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Background Cellular metabolism is an integral component of cellular adaptation to stress, playing a pivotal role in the resistance of cancer cells to various treatment modalities, including radiotherapy. In response to radiotherapy, cancer cells engage antioxidant and DNA repair mechanisms which mitigate and remove DNA damage, facilitating cancer cell survival. Given the reliance of these resistance mechanisms on amino acid metabolism, we hypothesised that controlling the exogenous availability of the non-essential amino acids serine and glycine would radiosensitise cancer cells. Methods We exposed colorectal, breast and pancreatic cancer cell lines/organoids to radiation in vitro and in vivo in the presence and absence of exogenous serine and glycine. We performed phenotypic assays for DNA damage, cell cycle, ROS levels and cell death, combined with a high-resolution untargeted LCMS metabolomics and RNA-Seq. Results Serine and glycine restriction sensitised a range of cancer cell lines, patient-derived organoids and syngeneic mouse tumour models to radiotherapy. Comprehensive metabolomic and transcriptomic analysis of central carbon metabolism revealed that amino acid restriction impacted not only antioxidant response and nucleotide synthesis but had a marked inhibitory effect on the TCA cycle. Conclusion Dietary restriction of serine and glycine is a viable radio-sensitisation strategy in cancer.

Figures S12-S14: Flow cytometry - Ly6C:Ly6G; Flow cytometry - F4:80;iNOS;CD206; Flow cytometry - gating strategy

Figures S5-S9: Survival of mice bearing Trp53-/- and Trp53-/-:Brca2-/- tumors; Disease distribution and ascites production in mice bearing Trp53-/-:Brca2-/- tumors; CD3 staining in Trp53-/-:Brca2-/- tumors; Quantification of lymphoid aggregates by absolute area and percentage tumor area; CD8 staining in Trp53-/-:Brca2-/- tumors

Figures S2-S4: Transcription of Cdkn1a in CRISPR control clones; Sanger sequencing of Brca2 exon 3; RAD51 focus formation following irradiation

Figure S1: Sanger sequencing data for Trp53 exon 5 in the 4 Trp53-/- ID8 clones

All Supplementary data figures and legends. Supplementary Figure 1. In Silico analysis of RUNX1 expression in human kidney cancer. Supplementary Figure 2. Knockdown of RUNX1 with shRNA causes a growth defect in two ccRCC cell lines. Supplementary Figure 3. RUNX1 deletion in 786-O* cells and orthotopic xenograft. Supplementary Figure 4. Principle component analysis. Gene expression variances between control (786-O pX, Red) and RUNX1 CRISPR cells (786-O A1, yellow and 786-O A3, purple). Supplementary Figure 5. Heterozygous deletion of RUNX2 in a GEM model of kidney cancer does not affect survival.

RNAseq data set

Full description of next generation sequencing, quantitative IHC and flow cytometry

The recurring association of specific genetic lesions with particular types of cancer is a fascinating and largely unexplained area of cancer biology. This is particularly true of clear cell renal cell carcinoma (ccRCC) where, although key mutations such as loss of VHL is an almost ubiquitous finding, there remains a conspicuous lack of targetable genetic drivers. In this study, we have identified a previously unknown protumorigenic role for the RUNX genes in this disease setting. Analysis of patient tumor biopsies together with loss-of-function studies in preclinical models established the importance of RUNX1 and RUNX2 in ccRCC. Patients with high RUNX1 (and RUNX2) expression exhibited significantly poorer clinical survival compared with patients with low expression. This was functionally relevant, as deletion of RUNX1 in ccRCC cell lines reduced tumor cell growth and viability in vitro and in vivo. Transcriptional profiling of RUNX1-CRISPR–deleted cells revealed a gene signature dominated by extracellular matrix remodeling, notably affecting STMN3, SERPINH1, and EPHRIN signaling. Finally, RUNX1 deletion in a genetic mouse model of kidney cancer improved overall survival and reduced tumor cell proliferation. In summary, these data attest to the validity of targeting a RUNX1-transcriptional program in ccRCC.Significance:These data reveal a novel unexplored oncogenic role for RUNX genes in kidney cancer and indicate that targeting the effects of RUNX transcriptional activity could be relevant for clinical intervention in ccRCC.

There is a need for transplantable murine models of ovarian high-grade serous carcinoma (HGSC) with regard to mutations in the human disease to assist investigations of the relationships between tumor genotype, chemotherapy response, and immune microenvironment. In addressing this need, we performed whole-exome sequencing of ID8, the most widely used transplantable model of ovarian cancer, covering 194,000 exomes at a mean depth of 400× with 90% exons sequenced >50×. We found no functional mutations in genes characteristic of HGSC (Trp53, Brca1, Brca2, Nf1, and Rb1), and p53 remained transcriptionally active. Homologous recombination in ID8 remained intact in functional assays. Further, we found no mutations typical of clear cell carcinoma (Arid1a, Pik3ca), low-grade serous carcinoma (Braf), endometrioid (Ctnnb1), or mucinous (Kras) carcinomas. Using CRISPR/Cas9 gene editing, we modeled HGSC by generating novel ID8 derivatives that harbored single (Trp53–/–) or double (Trp53–/–;Brca2–/–) suppressor gene deletions. In these mutants, loss of p53 alone was sufficient to increase the growth rate of orthotopic tumors with significant effects observed on the immune microenvironment. Specifically, p53 loss increased expression of the myeloid attractant CCL2 and promoted the infiltration of immunosuppressive myeloid cell populations into primary tumors and their ascites. In Trp53–/–;Brca2–/– mutant cells, we documented a relative increase in sensitivity to the PARP inhibitor rucaparib and slower orthotopic tumor growth compared with Trp53–/– cells, with an appearance of intratumoral tertiary lymphoid structures rich in CD3+ T cells. This work validates new CRISPR-generated models of HGSC to investigate its biology and promote mechanism-based therapeutics discovery. Cancer Res; 76(20); 6118–29. ©2016 AACR.

