Macrophages are a heterogeneous group of phagocytes that play critical roles in inflammation, infection and tumor growth. Macrophages respond to different environmental factors and are thereby polarized into specialized functional subsets. Although hypoxia is an important environmental factor, its impact on human macrophage polarization and subsequent modification of the inflammatory microenvironment have not been fully established. The present study aimed to elucidate the effect of hypoxia exposure on the ability of human macrophages to polarize into the classically activated (pro-inflammatory) M1, and the alternatively activated (anti-inflammatory) M2 phenotypes. The effect on the inflammatory microenvironment and the subsequent modification of A549 lung carcinoma cells was also investigated. The presented data show that hypoxia promoted macrophage polarization towards the M2 phenotype, and modified the inflammatory microenvironment by decreasing the release of proinflammatory cytokines. Modification of the microenvironment by proinflammatory M1 macrophages under hypoxia reversed the inhibition of malignant behaviors within the proinflammatory microenvironment. Furthermore, it was identified p38 signaling (a major contributor to the response to reactive oxygen species generated by hypoxic stress), but not hypoxia-induced factor, as a key regulator of macrophages under hypoxia. Taken together, the data suggest that hypoxia affects the inflammatory microenvironment by modifying the polarization of macrophages, and thus, reversing the inhibitory effects of a proinflammatory microenvironment on the malignant behaviors of several types of cancer cell.
First-line systemic therapeutic options for advanced esophageal squamous cell carcinoma (ESCC) are limited. In this multicenter, double-blind phase 3 trial, a total of 551 patients with previously untreated, locally advanced or metastatic ESCC and PD-L1 combined positive score of ≥1 were randomized (2:1) to receive serplulimab (an anti-PD-1 antibody; 3 mg/kg) or placebo (on day 1), plus cisplatin (50 mg/m2) (on day 1) and continuous infusion of 5-fluorouracil (1,200 mg/m2) (on days 1 and 2), once every 2 weeks. The study met the primary endpoints. At the prespecified final analysis of progression-free survival (PFS) assessed by the blinded independent radiological review committee, serplulimab plus chemotherapy significantly improved PFS compared with placebo plus chemotherapy (median PFS of 5.8 months and 5.3 months, respectively; hazard ratio, 0.60; 95% confidence interval, 0.48–0.75; P < 0.0001). At the prespecified interim analysis of overall survival (OS), serplulimab plus chemotherapy also significantly prolonged OS compared with placebo plus chemotherapy (median OS of 15.3 months and 11.8 months, respectively; hazard ratio, 0.68; 95% confidence interval, 0.53–0.87; P = 0.0020). Grade 3 or higher treatment-related adverse events occurred in 201 (53%) and 81 (48%) patients in the serplulimab plus chemotherapy group and the placebo plus chemotherapy group, respectively. Serplulimab plus chemotherapy administered every 2 weeks significantly improved PFS and OS in patients with previously untreated, PD-L1-positive advanced ESCC, with a manageable safety profile. This study is registered with ClinicalTrials.gov (NCT03958890).
Glycine betaine (betaine) is widely distributed in nature and can be found in many microorganisms, including bacteria, archaea, and fungi. Due to its particular functions, many microorganisms utilize betaine as a functional chemical and have evolved different metabolic pathways for the biosynthesis and catabolism of betaine. As in animals and plants, the principle role of betaine is to protect microbial cells against drought, osmotic stress, and temperature stress. In addition, the role of betaine in methyl group metabolism has been observed in a variety of microorganisms. Recent studies have shown that betaine supplementation can improve the performance of microbial strains used for the fermentation of lactate, ethanol, lysine, pyruvate, and vitamin B12, during which betaine can act as stress protectant or methyl donor for the biosynthesis of structurally complex compounds. In this review, we summarize the transport, synthesis, catabolism, and functions of betaine in microorganisms and discuss potential engineering strategies that employ betaine as a methyl donor for the biosynthesis of complex secondary metabolites such as a variety of vitamins, coenzymes, and antibiotics. In conclusion, the biocompatibility, C/N ratio, abundance, and comprehensive metabolic information of betaine collectively indicate that this molecule has great potential for broad applications in microbial biotechnology.
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