In this study we examine the dNTP supply system response to p53 loss by analyzing gene expression data from human mammary epithelial cells (HMEC) minimally transformed by stably knocking down p16, with and without p53 also knocked down, and data from the gene expression omnibus (GEO) [9] that includes: (a) normal human stromal breast tissue cells of Li-Fraumeni and healthy donors [10], (b) breast cancer cells that are p53 wild-type or mutated [11], and (c) KB cancer cells with p53R2 knocked down by p53R2 siRNA [12]. This evidence concerns the gene RRM2B and cancer.