Bile acids modified by the intestinal microbiota promote colorectal cancer growth by suppressing CD8+ T cell effector functions.

Concentrations of the secondary bile acid, deoxycholic acid (DCA), are aberrantly elevated in colorectal cancer (CRC) patients, but the consequences remain poorly understood. Here, we screened a library of gut microbiota-derived metabolites and identified DCA as a negative regulator for CD8+ T cell effector function. Mechanistically, DCA suppressed CD8+ T cell responses by targeting plasma membrane Ca2+ ATPase (PMCA) to inhibit Ca2+-nuclear factor of activated T cells (NFAT)2 signaling. In CRC patients, CD8+ T cell effector function negatively correlated with both DCA concentration and expression of a bacterial DCA biosynthetic gene. Bacteria harboring DCA biosynthetic genes suppressed CD8+ T cells effector function and promoted tumor growth in mice. This effect was abolished by disrupting bile acid metabolism via bile acid chelation, genetic ablation of bacterial DCA biosynthetic pathway, or specific bacteriophage. Our study demonstrated causation between microbial DCA metabolism and anti-tumor CD8+ T cell response in CRC, suggesting potential directions for anti-tumor therapy.

Gut microbial metabolite facilitates colorectal cancer development via ferroptosis inhibition.

The gut microbiota play a pivotal role in human health. Emerging evidence indicates that gut microbes participate in the progression of tumorigenesis through the generation of carcinogenic metabolites. However, the underlying molecular mechanism is largely unknown. In the present study we show that a tryptophan metabolite derived from Peptostreptococcus anaerobius, trans-3-indoleacrylic acid (IDA), facilitates colorectal carcinogenesis. Mechanistically, IDA acts as an endogenous ligand of an aryl hydrocarbon receptor (AHR) to transcriptionally upregulate the expression of ALDH1A3 (aldehyde dehydrogenase 1 family member A3), which utilizes retinal as a substrate to generate NADH, essential for ferroptosis-suppressor protein 1(FSP1)-mediated synthesis of reduced coenzyme Q10. Loss of AHR or ALDH1A3 largely abrogates IDA-promoted tumour development both in vitro and in vivo. It is interesting that P. anaerobius is significantly enriched in patients with colorectal cancer (CRC). IDA treatment or implantation of P. anaerobius promotes CRC progression in both xenograft model and ApcMin/+ mice. Together, our findings demonstrate that targeting the IDA-AHR-ALDH1A3 axis should be promising for ferroptosis-related CRC treatment.

A2AR limits IL-15-induced generation of CD39+ NK cells with high cytotoxicity.

CD39-mediated inhibition of natural killer (NK) cell activity has been demonstrated, but the characteristics of CD39+ NK cells in humans are not known. We investigated the characteristics of human circulating CD39+ NK cells. In healthy donors, the proportion of circulating CD39+ NK cells in total NK cells was relatively low compared with that of CD39- NK cells. Nonetheless, a higher proportion of CD39+ NK cells expressed CD107a. Similarly, a higher proportion of CD39+ NK cells expressed CD107a in patients with hepatitis B virus or patients with hepatocellular carcinoma. Stimulation with NK-sensitive K562 cells or interleukin (IL)-12/IL-18 activated CD39+ NK cells to express higher levels of CD107a, IFN-γ and TNF-α, relative to CD39- NK cells. Importantly, IL-15 induced the generation of CD39+ NK cells. In contrast, A2A adenosine receptor (A2AR) ligation suppressed the generation of CD39+ NK cells by inhibiting IL-15 signaling. These data for the first time demonstrated that A2AR counteracts IL-15-induced generation of human CD39+ NK cells, which have a stronger cytotoxicity than CD39- NK cells. IL-15-induced human CD39+ NK cells might be better choice for immunotherapy based on adoptive transfer of NK cells.

RTEF-1 Inhibits Vascular Smooth Muscle Cell Calcification through Regulating Wnt/ß-Catenin Signaling Pathway.

Vascular calcification (VC) is highly prevailing in cardiovascular disease, diabetes mellitus, and chronic kidney disease and, when present, is associated with cardiovascular events and mortality. The osteogenic differentiation of vascular smooth muscle cells (VSMCs) is regarded as the foundation for mediating VC. Related transcriptional enhancer factor (RTEF-1), also named as transcriptional enhanced associate domain (TEAD) 4 or transcriptional enhancer factor-3 (TEF-3), is a nuclear transcriptional factor with a potent effect on cardiovascular diseases, apart from its oncogenic role in the canonical Hippo pathway. However, the role and mechanism of RTEF-1 in VC, particularly in calcification of VSMCs, are poorly understood. Our results showed that RTEF-1 was reduced in calcified VSMCs. RTEF-1 significantly ameliorated ß-glycerophosphate (ß-GP)-induced VSMCs calcification, as detected by alizarin red staining and calcium content assay. Also, RTEF-1 reduced alkaline phosphatase (ALP) activity and decreased expressions of osteoblast markers such as Osteocalcin and Runt-related transcription factor-2 (Runx2), but increased expression of contractile protein, including SM α-actin (α-SMA). Additionally, RTEF-1 inhibited ß-GP-activated Wnt/ß-catenin pathway which plays a critical role in calcification and osteogenic differentiation of VSMCs. Specifically, RTEF-1 reduced the levels of Wnt3a, p-ß-catenin (Ser675), glycogen synthase kinase-3ß (GSK-3ß), and p-GSK-3ß (Ser9), but increased the levels of p-ß-catenin (Ser33/37). Also, RTEF-1 increased the ratio of p-ß-catenin (Ser33/37) to ß-catenin proteins and decreased the ratio of p-GSK-3ß (Ser9) to GSK-3ß protein. LiCl, a Wnt/ß-catenin signaling activator, was observed to reverse the protective effect of RTEF-1 overexpression on VSMCs calcification induced by ß-GP. Accordingly, Dickkopf-1 (Dkk1), a Wnt antagonist, attenuated the role of RTEF-1 deficiency in ß-GP-induced VSMCs calcification. Taken together, we concluded that RTEF-1 ameliorated ß-GP-induced calcification and osteoblastic differentiation of VSMCs by inhibiting Wnt/ß-catenin signaling pathway.

