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Supplementary Figure S1. Crebbp deficiency results in accelerated germinal center derived B-cell lymphoma development in mice. Supplementary Figure S2. Ep300 deficiency results in accelerated germinal center derived B-cell lymphoma development in mice. Supplementary Figure S3. Western blots showing the knockdown efficiency of shRNAs against human CREBBP in human DLBCL MD901 cells and H3K27ac reduction in MD901 cells transduced with shRNAs against human CREBBP, and stacked bar plot showing the genome-wide distribution of CREBBP ChIPseq peaks in OCI-Ly7 cells. Supplementary Figure S4. GSEA enrichment plots showing correlation of genes with >25% loss of H3K27ac at enhancers in VavP-Bcl2/shCrebbp tumours with ranked expression change between B220+ lymphoma cells from VavP-Bcl2/shCrebbp tumours (n=3) and VavP-Bcl2/GFP tumours (n=3). NES, normalized enrichment score. Supplementary Figure S5. Venn diagram showing the overlap of H3K4me2+H3K4me3-H3K27ac+ (active enhancer) peaks between human tonsilar IgD+ Naïve B cells (NBs) and CD77+ germinal center B cells (GCBs). Supplementary Figure S6. Pathway analysis of down-regulated genes in top 500 differentially expressed genes between murine VavP-Bcl2/shCrebbp tumours and VavP-Bcl2/GFP tumours (left panel), or between CREBBP knockdown and scramble control human DLBLC MD901 cells (right panel). Supplementary Figure S7. Pathway analysis of genes with > 25% reduction of H3K27ac reads at promoters in murine VavP-Bcl2/shCrebbp tumors. Supplementary Figure S8. UCSC read-density tracks of normalized BCL6 (purple) and SMRT (orange) ChIP-seq reads in human tonsilar GCBs, H3K27ac ChIP-seq reads in human tonsilar NBCs (red) and GCBs (blue), and H3K27ac ChIP-seq in control scramble (Scr, green) and CREBBP KD (shCREBBP, turquoise) MD901 cells at the human CIITA and CD74 loci. BCL6 and SMRT peaks determined by MACS2 are indicated by grey bars under the read density track. Supplementary Figure S9. Stacked bar plots showing the frequencies of CREBBP somatic mutations in two cohorts of FL and one cohort of DLBCL primary patient samples. Supplementary Figure S10. The proportions of the Up (up-regulated) and Down (down-regulated) genes in the top 100, 500, and 1000 most differentially expressed genes of the respective cohorts profiled in Figure 3. Supplementary Figure S11. Representative flow cytometry analysis for FAS and GL7 of whole spleens from NS-DAD wild type (wt) or mutant (mut) animals. Supplementary Figure S12. Western blots showing the knockdown efficiency of shRNAs against human HDAC3 in DLBCL cell lines OCI-Ly7 and MD901 120 hr after induction of shRNA expression. The amount of HDAC3 was quantified by using ImageJ, and the ratio of shRNA knockdown samples and the control shLuc sample was indicated below the blots. Supplementary Figure S13. BCL6 and HDAC3 ChIP-qPCR at enhancers of CD74 or HLA-DOA (primer sequences please check Supplementary Table S12) in OCI-Ly1 cells transfected with either non-target siRNA (siNT) or BCL6 siRNA (siBCL6). Supplementary Figure S14. Quantification of HLA-DR measured by flow cytometry in shCREBBP or scramble transduced lymphoma cells MD901 and OCI-Ly18 in a second biological replicate experiment.

A list of CREBBP mutations in cohorts 1 and 2.

Cellular senescence is emerging as an important in vivo anticancer response elicited by multiple stresses, including currently used chemotherapeutic drugs. Nutlin-3a is a recently discovered small-molecule antagonist of the p53-destabilizing protein murine double minute-2 (MDM2) that induces cell cycle arrest and apoptosis in cancer cells with functional p53. Here, we report that nutlin-3a induces cellular senescence in murine primary fibroblasts, oncogenically transformed fibroblasts, and fibrosarcoma cell lines. No evidence of drug-induced apoptosis was observed in any case. Nutlin-induced senescence was strictly dependent on the presence of functional p53 as revealed by the fact that cells lacking p53 were completely insensitive to the drug, whereas cells lacking the tumor suppressor alternative reading frame product of the CDKN2A locus underwent irreversible cell cycle arrest. Interestingly, irreversibility was achieved in neoplastic cells faster than in their corresponding parental primary cells, suggesting that nutlin-3a and oncogenic signaling cooperate in activating p53. Our current results suggest that senescence could be a major cellular outcome of cancer therapy by antagonists of the p53-MDM2 interaction, such as nutlin-3a. [Cancer Res 2007;67(15):7350–7]

