Thioredoxin-1 improves the immunometabolic phenotype of antitumor T cells.

Adoptive transfer of tumor epitope-reactive T cells has emerged as a promising strategy to control tumor growth. However, chronically-stimulated T cells expanded for adoptive cell transfer are susceptible to cell death in an oxidative tumor microenvironment. Because oxidation of cell-surface thiols also alters protein functionality, we hypothesized that increasing the levels of thioredoxin (Trx), an antioxidant molecule facilitating reduction of proteins through cysteine thiol-disulfide exchange, in T cells will promote their sustained antitumor function. Using pre-melanosome protein (Pmel)-Trx1 transgenic mouse-derived splenic T cells, flow cytometry, and gene expression analysis, we observed here that higher Trx expression inversely correlated with reactive oxygen species and susceptibility to T-cell receptor restimulation or oxidation-mediated cell death. These Trx1-overexpressing T cells exhibited a cluster of differentiation 62Lhi (CD62Lhi) central memory-like phenotype with reduced glucose uptake (2-NBDGlo) and decreased effector function (interferon γlo). Furthermore, culturing tumor-reactive T cells in the presence of recombinant Trx increased the dependence of T cells on mitochondrial metabolism and improved tumor control. We conclude that strategies for increasing the antioxidant capacity of antitumor T cells modulate their immunometabolic phenotype leading to improved immunotherapeutic control of established tumors.

Metabolic remodeling contributes towards an immune-suppressive phenotype in glioblastoma.

Glioblastoma (GBM) is one of the most aggressive tumors. Numerous studies in the field of immunotherapy have focused their efforts on identifying various pathways linked with tumor-induced immunosuppression. Recent research has demonstrated that metabolic reprogramming in a tumor can contribute towards immune tolerance. To begin to understand the interface between metabolic remodeling and the immune-suppressive state in GBM, we performed a focused, integrative analysis coupling metabolomics with gene-expression profiling in patient-derived GBM (n = 80) and compared them to low-grade astrocytoma (LGA; n = 28). Metabolic intermediates of tryptophan, arginine, prostaglandin, and adenosine emerged as immuno-metabolic nodes in GBM specific to the mesenchymal and classical molecular subtypes of GBM. Integrative analyses emphasized the importance of downstream metabolism of several of these metabolic pathways in GBM. Using CIBERSORT to analyze immune components from the transcriptional profiles of individual tumors, we demonstrated that tryptophan and adenosine metabolism resulted in an accumulation of Tregs and M2 macrophages, respectively, and was recapitulated in mouse models. Furthermore, we extended these findings to preclinical models to determine their potential utility in defining the biologic and/or immunologic consequences of the identified metabolic programs. Collectively, through integrative analysis, we uncovered multifaceted ways by which metabolic reprogramming may contribute towards immune tolerance in GBM, providing the framework for further investigations designed to determine the specific immunologic consequence of these metabolic programs and their therapeutic potential.

Immunotherapy and radiation in glioblastoma.

Radiation therapy plays a central role in the management of glioblastoma. Although primarily thought of as modality to provide local tumor control through DNA damage, the capacity of ionizing radiation to modulate tumor immune response has long been recognized. The recent emergence of clinically active immunotherapies offers exciting potential for harnessing the immune modulatory effects or radiation through combinatorial strategies designed to enhance clinical outcomes. In this Review, we provide background describing the unique immune environment within the central nervous system, how ionizing radiation may modulate the tumor immune response, preclinical and clinical data testing the combination of radiation and immune modulating agents, and highlight some of the current challenges in extending these findings clinically.

Interleukin-12 enhances the function and anti-tumor activity in murine and human CD8(+) T cells.

Mouse CD8(+) T cells conditioned with interleukin (IL)-12 ex vivo mediate the potent regression of established melanoma when transferred into lymphodepleted mice. However, the quantitative and qualitative changes induced by IL-12 in the responding mouse CD8(+) T cells have not been well defined. Moreover, the mechanisms by which IL-12-conditioning impacts human CD8(+) T cells, and how such cells might be expanded prior to infusion into patients is not known. We found that ex vivo IL-12-conditioning of mouse CD8(+) T cells led to a tenfold-100-fold increase in persistence and anti-tumor efficacy upon adoptive transfer into lymphodepleted mice. The enhancing effect of IL-12 was associated with maintenance of functional avidity. Importantly, in the context of ongoing ACT clinical trials, human CD8(+) T cells genetically modified with a tyrosinase-specific T cell receptor (TCR) exhibited significantly enhanced functional activity when conditioned with IL-12 as indicated by heightened granzyme B expression and elevated peptide-specific CD107a degranulation. This effect was sustainable despite the 20 days of in vitro cellular expansion required to expand cells over 1,000-fold allowing adequate cell numbers for administration to cancer patients. Overall, these findings support the efficacy and feasibility of ex vivo IL-12-conditioning of TCR-modified human CD8(+) T cells for adoptive transfer and cancer therapy.

Quinolinate promotes macrophage-induced immune tolerance in glioblastoma through the NMDAR/PPARγ signaling axis.

There has been considerable scientific effort dedicated to understanding the biologic consequence and therapeutic implications of aberrant tryptophan metabolism in brain tumors and neurodegenerative diseases. A majority of this work has focused on the upstream metabolism of tryptophan; however, this has resulted in limited clinical application. Using global metabolomic profiling of patient-derived brain tumors, we identify the downstream metabolism of tryptophan and accumulation of quinolinate (QA) as a metabolic node in glioblastoma and demonstrate its critical role in promoting immune tolerance. QA acts as a metabolic checkpoint in glioblastoma by inducing NMDA receptor activation and Foxo1/PPARγ signaling in macrophages, resulting in a tumor supportive phenotype. Using a genetically-engineered mouse model designed to inhibit production of QA, we identify kynureninase as a promising therapeutic target to revert the potent immune suppressive microenvironment in glioblastoma. These findings offer an opportunity to revisit the biologic consequence of this pathway as it relates to oncogenesis and neurodegenerative disease and a framework for developing immune modulatory agents to further clinical gains in these otherwise incurable diseases.

The Influence of the Ketogenic Diet on the Immune Tolerant Microenvironment in Glioblastoma.

Glioblastoma (GBM) represents an aggressive and immune-resistant cancer. Preclinical investigations have identified anti-tumor activity of a ketogenic diet (KD) potentially being used to target GBM's glycolytic phenotype. Since immune cells in the microenvironment have a similar reliance upon nutrients to perform their individual functions, we sought to determine if KD influenced the immune landscape of GBM. Consistent with previous publications, KD improved survival in GBM in an immune-competent murine model. Immunophenotyping of tumors identified KD-influenced macrophage polarization, with a paradoxical 50% increase in immune-suppressive M2-like-macrophages and a decrease in pro-inflammatory M1-like-macrophages. We recapitulated KD in vitro using a modified cell culture based on metabolomic profiling of serum in KD-fed mice, mechanistically linking the observed changes in macrophage polarization to PPARγ-activation. We hypothesized that parallel increases in M2-macrophage polarization tempered the therapeutic benefit of KD in GBM. To test this, we performed investigations combining KD with the CSF-1R inhibitor (BLZ945), which influences macrophage polarization. The combination demonstrated a striking improvement in survival and correlative studies confirmed BLZ945 normalized KD-induced changes in macrophage polarization. Overall, KD demonstrates antitumor activity in GBM; however, its efficacy is attenuated by promoting an immunosuppressive phenotype in macrophages. Combinatorial strategies designed to modulate macrophage polarization represent a rational approach to improve the anti-tumor activity of KD in GBM.

Influence of caspases 8 and 9 gene promoter polymorphism on prostate cancer susceptibility and early development of hormone refractory prostate cancer.

