Constitutive secretion of hematopoietic cytokines by human carcinoma cell lines and its up-regulation by interleukin-1 beta and phorbol ester

We investigated secretion of hematopoietic growth factors in ten human tumo r cell lines, derived from 5 different tissue types. The cell lines were st imulated transiently with interleukin-1 beta (IL-1 beta), IL-6, interferon- gamma (IFN-gamma), lipopolysaccharide (LPS) and tetradecanoyl phorbol 13-ac etate (TPA), respectively. Conditioned media (CM) were screened in a bioass ay using an indicator cell line which is growth factor-dependent and needs the supply of at least one hematopoietic cytokine. The CM of almost all tum or cell lines analyzed induced proliferation of this indicator cell line as documented by incorporation of [H-3]-thymidine. The majority of constituti vely cytokine-producing tumor cell lines could be induced to further increa se their amounts of secreted proliferation-inducing activity. The strongest inducers were TPA and IL-1 beta; weakly or not effective at all were IFN-g amma, LPS and IL-6. Enzyme-linked immunosorbent assay (ELISA) identified se veral cytokines and macrophage-colony-stimulating factor (M-CSF) and IL-6 w ere secreted at the highest concentrations. Especially in kidney cell lines , the levels of granulocyte macrophage-CSF (GM-CSF), M-CSF and IL-6 were fu rther strongly increased by the TPA and IL-1 beta pretreatment. The by far highest amounts of granulocyte-CSF (G-CSF) were elaborated by the bladder c ell line T-24 and could be further more than doubled by TPA. Other cell lin es, derived from esophagus, lung and pancreas, responded less strongly to t he pretreatment with the biomodulators. Our results demonstrating secretion of functionally active cytokines by human solid tumor cell lines suggest t hat these, to date so-called, hematopoietic cytokines are not entirely hema topoietic specific and might play a fundamentally important role in tumor c ell biology.