RESUMO
Follicular lymphoma (FL), the most common indolent non-Hodgkin lymphoma, constitutes a paradigm of immune tumor microenvironment (TME) contribution to disease onset, progression, and heterogenous clinical outcome. Here we present the first FL-Patient Derived Lymphoma Spheroid (FL-PDLS), including fundamental immune actors and features of TME in FL lymph nodes (LNs). FL-PDLS is organized in disc-shaped 3D structures composed of proliferating B and T cells, together with macrophages with an intermediate M1/M2 phenotype. FL-PDLS recapitulates the most relevant B-cell transcriptional pathways present in FL-LN (proliferation, epigenetic regulation, mTOR, adaptive immune system, among others). The T cell compartment in the FL-PDLS preserves CD4 subsets (follicular helper, regulatory, and follicular regulatory), also encompassing the spectrum of activation/exhaustion phenotypes in CD4 and CD8 populations. Moreover, this system is suitable for chemo and immunotherapy testing, recapitulating results obtained in the clinic. FL-PDLS allowed uncovering that soluble galectin-9 limits rituximab, rituximab, plus nivolumab/TIM-3 antitumoral activities. Blocking galectin-9 improves rituximab efficacy, highlighting galectin-9 as a novel immunotherapeutic target in FL. In conclusion, FL-PDLS maintains the crosstalk between malignant B cells and the immune LN-TME and constitutes a robust and multiplexed pre-clinical tool to perform drug screening in a patient-derived system, advancing toward personalized therapeutic approaches.
Assuntos
Galectinas , Linfonodos , Linfoma Folicular , Microambiente Tumoral , Humanos , Linfoma Folicular/imunologia , Linfoma Folicular/patologia , Linfoma Folicular/terapia , Linfonodos/patologia , Linfonodos/imunologia , Microambiente Tumoral/imunologia , Esferoides Celulares , Imunoterapia/métodos , Transdução de Sinais , Células Tumorais CultivadasRESUMO
Mantle cell lymphoma (MCL), a rare and aggressive B-cell non-Hodgkin lymphoma, mainly develops in the lymph node (LN) and creates a protective and immunosuppressive niche that facilitates tumor survival, proliferation and chemoresistance. To capture disease heterogeneity and tumor microenvironment (TME) cues, we have developed the first patient-derived MCL spheroids (MCL-PDLS) that recapitulate tumor oncogenic pathways and immune microenvironment in a multiplexed system that allows easy drug screening, including immunotherapies. MCL spheroids, integrated by tumor B cells, monocytes and autologous T-cells self-organize in disc-shaped structures, where B and T-cells maintain viability and proliferate, and monocytes differentiate into M2-like macrophages. RNA-seq analysis demonstrated that tumor cells recapitulate hallmarks of MCL-LN (proliferation, NF-kB and BCR), with T cells exhibiting an exhaustion profile (PD1, TIM-3 and TIGIT). MCL-PDLS reproduces in vivo responses to ibrutinib and demonstrates that combination of ibrutinib with nivolumab (anti-PD1) may be effective in ibrutinib-resistant cases by engaging an immune response with increased interferon gamma and granzyme B release. In conclusion, MCL-PDLS recapitulates specific MCL-LN features and in vivo responses to ibrutinib, representing a robust tool to study MCL interaction with the immune TME and to perform drug screening in a patient-derived system, advancing toward personalized therapeutic approaches.
Assuntos
Linfoma de Célula do Manto , Humanos , Adulto , Linhagem Celular Tumoral , Linfoma de Célula do Manto/patologia , Resistencia a Medicamentos Antineoplásicos , Adenina/uso terapêutico , Microambiente TumoralRESUMO
Microenvironment contributes to follicular lymphoma (FL) pathogenesis and impacts survival with macrophages playing a controversial role. In the present study, using FL primary samples and HK follicular dendritic cells (FDC) to mimic the germinal center, together with mouse models, we have analyzed the three-way crosstalk of FL-FDC-macrophages and derived therapeutic opportunities. Ex vivo primary FL-FDC co-cultures (n = 19) and in vivo mouse co-xenografts demonstrated that FL-FDC crosstalk favors tumor growth and, via the secretion of CCL2 and CSF-1, promotes monocyte recruitment, differentiation, and polarization towards an M2-like protumoral phenotype. Moreover, FL-M2 co-cultures displayed enhanced angiogenesis, dissemination, and immunosuppression. Analysis of the CSF-1/CSF-1R pathway uncovered that CSF-1 was significantly higher in serum from grade 3A FL patients, and that high CSF-1R expression in FL biopsies correlated with grade 3A, reduced overall survival and risk of transformation. Furthermore, CSF-1R inhibition with pexidartinib (PLX3397) preferentially affected M2-macrophage viability and polarization program disrupting FL-M2 positive crosstalk. In vivo CSF1-R inhibition caused M2 reduction and repolarization towards M1 macrophages and antitumor effect cooperating with anti-CD20 rituximab. In summary, these results support the role of macrophages in FL pathogenesis and indicate that CSF-1R may be a relevant prognostic factor and a novel therapeutic target cooperating with anti-CD20 immunotherapy.
