The distinct gene expression profiles of chronic lymphocytic leukemia and multiple myeloma suggest different anti-apoptotic mechanisms but predict only some differences in phenotype.

We compared gene expression in purified tumor cells from untreated patients with chronic lymphocytic (CLL) (n=24) and newly diagnosed multiple myeloma (MM) (n=29) using the Affymetrix HuGeneFL microarray with probes for approximately 6800 genes. Hierarchical clustering analysis showed that CLL and MM have distinct expression profiles (class prediction). Gene and protein expression (measured by flow cytometry) correlated well for CD19, CD20, CD23, and CD138 in CLL and MM, but not for immunoglobulin light chain, CD38 and CD79b in CLL, or CD45 and CD52 in MM. CLL and MM differentially expressed 18% of 130 apoptosis related genes, suggesting differences in mechanisms of cell survival.