Primary Cultures Derived From Bovine Papillomavirus-Infected Lesions As Model To Study Metabolic Deregulation

Abstract

Bovine papillomavirus (BPV) is the etiological agent of bovine papillomatosis, disease characterized by the presence of multiple papillomas that can regress or to progress to malignances. Due to the pathological similarities with the human papillomavirus (HPV), BPV is considered a prototype to study the papillomavirus-associated oncogenic process. Although it is clear that both BPV and HPV can interact with host chromatin, the interaction of these viruses with cell metabolism remains understudied due to the little attention given to primary cultures derived from papillomavirus-infected lesions. Thus, this study analyzed the energy metabolism, including the mitochondrial membrane potential (ΔΨm) and Reactive Oxygen Species (ROS) of cells derived from cutaneous papilloma, fibropapilloma and Esophageal Carcinoma (EC) as model to evaluate the cell metabolism. These cells were cultivated until sixth passage and subjected to BPV DNA sequences identification by PCR using specific primers to BPV-1, 2 and 4. PCR results showed the presence and maintenance of at least one BPV type along the six passages analyzed. Cells derived from normal skin, without BPV DNA sequences were used as control. Results of energy metabolism showed the loss of ΔΨm in fibropapilloma and EC cells, suggesting a metabolic switch compatible to the activation of aerobic glycolysis. Cutaneous papilloma and normal skin cells showed the maintenance of ΔΨm. Paradoxically, cutaneous papilloma and fibropapilloma presented high levels of ROS production, while the EC cells reduced the ROS levels, reinforcing the activation of glycolytic metabolism. Our results suggest that the metabolic switch is mediated by BPV E6 oncoprotein, since the addition of this oncoprotein in normal cells promoted the oxidative stress. The oxidative stress showed able to activate the STAT3 nuclear factor in papilloma and fibropapilloma cells, contributing to metabolic deregulation. These data suggest that primary cultures are useful model to study the interaction between BPV and cell metabolism.

The human papillomavirus (HPV)-related cancer biology: An overview

“…In this sense, studies have been shown that the HPV-16 E6* oncoprotein has a pro-oxidant action [74,210]. Similar results were described in study involving the BPV-1 E6 oncoprotein [76]. Moreover, both BPV E6 [88] and HPV E6/E7 oncoprotein can lead to cytogenic damages [114,115], resulting in genomic instability, which can result in the CSC development.…”

“…The authors also showed that HPV-16 E6 promotes the STAT3 activation [259]. The STAT3 activation was also described in cell line derived from bovine esophageal carcinoma co-infected by BPV-1, 2 and 4, suggesting that the STAT3 phosphorilation is a consequence of oxidative stress induced by E6 oncoprotein [76]. Interestling, Araldi et al [182] verified that BPV-infected cells from bovine fibropapilloma and esophageal carcinoma exhibit morphological alterations, including the loss of cell polarity, and increase the expression levels of Oct-3/4, suggesting that the EMT onset in pre-neoplastic lesions (fibropapillomas).…”

“…Currently studies have shown that the both HPV [74] and bovine papillomavirus type 1 (BPV-1) E6 oncoprotein is related to energetic metabolism deregulation [75,76]. Considering the relevance of these alterations for the carcinogenesis, the E6-related metabolic deregulations will be discussed in the Section 3.4.…”

“…In this sense, studies have been shown that HPV E6 and E6* (a splicing isoform of HPV-16 E6) [74,210,211] and BPV-1 E6 oncoproteins increase the ROS production [76] through the downregulation of SOD2 and GPx anti-oxidant enzymes [212]. The chronical oxidative stress promoted by E6 oncoprotein can lead to nucleotide oxidation and, therefore, genetic damages, including DSBs [213], which are commonly observed in cells infected by HPV [109] or BPV [76,[214][215][216]. However, the repair of oxidize nucleotides by base excision can result in SSBs [217].…”