Role of gp91phox homolog Nox1 in Cell Transformation of Human Keratinocytes
Final Report Abstract
The NADPH oxidase (Nox) family of enzymes generates reactive oxygen species (ROS). Overproduction of ROS has long been implicated as a risk factor in cancer development. Among Nox isoforms, Nox1 was the first enzyme which is implicated in Ras oncogene‐ induced cell transformation of mouse fibroblasts. About 90% of all human cancers originate from epithelial cells, i.e., keratinocytes. Compared to mouse fibroblasts, cell transformation of human keratinocytes is a rare event, and occurs in a multi‐step manner. Our research program has explored possible involvement of Nox1 in cell transformation of human keratinocytes. Our results showed that Nox1 cannot elicit immortalization of normal human epidermal keratinocytes (adult NHEK), thus Nox1 by itself is not an oncogene. Nox1 however can induce preneoplastic cells from immortalized keratinocytes indicating that Nox1 may participate in transformation step beyond immortalization. Nox1‐induced preneoplastic cells were resistant against calcium‐induced differentiation capable of proliferating in standard medium. From the total of six preneoplastic cell lines, two different phenotypes include cobblestone and spindle cells thus representing model cells available for any investigations to study epithelial‐mesenchymal‐transition. Spindle cells are the more transformed phenotype than cobblestone cells by exhibiting cell survival advantage, anchorage‐independent growth and invasiveness. All six cell lines express keratin 18 (K18) while a spindle line additionally expresses keratin 8 (K8). This observation has raised a question whether Nox1 can regulate the expression of these proteins. Because K8 and K18 are intermediate filament proteins persistently expressed in a wide variety of carcinomas, this K8/K18 regulation may represent a mechanism for involvement of Nox1 in early steps of neoplastic progression. This implicated role of Nox1 had not been anticipated prior to DFG funding. Our research findings have given insights into the understanding of how Nox1 is involved in cancer progression. Further experiments are warranted to dissect the underlying mechanisms of K8/K18 regulation by Nox1 via phosphorylation. Our results will be submitted for publications in Journal Biological Chemistry and Journal of Investigative Dermatolology.
Publications
- Poster Presentation title ‘Redox Regulation of Cell Signaling during Early Stages of Epithelial Carcinogenesis’ at Oxygen Club of California‐ Oxidants and Antioxidants in Biology, Sept 2005, Alba, Italy
W. Chamulitrat, R. Schmidt, A. Huber and W. Stremmel
- Poster Presentation title ‘Nox1 inhibits terminal differentiation of cultured immortalized human keratinocytes generating daughter cells that express simple epithelial keratins K8/18’ at XIII Congress of the Society for Free Radical Research International, Aug 2006, Davos, Switzerland
W. Chamulitrat, R. Schmidt, A. Huber, D. Riedel, W. Stremmel
- Role of superoxide‐generating Nox1 in neoplastic transformation of human epithelial cells. In: Proceedings of the 13 Congress of the Society for Free Radical Research International. Davos (Switzerland), 15‐ 19 August 2006, Medimond International Proceedings: Bologna, Italy, pp. 87‐90, 2006
Chamulitrat, W.,Huber, A., Riedel, H., Stremmel, W
- Nox1 induces differentiation resistance in immortalized human keratinocytes generating cells that express simple epithelial keratins. J Invest Dermatol. 2007;127(9):2171‐83
Chamulitrat W, Huber A, Riedel HD, Stremmel W
- Poster Presentation title ‘Expression of smooth muscle‐specific proteins in human gingival keratinocyte cell lines containing gp91phox homolog Nox1: possible involvement of MEF2B’ at The Society for Free Radical Research‐ European Region, July 2007, Berlin, Germany
W. Chamulitrat, A. Sattayakhom, Q. Sun, J. Backs, W. Stremmel
- Discrimination of epithelium‐like and fibroblast‐like phenotypes derived from ethanol‐treated immortalised human gingival keratinocytes in epithelial equivalents. Cell Tissue Res. 2008;332(1):57‐71
Müssig E, Steinberg T, Kohl A, Chamulitrat W, Komposch G, Tomakidi P
- Human papillomavirus 16 E6/E7‐immortalized human gingival keratinocytes with epithelial mesenchymal transition acquire increased expression of cIAP‐1, Bclx and p27(Kip1). Exp Dermatol. 2009;18(12):1067‐9
Chamulitrat W, Sattayakhom A, Herold‐Mended C, Stremmel W
- Poster Presentation title ‘Nox1 regulates keratin 18 protein by ubiquitin‐proteasome pathway in human immortalized epithelial cells’ at The Society for Free Radical Research‐ European Region, June 2010, Athens, Greece
A. Sattayakhom, W. Ittarat, W. Stremmel, W. Chamulitrat
