SP1 and cancer: We gratefully acknowledge K. and F. Hoppe-Seyler (German Cancer Research Center, Heidelberg) for kindly providing human Sp1 expression vector, E. Stanbridge (Department of Microbiology and Molecular Genetics, School of Medicine, University of California, Irvine) for kindly providing “444” cells, R. Zawatzky (German Cancer Research Center, Heidelberg) for critically reading the manuscript and T. Polonio (German Cancer Research Center, Heidelberg) for assistance in the statistical analysis.