Faculty Bibliography
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125
Novel heteroclitic XBP1 peptides induce antigen-specific memory CD3+CD8+T cells expressing critical T cell markers and transcription regulators [Meeting Abstract]
ISI:000349906904160
ISSN: 1538-7445
CID: 1845022
Efficacy of BET bromodomain inhibition in Kras-mutant non-small cell lung cancer
PURPOSE: Amplification of MYC is one of the most common genetic alterations in lung cancer, contributing to a myriad of phenotypes associated with growth, invasion, and drug resistance. Murine genetics has established both the centrality of somatic alterations of Kras in lung cancer, as well as the dependency of mutant Kras tumors on MYC function. Unfortunately, drug-like small-molecule inhibitors of KRAS and MYC have yet to be realized. The recent discovery, in hematologic malignancies, that bromodomain and extra-terminal (BET) bromodomain inhibition impairs MYC expression and MYC transcriptional function established the rationale of targeting KRAS-driven non-small cell lung cancer (NSCLC) with BET inhibition. EXPERIMENTAL DESIGN: We performed functional assays to evaluate the effects of JQ1 in genetically defined NSCLC cell lines harboring KRAS and/or LKB1 mutations. Furthermore, we evaluated JQ1 in transgenic mouse lung cancer models expressing mutant kras or concurrent mutant kras and lkb1. Effects of bromodomain inhibition on transcriptional pathways were explored and validated by expression analysis. RESULTS: Although JQ1 is broadly active in NSCLC cells, activity of JQ1 in mutant KRAS NSCLC is abrogated by concurrent alteration or genetic knockdown of LKB1. In sensitive NSCLC models, JQ1 treatment results in the coordinate downregulation of the MYC-dependent transcriptional program. We found that JQ1 treatment produces significant tumor regression in mutant kras mice. As predicted, tumors from mutant kras and lkb1 mice did not respond to JQ1. CONCLUSION: Bromodomain inhibition comprises a promising therapeutic strategy for KRAS-mutant NSCLC with wild-type LKB1, via inhibition of MYC function. Clinical studies of BET bromodomain inhibitors in aggressive NSCLC will be actively pursued. Clin Cancer Res; 19(22); 6183-92. (c)2013 AACR.
PMCID:3838895
PMID: 24045185
ISSN: 1078-0432
CID: 1844022
Metabolic and functional genomic studies identify deoxythymidylate kinase as a target in LKB1-mutant lung cancer
The LKB1/STK11 tumor suppressor encodes a serine/threonine kinase, which coordinates cell growth, polarity, motility, and metabolism. In non-small cell lung carcinoma, LKB1 is somatically inactivated in 25% to 30% of cases, often concurrently with activating KRAS mutations. Here, we used an integrative approach to define novel therapeutic targets in KRAS-driven LKB1-mutant lung cancers. High-throughput RNA interference screens in lung cancer cell lines from genetically engineered mouse models driven by activated KRAS with or without coincident Lkb1 deletion led to the identification of Dtymk, encoding deoxythymidylate kinase (DTYMK), which catalyzes dTTP biosynthesis, as synthetically lethal with Lkb1 deficiency in mouse and human lung cancer lines. Global metabolite profiling showed that Lkb1-null cells had a striking decrease in multiple nucleotide metabolites as compared with the Lkb1-wild-type cells. Thus, LKB1-mutant lung cancers have deficits in nucleotide metabolism that confer hypersensitivity to DTYMK inhibition, suggesting that DTYMK is a potential therapeutic target in this aggressive subset of tumors.
PMCID:3753578
PMID: 23715154
ISSN: 2159-8290
CID: 1844122
Pancreatic cancers rely on a novel glutamine metabolism pathway to maintain redox balance [Editorial]
PMCID:3737294
PMID: 23759579
ISSN: 1551-4005
CID: 1844182
PARI overexpression promotes genomic instability and pancreatic tumorigenesis
Treatment options for patients with pancreatic ductal adenocarcinoma (PDAC) remain limited. Therapeutic targets of interest include mutated molecules that predispose to pancreatic cancer such as KRAS and TP53. Here, we show that an element of the homologous recombination pathway of DNA repair, the PARP-binding protein C12orf48/PARI (PARPBP), is overexpressed specifically in pancreatic cancer cells where it is an appealing candidate for targeted therapy. PARI upregulation in pancreatic cancer cells or avian DT40 cells conferred DNA repair deficiency and genomic instability. Significantly, PARI silencing compromised cancer cell proliferation in vitro, leading to cell-cycle alterations associated with S-phase delay, perturbed DNA replication, and activation of the DNA damage response pathway in the absence of DNA damage stimuli. Conversely, PARI overexpression produced tolerance to DNA damage by promoting replication of damaged DNA. In a mouse xenograft model of pancreatic cancer, PARI silencing was sufficient to reduce pancreatic tumor growth in vivo. Taken together, our findings offered a preclinical proof-of-concept for PARI as candidate therapeutic target to treat PDAC.
