CD73-dependent adenosine signaling through Adora2b drives immunosuppression in ductal pancreatic cancer
The microenvironment that surrounds pancreatic ductal adenocarcinoma (PDAC) is profoundly desmoplastic and immunosuppressive. Understanding triggers of immunosuppression during the process of pancreatic tumorigenesis would aid in establishing targets for effective prevention and therapy. Here, we interrogated differential molecular mechanisms dependent on cell of origin and subtype that promote immunosuppression during PDAC initiation and in established tumors. Transcriptomic analysis of cell of origin-dependent epithelial gene signatures revealed that Nt5e/CD73, a cell surface enzyme required for extracellular adenosine generation, is one of the top 10% of genes over-expressed in murine tumors arising from ductal pancreatic epithelium as opposed to those rising from acinar cells. These findings were confirmed by immunohistochemistry and high-performance liquid chromatography. Analysis in human PDAC subtypes indicated that high Nt5e in murine ductal PDAC models overlaps with high NT5E in human PDAC squamous and basal subtypes, considered to have the highest immunosuppression and worst prognosis. Multiplex immunofluorescent analysis showed that activated CD8+ T cells in the PDAC tumor microenvironment express high levels of CD73 indicating an opportunity for immunotherapeutic targeting. Delivery of CD73 small molecule inhibitors through various delivery routes reduced tumor development and growth in genetically engineered and syngeneic mouse models. In addition, the adenosine receptor Adora2b was a determinant of adenosine-mediated immunosuppression in PDAC. These findings highlight a molecular trigger of the immunosuppressive PDAC microenvironment elevated in ductal cell of origin, linking biology with subtype classification, critical components for PDAC immunoprevention and personalized approaches for immunotherapeutic intervention.
Cytoskeletal association of ATP citrate lyase controls the mechanodynamics of macropinocytosis
Macropinocytosis is an actin-dependent mode of nonselective endocytosis that mediates the uptake of extracellular fluid-phase cargoes. It is now well recognized that tumor cells exploit macropinocytosis to internalize macromolecules that can be catabolized and used to support cell growth and proliferation under nutrient-limiting conditions. Therefore, the identification of molecular mechanisms that control macropinocytosis is fundamental to the understanding of the metabolic adaptive landscape of tumor cells. Here, we report that the acetyl-CoA-producing enzyme, ATP citrate lyase (ACLY), is a key regulator of macropinocytosis and describes a heretofore-unappreciated association of ACLY with the actin cytoskeleton. The cytoskeletal tethering of ACLY is required for the spatially defined acetylation of heterodimeric actin capping protein, which we identify as an essential mediator of the actin remodeling events that drive membrane ruffling and macropinocytosis. Furthermore, we identify a requirement for mitochondrial-derived citrate, an ACLY substrate, for macropinocytosis, and show that mitochondria traffic to cell periphery regions juxtaposed to plasma membrane ruffles. Collectively, these findings establish a mode of metabolite compartmentalization that supports the spatiotemporal modulation of membrane-cytoskeletal interactions required for macropinocytosis by coupling regional acetyl-CoA availability with dynamic protein acetylation.
Î±2,6-Sialylation Is Upregulated in Severe COVID-19, Implicating the Complement Cascade
Better understanding of the molecular mechanisms underlying COVID-19 severity is desperately needed in current times. Although hyper-inflammation drives severe COVID-19, precise mechanisms triggering this cascade and what role glycosylation might play therein are unknown. Here we report the first high-throughput glycomic analysis of COVID-19 plasma samples and autopsy tissues. We find that Î±2,6-sialylation is upregulated in the plasma of patients with severe COVID-19 and in autopsied lung tissue. This glycan motif is enriched on members of the complement cascade (e.g., C5, C9), which show higher levels of sialylation in severe COVID-19. In the lung tissue, we observe increased complement deposition, associated with elevated Î±2,6-sialylation levels, corresponding to elevated markers of poor prognosis (IL-6) and fibrotic response. We also observe upregulation of the Î±2,6-sialylation enzyme ST6GAL1 in patients who succumbed to COVID-19. Our work identifies a heretofore undescribed relationship between sialylation and complement in severe COVID-19, potentially informing future therapeutic development.
