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The BRCA1-PALB2-BRCA2 axis, or the BRCA pathway, plays key roles in genome stability maintenance and suppression of breast and several other cancers. Due to frequent p53 mutations in human BRCA1 breast cancers and mouse mammary tumors from Brca1, Brca2 and Palb2 conditional knockout models, it is often thought that p53 inactivation accelerates BRCA1/2 and PALB2-associated tumorigenesis. Here, we studied tumor development in mice with a mutation in Palb2 that disengages the PALB2-BRCA1 interaction in different Trp53 backgrounds. Rather than mammary tumors, Palb2 and Trp53 compound mutant mice developed, with greatly reduced latencies, lymphomas and sarcomas that are typically associated with germline Trp53 inactivation. Whole exome sequencing failed to identify any significant differences in genomic features between the same tumor types of Trp53 single mutant and Palb2;Trp53 compound mutant mice. These results suggest that loss of the BRCA pathway accelerates p53-associated tumor development, possibly without altering the fundamental tumorigenic processes.

Macroautophagy (hereafter autophagy) degrades and recycles intracellular components to sustain metabolism and survival during starvation. Host autophagy promotes tumor growth by providing essential tumor nutrients. Autophagy also regulates immune cell homeostasis and function and suppresses inflammation. Although host autophagy does not promote a T-cell antitumor immune response in tumors with low tumor mutational burden (TMB), whether this was the case in tumors with high TMB was not known. Here we show that autophagy, especially in the liver, promotes tumor immune tolerance by enabling regulatory T-cell function and limiting stimulator of interferon genes, T-cell response and interferon-γ, which enables growth of high-TMB tumors. We have designated this as hepatic autophagy immune tolerance. Autophagy thereby promotes tumor growth through both metabolic and immune mechanisms depending on mutational load and autophagy inhibition is an effective means to promote an antitumor T-cell response in high-TMB tumors. White and colleagues identify a role for host autophagy in restraining T-cell-dependent immune responses, specifically against tumors with high mutational burden.

Lung carcinoids (LC) are rare and slow growing primary lung neuroendocrine tumors. We performed targeted exome sequencing, mRNA sequencing, and DNA methylation array analysis on macro-dissected LCs. Recurrent mutations were enriched for genes involved in covalent histone modification/chromatin remodeling (34.5%; MEN1, ARID1A, KMT2C, and KMT2A) as well as DNA repair (17.2%) pathways. Unsupervised clustering and principle component analysis on gene expression and DNA methylation profiles showed three robust molecular subtypes (LC1, LC2, LC3) with distinct clinical features. MEN1 gene mutations were found to be exclusively enriched in the LC2 subtype. LC1 and LC3 subtypes were predominately found at peripheral and endobronchial lung, respectively. The LC3 subtype was diagnosed at a younger age than LC1 and LC2 subtypes. IHC staining of two biomarkers, ASCL1 and S100, sufficiently stratified the three subtypes. This molecular classification of LCs into three subtypes may facilitate understanding of their molecular mechanisms and improve diagnosis and clinical management. Significance: Integrative genomic analysis of lung carcinoids identifies three novel molecular subtypes with distinct clinical features and provides insight into their distinctive molecular signatures of tumorigenesis, diagnosis, and prognosis.

BRAF-driven colorectal cancer is among the poorest prognosis subtypes of colon cancer. Previous studies suggest that BRAF-mutant serrated cancers frequently exhibit Microsatellite Instability (MSI) and elevated levels of WNT signaling. The loss of tumor-suppressor Smad4 in oncogenic BRAF-V600E mouse models promotes rapid serrated tumor development and progression, and SMAD4 mutations co-occur in human patient tumors with BRAF-V600E mutations. This study assesses the role of SMAD4 in early-stage serrated tumorigenesis. SMAD4 loss promotes microsatellite stable (MSS) serrated tumors in an oncogenic BRAF-V600E context, providing a model for MSS serrated cancers. Inactivation of Msh2 in these mice accelerated tumor formation, and whole-exome sequencing of both MSS and MSI serrated tumors derived from these mouse models revealed that all serrated tumors developed oncogenic WNT mutations, predominantly in the WNT-effector gene Ctnnb1 (β-catenin). Mouse models mimicking the oncogenic β-catenin mutation show that the combination of three oncogenic mutations (Ctnnb1, Braf, and Smad4) are critical to drive rapid serrated dysplasia formation. Re-analysis of human tumor data reveals BRAF-V600E mutations co-occur with oncogenic mutations in both WNT and SMAD4/TGFβ pathways. These findings identify SMAD4 as a critical factor in early-stage serrated cancers and helps broaden the knowledge of this rare but aggressive subset of colorectal cancer.

