Growth inhibitory activity of human lymphoblastoid and fibroblast interferons in vitro

Growth inhibitory activities of both human fibroblast (HuIFN-beta) and lymphoblastoid (HuIFN-alpha) interferons against 17 human cultured cell lines derived from leukemias and lymphomas were measured quantitatively by regrowth assay. Daudi cells were the most sensitive to both interferons. Three B-cell lines, one T-cell line and one non-T, non-B cell line were moderately sensitive to both interferons. Although the levels of sensitivity of these cell lines to the interferons were different, cells could be killed by the interferons. Eleven other cultured cell lines including three B-cell lines, three T-cell lines, two non-T, non-B cell lines, two myeloid cell lines and one monocytoid cell line were not sensitive to these interferons. The results indicated that the growth inhibitory activity of interferons was not always cell lineage-specific and cell lines which were sensitive to the one interferon were always sensitive to the other interferon, although the level of sensitivity was different. Cytocidal action of interferons was analyzed by use of the most sensitive Daudi cells. The results indicated that both interferons had a time-dependent cytocidal action, but not a concentration-dependent one. Knowledge of the mode of the cytocidal action may be useful for the design of optional therapeutic schedules using the interferons. The prediction of clinical effectiveness of interferon against hematologic malignancies is discussed, based on the level of in vitro sensitivity of cultured leukemia and lymphoma cell lines.