Metabolism of Natural Killer Cells and Other Innate Lymphoid Cells.

Natural killer (NK) cells are the host's first line of defense against tumors and viral infections without prior sensitization. It is increasingly accepted that NK cells belong to the innate lymphoid cell (ILC) family. Other ILCs, comprising ILC1s, ILC2s, ILC3s and lymphoid tissue inducer (LTi) cells, are largely non-cytotoxic, tissue-resident cells, which function to protect local microenvironments against tissue insults and maintain homeostasis. Recently, evidence has accumulated that metabolism supports many aspects of the biology of NK cells and other ILCs, and that metabolic reprogramming regulates their development and function. Here, we outline the current understanding of ILC metabolism, and describe how metabolic processes are affected, and how metabolic defects are coupled to dysfunction of ILCs, in disease settings. Furthermore, we summarize the current and potential directions for immunotherapy involving targeting of ILC metabolism. Finally, we discuss the open questions in the rapidly expanding field of ILC metabolism.

Immunogenic chemotherapy effectively inhibits KRAS-Driven lung cancer.

Immunogenic chemotherapy has been shown to be effective against several cancer types. Here, we identified trametinib as an inducer of immunogenic cell death (ICD), and found that it exerts beneficial antitumor effects if used in combination with interleukin (IL)-12 in a Kras-mutant mouse model of spontaneous lung cancer. Tumor cells treated with trametinib showed the hallmarks of ICD, including cell-surface expression of calreticulin, release of high mobility group box 1 (HMGB1) from the nucleus, and activation of dendritic cells. Tumor-bearing mice treated with both trametinib and IL-12 showed increased infiltration and proliferation of T cells within the tumor, as well as increased effector function of NK cells and T cells, indicating that this therapeutic combination can improve the quality of the immune response. Taken together, our results provide a potential new therapeutic regimen for the treatment of KRAS-mutant lung adenocarcinomas.

Low-Dose Gemcitabine Treatment Enhances Immunogenicity and Natural Killer Cell-Driven Tumor Immunity in Lung Cancer.

Gemcitabine has been used as first-line chemotherapy against lung cancer, but many patients experience cancer recurrence. Activation of anti-tumor immunity in vivo has become an important way to prevent recurrence. Anti-tumor immune responses are often dependent upon the immunogenicity of tumors. In our study, we observed that low-dose gemcitabine treatment enhanced the immunogenicity of lung cancer by increasing the exposure of calreticulin, high mobility group box 1, and upregulating expression of NKG2D ligands. Further studies demonstrated that low-dose gemcitabine treatment increased interferon-γ expression and NK-cell activation in mice. Low-dose gemcitabine treatment was sufficient for inhibiting tumor growth with few side effects in vivo. These data suggest that low-dose gemcitabine-induced immunochemotherapy activated antitumor immunity in immunocompetent patients.

Natural Killer Cells in the Lungs.

The lungs, a special site that is frequently challenged by tumors, pathogens and other environmental insults, are populated by large numbers of innate immune cells. Among these, natural killer (NK) cells are gaining increasing attention. Recent studies have revealed that NK cells are heterogeneous populations consisting of distinct subpopulations with diverse characteristics, some of which are determined by their local tissue microenvironment. Most current information about NK cells comes from studies of NK cells from the peripheral blood of humans and NK cells from the spleen and bone marrow of mice. However, the functions and phenotypes of lung NK cells differ from those of NK cells in other tissues. Here, we provide an overview of human and mouse lung NK cells in the context of homeostasis, pathogenic infections, asthma, chronic obstructive pulmonary disease (COPD) and lung cancer, mainly focusing on their phenotype, function, frequency, and their potential role in pathogenesis or immune defense. A comprehensive understanding of the biology of NK cells in the lungs will aid the development of NK cell-based immunotherapies for the treatment of lung diseases.

Dysfunction of Natural Killer Cells by FBP1-Induced Inhibition of Glycolysis during Lung Cancer Progression.

Natural killer (NK) cells are effector lymphocytes with pivotal roles in the resistance against various tumors; dysfunction of NK cells often results in advanced tumor progression. Tumors develop in three stages comprising initiation, promotion, and progression, but little is known about the interrelationships between NK cells and tumor cells at different stages of tumor development. Here, we demonstrated that NK cells prevented tumor initiation potently but did not prevent tumor promotion or tumor progression in Kras-driven lung cancer. Moreover, loss of the antitumor effect in NK cells was closely associated with their dysfunctional state during tumor promotion and progression. Mechanistically, aberrant fructose-1,6-bisphosphatase (FBP1) expression in NK cells elicited their dysfunction by inhibiting glycolysis and impairing viability. Thus, our results show dynamic alterations of NK cells during tumor development and uncover a novel mechanism involved in NK cell dysfunction, suggesting potential directions for NK cell-based cancer immunotherapy involving FBP1 targeting.