Radiation-induced lymphomagenesis results from a clonogenic lymphoid cell proliferation due to genetic alterations and immunological dysregulation. Mouse models had been successfully used to identify risk and protective factors for radiation-induced DNA damage and carcinogenesis. The mammalian SETD4 is a poorly understood putative methyltransferase. Here, we report that conditional Setd4 deletion in adult mice significantly extended the survival of radiation-induced T-lymphoma. However, in Tp53 deficient mice, Setd4 deletion did not delay the radiation-induced lymphomagenesis although it accelerated the spontaneous T-lymphomagenesis in non-irradiated mice. The T-lymphomas were largely clonogenic in both Setd4(flox/flox) and Setd4(Δ/Δ) mice based on sequencing analysis of the T-cell antigen β receptors. However, the Setd4(Δ/Δ) T-lymphomas were CD4(+)/CD8(+) double positive, while the littermate Setd4(flox/flox) tumor were largely CD8+ single positive. A genomic sequencing analysis on chromosome deletion, inversion, duplication, and translocation, revealed a larger contribution of inversion but a less contribution of deletion to the overall chromosome rearrangements in the in Setd4(Δ/Δ) tumors than the Setd4(flox/flox) tumors. In addition, the Setd4(flox/flox) mice died more often from the large sizes of primary thymus lymphoma at earlier time, but there was a slight increase of lymphoma dissemination among peripheral organs in Setd4(Δ/Δ) at later times. These results suggest that Setd4 has a critical role in modulating lymphomagenesis and may be targeted to suppress radiation-induced carcinogenesis.

The receptor for hyaluronic acid-mediated motility (RHAMM) is upregulated in various cancers. We previously screened genes upregulated in human hepatocellular carcinomas for their metastatic function in a mouse model of pancreatic neuroendocrine tumor (PNET) and identified that humanRHAMMBpromoted liver metastasis. It was unknown whetherRHAMMBis upregulated in pancreatic cancer or contributes to its progression. In this study, we found that RHAMM protein was frequently upregulated in human PNETs. We investigated alternative splicing isoforms,RHAMMAandRHAMMB, by RNA-Seq analysis of primary PNETs and liver metastases.RHAMMB, but notRHAMMA, was significantly upregulated in liver metastases. RHAMMBwas crucial forin vivometastatic capacity of mouse and human PNETs. RHAMMA, carrying an extra 15-amino acid-stretch, did not promote metastasis in spontaneous and experimental metastasis mouse models. Moreover,RHAMMBwas substantially higher thanRHAMMAin pancreatic ductal adenocarcinoma (PDAC).RHAMMB, but notRHAMMA, correlated with both higherEGFRexpression and poorer survival of PDAC patients. Knockdown of EGFR abolished RHAMMB-driven PNET metastasis. Altogether, our findings suggest a clinically relevant function ofRHAMMB, but notRHAMMA, in promoting PNET metastasis in part through EGFR signaling.RHAMMBcan thus serve as a prognostic factor for pancreatic cancer.

This study used mice heterozygous for Tp53 mutations with different genetic backgrounds to investigate the genetic or stochastic factors that modify the penetrance of tumor formation by Tp53 mutation., p53 is the most frequently mutated gene in human cancers. Li-Fraumeni syndrome patients inheriting heterozygous p53 mutations often have a much-increased risk to develop cancer(s) at early ages. Recent studies suggest that some individuals inherited p53 mutations do not have the early onset or high frequency of cancers. These observations suggest that other genetic, environmental, immunological, epigenetic, or stochastic factors modify the penetrance of the cancerous mutant Tp53 phenotype. To test this possibility, this study explored dominant genetic modifiers of Tp53 mutations in heterozygous mice with different genetic backgrounds. Both genetic and stochastic effects upon tumor formation were observed in these mice. The genetic background of mice carrying Tp53 mutations has a strong influence upon the tissue type of the tumor produced and the number of tumors formed in a single mouse. The onset age of a tumor is correlated with the tissue type of that tumor, although identical tumor tissue types can occur at very different ages. These observations help to explain the great diversity of cancers in different Li-Fraumeni patients over lifetimes.

Purpose: Zinc metallochaperones (ZMC) are a new class of anticancer drugs that reactivate zinc-deficient mutant p53 by raising and buffering intracellular zinc levels sufficiently to restore zinc binding. In vitro pharmacodynamics of ZMCs indicate that p53-mutant activity is ON by 4–6 hours and is OFF by 24. We sought to understand the mechanism of this regulation and to translate these findings preclinically. We further sought to innovate the formulation of ZMCs to improve efficacy. Experimental Design: We performed in vitro mechanistic studies to determine the role of cellular zinc homeostatic mechanisms in the transient pharmacodynamics of ZMCs. We conducted preclinical pharmacokinetic, pharmacodynamic, and efficacy studies using a genetically engineered murine pancreatic cancer model (KPC) to translate these mechanistic findings and investigate a novel ZMC formulation. Results: In vitro, cellular zinc homeostatic mechanisms that restore zinc to its physiologic levels function as the OFF switch in ZMC pharmacodynamics. In vivo pharmacokinetic studies indicate that ZMCs have a short half-life (< 30 minutes), which is sufficient to significantly improve survival in mice expressing a zinc-deficient allele (p53R172H) while having no effect in mice expressing a non–zinc-deficient allele (p53R270H). We synthesized a novel formulation of the drug in complex with zinc and demonstrate this significantly improves survival over ZMC1. Conclusions: Cellular zinc homeostatic mechanisms function as an OFF switch in ZMC pharmacodynamics, indicating that a brief period of p53-mutant reactivation is sufficient for on-target efficacy. ZMCs synthesized in complex with zinc are an improved formulation. Clin Cancer Res; 24(18); 4505–17. ©2018 AACR.

