Cancer susceptibility of beta HPV49 E6 and E7 transgenic mice to 4-nitroquinoline 1-oxide treatment correlates with mutational signatures of tobacco exposure

The E6 and E7 proteins of beta3 human papillomavirus 49 can deregulate both cellular and extracellular vesicles-carried microRNAs

BACKGROUND

The β3 human papillomavirus (HPV)49 induces immortalization of primary keratinocytes through the action of E6 and E7 oncoproteins with an efficiency similar to alpha high risk (HR)-HPV16. Since HR-HPV oncoproteins are known to alter microRNA (miRNA) expression and extracellular vesicle (EV) production, we investigated the impact of HPV49 E6 and E7 proteins on miRNA profile and EV expression, and their involvement in the control of cell proliferation.

METHODS

The miRNA expression was evaluated by a miRNA array and validated by RT-qPCR in primary human keratinocytes immortalized by β3 HPV49 (K49) or α9 HR-HPV16 (K16), and in EVs from K49 and K16. The modulation of miRNA target proteins was investigated by immunoblotting analyses.

RESULTS

By comparing miRNA expression in K49 and K16 and the derived EVs, six miRNAs involved in HPV tumorigenesis were selected and validated. MiR-19a and -99a were found to be upregulated and miR-34a downregulated in both cell lines; miR-17 and -590-5p were upregulated in K49 and downmodulated in K16; miR-21 was downregulated only in K16. As for EV-carried miRNAs, the expression of miR-17, -19a, -21 and -99a was decreased and miR-34a was increased in K49 EVs. In K16 EVs, we revealed the same modulation of miR-19a, -34a, and -99a observed in producing cells, while miR-21 was upregulated. Cyclin D1, a common target of the selected miRNAs, was downmodulated in both cell lines, whereas cyclin-dependent kinase 4 was down-modulated in K49 but upregulated in K16.

CONCLUSION

These data suggest that E6 and E7 proteins of β3 HPV49 and α9 HR-HPV16 affect key factors of cell cycle control by indirect mechanisms based on miRNA modulation.

Beta HPV Deregulates Double-Strand Break Repair

Beta human papillomavirus (beta HPV) infections are common in adults. Certain types of beta HPVs are associated with nonmelanoma skin cancer (NMSC) in immunocompromised individuals. However, whether beta HPV infections promote NMSC in the immunocompetent population is unclear. They have been hypothesized to increase genomic instability stemming from ultraviolet light exposure by disrupting DNA damage responses. Implicit in this hypothesis is that the virus encodes one or more proteins that impair DNA repair signaling. Fluorescence-based reporters, next-generation sequencing, and animal models have been used to test this primarily in cells expressing beta HPV E6/E7. Of the two, beta HPV E6 appears to have the greatest ability to increase UV mutagenesis, by attenuating two major double-strand break (DSB) repair pathways, homologous recombination, and non-homologous end-joining. Here, we review this dysregulation of DSB repair and emerging approaches that can be used to further these efforts.

High-risk human papillomavirus in patients with oral leukoplakia and oral squamous cell carcinoma-A multi-centre study in Sweden, Brazil and Romania

OBJECTIVES

Although causal associations between oral leukoplakia (OL), oral squamous cell carcinoma (OSCC) and high-risk human papillomavirus (HR-HPV) have been speculated upon in several reports, conclusive evidence has not been presented. This study investigates whether the number of cases of HR-HPV in OL has increased over time and whether the prevalence of HR-HPV-positive OL differs in various parts of the world.

PATIENTS AND METHODS

A total of 432 patients with OL from Sweden, Brazil and Romania were analysed. Patients were divided into historical (1992-2002) and contemporary (2011-2017) cohorts from the respective countries. Seventeen patients with OL developed oral squamous cell carcinoma (OSCC). A real-time PCR assay, targeting HPV sub-types 6,11,16,18,31,33,35,39,45,52,56,58 and 59, was performed to detect HR-HPV in patients with OL.

RESULTS

In the Swedish and Romanian cohorts, none of the investigated HPV sub-types were detected. In the Brazilian cohorts, five patients with OL (3%) were positive for HR-HPV, including four patients from the contemporary cohort (HPV 16, 31, 33) and one from the historical cohort (HPV 11). All the cases of OL that transformed into OSCC were HR-HPV-negative, as were the corresponding tumours.

CONCLUSIONS

In summary, the prevalence of HR-HPV in OL is low in all the tested countries, and the incidence has not changed over time. HR-HPV in OL does not seem to be a driver of oncogenesis.

Transforming Properties of Beta-3 Human Papillomavirus E6 and E7 Proteins

The beta human papillomaviruses (HPVs) are subdivided into 5 species (beta-1 to beta-5), and they were first identified in the skin. However, the beta-3 species appears to be more highly represented in the mucosal epithelia than in the skin. Functional studies have also highlighted that beta-3 HPV49 shares some functional similarities with mucosal high-risk (HR) HPV16. Here, we describe the characterization of the in vitro transforming properties of the entire beta-3 species, which includes three additional HPV types: HPV75, HPV76, and HPV115. HPV49, HPV75, and HPV76 E6 and E7 (E6/E7), but not HPV115 E6 and E7, efficiently inactivate the p53 and pRb pathways and immortalize or extend the life span of human foreskin keratinocytes (HFKs). As observed for HR HPV16, cell cycle deregulation mediated by beta-3 HPV E6/E7 expression leads to p16INK4a accumulation, whereas no p16INK4a was detected in beta-2 HPV38 E6/E7 HFKs. As shown for HPV49 E6, HPV75 and HPV76 E6s degrade p53 by an E6AP/proteasome-mediated mechanism. Comparative analysis of cellular gene expression patterns of HFKs containing E6 and E7 from HR HPV16, beta-3 HPV types, and beta-2 HPV38 further highlights the functional similarities of HR HPV16 and beta-3 HPV49, HPV75, and HPV76. The expression profiles of these four HPV HFKs show some similarities and diverge substantially from those of beta-3 HPV115 E6/E7 and beta-2 HPV38 E6/E7 HFKs. In summary, our data show that beta-3 HPV types share some mechanisms with HR HPV types and pave the way for additional studies aiming to evaluate their potential role in human pathologies.IMPORTANCE Human papillomaviruses are currently classified in different genera. Mucosal HPVs belonging to the alpha genus have been clearly associated with carcinogenesis of the mucosal epithelium at different sites. Beta HPV types have been classified as cutaneous. Although findings indicate that some beta HPVs from species 1 and 2 play a role, together with UV irradiation, in skin cancer, very little is known about the transforming properties of most of the beta HPVs. This report shows the transforming activity of E6 and E7 from beta-3 HPV types. Moreover, it highlights that beta-3 HPVs share some biological properties more extensively with mucosal high-risk HPV16 than with beta-2 HPV38. This report provides new paradigms for a better understanding of the biology of the different HPV types and their possible association with lesions at mucosal and/or cutaneous epithelia.

Human Papillomavirus and carcinogenesis: Novel mechanisms of cell communication involving extracellular vesicles

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A group of mucosal HPVs are the causative agents of cervical cancer and are associated to other cancers.

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Certain cutaneous HPVs are involved in the development of cutaneous squamous cell carcinoma.

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EVs released by HPV⁺ cells convey a specific cargo of mRNAs and microRNAs.

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The EV delivery from HPV⁺ cells to non-infected recipient cells may represent a novel mechanism of tumorigenesis promotion.

A small group of mucosal Human Papillomaviruses are the causative agents of cervical cancer and are also associated with other types of cancers. Certain cutaneous Human Papillomaviruses seem to have a role as co-factors in the UV-induced carcinogenesis of the skin. The main mechanism of the tumorigenesis induced by Human Papillomaviruses is linked to the transforming activity of the viral E6 and E7 oncoproteins. However, other mechanisms, such as the gene expression control by specific microRNAs expression and deregulation of immune inflammatory mediators, may be important in the process of transformation. In this context, the release of Extracellular Vesicles with a specific cargo (microRNAs involved in tumorigenesis, mRNAs of viral oncoproteins, cytokines, chemokines) appears to play a key role.