Further Biologic Characteristics of a Human Carcinoembryonic Antigen-Producing Colon Carcinoma Cell Line2

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Abstract
Several biologic characteristics of human carcinoembryonic antigen (CEA)-producing colon adenocarcinoma cells grown in vitro were analyzed. Doubling times of exponentially growing cells ranged from 34 to 38 hours for initial cell concentrations of 105 through 7×105/petri dish (4,290-30,030 cells/cm2). The generation time, as analyzed by pulse-labeled mitosis (PLM) techniques and calculated according to the model of Jansson, was 29.3 hours with a coefficient of variation of 22%. Cultures exposed to continuous incubation with tritiated thymidine had a growth fraction of 90%. Compartment distribution calculated in reference to cell cycle transit times measured by PLM techniques was similar to that defined directly by pulse cytophotometry (PCP). PCP analysis of cells in stationary phase of growth revealed a significant fraction of cells with S-phase DNA content, even though the simultaneously defined labeling index was only 1%. Adequate synchronization in S- and G2-phase was achieved by treatment of the cells with 7 mm thymidine for 24 hours. Centrifugal elutriation and mitotic selection techniques were clearly inferior in terms of reproducibility and cell yield. Colony formation was most efficient for cells plated in fresh medium and incubated for 20 days. Cells inoculated into nude mice produced tumor masses that presented morphologic markers similar to those defined for in vitro cells and were capable of synthesizing CEA.