Taxifolin and Lucidin as Potential E6 Protein Inhibitors: p53 Function Re-Establishment and Apoptosis Induction in Cervical Cancer Cells

Cervical cancer (CC) is considered the 4^th most common cause of death in women worldwide, with over 99% of cases related to human papilloma virus (HPV) infection. The development of this pathology is related to the expression of the HPV E6 and E7 proteins, since they can interfere with the cellular regulatory mechanisms potentiated by tumor suppressor proteins, such as p53 and pRB proteins. Current treatments as surgery, radiotherapy or chemotherapy affect normal tissues and have several side effects which can cause discomfort and reduce quality of life for patients. The relevant role of E6 protein in the development and progression of HPV infection to cervical lesion or even invasive carcinoma has stimulated the interest of scientists to find new and specific anticancer agents. Thus, this research project, led by Ângela Sousa, joined researchers from CICS-UBI (Covilhã), UCIBIO (Lisbon), CNC (Coimbra), UNESP (Brazil) and AIMMSCR (India) to apply different computational studies and select compounds with the potential to inhibit the E6 protein. The action of 3 compounds (alizarin, taxifolin and lucidin) suggested by in silico (computational) studies was evaluated in in vitro studies with HPV-positive (Caski, HeLa) and HPV-negative (C33A, NHEK) cells. The in vitro studies demonstrated that taxifolin and lucidin reduce cell viability, increase p53 protein levels, and induce apoptosis in HPV-positive cells without affecting healthy cells. Thus, this work allowed the discovery of 2 natural compounds capable of inhibiting the function of the E6 protein by restoring the p53 protein levels and inducing the death of cancer cells.

Authors and Affiliations:

Diana Gomes ^1,2,3, Shivani Yaduvanshi⁴, Samuel Silvestre ^1,5,6,7, Ana Paula Duarte ^1,5,7, Adriana O. Santos¹, Christiane P. Soares ⁸, Veerendra Kumar⁴, Luís Passarinha ^1,2,3,5 and Ângela Sousa ¹

¹  CICS-UBI–Health Sciences Research Centre, University of Beira Interior, Avenida Infante D. Henrique, 6200-506 Covilhã, Portugal;

²  Associate Laboratory i4HB - Institute for Health and Bioeconomy, Faculdade de Ciências e Tecnologia, Universidade NOVA, 2819-516 Caparica, Portugal;

³  UCIBIO–Applied Molecular Biosciences Unit, Departamento de Química/Departamento Ciências da Vida, Faculdade de Ciências e Tecnologia, Universidade NOVA de Lisboa, 2829-516 Caparica, Portugal;

⁴  Amity Institute of Molecular Medicine and Stem Cell Research (AIMMSCR), Amity University, 201303 Noida Uttar Pradesh, India;

⁵  Laboratório de Fármaco-Toxicologia-UBIMedical, Universidade da Beira Interior, 6200-284 Covilhã, Portugal;

⁶  CNC-Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra 3004-504, Portugal;

⁷  C4–Cloud Computing Competence Centre, UBIMedical, University of Beira Interior, Estrada Municipal 506, 6200-284 Covilhã, Portugal;

⁸  Department of Clinical Analysis, School of Pharmaceutical Sciences, São Paulo State University (UNESP), Campus Ville, Araraquara, 14800-903 São Paulo, Brazil;

Abstract:

Cervical cancer is the fourth leading cause of death in women worldwide, with 99% of cases associated with a human papillomavirus (HPV) infection. Given that HPV prophylactic vaccines do not exert a therapeutic effect in individuals previously infected, have low coverage of all HPV types, and have poor accessibility in developing countries, it is unlikely that HPV-associated cancers will be eradicated in the coming years. Therefore, there is an emerging need for the development of anti-HPV drugs. Considering HPV E6’s oncogenic role, this protein has been proposed as a relevant target for cancer treatment. In the present work, we employed in silico tools to discover potential E6 inhibitors, as well as biochemical and cellular assays to understand the action of selected compounds in HPV-positive cells (Caski and HeLa) vs. HPV-negative (C33A) and non-carcinogenic (NHEK) cell lines. In fact, by molecular docking and molecular dynamics simulations, we found three phenolic compounds able to dock in the E6AP binding pocket of the E6 protein. In particular, lucidin and taxifolin were able to inhibit E6-mediated p53 degradation, selectively reduce the viability, and induce apoptosis in HPV-positive cells. Altogether, our data can be relevant for discovering promising leads for the development of specific anti-HPV drugs.

Journal: Cancers

Link: https://www.mdpi.com/2072-6694/14/12/2834