OBJECTIVE: To investigate, by genotyping CASP8 (-652 6N del/ins) and CASP9 (-1263 A > G; -293 19N del/ins), whether inactivation of apoptosis by genetic polymorphism of caspases 8 and 9 play an integral role in the mechanism of cancer development. To investigate the role of these polymorphisms in susceptibility to early development of hormone refractory prostate cancer. PATIENTS AND METHODS: The study included 175 histologically confirmed cases of prostate cancer and 198 age and ethnicity matched healthy controls. CASP9-1263 A > G polymorphism was genotyped using the polymerase chain reaction-restriction fragment length polymorphism method. CASP9-293 del/ins and CASP8-652 del/ins polymorphisms were genotyped and the deletion pattern analysed by polyacrylamide gel electrophoresis. RESULTS: Our results demonstrated that presence of CASP9-1263 G allele was associated with reduced risk for prostate cancer (odds ratio 0.6, 95%CI 0.39-0.92, P= 0.02). Other variant CASP9 was not associated with prostate cancer risk. Coincidentally, the presence of CASP9-1263 G allele was associated with increased risk for progression of prostate cancer to bone metastasis (odds ratio -2.28, 95%CI 1.14-4.53, P= 0.02). CASP8-652 (+/-) genotype was associated with increased hazard for early development of hormone refractory prostate cancer (hazard ratio 2.44, 95%CI 1.2-5.85, P= 0.045). CONCLUSION: Our results support the hypothesis that variants of CASP9 may influence the susceptibility to prostate cancer and its progression to bone metastasis. CASP8 polymorphism may influence the progression of prostate cancer disease to a hormone refractory state.

Inhibition of Colony-Stimulating Factor-1 Receptor Enhances the Efficacy of Radiotherapy and Reduces Immune Suppression in Glioblastoma.

AIM: To use inhibition of colony-stimulating factor-1 receptor (CSF-1R) to target tumor-associated macrophages (TAMs) and improve the efficacy of radiotherapy in glioblastoma (GBM). MATERIALS AND METHODS: The CSF-1R inhibitor BLZ-945 was used to examine the impact of CSF-1R inhibition on M2 polarization in vitro. Using an orthotopic, immunocompetent GBM model, mice were treated with vehicle, RT, BLZ-945, or RT plus BLZ-945. RESULTS: BLZ-945 reduced M2 polarization in vitro. BLZ-945 alone did not improve median overall survival (mOS=29 days) compared to control mice (mOS=27 days). RT improved survival (mOS=45 days; p=0.02), while RT plus BLZ-945 led to the longest survival (mOS=not reached; p=0.005). Resected tumors had a relatively large population of M2 TAMs in GBM at baseline, which was increased in response to RT. BLZ-945 reduced RT-induced M2 infiltration. CONCLUSION: Inhibition of CSF-1R improved response to RT in the treatment of GBM and may represent a promising strategy to improve RT-induced antitumor immune responses.

Perhexiline Demonstrates FYN-mediated Antitumor Activity in Glioblastoma.

Glioblastoma is the most common primary malignant brain tumor in adults. Despite aggressive treatment, outcomes remain poor with few long-term survivors. Therefore, considerable effort is being made to identify novel therapies for this malignancy. Targeting tumor metabolism represents a promising therapeutic strategy and activation of fatty acid oxidation (FAO) has been identified as a central metabolic node contributing toward gliomagenesis. Perhexiline is a compound with a long clinical track record in angina treatment and commonly described as an FAO inhibitor. We therefore sought to determine whether this compound might be repurposed to serve as a novel therapy in glioblastoma. Perhexiline demonstrated potent in vitro cytotoxicity, induction of redox stress and apoptosis in a panel of glioblastoma cell lines. However, the antitumor activity of perhexiline was distinct when compared with the established FAO inhibitor etomoxir. By evaluating mitochondrial respiration and lipid dynamics in glioblastoma cells following treatment with perhexiline, we confirmed this compound did not inhibit FAO in our models. Using in silico approaches, we identified FYN as a probable target of perhexiline and validated the role of this protein in perhexiline sensitivity. We extended studies to patient samples, validating the potential of FYN to serve as therapeutic target in glioma. When evaluated in vivo, perhexiline demonstrated the capacity to cross the blood-brain barrier and antitumor activity in both flank and orthotopic glioblastoma models. Collectively, we identified potent FYN-dependent antitumor activity of perhexiline in glioblastoma, thereby, representing a promising agent to be repurposed for the treatment of this devastating malignancy.

