Total RNA was isolated from cultured cells using TRIZOL reagent (Invitrogen). 2 μg total RNA was then reverse-transcribed using the Transcriptor First Strand cDNA synthesis Kit (Roche, Mannheim, Germany) with random hexamers. GSN mRNA was detected using Fast SYBR green PCR master mix (PE Applied Biosystems, Foster City, CA, USA) according to the manufacturer's protocol, and the primer sequence for GSN and GAPDH was as follows: GSN-QF: 5′-GCT GAG GTT GCC GCT GGT G-3′, and GSN-QR: 5′-TGT GTT GGT TGC ATT TCC TTT TTG-3′; GAPDH-F: 5′-TGG TAT CGT GGA AGG ACT CAT GAC-3′, and GAPDH-R: 5′-ATG CCA GTG AGC TTC CCG TTC AGC-3′. Relative mRNA expression of GSN was calculated with the comparative threshold cycle (Ct) (2−ΔΔCt) method.