[1] Mayo Clin, Miles & Shirley Fiterman Ctr Digest Dis, Coll Med, Rochester, MN 55905 USA
[2] Mayo Clin, Dept Oncol, Coll Med, Rochester, MN 55905 USA
[3] Mayo Clin, Dept Lab Med & Pathol, Coll Med, Rochester, MN 55905 USA
[4] Mayo Clin, Div Gastroenterol & Gen Surg, Coll Med, Rochester, MN 55905 USA
[5] NCI, Expt Carcinogenesis Lab, Bethesda, MD 20892 USA