MCF-10A and HCT116 cells with stable silencing of CEACAM1 exhibit normal regulation of p21/pRb in response to DNA damage. (a) MCF-10A cells stably transfected with CEACAM1 shRNA vector no. 25 (CEACAM1-KD 025) or with a control shRNA vector (CTRL) were incubated in the presence or the absence of 1.47 nM NCS for the indicated time points, lysed, and analyzed for p21/Waf1, pRb Ser 807/811-p, pRb, or β-actin by western blotting. (b) MCF-10A cells stably transfected with CEACAM1 shRNA vector no. 25 (CEACAM1-KD 025) or with a control shRNA vector (CTRL) were incubated in the presence or the absence of NCS 1.47 nM for 24 h in duplicate as indicated, lysed, and analyzed for p21/Waf1, pSer15-p, p53, or β-actin by western blotting. (c) HCT116 cells stably transfected with CEACAM1 shRNA vector no. 26 (CEACAM1-KD 026), with CEACAM1 shRNA vector no. 28 (CEACAM1-KD 028) or with a control shRNA vector (CTRL) were incubated in the presence of 20 μM etoposide or dimethyl sulfoxide (DMSO (solvent)) for 1 h, washed with phosphate-buffered saline and incubated in new medium for 3 days. At the end of the incubation the cells were lysed and analyzed for p21/Waf1, pRb Ser 807/811-p or pRb by western blotting.