<div>Abstract<p>Nuclear receptor coactivator 2 (Ncoa2) is a member of the Ncoa family of coactivators, and we previously showed that Ncoa2 regulates the differentiation of induced regulatory T cells. However, it remains unknown if Ncoa2 plays a role in CD8<sup>+</sup> T-cell function. Here, we show that Ncoa2 promotes CD8<sup>+</sup> T cell–mediated immune responses against tumors by stimulating T-cell activation via upregulating PGC-1α expression to enhance mitochondrial function. Mice deficient in <i>Ncoa2</i> in T cells (<i>Ncoa2<sup>fl/fl</sup>/CD4<sup>Cre</sup></i>) displayed defective immune responses against implanted MC38 tumors, which associated with significantly reduced tumor-infiltrating CD8<sup>+</sup> T cells and decreased IFNγ production. Consistently, CD8<sup>+</sup> T cells from <i>Ncoa2<sup>fl/fl</sup>/CD4<sup>Cre</sup></i> mice failed to reject tumors after adoptive transfer into <i>Rag1<sup>−/−</sup></i> mice. Further, in response to TCR stimulation, <i>Ncoa2<sup>fl/fl</sup>/CD4<sup>Cre</sup></i> CD8<sup>+</sup> T cells failed to increase mitochondrial mass, showed impaired oxidative phosphorylation, and had lower expression of PGC-1α, a master regulator of mitochondrial biogenesis and function. Mechanically, T-cell activation–induced phosphorylation of CREB triggered the recruitment of Ncoa2 to bind to enhancers, thus, stimulating PGC-1α expression. Forced expression of PGC-1α in <i>Ncoa2<sup>fl/fl</sup>/CD4<sup>Cre</sup></i> CD8<sup>+</sup> T cells restored mitochondrial function, T-cell activation, IFNγ production, and antitumor immunity. This work informs the development of Ncoa2-based therapies that modulate CD8<sup>+</sup> T cell–mediated antitumor immune responses.</p></div>
Macrophages are essential in eliciting antibody-dependent cellular phagocytosis (ADCP) of cancer cells. However, a satisfactory anticancer efficacy of ADCP is contingent on early antibody administration, and resistance develops along with cancer progression. Here, we investigate the mechanisms underlying ADCP and demonstrate an effective combinatorial strategy to potentiate its efficacy. We identified paclitaxel as a universal adjuvant that efficiently potentiated ADCP by a variety of anticancer antibodies in multiple cancers. Rather than eliciting cytotoxicity on cancer cells, paclitaxel polarized macrophages toward a state with enhanced phagocytic ability. Paclitaxel-treated macrophages down-regulated cell surface CSF1R whose expression was negatively correlated with patient survival in multiple malignancies. The suppression of CSF1R in macrophages enhanced ADCP of cancer cells, suggesting a role of CSF1R in regulating macrophage phagocytic ability. Together, these findings define a potent strategy for using conventional anticancer drugs to stimulate macrophage phagocytosis and promote the therapeutic efficacy of clinical anticancer antibodies.
Baicalein is a bioactive flavone that is originally extracted from the root of Scutellaria baicalensis Georgi. This plant has long served as Chinese herbal medicine in the management of multiple diseases including inflammatory bowel diseases. Although it has been revealed that baicalein inhibits experimental colitis in mice, the molecular mechanisms still remain largely unrecognized.The experimental colitis was induced in mice by 3% dextran sulfate sodium (DSS) in drinking water. The mice were given baicalein (10 or 25 mg/kg) by gavage for 7 days before and after DSS administration. Expression of COX-2 and inducible nitric oxide synthase (iNOS) and molecules involved in NF-κB signaling, such as inhibitor of κBα (IκBα), pIκBα, p65, and phospho-p65 was examined by Western blot analysis in the tissue of the mouse colon. Activity of IκB kinase β (IKKβ) was assessed by measuring the relative amount of radioactive γ-phosphate of ATP transferred to the IκBα substrate protein. The expression and phosphorylation of STAT3 and its target gene cyclin D1 were also measured.Baicalein prominently mitigated the severity of DSS-induced colitis in mice. It inhibited the expression of COX-2 and iNOS. Moreover, baicalein attenuated activity and phosphorylation of IKKβ and subsequent degradation of IκBα. Baicalein suppressed the phosphorylation and nuclear translocation of p65, resulting in a reduced DNA binding activity of NF-κB. Baicalein also suppressed the phosphorylation of STAT3 and expression of cyclin D1. Baicalein exhibited the synergistic effect on inhibition of COX-2 induced by DSS with curcumin, an ingredient of turmeric.Protective effects of baicalein on DSS-induced colitis are associated with suppression of NF-κB and STAT3 signaling pathways, which may contribute to its cancer preventive effects on colon carcinogenesis.
