TROP2 Is Associated with Primary Resistance to Immune Checkpoint Inhibition in Patients with Advanced Non-Small Cell Lung Cancer

PURPOSE

Mechanisms of primary resistance to inhibitors of the programmed cell death-1 (PD-1)/programmed death-ligand 1 (PD-L1) signaling axis in non-small cell lung cancer (NSCLC) are still poorly understood. While some studies suggest the involvement of trophoblast cell surface antigen 2 (TROP2) in modulating tumor cell resistance to therapeutic drugs, its specific role in the context of PD-1/PD-L1 axis blockade is not definitively established.

EXPERIMENTAL DESIGN

We performed high-throughput analysis of transcriptomic data from 891 NSCLC tumors from patients treated with either the PD-L1 inhibitor atezolizumab or chemotherapy in two large randomized clinical trials. To confirm our results at the protein level, we complemented this transcriptional approach by performing a multiplex immunofluorescence analysis of tumor tissue samples as well as a proteomic profiling of plasma.

RESULTS

We observed a significant association of TROP2 overexpression with worse progression-free survival and overall survival on PD-L1 blockade, independent of other prognostic factors. Importantly, we found increased TROP2 expression to be predictive of survival in patients treated with atezolizumab but not chemotherapy. TROP2 overexpression was associated with decreased T-cell infiltration. We confirmed these results at the proteomic level both on tumor tissue and in plasma.

CONCLUSIONS

Our results suggest an important contribution of TROP2 expression to the primary resistance to PD-L1 blockade in NSCLC. TROP2-biomarker-based strategy may be relevant in selecting patients with NSCLC who are more likely to benefit from a combination of immunotherapy and an anti-TROP2 agent.

Upregulation of Indoleamine 2,3-Dioxygenase 1 in Tumor Cells and Tertiary Lymphoid Structures is a Hallmark of Inflamed Non-Small Cell Lung Cancer

PURPOSE

Overexpression of the tryptophan-catabolizing enzyme indoleamine 2,3-dioxygenase 1 (IDO1) has been reported in several tumor types, including non-small cell lung cancer (NSCLC), and has been shown to promote tumor-immune evasion and inhibit T-cell activation through increased tryptophan degradation and the production of several immunosuppressive metabolites collectively known as kynurenines. However, it remains unclear whether IDO1 expression by tumor cells is detrimental specifically in the context of programmed cell death protein 1 (PD-1)/programmed death ligand 1 (PD-L1) axis blockade.

EXPERIMENTAL DESIGN

We analyzed the transcriptome of 891 NSCLC tumor samples from patients enrolled in two large randomized clinical trials investigating the safety and activity of atezolizumab, a humanized IgG1 mAb that targets PD-L1, versus docetaxel in patients with advanced NSCLC. We complemented these transcriptomics results at the protein level by using multiplex immunofluorescence and at the functional level with in vitro experiments.

RESULTS

The increased expression of the tryptophan-catabolizing enzyme IDO1 was significantly associated with improved objective response, progression-free survival, and overall survival in patients treated with PD-L1 inhibitors, but not in those treated with chemotherapy. Strikingly, inflamed tumors had higher levels of IDO1, and IDO1 was also expressed in tertiary lymphoid structures (TLS) by mature follicular dendritic cells. L-kynurenine impaired the differentiation of antibody-producing B cells induced by follicular helper T (Tfh)/B-cell interactions, a hallmark process within TLS.

CONCLUSIONS

IDO1 pathway in NSCLC is driven by the immune system rather than by tumor cells. Targeting IDO1 in combination with anti-PD-1/PD-L1 might be beneficial only in patients with inflamed tumors and particularly in those bearing TLS.

Abstract 4705: Profiling of immune cell components and soluble factors in ovarian cancer ascites highlights impaired immune environment

Background: It’s now increasingly recognized that ovarian cancer (OC) ascites play a significant role in OC progression - behavior of tumor cells is influenced by the nature of their surrounding microenvironment. Thus, characterization of ascites composition is essential to understand how this milieu affects tumor progression and particularly the immunosuppressive pathways that would underlie immune response dysfunctions and, in turn, how biological ascites effects can be influenced by that composition.

Methods: Ascites samples were collected from advanced OC patients. Through respective multiplexed approaches of flow cytometry-based marker expression analysis and quantitation of mediators, immune context was profiled by investigating immune cell composition and levels of a plethora of soluble factors, including cytokines/chemokines, and metabolic pathways of some amino acids known to be involved in immunosuppression. Furthermore, ascites fluids were functionally screened for their biological effects on healthy monocytes, either undifferentiated or undergoing M1 polarization.

