Tumor Metabolism and Neurocognition in CNS Lymphoma

BACKGROUND

The mechanistic basis for neurocognitive deficits in CNS lymphoma and other brain tumors is incompletely understood. We tested the hypothesis that tumor metabolism impairs neurotransmitter pathways and neurocognitive function.

METHODS

We performed serial cerebrospinal fluid (CSF) metabolomic analyses using liquid chromatography-electrospray tandem mass spectrometry to evaluate changes in the tumor microenvironment in 14 patients with recurrent CNS lymphoma, focusing on 18 metabolites involved in neurotransmission and bioenergetics. These were paired with serial mini-mental state examinations (MMSE) and MRI studies for tumor volumetric analyses. Patients were analyzed in the setting of the phase I trial of lenalidomide/rituximab. Associations were assessed by Pearson and Spearman correlation coefficient. Generalized estimating equation (gee) models were also established, adjusting for within-subject repeated measures.

RESULTS

Of 18 metabolites, elevated CSF lactate correlated most strongly with lower MMSE score (p<8E-8, rho=-0.67). High lactate was associated with lower GABA, higher glutamate/GABA ratio and dopamine. Conversely, high succinate correlated with higher MMSE score. Serial analysis demonstrated a reproducible, time-dependent, reciprocal correlation between changes in lactate and GABA concentrations. While high lactate and low GABA correlated with tumor contrast enhancing volume, they correlated more significantly with lower MMSE scores than tumor volumes.

CONCLUSIONS

We provide evidence that lactate production and Warburg metabolism may impact neurotransmitter dysregulation and neurocognition in CNS lymphomas. We identify novel metabolomic biomarkers that may be applied in future studies of neurocognition in CNS lymphomas. Elucidation of mechanistic interactions between lymphoma metabolism, neurotransmitter imbalance and neurocognition may promote interventions that preserve cognitive function.

Congenital superior mesenteric artery aneurysm in a 6-week-old infant presenting with upper gastrointestinal bleeding

Visceral artery aneurysms are rare in infants and children. The majority of cases are caused by genetic syndromes, trauma, or infection. Although the majority of aneurysms are asymptomatic, visceral artery aneurysms can present with abdominal pain, nausea/vomiting, or rupture. Aneurysm rupture can manifest as hemodynamic instability and/or gastrointestinal bleeding. We present the case of a congenital idiopathic aneurysm of the superior mesenteric artery in a 6-week-old infant who presented with gastrointestinal bleeding. We report a stepwise surgical approach to achieving aneurysm exclusion and thrombosis, and highlight the robust mesenteric collateral circulation that can develop in pediatric patients.

Transcriptional control of subtype switching ensures adaptation and growth of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDA) is a heterogeneous disease comprised of a basal-like subtype with mesenchymal gene signatures, undifferentiated histopathology and worse prognosis compared to the classical subtype. Despite their prognostic and therapeutic value, the key drivers that establish and control subtype identity remain unknown. Here, we demonstrate that PDA subtypes are not permanently encoded, and identify the GLI2 transcription factor as a master regulator of subtype inter-conversion. GLI2 is elevated in basal-like PDA lines and patient specimens, and forced GLI2 activation is sufficient to convert classical PDA cells to basal-like. Mechanistically, GLI2 upregulates expression of the pro-tumorigenic secreted protein, Osteopontin (OPN), which is especially critical for metastatic growth in vivo and adaptation to oncogenic KRAS ablation. Accordingly, elevated GLI2 and OPN levels predict shortened overall survival of PDA patients. Thus, the GLI2-OPN circuit is a driver of PDA cell plasticity that establishes and maintains an aggressive variant of this disease.

