Structural dynamic studies on identification of EGCG analogues for the inhibition of Human Papillomavirus E7

High risk human papillomaviruses are highly associated with the cervical carcinoma and the other genital tumors. Development of cervical cancer passes through the multistep process initiated from benign cyst to increasingly severe premalignant dysplastic lesions in an epithelium. Replication of this virus occurs in the fatal differentiating epithelium and involves in the activation of cellular DNA replication proteins. The oncoprotein E7 of human papillomavirus expressed in the lower epithelial layers constrains the cells into S-phase constructing an environment favorable for genome replication and cell proliferation. To date, no suitable drug molecules exist to treat HPV infection whereas anticipation of novel anti-HPV chemotherapies with distinctive mode of actions and identification of potential drugs are crucial to a greater extent. Hence, our present study focused on identification of compounds analogue to EGCG, a green tea molecule which is considered to be safe to use for mammalian systems towards treatment of cancer. A three dimensional similarity search on the small molecule library from natural product database using EGCG identified 11 potential small molecules based on their structural similarity. The docking strategies were implemented with acquired small molecules and identification of the key interactions between protein and compounds were carried out through binding free energy calculations. The conformational changes between the apoprotein and complexes were analyzed through simulation performed thrice demonstrating the dynamical and structural effects of the protein induced by the compounds signifying the domination. The analysis of the conformational stability provoked us to describe the features of the best identified small molecules through electronic structure calculations. Overall, our study provides the basis for structural insights of the identified potential identified small molecules and EGCG. Hence, the identified analogue of EGCG can be potent inhibitors against the HPV 16 E7 oncoprotein.

Immunotherapy Targeting HPV16/18 Generates Potent Immune Responses in HPV-Associated Head and Neck Cancer

PURPOSE

Clinical responses with programmed death (PD-1) receptor-directed antibodies occur in about 20% of patients with advanced head and neck squamous cell cancer (HNSCCa). Viral neoantigens, such as the E6/E7 proteins of HPV16/18, are attractive targets for therapeutic immunization and offer an immune activation strategy that may be complementary to PD-1 inhibition.

PATIENTS AND METHODS

We report phase Ib/II safety, tolerability, and immunogenicity results of immunotherapy with MEDI0457 (DNA immunotherapy targeting HPV16/18 E6/E7 with IL12 encoding plasmids) delivered by electroporation with CELLECTRA constant current device. Twenty-two patients with locally advanced, p16⁺ HNSCCa received MEDI0457.

RESULTS

MEDI0457 was associated with mild injection site reactions, but no treatment-related grade 3-5 adverse events (AE) were noted. Eighteen of 21 evaluable patients showed elevated antigen-specific T-cell activity by IFNγ ELISpot, and persistent cellular responses surpassing 100 spot-forming units (SFUs)/10⁶ peripheral blood mononuclear cells (PBMCs) were noted out to 1 year. Induction of HPV-specific CD8⁺ T cells was observed. MEDI0457 shifted the CD8⁺/FoxP3⁺ ratio in 4 of 5 post immunotherapy tumor samples and increased the number of perforin⁺ immune infiltrates in all 5 patients. One patient developed metastatic disease and was treated with anti-PD-1 therapy with a rapid and durable complete response. Flow-cytometric analyses revealed induction of HPV16-specific PD-1⁺ CD8⁺ T cells that were not found prior to MEDI0547 (0% vs. 1.8%).

CONCLUSIONS

These data demonstrate that MEDI0457 can generate durable HPV16/18 antigen-specific peripheral and tumor immune responses. This approach may be used as a complementary strategy to PD-1/PD-L1 inhibition in HPV-associated HNSCCa to improve therapeutic outcomes.