Liposarcoma (LPS) is a type of soft tissue sarcoma that mostly occurs in adults, and in humans is characterized by amplifications of MDM2 and CDK4. The molecular pathogenesis of this malignancy is still poorly understood and, therefore, we developed a mouse model with conditional inactivation of PTEN and p53 to investigate these pathways in the progression of the disease. We show that deletion of these two tumor suppressors cooperate in the formation of multiple subtypes of LPS (from well-differentiated LPS to pleomorphic LPS). In addition, progression of the tumors is further characterized by the expression of D cyclins and CDK4/6, which allow for continued cell division. Microarray analysis also revealed novel genes that are differentially expressed between different subtypes of LPS, which could aid in understanding the disease and to unravel potential new therapeutic targets.

To study the frequency with which targeted tumor sequencing results will lead to implemented change in care, this study assessed tumors from 100 patients for utility, feasibility, and limitations of genomic sequencing for genomically guided therapy or other clinical purpose in the setting of a multidisciplinary molecular tumor board. Comprehensive profiling led to implementable clinical action in 35% of tumors with genomic alterations., Background. The frequency with which targeted tumor sequencing results will lead to implemented change in care is unclear. Prospective assessment of the feasibility and limitations of using genomic sequencing is critically important. Methods. A prospective clinical study was conducted on 100 patients with diverse-histology, rare, or poor-prognosis cancers to evaluate the clinical actionability of a Clinical Laboratory Improvement Amendments (CLIA)-certified, comprehensive genomic profiling assay (FoundationOne), using formalin-fixed, paraffin-embedded tumors. The primary objectives were to assess utility, feasibility, and limitations of genomic sequencing for genomically guided therapy or other clinical purpose in the setting of a multidisciplinary molecular tumor board. Results. Of the tumors from the 92 patients with sufficient tissue, 88 (96%) had at least one genomic alteration (average 3.6, range 0–10). Commonly altered pathways included p53 (46%), RAS/RAF/MAPK (rat sarcoma; rapidly accelerated fibrosarcoma; mitogen-activated protein kinase) (45%), receptor tyrosine kinases/ligand (44%), PI3K/AKT/mTOR (phosphatidylinositol-4,5-bisphosphate 3-kinase; protein kinase B; mammalian target of rapamycin) (35%), transcription factors/regulators (31%), and cell cycle regulators (30%). Many low frequency but potentially actionable alterations were identified in diverse histologies. Use of comprehensive profiling led to implementable clinical action in 35% of tumors with genomic alterations, including genomically guided therapy, diagnostic modification, and trigger for germline genetic testing. Conclusion. Use of targeted next-generation sequencing in the setting of an institutional molecular tumor board led to implementable clinical action in more than one third of patients with rare and poor-prognosis cancers. Major barriers to implementation of genomically guided therapy were clinical status of the patient and drug access. Early and serial sequencing in the clinical course and expanded access to genomically guided early-phase clinical trials and targeted agents may increase actionability. Implications for Practice: Identification of key factors that facilitate use of genomic tumor testing results and implementation of genomically guided therapy may lead to enhanced benefit for patients with rare or difficult to treat cancers. Clinical use of a targeted next-generation sequencing assay in the setting of an institutional molecular tumor board led to implementable clinical action in over one third of patients with rare and poor prognosis cancers. The major barriers to implementation of genomically guided therapy were clinical status of the patient and drug access both on trial and off label. Approaches to increase actionability include early and serial sequencing in the clinical course and expanded access to genomically guided early phase clinical trials and targeted agents.

Macroautophagy (autophagy hereafter) captures intracellular proteins and organelles and degrades them in lysosomes. The degradation breakdown products are released from lysosomes and recycled into metabolic and biosynthetic pathways. Basal autophagy provides protein and organelle quality control by eliminating damaged cellular components. Starvation-induced autophagy recycles intracellular components into metabolic pathways to sustain mitochondrial metabolic function and energy homeostasis. Recycling by autophagy is essential for yeast and mammals to survive starvation through intracellular nutrient scavenging. Autophagy suppresses degenerative diseases and has a context-dependent role in cancer. In some models, cancer initiation is suppressed by autophagy. By preventing the toxic accumulation of damaged protein and organelles, particularly mitochondria, autophagy limits oxidative stress, chronic tissue damage, and oncogenic signaling, which suppresses cancer initiation. This suggests a role for autophagy stimulation in cancer prevention, although the role of autophagy in the suppression of human cancer is unclear. In contrast, some cancers induce autophagy and are dependent on autophagy for survival. Much in the way that autophagy promotes survival in starvation, cancers can use autophagy-mediated recycling to maintain mitochondrial function and energy homeostasis to meet the elevated metabolic demand of growth and proliferation. Thus, autophagy inhibition may be beneficial for cancer therapy. Moreover, tumors are more autophagy-dependent than normal tissues, suggesting that there is a therapeutic window. Despite these insights, many important unanswered questions remain about the exact mechanisms of autophagy-mediated cancer suppression and promotion, how relevant these observations are to humans, and whether the autophagy pathway can be modulated therapeutically in cancer. Clin Cancer Res; 21(22); 5037–46. ©2015 AACR. See all articles in this CCR Focus section, “Cell Death and Cancer Therapy.”