List of all putative functional variants in ID8

Supplementary Table 1. The relationship between RUNX2 and clinico-pathological characteristics of kidney cancer in the TMA study.

Legends for supplementary figures

Supplementary Methods from Cyclin D2–Cyclin-Dependent Kinase 4/6 Is Required for Efficient Proliferation and Tumorigenesis following Apc Loss

Supplementary Figure Legends 1-4 from Cyclin D2–Cyclin-Dependent Kinase 4/6 Is Required for Efficient Proliferation and Tumorigenesis following Apc Loss

Supplementary Figures 1-4 from Cyclin D2–Cyclin-Dependent Kinase 4/6 Is Required for Efficient Proliferation and Tumorigenesis following Apc Loss

Inactivation of the Apc gene is recognized as the key early event in the development of sporadic colorectal cancer (CRC), where its loss leads to constitutive activation of β-catenin/T-cell factor 4 signaling and hence transcription of Wnt target genes such as c-Myc. Our and other previous studies have shown that although cyclin D1 is required for adenoma formation, it is not immediately upregulated following Apc loss within the intestine, suggesting that proliferation following acute Apc loss may be dependent on another D-type cyclin. In this study, we investigated the expression and functional relevance of cyclin D2 following Apc loss in the intestinal epithelium. Cyclin D2 is upregulated immediately following Apc loss, which corresponded with a significant increase in cyclin-dependent kinase 4 (CDK4) and hyperphosphorylated Rb levels. Deficiency of cyclin D2 resulted in a reduction in enterocyte proliferation and crypt size within Apc-deficient intestinal epithelium. Moreover, cyclin D2 dramatically reduced tumor growth and development in ApcMin/+ mice. Importantly, cyclin D2 knockout did not affect proliferation of normal enterocytes, and furthermore, CDK4/6 inhibition also suppressed the proliferation of adenomatous cells and not normal cells from ApcMin/+ mice. Taken together, these results indicate that cyclin D–CDK4/6 complexes are required for the efficient proliferation of cells with deregulated Wnt signaling, and inhibiting this complex may be an effective chemopreventative strategy in CRC. Cancer Res; 70(20); 8149–58. ©2010 AACR.

Intercellular communication between different cell types in solid tumors contributes to tumor growth and metastatic dissemination. The secretome of cancer-associated fibroblasts (CAFs) plays major roles in these processes. Using human mammary CAFs, we unveil a mechanism of cell-cell communication between CAFs with myofibroblast phenotype and endothelial cells (ECs) based on intercellular protein transfer through extracellular vesicles (EVs). CAFs transfer proteins to ECs, including plasma membrane receptors, which we have identified by using mass spectrometry- based proteomics. Using THY1 as an example of transferred plasma membrane-bound protein, we show that CAF-derived proteins can influence how ECs interact with other cell types. Here, we show that CAFs produce high amounts of matrix-bound EVs that have a key role in protein transfer. Hence, our work paves the way for further studies to understand how CAF-derived matrix-bound EVs influence tumor pathology by regulating functions of neighboring cancer, stromal and immune cells.One sentence summaryCAFs with a myofibroblastic-like phenotype transfer proteins to ECs, including plasma membrane receptors, through matrix-bound EVs

Elevated production of collagen-rich extracellular matrix is a hallmark of cancer-associated fibroblasts (CAFs) and a central driver of cancer aggressiveness. Here we find that proline, a highly abundant amino acid in collagen proteins, is newly synthesized from glutamine in CAFs to make tumour collagen in breast cancer xenografts. PYCR1 is a key enzyme for proline synthesis and highly expressed in the stroma of breast cancer patients and in CAFs. Reducing PYCR1 levels in CAFs is sufficient to reduce tumour collagen production, tumour growth and metastatic spread in vivo and cancer cell proliferation in vitro. Both collagen and glutamine-derived proline synthesis in CAFs are epigenetically upregulated by increased pyruvate dehydrogenase-derived acetyl-CoA levels. PYCR1 is a cancer cell vulnerability and potential target for therapy; therefore, our work provides evidence that targeting PYCR1 may have the additional benefit of halting the production of a pro-tumorigenic extracellular matrix. Our work unveils new roles for CAF metabolism to support pro-tumorigenic collagen production. ispartof: NATURE METABOLISM vol:4 issue:6 pages:693-+ ispartof: location:Germany status: published