Enhanced fatty acid oxidation provides glioblastoma cells metabolic plasticity to accommodate to its dynamic nutrient microenvironment.

Despite advances in molecularly characterizing glioblastoma (GBM), metabolic alterations driving its aggressive phenotype are only beginning to be recognized. Integrative cross-platform analysis coupling global metabolomic and gene expression profiling on patient-derived glioma identified fatty acid ß-oxidation (FAO) as a metabolic node in GBM. We determined that the biologic consequence of enhanced FAO is directly dependent upon tumor microenvironment. FAO serves as a metabolic cue to drive proliferation in a ß-HB/GPR109A dependent autocrine manner in nutrient favorable conditions, while providing an efficient, alternate source of ATP only in nutrient unfavorable conditions. Rational combinatorial strategies designed to target these dynamic roles FAO plays in gliomagenesis resulted in necroptosis-mediated metabolic synthetic lethality in GBM. In summary, we identified FAO as a dominant metabolic node in GBM that provides metabolic plasticity, allowing these cells to adapt to their dynamic microenvironment. Combinatorial strategies designed to target these diverse roles FAO plays in gliomagenesis offers therapeutic potential in GBM.

Polymorphisms in tumor necrosis factor-A gene and prostate cancer risk in North Indian cohort.

PURPOSE: The proinflammatory cytokine tumor necrosis factor-alpha has an important role in the pathogenesis of prostate cancer. Single nucleotide polymorphisms in the promoter region of the TNF-A gene alter tumor necrosis factor-alpha transcription. Thus, we studied the association of 4 SNPs in the promoter region of TNF-A gene, including -1031T>C, -863C>A, -857 C>T and -308 G>A, in a North Indian cohort of patients with prostate cancer. MATERIALS AND METHODS: The study involved 453 subjects. All 197 case and 256 control samples were genotyped for the 4 promoter polymorphisms in the TNF-A gene using allele specific polymerase chain reaction and polymerase chain reaction-restriction fragment length polymorphism. RESULTS: Results showed an increased risk of prostate cancer for the TNF-A -1031 CC genotype (OR 2.01, p = 0.03). No significant association was observed for the TNF-A -863 C>A, TNF-A -857 C>T or -308 G>A polymorphisms. Haplotype analysis revealed that TNF-A -1031C-863C-857T-308G was significantly associated with prostate cancer risk (OR 2.22, p = 0.013). Moreover, the TNF-A -1031 C and -857 T alleles were associated with higher tumor grade and an increased risk of tumor progression and metastasis. CONCLUSIONS: These results show that TNF-A polymorphisms have an important role in prostate cancer pathogenesis. Results are in line with findings in other studies from the West and to our knowledge for the first time from India indicating the involvement of immune system genes in prostate cancer pathogenesis.

GSTM1, GSTM3 and GSTT1 gene variants and risk of benign prostate hyperplasia in North India.

Glutathione S-transferases (GSTs) play an important role in detoxification of various toxic compounds like carcinogens in cigarette smoke and tobacco by conjugating to toxic compounds and inactivating their hazardous effect. Variation in Glutathione S-Transferases (GSTs) genes may alter the catalytic efficiency of GST isoenzymes leading to potential increase in cancer susceptibility due to various carcinogens. We therefore, investigated association of GSTM1, GSTM3 and GSTT1 variants with susceptibility to benign prostate hyperplasia (BPH) and cigarette, tobacco chewing and alcohol consumption as confounding factors in 141 BPH and 184 healthy controls. Results showed increased risk for BPH susceptibility in patients with GSTM1 null genotype (OR-2.03, p = 0.013) and smoking (OR-3.12, p = 0.028), tobacco chewing (OR-2.54, p = 0.039) and alcohol habits (OR-3.39, p = 0.010). Null genotype of GSTM1 with cigarette, tobacco and alcohol habits predisposed increased risk for BPH.