Assuntos
Biomarcadores Tumorais/metabolismo , Regulação Neoplásica da Expressão Gênica , Linfoma Folicular/patologia , Macrófagos/patologia , Monócitos/patologia , Receptor de Fator Estimulador de Colônias de Macrófagos/metabolismo , Microambiente Tumoral , Aminopiridinas/farmacologia , Animais , Apoptose , Biomarcadores Tumorais/genética , Diferenciação Celular , Proliferação de Células , Humanos , Linfoma Folicular/tratamento farmacológico , Linfoma Folicular/metabolismo , Macrófagos/efeitos dos fármacos , Macrófagos/metabolismo , Camundongos , Monócitos/efeitos dos fármacos , Monócitos/metabolismo , Fosforilação , Pirróis/farmacologia , Receptor de Fator Estimulador de Colônias de Macrófagos/antagonistas & inibidores , Receptor de Fator Estimulador de Colônias de Macrófagos/genética , Células Tumorais Cultivadas , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
Follicular Lymphoma (FL), the most common indolent non-Hodgkin's B cell lymphoma, is a paradigm of the immune microenvironment's contribution to disease onset, progression, and heterogeneity. Over the last few years, state-of-the-art technologies, including whole-exome sequencing, single-cell RNA sequencing, and mass cytometry, have precisely dissected the specific cellular phenotypes present in the FL microenvironment network and their role in the disease. In this already complex picture, the presence of recurring mutations, including KMT2D, CREBBP, EZH2, and TNFRSF14, have a prominent contributory role, with some of them finely tuning this exquisite dependence of FL on its microenvironment. This precise characterization of the enemy (FL) and its allies (microenvironment) has paved the way for the development of novel therapies aimed at dismantling this contact network, weakening tumor cell support, and reactivating the host's immune response against the tumor. In this review, we will describe the main microenvironment actors, together with the current and future therapeutic approaches targeting them.
RESUMO
Despite idelalisib approval in relapsed follicular lymphoma (FL), a complete characterization of the immunomodulatory consequences of phosphatidylinositol 3-kinase δ (PI3Kδ) inhibition, biomarkers of response, and potential combinatorial therapies in FL remain to be established. Using ex vivo cocultures of FL patient biopsies and follicular dendritic cells (FDCs) to mimic the germinal center (n = 42), we uncovered that PI3Kδ inhibition interferes with FDC-induced genes related to angiogenesis, extracellular matrix formation, and transendothelial migration in a subset of FL samples, defining an 18-gene signature fingerprint of idelalisib sensitivity. A common hallmark of idelalisib found in all FL cases was its interference with the CD40/CD40L pathway and induced proliferation, together with the downregulation of proteins crucial for B-T-cell synapses, leading to an inefficient cross talk between FL cells and the supportive T-follicular helper cells (TFH). Moreover, idelalisib downmodulates the chemokine CCL22, hampering the recruitment of TFH and immunosupressive T-regulatory cells to the FL niche, leading to a less supportive and tolerogenic immune microenvironment. Finally, using BH3 profiling, we uncovered that FL-FDC and FL-macrophage cocultures augment tumor addiction to BCL-XL and MCL-1 or BFL-1, respectively, limiting the cytotoxic activity of the BCL-2 inhibitor venetoclax. Idelalisib restored FL dependence on BCL-2 and venetoclax activity. In summary, idelalisib exhibits a patient-dependent activity toward angiogenesis and lymphoma dissemination. In all FL cases, idelalisib exerts a general reshaping of the FL immune microenvironment and restores dependence on BCL-2, predisposing FL to cell death, providing a mechanistic rationale for investigating the combination of PI3Kδ inhibitors and venetoclax in clinical trials.