Many tumour cells show dependence on exogenous serine and dietary serine and glycine starvation can inhibit the growth of these cancers and extend survival in mice. However, numerous mechanisms promote resistance to this therapeutic approach, including enhanced expression of the de novo serine synthesis pathway (SSP) enzymes or activation of oncogenes that drive enhanced serine synthesis. Here we show that inhibition of PHGDH, the first step in the SSP, cooperates with serine and glycine depletion to inhibit one-carbon metabolism and cancer growth. In vitro, inhibition of PHGDH combined with serine starvation leads to a defect in global protein synthesis, which blocks the activation of an ATF-4 response and more broadly impacts the protective stress response to amino acid depletion. In vivo, the combination of diet and inhibitor shows therapeutic efficacy against tumours that are resistant to diet or drug alone, with evidence of reduced one-carbon availability. However, the defect in ATF4-response seen in vitro following complete depletion of available serine is not seen in mice, where dietary serine and glycine depletion and treatment with the PHGDH inhibitor lower but do not eliminate serine. Our results indicate that inhibition of PHGDH will augment the therapeutic efficacy of a serine depleted diet., Dietary serine and glycine starvation has emerged as a potential therapy for cancer. Here, the authors show that inhibition of PHGDH, which mediates the first step in the serine synthesis pathway, improves the therapeutic efficacy of serine depletion diet in mouse xenograft models.

Damaged or superfluous cells are typically eliminated by apoptosis. Although apoptosis is a cell-autonomous process, apoptotic cells communicate with their environment in different ways. Here we describe a mechanism whereby cells under apoptotic stress can promote survival of neighbouring cells. We find that upon apoptotic stress, cells release the growth factor FGF2, leading to MEK-ERK-dependent transcriptional upregulation of pro-survival BCL-2 proteins in a non-cell autonomous manner. This transient upregulation of pro-survival BCL-2 proteins protects neighbouring cells from apoptosis. Accordingly, we find in certain cancer types a correlation between FGF-signalling, BCL-2 expression and worse prognosis. In vivo, upregulation of MCL-1 occurs in an FGF-dependent manner during skin repair, which regulates healing dynamics. Importantly, either co-treatment with FGF-receptor inhibitors or removal of apoptotic stress restores apoptotic sensitivity to cytotoxic therapy and delays wound healing. These data reveal a pathway by which cells under apoptotic stress can increase resistance to cell death in surrounding cells. Beyond mediating cytotoxic drug resistance, this process also provides a potential link between tissue damage and repair., Apoptosis is a cellular process that eliminates damaged or superfluous cells. Here the authors show that cells undergoing apoptotic stresss secrete the growth factor FGF2, which upregulates pro-survival BCL-2 proteins in neighbouring cells, thereby promoting their survival.

Correction to: Nature Metabolism https://doi.org/10.1038/s42255-022-00582-0, published online 27 June 2022 In the version of this article initially published, the surname of the third author, Carla Riera-Domingo, was misspelled as Riero-Domingo. The error has been corrected in the HTML and PDF versions of the article.

Current nutritional recommendations are focused on energy, fat, carbohydrate, protein and vitamins. Less attention has been paid to the nutritional demand of one-carbon units for nucleotide and methionine synthesis. Here, we investigated the impact of sodium formate supplementation as a nutritional intervention to increase the dietary intake of one-carbon units. A cohort of six female and six male mice received 125 mM of sodium formate in the drinking water for three months. A control group of another six female and six male mice was also followed up for the same period of time. Tail vein blood samples were collected once a month and profiled with a haematology analyser. At the end of the study, blood and tissues were collected for metabolomics analysis and immune cell profiling. Formate supplementation had no significant physiological effect on male mice, except for a small decrease in body weight. Formate supplementation had no significant effect on the immune cell counts during the intervention or at the end of the study in either gender. In female mice, however, the body weight and spleen wet weight were significantly increased by formate supplementation, while the blood plasma levels of amino acids were decreased. Formate supplementation also increased the frequency of bifidobacteria, a probiotic bacterium, in the stools of female mice. We conclude that formate supplementation induces physiological changes in a gender-specific manner.

The recurring association of specific genetic lesions with particular types of cancer is a fascinating and largely unexplained area of cancer biology. This is particularly true of clear cell renal cell carcinoma (ccRCC) where, although key mutations such as loss of VHL is an almost ubiquitous finding, there remains a conspicuous lack of targetable genetic drivers. In this study, we have identified a previously unknown protumorigenic role for the RUNX genes in this disease setting. Analysis of patient tumor biopsies together with loss-of-function studies in preclinical models established the importance of RUNX1 and RUNX2 in ccRCC. Patients with high RUNX1 (and RUNX2) expression exhibited significantly poorer clinical survival compared with patients with low expression. This was functionally relevant, as deletion of RUNX1 in ccRCC cell lines reduced tumor cell growth and viability in vitro and in vivo. Transcriptional profiling of RUNX1-CRISPR–deleted cells revealed a gene signature dominated by extracellular matrix remodeling, notably affecting STMN3, SERPINH1, and EPHRIN signaling. Finally, RUNX1 deletion in a genetic mouse model of kidney cancer improved overall survival and reduced tumor cell proliferation. In summary, these data attest to the validity of targeting a RUNX1-transcriptional program in ccRCC. Significance: These data reveal a novel unexplored oncogenic role for RUNX genes in kidney cancer and indicate that targeting the effects of RUNX transcriptional activity could be relevant for clinical intervention in ccRCC.

