The microtiter SDI test is more advantageous than the SDI test for assessing the chemosensitivity of human tumor cells

The in vitro succinate dehydrogenase inhibition (SDI) test was adapted to be used with microtiter plates and this microtiter SDI (mSDI) test was evaluated for clinical use of chemosensitivity testing, as compared to findings with the SDI test. The optimal conditions of the mSDI test were determined(1) 2–5 × 10 cells/well; (2) enzymatic disaggregation of solid tumors with the use of a mixture of 0.2% pronase, 0.25% collagenase, 0.1% DNase for 20 min at 37°C; (3) addition of 10 mM sodium succinate in the colorimetric reaction; and (4) use of dimethyl sulfoxide (DMSO) as a solvent for extraction of formazan product. Good correlations were observed between the mSDI and the SDI tests when S-180 cells (r = 0.890–0.996) or 16 human fresh tumor cells (r = 0.731–0.999) were exposed to six anti-cancer drugs (carboquone, adriamycin, mitomycin C, aclacinomycin A, cisplatin, 5-fluorouracil). Thus, the mSDI test facilitates testing of a large number of drugs with minimal amounts of specimens, and is expected to replace the SDI test for chemosensitivity testing of clinical tumor cells.