Tumor-associated macrophages (TAMs), the main part of immune cells in tumor microenvironment (TME), play a potent role in promoting tumorigenesis through mechanisms such as stimulating angiogenesis, enhancing tumor migration and suppressing antitumor immunity. MicroRNAs (miRNAs) are considered as crucial regulators in multiple biological processes. The relationship between miRNAs and macrophages function has been extensively reported, but the roles that miRNAs play in regulating TAMs phenotype remain unclear. In this study, we screened highly expressed microRNAs in TAMs, and first identified that miR-100 represented a TAMs-high expression pattern and maintained TAMs phenotype by targeting mTOR signaling pathway. Moreover, miR-100 expression level in TAMs was positively related to IL-1ra secretion, a traditional immune-suppressive cytokine, which was determined to promote tumor cells stemness via stimulating Hedgehog pathway. Mechanism study suggested that mTOR/Stat5a pathway was involved in IL-1ra transcriptional regulation process mediated by miR-100. More importantly, tumor metastasis and invasion capacity were significantly decreased in a 4T1 mouse breast cancer model injected intratumorally with miR-100 antagomir, and combination therapy with cisplatin showed much better benefit. In this study, we confirm that highly expressed miR-100 maintains the phenotype of TAMs and promotes tumor metastasis via enhancing IL-1ra secretion. Interfering miR-100 expression of TAMs in mouse breast cancer model could inhibit TAMs pro-tumor function and reduce tumor metastasis, which suggests that miR-100 could serve as a potential therapy target to remodel tumor microenvironment in breast cancer.
Considerable evidence suggests that proinflammatory pathways drive self-renewal of cancer stem-like cells (CSC), but the underlying mechanisms remain mainly undefined. Here we report that the let7 repressor LIN28B and its regulator IKBKB (IKKb) sustain cancer cell stemness by interacting with the Wnt/TCF7L2 (TCF4) signaling pathway to promote cancer progression. We found that LIN28B expression correlated with clinical progression and stemness marker expression in breast cancer patients. Functional studies demonstrated that the stemness properties of LIN28B-expressing human breast and lung cancer cells were enhanced by IKKb, whereas loss of LIN28B abolished stemness properties in these settings. These phenomena were driven through interactions with TCF7L2, which enhanced LIN28B expression by direct binding to intron 1 of the LIN28B gene, which in turn promoted TCF7L2 mRNA translation through a positive feedback loop. Notably, RNAimediated silencing of LIN28B or pharmacologic inhibition of IKKb was sufficient to suppress primary and metastatic tumor growth in vivo. Together, our results establish the LIN28B/ TCF7L2 interaction loop as a central mediator of cancer stemness driven by proinflammatory processes during progression and metastasis, possibly offering a new therapeutic target for generalized interventions in advanced cancers.
In this study, we present a medium throughput siRNA screen platform to identify inflammation genes that regulate cancer cell stemness. We identified several novel candidates that decrease OCT4 expression and reduce the ALDH+ subpopulation both of which are characteristic of stemness. Furthermore, one of the novel candidates ICAM3 up-regulates in the ALDH+ subpopulation, the side population and the developed spheres. ICAM3 knockdown reduces the side population, sphere formation and chemo-resistance in MDA-MB-231 human breast cancer cells and A549 lung cancer cells. In addition, mice bearing MDA-MB-231-shICAM3 cells develop smaller tumors and fewer lung metastases versus control. Interestingly, ICAM3 recruits and binds to Src by the YLPL motif in its intracellular domain which further activates the PI3K-AKT phosphorylation cascades. The activated p-AKT enhances SOX2 and OCT4 activity and thereby maintains cancer cell stemness. Meanwhile, the p-AKT facilitated p50 nuclear translocation/activation enhances p50 feedback and thereby promotes ICAM3 expression by binding to the ICAM3 promoter region. On this basis, Src and PI3K inhibitors suppress ICAM3-mediated signaling pathways and reduce chemo-resistance which results in tumor growth suppression in vitro and in vivo. In summary, we identify a potential CSC regulator and suggest a novel mechanism by which ICAM3 governs cancer cell stemness and inflammation.
Tumor-associated macrophages(TAMs),the main part of immune cells in tumor microenvironment(TME),play a potent role in promoting tumorigenesis. MicroRNAs (miRs) are considered to be crucial regulators in tumor progression. However, the role that miRs play in TAMs phenotype regulation still remains unclear. In this study, we demonstrated that miR-100 played an important role in maintaining TAMs phenotype and enhancing tumor stemness properties. First, miRNome of TAMs isolated from mouse breast tumor was performed. Compared with macrophages from normal spleen, 40 miRs candidates, in 150 TAMs-high and 169 TAMs-low expressed miRs which were selected from miRNome, were further identified by real-time PCR. Importantly, miR-100 was found with TAMs-high expression pattern(about 70 folds changes). Moreover, we found that miR-100 overexpressed RAW264.7 cells and peritoneal macrophages gained M2 phenotype such as CD206+ cells percentage. Mechanism study demonstrated that miR-100 up-regulated IL-1ra expression detected by cytokine array. Furthermore we found that IL-1ra could enhance 4T1 breast cancer cell stemness properties including increasing tumor cell sphere formation and drug resistance in vitro. Taken together, our results demonstrate that TAMs-high expressed miR-100 could function to maintain the phenotype of TAMs via targeting mTOR pathway, and promote tumorigenesis by enhancing IL-1ra secretion, which would also serve as a promising therapy target to remodel TME and tumor metastasis. Citation Format: Wei Wang, Yan Liu, Jian Guo, Huiwen He, Junling Xie, Chong Chen, Yunping Luo. MicroRNA-100/mTOR/IL-1ra signaling maintains TAMs phenotype and enhances tumor cell stemness property in mouse breast cancer. [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 724.
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