1. Department of Carcinogenesis, Swiss Institute for Experimental Cancer Research, CH-1066 Epalinges S/Lausanne, Switzerland.
2. Laboratory of Human Carcinogenesis, Division of Cancer Etiology, National Cancer Institute, Bethesda, MD 20892, USA.
3. Cancer Institute, Chinese Academy of Medical Sciences, Beijing, China.
4. Unit of Mechanisms of Carcinogenesis, International Agency for Research on Cancer, 69372 Lyon Cédex 08, France.