KRAS and cancer: The in-cell K-Ras-G12D covalent labeling kinetics using a western blot time course mirrored the recombinant protein results (Fig. 3c), where (2R,3S)-G12Di-6 labeled endogenous K-Ras-G12D completely in homozygous KRASG12D/G12D cancer cell line SW1990 within 2 h as indicated by the gel mobility shift in the anti-Ras immunoblot, and concomitant reduction of the phospho-ERK levels.