Project description:Background: LINE-1 elements make up the most abundant retrotransposon family in the human genome. Full-length LINE-1 elements encode their own reverse transcriptase (RT). They are expressed at low levels in normal cells and abundantly in cancer cells. RT down-regulation, by either RNA interference to LINE-1 elements, or by RT inhibitory drugs, was previously found to reduce proliferation and promote differentiation in cancer cells and to antagonize tumor growth in animal models. Results: We report that the RT inhibitor efavirenz effectively inhibit proliferation of a variety of human tumorigenic cell lines while only slightly affecting the proliferation of human normal fibroblast cell line, a difference that nicely matches RT expression in the former cell lines and its lack in the latter. The finding of Alu and LINE-1 containing DNA:RNA hybrid molecules - identified by CsCl density gradients - selectively in cancer but not in normal cells, suggests that RNA transcripts from these retroelements are candidate substrates for reverse transcription. These hybrids disappear in tumor cells treated with efavirenz, under the same conditions which induce an extensive reprogrammed expression profiles for protein-coding genes, microRNAs (miRNAs) and ultraconserved regions (UCRs). The RT-sensitive miRNAs and UCRs are significantly associated with Alus sequences. Conclusions: A novel RT-dependent mechanism governs the balance between single-stranded and double-stranded RNA production. In cancer cells, the abundant LINE-1-encoded RT reverse-transcribes retroelement-derived mRNAs, generating RNA:DNA hybrids. We propose that this impairs the formation of double-stranded RNAs and the ensuing production of small regulatory RNAs, with a direct impact on gene expression. RT inhibition restores the M-^QnormalM-^R small RNA profile and the regulatory networks that depend on them. Thus, the retrotransposon-encoded RT drives an epigenetic mechanism crucial to maintenance of the transformed state in tumor cells.

Project description:Rifampicin and efavirenz are commonly used medicines to treat tuberculosis (rifampicin) and HIV/AIDS (efavirenz). Rifampicin and efavirenz are metabolized in the liver and exposure to these medicines can alter microRNA expression in hepatocytes. Changes in microRNA expression may affect metabolism of these medicines and potentially influence how patient's respond to therapy. It is important to understand changes in microRNA expression in a hepatic cell-based model. Differentiated HepaRG cells were used because mRNA expression and induction of drug metabolizing enzymes are comparable to that of primary human hepatocytes yet differentiated HepaRG cells have an extended lifespan. Differentiated HepaRG cells were obtained from Merck Millipore and cultured as an adherent cell line at a density of 315000 cells/well using collagen I coated 24-well plates. Clinically relevant concentrations of rifampicin and efavirenz were selected as 6.4uM efavirenz (dissolved in 100% dimethyl sulfoxide) and 24.4uM rifampicin (dissolved in 100% dimethyl sulfoxide), while 0.02% dimethyl sulfoxide was used as control to minimize toxicity. HepaRG serum-free induction medium was used to dilute efavirenz and rifampicin. On day 7 since thawing differentiated HepaRG cells, these cells were treated with 6.4uM efavirenz or 24.4uM rifampicin or 0.02% dimethyl sulfoxide for a period of 24 hours. Three biological replicates were available for each treatment condition. Total RNA was isolated from the cells, after treatment, using the Quick-RNATM MiniPrep Kit from Zymo Research Corporation. MicroRNA expression profiling was performed using the TaqMan® OpenArray® Human MicroRNA Panel and QuantStudioTM 12K Flex system. The R/Bioconductor package “Automated Analysis of High-Throughput qPCR Data” were used for data analyses. CT values were used for differential expression analysis and microRNAs with a CT value > 35 was considered undetected. MicroRNAs undetected in any of the replicate samples or microRNAs with AmpScore < 1.24 or CqConf < 0.8 were excluded. Quantile normalization was followed by limma analyses to identify differentially expressed microRNAs for efavirenz versus dimethyl sulfoxide and rifampicin versus dimethyl sulfoxide.

Project description:Although high-risk human papillomavirus (HPV) infection plays a major role in the development of cervical cancer, additive oncogenic events are involved as well. One key event involves increased activity of telomerase resulting from a deregulated expression of its catalytic subunit hTERT. Our previous microcell-mediated chromosome transfer studies revealed that introduction of human chromosome 6 in the HPV16 immortalized keratinocyte cell line FK16A and in the HPV16 containing cervical cancer cell line SiHa induced growth arrest, resulting from a repression of hTERT mRNA expression and telomerase activity. Here, this model was used to analyze expression profiles associated with hTERT deregulation in HPV transformed cells. Microarray expression analysis of 12 FK16A/chromosome 6 hybrids, four of which were negative for endogenous hTERT and 8 of which were positive for endogenous hTERT, resulted in the identification of 164 differentially expressed genes. Differential expression of a selection of 5 genes was verified by real-time RT-PCR. Of these 164 genes, 32 were also differentially expressed in other HPV transformed cells with deregulated hTERT. For 2 of these genes, encoding AQP3 and MGP, altered expression in hTERT positive cervical carcinomas was confirmed by real-time RT-PCR and immunohistochemistry, respectively. In summary we identified 32 candidate biomarkers for deregulated hTERT mRNA expression which may enable the identification of cervical premalignant lesions that are at highest risk to progress to invasive cancer. Keywords: microarray expression analysis, hTERT, cervical cancer 12 previously established cell hybrids, all carrying the same genetic background were subjected to microarray expression analysis. These hybrids were generated by the introduction of chromosome 6 in the HPV16 immortalized cell line FK16A, which resulted in a suppression of hTERT expression and telomerase activity. 8 hybrids were endogenous hTERT positive and 8 hybrids were hTERT negative. Additionally primary keratinocytes (hTERT negative), parental cell line FK16A and cervical cancer cell line SiHa (both hTERT positive) were hybridized.

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EFV-UCR

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