Abstract A43: Loss of Keap1 promotes KRAS-driven lung cancer and results in genotype-specific vulnerabilities

Treating KRAS mutant lung adenocarcinoma (LUAD) remains a major challenge in cancer treatment given the difficulties associated with directly inhibiting the KRAS oncoprotein1. One approach to addressing this challenge is to define frequently co-occurring mutations with KRAS, which themselves may lead to therapeutic vulnerabilities in tumors. Approximately 20% of KRAS mutant LUAD tumors carry loss-of-function (LOF) mutations in Kelch-like ECH-associated protein 1 (KEAP1)2-4, a negative regulator of nuclear factor erythroid 2-like 2 (NFE2L2; hereafter NRF2), which is the master transcriptional regulator of the endogenous antioxidant response5-10. The high frequency of mutations in KEAP1, which would be predicted to result in activation of the NRF2 pathway, suggests an important role for the oxidative stress response in lung tumorigenesis. To test this directly, we used a CRISPR/Cas9-based approach in a mouse model of Kras-driven LUAD to examine the effects of loss of KEAP1 function in lung cancer progression. We show that loss of KEAP1 hyper-activates Nrf2 and promotes Kras-driven LUAD. Combining CRISPR/Cas9-based genetic screening and metabolomic analyses, we also show that KEAP1/NRF2 mutant cancers are dependent on increased glutaminolysis, and this property can be therapeutically exploited through the pharmacologic inhibition of glutaminase. Finally, we provide a rationale for sub-stratification of human lung cancer patients with KRAS-KEAP1 or -NRF2 mutant tumors as likely to respond to glutaminase inhibition.

Citation Format: Rodrigo Romero, Volkan I. Sayin, Davidson M. Shawn, Matthew Bauer, Simranjit X. Singh, Sarah LeBoeuf, Triantafyllia R. Karakousi, Donald C. Ellis, Arjun Bhutkar, Francisco Sanchez-Rivera, Lakshmipriya Subbaraj, Britney Martinez, Roderick T. Bronson, Justin R. Prigge, Edward E. Schmidt, Craig J. Thomas, Angela Davies, Igor Dolgalev, Adriana Heguy, Viola Allaj, John T. Piorier, Andre L. Moreira, Charles M. Rudin, Harvey I. Pass, Matthew G. Vander Heiden, Tyler Jacks, Thales Papagiannakopoulos. Loss of Keap1 promotes KRAS-driven lung cancer and results in genotype-specific vulnerabilities [abstract]. In: Proceedings of the AACR Special Conference: Advances in Modeling Cancer in Mice: Technology, Biology, and Beyond; 2017 Sep 24-27; Orlando, Florida. Philadelphia (PA): AACR; Cancer Res 2018;78(10 Suppl):Abstract nr A43.

Circadian Rhythm Disruption Promotes Lung Tumorigenesis

Circadian rhythms are 24-hr oscillations that control a variety of biological processes in living systems, including two hallmarks of cancer, cell division and metabolism. Circadian rhythm disruption by shift work is associated with greater risk for cancer development and poor prognosis, suggesting a putative tumor-suppressive role for circadian rhythm homeostasis. Using a genetically engineered mouse model of lung adenocarcinoma, we have characterized the effects of circadian rhythm disruption on lung tumorigenesis. We demonstrate that both physiologic perturbation (jet lag) and genetic mutation of the central circadian clock components decreased survival and promoted lung tumor growth and progression. The core circadian genes Per2 and Bmal1 were shown to have cell-autonomous tumor-suppressive roles in transformation and lung tumor progression. Loss of the central clock components led to increased c-Myc expression, enhanced proliferation, and metabolic dysregulation. Our findings demonstrate that both systemic and somatic disruption of circadian rhythms contribute to cancer progression.

Rapid modelling of cooperating genetic events in cancer through somatic genome editing

Cancer is a multistep process that involves mutations and other alterations in oncogenes and tumour suppressor genes. Genome sequencing studies have identified a large collection of genetic alterations that occur in human cancers. However, the determination of which mutations are causally related to tumorigenesis remains a major challenge. Here we describe a novel CRISPR/Cas9-based approach for rapid functional investigation of candidate genes in well-established autochthonous mouse models of cancer. Using a Kras(G12D)-driven lung cancer model, we performed functional characterization of a panel of tumour suppressor genes with known loss-of-function alterations in human lung cancer. Cre-dependent somatic activation of oncogenic Kras(G12D) combined with CRISPR/Cas9-mediated genome editing of tumour suppressor genes resulted in lung adenocarcinomas with distinct histopathological and molecular features. This rapid somatic genome engineering approach enables functional characterization of putative cancer genes in the lung and other tissues using autochthonous mouse models. We anticipate that this approach can be used to systematically dissect the complex catalogue of mutations identified in cancer genome sequencing studies.