Acetyl-CoA carboxylase obstructs CD8+ T cell lipid utilization in the tumor microenvironment.

The solid tumor microenvironment (TME) imprints a compromised metabolic state in tumor-infiltrating T cells (TILs), hallmarked by the inability to maintain effective energy synthesis for antitumor function and survival. T cells in the TME must catabolize lipids via mitochondrial fatty acid oxidation (FAO) to supply energy in nutrient stress, and it is established that T cells enriched in FAO are adept at cancer control. However, endogenous TILs and unmodified cellular therapy products fail to sustain bioenergetics in tumors. We reveal that the solid TME imposes perpetual acetyl-coenzyme A (CoA) carboxylase (ACC) activity, invoking lipid biogenesis and storage in TILs that opposes FAO. Using metabolic, lipidomic, and confocal imaging strategies, we find that restricting ACC rewires T cell metabolism, enabling energy maintenance in TME stress. Limiting ACC activity potentiates a gene and phenotypic program indicative of T cell longevity, engendering T cells with increased survival and polyfunctionality, which sustains cancer control.

Stress-Mediated Attenuation of Translation Undermines T-cell Activity in Cancer.

Protein synthesis supports robust immune responses. Nutrient competition and global cell stressors in the tumor microenvironment (TME) may impact protein translation in T cells and antitumor immunity. Using human and mouse tumors, we demonstrated here that protein translation in T cells is repressed in solid tumors. Reduced glucose availability to T cells in the TME led to activation of the unfolded protein response (UPR) element eIF2α (eukaryotic translation initiation factor 2 alpha). Genetic mouse models revealed that translation attenuation mediated by activated p-eIF2α undermines the ability of T cells to suppress tumor growth. Reprograming T-cell metabolism was able to alleviate p-eIF2α accumulation and translational attenuation in the TME, allowing for sustained protein translation. Metabolic and pharmacological approaches showed that proteasome activity mitigates induction of p-eIF2α to support optimal antitumor T-cell function, protecting from translation attenuation and enabling prolonged cytokine synthesis in solid tumors. Together, these data identify a new therapeutic avenue to fuel the efficacy of tumor immunotherapy. SIGNIFICANCE: Proteasome function is a necessary cellular component for endowing T cells with tumor killing capacity by mitigating translation attenuation resulting from the unfolded protein response induced by stress in the tumor microenvironment.

High-Fat Diet Drives an Aggressive Pancreatic Cancer Phenotype.

BACKGROUND: Emerging evidence indicates associations between high-fat diet (HFD), metabolic syndrome (MetS), and increased risk of pancreatic cancer. However, individual components of an HFD that increase cancer risk have not been isolated. In addition, a specific pattern of cytokine elevation by which MetS drives pancreatic tumor progression is not well described. We hypothesized that oleic acid (OA), a major component of HFD, would augment pancreatic neoplastic processes. METHODS: An orthotopic pancreatic cancer model with Panc02 cells was used to compare the effect of low-fat diet to OA-based HFD on cancer progression. Tumors were quantitated, analyzed by immunohistochemistry. In addition, serum cytokine levels were quantitated. Proliferation, migration assays, and expression of epithelial-to-mesenchymal transition factors were evaluated on Panc02 and MiaPaCa-2 pancreatic cancer cells cultured in high concentrations of OA. RESULTS: HFD tumor-bearing mice (n = 8) had an 18% weight increase (P < 0.001) and increased tumor burden (P < 0.05) compared with the low-fat diet tumor-bearing group (n = 6). HFD tumors had significantly increased angiogenesis (P < 0.001) and decreased apoptosis (P < 0.05). Serum of HFD mice demonstrated increased levels of glucagon and glucagon-like peptide-1. Two pancreatic cancer cell lines cultured in OA demonstrated significant increases in proliferation (P < 0.001) and a >2.5-fold increase in cell migration (P < 0.001) when treated with OA. Panc02 treated with OA had increased expression of epithelial-to-mesenchymal transition factors SNAI-1 (Snail) and Zeb-1(P < 0.01). CONCLUSIONS: High-fat conditions in vitro and in vivo resulted in an aggressive pancreatic cancer phenotype. Our data support further investigations elucidating molecular pathways augmented by MetS conditions to identify novel therapeutic strategies for pancreatic cancer.

Targeting immunosuppressive macrophages overcomes PARP inhibitor resistance in BRCA1-associated triple-negative breast cancer.