TElevated production of collagen-rich extracellular matrix (ECM) is a hallmark of cancer associated fibroblasts (CAFs) and a central driver of cancer aggressiveness. How to target ECM production to oppose cancer is yet unclear, since targeting CAFs has been shown to restrain but also promote cancer progression. Metabolic rewiring is a hallmark of CAFs. Here we find that proline, which is a highly abundant amino acid in collagen proteins, is newly synthesised from glutamine to make tumour collagen in breast cancer xenografts, and that its production is elevated in breast cancer CAFs. PYCR1 is the rate-limiting enzyme for proline synthesis and is highly expressed in the tumour stroma of breast cancer patients and in CAFs. Reducing PYCR1 levels in CAFs is sufficient to reduce tumour collagen production, tumour growth and metastatic spread in vivo and cancer cell proliferation in vitro. PYCR1 and COL1A1 are overexpressed in patients with invasive ductal carcinoma with poor prognosis. Both collagen and glutamine-derived proline synthesis in CAFs are enhanced by increased pyruvate dehydrogenase-derived acetyl-CoA levels, via gene expression regulation through the epigenetic regulator histone acetyl transferase EP300. Altogether, our work unveils unprecedented roles of CAF metabolism to support pro-tumorigenic collagen production. PYCR1 is a recognised cancer cell vulnerability and potential target for therapy, hence, our work provides evidence that targeting PYCR1 in tumours may have the additional benefit of halting the production of pro-tumorigenic ECM.

Cancer cells have high demands for non-essential amino acids (NEAAs), which are precursors for anabolic and antioxidant pathways that support cell survival and proliferation. It is well-established that cancer cells consume the NEAA cysteine, and that cysteine deprivation can induce cell death; however, the specific factors governing acute sensitivity to cysteine starvation are poorly characterized. Here, we show that that neither expression of enzymes for cysteine synthesis nor availability of the primary precursor methionine correlated with acute sensitivity to cysteine starvation. We observed a strong correlation between efflux of the methionine-derived metabolite methylthioadenosine (MTA) and sensitivity to cysteine starvation. MTA efflux results from genetic deletion of methylthioadenosine phosphorylase (MTAP), which is frequently deleted in cancers. We show that MTAP loss upregulates polyamine metabolism which, concurrently with cysteine withdrawal, promotes elevated reactive oxygen species and prevents cell survival. Our results reveal an unexplored metabolic weakness at the intersection of polyamine and cysteine metabolism.

Tumor progression alters the composition and physical properties of the extracellular matrix. Particularly, increased matrix stiffness has profound effects on tumor growth and metastasis. While endothelial cells are key players in cancer progression, the influence of tumor stiffness on the endothelium and the impact on metastasis is unknown. Through quantitative mass spectrometry, we find that the matricellular protein CCN1/CYR61 is highly regulated by stiffness in endothelial cells. We show that stiffness-induced CCN1 activates β-catenin nuclear translocation and signaling and that this contributes to upregulate N-cadherin levels on the surface of the endothelium, in vitro This facilitates N-cadherin-dependent cancer cell-endothelium interaction. Using intravital imaging, we show that knockout of Ccn1 in endothelial cells inhibits melanoma cancer cell binding to the blood vessels, a critical step in cancer cell transit through the vasculature to metastasize. Targeting stiffness-induced changes in the vasculature, such as CCN1, is therefore a potential yet unappreciated mechanism to impair metastasis. ispartof: EMBO Journal vol:36 issue:16 pages:2373-2389 ispartof: location:England status: published

The non-essential amino acids serine and glycine are used in multiple anabolic processes that support cancer cell growth and proliferation (reviewed in ref. 1). While some cancer cells upregulate de novo serine synthesis, many others rely on exogenous serine for optimal growth. Restriction of dietary serine and glycine can reduce tumour growth in xenograft and allograft models. Here we show that this observation translates into more clinically relevant autochthonous tumours in genetically engineered mouse models of intestinal cancer (driven by Apc inactivation) or lymphoma (driven by Myc activation). The increased survival following dietary restriction of serine and glycine in these models was further improved by antagonizing the anti-oxidant response. Disruption of mitochondrial oxidative phosphorylation (using biguanides) led to a complex response that could improve or impede the anti-tumour effect of serine and glycine starvation. Notably, Kras-driven mouse models of pancreatic and intestinal cancers were less responsive to depletion of serine and glycine, reflecting an ability of activated Kras to increase the expression of enzymes that are part of the serine synthesis pathway and thus promote de novo serine synthesis.