Association of tumour necrosis factor-alpha gene (T-1031C, C-863A, and C-857T) polymorphisms with bladder cancer susceptibility and outcome after bacille Calmette-Guérin immunotherapy.

OBJECTIVE: To investigate the association of tumour necrosis factor-alpha gene (TNF-alpha) polymorphisms T-1031C, C-863A, and C-857T with bladder cancer risk and recurrence after bacille Calmette-Guérin (BCG) immunotherapy, as TNF-alpha regulates inflammatory process influencing bladder cancer susceptibility and outcome of BCG immunotherapy. PATIENTS AND METHODS: In all, 220 patients with bladder cancer and 206 controls were recruited. Genotyping was done using allele specific-polymerase chain reaction. RESULTS: A T-1031C, CC genotype and haplotype -1031C/-863C/-857T showed enhanced susceptibility to bladder cancer, with an odds ratio (OR) of 2.23 and 95% confidence interval (CI) of 1.17-4.26; and an OR of 6.05 and 95%CI of 2.46-14.90, respectively. A T-1031C, CC genotype had a reduced risk of recurrence after BCG treatment (hazard ratio 0.38, 95%CI 0.14-0.98). CONCLUSION: The present data suggests that T-1031C (CC) genotype and C/C/T haplotype may confer risk for bladder cancer, moreover T-1031C (CC) decreased the risk of recurrence after BCG immunotherapy.

IL-10 -1082 G>A: a risk for prostate cancer but may be protective against progression of prostate cancer in North Indian cohort.

BACKGROUND: Chronic intraprostatic inflammation is suspected to play a major role in the pathogenesis of prostate cancer (PCa). Polymorphisms in interleukin-10 (IL-10), a key anti-inflammatory cytokine gene can influence immune response and immune evasion of tumor cells. Its role as an anti-metastatic molecule is also well documented. METHODS: Gene promoter polymorphisms in IL-10 (-1082 G>A and -819 C>T) was analyzed in 159 PCa patients and 259 healthy controls to investigate their potential association with susceptibility for PCa. RESULTS: Our results indicated that the heterozygous (GA) and homozygous mutant (AA) genotypes of IL-10 -1082 to be more prevalent among PCa patients in comparison to controls (GA: OR - 2.8, p = 0.011; AA: OR - 2.3, p = 0.037). More patients (92.5%) than controls (82.7%) were positive for the A allele (GA + AA: OR - 2.6, p = 0.015). We observed lower frequency of T(-819)-G(-1082) haplotype in patients without bone metastasis (4.4%, OR - 0.30, p = 0.019) in comparison to PCa patients with bone metastasis (12.6%). CONCLUSION: Our results support the emerging hypothesis that genetically determined immune activity may play a role in the pathophysiology of PCa. Our findings of high producer of IL-10 -1082 variants suggest initiation of PCa. Future studies in large cohort of different ethnicity PCa groups are warranted to establish definite associations with other cytokine gene polymorphisms.

Influence of genetic polymorphisms in GSTM1, GSTM3, GSTT1 and GSTP1 on allograft outcome in renal transplant recipients.

INTRODUCTION: Glutathione S-transferases (GSTs) are important in protection against xenobiotic compounds and toxicity caused by immunosuppressants in renal transplant recipients. In the present study we hypothesize that genetic variability in GSTM1, GSTM3, GSTP1 and GSTT1 genes may be associated with allograft outcome. METHODS: The study included 223 controls and 273 transplant recipients categorized into 184 stable graft function (SGF), 57 rejection episodes (RE) and 32 delayed graft function (DGF). The polymorphism was studied using multiplex PCR and PCR-RFLP. RESULTS: GSTM1 null genotype showed a 3.35-fold higher risk for rejection in SGF vs. RE category [95% confidence interval (CI) 1.27-8.84, p = 0.014]. Mutant (G) allele of GSTP1 was associated with a 5.52-fold risk for DGF (95% CI 1.37-22.17, p = 0.016). Kaplan-Meier analysis revealed significantly lower mean time to first RE in null genotype as compared with GSTM1 present patients (Log p = 0.002). The dose adjusted C(2) levels in null genotype was higher as compared with GSTM1 present patients at one (p = 0.007) and three months (p = 0.027) post transplantation. CONCLUSION: Patients with variant genotype of GSTM1 and GSTP1 were at higher risk for rejection and delayed functioning of the allograft, respectively, supporting the hypothesis for involvement of GST isoform variants in allograft outcome in renal transplant recipients.