Despite objective responses to PARP inhibition and improvements in progression-free survival compared to standard chemotherapy in patients with BRCA-associated triple-negative breast cancer (TNBC), benefits are transitory. Using high dimensional single-cell profiling of human TNBC, here we demonstrate that macrophages are the predominant infiltrating immune cell type in BRCA-associated TNBC. Through multi-omics profiling we show that PARP inhibitors enhance both anti- and pro-tumor features of macrophages through glucose and lipid metabolic reprogramming driven by the sterol regulatory element-binding protein 1 (SREBP-1) pathway. Combined PARP inhibitor therapy with CSF-1R blocking antibodies significantly enhanced innate and adaptive anti-tumor immunity and extends survival in BRCA-deficient tumors in vivo and is mediated by CD8+ T-cells. Collectively, our results uncover macrophage-mediated immune suppression as a liability of PARP inhibitor treatment and demonstrate combined PARP inhibition and macrophage targeting therapy induces a durable reprogramming of the tumor microenvironment, thus constituting a promising therapeutic strategy for TNBC.

Remodeling Translation Primes CD8+ T-cell Antitumor Immunity.

The requisites for protein translation in T cells are poorly understood and how translation shapes the antitumor efficacy of T cells is unknown. Here we demonstrated that IL15-conditioned T cells were primed by the metabolic energy sensor AMP-activated protein kinase to undergo diminished translation relative to effector T cells. However, we showed that IL15-conditioned T cells exhibited a remarkable capacity to enhance their protein translation in tumors, which effector T cells were unable to duplicate. Studying the modulation of translation for applications in cancer immunotherapy revealed that direct ex vivo pharmacologic inhibition of translation elongation primed robust T-cell antitumor immunity. Our work elucidates that altering protein translation in CD8+ T cells can shape their antitumor capability.

Endoplasmic Reticulum Protein Disulfide Isomerase Shapes T Cell Efficacy for Adoptive Cellular Therapy of Tumors.

Effective cancer therapies simultaneously restrict tumor cell growth and improve anti-tumor immune responses. Targeting redox-dependent protein folding enzymes within the endoplasmic reticulum (ER) is an alternative approach to activation of the unfolded protein response (UPR) and a novel therapeutic platform to induce malignant cell death. E64FC26 is a recently identified protein disulfide isomerase (PDI) inhibitor that activates the UPR, oxidative stress, and apoptosis in tumor cells, but not normal cell types. Given that targeting cellular redox homeostasis is a strategy to augment T cell tumor control, we tested the effect of E64FC26 on healthy and oncogenic T cells. In stark contrast to the pro-UPR and pro-death effects we observed in malignant T cells, we found that E64FC26 improved viability and limited the UPR in healthy T cells. E64FC26 treatment also diminished oxidative stress and decreased global PDI expression in normal T cells. Oxidative stress and cell death are limited in memory T cells and we found that PDI inhibition promoted memory traits and reshaped T cell metabolism. Using adoptive transfer of tumor antigen-specific CD8 T cells, we demonstrate that T cells activated and expanded in the presence of E64FC26 control tumor growth better than vehicle-matched controls. Our data indicate that PDI inhibitors are a new class of drug that may dually inhibit tumor cell growth and improve T cell tumor control.

Endoplasmic Reticulum Stress Contributes to Mitochondrial Exhaustion of CD8+ T Cells.

Tumor antigen-specific T cells rapidly lose energy and effector function in tumors. The cellular mechanisms by which energy loss and inhibition of effector function occur in tumor-infiltrating lymphocytes (TILs) are ill-defined, and methods to identify tumor antigen-specific TILs that experience such stress are unknown. Processes upstream of the mitochondria guide cell-intrinsic energy depletion. We hypothesized that a mechanism of T-cell-intrinsic energy consumption was the process of oxidative protein folding and disulfide bond formation that takes place in the endoplasmic reticulum (ER) guided by protein kinase R-like endoplasmic reticulum kinase (PERK) and downstream PERK axis target ER oxidoreductase 1 (ERO1α). To test this hypothesis, we created TCR transgenic mice with a T-cell-specific PERK gene deletion (OT1 + Lckcre+ PERK f/f , PERK KO). We found that PERK KO and T cells that were pharmacologically inhibited by PERK or ERO1α maintained reserve energy and exhibited a protein profile consistent with reduced oxidative stress. These T-cell groups displayed superior tumor control compared with T effectors. We identified a biomarker of ER-induced mitochondrial exhaustion in T cells as mitochondrial reactive oxygen species (mtROS), and found that PD-1+ tumor antigen-specific CD8+ TILs express mtROS. In vivo treatment with a PERK inhibitor abrogated mtROS in PD-1+ CD8+ TILs and bolstered CD8+ TIL viability. Combination therapy enabled 100% survival and 71% tumor clearance in a sarcoma mouse model. Our data identify the ER as a regulator of T-cell energetics and indicate that ER elements are effective targets to improve cancer immunotherapy.

