Project description:Lck-MyrAkt2 mice develop spontaneous thymic lymphomas at approximately 100-200 days of age, driven in part by a consitutatively-active AKT (due to myristoylation). mTOR Knock Down mice were crossed with Lck-MyrAkt postive mice to model the affects of decreasing mTOR activity on tumors with an activated PI3K/AKT/MTOR pathway. Lck-Akt/mTOR KD mice had prolonged survival compared to the Lck-Akt/mTOR WT mice. We used microarrays to compare the transcriptome in thymic lymphomas between Lck-Akt positive, mTOR WT and Lck-Akt positive, mTOR KD mice. Four thymic lymphomas from Lck-Akt/mTOR WT mice were compared to three thymic lymphomas from Lck-Akt/mTOR KD mice.
Project description:We used gene transcript profiling to gain a deeper understanding of the role of FBXW7 in tumor development and to determine the influence of mTOR inhibition by rapamycin on tumor transcriptome and biological functions. In comparison to tumors from p53 single heterozygous (p53+/-) mice, we find that tumors from Fbxw7/p53 double heterozygous (Fbxw7+/-p53+/-) mice show significant deregulation of cholesterol metabolic processes independent of rapamycin treatment, while cell cycle related genes were upregulated in tumors from placebo treated Fbxw7+/-p53+/- mice, but not in tumors from rapamycin treated Fbxw7+/-p53+/- mice. On the other hand, tumors from rapamycin treated Fbxw7+/-p53+/- mice were enriched for genes involved in the integrated stress response, an adaptive mechanism to survive in stressful environments. p53+/â and p53+/âFbxw7+/â mice were generated by crossing p53-/- mice with Fbxw7+/- mice. At 5 weeks of age, mice were exposed whole-body to a single dose of 4 Gy X-ray irradiation. Mice were divided randomly into two groups and treated with rapamycin or placebo. RNA was isolated from thymic lymphomas.
Project description:Inactivation of Pten occurs by multiple mechanisms including epigenetic silencing, point mutations, insertion, and deletion, which are tissue dependent. Although frequent loss of heterozygosity around Pten locus and plausible involvement of epigenetic silencing have been reported in radiation-induced thymic lymphomas, the frequency of Pten inactivation and the spectrum of causal aberrations have not yet been extensively characterized. Here, we assessed the principal mode of inactivation by comprehensively analyzing expression and alterations of Pten gene in 23 radiation-induced thymic lymphomas developed in B6C3F1 mice. We found no evidence for methylation-associated silencing of Pten gene. Instead, we found complex structural abnormalities in 8 lymphomas (35%) that included missense and nonsense mutations, 1- and 3-bp insertions, and focal deletions. Sequencing of deletion breakpoints suggested that illegitimate V(D)J recombination and microhomology-mediated rearrangement were responsible for the focal deletions. Seven out of these 8 lymphomas had biallelic alterations, and 4 of them did not express any Pten protein. These aberrations of Pten were well coincided with downstream Akt phosphorylation on Ser473. In conclusion, Pten inactivation, which is frequently biallelic and is caused by a variety of structural abnormalities but not by epigenetic silencing, is involved in radiation-induced lymphomagenesis. Three thymic lymphomas were analyzed by array-CGH method.
Project description:High linear energy transfer (LET) radiation is thought to induce highly complex DNA damage compared with photon radiation such as X-rays, suggesting a characteristic mechanism for the development of cancers associated with high-LET radiation exposure. However, few studies have investigated the carcinogenic mechanisms that are dependent on radiation quality or LET. This study analyzed mutations and gene expression in thymic lymphomas induced by high-LET carbon-ion irradiation to identify characteristic genetic alterations. The results revealed that thymic lymphomas arising after four-fractionated high-LET carbon-ion irradiation frequently exhibited loss of heterozygosity in the region containing the thymic lymphoma–associated gene Ikzf1 on chromosome 11 owing to extensive genomic deletions in the paternal allele. Nevertheless, for carbon ion–induced thymic lymphomas, those with only loss of heterozygosity without Ikzf1 alterations were observed at a relatively high frequency. Comprehensive RNA sequencing and reverse-transcription PCR analysis of neighboring genes of Ikzf1 revealed highly upregulated expression of Grb10, an imprinted gene that is barely expressed in the normal thymus. In thymic lymphomas expressing Grb10, enhanced interferon signaling and Pten mutations were suggested to promote cell proliferation and survival. These results suggest that extensive genomic deletions caused by high-LET carbon-ion irradiation may contribute to carcinogenesis by altering the expression of multiple genes located in the deleted region.
