Analysis of interleukin 6 (IL-6)-stimulated differential gene expression in human myeloma cells

IL-6 serves as a potent growth factor for human myeloma cells. In contrast, IL-6 functions as a differentiation factor for normal B cells and plasmablasts. Because the end-result of cytokine signaling is gene transcription, it follows that aberrant growth of myeloma cells in response to IL-6 may result from differential expression of certain genes. To investigate this hypothesis, differential display reverse transcriptase polymerase chain reaction was used to identify IL-6 responsive genes in 4 IL-6 dependent myeloma cell lines. Each cell line was deprived of IL6 for 24 hours, recultured in medium ±IL-6 for 4 and 24 hours and total RNA was isolated. cDNA was generated using one base anchored oligodT primers. This same primer was then used with arbitrary 5'8-mers to amplify a pool of cDNAs representative of differentially expressed mRNAs. cDNAs were separated on a denaturing acrylamide gel and those bands that were induced to appear or disappear in response to IL-6 in all 4 cell lines were isolated, subcloned, and sequenced. To date, in addition to cloning several novel sequences that are being further characterized, we have also observed differential expression of cDNAs encoding MAC 30, CD44, the gp80 component of the IL-6 receptor and the PC4 positive transcription cofactor. This approach has the potential to identify common genetic events that are crucial in allowing IL-6 driven growth of malignant plasma cells.