Pancreatic neuroendocrine tumors (PanNETs) or islet cell tumors are a rare neuroendocrine malignancy with an annual incidence of less than 1 per 100,000 per year. Current classification scheme for PanNETs include grade and stage. While well-differentiated PanNETs can be successfully treated with surgery, there are few treatments for metastatic PanNETs. A greater understanding of the cells of origin of PanNETs, tumor progression and pathway pathogenesis may guide the development of novel therapeutic options. The most commonly mutated genes in PanNETs are ATRX, DAXX, and MEN1. Little is known about the cells-of-origin for non-functional neuroendocrine tumors. Here, we genotyped 64 PanNETs for mutations in ATRX, DAXX, and MEN1 and found 37 tumors (58%) carry mutations in these three genes (A-D-M mutant PanNETs) and this correlates with a worse clinical outcome than tumors carrying the wild-type alleles of all three genes (A-D-M WT PanNETs). We performed RNA sequencing (n=33) and Illumina 450K DNA methylation (n=32) analysis on randomly selected PanNETs to reveal two distinct subgroups with one group consisting exclusively of A-D-M mutant PanNETs. Pair-wise correlation of gene expression between all PanNETs, showed A-D-M mutant PanNETs are more homogeneous as a group than A-D-M WT PanNETs. Among A-D-M mutant PanNETs, mutants with the same genotype (mutations in ATRX/DAXX/MEN1) did not show greater gene expression correlation. Two biomarkers differentiating A-D-M mutant from A-D-M WT PanNETs were high ARX gene expression and low PDX1 gene expression with PDX1 promoter hyper-methylation in the A-D-M mutant PanNETs. Moreover, A-D-M mutant PanNETs had a gene expression signature similar to that of alpha cells (pval < 0.009) of pancreatic islets including increased expression of HNF1A and its transcriptional target genes. We validated our subtype classification and A-D-M mutant panNET alpha signature using two independent PanNETs expression dataset. This gene expression profile suggests that A-D-M mutant PanNETs originate from or transdifferentiate into a distinct cell type similar to alpha cells. Citation Format: Saurabh V. Laddha, Chang S. Chan, Peter Lewis, Matthew Koletsky, Kenneth Robzyk, Edaise Da Silva, Paula J. Torres, Brian Untch, Promita Bose, Timothy Chan, David S. Klimstra, David C. Allis, Laura H. Tang. ATRX, DAXX or MEN1 mutant pancreatic neuroendocrine tumors are a distinct “alpha-cell signature” subgroup [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 1799.

The p53 transcription factor functions as one of cancer’s most potent tumor suppressors and is the most frequently mutated gene in human cancer. The majority of p53 mutations (>70%) are missense that generate a defective protein found at high levels in cells that is targetable. Restoration of wild type structure and function of mutant p53 with a small molecule (so-called reactivation) is a highly sought after goal in anticancer drug development. The p53 protein requires the binding of a single zinc ion to fold properly, and mutations that impair the protein’s ability to bind zinc (and cause it to misfold) are highly prevalent in cancer. We recently discovered a new class of small-molecule zinc chelators named zinc metallochaperones (ZMCs) that reactivate zinc-deficient mutant p53 through a novel mechanism involving both zinc ionophore activity to raise intracellular zinc concentrations and donation to restore zinc binding to mutant p53. This induces a wild type conformation change and a p53-mediated apoptotic program. The lead compound (ZMC1) displays a transient pharmacodynamics (p21 levels) in vitro. We hypothesized that the regulation of these pharmacodynamics is governed by cellular zinc homeostatic mechanisms that function to restore zinc to its physiologic picomolar levels. We examined the entire suite of zinc homeostatic genes in response to ZMC1 and manipulated several metallothionein genes by knockout and knockdown. The net effect of this was to increase the peak and duration of intracellular zinc levels that lead to a more potent and sustained duration of p21 expression. This translated to increased sensitivity to ZMC1. We further postulated that this pharmacodynamics would allow the drug to function with very minimal exposure, and colony formation studies in vitro indicated that a 2-hour exposure was as effective as a 72-hour exposure. We then sought to translate this mechanism in vivo using a genetically engineered murine model of KPC pancreatic cancer (Pdx-1Cre; KrasG12D) that expresses either the p53R172H (zinc deficient) allele or p53R270H (non-zinc deficient). Pharmacokinetic (PK) studies of the drug revealed a short half-life (15 minutes) indicating a minimal exposure. Despite this, daily, intermittent dosing at the maximum tolerated dose resulted in a statistically significant increase in the overall survival of the KPC-p53R172H mice while having no such effect in the KPC-p53R270H. We sought to improve the efficacy of ZMC1 by preloading it with zinc in a 2:1 molar ratio based on the crystal structure. The drug-zinc complex (Zn-1) increased the median survival of KPCp53-R172H mice from 26 days to 35 days (ZMC1 monomer versus Zn-1). These studies indicate that cellular zinc homeostatic mechanisms function as an “off” switch for ZMCs, which has important implications for the translation of ZMCs in humans. Principally, this allows the drug to function with minimal exposure, which minimizes potential zinc toxicity. ZMC1 as monotherapy improves survival in an allele-specific mutant p53 manner. Furthermore, ZMC1 can be optimized by synthesizing it complexed with zinc. Overall, this “off” switch is novel for a targeted molecular therapeutic and represents a significant departure from the traditional paradigm where the goal is to develop a compound that binds the target with a PK profile that provides maximal exposure. Citation Format: Xin Yu, Samuel Kogan, Ying Chen, Ashley T. Tsang, Tracy Withers, Hongxia Lin, Chunxia Chen, Dirk F. Moore, Joseph Bertino, Chang Chan, Darren R. Carpizo. Cellular zinc homeostatic mechanisms function as an off switch for zinc metallochaperone-mediated reactivation of mutant p53 [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr B211.

