1. 1Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093, U.S.A.
2. 2Shu Chien-Gene Lay Department of Bioengineering, University of California, San Diego, La Jolla, CA 92093, U.S.A.
3. 3Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093, U.S.A.
4. 4Moores Cancer Center, University of California, San Diego, La Jolla, CA 92093, U.S.A.