Metastasis is the spread of cancer cells from a primary tumor to distant sites within the body to establish secondary tumors. Although this is an inefficient process, the consequences are devastating as metastatic disease accounts for >90% of cancer-related deaths. The formation of metastases is the result of a series of events that allow cancer cells to escape from the primary site, survive in the lymphatic system or blood vessels, extravasate and grow at distant sites. The metastatic capacity of a tumor is determined by genetic and epigenetic changes within the cancer cells as well as contributions from cells in the tumor microenvironment. Mouse models have proven to be an important tool for unraveling the complex interactions involved in the metastatic cascade and delineating its many stages. Here, we critically appraise the strengths and weaknesses of the current mouse models and highlight the recent advances that have been made using these models in our understanding of metastasis. We also discuss the use of these models for testing potential therapies and the challenges associated with the translation of these findings into the provision of new and effective treatments for cancer patients.

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Bone metastasis is the major cause of death in breast cancer. The lack of effective treatment suggests that disease mechanisms are still largely unknown. As a key component of the tumor microenvironment, macrophages promote tumor progression and metastasis. In this study, we found that macrophages are abundant in human and mouse breast cancer bone metastases. Macrophage ablation significantly inhibited bone metastasis growth. Lineage tracking experiments indicated that these macrophages largely derive from Ly6C+CCR2+ inflammatory monocytes. Ablation of the chemokine receptor, CCR2, significantly inhibited bone metastasis outgrowth and prolonged survival. Immunophenotyping identified that bone metastasis–associated macrophages express high levels of CD204 and IL4R. Furthermore, monocyte/macrophage-restricted IL4R ablation significantly inhibited bone metastasis growth, and IL4R null mutant monocytes failed to promote bone metastasis outgrowth. Together, this study identified a subset of monocyte-derived macrophages that promote breast cancer bone metastasis in an IL4R-dependent manner. This suggests that IL4R and macrophage inhibition can have potential therapeutic benefit against breast cancer bone disease.

Trp(redBODIPY) is the first red-emitting Trp-based amino acid for the preparation of fluorogenic peptides with retention of target binding affinity.

T-cell development in the thymus is largely controlled by an epigenetic program, involving in both DNA methylation and histone modifications. Previous studies have identified Cxxc1 as a regulator of both cytosine methylation and histone 3 lysine 4 trimethylation (H3K4me3). However, it is unknown whether Cxxc1 plays a role in thymocyte development. Here we show that T-cell development in the thymus is severely impaired in Cxxc1-deficient mice. Furthermore, we identify genome-wide Cxxc1-binding sites and H3K4me3 modification sites in wild-type and Cxxc1-deficient thymocytes. Our results demonstrate that Cxxc1 directly controls the expression of key genes important for thymocyte survival such as RORγt and for T-cell receptor signalling including Zap70 and CD8, through maintaining the appropriate H3K4me3 on their promoters. Importantly, we show that RORγt, a direct target of Cxxc1, can rescue the survival defects in Cxxc1-deficient thymocytes. Our data strongly support a critical role of Cxxc1 in thymocyte development.

The expression of coinhibitory receptors, such as CTLA-4, on effector T cells is a key mechanism for the negative regulation of T-cell activation. However, the transcriptional regulation of CTLA-4 is not well understood. Zfp281, a C2H2 zinc finger protein, is a negative regulator of pluripotency maintenance of embryonic stem cells. Nevertheless, the function of Zfp281 in differentiated cells has not been studied. We generated Zfp281 conditional knockout mice in which the function of the Zfp281 gene was conditionally disrupted by the Cd4 Cre transgene to study its impact on T cell function. Zfp281 had no effect on T-cell development, but CD4 + T cell activation and cytokine production were impaired due to diminished T-cell receptor signaling. Furthermore, Zfp281 deficiency inhibited in vivo T cell responses to Listeria monocytogenes infection. Using genome-wide expression profiling assays, we determined that Zfp281 repressed Ctla-4 expression by directly binding to GC-rich sites in its promoter, which inhibited the negative feedback of T cell activation. In line with this result, CTLA-4 blockade and shRNA knockdown partly rescued the reduced cytokine production caused by Zfp281 deficiency. These findings indicate that Zfp281 sustains CD4 + T lymphocyte activation by directly repressing Ctla-4 transcription.

Metastatic castration-resistant prostate cancer (PC) is the final stage of PC that acquires resistance to androgen deprivation therapies (ADT). Despite progresses in understanding of disease mechanisms, the specific contribution of the metastatic microenvironment to ADT resistance remains largely unknown. The current study identified that the macrophage is the major microenvironmental component of bone-metastatic PC in patients. Using a novel in vivo model, we demonstrated that macrophages were critical for enzalutamide resistance through induction of a wound-healing–like response of ECM–receptor gene expression. Mechanistically, macrophages drove resistance through cytokine activin A that induced fibronectin (FN1)-integrin alpha 5 (ITGA5)–tyrosine kinase Src (SRC) signaling cascade in PC cells. This novel mechanism was strongly supported by bioinformatics analysis of patient transcriptomics datasets. Furthermore, macrophage depletion or SRC inhibition using a novel specific inhibitor significantly inhibited resistant growth. Together, our findings elucidated a novel mechanism of macrophage-induced anti-androgen resistance of metastatic PC and a promising therapeutic approach to treat this deadly disease.

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