1. Department of Biochemistry, University of Padova, Viale G. Colombo 3, 35121 Padova, Italy, Venetian Institute for Molecular Medicine, Via Orus 2, 35129 Padova, Italy, Department of Experimental Oncology, National Cancer Institute, 20133 Milan, Italy, and Laboratoire de Chimie Thérapeutique, Section de Pharmacie, Quai Ernest-Ansermet 30, 1211 Genève, Switzerland