miR-145 Antagonizes SNAI1-Mediated Stemness and Radiation Resistance in Colorectal Cancer.

Epithelial-to-mesenchymal transition (EMT) has been closely linked with therapy resistance and cancer stem cells (CSCs). However, EMT pathways have proven challenging to therapeutically target. MicroRNA 145 (miR-145) targets multiple stem cell transcription factors and its expression is inversely correlated with EMT. Therefore, we hypothesized that miR-145 represents a therapeutic target to reverse snail family transcriptional repressor 1 (SNAI1)-mediated stemness and radiation resistance (RT). Stable expression of SNAI1 in DLD1 and HCT116 cells (DLD1-SNAI1; HCT116-SNAI1) increased expression of Nanog and decreased miR-145 expression compared to control cells. Using a miR-145 luciferase reporter assay, we determined that ectopic SNAI1 expression significantly repressed the miR-145 promoter. DLD1-SNAI1 and HCT116-SNAI1 cells demonstrated decreased RT sensitivity and, conversely, miR-145 replacement significantly enhanced RT sensitivity. Of the five parental colon cancer cell lines, SW620 cells demonstrated relatively high endogenous SNAI1 and low miR-145 levels. In the SW620 cells, miR-145 replacement decreased CSC-related transcription factor expression, spheroid formation, and radiation resistance. In rectal cancer patient-derived xenografts, CSC identified by EpCAM+/aldehyde dehydrogenase (ALDH)+ demonstrated high expression of SNAI1, c-Myc, and Nanog compared with non-CSCs (EpCAM+/ALDH-). Conversely, patient-derived CSCs demonstrated low miR-145 expression levels relative to non-CSCs. These results suggest that the SNAI1:miR-145 pathway represents a novel therapeutic target in colorectal cancer to overcome RT resistance.

SNAI2 modulates colorectal cancer 5-fluorouracil sensitivity through miR145 repression.

Epithelial-to-mesenchymal transition (EMT) has been associated with poor treatment outcomes in various malignancies and is inversely associated with miRNA145 expression. Therefore, we hypothesized that SNAI2 (Slug) may mediate 5-fluorouracil (5FU) chemotherapy resistance through inhibition of miR145 in colorectal cancer and thus represents a novel therapeutic target to enhance current colorectal cancer treatment strategies. Compared with parental DLD1 colon cancer cells, 5FU-resistant (5FUr) DLD1 cells demonstrated features of EMT, including >2-fold enhanced invasion (P < 0.001) and migration, suppressed E-cadherin expression, and 2-fold increased SNAI2 expression. DLD1 and HCT116 cells with stable expression of SNAI2 (DLD1/SNAI2; HCT116/SNAI2) also demonstrated EMT features such as the decreased E-cadherin as well as significantly decreased miR145 expression, as compared with control empty vector cells. On the basis of an miR145 luciferase promoter assay, we demonstrated that SNAI2 repressed activity of the miR145 promoter in the DLD1 and HCT116 cells. In addition, the ectopic expressing SNAI2 cell lines demonstrated decreased 5FU sensitivity, and, conversely, miR145 replacement significantly enhanced 5FU sensitivity. In the parental SW620 colon cancer cell line with high SNAI2 and low miR145 levels, inhibition of SNAI2 directly with short hairpin sequence for SNAI2 and miR145 replacement therapy both decreased vimentin expression and increased in vitro 5FU sensitivity. In pretreatment rectal cancer patient biopsy samples, low miR145 expression levels correlated with poor response to neoadjuvant 5FU-based chemoradiation. These results suggested that the SNAI2:miR145 pathway may represent a novel clinical therapeutic target in colorectal cancer and may serve as a response predictor to chemoradiation therapy.