Summary Cancer cells adapt their metabolism to support elevated energetic and anabolic demands of proliferation. Folate-dependent one-carbon metabolism is a critical metabolic process underpinning cellular proliferation supplying carbons for the synthesis of nucleotides incorporated into DNA and RNA. Recent research has focused on the nutrients that supply one-carbons to the folate cycle, particularly serine. Tryptophan is a theoretical source of one-carbon units through metabolism by IDO1, an enzyme intensively investigated in the context of tumor immune evasion. Using in vitro and in vivo pancreatic cancer models, we show that IDO1 expression is highly context dependent, influenced by attachment-independent growth and the canonical activator IFNγ. In IDO1-expressing cancer cells, tryptophan is a bona fide one-carbon donor for purine nucleotide synthesis in vitro and in vivo. Furthermore, we show that cancer cells release tryptophan-derived formate, which can be used by pancreatic stellate cells to support purine nucleotide synthesis., Graphical abstract, Highlights • IFNγ and attachment-independent growth promote IDO1 expression in PDAC cells • Metabolism of tryptophan by IDO1 contributes one-carbons to the THF cycle • Tryptophan can substitute for serine as a one-carbon source • Serine and glycine restriction enhances the anti-tumor activity of an IDO1 inhibitor, Newman et al. studied the metabolic outcomes of immune-regulated IDO1 expression in pancreatic cancer and stellate cells, reporting that IDO1-dependent tryptophan metabolism is a bona fide one-carbon source for folate-dependent nucleotide synthesis. Tryptophan substituted for serine as a one-carbon donor, with serine restriction improving the anti-tumor activity of IDO1 inhibitor epacadostat.

Formate is a precursor for the de novo synthesis of purine and deoxythymidine nucleotides. Formate also interacts with energy metabolism by promoting the synthesis of adenine nucleotides. Here we use theoretical modelling together with metabolomics analysis to investigate the link between formate, nucleotide and energy metabolism. We uncover that endogenous or exogenous formate induces a metabolic switch from low to high adenine nucleotide levels, increasing the rate of glycolysis and repressing the AMPK activity. Formate also induces an increase in the pyrimidine precursor orotate and the urea cycle intermediate argininosuccinate, in agreement with the ATP dependent activities of carbamoyl-phosphate and argininosuccinate synthetase. In vivo data for mouse and human cancers confirms the association between increased formate production, nucleotide and energy metabolism. Finally, the in vitro observations are recapitulated in mice following intraperitoneal injection of formate. We conclude that formate is a potent regulator of purine, pyrimidine and energy metabolism.

Background: Cutaneous squamous cell carcinoma (cSCC) incidence continues to rise with increasing morbidity and mortality, with limited treatment options for advanced disease. Future improvements in targeted therapy will rely on advances in genomic/transcriptomic understanding and the use of model systems for basic research. We describe here the panel of 16 primary and metastatic cSCC cell lines developed and characterised over the past three decades in our laboratory in order to provide such a resource for future preclinical research and drug screening. Methods: Primary keratinocytes were isolated from cSCC tumours and metastases, and cell lines were established. These were characterised using short tandem repeat (STR) profiling and genotyped by whole exome sequencing. Multiple in vitro assays were performed to document their morphology, growth characteristics, migration and invasion characteristics, and in vivo xenograft growth. Results: STR profiles of the cSCC lines allow the confirmation of their unique identity. Phylogenetic trees derived from exome sequence analysis of the matched primary and metastatic lines provide insight into the genetic basis of disease progression. The results of in vivo and in vitro analyses allow researchers to select suitable cell lines for specific experimentation. Conclusions: There are few well-characterised cSCC lines available for widespread preclinical experimentation and drug screening. The described cSCC cell line panel provides a critical tool for in vitro and in vivo experimentation.

There is a need for transplantable murine models of ovarian high-grade serous carcinoma (HGSC) with regard to mutations in the human disease to assist investigations of the relationships between tumor genotype, chemotherapy response, and immune microenvironment. In addressing this need, we performed whole-exome sequencing of ID8, the most widely used transplantable model of ovarian cancer, covering 194,000 exomes at a mean depth of 400× with 90% exons sequenced >50×. We found no functional mutations in genes characteristic of HGSC (Trp53, Brca1, Brca2, Nf1, and Rb1), and p53 remained transcriptionally active. Homologous recombination in ID8 remained intact in functional assays. Further, we found no mutations typical of clear cell carcinoma (Arid1a, Pik3ca), low-grade serous carcinoma (Braf), endometrioid (Ctnnb1), or mucinous (Kras) carcinomas. Using CRISPR/Cas9 gene editing, we modeled HGSC by generating novel ID8 derivatives that harbored single (Trp53–/–) or double (Trp53–/–;Brca2–/–) suppressor gene deletions. In these mutants, loss of p53 alone was sufficient to increase the growth rate of orthotopic tumors with significant effects observed on the immune microenvironment. Specifically, p53 loss increased expression of the myeloid attractant CCL2 and promoted the infiltration of immunosuppressive myeloid cell populations into primary tumors and their ascites. In Trp53–/–;Brca2–/– mutant cells, we documented a relative increase in sensitivity to the PARP inhibitor rucaparib and slower orthotopic tumor growth compared with Trp53–/– cells, with an appearance of intratumoral tertiary lymphoid structures rich in CD3+ T cells. This work validates new CRISPR-generated models of HGSC to investigate its biology and promote mechanism-based therapeutics discovery. Cancer Res; 76(20); 6118–29. ©2016 AACR.

