In vitro synergistic activity of PDN-IFN alpha and NM + IFN alpha combinations on fresh bone-marrow samples from multiple myeloma patients.

The differential staining cytotoxicity (DiSC) assay was used to evaluate the in vitro sensitivity of tumour and normal bone-marrow cells from 21 multiple myeloma (MM) patients to antitumour agents methylprednisolone (PDN), nitrogen mustard (NM) and recombinant interferon alpha-2b (IFN alpha) tested singly and in the combinations PDN + IFN alpha and NM + IFN alpha. Both the PDN-IFN alpha and NM-IFN alpha associations were more efficacious than any agents used singly in reducing the percentage of myeloma cell survival. However, whereas NM, alone and in combination with IFN alpha, provoked a severe reduction in normal bone-marrow population, PDN and PDN + IFN alpha induced an increase percentage survival of normal bone-marrow cells. These findings indicate that, at least in vitro, the PDN-IFN alpha combination exerts a great antitumor effect which is not associated with a relevant cytotoxic activity on normal myeloid cells.