Results: Unlike healthy PBMCs, OC ascites were mostly “enriched” in regulatory/immunosuppressive immune cell subsets including T and myeloid populations. Also, T cells were shown to highly express immune checkpoints such as PD1 in T cells and TIGIT in Tregs. Intriguingly, a high CD4/CD8 ratio was seen. Also, CD163+ tumor-associated macrophages were shown to express CSF1R, CCR8 and CCR2, and to even display a mixed phenotype since also expressing Arg1, CD80, and iNOS. On acellular fractions, most ascites demonstrated elevated CCL18, IL6, LIF, VEGF, and CCL2 levels, and low IL2, IL4, and IL17 levels. Interestingly, unlike healthy plasmas, these ascites appeared to harbor a metabolically-immunosuppressive profile characterized by high glutaminolysis and tryptophan (Trp) degradation in kynurenine (Kyn). Functionally, we demonstrated that not only ascites basically polarized monocytes into M2 macrophages, but even antagonized with their M1 polarization to ultimately tilt to M2 status.

Conclusions: Taken together, our data show that ascites fluids most favorable to the M2 phenotype were associated with high LIF, VEGF, IL6, CCL2, and CCL18 levels, and with elevated Kyn to Trp ratios - Kyn levels being strongly higher than in healthy plasmas. Our results thus highlight a peculiar altered environment of OC ascites where a mixture of suppressive cells and signaling factors mediate extracellular cues leading to immune cell activity dysfunction. Altogether, these translational findings highlight OC ascites as a valuable tool to understand the mechanisms of suppression and develop predictive profiles, and to provide new insights for the identification of new targets and development of targeted-therapies.

Citation Format: Assia Chaibi, Coriolan Lebreton, Dominique Bodet, Jean-Philippe Guegan, Guillaume Babin, Antoine Italiano, Alban Bessede, Imane Nafia. Profiling of immune cell components and soluble factors in ovarian cancer ascites highlights impaired immune environment. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4705.

Circulating L-Arginine predicts the survival of cancer patients treated with immune checkpoint inhibitors

BACKGROUND

The discovery of immune checkpoint inhibitors (ICIs) has revolutionized the systemic approach to cancer treatment. However, most patients receiving ICIs do not derive benefits. Therefore, it is crucial to identify reliable predictive biomarkers of response to ICIs. One important pathway in regulating immune cell reactivity is L-arginine (ARG) metabolism, essential to T-cell activation. We therefore aimed to evaluate the association between baseline plasma ARG levels and the clinical benefit of ICIs.

PATIENTS AND METHODS

The correlation between ARG levels and clinical ICI activity was assessed by analyzing plasma samples obtained before treatment onset in two independent cohorts of patients with advanced cancer included in two institutional molecular profiling programs (BIP, NCT02534649, n = 77; PREMIS, NCT03984318, n = 296) and from patients in a phase 1 first-in-human study of budigalimab monotherapy (NCT03000257). Additionally, the correlation between ARG levels and ICI efficacy in preclinical settings was evaluated using a syngeneic mouse model of colorectal cancer responsive to ICIs. Using matched PBMC plasma samples, we analyzed the correlation between ARG levels and PBMC features through multiplexed flow cytometry analysis.

RESULTS

In both discovery and validation cohorts, low ARG levels at baseline (<42 μM) were significantly and independently associated with a worse clinical benefit rate, progression-free survival, and overall survival. Moreover, at the preclinical level, the tumor rejection rate was significantly higher in mice with high baseline ARG levels than in those with low ARG levels (85.7% versus 23.8%; P = 0.004). Finally, PBMC immunophenotyping showed that low ARG levels were significantly associated with increased PD-L1 expression in several immune cell subsets from the myeloid lineage.

CONCLUSION

We demonstrate that baseline ARG levels predict ICI response. Plasma ARG quantification may therefore represent an attractive biomarker to tailor novel therapeutic regimens targeting the ARG pathway in combination with ICIs.

Abstract 2527: Ovarian cancer ascites display altered immune environment featured by enhanced soluble factors and suppressive cellular context

Background: Tumor microenvironment (TME) of epithelial ovarian cancer is unique among solid tumors as tumor cells create their "malignant ascites" TME. These ascites, acting as a complex mixture of soluble factors and cell components, are known to be rich in macrophages which were suggested to skew to a M2-like phenotype involved in resistance and metastases. However, while macrophages can adopt different phenotypes, it's now postulated that tumor-associated macrophages (TAM) from ovarian cancer patient ascites may even acquire mixed M1/M2 properties, providing a particular pro-inflammatory and tumor-promoting microenvironment. Characterization of cell composition along with the growth factors present in the microenvironment is thus crucial to understand ovarian cancer biology and more particularly the immunosuppressive pathways that would underlie the altered immune cell activity.

