KRAS and neoplasm: (B–D) Mean ± SEM of urethane-induced tumor (B) burden, (C) multiplicity, and (D) size in tamoxifen-treated SftpcCreER/CreER;Trp53fl/fl mice in a homozygous native (B, C: n = 30 mice; D: n = 11 tumors) and heterozygous or homozygous (B, C: n = 51 mice; D: n = 42 tumors) ex3op Kras background.