The tumor suppressor p53 plays a central role in tumor prevention. The E3 ubiquitin ligase MDM2 is the most critical negative regulator of p53, which binds to p53 and degrades p53 through ubiquitation. MDM2 itself is a transcriptional target of p53, and therefore, MDM2 forms a negative feedback loop with p53 to tightly regulate p53 levels and function. microRNAs (miRNAs) play a key role in regulation of gene expression. miRNA dysregulation plays an important role in tumorigenesis. In this study, we found that miRNA miR-1827 is a novel miRNA that targets MDM2 through binding to the 3'-UTR of MDM2 mRNA. miR-1827 negatively regulates MDM2, which in turn increases p53 protein levels to increase transcriptional activity of p53 and enhance p53-mediated stress responses, including apoptosis and senescence. Overexpression of miR-1827 suppresses the growth of xenograft colorectal tumors, whereas the miR-1827 inhibitor promotes tumor growth in mice in a largely p53-dependent manner. miR-1827 is frequently down-regulated in human colorectal cancer. Decreased miR-1827 expression is associated with high MDM2 expression and poor prognosis in colorectal cancer. In summary, our results reveal that miR-1827 is a novel miRNA that regulates p53 through targeting MDM2, and highlight an important role and the underlying mechanism of miR-1827 in tumor suppression.

Germline deletion of the p53 gene in mice gives rise to spontaneous thymic (T-cell) lymphomas. In this study, the p53 knockout mouse was employed as a model to study the mutational evolution of tumorigenesis. The clonality of the T-cell repertoire from p53 knockout and wild-type thymic cells was analyzed at various ages employing TCRβ sequencing. These data demonstrate that p53 knockout thymic lymphomas arose in an oligoclonal fashion, with tumors evolving dominant clones over time. Exon sequencing of tumor DNA revealed that all of the independently derived oligoclonal mouse tumors had a deletion in the Pten gene prior to the formation of the TCRβ rearrangement, produced early in development. This was followed in each independent clone of the thymic lymphoma by the amplification or overexpression of cyclin Ds and Cdk6. Alterations in the expression of Ikaros were common and blocked further development of CD-4/CD-8 T cells. While the frequency of point mutations in the genome of these lymphomas was one per megabase, there were a tremendous number of copy number variations producing the tumors’ driver mutations. The initial inherited loss of p53 functions appeared to delineate an order of genetic alterations selected for during the evolution of these thymic lymphomas.

// Cen Zhang 1,* , Juan Liu 1,* , Rui Wu 1 , Yingjian Liang 1 , Meihua Lin 1 , Jia Liu 1 , Chang S. Chan 2 , Wenwei Hu 1 and Zhaohui Feng 1 1 Department of Radiation Oncology, Rutgers Cancer Institute of New Jersey, Rutgers, State University of New Jersey, New Brunswick, USA 2 Department of Medicine, Rutgers Cancer Institute of New Jersey, Rutgers, State University of New Jersey, New Brunswick, USA * These two authors contributed equally to this work Correspondence: Wenwei Hu, email: // Zhaohui Feng, email: // Keywords : p53, glycolysis, RRAD, hypoxia, lung cancer Received : May 17, 2014 Accepted : June 24, 2014 Published : June 26, 2014 Abstract Cancer cells display enhanced glycolysis to meet their energetic and biosynthetic demands even under normal oxygen concentrations. Recent studies have revealed that tumor suppressor p53 represses glycolysis under normoxia as a novel mechanism for tumor suppression. As the common microenvironmental stress for tumors, hypoxia drives the metabolic switch from the oxidative phosphorylation to glycolysis, which is crucial for survival and proliferation of cancer cells under hypoxia. The p53’s role and mechanism in regulating glycolysis under hypoxia is poorly understood. Here, we found that p53 represses hypoxia-stimulated glycolysis in cancer cells through RRAD, a newly-identified p53 target. RRAD expression is frequently decreased in lung cancer. Ectopic expression of RRAD greatly reduces glycolysis whereas knockdown of RRAD promotes glycolysis in lung cancer cells. Furthermore, RRAD represses glycolysis mainly through inhibition of GLUT1 translocation to the plasma membrane. Under hypoxic conditions, p53 induces RRAD, which in turn inhibits the translocation of GLUT1 and represses glycolysis in lung cancer cells. Blocking RRAD by siRNA greatly abolishes p53’s function in repressing glycolysis under hypoxia. Taken together, our results revealed an important role and mechanism of p53 in antagonizing the stimulating effect of hypoxia on glycolysis, which contributes to p53’s function in tumor suppression.