Curcumin, a yellow ingredient of turmeric (Curcuma longa Linn, Zingiberaceae), has long been used in traditional folk medicine in the management of inflammatory disorders. Although curcumin has been reported to inhibit experimentally-induced colitis and carcinogenesis, the underlying molecular mechanisms remain largely unresolved.Murine colitis was induced by dextran sulfate sodium (DSS) which mimics inflammatory bowel disease. Curcumin or tetrahydrocurcumin was given orally (0.1 or 0.25 mmol/kg body weight daily) for 7 days before and together with DSS administration (3% in tap water). Collected colon tissue was used for histologic and biochemical analyses.Administration of curcumin significantly attenuated the severity of DSS-induced colitis and the activation of NF-κB and STAT3 as well as expression of COX-2 and inducible nitric oxide synthase. In contrast to curcumin, its non-electrophilic analogue, tetrahydrocurcumin has much weaker inhibitory effects.Intragastric administration of curcumin inhibited the experimentally induced murine colitis, which was associated with inhibition of pro-inflammatory signaling mediated by NF-κB and STAT3.
Tumor-associated macrophages (TAMs) represent one of the most abundant components of the tumor microenvironment and play important roles in tumor development and progression. TAMs display plasticity and functional heterogeneity as reflected by distinct phenotypic subsets. TAMs with an M1 phenotype have proinflammatory and anti-tumoral properties whereas M2-like TAMs exert anti-inflammatory and pro-tumoral functions. Tumor cell debris generated during chemotherapy can stimulate primary tumor growth and recurrence. According to our previous study, phagocytic engulfment of breast tumor cell debris by TAMs attenuated chemotherapeutic efficacy through the upregulation of heme oxygenase-1 (HO-1). To verify the impact of HO-1 upregulation on the profile of macrophage polarization during cytotoxic therapy, we utilized a syngeneic murine breast cancer (4T1) model in which tumor bearing mice were treated with paclitaxel (PTX). PTX treatment markedly downregulated the surface expression of the M1 marker CD86 in infiltrated TAMs. Notably, there were significantly more cytotoxic CD8+ T cells in tumors of mice treated with PTX plus the HO-1 inhibitor, zinc protophorphyrin IX (ZnPP) than in mice treated with PTX alone. Interestingly, the tumor-inhibiting efficacy of PTX and ZnPP co-treatment was abrogated when macrophages were depleted by clodronate liposomes. Macrophage depletion also decreased the intratumoral CD8+ T cell population and downregulated the expression of Cxcl9 and Cxcl10. The expression of the M1 phenotype marker, CD86 was higher in mice injected with PTX plus ZnPP than that in mice treated with PTX alone. Conversely, the PTX-induced upregulation of the M2 marker gene, Il10 in CD11b+ myeloid cells from 4T1 tumor-bearing mice treated was dramatically reduced by the administration of the HO-1 inhibitor. Genetic ablation of HO-1 abolished the inhibitory effect of 4T1 tumor cell debris on expression of M1 marker genes, Tnf and Il12b, in LPS-stimulated BMDMs. HO-1-deficient BMDMs exposed to tumor cell debris also exhibited a diminished expression of the M2 macrophage marker, CD206. These findings, taken all together, provide strong evidence that HO-1 plays a pivotal role in the transition of tumor-inhibiting M1-like TAMs to tumor-promoting M2-like ones during chemotherapy.
Steroid receptor coactivator (SRC) family members (SRC1, SRC2 and SRC3) are transcriptional co-regulators. SRCs orchestrate gene transcription by inducing transactivation of nuclear receptors and other transcription factors. Overexpression of SRCs is widely implicated in a range of cancers, especially hormone-related cancers. As coactivators, SRCs regulate multiple metabolic pathways involved in tumor growth, invasion, metastasis, and chemo-resistance. Emerging evidence in recent years suggest that SRCs also regulate maturation, differentiation, and cytotoxicity of T cells by controlling metabolic activities. In this review, we summarize the current understanding of the function of SRCs in T cells as well as cancer cells. Importantly, the controversies of targeting SRCs for cancer immunotherapy as well as possible reconciliation strategies are also discussed.
