The response of tumour cells to radiation and cytotoxic drugs– A comparison of clonogenic and isotope uptake assays

Abstract

Summary We have carried out a series of experiments to compare the response to radiation and drugs of cells disaggregated from solid tumours as assayed by clonogenic survival and by an isotope incorporation method. This latter assay consisted of measuring the 24h uptake of tritium labelled thymidine into cells plated in liquid medium upon a layer of semi-solid agar. The isotope was administered 4 days after plating. For cells from the RIF-1 mouse tumour, good agreement was seen between response to radiation, adriamycin, vincristine and CCNU as measured by the two assays. The two curves for radiation response, for example, showed similar shoulders and subsequent exponential regions. For cells from xenografts of the NCI-H69 human small cell lung cancer line, the response to radiation was dose-related for both assays, but the curve for clonogenic assay was about twice as steep as that for isotope uptake. For a range of five cytotoxic drugs, good agrement was seen between the two assays over the first 1N decades of response but with a tendency for the isotope uptake curve to plateau with further increasing drug dose.It appears that, at least for these two well-defined experimental tumour systems, the isotope uptake assay can provide a rapid quantitative assessment of cellular drug and radiation sensitivity comparable to that provided by clonogenic assay but in a much shorter period of time.

A Possible Correlation Between Growth-Factor Sensitivity and Response to Mitoxantrone Treatment in a Murine Myeloid Leukaemia (SA7HD) Cell Line

“…This reversion was detected by both the 3HTdR incorporation assay and the clonogenic assay, which were in agreement (8,17). The size of the initial leukaemic cell inoculum determines the extent of recovery of growth-factor sensitivity for a given mitoxantrone dose.…”

A comparison of two in vitro assays of cell response following in vitro drug and radiation exposures of human tumour xenograft cells

“…There is however an apparent increase in resistance as measured by the [3H]TdR uptake assay once the rate of uptake of [3H]TdR falls to 1% and below that of controls. The plateau in response (Figures 1 and 2a) is similar to the findings of Twentyman et al (1984) who noted the tendency for the [3H]TdR assay to plateau at between one to two decades of cell response after treatment of H69 lung xenograft cells with X-rays and the cytotoxic drugs adriamycin, melphalan, nitrogen mustard and CCNU.…”

A new formazan amplified clonogenic assay for cytotoxicity testing

“…In an attempt to overcome clonogenic assay problems such as low plating efficiencies, clumping artifacts and assay period, many short-term assays have been developed, including dye exclusion techniques (Weisenthal et al, 1983), tritiated thymidine uptake (Twentyman et al, 1984), radiolabeled glucose utilization (Von Hoff et al, 1985), and automated image analysis of Coomassie blue stained cells (Fraser et al, 1986). In addition, the tetrazolium salt (MTT) developed by Mosmann (1983) which measures the metabolic activity of cells is well accepted.…”