Pancreatic ductal adenocarcinoma is a notoriously difficult-to-treat cancer and patients are in need of novel therapies. We have shown previously that these tumours have altered metabolic ...requirements, making them highly reliant on a number of adaptations including a non-canonical glutamine (Gln) metabolic pathway and that inhibition of downstream components of Gln metabolism leads to a decrease in tumour growth. Here we test whether recently developed inhibitors of glutaminase (GLS), which mediates an early step in Gln metabolism, represent a viable therapeutic strategy. We show that despite marked early effects on in vitro proliferation caused by GLS inhibition, pancreatic cancer cells have adaptive metabolic networks that sustain proliferation in vitro and in vivo. We use an integrated metabolomic and proteomic platform to understand this adaptive response and thereby design rational combinatorial approaches. We demonstrate that pancreatic cancer metabolism is adaptive and that targeting Gln metabolism in combination with these adaptive responses may yield clinical benefits for patients.
Major histocompatibility complex class I (MHC-I) is a key molecule in anti-tumor adaptive immunity. MHC-I is essential for endogenous antigen presentation by cancer cells and subsequent recognition ...and clearance by CD8
+
T cells. Defects in MHC-I expression occur frequently in several cancers, leading to impaired antigen presentation, immune evasion and/or resistance to immune checkpoint blockade (ICB) therapy. Pancreatic ductal adenocarcinoma (PDAC), a deadly malignancy with dismal patient prognosis, is resistant to ICB and shows frequent downregulation of MHC-I independent of genetic mutations abrogating MHC-I expression. Previously, we showed that PDAC cells exhibit elevated levels of autophagy and lysosomal biogenesis, which together support the survival and growth of PDAC tumors via both cell-autonomous and non-cell-autonomous mechanisms. In our recent study, we have identified NBR1-mediated selective macroautophagy/autophagy of MHC-I as a novel mechanism that facilitates immune evasion by PDAC cells. Importantly, autophagy or lysosome inhibition restores MHC-I expression, leading to enhanced anti-tumor T cell immunity and improved response to ICB in transplanted tumor models in syngeneic host mice. Our results highlight a previously unknown function of autophagy and the lysosome in regulation of immunogenicity in PDAC, and provide a novel therapeutic strategy for targeting this deadly disease.
Basal levels of autophagy are elevated in most pancreatic ductal adenocarcinomas (PDAC). Suppressing autophagy pharmacologically using chloroquine (CQ) or genetically with RNAi to essential autophagy ...genes inhibits human pancreatic cancer growth in vitro and in vivo, which presents possible treatment opportunities for PDAC patients using the CQ-derivative hydroxychloroquine (HCQ). Indeed, such clinical trials are ongoing. However, autophagy is a complex cellular mechanism to maintain cell homeostasis under stress. Based on its biological role, a dual role of autophagy in tumorigenesis has been proposed: at tumor initiation, autophagy helps maintain genomic stability and prevent tumor initiation; while in advanced disease, autophagy degrades and recycles cellular components to meet the metabolic needs for rapid growth. This model was proven to be the case in mouse lung tumor models. However, in contrast to prior work in various PDAC model systems, loss of autophagy in PDAC mouse models with embryonic homozygous Trp53 deletion does not inhibit tumor growth and paradoxically increases progression. This raised concerns whether there may be a genotype-dependent reliance of PDAC on autophagy. In a recent study, our group used a Trp53 heterozygous mouse PDAC model and human PDX xenografts to address the question. Our results demonstrate that autophagy inhibition was effective against PDAC tumors irrespective of TP53/TRP53 status.
Drug resistance remains a major clinical challenge for cancer treatment. Multiple myeloma is an incurable plasma cell cancer selectively localized in the bone marrow. The main cause of resistance in ...myeloma is the minimal residual disease cells that are resistant to the original therapy, including bortezomib treatment and high-dose melphalan in stem cell transplant. In this study, we demonstrate that altered tumor cell metabolism is essential for the regulation of drug resistance in multiple myeloma cells. We show the unprecedented role of the metabolic phenotype in inducing drug resistance through LDHA and HIF1A in multiple myeloma, and that specific inhibition of LDHA and HIF1A can restore sensitivity to therapeutic agents such as bortezomib and can also inhibit tumor growth induced by altered metabolism. Knockdown of LDHA can restore sensitivity of bortezomib resistance cell lines while gain-of-function studies using LDHA or HIF1A induced resistance in bortezomib-sensitive cell lines. Taken together, these data suggest that HIF1A and LDHA are important targets for hypoxia-driven drug resistance. Novel drugs that regulate metabolic pathways in multiple myeloma, specifically targeting LDHA, can be beneficial to inhibit tumor growth and overcome drug resistance.
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.
NCOA4 is a selective cargo receptor for the autophagic turnover of ferritin, a process critical for regulation of intracellular iron bioavailability. However, how ferritinophagy flux is controlled ...and the roles of NCOA4 in iron-dependent processes are poorly understood. Through analysis of the NCOA4-FTH1 interaction, we demonstrate that direct association via a key surface arginine in FTH1 and a C-terminal element in NCOA4 is required for delivery of ferritin to the lysosome via autophagosomes. Moreover, NCOA4 abundance is under dual control via autophagy and the ubiquitin proteasome system. Ubiquitin-dependent NCOA4 turnover is promoted by excess iron and involves an iron-dependent interaction between NCOA4 and the HERC2 ubiquitin ligase. In zebrafish and cultured cells, NCOA4 plays an essential role in erythroid differentiation. This work reveals the molecular nature of the NCOA4-ferritin complex and explains how intracellular iron levels modulate NCOA4-mediated ferritinophagy in cells and in an iron-dependent physiological setting.
