Total RNA was extracted using TRIzol Reagent and treated with RNase-Free DNase. Reverse transcription was carried out with 500 ng total RNA. Real-time PCR was performed using the ABI 7900 Real-time PCR system and TaqMan PCR mastermix (Life Technologies). Quantification of gene amplification was performed in duplicate using the ΔΔCt method. The expression level of each gene was normalized using 3 housekeeping genes: hypoxantine-guanine-phosphoribosyl-transferase (HPRT) gene, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene, and β2 microglobulin gene. Primers and probes are listed.