1. From the Department of Biological and Medical Research, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
2. Current address: SAIC-Frederick, National Cancer Institute at Frederick, P.O. Box B Frederick, Maryland, 21702 USA
3. From the Department of Medicine, College of Medicine, King Saud University, Riyadh, Saudi Arabia
4. From the Department of Pathology and Laboratory Medicine, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia