Small DNA tumor viruses and human cancer: Preclinical models of virus infection and disease.

Human tumor viruses cause various human cancers that account for at least 15% of the global cancer burden. Among the currently identified human tumor viruses, two are small DNA tumor viruses: human papillomaviruses (HPVs) and Merkel cell polyomavirus (MCPyV). The study of small DNA tumor viruses (adenoviruses, polyomaviruses, and papillomaviruses) has facilitated several significant biological discoveries and established some of the first animal models of virus-associated cancers. The development and use of preclinical in vivo models to study HPVs and MCPyV and their role in human cancer is the focus of this review. Important considerations in the design of animal models of small DNA tumor virus infection and disease, including host range, cell tropism, choice of virus isolates, and the ability to recapitulate human disease, are presented. The types of infection-based and transgenic model strategies that are used to study HPVs and MCPyV, including their strengths and limitations, are also discussed. An overview of the current models that exist to study HPV and MCPyV infection and neoplastic disease are highlighted. These comparative models provide valuable platforms to study various aspects of virus-associated human disease and will continue to expand knowledge of human tumor viruses and their relationship with their hosts.

The Merkel Cell Polyomavirus T Antigens Function as Tumor Promoters in Murine Skin.

Merkel cell polyomavirus (MCPyV) causes the majority of human Merkel cell carcinomas (MCC), a rare but highly aggressive form of skin cancer. We recently reported that constitutive expression of MCC tumor-derived MCPyV tumor (T) antigens in the skin of transgenic mice leads to hyperplasia, increased proliferation, and spontaneous epithelial tumor development. We sought to evaluate how the MCPyV T antigens contribute to tumor formation in vivo using a classical, multi-stage model for squamous cell carcinoma development. In this model, two chemical carcinogens, DMBA and TPA, contribute to two distinct phases of carcinogenesis-initiation and promotion, respectively-that are required for tumors to develop. By treating the MCPyV transgenic mice with each chemical carcinogen, we determined how the viral oncogenes contributed to carcinogenesis. We observed that the MCPyV T antigens synergized with the tumor initiator DMBA, but not with the tumor promoter TPA, cause tumors. Therefore, the MCPyV tumor antigens function primarily as tumor promoters, similar to that seen with human papillomavirus (HPV) oncoproteins. These studies provide insight into the role of MCPyV T antigen expression in tumor formation in vivo and contribute to our understanding of how MCPyV may function as a human DNA tumor virus.

Efficient Transformation of Primary Human Mesenchymal Stromal Cells by Adenovirus Early Region 1 Oncogenes.

Previous observations that human amniotic fluid cells (AFC) can be transformed by human adenovirus type 5 (HAdV-5) E1A/E1B oncogenes prompted us to identify the target cells in the AFC population that are susceptible to transformation. Our results demonstrate that one cell type corresponding to mesenchymal stem/stroma cells (hMSCs) can be reproducibly transformed by HAdV-5 E1A/E1B oncogenes as efficiently as primary rodent cultures. HAdV-5 E1-transformed hMSCs exhibit all properties commonly associated with a high grade of oncogenic transformation, including enhanced cell proliferation, anchorage-independent growth, increased growth rate, and high telomerase activity as well as numerical and structural chromosomal aberrations. These data confirm previous work showing that HAdV preferentially transforms cells of mesenchymal origin in rodents. More importantly, they demonstrate for the first time that human cells with stem cell characteristics can be completely transformed by HAdV oncogenes in tissue culture with high efficiency. Our findings strongly support the hypothesis that undifferentiated progenitor cells or cells with stem cell-like properties are highly susceptible targets for HAdV-mediated cell transformation and suggest that virus-associated tumors in humans may originate, at least in part, from infections of these cell types. We expect that primary hMSCs will replace the primary rodent cultures in HAdV viral transformation studies and are confident that these investigations will continue to uncover general principles of viral oncogenesis that can be extended to human DNA tumor viruses as well. IMPORTANCE: It is generally believed that transformation of primary human cells with HAdV-5 E1 oncogenes is very inefficient. However, a few cell lines have been successfully transformed with HAdV-5 E1A and E1B, indicating that there is a certain cell type which is susceptible to HAdV-mediated transformation. Interestingly, all those cell lines have been derived from human embryonic tissue, albeit the exact cell type is not known yet. We show for the first time the successful transformation of primary human mesenchymal stromal cells (hMSCs) by HAdV-5 E1A and E1B. Further, we show upon HAdV-5 E1A and E1B expression that these primary progenitor cells exhibit features of tumor cells and can no longer be differentiated into the adipogenic, chondrogenic, or osteogenic lineage. Hence, primary hMSCs represent a robust and novel model system to elucidate the underlying molecular mechanisms of adenovirus-mediated transformation of multipotent human progenitor cells.