PMCID:3630264
PMID: 23436799
ISSN: 1538-7445
CID: 1844202
SIRT4 has tumor-suppressive activity and regulates the cellular metabolic response to DNA damage by inhibiting mitochondrial glutamine metabolism
DNA damage elicits a cellular signaling response that initiates cell cycle arrest and DNA repair. Here, we find that DNA damage triggers a critical block in glutamine metabolism, which is required for proper DNA damage responses. This block requires the mitochondrial SIRT4, which is induced by numerous genotoxic agents and represses the metabolism of glutamine into tricarboxylic acid cycle. SIRT4 loss leads to both increased glutamine-dependent proliferation and stress-induced genomic instability, resulting in tumorigenic phenotypes. Moreover, SIRT4 knockout mice spontaneously develop lung tumors. Our data uncover SIRT4 as an important component of the DNA damage response pathway that orchestrates a metabolic block in glutamine metabolism, cell cycle arrest, and tumor suppression.
PMCID:3650305
PMID: 23562301
ISSN: 1878-3686
CID: 1844272
Glutamine supports pancreatic cancer growth through a KRAS-regulated metabolic pathway
Cancer cells have metabolic dependencies that distinguish them from their normal counterparts. Among these dependencies is an increased use of the amino acid glutamine to fuel anabolic processes. Indeed, the spectrum of glutamine-dependent tumours and the mechanisms whereby glutamine supports cancer metabolism remain areas of active investigation. Here we report the identification of a non-canonical pathway of glutamine use in human pancreatic ductal adenocarcinoma (PDAC) cells that is required for tumour growth. Whereas most cells use glutamate dehydrogenase (GLUD1) to convert glutamine-derived glutamate into alpha-ketoglutarate in the mitochondria to fuel the tricarboxylic acid cycle, PDAC relies on a distinct pathway in which glutamine-derived aspartate is transported into the cytoplasm where it can be converted into oxaloacetate by aspartate transaminase (GOT1). Subsequently, this oxaloacetate is converted into malate and then pyruvate, ostensibly increasing the NADPH/NADP(+) ratio which can potentially maintain the cellular redox state. Importantly, PDAC cells are strongly dependent on this series of reactions, as glutamine deprivation or genetic inhibition of any enzyme in this pathway leads to an increase in reactive oxygen species and a reduction in reduced glutathione. Moreover, knockdown of any component enzyme in this series of reactions also results in a pronounced suppression of PDAC growth in vitro and in vivo. Furthermore, we establish that the reprogramming of glutamine metabolism is mediated by oncogenic KRAS, the signature genetic alteration in PDAC, through the transcriptional upregulation and repression of key metabolic enzymes in this pathway. The essentiality of this pathway in PDAC and the fact that it is dispensable in normal cells may provide novel therapeutic approaches to treat these refractory tumours.
PMCID:3656466
PMID: 23535601
ISSN: 1476-4687
CID: 1844062
DNA damage enhancement from gold nanoparticles for clinical MV photon beams
In this study, we quantify the relative damage enhancement due to the presence of gold nanoparticles (GNP) in vitro in a clinical 6 MV beam for various delivery parameters and depths. It is expected that depths and delivery modes that produce a larger proportions of low-energy photons will have a larger effect on the cell samples containing GNP. HeLa cells with and without 50 nm GNP were irradiated at depths of 1.5, 5, 10, 15 and 20 cm. Conventional beams with square aperture sizes 5, 10 and 15 cm at isocenter, and flattening filter free (FFF) beams were used. Relative DNA damage enhancement with GNP was evaluated by gamma-H2AX staining. Statistically significant increases in DNA damage with GNP, compared to the absence of GNP, were observed for all depths and delivery modes. Relative to the shallowest depth, damage enhancement was observed to increase as a function of increasing depth for all deliveries. For the conventional (open field) delivery, DNA damage enhancement with GNP was seen to increase as a function of field size. For FFF delivery, a substantial increase in enhancement was found relative to the conventional field delivery. The measured relative DNA damage enhancement validates the theoretically predicted trends as a function of depth and delivery mode for clinical MV photon beams. The results of this study open new possibilities for the clinical development of gold nanoparticle-aided radiation therapy.
PMCID:3525114
PMID: 23148509
ISSN: 1938-5404
CID: 1843992
Oncogenic Kras maintains pancreatic tumors through regulation of anabolic glucose metabolism
Tumor maintenance relies on continued activity of driver oncogenes, although their rate-limiting role is highly context dependent. Oncogenic Kras mutation is the signature event in pancreatic ductal adenocarcinoma (PDAC), serving a critical role in tumor initiation. Here, an inducible Kras(G12D)-driven PDAC mouse model establishes that advanced PDAC remains strictly dependent on Kras(G12D) expression. Transcriptome and metabolomic analyses indicate that Kras(G12D) serves a vital role in controlling tumor metabolism through stimulation of glucose uptake and channeling of glucose intermediates into the hexosamine biosynthesis and pentose phosphate pathways (PPP). These studies also reveal that oncogenic Kras promotes ribose biogenesis. Unlike canonical models, we demonstrate that Kras(G12D) drives glycolysis intermediates into the nonoxidative PPP, thereby decoupling ribose biogenesis from NADP/NADPH-mediated redox control. Together, this work provides in vivo mechanistic insights into how oncogenic Kras promotes metabolic reprogramming in native tumors and illuminates potential metabolic targets that can be exploited for therapeutic benefit in PDAC.
PMCID:3472002
PMID: 22541435
ISSN: 1097-4172
CID: 1844162
Guidelines for the use and interpretation of assays for monitoring autophagy [Guideline]
In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process vs. those that measure flux through the autophagy pathway (i.e., the complete process); thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from stimuli that result in increased autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field.
PMCID:3404883
PMID: 22966490
ISSN: 1554-8627
CID: 181862