Project description:Following exposure to either high LET (linear energy transfer) or gamma radiation, the most frequently observed malignancies in both Trp53?P and Trp53+/- mice are mammary and skin tumours, and thymic lymphomas. To gain further insights into the landscape of radiation-induced tumours the overall frequency and size of insertions and deletions in expressed genes was assessed by RNA-Seq. RNA was extracted from 12 mammary tumours of a range of histologies that had been induced using 50cGy of either high- or low- LET. 5 normal mammary tissue controls were also analyzed. A further 8 thymic lymphomas induced by gamma or Fe-ion radiation exposure were also sequenced as part of this study.This data is part of a pre-publication release. For information on the proper use of pre-publication data shared by the Wellcome Trust Sanger Institute (including details of any publication moratoria), please see http://www.sanger.ac.uk/datasharing/
Project description:Inactivation of Pten occurs by multiple mechanisms including epigenetic silencing, point mutations, insertion, and deletion, which are tissue dependent. Although frequent loss of heterozygosity around Pten locus and plausible involvement of epigenetic silencing have been reported in radiation-induced thymic lymphomas, the frequency of Pten inactivation and the spectrum of causal aberrations have not yet been extensively characterized. Here, we assessed the principal mode of inactivation by comprehensively analyzing expression and alterations of Pten gene in 23 radiation-induced thymic lymphomas developed in B6C3F1 mice. We found no evidence for methylation-associated silencing of Pten gene. Instead, we found complex structural abnormalities in 8 lymphomas (35%) that included missense and nonsense mutations, 1- and 3-bp insertions, and focal deletions. Sequencing of deletion breakpoints suggested that illegitimate V(D)J recombination and microhomology-mediated rearrangement were responsible for the focal deletions. Seven out of these 8 lymphomas had biallelic alterations, and 4 of them did not express any Pten protein. These aberrations of Pten were well coincided with downstream Akt phosphorylation on Ser473. In conclusion, Pten inactivation, which is frequently biallelic and is caused by a variety of structural abnormalities but not by epigenetic silencing, is involved in radiation-induced lymphomagenesis.
Project description:PRDM family members are sequence-specific transcriptional regulators involved in cell identity and fate determination and are often dysregulated in cancer. The PRDM15 gene is of particular interest, given its relatively low expression in adult tissues and its overexpression in follicular lymphomas (FL). Despite its well characterized role in stem cell biology and during early development, the role of PRDM15 in cancer remains obscure. Herein, we demonstrate that while PRDM15 is largely dispensable for mouse adult somatic cell homeostasis in vivo, it plays an essential role in B cell lymphomagenesis. Mechanistically, PRDM15 regulates a transcriptional program pertinent to the activity of the PI3K/AKT/mTOR pathway and glycolysis in B cell lymphomas. Abrogation of PRDM15 induces a metabolic crisis and selective death of lymphoma cells. Collectively, our data demonstrate that PRDM15 fuels the metabolic requirement of B cell lymphomas and validate it as an attractive and previously unrecognized target in oncology.
Project description:Dnmt3b is a DNA methytransferase which is an enzyme that methylated genomic DNA which contributes to genomic stability and transcriptional regulation. We genetically inactivated Dnmt3b in the hematopoeitic compartment in the context of MYC overexpression and analysed the resulting thymic lymphomas.
Project description:Dnmt3b is a DNA methytransferase which is an enzyme that methylated genomic DNA which contributes to genomic stability and transcriptional regulation. We genetically inactivated Dnmt3b in the hematopoeitic compartment in the context of MYC overexpression and analysed the resulting thymic lymphomas.