[A study of MTT-hybrid assay using human bone and soft tissue tumor cells]

We investigated a new chemosensitivity test, MTT-hybrid assay, which was a hybrid of MTT colorimetric assay and double-layered soft agar colony assay, using human bone and soft tissue tumor cells. MTT formazan crystals produced by viable cells in the soft agar medium were solubilized by SDS at 60 degrees C. The absorbance (560 nm) is directly proportional to the cell number over a wide range. The absorbance increased in proportion to colonial growth of osteosarcoma cells, while it decreased in a human diploid cell strain in a few days. Drug sensitivity of tumor cells is supposed to be assessed without contaminating normal cells by MTT-hybrid assay in primary tumor samples. Good correlation of IC50 was observed between MTT-hybrid assay and colony assay. The MTT-hybrid assay shows potential value as a rapid predictive test for chemotherapeutic agents in an individual patient.