Methods & Results: Through flow cytometry-based marker expression analysis and quantitation of soluble mediators in ovarian cancer ascites, we investigated here the cell component nature as well as the presence of several growth factors. While these ascites were interestingly enriched in major "immunosuppressive" cell subsets including T and myeloid populations, TAM were intriguingly shown to display a mixed phenotype characterized by high expression of CD163, unrelated to M1/M2 categorization since also expressing Arg1, CD80, and iNOS markers. The immunosuppressive phenotype was also linked to IL6, LIF and IL10 among other factors present in the ascitic environment. In order to assess their role in the occurrence of such an immunosuppressive cell status, soluble mediators were then investigated on healthy monocytes undergoing M1 polarization. We demonstrated that, while LIF did not directly affect IL6 and IL10 levels released by the cells, interestingly IL6 alone or in co-presence with LIF decreased IL6 supernatant content, with respect to the control. These changes were concomitant with a decrease and increase in the expression of CD80 and CD163, respectively. Furthermore, CD14 and CD206 were found to increase in the presence of IL6+/-LIF.

Conclusion: All these data highlight a switching activity of IL6 skewing cells from M1 polarization and resulting in a proper macrophage phenotype exhibiting a mixed M1/M2 status and would suggest these ascite-containing factors as keys conferring an immunosuppressive cell phenotype. Altogether, these translational findings highlight ovarian patient-derived ascites as a valuable tool to understand the mechanisms of suppression and to allow for the identification of novel markers to develop innovative targeted therapies.

Citation Format: Imane Nafia, Assia Chaibi, Christophe Rey, Jean-Philippe Guegan, Alban Bessede, Coriolan Lebreton, Antoine Italiano. Ovarian cancer ascites display altered immune environment featured by enhanced soluble factors and suppressive cellular context [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2527.

Abstract 622: Development and characterization of a novel anti-PD1 resistant sarcoma mouse model

Background: Soft Tissue Sarcoma (STS) is known to be resistant to cancer immunotherapy including the prototypical immune checkpoint inhibitor (ICI) anti-PD1 (1). It’s therefore crucial to develop innovative strategies aiming at improving current clinical benefit. To this end, a well-characterized sarcoma preclinical model that mimics resistance to immunotherapy is needed. Starting from the anti-PD(L)1-sensitive MCA205 sarcoma mouse model, we therefore aimed at developing and characterizing a novel model resistant to anti-PD1.

Methods: Anti-PDL1 antibody was first administered to the ICI-sensitive MCA205 mouse sarcoma model (MCA205-S) and tumor growth was followed overtime. Tumor from a “non-responder” animal - tumor growth profile being similar as in the vehicle group - was then retrieved and processed for tissue dissociation and cell culture. Tumor cells were then amplified and inoculated into immunocompetent C57BL/6 mice that were exposed or not to anti-PD1 antibody, and tumor growth was monitored for a 8-week period. In addition, tumor samples from satellite animals were collected and processed for intratumoral immune landscape characterization by multiparametric flow cytometry as well as for gene expression analysis by RNA sequencing.

Results: While anti-PD1 antibody demonstrated a strong anti-tumor effect in MCA205-S tumor-bearing mice, administration of anti-PD1 to the mice inoculated with the non-responder mouse-originating MCA205 cells did not yield to a significant anti-tumor effect thereby validating the resistant profile of this new MCA205-R cell line. Flow cytometry analysis of tumor-infiltrated immune cells revealed a higher abundance of macrophages (defined as CD11b+/F4:80+) in MCA205-R when compared to the MCA205-S model, which more likely harbor a M2 phenotype. Also, anti-PD1 treatment favored an important MCA205-R tumor infiltration by gMDSC which was more limited in the MCA205-S model. Gene expression profile of tumor samples is currently under investigation.

Conclusions: We developed and validated a novel preclinical mouse model of sarcoma (MCA205-R) characterized by its resistance to anti-PD1 and a high tumor infiltration by macrophages. This model - more reflecting the clinic in terms of immunotherapy sensitivity - can thus serve to evaluate novel immunotherapeutic regimens either alone or in combination with reference ICI, to ultimately translate into clinical benefit for STS patients treated with immunotherapy.

Citation Format: Imane Nafia, Jean-Philippe Guegan, Assia Chaibi, Noëlie Bos, Doriane Bortolotto, Christophe Rey, Loïc Cerf, Florent Peyraud, Antoine Italiano, Alban Bessede. Development and characterization of a novel anti-PD1 resistant sarcoma mouse model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 622.

