ALK and lung cancer: To further validate whether RNase1 is also required for the ALK activity, we knocked down RNase 1 in PC-9 lung cancer cells co-expressing endogenous ALK and RNase1 by two different small hairpin RNAs (shRNAs) targeting RNase1 (Supplementary Fig. 2, e; lanes 2 and 3 vs. 1) and examined the effects on phospho-ALK, cell mobility and cell proliferation.