Fig. 3. Down-regulation of ERCC1 expression enhanced the capsaicin-induced cytotoxicity and growth inhibition. (A) A549 or H1975 cells were transfected with siRNA duplexes (200 nM) specific to ERCC1 or scrambled (control) in complete medium for 24 h prior to the treatment with capsaicin in complete medium for 24 h. The total RNA was isolated and subjected to real-time PCR for ERCC1 mRNA expression. (B and C) After the above-mentioned treatment, cytotoxicity was determined by MTS assay and trypan blue exclusion assay. (D) After the cells were transfected with si-ERCC1 or si-scrambled RNA, the cells were treated with capsaicin (25 μM) for 24, 48, and 72 h, after which living cells were determined by MTS assay. The results (mean ± SEM) were from three independent experiments. **p < 0.01 using Student's t-test for comparison between the cells treated with capsaicin in si-ERCC1 RNA or si-scrambled RNA-transfected cells.