Metabolic reprogramming of tumor-associated macrophages by collagen turnover promotes fibrosis in pancreatic cancer
SignificanceThe highly desmoplastic and immunosuppressive microenvironment of pancreatic tumors is a major determinant of the aggressive nature and therapeutic resistance of pancreatic cancer. Therefore, improving our understanding of the mechanisms that regulate the composition and function of the pancreatic tumor microenvironment is critical for the design of intervention strategies for this devastating malignancy. This study identifies a modality for the reprogramming of tumor-associated macrophages involving collagen scavenging followed by a metabolic switch toward a profibrotic paracrine phenotype. These findings establish a molecular framework for the elucidation of regulatory processes that could be harnessed to mitigate the stroma-dependent protumorigenic effects in pancreatic cancer.
Precision medicine in pancreatic cancer: Patient derived organoid pharmacotyping is a predictive biomarker of clinical treatment response
RATIONALE/BACKGROUND:Patient-derived organoids (PDOs) are a promising technology to support precision medicine initiatives for patients with pancreatic ductal adenocarcinoma (PDAC). PDOs may improve clinical next-generation sequencing (NGS) and enable rapid ex vivo chemotherapeutic screening (pharmacotyping). METHODS:PDOs were derived from tissues obtained during surgical resection and endoscopic biopsies and studied with NGS and pharmacotyping. PDO-specific pharmacotype is assessed prospectively as a predictive biomarker of clinical therapeutic response by leveraging data from a randomized-controlled clinical trial. RESULTS:Clinical sequencing pipelines often fail to detect PDAC-associated somatic mutations in surgical specimens that demonstrate a good pathological response to previously administered chemotherapy. Sequencing the PDOs derived from these surgical specimens, after biomass expansion, improves the detection of somatic mutations and enables quantification of copy number variants. The detection of clinically relevant mutations and structural variants is improved following PDO biomass expansion. On clinical trial, PDOs were derived from biopsies of treatment naÃ¯ve patients prior to treatment with FOLFIRINOX (FFX). Ex vivo PDO pharmacotyping with FFX components predicted clinical therapeutic response in these patients with borderline resectable or locally advanced PDAC treated in a neoadjuvant or induction paradigm. PDO pharmacotypes suggesting sensitivity to FFX components were associated with longitudinal declines of tumor marker, CA-19-9 and favorable RECIST imaging response. CONCLUSION/CONCLUSIONS:PDOs establishment from tissues obtained from patients previously receiving cytotoxic chemotherapies can be accomplished in a clinically-certified laboratory. Sequencing PDOs following biomass expansion improves clinical sequencing quality. High in-vitro sensitivity to standard-of-care chemotherapeutics predicts good clinical response to systemic chemotherapy in PDAC.
USP21 deubiquitinase elevates macropinocytosis to enable oncogenic KRAS bypass in pancreatic cancer
Activating mutations in KRAS (KRAS*) are present in nearly all pancreatic ductal adenocarcinoma (PDAC) cases and critical for tumor maintenance. By using an inducible KRAS* PDAC mouse model, we identified a deubiquitinase USP21-driven resistance mechanism to anti-KRAS* therapy. USP21 promotes KRAS*-independent tumor growth via its regulation of MARK3-induced macropinocytosis, which serves to maintain intracellular amino acid levels for anabolic growth. The USP21-mediated KRAS* bypass, coupled with the frequent amplification of USP21 in human PDAC tumors, encourages the assessment of USP21 as a novel drug target as well as a potential parameter that may affect responsiveness to emergent anti-KRAS* therapy.
The polar oxy-metabolome reveals the 4-hydroxymandelate CoQ10 synthesis pathway
Oxygen is critical for a multitude of metabolic processes that are essential for human life. Biological processes can be identified by treating cells with 18O2 or other isotopically labelled gases and systematically identifying biomolecules incorporating labeled atoms. Here we labelled cell lines of distinct tissue origins with 18O2 to identify the polar oxy-metabolome, defined as polar metabolitesÂ labelled with 18O under different physiological O2 tensions. The most highly 18O-labelled feature was 4-hydroxymandelate (4-HMA).Â We demonstrate that 4-HMA is produced by hydroxyphenylpyruvate dioxygenase-like (HPDL), a protein of previously unknown function in human cells. We identify 4-HMA as an intermediate involved in the biosynthesis of the coenzyme Q10 (CoQ10) headgroup in human cells. The connection of HPDL to CoQ10 biosynthesis provides crucial insights into the mechanisms underlying recently described neurological diseases related to HPDL deficiencies1-4 and cancers with HPDL overexpression5.