Supplementary Figure 1 from Induction of p53-Dependent Senescence by the MDM2 Antagonist Nutlin-3a in Mouse Cells of Fibroblast Origin

SUMMARY B lymphocytes are exquisitely sensitive to fluctuations in nutrient signaling by the Rag GTPases, and 15% of follicular lymphomas (FLs) harbor activating mutations in RRAGC. Hence, a potential therapeutic approach against malignant B cells is to inhibit Rag GTPase signaling, but because such inhibitors are still to be developed, efficacy and safety remain unknown. We generated knockin mice expressing a hypomorphic variant of RagC (Q119L); RagCQ119L/+ mice are viable and show attenuated nutrient signaling. B lymphocyte activation is cell-intrinsically impaired in RagCQ119L/+ mice, which also show significant suppression of genetically induced lymphomagenesis and autoimmunity. Surprisingly, no overt systemic trade-offs or phenotypic alterations caused by partial suppression of nutrient signaling are seen in other organs, and RagCQ119L/+ mice show normal longevity and normal age-dependent health decline. These results support the efficacy and safety of moderate inhibition of nutrient signaling against pathological B cells., Graphical abstract, In brief By generating knockin mice expressing a hypomorphic variant of the RagC GTPase, Ortega-Molina et al. show that partial inhibition of nutrient signaling may be a safe and efficacious approach against pathogenic B cells and B cell lymphomas.

Cancer cells adapt their metabolic activities to support growth and proliferation. However, increased activity of metabolic enzymes is not usually considered an initiating event in the malignant process. Here, we investigate the possible role of the enzyme serine hydroxymethyltransferase-2 (SHMT2) in lymphoma initiation. SHMT2 localizes to the most frequent region of copy number gains at chromosome 12q14.1 in lymphoma. Elevated expression of SHMT2 cooperates with BCL2 in lymphoma development; loss or inhibition of SHMT2 impairs lymphoma cell survival. SHMT2 catalyzes the conversion of serine to glycine and produces an activated one-carbon unit that can be used to support S-adenosyl methionine synthesis. SHMT2 induces changes in DNA and histone methylation patterns leading to promoter silencing of previously uncharacterized mutational genes, such as SASH1 and PTPRM. Together, our findings reveal that amplification of SHMT2 in cooperation with BCL2 is sufficient in the initiation of lymphomagenesis through epigenetic tumor suppressor silencing. Parsa et al. report a mechanism of lymphoma initiation involving cooperation of BCL2 and increased activity of the metabolic enzyme SHMT2, which imparts changes in DNA and histone methylation.

The mechanistic target of rapamycin complex 1 (mTORC1) integrates cellular nutrient signaling and hormonal cues to control metabolism. We have previously shown that constitutive nutrient signaling to mTORC1 by means of genetic activation of RagA (expression of GTP-locked RagA, or RagAGTP) in mice resulted in a fatal energetic crisis at birth. Herein, we rescue neonatal lethality in RagAGTP mice and find morphometric and metabolic alterations that span glucose, lipid, ketone, bile acid and amino acid homeostasis in adults, and a median lifespan of nine months. Proteomic and metabolomic analyses of livers from RagAGTP mice reveal a failed metabolic adaptation to fasting due to a global impairment in PPARα transcriptional program. These metabolic defects are partially recapitulated by restricting activation of RagA to hepatocytes, and revert by pharmacological inhibition of mTORC1. Constitutive hepatic nutrient signaling does not cause hepatocellular damage and carcinomas, unlike genetic activation of growth factor signaling upstream of mTORC1. In summary, RagA signaling dictates dynamic responses to feeding-fasting cycles to tune metabolism so as to match the nutritional state., The mechanistic target of rapamycin complex 1 (mTORC1) integrates nutrient and hormonal signals to control metabolism. Here the authors investigate the effects of constitutive nutrient signaling through genetic activation of RagA in adult mice and show that constitutive nutrient signaling regulates the response to feeding-fasting cycles and does not drive liver cancer.

