Relative levels of mRNA encoding individual APM components in immunomagnetically purified premalignant and malignant (CD138⁺) BM plasma cells determined by real-time reverse-transcription polymerase chain reaction and the 2^−ΔΔCt method. indicates MGUS patients; and , MM patients. APM transcript levels were normalized to those of glyceraldehyde 3-phosphate dehydrogenase in the same samples and then expressed as fold change relative to the average value for normal (CD38⁺) plasma cells from controls. Values shown are mean and SD for 20 MGUS and 20 MM patients. *P < .05, **P ≤ .005, Mann-Whitney test.