SMAD4 and neoplasm: For 10 out of 18 such genes harboring driver mutations in at least 5 cell lines (PTEN, PIK3R1, APC, CD58, B2M, ARID1A, BMPR2, SMAD4, MSH6, and EP300), we found a significant negative impact on the respective protein abundances, in line with their function as tumor suppressors, whereas missense mutations in TP53 were associated with elevated protein levels as previously reported (Bertorelle et al., 1996, Dix et al., 1994; ANOVA test; permutation-based FDR < 0.1; Figure 2A).