Impact of acetaminophen on the efficacy of immunotherapy in patients with cancer

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Background: Pain is the most common symptom experienced by patients with advanced cancer. Acetaminophen (APAP, commonly known as paracetamol) alone or in combination with a weak opioid, such as codeine or tramadol, is usually considered as the first-line strategy to manage mild-to-moderate pain in this setting. Although generally considered to be safe, several evidences suggest that APAP may have negative immunomodulatory effects. Randomized studies have shown that APAP use is associated with blunted vaccine immune responses. Given its potential to impair vaccine effectiveness, the World Health Organization stated in 2015 that administration of APAP before or at the time of vaccination is not recommended. This study aimed to assess APAP impact on efficacy of immunotherapy in patients with cancer. Methods: Exposure to APAP was assessed by plasma analysis and was correlated with clinical outcome in three independent cohorts of patients with advanced cancer who were treated with immune checkpoint blockers (ICB): the CheckMate 025 trial, n = 297 (NCT01668784, sponsor: Bristol Myers Squibb), the institutional biomarker program BIP n = 34 (NCT02534649, sponsor: Institut Bergonié, Bordeaux, France) and the institutional biomarker program PREMIS n = 297 (NCT03984318, sponsor: Gustave Roussy, Villejuif, France). APAP immunomodulatory effects were evaluated on a pre-clinical tumor model (MC38) and on human peripheral blood mononuclear cells (PBMCs) from healthy donors. Results: Detectable plasma APAP levels at treatment onset was associated with a significantly worse clinical outcome in ICB-treated cancer patients (HR for progression-free survival : 1.43, 95% CI 1.07–1.91, p = 0.015; HR for overall survival: 1.78 95% CI 1.18–2.68, p = 0.006), independently of other prognostic factors (age, performance status, number of previous lines of treatment, tumor type, number of metastatic sites, presence of liver metastases, LDH levels). APAP significantly reduced ICB efficacy in the pre-clinical MC38 model, as well as the production of PD1 blockade-related interferon-γ secretion by human PBMCs. Moreover, reduction of ICB efficacy in vivo was associated with significantly increased tumor infiltration by regulatory T cells (Tregs). Administration of APAP over 24 h induced a significant expansion of peripheral Tregs in healthy individuals. In addition, interleukin-10, a crucial mediator of Treg-induced immune suppression, was significantly upregulated upon treatment with ICB in cancer patients taking APAP. Conclusions: This study provides strong pre-clinical and clinical evidence of the role of APAP as a potential suppressor of antitumor immunity. Hence, APAP should be used with caution in patients treated with ICB.

Impact of acetaminophen on the efficacy of immunotherapy in cancer patients

BACKGROUND

Acetaminophen (APAP) use has been associated with blunted vaccine immune responses. This study aimed to assess APAP impact on immunotherapy efficacy in patients with cancer.

PATIENTS AND METHODS

Exposure to APAP was assessed by plasma analysis and was correlated with clinical outcome in three independent cohorts of patients with advanced cancer who were treated with immune checkpoint blockers (ICB). APAP immunomodulatory effects were evaluated on a pre-clinical tumor model and on human peripheral blood mononuclear cells (PBMCs) from healthy donors.

RESULTS

Detectable plasma APAP levels at treatment onset was associated with a significantly worse clinical outcome in ICB-treated cancer patients, independently of other prognostic factors. APAP significantly reduced ICB efficacy in the pre-clinical MC38 model, as well as the production of PD1 blockade-related interferon-γ secretion by human PBMCs. Moreover, reduction of ICB efficacy in vivo was associated with significantly increased tumor infiltration by regulatory T cells (Tregs). Administration of APAP over 24 h induced a significant expansion of peripheral Tregs in healthy individuals. In addition, interleukin-10, a crucial mediator of Treg-induced immune suppression, was significantly upregulated upon treatment with ICB in cancer patients taking APAP.

CONCLUSION

This study provides strong pre-clinical and clinical evidence of the role of APAP as a potential suppressor of antitumor immunity. Hence, APAP should be used with caution in patients treated with ICB.

Fucoidan Independently Enhances Activity in Human Immune Cells and Has a Cytostatic Effect on Prostate Cancer Cells in the Presence of Nivolumab

Fucoidan compounds may increase immune activity and are known to have cancer inhibitory effects in vitro and in vivo. In this study, we aimed to investigate the effect of fucoidan compounds on ex vivo human peripheral blood mononuclear cells (PBMCs), and to determine their cancer cell killing activity both solely, and in combination with an immune-checkpoint inhibitor drug, Nivolumab. Proliferation of PBMCs and interferon gamma (IFNγ) release were assessed in the presence of fucoidan compounds extracted from Fucus vesiculosus, Undaria pinnatifida and Macrocystis pyrifera. Total cell numbers and cell killing activity were assessed using a hormone resistant prostate cancer cell line, PC3. All fucoidan compounds activated PBMCs, and increased the effects of Nivolumab. All fucoidan compounds had significant direct cytostatic effects on PC3 cells, reducing cancer cell numbers, and PBMCs exhibited cell killing activity as measured by apoptosis. However, there was no fucoidan mediated increase in the cell killing activity. In conclusion, fucoidan compounds promoted proliferation and activity of PBMCs and added to the effects of Nivolumab. Fucoidan compounds all had a direct cytostatic effect on PC3 cells, as shown through their proliferation reduction, while their killing was not increased.

