Role and predictive strength of transglutaminase type 2 expression in premalignant lesions of the cervix

Human papillomavirus oncoproteins and post-translational modifications: generating multifunctional hubs for overriding cellular homeostasis

Human papillomaviruses (HPVs) are major human carcinogens, causing around 5% of all human cancers, with cervical cancer being the most important. These tumors are all driven by the two HPV oncoproteins E6 and E7. Whilst their mechanisms of action are becoming increasingly clear through their abilities to target essential cellular tumor suppressor and growth control pathways, the roles that post-translational modifications (PTMs) of E6 and E7 play in the regulation of these activities remain unclear. Here, we discuss the direct consequences of some of the most common PTMs of E6 and E7, and how this impacts upon the multi-functionality of these viral proteins, and thereby contribute to the viral life cycle and to the induction of malignancy. Furthermore, it is becoming increasingly clear that these modifications, may, in some cases, offer novel routes for therapeutic intervention in HPV-induced disease.

Characterization of distinct sub-cellular location of transglutaminase type II: changes in intracellular distribution in physiological and pathological states

Transglutaminase type II (TG2) is a pleiotropic enzyme that exhibits various activities unrelated to its originally identified functions. Apart from post-translational modifications of proteins (peculiar to the transglutaminase family enzymes), TG2 is involved in diverse biological functions, including cell death, signaling, cytoskeleton rearrangements, displaying enzymatic activities, G-protein and non-enzymatic biological functions. It is involved in a variety of human diseases such as celiac disease, diabetes, neurodegenerative diseases, inflammatory disorders and cancer. Regulatory mechanisms might exist through which cells control multifunctional protein expression as a function of their sub-cellular localization. The definition of the tissue and cellular distribution of such proteins is important for the determination of their function(s). We investigate the sub-cellular localization of TG2 by confocal and immunoelectron microscopy techniques in order to gain an understanding of its properties. The culture conditions of human sarcoma cells (2fTGH cells), human embryonic kidney cells (HEK293^TG) and human neuroblastoma cells (SK-n-BE(2)) are modulated to induce various stimuli. Human tissue samples of myocardium and gut mucosa (diseased and healthy) are also analyzed. Immuno-gold labeling indicates that TG2 is localized in the nucleus, mitochondria and endoplasmic reticulum under physiological conditions but that this is not a stable association, since different locations or different amounts of TG2 can be observed depending on stress stimuli or the state of activity of the cell. We describe a possible unrecognized location of TG2. Our findings thus provide useful insights regarding the functions and regulation of this pleiotropic enzyme.

Synergistic effect of viral load and alcohol consumption on the risk of persistent high-risk human papillomavirus infection

PURPOSE

This prospective study aimed to examine the combined effect of viral load and alcohol consumption on the risk of persistent high-risk (HR) human papillomavirus (HPV) infection.

METHODS

Among women undergoing health screening between 2002 and 2011 at the National Cancer Center, 284 and 122 women with HR-HPV infection and cytological findings of low-grade squamous intraepithelial or lower-grade lesions were followed up for 1 and 2 years, respectively. Multivariate logistic regression analysis was performed, and the relative excess risk due to interaction (RERI) and synergy index (S) were calculated.

RESULTS

Among drinkers, the risks of 1-year (odds ratio [OR] 4.09, 95% confidence interval [CI] 2.05-8.18) and 2-year persistence (OR 8.08, CI 2.36-27.6) were significantly higher for high HPV loads than for low HPV loads; this association was not seen for non-drinkers. The risks for 1-year (OR 4.14, CI 1.89-9.05) and 2-year persistence (OR 6.61, CI 2.09-20.9) were significantly higher in subjects with a high HPV load who were also drinkers than in those who were non-drinkers. A high HPV load together with a longer drinking duration or higher alcohol consumption was associated with increased risks of 1-year (OR 3.07, CI 1.40-6.75 or OR 2.05, CI 0.87-4.83) and 2-year persistence (OR 6.40, CI 1.72-23.8 or OR 4.14, CI 1.18-14.6). The synergistic effect of alcohol consumption and HR-HPV load was stronger on the risk of 2-year persistence (RERI = 3.26, S = 2.38) than on the risk of 1-year persistence (RERI = 1.21, S = 1.63).

CONCLUSIONS

The synergistic effect of HR-HPV load and alcohol consumption was associated with the risk of HR-HPV persistence and was stronger for longer-term HR-HPV infection. Limiting alcohol consumption might be an important measure to prevent the development of cervical cancer in women with a high HR-HPV load.

Oxidative stress and HPV carcinogenesis

Extensive experimental work has conclusively demonstrated that infection with certain types of human papillomaviruses, the so-called high-risk human papillomavirus (HR-HPV), represent a most powerful human carcinogen. However, neoplastic growth is a rare and inappropriate outcome in the natural history of HPV, and a number of other events have to concur in order to induce the viral infection into the (very rare) neoplastic transformation. From this perspective, a number of putative viral, host, and environmental co-factors have been proposed as potential candidates. Among them oxidative stress (OS) is an interesting candidate, yet comparatively underexplored. OS is a constant threat to aerobic organisms being generated during mitochondrial oxidative phosphorylation, as well as during inflammation, infections, ionizing irradiation, UV exposure, mechanical and chemical stresses. Epithelial tissues, the elective target for HPV infection, are heavily exposed to all named sources of OS. Two different types of cooperative mechanisms are presumed to occur between OS and HPV: I) The OS genotoxic activity and the HPV-induced genomic instability concur independently to the generation of the molecular damage necessary for the emergence of neoplastic clones. This first mode is merely a particular form of co-carcinogenesis; and II) OS specifically interacts with one or more molecular stages of neoplastic initiation and/or progression induced by the HPV infection. This manuscript was designed to summarize available data on this latter hypothesis. Experimental data and indirect evidences on promoting the activity of OS in viral infection and viral integration will be reviewed. The anti-apoptotic and pro-angiogenetic role of NO (nitric oxide) and iNOS (inducible nitric oxide synthase) will be discussed together with the OS/HPV cooperation in inducing cancer metabolism adaptation. Unexplored/underexplored aspects of the OS interplay with the HPV-driven carcinogenesis will be highlighted. The aim of this paper is to stimulate new areas of study and innovative approaches.