New peptide binders for HPV16 E6 and E7 oncoproteins: identification and application in the development of therapies for HPV-induced tumors

Author(s)

Heloise Ranucci Luchiari

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Conjunto das Químicas (IQ e FCF) (CQ/DBDCQ)
• Defense date: 2023-02-10

Examining board members

Ricardo José Giordano; Daniela Sanchez Bassères; Emmanuel Dias Neto; Enrique Mario Boccardo Pierulivo

• Advisor: Ricardo José Giordano; Luisa Lina Villa

Abstract

The Human papillomavirus (HPV) is responsible for almost 700,000 new cancer cases annually, and for many asymptomatic infections that can progress to benign, pre-malign and malign lesions. Although the prophylactic HPV vaccines can prevent new infections, it does not benefit already infected individuals and there is no specific treatment for them. The E6 and E7 oncoproteins, encoded by the viral genome, highjack several cellular targets and are essential to achieve and maintain the malignant phenotype in HPV-induced tumors. E6 and E7 have no homology with cellular proteins and its silencing can lead cells to apoptosis, making them optimal targets for the development of new therapies to fight HPV. Thus, the aim of this study was to identify inhibitory peptide ligands for E6 and E7 oncoproteins of the highly prevalent HPV 16 that can be useful for the development of new specific treatments for HPV tumorigenesis and infection. Using phage display technology and our own libraries, we found novel peptide binders for E6 and E7. Peptides selected against E6 were highly specific and shared a central motif with an acidic core flanked by hydrophobic residues. Also, the new E6 binders were able to bind to the hydrophobic pocket of the oncoprotein, previously described as the binding pocket for many cellular partners of E6. This result was validated by experimental and in silico approaches. Also, the novel peptides were tested in HPV-positive cancer cell lines, but they had no effects on cell viability. Thus, we developed a displacement screening platform based on the peptide-oncoprotein interaction to search for small compounds that bind to E6. Using this assay, we selected two compounds with effects on HPVpositive cell lines viability that can be optimized to the development of new HPV-specific therapies. It can also be useful to the screening of other molecules to find potential binders for E6. Moreover, docking and molecular dynamic simulations shed light on novel interactions between our peptide and E6, providing tools for rational design of new drugs. We hope that this work brings contribution to the development of specific treatments to benefit patients that suffer from lesions and tumors induced by HPV infection. (AU)

• FAPESP's process: 17/19801-4 - Identification of inhibitory peptides directed toward E6 and E7 HPV oncoproteins for the development of novel therapies for tumors induced by HPV
• Grantee: Heloise Ranucci Luchiari
• Support Opportunities: Scholarships in Brazil - Doctorate