Chemosensitivity testing of fresh and continuous tumor cell cultures using lactate dehydrogenase

We have examined the use of the LDH (lactate dehydrogenase) assay for chemosensitivity testing in established and primary cultures of sarcoma, leukaemia and ovarian cancer in parallel with the MTT assay. The method we describe is rapid, sensitive and ideal for 96-well plate assays using adherent or suspension cultures. Excellent agreement between the two methods was observed (r = 0.936) using a variety of antitumour agents, with some notable exceptions. In the Bax (human synovial sarcoma) cell line MTT colour production by control cells was very low, thus MTT-->formazan production could not be relied upon as a definitive end point equating with cell number. In contrast, colour production of control cells using the LDH assay was significantly greater and all cultures tested were suitable for titration of chemosensitivity. There was a discrepancy between IC50 values obtained either by cell counting or MTT in the HTB88 (human leiomyosarcoma) line treated with 5-FU (59.9 microM vs > 200 microM, respectively). However, cell counting agreed well with the LDH assay (IC50 47.3 microM). Whilst the MTT assay remains a reliable method for chemosensitivity testing, the LDH assay may prove more appropriate in certain experimental settings.