MACHETE identifies interferon-encompassing chromosome 9p21.3 deletions as mediators of immune evasion and metastasis
The most prominent homozygous deletions in cancer affect chromosome 9p21.3 and eliminate CDKN2A/B tumor suppressors, disabling a cell-intrinsic barrier to tumorigenesis. Half of 9p21.3 deletions, however, also encompass a type I interferon (IFN) gene cluster; the consequences of this co-deletion remain unexplored. To functionally dissect 9p21.3 and other large genomic deletions, we developed a flexible deletion engineering strategy, MACHETE (molecular alteration of chromosomes with engineered tandem elements). Applying MACHETE to a syngeneic mouse model of pancreatic cancer, we found that co-deletion of the IFN cluster promoted immune evasion, metastasis and immunotherapy resistance. Mechanistically, IFN co-deletion disrupted type I IFN signaling in the tumor microenvironment, leading to marked changes in infiltrating immune cells and escape from CD8+â€‰T-cell surveillance, effects largely driven by the poorly understood interferon epsilon. These results reveal a chromosomal deletion that disables both cell-intrinsic and cell-extrinsic tumor suppression and provide a framework for interrogating large deletions in cancer and beyond.
Exercise-induced engagement of the IL-15/IL-15RÎ± axis promotes anti-tumor immunity in pancreatic cancer
Aerobic exercise is associated with decreased cancer incidence and cancer-associated mortality. However, little is known about the effects of exercise on pancreatic ductal adenocarcinoma (PDA), a disease for which current therapeutic options are limited. Herein, we show that aerobic exercise reduces PDA tumor growth, by modulating systemic and intra-tumoral immunity. Mechanistically, exercise promotes immune mobilization and accumulation of tumor-infiltrating IL15RÎ±+ CD8 TÂ cells, which are responsible for the tumor-protective effects. In clinical samples, an exercise-dependent increase of intra-tumoral CD8 T cells is also observed. Underscoring the translational potential of the interleukin (IL)-15/IL-15RÎ± axis, IL-15 super-agonist (NIZ985) treatment attenuates tumor growth, prolongs survival, and enhances sensitivity to chemotherapy. Finally, exercise or NIZ985 both sensitize pancreatic tumors to Î±PD-1, with improved anti-tumor and survival benefits. Collectively, our findings highlight the therapeutic potential of an exercise-oncology axis and identify IL-15 activation as a promising treatment strategy for this deadly disease.
Adaptive stimulation of macropinocytosis overcomes aspartate limitation in cancer cells under hypoxia
Stress-adaptive mechanisms enable tumour cells to overcome metabolic constraints under nutrient and oxygen shortage. Aspartate is an endogenous metabolic limitation under hypoxic conditions, but the nature of the adaptive mechanisms that contribute to aspartate availability and hypoxic tumour growth are poorly understood. Here we identify GOT2-catalysed mitochondrial aspartate synthesis as an essential metabolic dependency for the proliferation of pancreatic tumour cells under hypoxic culture conditions. In contrast, GOT2-catalysed aspartate synthesis is dispensable for pancreatic tumour formation in vivo. The dependence of pancreatic tumour cells on aspartate synthesis is bypassed in part by a hypoxia-induced potentiation of extracellular protein scavenging via macropinocytosis. This effect is mutant KRAS dependent, and is mediated by hypoxia-inducible factor 1 (HIF1A) and its canonical target carbonic anhydrase-9 (CA9). Our findings reveal high plasticity of aspartate metabolism and define an adaptive regulatory role for macropinocytosis by which mutant KRASï»¿ tumours can overcome nutrient deprivation under hypoxic conditions.
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.
A phase 1b study evaluating IL-1beta and PD-1 targeting with chemotherapy in metastatic pancreatic cancer (PanCAN-SR1) [Meeting Abstract]
Background: Pancreatic ductal adenocarcinoma (PDA) is a highly lethal malignancy that is refractory to therapeutic targeting of the immune microenvironment. In preclinical work, IL-1beta was shown to be upregulated in pancreatic cancer tumors, and in mouse models, IL-1beta expression led to activation of pancreatic stellate cells and immunosuppression (Das et al 2020). We hypothesize that blockade of IL-1beta and PD-1 will result in alterations in myeloid, lymphoid, and fibroblast subsets within the pancreatic cancer microenvironment and add therapeutic benefit in combination with chemotherapy in PDA.
