Time-lapse video reveals immediate heterogeneity and heritable damage among human ileocecal carcinoma HCT-8 cells treated with raltitrexed (ZD1694)

Background: Cellular heterogeneity in drug response has important clinical implications, and is believed to develop over many generations during clona l evolution in human tumors. The purpose of this study was to determine the level of heterogeneity exhibited by sister cells soon after their birth. Methods: Human ileocecal carcinoma cells (HCT-8) were followed up to 11 day s in vitro after a 2-h exposure to 1 muM raltitrexed (IC95) in a time-lapse video system. Results: Over five experiments, 414 cells were followed after exposure to r altitrexed. Immediate sterility occurred in 74% of treated cells. Only 6% o f cells could produce more than two generations of offspring, and heterogen eity in drug response was seen. Comparing sister cells < 24 h old, the more proliferative sibling produced up to 73 times more offspring, with a media n ratio of 9.0 (control median = 1.19). Offspring of prolific drug-treated cells had a decreased probability of division (68% compared with 92%) and a n increased average interdivision time (19.0 h compared with 15.1 h). Conclusions: Short-term exposure to raltitrexed resulted in increased inter division times and production of sterile offspring extending seven generati ons. Cellular heterogeneity (difference in proliferation potential comparin g drug-treated sister cells) was evident without a period of clonal evoluti on. Cytometry 41:252-260, 2000. (C) 2000 Wiley-Liss, Inc.