TRANSCRIPTION OF GENES ENCODING GRANULOCYTE-MACROPHAGE COLONY-STIMULATING FACTOR, INTERLEUKIN-3, AND INTERLEUKIN-6 RECEPTORS AND LACK OF PROLIFERATIVE RESPONSE TO EXOGENOUS CYTOKINES IN NONHEMATOPOIETIC HUMAN-MALIGNANT CELL-LINES

Studies in recent years have suggested that human tumor cell lines are capable of responding in vitro to hematopoietic growth factors. In th e present study, we investigate the transcription of the alpha and bet a subunits of granulocyte-macrophage colony-stimulating factor (GM-CSF ) receptor, the alpha and beta subunits of interleukin 3 (IL-3) recept or, and the single subunit of interleukin 6 (IL-6) receptor and its as sociated gp130 transduction protein by PCR amplification of reverse-tr anscribed cellular mRNA in 34 malignant cell lines derived from a vari ety of histological cell types. mRNA for only a single subunit polypep tide was found in a significant minority of cell lines (23%), while in 20% both the alpha and beta subunits of either the GM-CSF receptor or the IL-3 receptor were detected among a number of different histologi cal cell types. Transcription of the gene encoding the IL-6 receptor w as found in 38% of cell lines, and all lines transcribed the gp130 tra nsduction protein, consistent with previous observations on the ubiqui ty of that polypeptide. In order to test the in vitro effect of exogen ously added growth factors on those malignant cell lines transcribing complete cytokine receptor, either GM-CSF, IL-3, or IL-6 was added in therapeutic concentrations (20-500 ng/ml) and cellular proliferation w as measured by incorporation of [H-3]thymidine. No stimulation was see n at either 3 and 6 days of culture. Production of cytokine by these c ell lines was investigated at the level of transcription and by assay of peptide product. None transcribed mRNA for either GM-CSF or IL-3, w hile 5 of 6 (STD, DOZ, ADE, Hep-2, and Detroit) expressed IL-6 mRNA. O f these latter, 2 cell lines (ADE and Hep-2) produced IL-6 as determin ed by bioassay, while none produced GM-CSF or IL-3 by enzyme-linked im munosorbent assay. This suggests that in the case of GM-CSF and IL-3, failure to proliferate on addition of cytokine is not due to the prior presence of endogenous production. In contrast, at least a subset of malignant cell lines may involve a closed IL-6 autocrine loop saturati ng cell surface sites. These findings suggest that the ability to tran scribe the genes encoding cytokine receptor is by itself insufficient to render cells cytokine responsive and that malignant cells may lack the cellular machinery for cytokine-induced proliferation. This in tur n suggests that therapeutic administration of either GM-CSF, IL-3, or IL-6 may involve no additional risk of tumor regrowth in vivo.