ALDH1B1 and neoplasm: We established A549 cells with ALDH6A1 or ALDH9A1 depletion (Supplementary Fig. 2e, f) and found that ALDH9A1 depletion increased tumor cell death in confining pores (Supplementary Fig. 2g), though its effect was weaker than that of ALDH1B1 ablation.