Knock-in of Oncogenic Kras Does Not Transform Mouse Somatic Cells But Triggers a Transcriptional Response that Classifies Human Cancers

Abstract

KRAS mutations are present at a high frequency in human cancers. The development of therapies targeting mutated KRAS requires cellular and animal preclinical models. We exploited adeno-associated virus-mediated homologous recombination to insert the Kras G12D allele in the genome of mouse somatic cells. Heterozygous mutant cells displayed a constitutively active Kras protein, marked morphologic changes, increased proliferation and motility but were not transformed. On the contrary, mouse cells in which we overexpressed the corresponding Kras cDNA were readily transformed. The levels of Kras activation in knock-in cells were comparable with those present in human cancer cells carrying the corresponding mutation. Kras-mutated cells were compared with their wild-type counterparts by gene expression profiling, leading to the definition of a ''mutated Kras-KI signature'' of 345 genes. This signature was capable of classifying mouse and human cancers according to their KRAS mutational status, with an accuracy similar to or better than published Ras signatures. The isogenic cells that we have developed recapitulate the oncogenic activation of KRAS occurring in cancer and represent new models for studying Kras-mediated transformation. Our results have implications for the identification of human tumors in which the oncogenic KRAS transcriptional response is activated and suggest new strategies to build mouse models of tumor progression. [Cancer Res 2007;67(18):8468-76]

Identification of Mutant K-Ras-dependent Phenotypes Using a Panel of Isogenic Cell Lines

“…There have previously been several publications using "Ras gene signatures" to classify human tumors. Sweet- (37) used single copy K-Ras knock-in in mouse liver progenitor cells to derive 149 genes that were up-regulated upon this condition. Mutant K-Ras results in highly divergent consequences in different tissues and environments, as exemplified by the fact that only a single gene (DUSP6) is in common among these three sets of signatures.…”

Replacement of normal with mutant alleles in the genome of normal human cells unveils mutation-specific drug responses

“…The lentiviral vector expressing BRAF V600E was a kind gift of of Dr María S. Soengas (Ann Arbor, MI). The procedure to obtain the lentivirus expressing the KRAS G13D mutation has been described elsewhere (2).…”

“…While such systems in which mutated oncogenes are ectopically expressed under exogenous promoters have been instrumental in dissecting their oncogenic properties, they have also led to controversial results. For example, studies focused on oncogene-mediated transformation and senescence have generated conflicting data depending on whether the cancer alleles were ectopically expressed or permanently introduced in the genome of mouse or human cells (2)(3)(4)(5). To address the limitation of current models, we have used targeted homologous recombination to introduce (knock-in, KI) a panel of cancer alleles in human somatic cells.…”

Wilms tumor 1 (WT1) regulates KRAS-driven oncogenesis and senescence in mouse and human models

“…Previous work has identified KRAS-specific gene expression signatures using mouse, zebrafish, or human model systems (8)(9)(10)(11). Gene expression signatures are useful tools for identifying the complex signaling networks that drive diverse cellular processes in normal physiology and disease.…”