Metastasis to distant tissues is the chief driver of breast cancer-related mortality, but little is known about the systemic physiologic dynamics that regulate this process. To investigate the role of neuroendocrine activation in cancer progression, we used in vivo bioluminescence imaging to track the development of metastasis in an orthotopic mouse model of breast cancer. Stress-induced neuroendocrine activation had a negligible effect on growth of the primary tumor but induced a 30-fold increase in metastasis to distant tissues including the lymph nodes and lung. These effects were mediated by β-adrenergic signaling, which increased the infiltration of CD11b + F4/80 + macrophages into primary tumor parenchyma and thereby induced a prometastatic gene expression signature accompanied by indications of M2 macrophage differentiation. Pharmacologic activation of β-adrenergic signaling induced similar effects, and treatment of stressed animals with the β-antagonist propranolol reversed the stress-induced macrophage infiltration and inhibited tumor spread to distant tissues. The effects of stress on distant metastasis were also inhibited by in vivo macrophage suppression using the CSF-1 receptor kinase inhibitor GW2580. These findings identify activation of the sympathetic nervous system as a novel neural regulator of breast cancer metastasis and suggest new strategies for antimetastatic therapies that target the β-adrenergic induction of prometastatic gene expression in primary breast cancers.

Radiotherapy is used to treat many types of cancer, but many treated patients relapse with local tumor recurrence. Tumor-infiltrating myeloid cells (TIMs), including CD11b (ITGAM)+F4/80 (EMR1)+ tumor-associated macrophages (TAMs) and CD11b+Gr-1 (LY6G)+ myeloid-derived suppressor cells (MDSCs), respond to cancer-related stresses and play critical roles in promoting tumor angiogenesis, tissue remodeling and immunosuppression. In this report, we employed a prostate cancer model to investigate the effects of irradiation on TAMs and MDSCs in tumor-bearing animals. Unexpectedly, when primary tumor sites were irradiated we observed a systemic increase of MDSCs in spleen, lung, lymph nodes and peripheral blood. Cytokine analysis showed that the macrophage colony-stimulating factor CSF1 increased by 2-fold in irradiated tumors. Enhanced macrophage migration induced by conditioned media from irradiated tumor cells was completely blocked by a selective inhibitor of CSF1R. These findings were confirmed in prostate cancer patients, where serum levels of CSF1 increased after radiotherapy. Mechanistic investigations revealed the recruitment of the DNA damage-induced kinase ABL1 into cell nuclei where it bound the CSF1 gene promoter and enhanced CSF1 gene transcription. When added to radiotherapy, a selective inhibitor of CSF1R suppressed tumor growth more effectively than radiation alone. Our results highlight the importance of CSF1/CSF1R signaling in the recruitment of TIMs which can limit the efficacy of radiotherapy. Further, they suggest that CSF1 inhibitors should be evaluated in clinical trials in combination with radiotherapy as a strategy to improve outcomes.

An average cell contains thousands of proteins that participate in normal cellular functions, and most diseases are somehow related to the malfunctioning of one or more of these proteins. Protein therapy, which delivers proteins into the cell to replace the dysfunctional protein, is considered the most direct and safe approach for treating disease. However, the effectiveness of this method has been limited by its low delivery efficiency and poor stability against proteases in the cell, which digest the protein. Here, we show a novel delivery platform based on nanocapsules consisting of a protein core and a thin permeable polymeric shell that can be engineered to either degrade or remain stable at different pHs. Non-degradable capsules show long-term stability, whereas the degradable ones break down their shells, enabling the core protein to be active once inside the cells. Multiple proteins can be delivered to cells with high efficiency while maintaining low toxicity, suggesting potential applications in imaging, therapy and cosmetics fields.

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SUMMARY Recent studies underscore the importance of myeloid cells in rendering distant organs hospitable for disseminating tumor cells to colonize. However, what enables myeloid cells to have an apparently superior capacity to colonize distant organs is unclear. Here we show that S1PR1-STAT3 upregulation in tumor cells induces factors that activate S1PR1-STAT3 in various cells in pre-metastatic sites, leading to pre-metastatic niche formation. Targeting either S1PR1 or STAT3 in myeloid cells disrupts existing pre-metastatic niches. S1PR1-STAT3 pathway enables myeloid cells to intravasate, prime the distant organ microenvironment and mediate sustained proliferation and survival of their own and other stromal cells at future metastatic sites. Analyzing tumor-free lymph nodes from cancer patients shows elevated myeloid infiltrates, STAT3 activity and increased survival signal.

