Supplementation of l‐arginine boosts the therapeutic efficacy of anticancer chemoimmunotherapy

Myeloid‐derived suppressor cells (MDSCs) play a crucial role in immunosuppression in tumor‐bearing hosts. MDSCs express arginase‐I and indoleamine 2,3‐dioxygenase; they suppress T‐cell function by reducing the levels of l ‐arginine and l ‐tryptophan, respectively. We examined the anticancer effects of supplementation of these amino acids in CT26 colon carcinoma‐bearing mice. Oral supplementation of l ‐arginine or l ‐tryptophan (30 mg/mouse) did not affect tumor growth, whereas oral supplementation of d ‐arginine was lethal. Supplementation of l ‐arginine showed a tendency to augment the efficacy of cyclophosphamide (CP). CP reduced the proportions of granulocytic MDSCs and increased the proportions of monocytic MDSCs in the spleen and tumor tissues of CT26‐bearing mice. l ‐Arginine supplementation alone did not affect the MDSC subsets. CP treatment tended to reduce the plasma levels of l ‐arginine in CT26‐bearing mice and significantly increased the number of tumor‐infiltrating CD8⁺ T cells. In addition, l ‐arginine supplementation significantly increased the proportions of tumor peptide‐specific CD8⁺ T cells in draining lymph nodes. Importantly, additional supplementation of l ‐arginine significantly increased the number of cured mice that were treated with CP and anti‐PD‐1 antibody. Totally, l ‐arginine supplementation shows promise for boosting the therapeutic efficacy of chemoimmunotherapy.     

Starvation in cancer cells: circulating arginine is good for cancer but bad for patients

Introduction: Currently, basic understanding of heterogeneity and complexity of tumors is depicted at molecular, cellular, genetic, epigenetic and metabolic adaptations levels.

Areas covered: There are appreciable numbers of views to pinpoint signaling axis that support metabolic adaptations of cancer cells in response to environmental pressures including nutritional factors and drug treatments. Specifically, nutritional deprivation and autophagy in certain types of cancer are linked to the abilities of cancer cells to use arginine in an auxotrophic or prototrophic manner.

Expert opinion: Hence, this paper highlights the current scope of arginine- and autophagy-centered metabolic adaptations across tumor types and possible avenues to bring tumors towards cytotoxic or cytostatic death.     

丝氨酸/精氨酸富有剪接因子1、核因子κB在前列腺癌中的表达及与患者临床特征的关系

目的探讨前列腺癌组织中丝氨酸/精氨酸富有剪接因子1(SRSF1)、核因子κB(NF-κB)的表达情况及与患者临床特征的关系。方法选取前列腺癌患者和前列腺良性增生患者,各70例,取前列腺癌组织和前列腺良性增生组织。免疫组化法检测前列腺癌组织和前列腺良性增生组织SRSF1、NF-κB蛋白的阳性表达率,并分析不同临床特征前列腺癌患者前列腺癌组织中SRSF1、NF-κB蛋白的表达情况。结果前列腺癌组织中SRSF1、NF-κB蛋白的阳性表达率均高于前列腺良性增生组织,差异均有统计学意义(P﹤0.05)。不同前列腺特异性抗原(PSA)水平前列腺癌患者前列腺癌组织中SRSF1蛋白的阳性表达率比较,差异无统计学意义(P﹥0.05);不同TNM分期、淋巴结转移情况、Gleason评分前列腺癌患者前列腺癌组织中SRSF1蛋白的阳性表达率比较,差异均有统计学意义(P﹤0.05)。不同PSA水平、Gleason评分前列腺癌患者前列腺癌组织中NF-κB蛋白的阳性表达率比较,差异均无统计学意义(P﹥0.05);不同TNM分期、淋巴结转移情况前列腺癌患者前列腺癌组织中NF-κB蛋白的阳性表达率比较,差异均有统计学意义(P﹤0.05)。结论前列腺癌组织中的SRSF1、NF-κB蛋白表达水平和阳性表达率均较高,SRSF1蛋白的表达可能与TNM分期、淋巴结转移情况和Gleason评分,NF-κB蛋白的表达可能与TNM分期和淋巴结转移情况有关。     