During the humoral response, B cells undergo a sudden anabolic shift that requires high cellular nutrient levels to sustain the subsequent proliferative burst. Follicular lymphoma (FL) originates from B cells that have participated in the humoral response, and 15% of FL samples have selected for point, activating mutations in RRAGC, a member of the Rag GTPase family that controls the activation of the mechanistic target of rapamycin complex 1 downstream of the sensing of cellular nutrients. S74C and T89N, two of the most frequent activating single-amino acid changes in RRAGC, when targeted to the endogenous Rragc locus in mice, confer only a partial insensitivity to nutrient deprivation but strongly exacerbate B-cell responses and accelerate lymphomagenesis. Surprisingly, this moderate increase in nutrient signaling affected the interaction of B cells with the cellular microenvironment, synergizing their effects on mTORC1 activation with paracrine cues from the supportive T-cell microenvironment that activate B cells via the PI3K–Akt–mTORC1 axis. Hence, Rragc mutations sustain induced germinal centers and murine and human FL in the presence of decreased T-cell help. From a therapeutic standpoint, Rragc mutations impose a selective vulnerability to pharmacologic inhibition of mTORC1. Our results support a model in which activating mutations in the nutrient signaling pathway foster lymphomagenesis by corrupting a nutrient-dependent control over paracrine signals from the T-cell microenvironment. While pharmacologic inhibition of mTORC1 with rapamycin yielded exciting preclinical responses in murine lymphomas with activating mutations in Rragc, targeting the nutrient signaling cascade itself, instead of using such allosteric, partial inhibition of mTOR, may constitute a more efficacious intervention. Because nutrient signaling inhibitors are still in development phase, their efficacy and safety remain unproven. Previous genetic approaches to investigate the consequences of inhibition of Rag GTPase signaling relied on deletion of the Rags in mice and led to severe phenotypes and death. Incomplete inhibition of nutrient signaling, an approach that would mirror more closely the effect of small molecules, has not been pursued to support both their efficacy and safety. We have generated knock-in mice endogenously expressing a point-mutant form of RagC (Q119L) that partially suppresses nutrient signaling. RagCQ119L/Q119L mice are not viable, but RagCQ119L/+ mice show minimal phenotypic alterations with partially decreased nutrient signaling. While B-cell development was unaffected, B-cell activation and the humoral response were impaired in RagCQ119L/+ in a B cell-intrinsic manner. When bred to the FL- and autoimmunity-prone strain VavP-Bcl2, RagCQ119L/+ mice were protected against development of both FL and autoimmunity. No obvious systemic tradeoff for the suppression of nutrient signaling seems to occur, because RagCQ119L/+ mice show normal physiology and longevity with a similar age-dependent health decline. Altogether, our work supports the oncogenicity of activating mutations in components of the nutrient signaling pathway, such as RagC, and both the efficacy and safety of a moderate inhibition of nutrient signaling against pathologic B cells without detrimental systemic effects. Citation Format: Ana Ortega-Molina, Cristina Lebrero-Fernández, Nerea Deleyto-Seldas, Alba Sanz, Alejo Efeyan. Oncogenic Rag GTPase signaling links cellular nutrients with the FL microenvironment [abstract]. In: Proceedings of the AACR Virtual Meeting: Advances in Malignant Lymphoma; 2020 Aug 17-19. Philadelphia (PA): AACR; Blood Cancer Discov 2020;1(3_Suppl):Abstract nr IA13.

Dyshomeostasis of amyloid-β peptide (Aβ) is responsible for synaptic malfunctions leading to cognitive deficits ranging from mild impairment to full-blown dementia in Alzheimer's disease. Aβ appears to skew synaptic plasticity events toward depression. We found that inhibition of PTEN, a lipid phosphatase that is essential to long-term depression, rescued normal synaptic function and cognition in cellular and animal models of Alzheimer's disease. Conversely, transgenic mice that overexpressed PTEN displayed synaptic depression that mimicked and occluded Aβ-induced depression. Mechanistically, Aβ triggers a PDZ-dependent recruitment of PTEN into the postsynaptic compartment. Using a PTEN knock-in mouse lacking the PDZ motif, and a cell-permeable interfering peptide, we found that this mechanism is crucial for Aβ-induced synaptic toxicity and cognitive dysfunction. Our results provide fundamental information on the molecular mechanisms of Aβ-induced synaptic malfunction and may offer new mechanism-based therapeutic targets to counteract downstream Aβ signaling.

Somatic mutations in CREBBP occur frequently in B-cell lymphoma. Here, we show that loss of CREBBP facilitates the development of germinal center (GC)–derived lymphomas in mice. In both human and murine lymphomas, CREBBP loss-of-function resulted in focal depletion of enhancer H3K27 acetylation and aberrant transcriptional silencing of genes that regulate B-cell signaling and immune responses, including class II MHC. Mechanistically, CREBBP-regulated enhancers are counter-regulated by the BCL6 transcriptional repressor in a complex with SMRT and HDAC3, which we found to bind extensively to MHC class II loci. HDAC3 loss-of-function rescued repression of these enhancers and corresponding genes, including MHC class II, and more profoundly suppressed CREBBP-mutant lymphomas in vitro and in vivo. Hence, CREBBP loss-of-function contributes to lymphomagenesis by enabling unopposed suppression of enhancers by BCL6/SMRT/HDAC3 complexes, suggesting HDAC3-targeted therapy as a precision approach for CREBBP-mutant lymphomas. Significance: Our findings establish the tumor suppressor function of CREBBP in GC lymphomas in which CREBBP mutations disable acetylation and result in unopposed deacetylation by BCL6/SMRT/HDAC3 complexes at enhancers of B-cell signaling and immune response genes. Hence, inhibition of HDAC3 can restore the enhancer histone acetylation and may serve as a targeted therapy for CREBBP-mutant lymphomas. Cancer Discov; 7(1); 38–53. ©2016 AACR. See related commentary by Höpken, p. 14. This article is highlighted in the In This Issue feature, p. 1

13 páginas, 7 figuras, 7 figuras suplementarias, 7 tablas suplementarias.-- et al., Aging in worms and flies is regulated by the PI3K/Akt/Foxo pathway. Here we extend this paradigm to mammals. Ptentg mice carrying additional genomic copies of Pten are protected from cancer and present a significant extension of life span that is independent of their lower cancer incidence. Interestingly, Ptentg mice have an increased energy expenditure and protection from metabolic pathologies. The brown adipose tissue (BAT) of Ptentg mice is hyperactive and presents high levels of the uncoupling protein Ucp1, which we show is a target of Foxo1. Importantly, a synthetic PI3K inhibitor also increases energy expenditure and hyperactivates the BAT in mice. These effects can be recapitulated in isolated brown adipocytes and, moreover, implants of Ptentg fibroblasts programmed with Prdm16 and Cebpβ form subcutaneous brown adipose pads more efficiently than wild-type fibroblasts. These observations uncover a role of Pten in promoting energy expenditure, thus decreasing nutrient storage and its associated damage, Work in the laboratory of A.M.V. was funded by grant SAF2009-08114 and by the CIBERDEM (ISCIII), and work in the laboratory of E. Rial was funded by grants SAF2010-20256 and Consolider-Ingenio CSD2007-00020. A.O.-M. was recipient of a predoctoral contract of the Regional Government of Madrid. E.L.-G. was recipient of a predoctoral contract from the Spanish Ministry of Education. M.M.G.-B. was supported by the “Ramon y Cajal” program of the Spanish Ministry of Science and Innovation.

Cellular senescence is emerging as an important in vivo anticancer response elicited by multiple stresses, including currently used chemotherapeutic drugs. Nutlin-3a is a recently discovered small-molecule antagonist of the p53-destabilizing protein murine double minute-2 (MDM2) that induces cell cycle arrest and apoptosis in cancer cells with functional p53. Here, we report that nutlin-3a induces cellular senescence in murine primary fibroblasts, oncogenically transformed fibroblasts, and fibrosarcoma cell lines. No evidence of drug-induced apoptosis was observed in any case. Nutlin-induced senescence was strictly dependent on the presence of functional p53 as revealed by the fact that cells lacking p53 were completely insensitive to the drug, whereas cells lacking the tumor suppressor alternative reading frame product of the CDKN2A locus underwent irreversible cell cycle arrest. Interestingly, irreversibility was achieved in neoplastic cells faster than in their corresponding parental primary cells, suggesting that nutlin-3a and oncogenic signaling cooperate in activating p53. Our current results suggest that senescence could be a major cellular outcome of cancer therapy by antagonists of the p53-MDM2 interaction, such as nutlin-3a. [Cancer Res 2007;67(15):7350–7]