Macroautophagy (autophagy hereafter) recycles intracellular components to sustain mitochondrial metabolism that promotes the growth, stress tolerance, and malignancy of lung cancers, suggesting that autophagy inhibition may have antitumor activity. To assess the functional significance of autophagy in both normal and tumor tissue, we conditionally deleted the essential autophagy gene, autophagy related 7 (Atg7), throughout adult mice. Here, we report that systemic ATG7 ablation caused susceptibility to infection and neurodegeneration that limited survival to 2 to 3 months. Moreover, upon fasting, autophagy-deficient mice suffered fatal hypoglycemia. Prior autophagy ablation did not alter the efficiency of non–small cell lung cancer (NSCLC) initiation by activation of oncogenic KrasG12D and deletion of the Trp53 tumor suppressor. Acute autophagy ablation in mice with preexisting NSCLC, however, blocked tumor growth, promoted tumor cell death, and generated more benign disease (oncocytomas). This antitumor activity occurred before destruction of normal tissues, suggesting that acute autophagy inhibition may be therapeutically beneficial in cancer. Significance: We systemically ablated cellular self-cannibalization by autophagy in adult mice and determined that it is dispensable for short-term survival, but required to prevent fatal hypoglycemia and cachexia during fasting, delineating a new role for autophagy in metabolism. Importantly, acute, systemic autophagy ablation was selectively destructive to established tumors compared with normal tissues, thereby providing the preclinical evidence that strategies to inhibit autophagy may be therapeutically advantageous for RAS-driven cancers., Val Skinner Foundation, National Institutes of Health (U.S.) (RC1 CA147961), Rutgers Cancer Institute of New Jersey, Rutgers Cancer Institute of New Jersey (P30 CA072720), National Institutes of Health (U.S.) (R01 CA163591), National Institutes of Health (U.S.) (R37 CA53370), National Institutes of Health (U.S.) (R01 CA130893)

Evidence suggests that the catabolic process of macroautophagy (autophagy hereafter) can either suppress or promote cancer. The essential autophagy gene ATG6/BECN1 encoding the Beclin1 protein has been implicated as a haploinsufficient tumor suppressor in breast, ovarian, and prostate cancers. The proximity of BECN1 to the known breast and ovarian tumor suppressor breast cancer 1, early onset, BRCA1, on chromosome 17q21, has made this determination equivocal. Here, the mutational status of BECN1 was assessed in human tumor sequencing data from The Cancer Genome Atlas (TCGA) and other databases. Large deletions encompassing both BRCA1 and BECN1, and deletions of only BRCA1 but not BECN1, were found in breast and ovarian cancers, consistent with BRCA1 loss being a primary driver mutation in these cancers. Furthermore, there was no evidence for BECN1 mutation or loss in any other cancer, casting doubt on whether BECN1 is a tumor suppressor in most human cancers. Implications: Contrary to previous reports, BECN1 is not significantly mutated in human cancer and not a tumor-suppressor gene, as originally thought. Visual Overview: http://mcr.aacrjournals.org/content/early/2014/04/01/1541-7786.MCR-13-0614/F1.large.jpg. Mol Cancer Res; 12(4); 485–90. ©2014 AACR.

Sagne, Charlotte Marcel, Virginie Bota, Maria Martel-Planche, Ghyslaine Nobrega, Amanda Palmero, Edenir Inez Perriaud, Laury Boniol, Mathieu Vagner, Stephan Cox, David G Chan, Chang S Mergny, Jean-Louis Olivier, Magali Ashton-Prolla, Patricia Hall, Janet Hainaut, Pierre Achatz, Maria Isabel eng England 2013/12/18 06:00 Carcinogenesis. 2014 Apr;35(4):807-15. doi: 10.1093/carcin/bgt381. Epub 2013 Dec 11.; International audience; Germline TP53 mutations predispose to multiple cancers defining Li-Fraumeni/Li-Fraumeni-like syndrome (LFS/LFL), a disease with large individual disparities in cancer profiles and age of onset. G-quadruplexes (G4s) are secondary structural motifs occurring in guanine tracks, with regulatory effects on DNA and RNA. We analyzed 85 polymorphisms within or near five predicted G4s in TP53 in search of modifiers of penetrance of LFS/LFL in Brazilian cancer families with (n = 35) or without (n = 110) TP53 mutations. Statistical analyses stratified on family structure showed that cancer tended to occur ~15 years later in mutation carriers who also carried the variant alleles of two polymorphisms within predicted G4-forming regions, rs17878362 (TP53 PIN3, 16 bp duplication in intron 3; P = 0.082) and rs17880560 (6 bp duplication in 3' flanking region; P = 0.067). Haplotype analysis showed that this inverse association was driven by the polymorphic status of the remaining wild-type (WT) haplotype in mutation carriers: in carriers with a WT haplotype containing at least one variant allele of rs17878362 or rs17880560, cancer occurred ~15 years later than in carriers with other WT haplotypes (P = 0.019). No effect on age of cancer onset was observed in subjects without a TP53 mutation. The G4 in intron 3 has been shown to regulate alternative p53 messenger RNA splicing, whereas the biological roles of predicted G4s in the 3' flanking region remain to be elucidated. In conclusion, this study demonstrates that G4 polymorphisms in haplotypes of the WT TP53 allele have an impact on LFS/LFL penetrance in germline TP53 mutation carriers.