Assuntos
Antineoplásicos , Linfoma Folicular , Antineoplásicos/farmacologia , Antineoplásicos/uso terapêutico , Compostos Bicíclicos Heterocíclicos com Pontes/farmacologia , Compostos Bicíclicos Heterocíclicos com Pontes/uso terapêutico , Humanos , Linfoma Folicular/tratamento farmacológico , Sulfonamidas/farmacologia , Sulfonamidas/uso terapêutico , Microambiente TumoralRESUMO
CD38 is expressed in several types of non-Hodgkin lymphoma (NHL) and constitutes a promising target for antibody-based therapy. Daratumumab (Darzalex) is a first-in-class anti-CD38 antibody approved for the treatment of relapsed/refractory (R/R) multiple myeloma (MM). It has also demonstrated clinical activity in Waldenström macroglobulinaemia and amyloidosis. Here, we have evaluated the activity and mechanism of action of daratumumab in preclinical in vitro and in vivo models of mantle cell lymphoma (MCL), follicular lymphoma (FL) and diffuse large B-cell lymphoma (DLBCL), as monotherapy or in combination with standard chemo-immunotherapy. In vitro, daratumumab engages Fc-mediated cytotoxicity by antibody-dependent cell cytotoxicity and antibody-dependent cell phagocytosis in all lymphoma subtypes. In the presence of human serum, complement-dependent cell cytotoxicity was marginally engaged. We demonstrated by Selective Plane Illumination Microscopy that daratumumab fully penetrated a three-dimensional (3D) lymphoma organoid and decreased organoid volume. In vivo, daratumumab completely prevents tumor outgrowth in models of MCL and FL, and shows comparable activity to rituximab in a disseminated in vivo model of blastic MCL. Moreover, daratumumab improves overall survival (OS) in a mouse model of transformed CD20dim FL, where rituximab showed limited activity. Daratumumab potentiates the antitumor activity of CHOP and R-CHOP in MCL and FL xenografts. Furthermore, in a patient-derived DLBCL xenograft model, daratumumab anti-tumor activity was comparable to R-CHOP and the addition of daratumumab to either CHOP or R-CHOP led to full tumor regression. In summary, daratumumab constitutes a novel therapeutic opportunity in certain scenarios and these results warrant further clinical development.
Assuntos
Anticorpos Monoclonais/uso terapêutico , Linfoma não Hodgkin/terapia , Adulto , Linfócitos B , Humanos , Imunoterapia , RituximabRESUMO
In endometrioid endometrial carcinomas (EECs), microcystic, elongated, and fragmented (MELF) myoinvasion is associated with easily overlooked lymph node metastases; however, the role of immunohistochemistry in their detection and their clinical significance have not been addressed. We identified MELF in 43 of 101 (43%) myoinvasive EECs. Nodes were removed in 49 (49%), 25 with MELF and 24 without MELF. Metastases were initially reported in 3 of the former (12%) and 2 of the latter (8%). All negative nodes were reviewed, and cytokeratin immunohistochemistry was performed. Three metastases were identified in the MELF group but none in the EECs without MELF. By immunohistochemistry, metastatic nodal isolated tumor cells (ITCs) were found in 6 of the remaining 19 MELF-positive cases. In contrast, lymph node metastases were detected in only 2 of the 22 EECs without MELF. MELF-positive cases had more lymph node metastases (P=.03) than myoinvasive EECs without MELF. At follow-up, all 6 patients with grade 1-2 EECs and nodal ITCs/micrometastases were alive (5 no evidence of disease and 1 with perineal disease). In contrast, 3 of 4 patients with grade 3 EECs and nodal ITCs/micrometastases died of disease, and the other patient was alive with tumor. In MELF, the frequency of ITCs/micrometastases in apparently negative lymph nodes is high. In patients with grade 1-2 EEC who had not received chemotherapy, the presence of nodal ITCs/micrometastases did not affect survival. In contrast, in high-grade tumors, ITCs/micrometastases were associated with unfavorable prognosis. Immunohistochemistry should be done in MELF-positive cases to detect occult lymph node metastases, especially in high-grade tumors.