Endothelial cells (ECs) form the inner layer of blood vessels and physically separate the blood from the surrounding tissue. To support tissues with nutrients and oxygen, the endothelial monolayer is semipermeable. When EC permeability is altered, blood vessels are not functional, and this is associated with disease. A comprehensive knowledge of the mechanisms regulating EC permeability is key in developing strategies to target this mechanism in pathologies. Here we have used an in vitro model of human umbilical vein endothelial cells mimicking the formation of a physiologically permeable vessel and performed time-resolved in-depth molecular profiling using stable isotope labeling by amino acids in cell culture mass spectrometry (MS)-proteomics. Autophagy is induced when ECs are assembled into a physiologically permeable monolayer. By using siRNA and drug treatment to block autophagy in combination with functional assays and MS proteomics, we show that ECs require autophagy flux to maintain intracellular reactive oxygen species levels, and this is required to maintain the physiological permeability of the cells.

The murine double minute 2 (MDM2) protein is an E3 ubiquitin ligase most notable for priming tumour-suppressor p53 for degradation. MDM2 contains two promoters - the constitutive P1 and the inducible P2. The p53-independent P1 promoter is responsible for basal levels of MDM2, whilst the p53-dependent P2 promoter is activated upon stress responses. Although the oncogenic functions of MDM2 are well understood, less is known about the individual roles of the promoters and their contribution to tumorigenesis and stress responses. To tease apart the roles of the promoters, we have used genetically engineered mouse (GEM) models null for the P1-promoter and mutated for the P2-promoter in the context of intestinal cancer, lymphoma and hepatocellular carcinoma (HCC). Here, we have shown that mice with heterozygous or homozygous loss of the P1-promoter in the APCMin/+ intestinal model have extended survival and reduced intestinal tumour burden in comparison to the P1- wild type (WT), APCMin/+ mice. Surprisingly, none of the P1-null APCMin/+ mice succumbed to intestinal tumours, but rather to thymic lymphomas. In the P1-null APCMin/+ lymphoma samples, we investigated the p53 functionality by examining the expression levels of p21, a p53 downstream target. Immunohistochemistry analysis clearly revealed that p53 is non-functional as p21 was not expressed, despite variations in p53 expression levels itself. This uncommon occurrence in the APCMin/+ model led us to investigate the role of the P1 and P2 promoters in the Eµ-Myc lymphoma model. Interestingly, in this model, heterozygous loss of the P1 promoter improves survival, while heterozygous loss of the P2 promoter accelerates lymphomagenesis. Our findings thus far indicate a differential role for the P1 and P2 MDM2 promoters in tumorigenesis. In addition to using GEM models, we are investigating the role of the MDM2 promoters in stress-induced HCC. These studies will allow for a better understanding of MDM2 functions, but also perhaps provide an alternative therapeutic strategy for cancers with aberrations in the p53-MDM2 signalling axis. Citation Format: Narisa Phinichkusolchit, Thomas Jamieson, Rachel Ridgway, Dimitris Athineos, Kerryanne Crawford, Nikolina Vlatkovic, Mark Boyd, Owen Sansom, Karen Blyth. MDM2 P1 and P2 promoters have different roles in tumorigenesis [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1620.

Formate overflow coupled to mitochondrial oxidative metabolism\ has been observed in cancer cell lines, but whether that takes place in the tumor microenvironment is not known. Here we report the observation of serine catabolism to formate in normal murine tissues, with a relative rate correlating with serine levels and the tissue oxidative state. Yet, serine catabolism to formate is increased in the transformed tissue of in vivo models of intestinal adenomas and mammary carcinomas. The increased serine catabolism to formate is associated with increased serum formate levels. Finally, we show that inhibition of formate production by genetic interference reduces cancer cell invasion and this phenotype can be rescued by exogenous formate. We conclude that increased formate overflow is a hallmark of oxidative cancers and that high formate levels promote invasion via a yet unknown mechanism., Serine catabolism to formate supplies one-carbon units for biosynthesis. Here the authors show that formate production in murine cancers with high oxidative metabolism exceeds the biosynthetic demand and that high formate levels promotes invasion of cancer cells.

SummaryRegulation of metabolic pathways plays an important role in controlling cell growth, proliferation, and survival. TIGAR acts as a fructose-2,6-bisphosphatase, potentially promoting the pentose phosphate pathway to produce NADPH for antioxidant function and ribose-5-phosphate for nucleotide synthesis. The functions of TIGAR were dispensable for normal growth and development in mice but played a key role in allowing intestinal regeneration in vivo and in ex vivo cultures, where growth defects due to lack of TIGAR were rescued by ROS scavengers and nucleosides. In a mouse intestinal adenoma model, TIGAR deficiency decreased tumor burden and increased survival, while elevated expression of TIGAR in human colon tumors suggested that deregulated TIGAR supports cancer progression. Our study demonstrates the importance of TIGAR in regulating metabolism for regeneration and cancer development and identifies TIGAR as a potential therapeutic target in diseases such as ulcerative colitis and intestinal cancer.