Plasma proteomics identifies leukemia inhibitory factor (LIF) as a novel predictive biomarker of immune-checkpoint blockade resistance

BACKGROUND

Immune checkpoint blockers (ICBs) are now widely used in oncology. Most patients, however, do not derive benefit from these agents. Therefore, there is a crucial need to identify novel and reliable biomarkers of resistance to such treatments in order to prescribe potentially toxic and costly treatments only to patients with expected therapeutic benefits. In the wake of genomics, the study of proteins is now emerging as the new frontier for understanding real-time human biology.

PATIENTS AND METHODS

We analyzed the proteome of plasma samples, collected before treatment onset, from two independent prospective cohorts of cancer patients treated with ICB (discovery cohort n = 95, validation cohort n = 292). We then investigated the correlation between protein plasma levels, clinical benefit rate, progression-free survival and overall survival by Cox proportional hazards models.

RESULTS

By using an unbiased proteomics approach, we show that, in both discovery and validation cohorts, elevated baseline serum level of leukemia inhibitory factor (LIF) is associated with a poor clinical outcome in cancer patients treated with ICB, independently of other prognostic factors. We also demonstrated that the circulating level of LIF is inversely correlated with the presence of tertiary lymphoid structures in the tumor microenvironment.

CONCLUSION

This novel clinical dataset brings strong evidence for the role of LIF as a potential suppressor of antitumor immunity and suggests that targeting LIF or its pathway may represent a promising approach to improve efficacy of cancer immunotherapy in combination with ICB.

Abstract 6697: DT095895, a selective EP4 receptor antagonist with monotherapy efficacy in syngeneic mouse model(s) and best-in-class properties

Elevated levels of Prostaglandin E2 (PGE2), an eicosanoid notably synthesized by the cyclooxygenase-2 (COX-2), exert strong immunosuppressive effects in the tumor microenvironment. COX-2-positive solid tumors have the ability to use this pathway as a resistance mechanism, especially to escape from the host immune system, thus limiting the anti-tumor effects of immune checkpoint inhibitors (ICI). These immunosuppressive effects are largely mediated by the EP4 receptor, expressed on multiple immune cells. A novel series of EP4 receptor antagonists has been developed, with improved pharmacokinetic properties when compared to the EP4 receptor antagonists currently being evaluated in clinical trials. An intensive lead optimization program led to the identification of DT095895, a small molecule development candidate with a “best-in class” potential. Its preclinical package will be presented in the poster. DT095895 was assessed in multiple syngeneic mouse tumor models selected for their COX-2 expression profile. Efficacy was seen both in a monotherapy setting, as well as in combination with ICI. Additionally, a specific biomarker program was implemented and validated in order to show target engagement. A phospho-flow murine whole blood assay was set up to assess the ability of DT095895 to inhibit CREB phosphorylation induced by a selective EP4 receptor agonist in CD3+ cells. This biomarker was further developed for human whole blood to support Phase 1 and clinical trials studies. In conclusion, DT095895 is a selective EP4 receptor antagonist and demonstrates strong anti-tumor effects in multiple syngeneic mouse tumor models, both as a monotherapy and in combination with ICI, through the inhibition of the PGE2-induced immunosuppression. DT095895 progresses in regulatory development.

Citation Format: Anne-Laure Blayo, Laurène Deshons, Alexia Dumont, Christel Franchet, Célia Halter, Ludovic Herbin, Gaël Hommet, Stanislas Mayer, Alban Bessede, Imane Nafia, Marjorie Sidhoum, Xavier Leroy, Stephan Schann. DT095895, a selective EP4 receptor antagonist with monotherapy efficacy in syngeneic mouse model(s) and best-in-class properties [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6697.

Abstract 3938: Anti-angiogenic therapy combination with hypoxia-regulating agent leads to improved tumor regression in a murine model or renal carcinoma

Background: While antiangiogenic therapies have been shown effective in preclinical and clinical trials, tumors can acquire resistance conferring them the ability to survive and grow under hypoxic conditions, even, induced by antiangiogenic drugs themselves.

Methods: This study investigated the effects of an antiangiogenic strategy and hypoxia-regulating agent, each alone and in combination. Here, we have tested the synergistic activity of the anti-angiogenic agent Sunitinib and the mTOR inhibitor Everolimus in murine syngeneic renal cancer model - renal carcinoma being known as angiogenesis-dependent and hypoxia-driven malignancy. Anti-tumor effects were investigated on tumor growth and survival. Flow cytometry-based immunoprofiling was performed at the peripheral level - blood and spleen - while immunohistofluorescence and quantitative image analysis served to characterize and evaluate tumor immune cell infiltrate, tumor hypoxia, and tumor vascular density/features.