Pancreatic neuroendocrine tumors are generally classified as functioning or nonfunctioning. Patients with functioning tumors can have severe hypoglycemia because their tumors express high amounts of insulin as well as chromogranin A; fortunately, these tumors are seldom metastatic. Patients with nonfunctioning tumors express high amounts of chromogranin A but little insulin; unfortunately these tumors are highly metastatic to the liver. Nonfunctioning tumors are more common, and a more severe health issue. The highly studied RT2 B6 mouse, in which the SV40 T antigen is expressed from an insulin promoter in an inbred C57Bl/6 genetic background, is a model for functioning pancreatic neuroendocrine tumors: liver metastasis is uncommon in RT2 B6 mice, which are very hypoglycemic and often die when tumors are very small. We have changed the genetic background and are studying RT2 AB6F1 hybrid mice, which have a C57Bl/6 father and a mother from an A/J inbred background. RT2 AB6F1 mice are much less hypoglycemic, and these mice develop liver metastasis with high frequency. We have mated the hybrid AB6F1 mice to their littermates in order to map metastasis genes by F2 analysis, and have discovered that a locus at mouse chromosome 2qG1 links tightly to liver metastasis. One gene within this locus, InsM1, is less expressed in the primary tumors of mice with liver metastatic disease. InsM1 is also less expressed in primary tumors from humans with liver metastatic disease. Previous studies of InsM1 have shown that this protein maintains the differentiated status of pancreatic beta cells. We find that tumors from mice with low expression of InsM1 also express lower amounts of several distinctive markers of differentiated beta cells, but higher amounts of several markers of liver cells. These data suggest that dedifferentiation to stem cells, which can then redifferentiate to other cell types such as liver cells, promotes metastasis of pancreatic beta cell tumors. Intratumoral expression of liver markers may be a useful predictor of metastatic disease in these patients. Dedifferentiation of mature beta cells is also a mechanism by which type 2 diabetes occurs, so there may be similarities between these two diseases. Citation Format: Tanupriya Contractor, Shinta Kobayashi, Richard Clausen, Edaise da Silva, Laura Tang, Chang Chan, Chris R. Harris. A mouse model for highly metastatic, nonfunctioning pancreatic neuroendocrine tumors. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 478.

Distal enhancers have recently emerged as a common mode of gene regulation for several transcription factors, including estrogen and androgen receptors, the two key regulators of breast and prostate cancer major subtypes. Despite the rapid success in genome-wide annotation of estrogen receptor-α (ERα) binding sites in cell lines, the precise mechanism governing the gene-to-enhancer association is still unknown and no quantitative model that can predict the estrogen responsiveness of genes has been hitherto proposed. This article presents an integrative genomics approach to construct a predictive model that can explain more than 70% of estrogen-induced expression profiles. The proposed method combines a recent map of the insulator protein CCCTC-binding factor (CTCF) with previous ER location studies and expression profiling in the presence of the translation inhibitor cycloheximide, providing evidence that CTCF partitions the human genome into distinct ER-regulatory blocks. It is shown that estrogen-responsive genes with a decreased transcription level (down-regulated genes) have a markedly different relative distribution of ER binding sites compared with those with an increased transcription level (up-regulated genes). Finally, Bayesian belief networks are constructed to quantify the effects of ER-binding distance from genes as well as the insulating effects of CTCF on the estrogen responsiveness of genes. This work thus represents a stride toward understanding and predicting the distal activities of steroid hormone nuclear receptors. [Cancer Res 2008;68(21):9041–9]

Among patients with neuroendocrine tumors, males are more likely than females to develop liver metastatic disease. We show that this male bias toward liver metastasis is also observed in a mouse model for pancreatic neuroendocrine tumorigenesis (PanNETs). Interestingly, primary tumors from mice with metastatic disease display hepatomimicry, expressing genes normally expressed in liver. Both male and female primary tumors from mice with metastatic disease show hepatomimicry, although one of the liver genes, complement C5, is only induced in males. In mice knocked out for the complement C5 gene, the frequency of liver metastasis dropped significantly; moreover, males and females lacking a gene for complement C5 developed liver metastasis at the same frequency. Liver metastasis was also prevented by PMX53, a small molecule antagonist of C5aR1/CD88, which is the receptor for complement C5a. Thus complement C5 is epistatic to metastasis and promotes gender bias of liver metastatic disease. Citation Format: Tanupriya Contractor, Chang Chan, Shinta Kobayashi, Richard Clausen, Yvonne Sun, Edaise da Silva, Evan Vosburgh, Arnold J. Levine, Laura Tang, Chris R. Harris. Complement C5 promotes male bias of pancreatic neuroendocrine tumor metastasis. [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 3185. doi:10.1158/1538-7445.AM2015-3185

