Human papillomavirus type 18 E5 oncoprotein cooperates with E6 and E7 in promoting cell viability and invasion and in modulating the cellular redox state

BACKGROUND High-risk human papillomaviruses (HR-HPVs) are the etiological agents of cervical cancer. Among them, types 16 and 18 are the most prevalent worldwide. The HPV genome encodes three oncoproteins (E5, E6, and E7) that possess a high transformation potential in culture cells when transduced simultaneously. In the present study, we analysed how these oncoproteins cooperate to boost key cancer cell features such as uncontrolled cell proliferation, invasion potential, and cellular redox state imbalance. Oxidative stress is known to contribute to the carcinogenic process, as reactive oxygen species (ROS) constitute a potentially harmful by-product of many cellular reactions, and an efficient clearance mechanism is therefore required. Cells infected with HR-HPVs can adapt to oxidative stress conditions by upregulating the formation of endogenous antioxidants such as catalase, glutathione (GSH), and peroxiredoxin (PRX). OBJECTIVES The primary aim of this work was to study how these oncoproteins cooperate to promote the development of certain cancer cell features such as uncontrolled cell proliferation, invasion potential, and oxidative stress that are known to aid in the carcinogenic process. METHODS To perform this study, we generated three different HaCaT cell lines using retroviral transduction that stably expressed combinations of HPV-18 oncogenes that included HaCaT E5-18, HaCaT E6/E7-18, and HaCaT E5/E6/E7-18. FINDINGS Our results revealed a statistically significant increment in cell viability as measured by MTT assay, cell proliferation, and invasion assays in the cell line containing the three viral oncogenes. Additionally, we observed that cells expressing HPV-18 E5/E6/E7 exhibited a decrease in catalase activity and a significant augmentation of GSH and PRX1 levels relative to those of E5, E6/E7, and HaCaT cells. MAIN CONCLUSIONS This study demonstrates for the first time that HPV-18 E5, E6, and E7 oncoproteins can cooperate to enhance malignant transformation.

Cáncer cérvicouterino y virus del papiloma humano / Cervical cancer and human papillomavirus

El cáncer cérvicouterino (CaCu) es la segunda causa de muerte por cáncer en mujeres de todo el mundo, a pesar de la implementación de la citología de cérvix para su prevención. Esto se debe a la baja sensibilidad y especificidad de la prueba, lo cual apoya a un cambio urgente en la forma de tamizaje para su detección. Ahora se sabe que la infección persistente por virus del papiloma humano de alto riesgo (HR-HPV) es la causa de la totalidad de los casos de CaCu. En la actualidad se están utilizando vacunas frente a dos (Bivalente: HPV-16 y HPV-18) o cuatro (Tetravalente: HPV-6 HPV-11, HPV-16 y HPV-18) de las cepas de HR-HPV que causan la mayoría de los casos de CaCu. El propósito de este artículo es proporcionar una revisión de las características principales del virus y de los mecanismos que se echan a andar bajo la infección persistente de las células cervicales, lo cual conduce a la proliferación desordenada y a la malignización de las células infectadas. Es necesario que el virus se integre al genoma de la célula epitelial para que inicie la expresión de las oncoproteínas virales E6 y E7 lo cual conducirá al desarrollo del CaCu.

Cervical cancer (CC) is the second cause of death for cancer in women worldwide in spite of the implementation of cervix cytology screenings for its prevention. The low sensibility and specificity of the test reduce the potential benefits of these screenings and supports urgent improvements in early detection tests for CC. It is now known that persistent infection with the high-risk human papiloma virus (HR-HPV) is the causal agent of almost all cases of CC. HR-HPV vaccines effective against two (Bivalent: HPV-16 and HPV-18) or four (Tetravalent: HPV-6 HPV-11, HPV-16 and HPV-18) strains that are responsible of the majority of the CC cases have been licensed in several countries. The present study aims to provide a review of the principal characteristics of the HR-HPV virus and of the mechanisms that take to the persistent infection of the cervical cells leading to abnormal proliferation and malignancy. It is necessary that the virus integrates into the genome of the epithelial cell to initiates the expression of the E6 and E7 viral oncoproteins which will lead to the development of the CC.

