KRAS and adenoma: Sections of lung from immunized Cγ1-Cre KrasG12D show well-demarcated nodules composed mostly of sheets of bronchial epithelial cells and some “signet ring” cells with bland nuclear features and absence of mitotic figures consistent with adenomas or low-grade adenocarcinomas (Figure S2B–E). Tissue from lung tumors in two independent Cγ1-Cre KrasG12D mice shows partial recombination of the Kras allele (Figure S2F). The immunized and unimmunized negative control Cγ1-Cre mice showed no evidence of disease (Figure 3A).