Differential regulation of interleukin-1 alpha and interleukin-1 beta in K-562 cells

Interleukin (IL)-1 alpha and IL-1 beta are encoded by two separate genes, b ut both function as comitogens for lymphocyte activation. In this study, we observed K-562 cells to express constitutively mRNA for IL-1 alpha, althou gh IL-1 alpha was not detected in the growth-conditioned medium (GCM). Howe ver, IL-1 beta mRNA was not expressed unless the cells had been treated wit h phorbol myristate acetate (PMA), Both IL-1 alpha and IL-1 beta were detec ted in the GCM after the cells had been cultured with PMA, suggesting that IL-1 elaboration required PMA treatment. The K-562 cells treated with PMA d ifferentiated to the myeloblastic stage, as observed by nuclear morphologic properties by electron microscopy, PMA treatment induced de novo expressio n of CD61 or gpIIIa, a marker associated with megakaryoblasts. These result s showed that although K-562 cells constitutively expressed IL-1 alpha mRNA , PMA treatment was required for secretion. On the other hand, both the exp ression and secretion of LL-1 beta required treatment with PMA, This study showed that K-562 cells treated with PMA differentiated to the myeloblastic stage and expressed and secreted IL-1 alpha and IL-1 beta.