Identification and characterization of small molecule antagonists of pRb inactivation by viral oncoproteins

The retinoblastoma protein pRb is essential for regulating many cellular activities through its binding and inhibition of E2F transcription activators, and pRb inactivation leads to many cancers. pRb activity can be perturbed by viral oncoproteins including human papillomavirus (HPV) that share an LxCxE motif. Because there are no treatments for existing HPV infection leading to nearly all cervical cancers and other cancers to a lesser extent, we screened for compounds that inhibit the ability of HPV-E7 to disrupt pRb/E2F complexes. This lead to the identification of thiadiazolidinedione compounds that bind to pRb with mid-high nanomolar dissociation constants, are competitive with the binding of viral oncoproteins containing an LxCxE motif, and are selectively cytotoxic in HPV-positive cells alone and in mice. These inhibitors provide a promising scaffold for the development of therapies to treat HPV-mediated pathologies.

Efficacy of TRAIL treatment against HPV16 infected cervical cancer cells undergoing senescence following siRNA knockdown of E6/E7 genes

In this study we investigated E6 and E7 oncogenes from the Human Papilloma Virus as targets for siRNA knockdown in order to boost the efficacy of the anti-cancer drug 'tumor necrosis factor-related apoptosis inducing ligand' (TRAIL). SiHa cells were treated with TRAIL following transfection with E6/E7 siRNA and the expression of death receptors DR4 and DR5, cell viability, apoptosis, senescence and cell cycle analysis were undertaken using flow cytometry, MTT viability assay and cellular β-galactosidase activity assays. E6/E7 siRNA resulted in significant upregulation of death receptors DR4 and DR5 but did not result in an enhanced sensitivity to TRAIL. Our results indicate that E6/E7-siRNA induces senescence rather than apoptosis in SiHa cells. The occurrence of senescence in drug resistant cervical cancer cells such as the SiHa cell line by E6/E7 siRNA, among other factors, may prevent TRAIL induced activation of extrinsic and intrinsic pathways that lead to apoptotic cell death. Our findings are significant for combinatorial strategies for cancer therapy since the induction of senescence can preclude apoptosis rendering cells to be recalcitrant to TRAIL treatment.

Novel anti-metastatic action of cidofovir mediated by inhibition of E6/E7, CXCR4 and Rho/ROCK signaling in HPV tumor cells

Cervical cancer is frequently associated with HPV infection. The expression of E6 and E7 HPV oncoproteins is a key factor in its carcinogenicity and might also influence its virulence, including metastatic conversion. The cellular mechanisms involved in metastatic spread remain elusive, but pro-adhesive receptors and their ligands, such as SDF-1α and CXCR4 are implicated. In the present study, we assessed the possible relationship between SDF-1α/CXCR4 signaling, E6/E7 status and the metastatic process. We found that SDF-1α stimulated the invasion of E6/E7-positive cancer cell lines (HeLa and TC-1) in Matrigel though CXCR4 and subsequent Rho/ROCK activation. In pulmonary metastatic foci generated by TC-1 cells IV injection a high proportion of cells expressed membrane-associated CXCR4. In both cases models (in vitro and in vivo) cell adhesion and invasion was abrogated by CXCR4 immunological blockade supporting a contribution of SDF-1α/CXCR4 to the metastatic process. E6 and E7 silencing using stable knock-down and the approved anti-viral agent, Cidofovir decreased CXCR4 gene expression as well as both, constitutive and SDF-1α-induced cell invasion. In addition, Cidofovir inhibited lung metastasis (both adhesion and invasion) supporting contribution of E6 and E7 oncoproteins to the metastatic process. Finally, potential signals activated downstream SDF-1α/CXCR4 and involved in lung homing of E6/E7-expressing tumor cells were investigated. The contribution of the Rho/ROCK pathway was suggested by the inhibitory effect triggered by Cidofovir and further confirmed using Y-27632 (a small molecule ROCK inhibitor). These data suggest a novel and highly translatable therapeutic approach to cervix cancer, by inhibition of adhesion and invasion of circulating HPV-positive tumor cells, using Cidofovir and/or ROCK inhibition.