MUC5AC and lung cancer: In addition, the circSULF2 is up-regulated in lung cancer tissues in comparison with adjacent normal lung tissues (Fig. S1f), and in lung cancer cell lines when compared to normal lung cell lines (Fig. S1g), and its expression is positively correlated with MUC5B (r = 0.266, P = 0.001) but not MUC5AC (Fig. S1h).