Direct Cloning of Human Neuroblastoma Cells in Soft Agar Culture1

An in vitro soft agar technique was used in an attempt to culture neuroblastoma cells from 71 bone marrow, 3 lymph node, and 2 solid tumor specimens from 18 patients with neuroblastoma. One-half of each specimen was sent for routine pathology studies and one-half was cultured in the soft agar system. Colonies appeared within 10 days in histologically positive bone marrows. Light microscopy, electron microscopy, catecholamine secretion, and karyology provided evidence that the colonies were composed of neuroblastoma cells. There were 38 instances in which histological study of the specimen demonstrated neuroblastoma cells. The soft agar system showed colony growth in 30 of these samples (79%). There were a total of 38 specimens that were histologically negative for neuroblastoma. Thirty of these 38 specimens showed no growth in the stem cell assay. Eight histologically negative specimens from 6 patients formed colonies in the soft agar system. Five of these 6 patients showed tumor histologically on prior or subsequent marrow examinations. In addition to a significant correlation between histological and soft agar cul ture results (p < 0.001 ), there exists a highly significant positive correlation between the number of colonies per plate and the histological status of the specimen (p < 0.005). Serial marrow samples were cultured on 7 patients. There appears to be an association between the number of colonies that develop in the plate and the clinical course and prognosis of the patient. Decreasing plating efficiencies (number of colonies per number of cells plated) correlated with tumor response. Increasing plating efficiencies indicated tumor relapse. A plating efficiency of >0.1% portended a particularly poor prognosis. Neuroblas toma grows well in this soft agar culture system. This excellent growth provides a good model for both clinical and basic science studies of neuroblastoma.