Genome-wide retroviral insertional tagging of genes involved in cancer in Cdkn2a-deficient mice

Abstract

We have used large-scale insertional mutagenesis to identify functional landmarks relevant to cancer in the recently completed mouse genome sequence. We infected Cdkn2a(-/-) mice with Moloney murine leukemia virus (MoMuLV) to screen for loci that can participate in tumorigenesis in collaboration with loss of the Cdkn2a-encoded tumor suppressors p16INK4a and p19ARF. Insertional mutagenesis by the latent retrovirus was synergistic with loss of Cdkn2a expression, as indicated by a marked acceleration in the development of both myeloid and lymphoid tumors. We isolated 747 unique sequences flanking retroviral integration sites and mapped them against the mouse genome sequence databases from Celera and Ensembl. In addition to 17 insertions targeting gene loci known to be cancer-related, we identified a total of 37 new common insertion sites (CISs), of which 8 encode components of signaling pathways that are involved in cancer. The effectiveness of large-scale insertional mutagenesis in a sensitized genetic background is demonstrated by the preference for activation of MAP kinase signaling, collaborating with Cdkn2a loss in generating the lymphoid and myeloid tumors. Collectively, our results show that large-scale retroviral insertional mutagenesis in genetically predisposed mice is useful both as a system for identifying genes underlying cancer and as a genetic framework for the assignment of such genes to specific oncogenic pathways.

A direct link between expression of urokinase plasminogen activator receptor, growth rate and oncogenic transformation in mouse embryonic fibroblasts

“…Finally, as uPAR overexpression may participate in tumorigenesis in the absence of the Ink4a gene products (Lund et al, 2002) we analysed p19 À/À MEFs, lacking one gene product of this locus, and found that uPAR overexpression failed to decrease growth (Figure 1e), even though it did not stimulate it like Ras V12 . Thus, uPAR can affect cell proliferation only in a p19-positive background.…”

“…Thus, the effect of uPAR on cell proliferation may change depending on which proto-oncogenes and/or tumor suppressor genes are mutated in the cell. Indeed, uPAR is detected as a potential cooperating oncogene in Ink4a Ko mice (Lund et al, 2002). Ink4a Ko mice do not express p16 or p19ARF and are deficient in cell growth control (Serrano et al, 1996).…”

“…Second, uPA and uPAR antagonists prevent not only invasiveness and metastasis dissemination but also tumor growth (Crowley et al, 1993;Min et al, 1996;Lakka et al, 2001;Ploug et al, 2001). Finally, a genetic screen in Ink4a À/À mice identified uPAR as a potential cooperating oncogene (Lund et al, 2002). As the Ink4a locus controls both p53 and Rb pathways through the p19 and p16 gene products (Sharpless and DePinho, 1999), these data suggest that uPAR overexpression may participate in tumorigenesis in the absence of cell cycle control.…”

Mutations in the NF-κB signaling pathway: implications for human disease

“…Third, mice with a knock out of nfkb2 sequences encoding the C-terminal sequences of p100 have increased numbers of T lymphocytes, enlarged lymph nodes and gastric hyperplasia (Ishikawa et al, 1997). Fourth, in two large-scale retroviral integration screens for mouse lymphoma genes, retroviral integrations in 3 0 coding regions of nfkb2 (and nfkb1) were detected (Lund et al, 2002;Suzuki et al, 2002b).…”

Syntenin-mediated regulation of Sox4 proteasomal degradation modulates transcriptional output

“…In addition, Sox4 appears to have a dominant role in conferring oncogenic and metastatic transformation (Rhodes et al, 2004). High levels of Sox4 mRNA expression have been observed in a large number of human tumors including breast, lung, brain, prostate and ovarian cancer, and the Sox4 gene locus has been repeatedly found to be targeted by tumor-promoting retroviral integration in mice (Lund et al, 2002;Suzuki et al, 2002;Shin et al, 2004). Together, these studies support the inclusion of Sox4 as one of the 64 genes that constitute a general cancer signature (Rhodes et al, 2004).…”