Total RNA was extracted from cultured cells using the TRIzol reagent (#15596-018; Ambion, Life Technologies, Carlsbad, CA) and reverse-transcribed to cDNA using the SuperScript III First-Strand Synthesis System (#18080-051; Invitrogen, Life Technologies, Carlsbad, CA). Gene expression was analyzed in triplicate using FastStart Universal SYBR Green Master with ROX (#04913850001; Roche Applied Science, Indianapolis, IN) on the Applied Biosystems 7900HT Fast Real-Time PCR System. Relative expression of each gene was calculated according to the 2−ΔΔCt method51. GAPDH was used as an internal control for normalization. Primers used for qRT-PCR were listed in Supplementary Table 2.