1. Department of Medicinal Chemistry and Molecular Pharmacology, School of Pharmacy and Pharmaceutical Sciences, and the Purdue University Center for Cancer Research, Purdue University, West Lafayette, Indiana 47907
2. Department of Medicinal Chemistry, School of Pharmacy, Second Military Medical University, Shanghai 200433, China
3. Laboratory of Molecular Pharmacology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892