Method(s): We are conducting an open-label multicenter Phase Ib study evaluating a 4 drug regimen including gemcitabine and nabpaclitaxel with the addition of canakinumab (ACZ885), a high-affinity human anti-interleukin1beta (IL-1beta) monoclonal antibody (mAb), and spartalizumab (PDR001), a mAb directed against human Programmed Death-1 (PD-1). Eligible subjects have metastatic PDA without prior anticancer therapy for metastatic disease and RECIST measurable disease. The primary objective was to identify a recommended phase II/III dose of combination therapy by evaluating the incidence of dose limiting toxicities in the first 56 days (8 weeks) of dosing in at least 6 evaluable subjects utilizing a Bayesian logistic regression model. All subjects underwent baseline and on-study tissue and blood collection for extensive exploratory correlative studies. Secondary objectives including safety and tolerability of quadruple therapy and preliminary assessment of clinical activity.
Result(s): 10 subjects were enrolled between November 2020 and March 2021, and the first 6 subjects to complete 8 weeks of therapy were included in the dose confirmation analysis. There were no dose limiting toxicities and the recommended Phase II/III dose was established as; gemcitabine (1000 mg/m2 IV) on day 1,8,15; nab-paclitaxel (125 mg/m2 IV) on day 1,8,15, canakinumab (250 mg via subcutaneous injection) on day 1, spartalizumab (400 mg IV) on day 1; of each 28 day cycle. Adverse events were consistent with those seen with chemotherapy and were predominately hematologic. The majority of subjects completed the on-treatment blood and tissue collection for correlative analysis. The study is ongoing with subjects remaining on therapy and all subjects will be evaluated for efficacy.
Conclusion(s): In this Phase Ib study, we demonstrated the feasibility and safety of adding canakinumab and spartalizumab to standard of care chemotherapy in first line metastatic PDA and established the recommended Phase II/III dose. This novel 4 drug combination will be tested in a randomized Phase II/III study through the Precision Promise clinical trial network. Preliminary correlative and efficacy data will be reported
EMSY inhibits homologous recombination repair and the interferon response, promoting lung cancer immune evasion
Non-small cell lung cancers (NSCLCs) harboring KEAP1 mutations are often resistant to immunotherapy. Here, we show that KEAP1 targets EMSY for ubiquitin-mediated degradation to regulate homologous recombination repair (HRR) and anti-tumor immunity. Loss of KEAP1 in NSCLC induces stabilization of EMSY, producing a BRCAness phenotype, i.e., HRR defects and sensitivity to PARP inhibitors. Defective HRR contributes to a high tumor mutational burden that, in turn, is expected to prompt an innate immune response. Notably, EMSY accumulation suppresses the type I interferon response and impairs innate immune signaling, fostering cancer immune evasion. Activation of the type I interferon response in the tumor microenvironment using a STING agonist results in the engagement of innate and adaptive immune signaling and impairs the growth of KEAP1-mutant tumors. Our results suggest that targeting PARP and STING pathways, individually or in combination, represents a therapeutic strategy in NSCLC patients harboring alterations in KEAP1.
Exploiting cancer's drinking problem: regulation and therapeutic potential of macropinocytosis
Macropinocytosis, an evolutionarily conserved endocytic mechanism that mediates non-specific fluid-phase uptake, is potently upregulated by various oncogenic pathways. It is now well appreciated that high macropinocytic activity is a hallmark of many human tumors, which use this adaptation to scavenge extracellular nutrients for fueling cell growth. In the context of the nutrient-scarce tumor microenvironment, this process provides tumor cells with metabolic flexibility. However, dependence on this scavenging mechanism also illuminates a potential metabolic vulnerability. As such, there is a great deal of interest in understanding the molecular underpinnings of macropinocytosis. In this review, we will discuss the most recent advances in characterizing macropinocytosis: the pathways that regulate it, its contribution to the metabolic fitness of cancer cells, and its therapeutic potential.