GAPDH and lung carcinoma: In our results, the expression of linear ITCH (normalized to GAPDH) showed no difference between total RNA and poly(A)-enriched RNA in both A549 cells and NCI-H460 cells (Figure 1(d)), while the expression of cir-ITCH was significantly decreased in poly(A)-enriched RNA compared with total RNA in these two lung cancer cell lines (Figure 1(d)).