Genotipificación, niveles de expresión y estado físico del virus del papiloma humano en pacientes colombianos con cáncer de células escamosas en la cavidad oral / Genotyping, levels of expression and physical status of human papilloma virus in oropharyngeal squamous cell carcinoma among Colombian patients

Introducción. Uno de los factores de riesgo del carcinoma de células escamosas en la cavidad oral es la infección por el virus del papiloma humano (HPV), cuyas prevalencias dependen de la región geográfica. Objetivo. Identificar los tipos del virus del papiloma humano más frecuentes en el cáncer de la cavidad bucal, sus niveles de expresión y el estado físico del genoma viral. Materiales y métodos. Se seleccionaron 46 pacientes que asistían a los servicios de cirugía de cabeza y cuello en Bogotá, Manizales y Bucaramanga. El examen histopatológico de las muestras incluidas en el estudio demostró la presencia de carcinoma de células escamosas en la cavidad oral en todas ellas. Se extrajo el ADN para genotipificar el virus y determinar el estado físico de su genoma, y el ARN para determinar los transcritos virales mediante reacción en cadena de la polimerasa en tiempo real. Resultados. La prevalencia del virus del papiloma humano en los tumores fue de 21,74% (n=10) y el tipo viral más frecuente fue el HPV-16 (nueve casos). La expresión viral del HPV-16 fue baja (una de 11 copias) y el estado físico predominante fue el mixto (ocho casos), con prevalencia de la disrupción en el sitio de unión de E1 y E2 (2525 a 3720 nucleótidos). Conclusión. En los pacientes con carcinoma de cavidad oral incluidos en este trabajo, la frecuencia del virus del papiloma humano fue relativamente baja (21,7 %) y el tipo viral más frecuente fue el HPV-16, el cual se encontró en forma mixta y con baja expresión de E7 , lo cual puede ser indicativo de un mal pronóstico para el paciente.

Introduction: One of the risk factors for squamous cell oropharyngeal carcinoma is infection with the human papilloma virus (HPV), with prevalences that vary depending on the geographical region. Objective: To identify the most frequent HPV viral types in oropharyngeal cancer, the levels of expression and the physical condition of the viral genome. Materials and methods: Forty-six patients were included in the study from among those attending head and neck surgical services in the cities of Bogotá, Manizales and Bucaramanga. In the histopathological report all study samples were characterized as oropharyngeal squamous cell carcinoma. DNA extraction was subsequently performed for HPV genotyping and to determine the physical state of the viral genome, as well as RNA to determine viral transcripts using real-time PCR. Results: HPV prevalence in tumors was 21.74% (n=10) and the most common viral type was HPV-16 (nine cases). Viral expression for HPV-16 was low (one of 11 copies) and the predominant physical state of the virus was mixed (eight cases), with disruption observed at the E1 - E2 binding site (2525 - 3720 nucleotides). Conclusion: The prevalence of HPV associated with oropharyngeal carcinoma among the Colombian study population was 21.7%, which is relatively low. The most frequent viral type was HPV-16, found in a mixed form and with low expression of E7 , possibly indicating a poor prognosis for these patients.

Genotyping, levels of expression and physical status of human papilloma virus in oropharyngeal squamous cell carcinoma among Colombian patients.

INTRODUCTION: One of the risk factors for squamous cell oropharyngeal carcinoma is infection with the human papilloma virus (HPV), with prevalences that vary depending on the geographical region.  OBJECTIVE: To identify the most frequent HPV viral types in oropharyngeal cancer, the levels of expression and the physical condition of the viral genome.  MATERIALS AND METHODS: Forty-six patients were included in the study from among those attending head and neck surgical services in the cities of Bogotá, Manizales and Bucaramanga. In the histopathological report all study samples were characterized as oropharyngeal squamous cell carcinoma. DNA extraction was subsequently performed for HPV genotyping and to determine the physical state of the viral genome, as well as RNA to determine viral transcripts using real-time PCR.  RESULTS: HPV prevalence in tumors was 21.74% (n=10) and the most common viral type was HPV-16 (nine cases). Viral expression for HPV-16 was low (one of 11 copies) and the predominant physical state of the virus was mixed (eight cases), with disruption observed at the E1 - E2 binding site (2525 - 3720 nucleotides).  CONCLUSION: The prevalence of HPV associated with oropharyngeal carcinoma among the Colombian study population was 21.7%, which is relatively low. The most frequent viral type was HPV-16, found in a mixed form and with low expression of E7, possibly indicating a poor prognosis for these patients.

microRNAs are biomarkers of oncogenic human papillomavirus infections.

Cellular and viral microRNAs (miRNAs) are the transcriptional products of RNA polymerase II and are regulated by transcriptional factors for their differential expression. The altered expression of miRNAs in many cancer types has been explored as a marker for possible diagnosis and therapy. We report in this study that oncogenic human papillomaviruses (HPVs) induce aberrant expression of many cellular miRNAs and that HPV18 infection produces no detectable viral miRNA. Thirteen abundant host miRNAs were specifically regulated by HPV16 and HPV18 in organotypic raft cultures of foreskin and vaginal keratinocytes as determined by miRNA array in combination with small RNA sequencing. The increase of miR-16, miR-25, miR-92a, and miR-378 and the decrease of miR-22, miR-27a, miR-29a, and miR-100 could be attributed to viral oncoprotein E6, E7, or both, all of which are known to target many cellular transcription factors. The examination of 158 cervical specimens, including 38 normal, 52 cervical intraepithelial neoplasia (CIN), and 68 cervical cancer (CC) tissues, for the expression of these eight miRNAs showed a remarkable increase of miR-25, miR-92a, and miR-378 with lesion progression but no obvious change of miR-22, miR-29a, and miR-100 among the HPV-infected tissues. Further analyses indicate that an expression ratio ≥1.5 of miR-25/92a group over miR-22/29a group could serve as a cutoff value to distinguish normal cervix from CIN and from CIN to CC.