Spontaneous hydrolysis and spurious metabolic properties of Î±-ketoglutarate esters
Î±-ketoglutarate (KG), also referred to as 2-oxoglutarate, is a key intermediate of cellular metabolism with pleiotropic functions. Cell-permeable esterified analogs are widely used to study how KG fuels bioenergetic and amino acid metabolism and DNA, RNA, and protein hydroxylation reactions, as cellular membranes are thought to be impermeable to KG. Here we show that esterified KG analogs rapidly hydrolyze in aqueous media, yielding KG that, in contrast to prevailing assumptions, imports into many cell lines. Esterified KG analogs exhibit spurious KG-independent effects on cellular metabolism, including extracellular acidification, arising from rapid hydrolysis and de-protonation of Î±-ketoesters, and significant analog-specific inhibitory effects on glycolysis or mitochondrial respiration. We observe that imported KG decarboxylates to succinate in the cytosol and contributes minimally to mitochondrial metabolism in many cell lines cultured in normal conditions. These findings demonstrate that nuclear and cytosolic KG-dependent reactions may derive KG from functionally distinct subcellular pools and sources.
Harnessing metabolic dependencies in pancreatic cancers
Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive disease with a 5-year survival rate of <10%. The tumour microenvironment (TME) of PDAC is characterized by excessive fibrosis and deposition of extracellular matrix, termed desmoplasia. This unique TME leads to high interstitial pressure, vascular collapse and low nutrient and oxygen diffusion. Together, these factors contribute to the unique biology and therapeutic resistance of this deadly tumour. To thrive in this hostile environment, PDAC cells adapt by using non-canonical metabolic pathways and rely on metabolic scavenging pathways such as autophagy and macropinocytosis. Here, we review the metabolic pathways that PDAC use to support their growth in the setting of an austere TME. Understanding how PDAC tumours rewire their metabolism and use scavenging pathways under environmental stressors might enable the identification of novel therapeutic approaches.
Autophagy is critical for cysteine metabolism in pancreatic cancer through regulation of SLC7A11
Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest forms of cancer. The elevated macroautophagy/autophagy in these tumors supports growth, promotes immune evasion, and increases therapeutic resistance. Therefore, targeting autophagy is a therapeutic strategy that is being pursued to treat PDAC patients. Whereas autophagy inhibition impairs mitochondrial metabolism in PDAC, the specific metabolite(s) that becomes limiting when autophagy is inhibited has not been identified. We report that loss of autophagy specifically results in intracellular cysteine depletion under nutrient-replete conditions. Mechanistically, we show that PDAC cells utilize the autophagy machinery to regulate the activity and localization of the cystine transporter SLC7A11 at the plasma membrane. Upon inhibition of autophagy, SLC7A11 is localized to lysosomes in an MTORC2-dependent manner. Our findings reveal a novel connection between autophagy and cysteine metabolism in pancreatic cancer.
Metabolic Codependencies in the Tumor Microenvironment
Metabolic reprogramming enables cancer cell growth, proliferation, and survival. This reprogramming is driven by the combined actions of oncogenic alterations in cancer cells and host cell factors acting on cancer cells in the tumor microenvironment. Cancer cell intrinsic mechanisms activate signal transduction components that either directly enhance metabolic enzyme activity or upregulate transcription factors that in turn increase expression of metabolic regulators. Extrinsic signaling mechanisms involve host-derived factors that further promote and amplify metabolic reprogramming in cancer cells. This review describes intrinsic and extrinsic mechanisms driving cancer metabolism in the tumor microenvironment and how such mechanisms may be targeted therapeutically.
Autophagy is required for proper cysteine homeostasis in pancreatic cancer through regulation of SLC7A11
Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest forms of cancer and is highly refractory to current therapies. We had previously shown that PDAC can utilize its high levels of basal autophagy to support its metabolism and maintain tumor growth. Consistent with the importance of autophagy in PDAC, autophagy inhibition significantly enhances response of PDAC patients to chemotherapy in two randomized clinical trials. However, the specific metabolite(s) that autophagy provides to support PDAC growth is not yet known. In this study, we demonstrate that under nutrient-replete conditions, loss of autophagy in PDAC leads to a relatively restricted impairment of amino acid pools, with cysteine levels showing a significant drop. Additionally, we made the striking discovery that autophagy is critical for the proper membrane localization of the cystine transporter SLC7A11. Mechanistically, autophagy impairment results in the loss of SLC7A11 on the plasma membrane and increases its localization at the lysosome in an mTORC2-dependent manner. Our results demonstrate a critical link between autophagy and cysteine metabolism and provide mechanistic insights into how targeting autophagy can cause metabolic dysregulation in PDAC.
Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition)
In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct autophagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for bona fide autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field.