Various validated systems for testing the components of HPV E1 helicase and viral DNA replication using transient transfection of E1 and E2 expression plasmids or using purified enzymes in vitro have been reported ( Liu et al., 1995, Kuo et al., 1994 and Fradet-Turcotte et al., 2010). Further research is also needed in understanding the effects of CDV on the productive replicative cycle of low-risks HPVs and the organotypic epithelial raft cultures appear to be the ideal system to perform these investigations as they reproduce epithelial differentiation in an ex vivo system. A fully productive 3-dimensional tissue culture system

for production of high yields of infectious HPV-18 virions NLG919 concentration was first described in 2009, with multiple published applications since then (Wang et al., 2009). This system appears to be also more appropriate to analyse drug-metabolism because nucleoside metabolism in cell monolayer cultures (especially with immortalized and transformed cells)

are considerably abnormal compared to 3-dimensional tissues, where most cells are quiescent. Moreover, uptake of small molecules is substantially altered in rapidly dividing monolayer cells that do not have cell–cell junctions. Nucleotide synthetic pathways have exquisitely coordinated balancing of de novo production of the ribonucleoside and the deoxyribonucleoside CH5424802 chemical structure triphosphates, and these regulatory responses are also heavily influenced by salvage of nucleosides from broken down RNA and DNA or from the general circulation. Exogenous agents such as inhibitors of these synthetic or salvage pathways (eg. hydroxyurea, methotrexate) or from nucleoside analogues (eg. 5-FU) can substantially alter this balancing network. Whether CDV or other ANP’s

have an impact on the normal distribution of ribo- and deoxyribo-nucleosides and their phosphorylated derivatives should be investigated. How CDV and other ANPs impact ribonucleoside diphosphate reductase, the main source ZD1839 cell line of deoxynucleotide synthesis in virally infected cells should be considered, as well as the consequences of cell growth in the presence of CDV with respect to ribosomal RNA transcription and processing. One of the major findings regarding CDV-antitumor activities points to the potential use of the drug in the therapy of non-viral induced tumors such as glioblastomas. Also, further research will be necessary to elucidate the effects of CDV in several signalling pathways compared to PME derivatives and other chemotherapeutics in order to highlight (dis)similarities and understand their mechanisms of action. We are grateful to the Geconcerteerde Onderzoeksacties (GOA), Krediet no. 10/014 and to the Program Financing (PF-10/08) of the KU Leuven for funding. “
“Integrase inhibitors (INIs) are an important addition to the HIV infection treatment armamentarium. Licensed in 2007, raltegravir (RAL, Merck Laboratories) is the first INI approved for clinical use (FDA, 2007).