P53RRA functions as a tumor suppressor. A, qRT-PCR analysis was conducted to detect P53RRA levels in A549, SPCA1, and H359 cells that were stably transfected with the P53RRA expression plasmid. B, P53RRA inhibited cell growth in A549, SPCA1, and H522 cells, as demonstrated by MTT assay. C, P53RRA inhibited colony formation in cells as indicated. D–L, Nude mice are shown after injection of A549, SPCA1, and H522 cells stably expressing the control vector or P53RRA expression plasmids. Tumor formation (D, G, and J) was monitored at the indicated time points, tumor formation (E, H, and K) was shown, and tumor weight (F, I, and L) was recorded (n = 6). M, qRT-PCR analysis was conducted to detect the P53RRA levels in HBE cells that were stably transfected with two distinct target gene shRNA expression vectors or a control vector (shCTRL). N and O, Depletion of P53RRA in HBE cells promoted cell proliferation (N) and colony formation (O). *, P < 0.05; **, P < 0.01; ***, P < 0.001.