Association of GSTM3 intron 6 variant with cigarette smoking, tobacco chewing and alcohol as modifier factors for prostate cancer risk.

Variations in glutathione-S-transferases (GSTs) genes may alter the catalytic efficiency of GST isoenzymes leading to potential increase in susceptibility to carcinogens present in cigarette smoke and tobacco. The present study aimed to explore the association of GSTM3 intron 6 polymorphism with susceptibility to prostate cancer (PCa), and to assess risks associated with cigarette smoking, tobacco chewing and alcohol consumption in PCa patients of North India. The study included 135 PCa patients and 169 controls. All subjects were genotyped for 3-bp deletion in intron 6 of GSTM3. Risk of developing prostate cancer associated with GSTM3 AB + BB was 2.5-fold (OR = 2.51, P = 0.028) as compared to AA genotype. Patients who were either smokers and/or had alcohol habits demonstrated a strong association with GSTM3 (AB + BB) genotype (OR = 4.11, P = 0.046; OR = 4.38, P = 0.027, respectively). Our results suggested GSTM3 (AB + BB) genotype to be significantly associated with PCa risk. The risk was even more apparent in case of cigarette smokers and alcohol consumers.

Integrative cross-platform analyses identify enhanced heterotrophy as a metabolic hallmark in glioblastoma.

BACKGROUND: Although considerable progress has been made in understanding molecular alterations driving gliomagenesis, the diverse metabolic programs contributing to the aggressive phenotype of glioblastoma remain unclear. The aim of this study was to define and provide molecular context to metabolic reprogramming driving gliomagenesis. METHODS: Integrative cross-platform analyses coupling global metabolomic profiling with genomics in patient-derived glioma (low-grade astrocytoma [LGA; n = 28] and glioblastoma [n = 80]) were performed. Identified programs were then metabolomically, genomically, and functionally evaluated in preclinical models. RESULTS: Clear metabolic programs were identified differentiating LGA from glioblastoma, with aberrant lipid, peptide, and amino acid metabolism representing dominant metabolic nodes associated with malignant transformation. Although the metabolomic profiles of glioblastoma and LGA appeared mutually exclusive, considerable metabolic heterogeneity was observed in glioblastoma. Surprisingly, integrative analyses demonstrated that O6-methylguanine-DNA methyltransferase methylation and isocitrate dehydrogenase mutation status were equally distributed among glioblastoma metabolic profiles. Transcriptional subtypes, on the other hand, tightly clustered by their metabolomic signature, with proneural and mesenchymal tumor profiles being mutually exclusive. Integrating these metabolic phenotypes with gene expression analyses uncovered tightly orchestrated and highly redundant transcriptional programs designed to support the observed metabolic programs by actively importing these biochemical substrates from the microenvironment, contributing to a state of enhanced metabolic heterotrophy. These findings were metabolomically, genomically, and functionally recapitulated in preclinical models. CONCLUSION: Despite disparate molecular pathways driving the progression of glioblastoma, metabolic programs designed to maintain its aggressive phenotype remain conserved. This contributes to a state of enhanced metabolic heterotrophy supporting survival in diverse microenvironments implicit in this malignancy.

ABCB1 G2677 allele is associated with high dose requirement of cyclosporin A to prevent renal allograft rejection in North India.

