MicroRNAs are f22-nucleotide sequences thought to interact with multiple mRNAs resulting in either translational repression or degradation. We previously reported that several microRNAs had variable expression in mammalian cell lines, and we examined one, miR-200c, in more detail. A combination of bioinformatics and quantitative reverse transcription-PCR was used to identify potential targets and revealed that the zinc finger transcription factor transcription factor 8 (TCF8; also termed ZEB1, DEF1, Nil-2-A) had inversely proportional expression levels to miR-200c. Knockout experiments using anti-microRNA oligonucleotides increased TCF8 levels but with nonspecific effects. Therefore, to investigate target predictions, we overexpressed miR-200c in select cells lines. Ordinarily, the expression level of miR-200c in nonsmall-cell lung cancer A549 cells is low in contrast to normal human bronchial epithelial cells. Stable overexpression of miR-200c in A549 cells results in a loss of TCF8, an increase in expression of its regulatory target, E-cadherin, and altered cell morphology. In MCF7 (estrogen receptor-positive breast cancer) cells, there is endogenous expression of miR-200c and E-cadherin but TCF8 is absent. Conversely, MDA-MB-231 (estrogen receptor-negative) cells lack detectable miR-200c and E-cadherin (the latter reportedly due to promoter region methylation) but express TCF8. The ectopic expression of miR-200c in this cell line also reduced levels of TCF8, restored E-cadherin expression, and altered cell morphology. Because the down-regulation of E-cadherin is a crucial event in epithelial-to-mesenchymal transition, loss of miR-200c expression could play a significant role in the initiation of an invasive phenotype, and, equally, miR-200c overexpression holds potential for its reversal. [Cancer Res 2007;67(17):7972-6]

Almost all lung cancer deaths are caused by cigarette smoking, underscoring the need for ongoing efforts at tobacco control throughout the world. Further research is needed into the reasons underlying lung cancer disparities, the causes of lung cancer in never smokers, the potential role of HIV in lung carcinogenesis, and the development of biomarkers.

A 2-dimensional linear quadrupole ion trap mass spectrometer (LIT/MS) was employed to simultaneously screen for DNA adducts of environmental, dietary, and endogenous genotoxicants, by data-dependent constant neutral loss scanning followed by triple-stage mass spectrometry (CNL-MS 3 ). The loss of the deoxyribose (dR) from the protonated DNA adducts ([M+H-116] + ) in the MS/ MS scan mode triggered the acquisition of MS 3 product ion spectra of the aglycone adducts [BH 2 + ]. Five DNA adducts of the tobacco carcinogen 4-aminobiphenyl (4-ABP) were detected in human hepatocytes treated with 4-ABP, and three DNA adducts of the cooked-meat carcinogen 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) were identified in the livers of rats exposed to MeIQx, by the CNL-MS 3 scan mode. Buccal-cell DNA from tobacco smokers was screened for DNA adducts of various classes of carcinogens in tobacco smoke including 4-ABP, 2-amino-9H-pyrido [2,3-b]indole (AαC), and benzo[a]pyrene (BaP); the cooked-meat carcinogens MeIQx, AαC, and 2-amino-1-methyl-6-phenylmidazo[4,5-b]pyridine (PhIP); and the lipid peroxidation products acrolein (AC) and trans-4-hydroxynonenal (HNE). The CNL-MS 3 scanning technique can be used to simultaneously screen for multiple DNA adducts derived from different classes of carcinogens, at levels of adduct modification approaching 1 adduct per 10 8 unmodified DNA bases, when 10 μg of DNA are employed for the assay.