Oncogene-induced senescence (OIS) is crucial for tumour suppression. Senescent cells implement a complex pro-inflammatory response termed the senescence-associated secretory phenotype (SASP). The SASP reinforces senescence, activates immune surveillance and paradoxically also has pro-tumorigenic properties. Here, we present evidence that the SASP can also induce paracrine senescence in normal cells both in culture and in human and mouse models of OIS in vivo. Coupling quantitative proteomics with small-molecule screens, we identified multiple SASP components mediating paracrine senescence, including TGF-β family ligands, VEGF, CCL2 and CCL20. Amongst them, TGF-β ligands play a major role by regulating p15(INK4b) and p21(CIP1). Expression of the SASP is controlled by inflammasome-mediated IL-1 signalling. The inflammasome and IL-1 signalling are activated in senescent cells and IL-1α expression can reproduce SASP activation, resulting in senescence. Our results demonstrate that the SASP can cause paracrine senescence and impact on tumour suppression and senescence in vivo. Core support from the MRC and grants from MRCT, CRUK and the AICR financially supported the research in J.G's laboratory. J.G. is also supported by the EMBO Young Investigator Programme

SummaryThe Adenomatous Polyposis Coli (APC) gene is mutated in the majority of colorectal cancers (CRCs). Loss of APC leads to constitutively active WNT signaling, hyperproliferation, and tumorigenesis. Identification of pathways that facilitate tumorigenesis after APC loss is important for therapeutic development. Here, we show that RAC1 is a critical mediator of tumorigenesis after APC loss. We find that RAC1 is required for expansion of the LGR5 intestinal stem cell (ISC) signature, progenitor hyperproliferation, and transformation. Mechanistically, RAC1-driven ROS and NF-κB signaling mediate these processes. Together, these data highlight that ROS production and NF-κB activation triggered by RAC1 are critical events in CRC initiation.

Serine catabolism results in formate efflux that exceeds anabolic demands for purine synthesis., Serine catabolism to glycine and a one-carbon unit has been linked to the anabolic requirements of proliferating mammalian cells. However, genome-scale modeling predicts a catabolic role with one-carbon release as formate. We experimentally prove that in cultured cancer cells and nontransformed fibroblasts, most of the serine-derived one-carbon units are released from cells as formate, and that formate release is dependent on mitochondrial reverse 10-CHO-THF synthetase activity. We also show that in cancer cells, formate release is coupled to mitochondrial complex I activity, whereas in nontransformed fibroblasts, it is partially insensitive to inhibition of complex I activity. We demonstrate that in mice, about 50% of plasma formate is derived from serine and that serine starvation or complex I inhibition reduces formate synthesis in vivo. These observations transform our understanding of one-carbon metabolism and have implications for the treatment of diabetes and cancer with complex I inhibitors.

Melanoma patients treated with oncogenic BRAF inhibitors can develop cutaneous squamous cell carcinoma (cSCC) within weeks of treatment, driven by paradoxical RAS/RAF/MAPK pathway activation. Here we identify frequent TGFBR1 and TGFBR2 mutations in human vemurafenib-induced skin lesions and in sporadic cSCC. Functional analysis reveals these mutations ablate canonical TGFβ Smad signalling, which is localized to bulge stem cells in both normal human and murine skin. MAPK pathway hyperactivation (through BrafV600E or KrasG12D knockin) and TGFβ signalling ablation (through Tgfbr1 deletion) in LGR5+ve stem cells enables rapid cSCC development in the mouse. Mutation of Tp53 (which is commonly mutated in sporadic cSCC) coupled with Tgfbr1 deletion in LGR5+ve cells also results in cSCC development. These findings indicate that LGR5+ve stem cells may act as cells of origin for cSCC, and that RAS/RAF/MAPK pathway hyperactivation or Tp53 mutation, coupled with loss of TGFβ signalling, are driving events of skin tumorigenesis., Cutaneous squamous cell carcinomas is a growing problem but the driver genes causing this remain poorly defined. Here, the authors demonstrate that inactivating driver mutations in TGFBR1 and TGFBR2 occur in vemurafenib-induced and sporadic cutaneous squamous cell carcinomas.