Assuntos
Biomarcadores Tumorais/análise , Carcinoma Endometrioide/química , Carcinoma Endometrioide/secundário , Neoplasias do Endométrio/química , Neoplasias do Endométrio/patologia , Imuno-Histoquímica , Linfonodos/química , Idoso , Idoso de 80 Anos ou mais , Carcinoma Endometrioide/mortalidade , Carcinoma Endometrioide/terapia , Neoplasias do Endométrio/mortalidade , Neoplasias do Endométrio/terapia , Feminino , Humanos , Linfonodos/patologia , Metástase Linfática , Pessoa de Meia-Idade , Miométrio/química , Miométrio/patologia , Gradação de Tumores , Invasividade Neoplásica , Micrometástase de Neoplasia , Valor Preditivo dos Testes , Estudos Retrospectivos , Fatores de Risco , Resultado do TratamentoRESUMO
Carcinogenesis is a multistep process in which cancer cells and tumor stroma cells play important roles. T lymphocytes are immune constituents of tumor stroma and play a crucial function in anti-tumor response. By immunohistochemistry and flow cytometry, we studied T cytotoxic (CTLs) and T helper lymphocyte distribution and percentage in the tumor microenvironment and peripheral blood from 35 patients with endometrioid endometrial carcinomas (EEC). We also studied 23 healthy donors' blood samples as a control group. Tumor and non-tumoral endometrium samples were obtained. Immunohistochemistry revealed a high number of CTLs and T helper lymphocytes in the tumor stroma of myoinvasive EECs. T lymphocytes were mostly located in the invasive front. By flow cytometry, the percentages of CTLs and T helper lymphocytes were significantly higher in the tumor compared with the non-neoplastic endometrium (P = .0492 and P = .002). The mean fluorescence intensity of CD8 staining was lower in the tumor compared to the non-neoplastic endometrium (P = .001). There was also reduction of the mean fluorescence intensity of CD8 staining on peripheral blood from patients with grade 3 EECs compare to the peripheral blood from healthy donors (P = .0093). No alterations in the expression of granzymes A and B were found in the CTLs from the EEC cases. Finally, in a proteome profiler cytokine array we found that the growth differentiation factor 15 (GDF15) increased in blood in parallel to the tumor grade. EECs are capable of down-regulating CD8 expression of CTLs. Most likely, this effect is mediated by a soluble molecule present in plasma and is not a result of anergy or exhaustion state.
Assuntos
Biomarcadores Tumorais/análise , Antígenos CD8/análise , Carcinoma Endometrioide/imunologia , Neoplasias do Endométrio/imunologia , Linfócitos do Interstício Tumoral/imunologia , Linfócitos T Citotóxicos/imunologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Biomarcadores Tumorais/sangue , Carcinoma Endometrioide/sangue , Carcinoma Endometrioide/patologia , Citocinas/sangue , Regulação para Baixo , Neoplasias do Endométrio/sangue , Neoplasias do Endométrio/patologia , Feminino , Fator 15 de Diferenciação de Crescimento/sangue , Humanos , Linfócitos do Interstício Tumoral/patologia , Pessoa de Meia-Idade , Gradação de Tumores , Linfócitos T Citotóxicos/patologia , Microambiente TumoralRESUMO
LPS induces the expression of NO synthase 2 (nos2) in macrophages. The expression of this molecule is one of the hallmarks of classical activation. In this paper, we describe that trichostatin A (TSA), which inhibits deacetylase activity, blocks LPS-dependent nos2 expression. TSA specifically inhibits LPS-dependent genes of secondary response, which require new protein synthesis for their induction but not those belonging to the primary response, which do not depend on this process. Deacetylase activity acts at the transcriptional level because RNA polymerase II was not bound after LPS stimulus when we added TSA. A link between the global acetylation caused by HDAC inhibitor and gene promoter recruitment of CDK8 was found. This Mediator complex subunit associates with Med 12, Med13, and cyclin C to form a submodule that is a transcriptional negative regulator. We also found that TSA reduces C/EBPß phosphorylation without affecting its binding to DNA. Taken together, these results shed light on the molecular mechanisms involved in the transcriptional regulation of LPS-treated macrophages and on how TSA targets critical LPS-induced genes, such as nos2 and tnf-α, in inflammatory macrophage response.
