Use of a colorimetric microtiter (MTT) assay in determining the radiosensitivity of cells from murine solid tumors.

We assessed the use of a colorimetric assay for determination of radiosensitivity for cells taken directly from murine solid tumors. The assay uses microtier plates and measures the ability of viable cells to reduce a tetrazolium salt (MTT) to an insoluble form, a formazan salt. We established the dependency of the assay on the cell number and time of assay for two murine tumors (EMT-6 and RIF-1). We compared the MTT assay to the standard clonogenic assay and had good agreement of surviving fraction after radiation doses of 2 and 4 Gy. It is possible, therefore, to adapt the MTT assay for use with cell suspensions prepared directly from fresh murine tumors. This may provide a methodology for the determination of the clinical radiosensitivity of tumors including fresh clinical tumor specimens.