Macroautophagy (autophagy) is a regulated catabolic pathway to degrade cellular organelles and macromolecules. The role of autophagy in cancer is complex and may differ depending on tumor type or ...context. Here we show that pancreatic cancers have a distinct dependence on autophagy. Pancreatic cancer primary tumors and cell lines show elevated autophagy under basal conditions. Genetic or pharmacologic inhibition of autophagy leads to increased reactive oxygen species, elevated DNA damage, and a metabolic defect leading to decreased mitochondrial oxidative phosphorylation. Together, these ultimately result in significant growth suppression of pancreatic cancer cells in vitro. Most importantly, inhibition of autophagy by genetic means or chloroquine treatment leads to robust tumor regression and prolonged survival in pancreatic cancer xenografts and genetic mouse models. These results suggest that, unlike in other cancers where autophagy inhibition may synergize with chemotherapy or targeted agents by preventing the up-regulation of autophagy as a reactive survival mechanism, autophagy is actually required for tumorigenic growth of pancreatic cancers de novo, and drugs that inactivate this process may have a unique clinical utility in treating pancreatic cancers and other malignancies with a similar dependence on autophagy. As chloroquine and its derivatives are potent inhibitors of autophagy and have been used safely in human patients for decades for a variety of purposes, these results are immediately translatable to the treatment of pancreatic cancer patients, and provide a much needed, novel vantage point of attack.
Pancreatic ductal adenocarcinomas (PDA) are extremely aggressive cancers and currently available therapies are only minimally effective in treating this disease. Tackling this devastating cancer has ...been a major challenge to the scientific and medical communities, in part due to its intense therapeutic resistance. One of the aspects of this tumor that contributes to its aggressive behavior is its altered cellular metabolism. Indeed, PDA cells seem to possess the ability to adapt their metabolism to the particular environment to which they are exposed, including utilizing diverse fuel sources depending on their availability. Moreover, PDA tumors are efficient at recycling various metabolic substrates through activation of different salvage pathways such as autophagy and macropinocytosis. Together, these diverse metabolic adaptations allow PDA cells to survive and thrive in harsh environments that may lack nutrients and oxygen. Not surprisingly, given its central role in the pathogenesis of this tumor, oncogenic Kras plays a critical role in much of the metabolic reprogramming seen in PDA. In this review, we discuss the metabolic landscape of PDA tumors, including the molecular underpinnings of the key regulatory nodes, and describe how such pathways can be exploited for future diagnostic and therapeutic approaches.
Targeting glycolysis has been considered therapeutically intractable owing to its essential housekeeping role. However, the context-dependent requirement for individual glycolytic steps has not been ...fully explored. We show that CRISPR-mediated targeting of glycolysis in T cells in mice results in global loss of Th17 cells, whereas deficiency of the glycolytic enzyme glucose phosphate isomerase (Gpi1) selectively eliminates inflammatory encephalitogenic and colitogenic Th17 cells, without substantially affecting homeostatic microbiota-specific Th17 cells. In homeostatic Th17 cells, partial blockade of glycolysis upon Gpi1 inactivation was compensated by pentose phosphate pathway flux and increased mitochondrial respiration. In contrast, inflammatory Th17 cells experience a hypoxic microenvironment known to limit mitochondrial respiration, which is incompatible with loss of Gpi1. Our study suggests that inhibiting glycolysis by targeting Gpi1 could be an effective therapeutic strategy with minimum toxicity for Th17-mediated autoimmune diseases, and, more generally, that metabolic redundancies can be exploited for selective targeting of disease processes.
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•PPP and OXPHOS compensate for Gpi1 loss in Th17 cells in normoxic environment•Gpi1 is essential in hypoxic inflamed tissue due to reduced OXPHOS compensation•Metabolic redundancy can vary according to the microenvironment•Targeting Gpi1 could be a tolerable approach for therapeutic glycolysis inhibition
Metabolic redundancy differs according to microenvironments, making the glycolysis gene Gpi1 dispensable for homeostatic Th17 cells in normal tissue but essential for pathogenic Th17 cells in hypoxic inflamed tissue.
Over the past two decades, the molecular machinery that underlies autophagic responses has been characterized with ever increasing precision in multiple model organisms. Moreover, it has become clear ...that autophagy and autophagy‐related processes have profound implications for human pathophysiology. However, considerable confusion persists about the use of appropriate terms to indicate specific types of autophagy and some components of the autophagy machinery, which may have detrimental effects on the expansion of the field. Driven by the overt recognition of such a potential obstacle, a panel of leading experts in the field attempts here to define several autophagy‐related terms based on specific biochemical features. The ultimate objective of this collaborative exchange is to formulate recommendations that facilitate the dissemination of knowledge within and outside the field of autophagy research.
Autophagy‐related responses are described in an increasing number of distinct biological contexts. This review discusses the use of appropriate terms for autophagic processes with the aim to provide recommendations and avoid confusion in the field of autophagy research.
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