1. From the Department of Cell & Tissue Biology, Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA; the Department of Cell & Tissue Biology and Biomedical Sciences Graduate Program, University of California, San Francisco, San Francisco, CA; and the Department of Cell & Tissue Biology, Department of Medicine, Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA.