Furthermore, there were animals in which a different transgene, Kras or EGFR, was expressed in individual tumor nodules (e.g., mouse number 798), implying that tumors from mice carrying oncogenic alleles of both Kras and EGFR have evolved by selecting against cells that express both mutant transgenes, further suggesting that expression of both these genes is detrimental. This evidence concerns the gene EGFR and neoplasm.