UNLABELLED: Abstract Aims: A recent study conducted in mice reported that liver-specific knockout of tumor suppressor Pten augments nuclear factor (erythroid-derived 2)-like 2 (NRF2) transcriptional activity. Here, we further investigated how phosphatase and tensin homolog deleted on chromosome 10 (PTEN) controls NRF2 and the relevance of this pathway in human carcin ogenesis.RESULTS: Drug and genetic targeting to PTEN and phosphoproteomics approaches indicated that PTEN leads to glycogen synthase kinase-3 (GSK-3)-mediated phosphorylation of NRF2 at residues Ser(335) and Ser(338) and subsequent beta-transducin repeat containing protein (β-TrCP)-dependent but Kelch-like ECH-associated protein 1 (KEAP1)-independent degradation. Rescue experiments in PTEN-deficient cells and xerographs in athymic mice indicated that loss of PTEN leads to increased NRF2 signature which provides a proliferating and tumorigenic advantage. Tissue microarrays from endometrioid carcinomas showed that 80% of PTEN-negative tumors expressed high levels of NRF2 or its target heme oxygenase-1 (HO-1).INNOVATION: These results uncover a new mechanism of oncogenic activation of NRF2 by loss of its negative regulation by PTEN/GSK-3/β-TrCP that may be relevant to a large number of tumors, including endometrioid carcinomas.CONCLUSION: Increased activity of NRF2 due to loss of PTEN is instrumental in human carcinogenesis and represents a novel therapeutic target. Antioxid. Redox Signal. 21, 2498-2514.

SummaryGenetic inhibition of PI3K signaling increases energy expenditure, protects from obesity and metabolic syndrome, and extends longevity. Here, we show that two pharmacological inhibitors of PI3K, CNIO-PI3Ki and GDC-0941, decrease the adiposity of obese mice without affecting their lean mass. Long-term treatment of obese mice with low doses of CNIO-PI3Ki reduces body weight until reaching a balance that is stable for months as long as the treatment continues. CNIO-PI3Ki treatment also ameliorates liver steatosis and decreases glucose serum levels. The above observations have been recapitulated in independent laboratories and using different oral formulations of CNIO-PI3Ki. Finally, daily oral treatment of obese rhesus monkeys for 3 months with low doses of CNIO-PI3Ki decreased their adiposity and lowered their serum glucose levels, in the absence of detectable toxicities. Therefore, pharmacological inhibition of PI3K is an effective and safe anti-obesity intervention that could reverse the negative effects of metabolic syndrome in humans.

Somatic mutations in CREBBP occur frequently in germinal center derived lymphomas such as DLBCL and FL. However whether or how these mutations might contribute to lymphomagenesis is still largely unknown. Most CREBBP mutations are predicted to result in loss of function since they target the histone acetyltransferase (HAT) domain or give rise to premature stop codon prior to the HAT domain. Here, we show that Crebbp shRNA knockdown (KD) accelerated lymphomagenesis in VavP-Bcl2 transgenic mice, a model that recapitulates human GC-derived lymphomas. The median time to lymphoma onset in VavP-Bcl2/CrebbpKD mice was 114 days, significantly shorter than control VavP-Bcl2/GFP mice (193 days, p=0.04). Histopathology revealed that VavP-Bcl2/CrebbpKD lymphomas were more aggressive and widely disseminated than VavP-Bcl2/GFP lymphomas. CREBBP can regulate gene enhancer function through H3K27 acetylation. ChIP-seq in VavP-Bcl2/CrebbpKD lymphoma cells revealed significant reduction of H3K27ac peaks compared to control lymphoma cells (N = 1717, Kolmogorov-Smirnov test, p To better understand mechanism we performed an integrative analysis of CREBBP signatures against databases of B-cell transcription factor and epigenome profiles. This analysis yielded significant enrichment (BH-adjusted p The opposing effects of BCL6/SMRT/HDAC3 and CREBBP on MHC class II could have implications for immune surveillance. Accordingly CREBBP KD induced significant loss of cell surface HLA-DR molecules (p Disclosures Scott: Celgene: Consultancy; Roche: Honoraria; Janssen: Consultancy; BC Cancer Agency: Patents & Royalties: Inventor on a patent licensed to NanoString Technologies. Tam:Millennium Pharmaceuticals, Inc.: Consultancy. Melnick:Janssen: Research Funding.

Recent reports on mice with systemic overexpression of the tumor-suppressor PTEN (phosphatase and tensin homolog) have expanded our understanding of its physiological functions. Pten transgenic mice present increased energy expenditure, decreased adiposity, improved insulin sensitivity upon high-fat feeding or with aging, and extended lifespan. This has led to new mechanistic insights about the role of PTEN in metabolism. Interestingly, PTEN promotes oxidative phosphorylation and decreases glycolysis, thus preventing the metabolic reprogramming characteristic of cancer cells, which might be relevant to PTEN-mediated cancer protection. PTEN also upregulates UCP1 expression in brown adipocytes, which enhances their nutrient burning capacity and decreases adiposity and associated pathologies. The newly discovered effects of PTEN on metabolism open new avenues for exploration relevant to cancer, obesity, diabetes, and aging.

The crucial function of the PTEN tumor suppressor in multiple cellular processes suggests that its activity must be tightly controlled. Both, membrane association and a variety of post-translational modifications, such as acetylation, phosphorylation, and mono- and polyubiquitination, have been reported to regulate PTEN activity. Here, we demonstrated that PTEN is also post-translationally modified by the small ubiquitin-like proteins, small ubiquitin-related modifier 1 (SUMO1) and SUMO2. We identified lysine residue 266 and the major monoubiquitination site 289, both located within the C2 domain required for PTEN membrane association, as SUMO acceptors in PTEN. We demonstrated the existence of a crosstalk between PTEN SUMOylation and ubiquitination, with PTEN-SUMO1 showing a reduced capacity to form covalent interactions with monoubiquitin and accumulation of PTEN-SUMO2 conjugates after inhibition of the proteasome. Moreover, we found that virus infection induces PTEN SUMOylation and favors PTEN localization at the cell membrane. Finally, we demonstrated that SUMOylation contributes to the control of virus infection by PTEN.

Ionizing radiation induces DNA Double-Strand Breaks (DSBs), which activate the ATM/CHEK2/p53 pathway leading to cell cycle arrest and apoptosis through transcription of genes including CDKN1A (p21) and BBC3 (PUMA). This pathway prevents genomic instability and tumorigenesis as demonstrated in heritable syndromes [e.g., Ataxia Telangiectasia (AT); Li-Fraumeni syndrome (LFS)]. Here, a simple assay based on gene expression in peripheral blood to measure accurately ATM/CHEK2/p53 pathway activity is described. The expression of p21, Puma and Sesn2 was determined in blood from mice with different gene copy numbers of Atm, Trp53 (p53), Chek2 or Arf and in human blood and mitogen stimulated T-lymphocyte (MSTL) cultures from AT, AT carriers, LFS patients and controls, both before and after ex vivo ionizing irradiation. Mouse Atm/Chek2/p53 activity was highly dependent on the copy number of each gene except Arf. In human MSTL, an AT case, AT carriers and LFS patients showed responses distinct from healthy donors. The relationship between gene copy number and transcriptional induction upon radiation was linear for p21 and Puma and correlated well with cancer incidence in p53 variant mice. This reliable blood test provides an assay to determine ATM/CHEK2/p53 pathway activity and demonstrates the feasibility of assessing the activity of this essential cancer protection pathway in simple assays. These findings may have implications for the individualized prediction of cancer susceptibility.

Recent studies in human fibroblasts have provided a new general paradigm of tumor suppression according to which oncogenic signaling produces DNA damage and this, in turn, results in ATM/p53-dependent cellular senescence. Here, we have tested this model in a variety of murine experimental systems. Overexpression of oncogenic Ras in murine fibroblasts efficiently induced senescence but this occurred in the absence of detectable DNA damage signaling, thus suggesting a fundamental difference between human and murine cells. Moreover, lung adenomas initiated by endogenous levels of oncogenic K-Ras presented abundant senescent cells, but undetectable DNA damage signaling. Accordingly, K-Ras-driven adenomas were also senescent in Atm-null mice, and the tumorigenic progression of these lesions was only modestly accelerated by Atm-deficiency. Finally, we have examined chemically-induced fibrosarcomas, which possess a persistently activated DNA damage response and are highly sensitive to the activity of p53. We found that the absence of Atm favored genomic instability in the resulting tumors, but did not affect the persistent DNA damage response and did not impair p53-dependent tumor suppression. All together, we conclude that oncogene-induced senescence in mice may occur in the absence of a detectable DNA damage response. Regarding murine Atm, our data suggest that it plays a minor role in oncogene-induced senescence or in p53-dependent tumor suppression, being its tumor suppressive activity probably limited to the maintenance of genomic stability.