The changes in,and relationship between,plasma nitric oxide and corticotropin‐releasing hormone in patients with major depressive disorder

There is strong evidence of roles of the hypothalamus‐pituitary‐adrenal axis and nitric oxide (NO) synthase‐NO system in depression, but the relationship between them is unknown. The aim of this study, therefore, was to elucidate whether there is any correlation between NO and corticotropin‐releasing hormone (CRH) in major depressive disorder (MDD) patients. In 16 outpatients with MDD and 18 healthy controls, the plasma amino acids citrulline (Cit) and arginine (Arg) were determined by high‐performance liquid chromatography, and CRH levels was measured by radioimmunoassay. The Cit/Arg ratio was calculated as an index of NO synthesis. Correlations between NO and CRH were examined with the Spearman test. Before treatment, no significant correlation was observed between the plasma NO level and CRH levels in MDD patients. The plasma NO levels were significantly higher in MDD patients. A significant correlation was found between NO levels and Hamilton Depression Rating Scale (HAMD) scores in MDD patients. The plasma CRH levels were significantly higher in MDD patients than in controls. After monotherapy for 2 months, the NO levels had dramatically declined but were also higher than those in the controls. This study is the first report of the absence of a significant correlation between plasma NO and CRH levels, although both levels are elevated in MDD patients. Furthermore, the strong links between the plasma NO levels and the HAMD scores, as well as the increased NO reduction after remission, suggest that NO plays a key role in depression and may be an indicator of therapeutic success.     

Arginase and α‐smooth muscle actin induction after hyperoxic exposure in a mouse model of bronchopulmonary dysplasia

The L‐arginine/NO pathway is an important regulator of pulmonary hypertension, the leading cause of mortality in patients with the chronic lung disease of prematurity, bronchopulmonary dysplasia. L‐arginine can be metabolized by NO synthase (NOS) to form L‐citrulline and NO, a potent vasodilator. Alternatively, L‐arginine can be metabolized by arginase to form urea and L‐ornithine, a precursor to collagen and proline formation important in vascular remodelling. In the current study, we hypothesized that C3H/HeN mice exposed to prolonged hyperoxia would have increased arginase expression and pulmonary vascular wall cell proliferation. C3H/HeN mice were exposed to 14 days of 85% O₂ or room air and lung homogenates analyzed by western blot for protein levels of arginase I, arginase II, endothelial NOS (eNOS), ornithine decarboxylase (ODC), ornithine aminotransferase (OAT), and α‐smooth muscle actin (α‐SMA). Hyperoxia did not change arginase I or eNOS protein levels. However, arginase II protein levels were 15‐fold greater after hyperoxia exposure than in lungs exposed to room air. Greater protein levels of ODC and OAT were found in lungs following hyperoxic exposure than in room air animals. α‐SMA protein levels were found to be 7‐fold greater in the hyperoxia exposed lungs than in room air lungs. In the hyperoxia exposed lungs there was evidence of greater pulmonary vascular wall cell proliferation by α‐SMA immunohistochemistry than in room air lungs. Taken together, these data are consistent with a more proliferative vascular phenotype, and may explain the propensity of patients with bronchopulmonary dysplasia to develop pulmonary hypertension.     

A novel Tc‐99m and fluorescence‐labeled arginine‐arginine‐leucine‐containing peptide as a multimodal tumor imaging agent in a murine tumor model