Abstract Resolution of inflammation is an active process which is important for maintaining or restoring homeostasis in response to inflammatory insult. Failure in resolution results in persistent and chronic inflammation which increases the risk of cancer development. Efferocytosis, an essential part of resolution of inflammation, is defined as phagocytic removal of apoptotic cells, especially neutrophils, at the inflamed site, thereby preventing exposure of tissue to toxic intracellular components. It is carried out by a distinct group of phagocytes including anti-inflammatory macrophages (M2 type). Therefore, M2 macrophages represent a key component of the cellular proresolving mechanism and a potential factor for prevention of inflammation-associated cancer. Dysregulation, often overexpression, of c-Myc drives dedifferentiation of cancer cells to acquire capacity for self-renewal and metastasis, which accounts for poor prognosis in cancer patients. A cytoplasmic N-terminal part of full length c-Myc, termed Myc-nick, has been reported to promote differentiation of myoblasts. In the present study, we investigated whether Myc-nick is involved in M2 macrophage polarization and promotion of efferocytosis. We found that ectopic expression of Myc-nick in mouse bone marrow derived macrophages (BMDM) promoted the M2 macrophage polarization through upregulation of interleukin 10 (IL-10) and peroxisome proliferator activated receptor gamma (PPARγ). Furthermore, overexpression of exogenous Myc-nick in BMDM increased capture of apoptotic cells by BMDM through upregulation of a class of phosphatidyl serine (PS) receptors including T-cell immunoglobulin and mucin domain containing 4 (Timd4). PS constitutes one of ‘eat-me’ signals carried by apoptotic cells. PS receptors present on the surface of macrophages are important to recognize, engulf and finally clear apoptotic cells via phagocytosis. In addition, Myc-nick-induced efferocytosis was found to be tightly associated with K (lysine) acetyltransferase 2A (Kat2a/Gcn5). This may lead to the acetylation of transcription factors that regulate expression of PS receptor proteins. In conclusion, activation of M2 macrophages by Myc-nick facilitates efferocytosis and hence resolution of inflammation, and this may suppress inflammation-associated cancer progression. Citation Format: Xiancai Zhong, Ha-Na Lee, Young-Joon Surh. Myc-nick promotes efferocytosis through M2 macrophage polarization. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 825.
Chemotherapy is commonly used as a major therapeutic option for breast cancer treatment, but its efficacy is often diminished by disruption of patient's anti-tumor immunity.Chemotherapy-generated tumor cell debris could hijack accumulated tumor-associated macrophages (TAMs), provoking tumor recurrence.Therefore, reprogramming TAMs to acquire an immunocompetent phenotype is a promising strategy to potentiate therapeutic efficacy.In this study, we analyzed the proportion of immune cells in the breast cancer patients who received chemotherapy.To validate our findings in vivo, we used a syngeneic murine breast cancer (4T1) model.Chemotherapy generates an immunosuppressive tumor microenvironment in breast cancer.Here, we show that phagocytic engulfment of tumor cell debris by TAMs reduces chemotherapeutic efficacy in a 4T1 breast cancer model.Specifically, the engulfment of tumor cell debris by macrophages reduced M1-like polarization through heme oxygenase-1 (HO-1) upregulation.Conversely, genetic or pharmacologic inhibition of HO-1 in TAMs restored the M1-like polarization.Our results demonstrate that tumor cell debris-induced HO-1 expression in macrophages regulates their polarization.Inhibition of HO-1 overexpression in TAMs may provoke a robust anti-tumor immune response, thereby potentiating the efficacy of chemotherapy.
<div>Abstract<p>Nuclear receptor coactivator 2 (Ncoa2) is a member of the Ncoa family of co-activators, and we previously showed that Ncoa2 regulates the differentiation of induced regulatory T cells. However, it remains unknown if Ncoa2 plays a role in CD8+ T-cell function. Here, we show that Ncoa2 promotes CD8+ T cell-mediated immune responses against tumors by stimulating T-cell activation via upregulating PGC-1α expression to enhance mitochondrial function. Mice deficient in Ncoa2 in T cells (Ncoa2fl/fl/CD4Cre) displayed defective immune responses against implanted MC38 tumors, which associated with significantly reduced tumor-infiltrating CD8+ T cells and decreased IFNγ production. Consistently, CD8+ T cells from Ncoa2fl/fl/CD4Cre mice failed to reject tumors after adoptive transfer into Rag1-/- mice. Further, in response to TCR stimulation, Ncoa2fl/fl/CD4Cre CD8+ T cells failed to increase mitochondrial mass, showed impaired oxidative phosphorylation, and had lower expression of PGC-1α, a master regulator of mitochondrial biogenesis and function. Mechanically, T cell activation-induced phosphorylation of CREB triggered the recruitment of Ncoa2 to bind to enhancers, thus, stimulating PGC-1α expression. Forced expression of PGC-1α in Ncoa2fl/fl/CD4Cre CD8+ T cells restored mitochondrial function, T-cell activation, IFNγ production, and anti-tumor immunity. This work informs the development of Ncoa2-based therapies that modulate CD8+ T cell-mediated anti-tumor immune responses.</p></div>
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