西达本胺通过调控肿瘤相关巨噬细胞功能增强对结肠癌细胞的抑制作用

[摘要] 目的：探讨肿瘤相关巨噬细胞（TAM）对西达本胺（chidamide）抑瘤效果的影响及其作用机制。方法：体外培养小鼠巨噬细胞系Ana1 和Raw264.7,用肿瘤上清诱导成为TAM。用西达本胺处理TAM后,用比色法检测HDAC酶活性,用qPCR检测TAM中IL-6、IL-12、TNF、IL-1β 等细胞因子的mRNA表达水平,用Wb 实验检测西达本胺处理后TAM中NF-κB和STAT3 蛋白的表达水平。将TAM和结肠癌CT26 细胞混合后,接种到裸鼠体内构建皮下移植瘤模型,灌喂西达本胺（3.87 mg/kg）,观察西达本胺对皮下移植瘤生长的影响,并通过免疫组化检测移植瘤组织中PCNA、F4/80、Arg1、iNos 蛋白的表达水平。结果：西达本胺抑制CT26 细胞的增殖活性,在裸鼠体内西达本胺单独处理CT26 细胞皮下移植瘤的抑制率约为18.7%;当TAM存在时,西达本胺处理可以将移植瘤抑制率提高到57.2%。西达本胺可以抑制TAM的HDAC酶活性,进而使得组蛋白乙酰化水平升高;西达本胺能影响核内转录因子NF-κB 水平,并且降低Arg1、IL-6、IL-12 表达,提高iNos、Tnf、IL-1β 表达。结论：西达本胺通过抑制TAM中HDAC活性和调控细胞因子表达,增强其对于结肠癌CT26 细胞的抑制作用。     

Homeobox A7 promotes esophageal squamous cell carcinoma progression through C-C motif chemokine ligand 2-mediated tumor-associated macrophage recruitment

Homeobox A7 (HOXA7) plays essential roles in multiple malignancies and was reported to be overexpressed in esophageal squamous cell carcinoma (ESCC). However, its functions in the ESCC tumor microenvironment remain to be explored. In this study, we showed that HOXA7 was overexpressed in ESCC among HOXA family members and correlated with tumor-associated macrophage (TAM) infiltration both in The Cancer Genome Atlas database and ESCC clinical samples. Moreover, transactivation of C-C motif chemokine ligand 2 (CCL2) by HOXA7 was identified (real-time quantitative PCR [RT-qPCR], western blot analysis, ELISA, and ChIP-qPCR), which was detected to drive chemotaxis and M2 polarization of macrophages both in vitro (Transwell assay) and in vivo (xenograft tumors models). In addition, CCL2 triggers macrophage expression of epidermal growth factor (EGF) (RT-qPCR and ELISA), which promotes tumor proliferation and metastasis by activating its receptor EGFR. In addition, EGF-induced ESCC cell proliferation and migration can be abrogated by HOXA7 knockdown (CCK-8 proliferation assay, EdU fluorescence, and Transwell assay). These results indicate a novel mechanistic role of HOXA7 in the cross-talk between ESCC and TAMs, which could be an underlying therapeutic target for ESCC.     

Distinct role of CD8 cells and CD4 cells in antitumor immunity triggered by cell apoptosis using a Herpes simplex virus thymidine kinase/ganciclovir system

