Augmented expression of p21 and MDM2 during serine and glycine (SG)-deprivation promotes adaptation in R248W cells independently of MDM2-facilitated SSP induction. a Growth of the indicated cell lines treated with non-targeting control or p21 siRNA and cultured in SG-depleted medium for 7 days. iRFP intensity in each well on day 7 (top) and iRFP level per well relative to the day 2 reading (bottom) shown for each cell line. Data are represented as the mean of triplicate wells ± SEM for each condition. b Growth of the indicated cell lines treated with non-targeting control or MDM2 siRNA and cultured in SG-depleted medium for 7 days as in (a). c Western blot PSAT-1 and PSPH in the indicated cell lines cultured in SG-depleted medium for 1 or 2 days. Note: this is a re-probe of the blot shown in Fig. 1f, where MDM2 and p21 levels are shown. The ACTIN loading control blot is therefore the same in both figures. d Western blot for SSP enzymes PSAT-1, PSPH and PHGDH, and MDM2 in the indicated cell lines treated with non-targeting control or MDM2 siRNA and grown in SG-depleted medium for 2 days. e Western blot for HA-MDM2 in p53 KO cells transfected with an HA-tagged MDM2 expression construct (HA-MDM2) or a control vector containing GFP. f Growth of p53 KO cells expressing HA-tagged MDM2 or a control vector (EV) and cultured in SG-depleted medium for 9 days. Data are presented as mean ± SEM and depicted as iRFP intensity relative to the initial measurement obtained from triplicate wells per condition.