We developed a Tc‐99m and TAMRA‐labeled peptide, Tc‐99m arginine‐arginine‐leucine (RRL) peptide (TAMRA‐GHEG‐ECG‐RRL), to target tumor cells and evaluated the diagnostic performance of Tc‐99m TAMRA‐GHEG‐ECG‐RRL as a dual‐modality imaging agent for tumor in a murine model. TAMRA‐GHEG‐ECG‐RRL was synthesized using Fmoc solid‐phase peptide synthesis. Binding affinity and in vitro cellular uptake studies were performed. Gamma camera imaging, biodistribution, and ex vivo imaging studies were performed in murine models with PC‐3 tumors. Tumor tissue slides were prepared and analyzed with immunohistochemistry using confocal microscopy. After radiolabeling procedures with Tc‐99m, Tc‐99m TAMRA‐GHEG‐ECG‐RRL complexes were prepared in high yield (>96%). The K_d of Tc‐99m TAMRA‐GHEG‐ECG‐RRL determined by saturation binding was 41.7 ± 7.8 nM. Confocal microscopy images of PC‐3 cells incubated with TAMRA‐GHEG‐ECG‐RRL showed strong fluorescence in the cytoplasm. Gamma camera imaging revealed substantial uptake of Tc‐99m TAMRA‐GHEG‐ECG‐RRL in tumors. Tumor uptake was effectively blocked by the coinjection of an excess concentration of RRL. Specific uptake of Tc‐99m TAMRA‐GHEG‐ECG‐RRL was confirmed by biodistribution, ex vivo imaging, and immunohistochemistry stain studies. In conclusion, in vivo and in vitro studies revealed substantial uptake of Tc‐99m TAMRA‐GHEG‐ECG‐RRL in tumors. Tc‐99m TAMRA‐GHEG‐ECG‐RRL has potential as a dual‐modality tumor imaging agent.     

Ammonium accumulation and chemokine decrease in culture media of Gcdh−/− 3D reaggregated brain cell cultures

Glutaric Aciduria type I (GA-I) is caused by mutations in the GCDH gene. Its deficiency results in accumulation of the key metabolites glutaric acid (GA) and 3-hydroxyglutaric acid (3-OHGA) in body tissues and fluids. Present knowledge on the neuropathogenesis of GA-I suggests that GA and 3-OHGA have toxic properties on the developing brain.We analyzed morphological and biochemical features of 3D brain cell aggregates issued from Gcdh^?/? mice at two different developmental stages, day-in-vitro (DIV) 8 and 14, corresponding to the neonatal period and early childhood. We also induced a metabolic stress by exposing the aggregates to 10 mM l-lysine (Lys).Significant amounts of GA and 3-OHGA were detected in Gcdh^?/? aggregates and their culture media. Ammonium was significantly increased in culture media of Gcdh^?/? aggregates at the early developmental stage. Concentrations of GA, 3-OHGA and ammonium increased significantly after exposure to Lys. Gcdh^?/? aggregates manifested morphological alterations of all brain cell types at DIV 8 while at DIV 14 they were only visible after exposure to Lys. Several chemokine levels were significantly decreased in culture media of Gcdh^?/? aggregates at DIV 14 and after exposure to Lys at DIV 8.This new in vitro model for brain damage in GA-I mimics well in vivo conditions. As seen previously in WT aggregates exposed to 3-OHGA, we confirmed a significant ammonium production by immature Gcdh^?/? brain cells. We described for the first time a decrease of chemokines in Gcdh^?/? culture media which might contribute to brain cell injury in GA-I.     

Isolation and characterization of aminopeptidase from Capnocytophaga granulosa ATCC 51502

There is evidence that enzymes from the genus Capnocytophaga play a role in dental calculus formation. Although most of the species in the genus produce aminopeptidases, there is a paucity of data on the purification and characterization of the enzyme, except in the case of Capnocytophaga gingivalis. The aim of this study was to purify aminopeptidase from culture supernatant of Capnocytophaga granulosa ATCC 51502, a new species of the genus. Purification was performed using ammonium sulfate fractionation and two chromatographic steps. The aminopeptidase was purified 158,433-fold with a yield of 12.0%. The enzyme appeared to be a trimer with a molecular mass of 270 kDa. The optimal pH of the aminopeptidase was 6.5 and its activity was completely inhibited by incubation at 50 degrees C for 10 min. The enzyme showed maximum specificity for basic amino acids (Arg and Lys) and also hydrolyzed noncharged amino acids (Met, Leu and Ala). Ca(2+), Zn(2+) and Fe(3+) activated the enzyme, while EDTA, Ag(+), Hg(+) and Cu(2+) inhibited it. These results suggest that aminopeptidase of C. granulosa is different from that of C. gingivalis but similar to aminopeptidase B.