BACKGROUND: Interindividual heterogeneity in expression of ABCB1 gene has been suspected to be one of the factors resulting in cyclosporin (CsA) pharmacokinetic variation. The present study explored the association of ABCB1 SNPs on CsA dose requirements and dose-adjusted C2 levels (CsA level/daily dose requirement) in renal allograft recipients. METHODS: Daily doses (mg/kg/day) and dose-adjusted C2 levels (microg/mL per mg/kg/day) at 1 and 3 months for 155 recipients on CsA therapy were compared according to allelic status of ABCB1 c.1236C>T, c. 2064-76T>A, c.2677G>T and c.3435C>T. RESULTS: Dose-adjusted C2 levels were lower in ABCB1 c.2677G>T GG genotype as compared to GT/TT genotypes at 1 and 3 months, suggesting that for a given dose their CsA blood concentration is lower (p=0.009 and p=0.043). GG genotype was further associated with lower allograft survival as revealed by Kaplan-Meier analysis (p=0.021). CONCLUSIONS: Identification of ABCB12677GG patients may have a clinically significant impact on allograft outcome and may be helpful in providing pre-transplant pharmacogenetic information to individualize CsA dosing.

Tryptophan Metabolism Contributes to Radiation-Induced Immune Checkpoint Reactivation in Glioblastoma.

Purpose: Immune checkpoint inhibitors designed to revert tumor-induced immunosuppression have emerged as potent anticancer therapies. Tryptophan metabolism represents an immune checkpoint, and targeting this pathway's rate-limiting enzyme IDO1 is actively being investigated clinically. Here, we studied the intermediary metabolism of tryptophan metabolism in glioblastoma and evaluated the activity of the IDO1 inhibitor GDC-0919, both alone and in combination with radiation (RT).Experimental Design: LC/GC-MS and expression profiling was performed for metabolomic and genomic analyses of patient-derived glioma. Immunocompetent mice were injected orthotopically with genetically engineered murine glioma cells and treated with GDC-0919 alone or combined with RT. Flow cytometry was performed on isolated tumors to determine immune consequences of individual treatments.Results: Integrated cross-platform analyses coupling global metabolomic and gene expression profiling identified aberrant tryptophan metabolism as a metabolic node specific to the mesenchymal and classical subtypes of glioblastoma. GDC-0919 demonstrated potent inhibition of this node and effectively crossed the blood-brain barrier. Although GDC-0919 as a single agent did not demonstrate antitumor activity, it had a strong potential for enhancing RT response in glioblastoma, which was further augmented with a hypofractionated regimen. RT response in glioblastoma involves immune stimulation, reflected by increases in activated and cytotoxic T cells, which was balanced by immune checkpoint reactivation, reflected by an increase in IDO1 expression and regulatory T cells (Treg). GDC-0919 mitigated RT-induced Tregs and enhanced T-cell activation.Conclusions: Tryptophan metabolism represents a metabolic node in glioblastoma, and combining RT with IDO1 inhibition enhances therapeutic response by mitigating RT-induced immunosuppression. Clin Cancer Res; 24(15); 3632-43. ©2018 AACR.

The interplay between metabolic remodeling and immune regulation in glioblastoma.

The fields of tumor metabolism and immune oncology have both independently received considerable attention over the last several years. The majority of research in tumor metabolism has largely focused on the Warburg effect and its resulting biologic consequences, including energy and macromolecule production. However, recent investigations have identified elegant, multifaceted strategies by which alterations in tumor metabolism can also contribute to a potent tolerogenic immune environment. One of the most notable is increased tryptophan metabolism through activation of indoleamine 2,3-dioxygenase 1 (IDO1) and tryptophan 2,3-dioxygenase (TDO). However, this pathway represents one of numerous metabolic pathways that may modulate the immune system. For example, metabolites associated with aerobic glycolysis, adenosine, arginine, and prostaglandin metabolism have all been implicated in cancer-mediated immune tolerance and represent attractive therapeutic targets. In this review, we will provide an overview of the emerging interface between these 2 timely areas of cancer research and provide an overview of strategies currently being tested to target these next-generation metabolic immune checkpoints.