Patients with adenocarcinoma of the pancreas were treated using a combination of EUS-guided intrapancreatic tumor injection and systemic boost using PANVAC-F and PANVAC-V in this first-in-man Phase I trial. The study represents the translation of our unique demonstration in murine models of bladder and orthotopic mammary tumors that anergy to systemic immunization using antigen encoding vaccinia recombinants could be overcome by immunization into the tumor microenvironment. Consented patients with locally advanced or minimally metastatic pancreatic cancer received EUS-guided intrapancreatic injections (IT) of recombinant Panvac-F (Fowlpox encoding MUC-1, CEA, TRICOM), systemic subcutaneous (SC) Panvac-V (vaccinia) and SC Panvac-F boosts. Systemic SC vaccines were accompanied by subcutaneous rH-GM-CSF, 100 mcg X 4 days. Patients received 2 intrapancreatic injections of Panvac-F (2 weeks apart) with systemic Panvac-V and Panvac-F boosts given with GMCSF extending to day 71 (total of 2 IT Panvac-F, 1 SC Panvac-V, 4 SC Panvac-F). Patients were allowed to transition to standard care at day 31. Patients were evaluated for toxicity and tumor progression. Follow-up care was provided by referring oncologists. In this dose escalation study, the first cohort of 6 pts received IT Panvac-F (10 8 PFU), SC Panvac-V (2 X 10 8 PFU), and SC Panvac-F (10 9 PFU). The second dose cohort of 8 pts received IT Panvac-F (10 9 PFU), SC Panvac-V (2 X 10 8 PFU), and SC Panvac-F (10 9 PFU ). At dose level 1, two of six patients were removed from study after approximately two weeks due to rapid disease progression and died one and six months after trial initiation. At dose level 2, one patient was removed due to rapidly progressive disease and died at 1 mo and a second patient withdrew following 1 IT inoculation and died at month 16. Of the remaining 10 pts, 3 presented with distant metastatic disease (Median Survival 7 mos, range 1-25) and 7 presented without distant metastases (Median Survival 16 mos, range 3-35). Of note, none of the 7 patients presenting without metastatic disease developed distant visceral metastases, by imaging available to us but died of sequellae associated with progressive local disease. Of the above 10 pts, all but one transitioned initially to treatment with gemcitabine-based therapy. (the remaining pt did not begin systemic treatment). Initial RNAseq transcriptome analysis of Fine Needle Aspirate (FNA) comparing Day 1 and Day 14 samples demonstrated a significant increase in a series of chemokines associated with the induction of an immune response in the tumor microenvironment. A planned series of immunologic and genetic analyses are underway. Results demonstrate that the “first in man” intrapancreatic administration of recombinant poxvirus was well tolerated with the complete regimen suggesting an encouraging period of stable disease. The finding that none of the patients who presented without distant visceral metastases developed such would be consistent with the generation of a systemic immune response with effects on seeded metastatic cells. Analysis of local and systemic immune responses is currently proceeding and may provide further insights. This study is supported by the NCI Cancer Therapeutics Evaluation Program (CTEP) and by NCI U01-CA07031 and P30-CA72720. Citation Format: Elizabeth A. Poplin, David A. August, Rebecca A. Moss, Tamir Ben-Menachem, Hazar Michael, Aparna Repaka, Renee Artymyshyn, Chang Chan, James L. Gulley, Robert S. DiPaola, Edmund C. Lattime. Panvac-F and Panvac-V: Phase I study of intratumoral and systemic vaccination. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Innovations in Research and Treatment; May 18-21, 2014; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2015;75(13 Suppl):Abstract nr B100.

Endogenous c-MYC (MYC) has been reported to be a potential pharmacological target to trigger ubiquitous tumor regression of pancreatic neuroendocrine tumors (PanNETs) and lung tumors. Recently inhibitors of bromodomain and extra-terminal (BET) family proteins have shown antitumor effects through the suppression of MYC in leukemia and lymphoma. In this paper, we investigated the antitumor activity of a BET protein bromodomain inhibitor (BETi) CPI203 as a single agent and in combination with rapamycin in human PanNETs. We found that exposure of human PanNET cell lines to CPI203 led to downregulation of MYC expression, G1 cell cycle arrest and nearly complete inhibition of cell proliferation. In addition, overexpression of MYC suppressed the growth inhibition caused by CPI203 and knockdown of MYC phenocopied the effects of CPI203 treatment. These findings indicate that suppression of MYC contributed to the antiproliferative effects of BETi inhibition in human PanNET cells. Importantly, CPI203 treatment enhanced the antitumor effects of rapamycin in PanNET cells grown in monolayer and in three-dimensional cell cultures, as well as in a human PanNET xenograft model in vivo. Furthermore, the combination treatment attenuated rapamycin-induced AKT activation, a major limitation of rapamycin therapy. Collectively, our data suggest that targeting MYC with a BETi may increase the therapeutic benefits of rapalogs in human PanNET patients. This provides a novel clinical strategy for PanNETs, and possibly for other tumors as well.

Loss of the tumor suppressor, p53, occurs in over 50% of cancers. The ability for p53 to protect the cell from tumorigenesis is based on its ability to induce cell cycle arrest, apoptosis, and senescence following genotoxic stress. Furthermore, genetic deletion of p53 in mice gives rise to spontaneous thymic (T-cell) lymphomas and sarcomas. In this study, we used the p53-knockout (KO) mouse as a model for progression of tumorigenesis. We first analyzed genomic DNA of p53-KO and WT normal thymus at various ages and p53-KO thymic lymphomas using TCRβ sequencing, allowing us to determine the clonality of the T cell repertoire. These data suggest that p53-KO thymic lymphomas were mostly oligoclonal, with some tumors comprising of a dominant clone. We further analyzed tumors with dominant clones for genomic instability by exome sequencing. Sequencing analysis revealed that there were many non-synonymous mutations occurring in each tumor, but with no similarities between tumors. On the other hand, all of the murine tumors had deletion of Pten and amplification of Cdk6. This is in stark contrast to what is seen in most human T cell lymphoblastic leukemias, which have activating mutations in Notch1 and loss of Arf. Interestingly, loss of Pten not only occurred in all tumors, but also in most, if not all, clones in the tumor. This suggests that Pten loss is an early event driving T cell transformation in a p53-KO background. Using this data, we found the somatic mutation rate in the tumors to be 1000-fold greater than the germline mutation rate. Loss of p53 also caused chromosomal abnormalities as seen with increased copy number variations. Taken together, our work suggests that, with initial loss of p53, the path to T cell tumorigenesis is vastly different from that of human tumors. Without p53, the somatic genome increases in mutation rate and copy number variations, thus solidifying p53's role as guardian of the genome. Citation Format: Crissy Dudgeon, Chang Chan, Yvonne Sun, Arnold J. Levine. Exome sequencing of murine p53-knockout T-cell lymphomas reveals Pten loss and Cdk6 amplification as key steps toward cellular transformation. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr LB-80. doi:10.1158/1538-7445.AM2014-LB-80