E6/E7 oncogenes in epithelial suprabasal layers and estradiol promote cervical growth and ear regeneration

The loss of antioxidant activities impairs intestinal epithelium homeostasis by altering lipid metabolism

Reactive oxygens species (ROS) are common byproducts of metabolic reactions and could be at the origin of many diseases of the elderly. Here we investigated the role of ROS in the renewal of the intestinal epithelium in mice lacking catalase (CAT) and/or nicotinamide nucleotide transhydrogenase (NNT) activities. Cat-/- mice have delayed intestinal epithelium renewal and were prone to develop necrotizing enterocolitis upon starvation. Interestingly, crypts lacking CAT showed fewer intestinal stem cells (ISC) and lower stem cell activity than wild-type. In contrast, crypts lacking NNT showed a similar number of ISCs as wild-type but increased stem cell activity, which was also impaired by the loss of CAT. No alteration in the number of Paneth cells (PCs) was observed in crypts of either Cat-/- or Nnt-/- mice, but they showed an evident decline in the amount of lysozyme. Cat deficiency caused fat accumulation in crypts, and a fall in the remarkable high amount of adipose triglyceride lipase (ATGL) in PCs. Notably, the low levels of ATGL in the intestine of Cat -/- mice increased after a treatment with the antioxidant N-acetyl-L-cysteine. Supporting a role of ATGL in the regulation of ISC activity, its inhibition halt intestinal organoid development. These data suggest that the reduction in the renewal capacity of intestine originates from fatty acid metabolic alterations caused by peroxisomal ROS.

DNA viruses and cancer: insights from evolutionary biology

When it comes to understanding the exact mechanisms behind the virus induced cancers, we have often turned to molecular biology. It would be fair to argue that our understanding of cancers caused by viruses has significantly improved since the isolation of Epstein-Barr virus from Burkitt's lymphoma. However they are some important questions that remain unexplored like what advantage do viruses derive by inducing carcinogenesis? Why do viruses code for the so called oncogenes? Why DNA viruses are disproportionately linked to cancers? These questions have been addressed from the lens of evolutionary biology in this review. The evolutionary analysis of virus induced cancer suggests that persistent strategy of infection could be a stable strategy for DNA viruses and also the main culprit behind their tendency to cause cancer. The framework presented in the review not only explains wider observations about cancer caused by viruses but also offers fresh predictions to test the hypothesis.

Human Papillomavirus 11 Early Protein E6 Activates Autophagy by Repressing AKT/mTOR and Erk/mTOR

Low-risk human papillomaviruses (LR-HPVs) are the causative agents of genital warts, which are a widespread sexually transmitted disease. How LR-HPVs affect autophagy and the specific proteins involved are unknown. In the current study, we investigated the impact of LR-HPV11 early protein 6 (E6) on the activity of the autophagy pathway. We transfected an HPV11 E6 (11E6) plasmid into HaCaT cells, H8 cells, and NHEK cells and established a stable cell line expressing the HPV11 E6 protein. The differences in autophagy activity and upstream regulatory pathways compared with those in the parent cell lines were investigated using a Western blot analysis of the total and phosphorylated protein levels and confocal microscopy of immunostained cells and cells transfected with an mCherry-green fluorescent protein-LC3 expression plasmid. We used short hairpin RNA (shRNA) to knock down 11E6 and showed that these effects require continued 11E6 expression. Compared with its expression in the control cells, the expression of HPV11 E6 in the cells activated the autophagy pathway. The increased autophagy activity was the result of the decreased phosphorylation levels of the canonical autophagy repressor mammalian target of rapamycin (mTOR) at its Ser2448 position (the mTOR complex 1 [mTORC1] phosphorylation site) and decreased AKT and Erk phosphorylation. Therefore, these results indicate that HPV11 E6 activates autophagy through the AKT/mTOR and Erk/mTOR pathways. Our findings provide novel insight into the relationship between LR-HPV infections and autophagy and could help elucidate the pathogenic mechanisms of LR-HPV.IMPORTANCE We transfected an HPV11 E6 plasmid into HaCaT cells, H8 cells, and NHEK cells and established a stable cell line expressing the HPV11 E6 protein. Then, we confirmed that HPV11 E6 induces autophagy by suppressing the AKT/mTOR and Erk/mTOR pathways. In contrast to the high-risk HPV E6 genes, HPV11 E6 did not affect the expression of p53. To the best of our knowledge, this study represents the first direct in-depth investigation of the relationship between the LR-HPV E6 gene and autophagy, which may help to reveal the pathogenesis of LR-HPV infection.

The E6/E7 oncogenes of human papilloma virus and estradiol regulate hedgehog signaling activity in a murine model of cervical cancer

Human papilloma virus oncogenes and estradiol are major etiologic factors associated with cervical cancer. In order to understand the mechanism by which these two factors promote carcinogenesis, the role of the Hedgehog (Hh) signaling pathway was evaluated during the normal growth of cervical epithelium and in the presence of E6/E7 oncogenes and exogenous estradiol. Hh signaling activity was determined in live animals (i.e., Gli-Luc reporter levels) during the estrous cycle and was found to be higher in the cervical area during the major growth phases, proestrus-estrus, in comparison to the diestrus phase. The same pattern was observed in transgenic mice expressing the E6/E7 oncogenes, though with notably higher levels than in control mice. Adding estradiol also markedly increased Gli activity in the cervix and the skin. In agreement with the correlation between high bioluminescence and tissue growth in different context, cervical cell proliferation was reduced upon Hh signaling inhibition in mice. Treatment with itraconazole, a putative novel Hh inhibitor, at an early stage of cervical carcinogenesis, did not decrease Hh signaling but it did reduce growth. Therefore, Hh signaling likely contributes to cervical carcinogenesis and itraconazole is effective to reduce growth but by a mechanism involving additional signaling pathways.