Results: While Sunitinib and more importantly Everolimus led to a significant tumor growth inhibition as single agents, their combination was more effective on tumor regression. At the peripheral level, Sunitinib, but also Everolimus, led each to declines in circulating and splenic myeloid-derived suppressor cells (MDSCs) - depicted as CD11b+/Gr1+, an event that was further optimized upon combination of both agents. In addition, tumor sections analyses showed decreased microvessel density under Sunitinib and combination treatment. Differential modulations of correlative endothelium/pericytes staining and hypoxia degree were also observed upon the different treatments. This study confirms the preclinical efficacy of Sunitinib and a hypoxia regulator in renal tumor model and suggests that limitation of Sunitinib-induced hypoxia through mTOR targeting or with hypoxia regulators represents a suitable strategy to enhance effect of anti-angiogenic agent thereby limiting tumor growth.

Citation Format: Imane Nafia, Assia Chaibi, Doriane Bortolotto, Christophe Rey, Alban Bessede. Anti-angiogenic therapy combination with hypoxia-regulating agent leads to improved tumor regression in a murine model or renal carcinoma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3938.

Abstract 934: “GPCR-ome” modulation upon PD1 / PDL1 axis blockade

Background: Immunotherapy represents a novel weapon within the cancer armamentarium with unprecedented response observed in several indications including among others metastatic melanoma and Lung cancer. However, the limited rate of response accounting for app. 30% requires further optimization and thus calls the interest in elucidating mechanisms underlying sensitivity to immune checkpoint inhibitors. G Protein-Coupled Receptors (GPCRs) are the largest gene family of cell membrane-associated molecules mediating signal transmission, involved in several physiological functions including the shaping of the immune response but their role in tumor biology and particularly in immune evasion and resistance to immunotherapy remains to be elucidated

Methods: Using a preclinical syngeneic mouse model of sarcoma based on the inoculation of murine sarcoma MCA205 cell line, we investigated - besides the evaluation of tumor growth and survival - a large set of GPCRs upon PDL1 or PD1 blockade. Gene expression analysis was performed on tumor samples by mean of RNA sequencing. Data were analyzed using computational methodology including CIBERSORT and GSEA algorithms to evaluate immune cell subset within the tumor and specific gene datasets enrichment respectively. A large set of GPCRs (1412 in total) was then investigated through conventional Differential Gene Expression (DGE) analysis.

Results: PDL1/PD1 axis blockade, using specific antibodies, exhibited a strong anti-tumor effect. As highlighted by CIBERSORT analysis, anti-PD1/PDL1 antibodies triggered a CD8 and activated NK cells infiltration within the tumor. The recruitment of such effectory populations was associated with enrichment in genes from different hallmarks datasets including allograft rejection and interferon signaling thus confirming the induction of an efficient anti-tumor immune response. Concomitantly, this study revealed a significant up-regulation of several GPCRs already known to be involved in immune evasion - including Adenosine, Prostaglandins and chemokines receptors - but also highlighted the modulation of unexpected orphan or peptidic receptors. Altogether, this novel dataset confirms the induction of an effective anti-tumor immune response upon PD1 / PDL1 blockade and highlights the modulation of GPCRs that warrants further investigation to delineate their exact participation in sensitivity to immunotherapy.

Citation Format: Imane Nafia, Xavier Leroy, Loic Cerf, Jean-Philippe Guegan, Anne-Laure Blayo, Antoine Italiano, Stephan Schann, Alban Bessede. “GPCR-ome” modulation upon PD1 / PDL1 axis blockade [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 934.

