancer. Thus, in vivo detection of the oncoproteins is very important for the diagnosis of the cancer. Recently, affibody molecules have been demonstrated to be a powerful targeting probe for tumor-targeted imaging and diagnosis. In this study, four HPV16 E7-binding affibody molecules (Z HPV16 E7127, Z HPV16E7301, Z HPV16E7384 and Z HPV16E7745) were screened from a phage-displayed peptide library and used for molecular imaging in tumor-bearing mice. Biosensor binding analyses showed first that the four affibody molecules bound to HPV16 E7 with very high affinity and specificity. They co-localized with E7 protein only in two HPV16-positive cancer cells (SiHa and CaSki). Furthermore, affibody ZHPV16E7384 was conjugated with Dylight755 and used for in vivo tumor-imaging. Strongly high-contrast tumor retention of this affibody only occurred in HPV16-derived tumors of mice as early as 30 min post-injection, not in HPV-negative and HPV18-derived tumors. The accumulation of Dylight755-conjugated ZHPV16E7384 in tumor was achieved over a longer time period (24 h). The data here provide strong evidence that E7-specific affibody molecules have great potential used for molecular imaging and diagnosis of HPV-induced cancers.

Transforming properties of Felis catus papillomavirus type 2 E6 and E7 putative oncogenes in vitro and their transcriptional activity in feline squamous cell carcinoma in vivo

Felis catus papillomavirus type 2 (FcaPV2) DNA is found in feline cutaneous squamous cell carcinomas (SCCs); however, its biological properties are still uncharacterized. In this study, we successfully expressed FcaPV2 E6 and E7 putative oncogenes in feline epithelial cells and demonstrated that FcaPV2 E6 binds to p53, impairing its protein level. In addition, E6 and E7 inhibited ultraviolet B (UVB)-triggered accumulation of p53, p21 and pro-apoptotic markers such as Cleaved Caspase3, Bax and Bak, suggesting a synergistic action of the virus with UV exposure in tumour pathogenesis. Furthermore, FcaPV2 E7 bound to feline pRb and impaired pRb levels, resulting in upregulation of the downstream pro-proliferative genes Cyclin A and Cdc2. Importantly, we demonstrated mRNA expression of FcaPV2 E2, E6 and E7 in feline SCC samples, strengthening the hypothesis of a causative role in the development of feline SCC.

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.

An RNA aptamer provides a novel approach for the induction of apoptosis by targeting the HPV16 E7 oncoprotein

BACKGROUND

Human papillomavirus 16 (HPV16) is a high-risk DNA tumour virus, which is a major causative agent of cervical cancer. Cellular transformation is associated with deregulated expression of the E6 and E7 oncogenes. E7 has been shown to bind a number of cellular proteins, including the cell cycle control protein pRb. In this study, RNA aptamers (small, single-stranded oligonucleotides selected for high-affinity binding) to HPV16 E7 were employed as molecular tools to further investigate these protein-protein interactions.

METHODOLOGY/PRINCIPAL FINDINGS

This study is focused on one aptamer (termed A2). Transfection of this molecule into HPV16-transformed cells resulted in inhibition of cell proliferation (shown using real-time cell electronic sensing and MTT assays) due to the induction of apoptosis (as demonstrated by Annexin V/propidium iodide staining). GST-pull down and bead binding assays were used to demonstrate that the binding of A2 required N-terminal residues of E7 known to be involved in interaction with the cell cycle control protein, pRb. Using a similar approach, A2 was shown to disrupt the interaction between E7 and pRb in vitro. Furthermore, transfection of HPV16-transformed cells with A2 appeared to result in the loss of E7 and rise in pRb levels, as observed by immunoblotting.

CONCLUSIONS/SIGNIFICANCE

This paper includes the first characterisation of the effects of an E7 RNA aptamer in a cell line derived from a cervical carcinoma. Transfection of cells with A2 was correlated with the loss of E7 and the induction of apoptosis. Aptamers specific for a number of cellular and viral proteins have been documented previously; one aptamer (Macugen) is approved for clinical use and several others are in clinical trials. In addition to its role as a molecular tool, A2 could have further applications in the future.

Functional study of dextran-graft-poly((2-dimethyl amino)ethyl methacrylate) gene delivery vector for tumor therapy

The obstacle of gene therapy is the shortage of efficient delivery system. The development of the gene delivery system with high transfection efficiency and low toxicity appears to be crucial. Recently, we reported that the dextran-graft-poly((2-dimethyl amino)ethyl methacrylate) (DPD) can be potentially used as efficient gene vector. Herein, DPD was systematically studied for its potential in tumor gene therapy. DPD was synthesized and characterized by agarose gel electrophoresis, particle size and zeta potential. The particle size and zeta potential of the DPD/enhanced green fluorescent protein (pEGFP-C1) plasmid complexes at various N/P ratios were 130-150 nm and about 40 mV, respectively. The results showed that DPD exhibit a higher transfection effect compared with Lipofectamine 2K (Lipo 2K), a commercialized vector. The possibility of DPD in gene therapy was evaluated using p53, a gene that has been wildly applied in the research of cancer gene therapy. DPD/pEGFP-C1-p53 complex was found to be able to inhibit tumor cell proliferation through cell cycle arrest and apoptosis. Moreover, the tumor growth was found to be restrained when DPD/pEGFP-C1-p53 complex was used in a xenograft MCF7 tumor model in vivo. These observations indicated that DPD/pEGFP-C1-p53 complex may be considered to be an efficient delivery system for tumor gene therapy.

Interference with p53 functions in human viral infections, a target for novel antiviral strategies?

Viral infections cause a major stress in host cells. The cellular responses to stress are mediated by p53, which by deregulation of cell cycle and apoptosis, may also be part of the host cell reaction to fight infections. Therefore, during evolutionary viral adaptation to host organisms, viruses have developed strategies to manipulate host cell p53 dependent pathways to facilitate their viral life cycles. Thus, interference with p53 function is an important component in viral pathogenesis. Many viruses have proteins that directly affect p53, whereas others alter the regulation of p53 in an indirect manner, mediated by Hdm2 or Akt, or induction of interferon. Rescue of p53 activity is becoming an area of therapeutic development in oncology. It might be feasible that manipulation of p53 mediated responses can become a therapeutic option to limit viral replication or dissemination. In this report, the mechanisms by which viral proteins manipulate p53 responses are reviewed, and it is proposed that a pharmacological rescue of p53 functions might help to control viral infections.