CD138-positive cell separation affects cancer gene expression in human myeloma cell lines

Gene expression (GE) profiling of multiple myeloma (MM) cells is a promising means of identifying high-risk MM patients. The analyses depend on plasma cell purification by CD138+ cell separation. Considering the sensitivity of gene transcription, we wanted to test if cell separation distorts true in vivo GE patterns. We performed a controlled study of running 4 human myeloma cell lines (HMCLs: U266, INA-6, RPMI 8226, and NCI H929) through a CD138+ separation procedure identical to the handling of clinical samples. We then compared the resulting effects on gene expression. Using U266 as a screening model, we performed global GE analysis using the Affymetrix Human Gene 1.0 ST array. Sample cells showed significant changes (adj. p<0,05) in 670 genes compared to the non-separated controls. We searched for upregulated genes of myeloma and/or cancer relevance and chose (in decending fold change order) FOS, DUSP1, MIRN21, NFKBIA, and ATF4 for PCR validation. Note: Only U266 cells were used for microarray analysis. The other cell lines were used later to validate the array results.