Genomic studies have revealed surprising new insights into the genetics of human B-cell lymphomas. Of particular note the lysine-specific methyl transferase KMT2D has emerged as one of the most frequently mutated genes in follicular lymphoma (FL) and in diffuse large B-cell lymphoma (DLBCL). However, the biological consequences of KMT2D mutations in lymphoma are not known. Here we show that KMT2D functions as a bona fide tumor suppressor and promotes lymphoma development in vivo. Integrative analyses of KMT2D function indicate specific and focal effects on H3K4 methylation and gene expression. These include B-cell growth and differentiation signals such as the CD40, JAK/STAT, and B-cell receptor pathways. Moreover, KMT2D targets include frequently mutated tumor suppressor genes such as TNFAIP3/A20, SOCS3, and TNFRSF14/HVEM. In this manner, KMT2D deficiency disrupts the physiological process of B-cell differentiation, facilitates malignant outgrowth, and can impede therapies acting on the CD40 and B-cell receptor pathways. Citation Format: Ana Ortega-Molina, Isaac W. Boss, Andres Canela, Heng Pan, Yanwen Jiang, Chunying Zhao, Man Jiang, Deqing Hu, Ji-Eun Lee, Hua-Tang Chen, Daisuke Ennishi, David W. Scott, Christoffer Hother, Shichong Liu, Xing-Jun Cao, Wayne Tam, Rita Shaknovich, Benjamin A. Garcia, Randy D. Gascoyne, Kai Ge, Ali Shilatifard, Olivier Elemento, Andre Nussenzweig, Ari M. Melnick, Hans-Guido Wendel. Functional characterization of the tumor suppressor lysine-specific methyltransferase KMT2D in lymphoma. [abstract]. In: Proceedings of the AACR Special Conference on Chromatin and Epigenetics in Cancer; Sep 24-27, 2015; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2016;76(2 Suppl):Abstract nr IA18.

Follicular lymphoma (FL) is a common and incurable form indolent B-cell lymphoma. Genomic studies have now catalogued many recurrent mutations in FL. Epigenetic regulators have emerged as the most common targets of somatic point mutations. For example, the histone methyltransferase KMT2D (MLL4/MLL2) is the most frequently mutated gene in FL with reported mutational frequencies of up to 84%. However, the transcriptional and biological consequences of KMT2D loss of function are currently unknown. Using a well-described murine model of FL, we showed that deficiency of KMT2D promotes the initiation of indolent FL in vivo. To explore the mechanism of KMT2D-mediated tumor suppression we used cross species comparisons of gene expression, histone H3K4 methylation marks and KMT2D genomic occupancy. These analyses converge on a relatively small group of conserved target genes. Strikingly, they include bona fide tumor suppressors and regulators of B-cell proliferation (e.g. TNFAIP3/A20, SOCS3, ARID1A, and TNFRSF14). Our results indicate that KMT2D restrains FL development through simultaneous effects on multiple key regulators of B-cell behavior. Note: This abstract was not presented at the meeting. Citation Format: Ana Ortega-Molina, Isaac Boss, Heng Pan, Yanwen Jiang, Deqing Hu, Xin Gao, Rita Shaknovich, Ali Shilatifard, Ari M. Melnick, Hans-Guido Wendel. Characterization of the tumor suppressor function of the lysine-specific methyltransferase KMT2D in follicular lymphoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr LB-064. doi:10.1158/1538-7445.AM2015-LB-064

