1. Oral and Pharyngeal Cancer Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD 20892-4340, U.S.A.
2. Cancer Research Institute, Catholic Research Institutes of Medical Science, The Catholic University of Korea, 505, Banpo-dong, Sucho-Ku, Seoul, 137-040, Korea
3. Bioengineering and Physical Science Program, National Institutes of Health, Bethesda, MD 20892-4340, U.S.A.