Synergistic antiproliferative effects of glucocorticoids and interferon‐α on some lymphoid cell lines

The Daudi B lymphoblastoid cell line was previously demonstrated to be highly sensitive to the antiproliferative effect of recombinant interferon‐αA (rlFN‐α). In the present study, glucocorticoid hormones were shown to act synergistically with rlFN‐α to further increase the sensitivity of Daudi cells to rlFN‐α.At 10⁶M, dexamethasone, prednisolone, or hydrocortisone alone had little effect on Daudi cell growth, but they greatly potentiated the antiproliferative activity of rlFN‐α. The synergy between rlFN‐α and glucocorti‐coids on Daudi cells was not related to the inhibitory effects of glucocorticoids on prostaglandin or leukotriene synthesis, since no synergy was observed between rlFN‐α and indomethacin or nordihydroguaiaretic acid. Glucocorticoids and rlFN‐α also had appreciable synergistic antiproliferative effects on two out of five other IFN‐sensitive lymphoid cell lines. When Raji B lymphoblastoid cells, which were quite resistant to the antiproliferative effect of rlFN‐α, were treated with the combination of glucocorticoids and rlFN‐α, no significant synergistic effects were observed. The synergistic antiproliferative effects of glucocorticoids and rlFN‐α observed with some IFN‐sensitive lymphoid cell lines in this in vitro study may have clinical relevance in the treatment of certain lymphoid malignancies that are sensitive to rlFN‐α therapy.