TP53 and cancer: Compared with the reference group carrying no risk genotype at either locus (i.e., MDM2 TT and p53 codon 72 PR/RR), those with a risk genotype on one of the loci, MDM2 (MDM2 GG/GT and p53 codon 72 PR/RR) were 1.54 times more likely to have cancer (P = 0.0319), and the highest hazard ratio of 3.25 was observed for those carriers with risk genotypes at both loci (P = 0.0367); this hazard ratio is close to the product of hazard ratios for the main effects of risk genotype at each locus (1.54×2.36 = 3.63), suggesting that the two SNPs together have a multiplicative joint effect.