Assuntos
Proteína beta Intensificadora de Ligação a CCAAT/metabolismo , Regulação da Expressão Gênica , Histona Desacetilases/metabolismo , Lipopolissacarídeos/imunologia , Macrófagos/imunologia , Macrófagos/metabolismo , Animais , Quinase 8 Dependente de Ciclina/metabolismo , Regulação da Expressão Gênica/efeitos dos fármacos , Ordem dos Genes , Inativação Gênica , Histona Desacetilase 1/genética , Histona Desacetilase 1/metabolismo , Inibidores de Histona Desacetilases/farmacologia , Histona Desacetilases/genética , Ácidos Hidroxâmicos/farmacologia , Camundongos , NF-kappa B/metabolismo , Óxido Nítrico Sintase Tipo II/genética , Óxido Nítrico Sintase Tipo II/metabolismo , Fosforilação/efeitos dos fármacos , Regiões Promotoras Genéticas , Ligação Proteica , RNA Polimerase II/metabolismo , Transdução de Sinais/efeitos dos fármacos , Proteína de Ligação a TATA-Box/metabolismo , Iniciação da Transcrição Genética , Transcrição Gênica/efeitos dos fármacos , Proteínas Quinases p38 Ativadas por Mitógeno/metabolismoRESUMO
The amount of arginine available at inflammatory loci is a limiting factor for the growth of several cells of the immune system. IL-4-induced activation of macrophages produced arginase-1, which converts arginine into ornithine, a precursor of polyamines and proline. Trichostatin A (TSA), a pan-inhibitor of histone deacetylases (HDACs), inhibited IL-4-induced arginase-1 expression. TSA showed promoter-specific effects on the IL-4-responsive genes. While TSA inhibited the expression of arginase-1, fizz1, and mrc1, other genes, such as ym,1 mgl1, and mgl2, were not affected. The inhibition of arginase-1 occurred at the transcriptional level with the inhibition of polymerase II binding to the promoter. IL-4 induced STAT6 phosphorylation and binding to DNA. These activities were not affected by TSA treatment. However, TSA inhibited C/EBPß DNA binding. This inhibitor induced acetylation on lysine residues 215-216, which are critical for DNA binding. Finally, using macrophages from STAT6 KO mice we showed that STAT6 is required for the DNA binding of C/EBPß. These results demonstrate that the acetylation/deacetylation balance strongly influences the expression of arginase-1, a gene of alternative activation of macrophages. These findings also provide a molecular mechanism to explain the control of gene expression through deacetylase activity.
Assuntos
Arginase/biossíntese , Proteína beta Intensificadora de Ligação a CCAAT/metabolismo , Inibidores de Histona Desacetilases/farmacologia , Interleucina-4/farmacologia , Macrófagos/imunologia , Acetilação , Animais , Arginase/genética , Arginase/imunologia , Proteína beta Intensificadora de Ligação a CCAAT/imunologia , Ácidos Hidroxâmicos/farmacologia , Ativação de Macrófagos/efeitos dos fármacos , Ativação de Macrófagos/imunologia , Macrófagos/efeitos dos fármacos , Macrófagos/enzimologia , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Knockout , Fosforilação , RNA/química , RNA/genética , Reação em Cadeia da Polimerase em Tempo Real , Fator de Transcrição STAT6/imunologia , Estatísticas não ParamétricasRESUMO
After interaction with its receptor, GM-CSF induces phosphorylation of the beta-chain in two distinct domains in macrophages. One induces activation of mitogen-activated protein kinases and the PI3K/Akt pathway, and the other induces JAK2-STAT5. In this study we describe how trichostatin A (TSA), which inhibits deacetylase activity, blocks JAK2-STAT5-dependent gene expression but not the expression of genes that depend on the signal transduction induced by the other domain of the receptor. TSA treatment inhibited the GM-CSF-dependent proliferation of macrophages by interfering with c-myc and cyclin D1 expression. However, M-CSF-dependent proliferation, which requires ERK1/2, was unaffected. Protection from apoptosis, which involves Akt phosphorylation and p21(waf-1) expression, was not modified by TSA. GM-CSF-dependent expression of MHC class II molecules was inhibited because CIITA was not induced. The generation of dendritic cells was also impaired by TSA treatment because of the inhibition of IRF4, IRF2, and RelB expression. TSA mediates its effects by preventing the recruitment of RNA polymerase II to the promoter of STAT5 target genes and by inhibiting their expression. However, this drug did not affect STAT5A or STAT5B phosphorylation or DNA binding. These results in GM-CSF-treated macrophages reveal a relationship between histone deacetylase complexes and STAT5 in the regulation of gene expression.