The success of adoptive therapy using chimeric antigen receptor (CAR)-expressing T cells partly depends on optimal CAR design. CARs frequently incorporate a spacer/linker region based on the constant region of either IgG1 or IgG4 to connect extracellular ligand-binding with intracellular signaling domains. Here, we evaluated the potential for the IgG4-Fc linker to result in off-target interactions with Fc gamma receptors (FcγRs). As proof-of-principle, we focused on a CD19-specific scFv-IgG4-CD28-zeta CAR and found that, in contrast to CAR-negative cells, CAR+ T cells bound soluble FcγRs in vitro and did not engraft in NSG mice. We hypothesized that mutations to avoid FcγR binding would improve CAR+ T cell engraftment and antitumor efficacy. Thus, we generated CD19-specific CARs with IgG4-Fc spacers that had either been mutated at two sites (L235E; N297Q) within the CH2 region (CD19R(EQ)) or incorporated a CH2 deletion (CD19Rch2Δ). These mutations reduced binding to soluble FcγRs without altering the ability of the CAR to mediate antigen-specific lysis. Importantly, CD19R(EQ) and CD19Rch2Δ T cells exhibited improved persistence and more potent CD19-specific antilymphoma efficacy in NSG mice. Together, these studies suggest that optimal CAR function may require the elimination of cellular FcγR interactions to improve T cell persistence and antitumor responses.

Purpose: Metastasis to the brain from breast cancer remains a significant clinical challenge, and may be targeted with CAR-based immunotherapy. CAR design optimization for solid tumors is crucial due to the absence of truly restricted antigen expression and potential safety concerns with “on-target off-tumor” activity. Here, we have optimized HER2-CAR T cells for the treatment of breast to brain metastases, and determined optimal second-generation CAR design and route of administration for xenograft mouse models of breast metastatic brain tumors, including multifocal and leptomeningeal disease. Experimental Design: HER2-CAR constructs containing either CD28 or 4-1BB intracellular costimulatory signaling domains were compared for functional activity in vitro by measuring cytokine production, T-cell proliferation, and tumor killing capacity. We also evaluated HER2-CAR T cells delivered by intravenous, local intratumoral, or regional intraventricular routes of administration using in vivo human xenograft models of breast cancer that have metastasized to the brain. Results: Here, we have shown that HER2-CARs containing the 4-1BB costimulatory domain confer improved tumor targeting with reduced T-cell exhaustion phenotype and enhanced proliferative capacity compared with HER2-CARs containing the CD28 costimulatory domain. Local intracranial delivery of HER2-CARs showed potent in vivo antitumor activity in orthotopic xenograft models. Importantly, we demonstrated robust antitumor efficacy following regional intraventricular delivery of HER2-CAR T cells for the treatment of multifocal brain metastases and leptomeningeal disease. Conclusions: Our study shows the importance of CAR design in defining an optimized CAR T cell, and highlights intraventricular delivery of HER2-CAR T cells for treating multifocal brain metastases. Clin Cancer Res; 24(1); 95–105. ©2017 AACR.

Growing evidence suggests that tumor-associated macrophages (TAMs) promote cancer progression and therapeutic resistance by enhancing angiogenesis, matrix-remodeling and immunosuppression. In this study prostate cancer (PCa) under androgen blockade therapy (ABT) was investigated, demonstrating that TAMs contribute to PCa disease recurrence through paracrine signaling processes. ABT induced the tumor cells to express macrophage colony-stimulating factor 1 (M-CSF-1 or CSF-1) and other cytokines that recruit and modulate macrophages, causing a significant increase in TAM infiltration. Inhibitors of CSF-1 signaling through its receptor, CSF-1R, were tested in combination with ABT, demonstrating that blockade of TAM influx in this setting disrupts tumor promotion and sustains a more durable therapeutic response compared to ABT alone.