Follicular lymphoma (FL), a form of non-Hodgkin lymphoma, is the second most common form of B-cell lymphoma and remains incurable in the majority of cases despite recent advances in therapy. Following an indolent phase, 50% of patients suffer disease transformation to an aggressive form of lymphoma (transformed FL; tFL). This dramatic switch in disease behavior typically culminates in rapid deterioration and patient demise. Accordingly, much effort has been focused on understanding the genetics of transformation and has resulted in the identification of key genetic lesions (e.g. MYC activation, loss of p53, cell cycle controls, activation of NFKB (TNFAIp3/A20)). However, exactly how tumor metabolism, which is altered by these genetic lesions, contributes to disease aggressiveness is not known and therefore the metabolic changes that occur upon FL transformation are poorly understood. We have developed a murine model of FL transformation that recapitulates key genetic and pathological aspects of human FL (Oricchio et al, 2011). This model allows us to study the genetics and metabolism of FL transformation. Specifically, we will systematically define the metabolic profiles of genetically defined murine lymphomas that represent different stages of transformation and cross-compare metabolic changes to primary patient samples. This ensures focus on clinically relevant changes and provides metabolic annotation of distinct tumor genotypes. This study builds on the complementary strengths of the Le lab (Johns Hopkins) in cancer metabolism and the Wendel lab (MSKCC) in modeling FL genetics. Our study shows that MYC transformed FL exhibits a distinct metabolic profile as compared to indolent follicular lymphoma or normal spleen. The most altered pathways examined thus far are glycolysis and amino acid metabolism. We believe that the transformed lymphoma is more reliant upon glycolysis and may be exhibiting aerobic glycolysis, also known as the Warburg Effect. This is substantiated from previous experiments in which a Burkitt lymphoma line, also overexpressing MYC, was found to have altered glycolytic intermediates levels. We next plan to examine the metabolic profile of other transformed follicular lymphoma models of known genetic backgrounds. We will also cross validate the transformed mouse models with follicular lymphoma patient samples of known genetic backgrounds to identify potential metabolic markers. Citation Format: Brad Poore, Ana Ortega-Molina, Christopher Nguyen, Liang Zhao, Anne Blackwell, Thomas Hartung, Hans-Guido Wendel, Anne Le. Metabolic characterization of follicular lymphoma transformation. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1183. doi:10.1158/1538-7445.AM2015-1183

The humoral immune response requires that B cells undergo a sudden anabolic shift and high cellular nutrient levels, which are required to sustain the subsequent proliferative burst. Follicular lymphoma (FL) originates from B cells that have participated in the humoral response, and 15% of FL samples harbour point-activating mutations in RRAGC, an essential activator of mTORC1 downstream of the sensing of cellular nutrients. The impact of recurrent RRAGC mutations in B cell function and lymphoma is unexplored. RRAGC mutations, targeted to the endogenous locus in mice, confer a partial insensitivity to nutrient deprivation, but strongly exacerbate B cell responses and accelerate lymphomagenesis, while creating a selective vulnerability to pharmacological inhibition of mTORC1. This moderate increase in nutrient signalling synergizes with paracrine cues from the supportive T cell microenvironment that activate B cells via the PI3K–Akt–mTORC1 axis. Hence, Rragc mutations sustain induced germinal centres and murine and human FL in the presence of decreased T cell help. Our results support a model in which activating mutations in the nutrient signalling pathway foster lymphomagenesis by corrupting a nutrient-dependent control over paracrine signals from the T cell microenvironment. Some follicular B cell lymphomas harbour activating mutations in RRAGC, activator of the nutrient sensor mTORC1. Here the authors show that these mutations confer insensitivity to nutrient deprivation and synergize with paracrine cues from the supportive T cell microenvironment to accelerate lymphomagenesis, but impose vulnerability to inhibition of mTORC1.

The gene encoding the lysine-specific histone methyltransferase KMT2D has emerged as one of the most frequently mutated genes in follicular lymphoma and diffuse large B cell lymphoma; however, the biological consequences of KMT2D mutations on lymphoma development are not known. Here we show that KMT2D functions as a bona fide tumor suppressor and that its genetic ablation in B cells promotes lymphoma development in mice. KMT2D deficiency also delays germinal center involution and impedes B cell differentiation and class switch recombination. Integrative genomic analyses indicate that KMT2D affects methylation of lysine 4 on histone H3 (H3K4) and expression of a set of genes, including those in the CD40, JAK-STAT, Toll-like receptor and B cell receptor signaling pathways. Notably, other KMT2D target genes include frequently mutated tumor suppressor genes such as TNFAIP3, SOCS3 and TNFRSF14. Therefore, KMT2D mutations may promote malignant outgrowth by perturbing the expression of tumor suppressor genes that control B cell-activating pathways.