Assuntos
Diferenciação Celular/imunologia , Células Dendríticas/imunologia , Regulação da Expressão Gênica/imunologia , Fator Estimulador de Colônias de Granulócitos e Macrófagos/imunologia , Histona Desacetilases/imunologia , Macrófagos/imunologia , Fator de Transcrição STAT5/imunologia , Animais , Apoptose/efeitos dos fármacos , Apoptose/imunologia , Diferenciação Celular/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Ciclina D , Inibidor de Quinase Dependente de Ciclina p21/imunologia , Inibidor de Quinase Dependente de Ciclina p21/metabolismo , Ciclinas/imunologia , Ciclinas/metabolismo , Células Dendríticas/citologia , Células Dendríticas/metabolismo , Inibidores Enzimáticos/farmacologia , Regulação da Expressão Gênica/efeitos dos fármacos , Fator Estimulador de Colônias de Granulócitos e Macrófagos/metabolismo , Antígenos de Histocompatibilidade Classe II/imunologia , Antígenos de Histocompatibilidade Classe II/metabolismo , Inibidores de Histona Desacetilases , Histona Desacetilases/metabolismo , Ácidos Hidroxâmicos/farmacologia , Fator Regulador 2 de Interferon/imunologia , Fator Regulador 2 de Interferon/metabolismo , Fatores Reguladores de Interferon/imunologia , Fatores Reguladores de Interferon/metabolismo , Janus Quinase 2/genética , Janus Quinase 2/imunologia , Macrófagos/citologia , Macrófagos/metabolismo , Camundongos , Camundongos Endogâmicos BALB C , Proteína Quinase 1 Ativada por Mitógeno/imunologia , Proteína Quinase 1 Ativada por Mitógeno/metabolismo , Proteína Quinase 3 Ativada por Mitógeno/imunologia , Proteína Quinase 3 Ativada por Mitógeno/metabolismo , Proteínas Nucleares/imunologia , Proteínas Nucleares/metabolismo , Fosfatidilinositol 3-Quinases/imunologia , Fosfatidilinositol 3-Quinases/metabolismo , Fosforilação/efeitos dos fármacos , Regiões Promotoras Genéticas/imunologia , Proteínas Proto-Oncogênicas c-akt/imunologia , Proteínas Proto-Oncogênicas c-akt/metabolismo , Proteínas Proto-Oncogênicas c-myc/imunologia , Proteínas Proto-Oncogênicas c-myc/metabolismo , RNA Polimerase II/imunologia , RNA Polimerase II/metabolismo , Receptores de Fator Estimulador das Colônias de Granulócitos e Macrófagos/imunologia , Receptores de Fator Estimulador das Colônias de Granulócitos e Macrófagos/metabolismo , Fator de Transcrição STAT5/metabolismo , Transdução de Sinais/efeitos dos fármacosRESUMO
Arginine is processed by macrophages in response to the cytokines to which these cells are exposed. Th1-type cytokines induce NO synthase 2, which metabolizes arginine into nitrites, while the Th2-type cytokines produce arginase, which converts arginine into polyamines and proline. Activation of bone marrow-derived macrophages by these two types of cytokines increases L-arginine transport only through the y(+) system. Analysis of the expression of the genes involved in this system showed that Slc7A1, encoding cationic amino acid transporters (CAT)1, is constitutively expressed and is not modified by activating agents, while Slc7A2, encoding CAT2, is induced during both classical and alternative activation. Macrophages from Slc7A2 knockout mice showed a decrease in L-arginine transport in response to the two kinds of cytokines. However, while NO synthase 2 and arginase expression were unmodified in these cells, the catabolism of arginine was impaired by both pathways, producing smaller amounts of nitrites and also of polyamines and proline. In addition, the induction of Slc7A2 expression was independent of the arginine available and of the enzymes that metabolize it. In conclusion, the increased arginine transport mediated by activators is strongly regulated by CAT2 expression, which could limit the function of macrophages.