Cytokine gene expression in human multiple myeloma

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Abstract
Summary. In the present study the gene expression of cytokines promoting in vitro myeloma‐cell growth was investigated by Northern blot analysis using total RNA of 36 tumour samples of patients with multiple myeloma (MM) or plasma cell leukaemia and poly(A)+ RNA of 10 human myeloma cell lines (HMCL). These cytokines included interleukin (IL)‐1α, IL‐1β, IL‐3, IL‐6, granulocyte‐macrophage (GM)‐colony‐stimulating factor (CSF) and granulocyte (G)‐CSF. IL‐1β, IL‐6 and G‐CSF genes were coexpressed in most patients, although at variable levels. IL‐1α transcripts were detected in 32% of patients in whom coexpression of IL‐1β gene was found. IL‐3 gene was not expressed in patients' cells and GM‐CSF mRNA was detected in only 1/32 patients. No detectable transcripts for the above cytokines were present in HMCL, whereas IL‐6 gene was expressed in 2/10 HMCL. We also looked for the presence of transcripts for IL‐2, leukaemia inhibitory factor (LIF) and transforming growth factor (TGF)β in cells of tumour samples from the same patients and in HMCL. IL‐2 gene was not expressed in MM patients and HMCL. Weak expression of LIF gene was detected in three patients (9%), and transforming growth factor β (TGFβ) mRNA was observed in 12/12 tumour samples analysed and all HMCL. These results suggest that, among cytokines shown to control myeloma‐cell growth in vitro, IL‐1, IL‐6 and G‐CSF could play a role in the development of myeloma disease in vivo.