Human ether à go-go potassium channels in lung cancer cells and its modulation by environmental pollutants.

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Introduction: Human ether à go-go (Eag1) potassium channels possess oncogenic properties and display a very restricted distribution in normal tissues but a more ubiquitous and abundant expression in tumor biopsies. Inhibition of either Eag1 gene expression or channel activity decreases tumor cell proliferation in vitro and/or tumor growth in vivo. Therefore, Eag1 channels have been proposed both as tumor markers and therapeutic targets for several types of cancer. Because some cervical cancer etiological factors like human papilloma virus oncogenes regulate Eag1 gene expression, these channels have also been suggested as early markers of cell proliferation. Lung cancer is the first cause of mortality by malignant tumors in several countries and exposure to environmental pollutants has been associated to lung cancer incidence. Normal bronchial epithelium display no Eag1 expression; in contrast, Eag1 is overexpressed in lung cancer biopsies; nevertheless, whether Eag1 is modulated by environmental pollutants remains unknown. Here we studied Eag1 gene expression in several lung cancer cell lines and the possible Eag1 modulation by some environmental pollutants, namely, acrolein (a smoke cigarette compound suggested to be very important in cigarette smoke-induced lung cancer), exhaust diesel particles and urban dust in A-549 lung cancer cells.
 >Methods: Lung cancer cell lines (A-549, A-427, SK-MES-1, Calu-1 and SK-LU-1) were obtained from the American Type Culture Collection (ATCC, USA) and cultured following the manufacturer´s instructions. A-549 cells were incubated with acrolein (1 or 20 μM, Fluka, Switzerland), urban dust (5 or 10 μg/cm², NIST 1649a, USA) or exhaust diesel particles (5 or 10 μg/cm²) during 12, 24 and 48 hours. RNA extraction was performed with Trizol and 5 µg of total RNA were used to obtain cDNA. Eag1 and GAPDH (as a constitutive gene) were amplified with specific probes by real time PCR. Data were analyzed by the ΔΔCt method and by the threshold cycle alone.
 >Results: Eag1 mRNA was found to be endogenously and differentially expressed in most of the lung cancer cell lines (A-549 > SK-LU-1 > SK-MES-1 > Calu). Acrolein up-regulated Eag1 expression in a concentration and time-dependent manner. Urban dust and exhaust diesel particle up-regulated Eag1 mainly at the lowest concentration.
 >Conclusions: Because acrolein, urban dust and exhausted diesel particles up-regulate gene expression of oncogenic Eag1 channels, our results suggest that environmental pollutants might enhance tumor growth by regulating Eag1. Despite more studies are needed to determine the effect of environmental pollutants on Eag1 expression in normal lung cells, our results also suggest Eag1 as a marker of cell exposure to the environmental pollutants here studied.