No abstract

DNA adducts of carcinogens derived from tobacco smoke and cooked meat were identified, by liquid chromatography-electrospray ionization/multi-stage tandem mass spectrometry (LC-ESI/ MS/MS n ), in saliva samples from 37 human volunteers on unrestricted diets. The N-(deoxyguanosin-8-yl) (dG-C8) adducts of the heterocyclic aromatic amines 2-amino-1-methyl-6-phenylimidazo [4,5-b] (MeIQx); and the aromatic amine, 4-aminobiphenyl (4-ABP) were characterized and quantified, by LC-ESI/MS/MS n , employing consecutive reaction monitoring at the MS 3 scan stage mode with a linear quadrupole ion trap (LIT) mass spectrometer (MS). DNA adducts of PhIP were found most frequently: dG-C8-PhIP was detected in saliva samples from 13 of 29 ever-smokers and in saliva samples from 2 of 8 never-smokers. dG-C8-AαC and dG-C8-MeIQx were identified solely in saliva samples of 3 current smokers, and dG-C8-4-ABP was detected in saliva from 2 current-smokers. The levels of these different adducts ranged from 1 to 9 adducts per 10 8 DNA bases. These findings demonstrate that PhIP is a significant DNA-damaging agent in humans. Saliva appears to be a promising biological fluid in which to assay DNA adducts of tobacco and dietary carcinogens, by selective LIT MS techniques.

Exfoliated cytologic specimens from mouth (buccal) epithelium may contain viable cells, permitting assay of gene expression for direct and noninvasive measurement of gene-environment interactions, such as for inhalation (e.g., tobacco smoke) exposures. We determined specific mRNA levels in exfoliated buccal cells collected by cytologic brush, using a recently developed RNA-specific real-time quantitative reverse transcription-PCR strategy. In a pilot study, metabolic activity of exfoliated buccal cells was verified by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium assay in vitro. Transcriptional activity was observed, after timed in vivo exposure to mainstream tobacco smoke resulted in induction of CYP1B1 in serially collected buccal samples from the one subject examined. For a set of 11 subjects, mRNA expression of nine genes encoding carcinogenand oxidant-metabolizing enzymes qualitatively detected in buccal cells was then shown to correlate with that in laser-microdissected lung from the same individuals ( 2 ‫؍‬ 52.91, P < 0.001). Finally, quantitative realtime reverse transcription-PCR assays for seven target gene (AhR, CYP1A1, CYP1B1, GSTM1, GSTM3, GSTP1, and GSTT1) and three reference gene [glyceraldehyde-3-phosphate dehydrogenase (GAPDH), ␤-actin, and 36B4] transcripts were performed on buccal specimens from 42 subjects. In multivariate analyses, gender, tobacco smoke exposure, and other factors were associated with the level of expression of CYP1B1, GSTP1, and other transcripts on a gene-specific basis, but substantial interindividual variability in mRNA expression remained unexplained. Within the power limits of this pilot study, gene expression signature was not clearly predictive of lung cancer case or control status. This noninvasive and quantitative method may be incorporated into high-throughput human applications for probing gene-environment interactions associated with cancer.

No abstract

Using an anchored oligo(dT) based RT-PCR approach we quantified endogenous expression of ten microRNAs in six cell lines. This identified a miRNA, miR-200c, with variable expression, ranging from undetectable in MDA-MB-231 and HT1080 to highly expressed in MCF7. The variable expression provided a model system to investigate endogenous interactions between miRNAs and their computationally predicted targets. As the expression level of the predicted mRNA targets and miR-200c in these lines should have an inverse relationship if cleavage or degradation results from the interaction. To select targets for analysis we used Affymetrix expression data and computational prediction programs. Affymetrix data indicated approximately 3500 candidate mRNAs, absent in MCF7 and present in MDA-MB-231 or HT1080. These targets were cross-referenced against approximately 600 computationally predicted miR-200c targets, identifying twenty potential mRNAs. Expression analysis by qRT-PCR of these targets and an additional ten mRNAs (selected using the prediction program ranking alone) revealed four mRNAs, BIN1, TCF8, RND3 and LHFP with an inverse relationship to miR-200c. Of the remainder, the majority did not appear to be degraded (and may be translational targets) or were undetectable in the cell lines examined. Finally, inhibition of miR-200c using an anti-miRNA 2'-0-Methyl oligonucleotide (AMO) resulted in an increase in expression of one of the targets, the transcription factor TCF8. These results indicate that a single miRNA could directly affect the mRNA levels of an important transcription factor, albeit in a manner specific to cell lines. Further investigation is required to confirm this in vivo and determine any translational effects.