Carcinogenesis Advance Access originally published online on May 29, 2009
Carcinogenesis 2009 30(8):1433-1442; doi:10.1093/carcin/bgp129
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Increased PEA3/E1AF and decreased Net/Elk-3, both ETS proteins, characterize human NSCLC progression and regulate caveolin-1 transcription in Calu-1 and NCI-H23 NSCLC cell lines
Pulmonary Center
1 Department of Medicine
2 Department of Pathology, Boston University School of Medicine, 72 East Concord Street, R304, Boston, MA 02118, USA
3 Department of Pathology, Edward Hines, Jr. VA Hospital, 5000 South 5th Avenue, Hines, IL 60141, USA
* To whom correspondence should be addressed. Tel: +1 617 638 4860; Fax: +1 617 536 8093;Email: kasloan{at}bu.edu
Caveolin-1 protein has been called a ‘conditional tumor suppressor’ because it can either suppress or enhance tumor progression depending on cellular context. Caveolin-1 levels are dynamic in non-small-cell lung cancer, with increased levels in metastatic tumor cells. We have shown previously that transactivation of an erythroblastosis virus-transforming sequence (ETS) cis-element enhances caveolin-1 expression in a murine lung epithelial cell line. Based on high sequence homology between the murine and human caveolin-1 promoters, we proposed that ETS proteins might regulate caveolin-1 expression in human lung tumorigenesis. We confirm that caveolin-1 is not detected in well-differentiated primary lung tumors. Polyoma virus enhancer activator 3 (PEA3), a pro-metastatic ETS protein in breast cancer, is expressed at low levels in well-differentiated tumors and high levels in poorly differentiated tumors. Conversely, Net, a known ETS repressor, is expressed at high levels in the nucleus of well-differentiated primary tumor cells. In tumor cells in metastatic lymph node sites, caveolin-1 and PEA3 are highly expressed, whereas Net is now expressed in the cytoplasm. We studied transcriptional regulation of caveolin-1 in two human lung cancer cell lines, Calu-1 (high caveolin-1 expressing) and NCI-H23 (low caveolin-1 expressing). Chromatin immunoprecipitation-binding assays and small interfering RNA experiments show that PEA3 is a transcriptional activator in Calu-1 cells and that Net is a transcriptional repressor in NCI-H23 cells. These results suggest that Net may suppress caveolin-1 transcription in primary lung tumors and that PEA3 may activate caveolin-1 transcription in metastatic lymph nodes.
Abbreviations: ChIP, chromatin immunoprecipitation; EDTA, ethylenediaminetetraacetic acid; ETS, erythroblastosis virus-transforming sequence; mRNA, messenger RNA; NSCLC, non-small-cell lung cancer; PCR, polymerase chain reaction; PEA3, Polyoma virus enhancer activator 3; QRT, quantitative real-time; RT, reverse transcription; SDS, sodium dodecyl sulfate; siRNA, small interfering RNA
Received November 14, 2008; revised May 15, 2009; accepted May 16, 2009.