IDO Targeting in Sarcoma: Biological and Clinical Implications

Sarcomas are heterogeneous malignant mesenchymal neoplasms with limited sensitivity to immunotherapy. We recently demonstrated an increase in Kynurenine Pathway (KP) activity in the plasma of sarcoma patients treated with pembrolizumab. While the KP has already been described to favor immune escape through the degradation of L-Tryptophan and production of metabolites including L-Kynurenine, Indoleamine 2,3 dioxygenase (IDO1), a first rate-limiting enzyme of the KP, still represents an attractive therapeutic target, and its blockade had not yet been investigated in sarcomas. Using immunohistochemistry, IDO1 and CD8, expression profiles were addressed within 203 cases of human sarcomas. At a preclinical level, we investigated the modulation of the KP upon PDL1 blockade in a syngeneic model of sarcoma through mRNA quantification of key KP enzymes within the tumor. Furthermore, in order to evaluate the possible anti-tumor effect of IDO blockade in combination with PDL1 blockade, an innovative IDO inhibitor (GDC-0919) was used. Its effect was first assessed on Kynurenine to Tryptophan ratio at plasmatic level and also within the tumor. Following GDC-0919 treatment, alone or in combination with anti-PDL1 antibody, tumor growth, immune cell infiltration, and gene expression profiling were measured. IDO1 expression was observed in 39.1% of human sarcoma cases and was significantly higher in tumors with high CD8 infiltration. In the pre-clinical setting, blockade of PDL1 led to a strong anti-tumor effect and was associated with an intratumoral inflammatory cytokines signature driven by Ifng but also with a modulation of the KP enzymes including Ido1 and Ido2. IDO1 inhibition using GDC-0919 resulted in (i) a significant decrease of plasmatic Kynurenine to Tryptophan ratio and in (ii) a decrease of tumoral Kynurenine. However, GDC-0919 used alone or combined with anti-PDL1, did not show anti-tumoral activity and did not affect the tumor immune cell infiltrate. In order to elucidate the mechanism(s) underlying the lack of effect of GDC-0919, we analyzed the gene expression profile of intratumoral biopsies. Interestingly, we have found that GDC-0919 induced a downregulation of the expression of pvr and granzymes, and an upregulation of inhba and Dtx4 suggesting a potential role of the IDO pathway in the control of NK function.

Abstract 5716: Functional evidence for an immunosuppressive role of kynurenine in cancer patients

Background: While being neglected for decades, tumor immune escape is now considered as a new paradigm that promotes tumor growth and evasion. Besides the prototypical PD1 / PDL1 axis, several mechanisms has been identified as important actor in immune editing process. Indoleamine 2,3 dioxygenase (IDO1), a first rate-limiting enzyme of the Kynurenine pathway, has been described to favor tolerance and immune escape through the production of a series of metabolites including L-Kynurenine. However, functional evidences have not yet been clearly demonstrated.

Methods: We reconstituted in vitro a human immune - tumor cell synapse where ability of primary immune cells to promote tumor cell death has been kinetically followed through fluorescent-based live cell imaging in the presence and absence of L-Kynurenine. Two different donors as source of Peripheral Blood Mononuclear Cells (PBMCs) and three different tumor cell lines - namely IB115 and IB136 as sarcoma models & H1299 as reference lung adenocarcinoma model - have been used in this study. Finally, in order to determine cancer subtypes that might be highly exposed to Kynurenine pathway dysregulation and associated immune dysfunction, a comprehensive analysis of Kynurenine and Tryptophan levels was done in a series of 691 patients with advanced solid tumors

Results: L-Kynurenine demonstrated a clear propensity to limit the immune cell-mediated tumor apoptosis elicited by TCR ligation - an event that was consistent within the two different donors and the three different cell lines. Interestingly, this immune suppressive feature of L-Kynurenine was associated with a limited amount of gamma-Interferon (IFNγ) in the cell culture supernatant while no effect was observed on Tumor Necrosis Factor alpha (TNFα). It's worth to note that L-Kynurenine had no effect on tumor cells without immune cells thus suggesting that Kynurenine has direct action on immune cells through which it limits their anti-tumor function -The Kyn/Trp ratio in cancer patients was significantly higher than that reported in healthy subjects (median: 71.2, range: 5.8-2825.2). Median value was the highest in breast cancer (126) and the lowest in colorectal (54) and pancreatic cancer (51) patients. No correlation with IDO1 tumor expression neither with systemic markers of inflammation (C-reactive protein) was observed.

In conclusion, these results represent the first large description of the Kynurenine/Tryptophan ratio levels in cancer patients and the first functional evidence of a direct inhibition by Kynurenine of lymphocytes's effector functions.

Citation Format: Alban Bessede, Antoine Italiano, Assia Chaïbi, Christophe Rey, Imane Nafia, Sylvestre le Moulec, Sophie Cousin, Maud Toulmonde, Céline Auzanneau, Marina Pulido. Functional evidence for an immunosuppressive role of kynurenine in cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5716.

Progressive Parkinsonism by acute dysfunction of excitatory amino acid transporters in the rat substantia nigra

Parkinson's disease (PD) is characterized by the progressive degeneration of substantia nigra (SN) dopamine neurons, involving a multifactorial cascade of pathogenic events. Here we explored the hypothesis that dysfunction of excitatory amino acid transporters (EAATs) might be involved. Acutely-induced dysfunction of EAATs in the rat SN, by single unilateral injection of their substrate inhibitor l-trans-pyrrolidine-2,4-dicarboxylate (PDC), triggers a neurodegenerative process mimicking several PD features. Dopamine neurons are selectively affected, consistent with their sustained excitation by PDC measured by slice electrophysiology. The anti-oxidant N-acetylcysteine and the NMDA receptor antagonists ifenprodil and memantine provide neuroprotection. Besides oxidative stress and NMDA receptor-mediated excitotoxicity, glutathione depletion and neuroinflammation characterize the primary insult. Most interestingly, the degeneration progresses overtime with unilateral to bilateral and caudo-rostral evolution. Transient adaptive changes in dopamine function markers in SN and striatum accompany cell loss and axonal dystrophy, respectively. Motor deficits appear when neuron loss exceeds 50% in the most affected SN and striatal dopamine tone is dramatically reduced. These findings outline a functional link between EAAT dysfunction and several PD pathogenic mechanisms/pathological hallmarks, and provide a novel acutely-triggered model of progressive Parkinsonism.