Immune cells can recognize tumor-associated antigens released from dead tumor cells, which elicit immune responses, potentially resulting in tumor regression. Tumor cell death induced by chemotherapy has also been reported to activate immunity. However, various studies have reported drug-induced immunosuppression or suppression of inflammation by apoptotic cells. Thus, this study aimed to investigate whether apoptotic tumor cells trigger antitumor immunity independent of anticancer treatment. Local immune responses were evaluated after direct induction of tumor cell apoptosis using a Herpes simplex virus thymidine kinase/ganciclovir (HSV-tk/GCV) system. The inflammatory response was significantly altered at the tumor site after apoptosis induction. The expression of cytokines and molecules that activate and suppress inflammation simultaneously increased. The HSV-tk/GCV-induced tumor cell apoptosis resulted in tumor growth suppression and promoted T lymphocyte infiltration into tumors. Therefore, the role of T cells after inducing tumor cell death was explored. CD8 T cell depletion abrogated the antitumor efficacy of apoptosis induction, indicating that tumor regression was mainly dependent on CD8 T cells. Furthermore, CD4 T cell depletion inhibited tumor growth, suggesting the potential role of CD4 T cells in suppressive tumor immunity. Tumor tissues were evaluated after tumor cell apoptosis and CD4 T cell depletion to elucidate this immunological mechanism. Foxp3 and CTLA4, regulatory T-cell markers, decreased. Furthermore, arginase 1, an immune-suppressive mediator induced by myeloid cells, was significantly downregulated. These findings indicate that tumors accelerate CD8 T cell-dependent antitumor immunity and CD4 T cell-mediated suppressive immunity. These findings could be a therapeutic target for immunotherapy in combination with cytotoxic chemotherapy.     

Influence of leptin and compression in GAS-6 mediated homeostasis of periodontal ligament cell

Growth arrest-specific protein 6 (GAS-6) regulates immunomodulatory and inflammatory mechanisms in periodontium and may participate in obesity predisposition. This study aimed to determine whether GAS-6 is associated with the homeostasis of periodontal ligament (SV-PDL) cells in the presence of adipokines or compressive forces. The SV-PDL cell line was used. Western blots were employed for TAM receptors detection. Cells were stimulated using different concentrations of GAS-6. The migration, viability, and proliferation were measured by a standard scratch test, MTS assay, and immunofluorescent staining. The mRNA expression was analyzed by RT-PCR. Release of TGF-β1, GAS-6, and Axl were verified by ELISA. Western blot shows that TAM receptors are expressed in SV-PDL cells. GAS-6 has a promoting effect on cell migration and proliferation. RT-PCR analysis showed that GAS-6 induces Collagen-1, Collagen-3, Periostin, and TGF-β1 mRNA expression whereas it reduces Caspase-3, Caspase-8, Caspase-9, and IL-6 mRNA expression. Further, secreted GAS-6 in SV-PDL is reduced in response to both compressive forces and leptin and upregulated by IL-6. Additionally, ADAM-10 inhibition reduces GAS-6 and Axl release on SV-PDL cells. TAM receptors especially Axl are identified as the receptors of GAS-6. GAS-6/TAM interactions contribute to periodontal ligament cells homeostasis. Leptin inhibits the GAS-6 release independently of ADAM-10 metalloprotease.     

Hypoxic niches attract and sequester tumor-associated macrophages and cytotoxic T cells and reprogram them for immunosuppression

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Engulfment and cell motility protein 1 fosters reprogramming of tumor-associated macrophages in colorectal cancer

Functional reprogramming of tumor-associated macrophages (TAMs) is crucial to their potent tumor-supportive capacity. However, the molecular mechanism behind the reprogramming process remains poorly understood. Here, we identify engulfment and cell motility protein 1 (ELMO1) as a crucial player for TAM reprogramming in colorectal cancer (CRC). The expression of ELMO1 in stromal but not epithelial tumor cells was positively associated with advanced clinical stage and poor disease-free survival in CRC. An increase in ELMO1 expression was specifically found in TAMs, but not in other multiple nonmalignant stromal cells. Gain- and loss-of-function assays indicated ELMO1 reprogrammed macrophages to a TAM-like phenotype through Rac1 activation. In turn, ELMO1-reprogrammed macrophages were shown to not only facilitate the malignant behaviors of CRC cells but exhibited potent phagocytosis of tumor cells. Taken together, our work underscores the importance of ELMO1 in determining functional reprogramming of TAMs and could provide new insights on potential therapeutic strategies against CRC.