Growth slow‐down and growth arrest of human colon carcinoma cells HCT‐8 in vitro after exposure to 5‐fluoro‐2′‐deoxyuridine

Abstract

Cellular heterogeneity in drug response denotes a mixed response among individual cells in a drug treated population. Individual cell responses may be more complex than 'cell kill' and 'no response'. In this study we employed a colony formation assay and high-resolution image analysis to detect the various responses such as immediate and delayed cessation of growth, growth delay and growth slow-down, at the level of the individual colony. The evaluation was carried out using a human ileocaecal adenocarcinoma cell line (HCT-8) and the anti-tumour agent 5-fluoro-2'-deoxyuridine (FdUrd). In the presence of a drug concentration which, in standard monolayer assays, inhibits the growth to about 50% (IC50) only about 20% of the colonies ceased to grow and the remaining colonies grew at a growth rate of about 70% of control. At an FdUrd concentration which, in standard monolayer assays, reduced growth by > 90% (> IC90), about 50% of the cells grew, with growth rates of about 30% of control. The slowing of growth, most prominent at lower drug concentrations, should be considered in determining mechanisms of drug action at the individual cell level. In clinical situations in which high drug doses are precluded by toxicity to normal tissues, growth slow-down may play a significant role in tumour response.

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

“…An increase in interdivision time has been reported among HCT‐8 cells exposed to the thymidylate synthase inhibitor, FUdR (15), similar to the findings in this study. However, that study was conducted at the level of the individual colony and had limited data on the behavior of individual cells within the colony.…”

“…In cell proliferation assays, several mechanisms may contribute to growth inhibition (18). These mechanisms include a reduction in the number of cells proliferating (growth fraction) and an increase in interdivision time (cell cycle time), an effect that has been discussed in an earlier study of colony formation by HCT‐8 cells (15, 18). In the present experiments, the growth fraction was decreased from a control median value of 92.9% (range 85.9–99.2%) to a median after drug treatment of 26% (range 21–31%).…”

“…Time‐lapse recording methods and sophisticated mathematical analyses have been applied to colony formation assays, to characterize inheritance of proliferative capacity and heterogeneity in growth comparing normal and tumor cells (8–14). We undertook a study of the response of individual cells of a human ileocecal carcinoma cell line (HCT‐8), using a time‐lapse video recorder with semiautomated computer analysis, to follow up on earlier work conducted at the individual colony level (15–18).…”

Automatic analysis of growth onset, growth rate and colony size of individual bone marrow progenitors

“…Time-lapse video images allowed dynamic descriptions of the growth in the assay (2, 3). Slocum and co-workers developed a method to monitor and evaluate the growth history of individual cells plated in semi-solid medium (6)(7)(8). The technique is based on measurement of the colony diameter using pseudo dark field microscopy and thus limited to more or less coherent, non-overlapping aggregates.…”