Collier, Lara S.

The SB transposon system has been used as an insertional mutagen to study tumor development. This novel system involves the mobilization of a transposon (e.g. T2/onc) by a tranposase source (e.g. Rosa26‐SB11) in transgenic mice. We serially sectioned FFPE brains from 154 mice and identified 15 infiltrating gliomas that morphologically resembled small cell astrocytomas, as well as one PNET. The gliomas involved cerebral hemispheres (n=8) or posterior fossa (n=7). The tumors demonstrated remarkable infiltration of underlying brain parenchyma with secondary structuring (i.e. subpial, perivascular and perineuronal aggregation); round to oval cells with irregular nuclear contours, scant cell processes and variable mitotic activity (median 4/10 hpf, range 2–9); and pseudopalisading necrosis (n=5). Endothelial proliferation and calcification were absent. Immunohistochemical stains for GFAP and S100 strongly labeled reactive astrocytes, but minimal immunoreactivity was also seen in occasional small tumor cells. In 14 of 15 mice the genotype was T2/onc/SB11 positive; three mice were p19 Arf +/− , one mouse was p19 Arf −/− and one was Blm −/− . The PNET filling the third ventricle was identified in a control mouse homozygous mutant for p19 Arf , but transgenic only for the T2/Onc concatomer. This tumor, in contrast to the gliomas, demonstrated uniform synaptophysin staining and did not label with GFAP or S100.These results demonstrate that the SB transposon system is a valid model to study gliomagenesis in mice.

Abstract The Sleeping Beauty (SB) transposon system has been used as an insertional mutagenesis tool to identify novel cancer genes. To identify glioma-associated genes, we evaluated tumor formation in the brain tissue from 117 transgenic mice that had undergone constitutive SB-mediated transposition. Upon analysis, 21 samples (18%) contained neoplastic tissue with features of high-grade astrocytomas. These tumors expressed glial markers and were histologically similar to human glioma. Genomic DNA from SB-induced astrocytoma tissue was extracted and transposon insertion sites were identified. Insertions in the growth factor gene Csf1 were found in 13 of the 21 tumors (62%), clustered in introns 5 and 8. Using reverse transcription-PCR, we documented increased Csf1 RNAs in tumor versus adjacent normal tissue, with the identification of transposon-terminated Csf1 mRNAs in astrocytomas with SB insertions in intron 8. Analysis of human glioblastomas revealed increased levels of Csf1 RNA and protein. Together, these results indicate that SB-insertional mutagenesis can identify high-grade astrocytoma-associated genes and they imply an important role for CSF1 in the development of these tumors. Cancer Res; 70(9); 3557–65. ©2010 AACR.

Abstract The Sleeping Beauty (SB) transposon system has been used as a somatic mutagen to identify candidate cancer genes. In previous studies, efficient leukemia/lymphoma formation on an otherwise wild-type genetic background occurred in mice undergoing whole-body mobilization of transposons, but was accompanied by high levels of embryonic lethality. To explore the utility of SB for large-scale cancer gene discovery projects, we have generated mice that carry combinations of different transposon and transposase transgenes. We have identified a transposon/transposase combination that promotes highly penetrant leukemia/lymphoma formation on an otherwise wild-type genetic background, yet does not cause embryonic lethality. Infiltrating gliomas also occurred at lower penetrance in these mice. SB-induced or accelerated tumors do not harbor large numbers of chromosomal amplifications or deletions, indicating that transposon mobilization likely promotes tumor formation by insertional mutagenesis of cancer genes, and not by promoting wide-scale genomic instability. Cloning of transposon insertions from lymphomas/leukemias identified common insertion sites at known and candidate novel cancer genes. These data indicate that a high mutagenesis rate can be achieved using SB without high levels of embryonic lethality or genomic instability. Furthermore, the SB system could be used to identify new genes involved in lymphomagenesis/leukemogenesis. [Cancer Res 2009;69(21):8429–37]