Background: Transplantable murine models of ovarian high-grade serous carcinoma (HGSC) that recreate key mutations seen in the human disease are greatly needed. These models would assist investigation of the relationships between tumor genotype, chemotherapy response, and immune microenvironment. ID8 is a widely-used murine model of ovarian cancer. However, we previously showed that it is poorly characteristic of HGSC, with no functional alterations in key HGSC genes including Trp53, Brca1, Brca2, Pten, Nf1, and Rb1. We generated novel ID8 derivatives with single (Trp53-/-) and double (Trp53-/-;Brca2-/-) mutations using CRISPR/Cas9 gene editing. Methods: We have now generated further ID8 derivatives: Trp53-/-;Brca1-/-, Trp53-/-;Pten-/- and Trp53-/-;Nf1-/-. In vitro, we assessed DNA double-strand break repair, and sensitivity to both platinum chemotherapy and PARP inhibition, as well as cytokine and chemokine production. In vivo, we investigated intraperitoneal growth, as well as immune cell infiltration into the tumor microenvironment. Results: Assays of homologous recombination (HR) function confirm that loss of Brca1 function, but not Pten or Nf1, renders cells HR defective. This is accompanied by significant increases in sensitivity to both platinum and the PARP inhibitor rucaparib in Trp53-/-;Brca1-/- cells compared to Trp53-/-. Drug sensitivity in Trp53-/-;Pten-/- and Trp53-/-;Nf1-/- cells remains unchanged compared to Trp53-/- cells. In vivo, loss of Pten and Nf1 significantly reduced time to reach humane endpoints following intraperiteonal injection (34 and 36.5 days respectively) compared to p53 loss alone (46 days, both p There were significant differences in survival for the different genotypes following three doses of intraperitoneal cisplatin (5mg/kg on days 28, 35, and 42 only). Mice bearing control Trp53-/- tumors reached humane endpoint in a median of 81 days. Trp53-/-;Pten-/- and Trp53-/-;Nf1-/- tumors produced the worst survival (median 69 and 71 days, respectively; p In poor-prognosis Trp53-/-;Pten-/- and Trp53-/-;Nf1-/- tumors, whole-blood analysis of mice at endpoint shows a significant decrease in haemoglobin compared to single Trp53-/- tumors (p=0.0023). Furthermore, flow cytometry data show a significant increase in CD11b+;Ly6CG++ neutrophils in the ascites of mice compared to single Trp53-/-, suggesting an immunosuppressive microenvironment (p=0.0146). Analysis of whole blood at endpoint again shows a significant increase in neutrophils in mice bearing double Trp53-/-;Pten-/- tumors compared to single Trp53-/- (p=0.0203). Possible mechanisms suggested from cytokine array data include increased expression of CCL7 in Trp53-/-;Pten-/- cells, which is confirmed in tumors. Further work to characterize T-cell activation in these models is ongoing. Conclusions: These novel ID8 models represent a new and simple tool to investigate the biology of HGSC. All cells will be made available to other researchers upon request. This abstract is also being presented as Poster B61. Citation Format: Josephine Walton, Malcolm Farquharson, Susan Mason, Julianna Blagih, Darren Ennis, Elaine Leung, Suzanne Dowson, Dimitris Athineos, Damiano Rami, David Stevenson, Seth Coffelt, Karen Blyth, Douglas Strathdee, Frances Balkwill, Karen Vousden, Michelle Lockley, Iain McNeish. CRISPR/Cas9-mediated Trp53, Brca1, Brca2, Pten, and Nf1 knockout to generate improved murine models of ovarian high-grade serous carcinoma. [abstract]. In: Proceedings of the AACR Conference: Addressing Critical Questions in Ovarian Cancer Research and Treatment; Oct 1-4, 2017; Pittsburgh, PA. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(15_Suppl):Abstract nr PR14.

Introduction Oncolytic viruses are a promising new cancer therapy, since they can infect cancer cells, selectively multiply within them and induce direct cytotoxicity, leading to the release of mature viral particles that can infect other neighboring cancer cells. However, the mechanisms by which oncolytic adenoviruses induce cell death remains uncertain. It was long thought that DNA viruses induce apoptosis, but there is now evidence that cell death induced by adenovirus, vaccinia and HSV-1 displays features strongly resembling a form of programmed necrosis. Methods and Results In order to investigate the role of necrosis in cell death as a result of oncolytic adenovirus infection, cancer cells were infected with the E1A CR2-deleted adenoviral mutant dl922-947, which specifically replicates in cells that have abnormalities in the pRB-pathway. We specifically sought to investigate the role of the core necrotic proteins RIPK1, RIPK3 and MLKL in adenovirus cytotoxicity. Electron microscopy indicated that dl922-947 infection induces key morphological changes similar to necrotic death induced by TSZ (TNF-α, Smac-mimetic, Z.Vad.fmk) treatment. Using specific inhibitors of programmed necrosis (necrostatin-1, necrosulfonamide, GSK'840B and GSK'843A) as well as RNAi-mediated knockdown of RIPK1, RIPK3 and MLKL, we showed that adenovirus-infected cancer cells undergo RIPK3-dependent necrosis. We further found that, while TNF-α-induced programmed necrosis relies on the (RHIM)-dependent interaction of RIPK1 and RIPK3, dl922-947-induced cell death is independent of TNF-α signalling, does not involve RIPK1 and does not rely on the presence of MLKL. Caspase-8 inhibition, however, induces RIPK3-dependent necrosis that significantly enhances dl922-947 cytotoxicity. Using CRISPR/Cas9 gene editing, we have demonstrated that this increase in cytotoxicity during caspase inhibition was MLKL dependent. Using a RIPK3 overexpression model, we observed that the extent of adenovirus-induced cell death correlated with RIPK3 expression even in the absence of caspase inhibition. Using RIPK3 co-immunoprecipitation, we identified an interaction between RIPK3 and MLKL as well as an interaction between RIPK3 and adenoviral proteins. In vivo experiments using human xenografts showed that expression of RIPK3 significantly improved anti-tumor activity following intra-tumoral injection of dl922-947. Conclusions Our data suggest that adenovirus infection induces a novel form of programmed necrosis that differs from classical TSZ-induced necroptosis, but still relies on the kinase RIPK3. Unfortunately, many cancer cells do not express RIPK3 and can therefore not undergo programmed necrosis. The integration of human RIPK3 into an adenoviral vector offers a therapeutic window to eradicate cancer cells that are resistant to apoptosis. Citation Format: Melanie Weigert, Alex Binks, Suzanne Dowson, Elaine Leung, Dimitris Athineos, Xinzi Yu, Margaret Mullin, Josephine Walton, Clare Orange, Darren Ennis, Karen Blyth, Stephen Tait, Iain McNeish. Oncolytic adenovirus type 5 induces a novel form of programmed necrosis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4379.