Preferential vulnerability of mesencephalic dopamine neurons to glutamate transporter dysfunction

Nigral depletion of the main brain antioxidant GSH is the earliest biochemical event involved in Parkinson's disease pathogenesis. Its causes are completely unknown but increasing number of evidence suggests that glutamate transporters [excitatory amino acid transporters (EAATs)] are the main route by which GSH precursors may enter the cell. In this study, we report that dopamine (DA) neurons, which express the excitatory amino acid carrier 1, are preferentially affected by EAAT dysfunction when compared with non-DA neurons. In rat embryonic mesencephalic cultures, l-trans-pyrrolidine-2,4-dicarboxylate, a substrate inhibitor of EAATs, is directly and preferentially toxic for DA neurons by decreasing the availability of GSH precursors and lowering their resistance threshold to glutamate excitotoxicity through NMDA-receptors. In adult rat, acute intranigral injection of l-trans-pyrrolidine-2,4-dicarboxylate induces a large regionally selective and dose-dependent loss of DA neurons and alpha-synuclein aggregate formation. These data highlight for the first time the importance of excitatory amino acid carrier 1 function for the maintenance of antioxidant defense in DA neurons and suggest its dysfunction as a candidate mechanism for the selective death of DA neurons such as occurring in Parkinson's disease.

Glutamate leakage from a compartmentalized intracellular metabolic pool and activation of the lipoxygenase pathway mediate oxidative astrocyte death by reversed glutamate transport

Astrocytes have essential roles for neuron survival and function, so that their demise in neurodegenerative insults, such as ischemia, deserves attention. A major event of the cell death cascade in ischemia is the reversed operation of excitatory amino acid transporters (EAAT), releasing glutamate. Cytotoxicity is conventionally attributed to extracellular glutamate accumulation. We previously reported that mimicking such dysfunction by EAAT substrate inhibitors, whose uptake induces glutamate release by heteroexchange, triggers glutathione (GSH) depletion and oxidative death of differentiated astrocytes in culture. Here we demonstrate that astrocyte death, although correlated with glutamate release, is not resulting from high extracellular glutamate-mediated toxicity. L-glutamate per se was gliotoxic only at concentrations much higher than the maximum reached with the potent EAAT substrate inhibitor L-trans-pyrrolidine-2,4-dicarboxylate (PDC), and toxicity was lower. Moreover, high glutamate concentrations offered protection against PDC. Protection was also provided by L-aspartate, which is both transported by EAAT and metabolized into glutamate, and by inhibiting glutamine synthetase, which uses transported glutamate to synthesize glutamine. Neither D-aspartate, a metabolically inert EAAT substrate, nor compounds that can provide glutamate intracellularly but are not EAAT substrates offered protection. Interestingly, only the compounds providing protection prevented PDC-induced GSH depletion. These data strongly suggest that reversed uptake-mediated astrocyte death results from the leakage of glutamate from a compartmentalized intracellular metabolic pool specifically fuelled by EAAT, crucial for preserving GSH contents. In addition, we provide evidence for a minor contribution of the cystine-glutamate antiporter x(c) (-) but a major role of the 5-lipoxygenase pathway in this death mechanism.

[Cerebral oxidative stress: are astrocytes vulnerable to low intracellular glutamate concentrations? Consequences for neuronal viability]

This review describes reactive oxygen species (ROS), their production and effects on crucial biological molecules, the different lines of defense against oxidative stress, with particular attention to glutathione, the main antioxidant in the brain, which neuronal synthesis seems to be dependent on astrocytic precursors. It also focuses on the different ways by which glutamate may induce oxidative stress in the brain. The different mechanisms leading to ROS production, activated during the excitotoxic cascade, are described. Oxidative glutamate toxicity is also briefly described. A novel form of oxidative glutamate toxicity by depletion of transported glutamate that we recently evidenced is detailed. This toxicity induced by pharmacological reversal of glutamate transport, which mimics glutamate transport reversal occurring in ischemia, involves glutathione depletion and oxidative stress, leading to delayed death of cultured striatal astrocytes differentiated by dibutyryl-cAMP, probably through apoptotic processes. Evidence suggesting that this oxidative glutamate toxicity by depletion of transported glutamate is very likely occurring in vivo and its consequences on neuronal survival are discussed.