Bone marrow cells freshly aspirated from the 10 consecutive untreated adult patients with acute nonlymphocytic leukemia were cultured by 2 different methods: the conventional agar culture method for myeloid colony formation and its modification by daily feeding with culture medium. In 5 patients, colonies grew in much higher numbers (4.7- to 330-fold) with feeding than without. Three patients grew colonies only with feeding. Two of these 3 patients required l-ascorbic acid in the fed medium for colony growth. Colonies did not grow from the remaining 2 patients by any method. In 7 patients the number of colonies grown with feeding were much higher, up to 170 times higher, than were those from normal control marrows, which grew the same number of colonies regardless of feeding or l-ascorbic acid. Peroxidase and Wright's stains indicated the myeloid differentiation of the cells in the leukemic marrow colonies. The leukemic origin of the colonies was proven by chromosomal analysis. The wide range of linearity between the number of cells plated and the number of colonies grown permits quantitative assay of colony-forming leukemic cells. This assay should be valuable for studies of chemotherapy, growth regulation, and differentiation of leukemic cells.

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This investigation was supported by NIH Grants RO-1 CA 20717 and S-501 RR 5373 and by the American Cancer Society, Kansas Division. Presented in part at the 67th Annual Meeting of the American Association for Cancer Research, Toronto, Ontario, Canada, May 4 to 8, 1976 (18).

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