Assessing protein stability of the dimeric DNA-binding domain of E2 human papillomavirus 18 with molecular dynamics

The objective of this study is to understand the structural flexibility and curvature of the E2 protein of human papillomavirus type 18 using molecular dynamics (6 ns). E2 is required for viral DNA replication and its disruption could be an anti-viral strategy. E2 is a dimer, with each monomer folding into a stable open-faced â-sandwich. We calculated the mobility of the E2 dimer and found that it was asymmetric. These different mobilities of E2 monomers suggest that drugs or vaccines could be targeted to the interface between the two monomers.

STP-A11, an oncoprotein of Herpesvirus saimiri augments both NF-kappaB and AP-1 transcription activity through TRAF6

Herpesvirus saimiri (HVS), a member of the gamma-herpesvirus family, encodes an oncoprotein called Saimiri Transforming Protein (STP) which is required for lymphoma induction in non-human primates. However, a detailed mechanism of STP-A11-induced oncogenesis has not been revealed yet. We first report that STP-A11 oncoprotein interacts with TNF-alpha receptor-associated factor (TRAF) 6 in vivo and in vitro. Mutagenesis analysis of the TRAF6-binding motif 10PQENDE15 in STP-A11 reveals that Glu (E)12 residue is critical for binding to TRAF6 and NF-kappaB activation. Interestingly, co-expression of E12A mutant, lack of TRAF6 binding, with cellular Src (Src) results in decreased transcriptional activity of Stat3 and AP-1, a novel target of STP-A11 compared to that of wild type. Furthermore, the presence of STP-A11 enhances the association of TRAF6 with Src and induces the translocation of both TRAF6 and Src to a nonionic detergent-insoluble fraction. Taken together, these studies suggest that STP-A11 oncoprotein up-regulates both NF-kappaB and AP-1 transcription activity through TRAF6, which would ultimately contribute cellular transformation.

Polimorfismo en el codón 72 del gen p53 y riesgo de cáncer cérvico-uterino en México / Polymorphism in codon 72 of the p53 gene and cervico-uterine cancer risk in Mexico

A polymorphism at codon 72 in the p53 gen has been reported as a potential risk factor to cervical cancer (CC) because human papillomavirus (HPV) is more effective at degrading p53 Arg-72 than p53 Pro-72, making individuals homozygous for p53 Arg-72 seven times more likely to develop HPV-associated CC. As In Mexico the CC is a health public problem, we designed this study to determinate whether the p53 codon 72 polymorphism represent a risk factor to CC in our population. A case-controls study was performed. DNA was obtained from paraffin-embedded cervical fixed tissue samples. Analysis of the p53 genotype at position 72 was performed by polymerase chain reaction using specific primers and Accll digestion. Among cases with CC the proportions of the p53 genotypes at codon 72 were 0.05 to proline homozygous, 0.5 to heterozygous, and 0.45 to arginine-homozygous. In controls the proportions were 0.08, 0.62, and 0.31. X2 test showed no significant difference In the proportions. We conclude than In our population, as other worldwide countries, the homozygous for arginine at codon 72 of the p53 gene is not a risk factor to cervical cancer.

Immunoexpression of mutant p53 and human papillomavirus related E6 oncoprotein in anal malignancies.

Immunohistochemical expression of mutant p53 protein and human papillomavirus (HPV) 16 and 18 related E6 oncoprotein was studied in 36 biopsy proved anal cancers. Mutant p53 was detected in 61.1% cases. HPV 16 and 18 E6 protein was expressed in 22.2% cases, all of which were squamous cell carcinomas. Coexpression of both mutant p53 and E6 protein was found in only 5 cases (13.8%). In HPV 16/18 positive anal tumors, the degradation of p53 is accelerated by viral E6 oncoprotein. In HPV negative tumors, however, other mutagenic factors probably play a role in carcinogenesis.