Project description:Streptococcus pneumoniae is the leading cause of community-acquired pneumonia. Mertk is an efferocytosis receptor involved in the recognition and removal of apoptotic debris by macrophages and other phagocytic cells. Here we show that Mertk negatively regulates the clearance of S. pneumoniae, as measured by the greater number of viable bacteria in the lung of wild type vs. Mertk-/- mice 24 hours post-inoculation. The impaired clearance observed in wild type mice was associated with a greater number of neutrophils in the bronchoalveolar lavage (BAL) and lower concentration of IFNγ in the BAL fluid; however, similar enhancement of clearance was observed in Mertk-/- mice receiving neutralizing IFNγ antibody. Mertk is highly expressed on alveolar macrophages. Transcriptomic changes observed in primary Mertk-/- alveolar macrophages were associated with leukocyte activation, cellular motility, and response to stimulus. Mertk deficiency similarly enhanced proinflammatory gene expression in S. pneumoniae-stimulated alveolar macrophages in vitro and in pneumonic lung tissue. Thus, Mertk contributes to alveolar macrophage homeostasis through the receptor’s immunomodulatory role. Naive Mertk-/- alveolar macrophages appear primed for an inflammatory response to S. pneumoniae leading to greater cell motility, improved bacterial killing and enhancement of other innate immune cells through the production of inflammatory mediators.
Project description:Streptococcus pneumoniae is the leading cause of community-acquired pneumonia. Mertk is an efferocytosis receptor involved in the recognition and removal of apoptotic debris by macrophages and other phagocytic cells. Here we show that Mertk negatively regulates the clearance of S. pneumoniae, as measured by the greater number of viable bacteria in the lung of wild type vs. Mertk-/- mice 24 hours post-inoculation. The impaired clearance observed in wild type mice was associated with a greater number of neutrophils in the bronchoalveolar lavage (BAL) and lower concentration of IFNγ in the BAL fluid; however, similar enhancement of clearance was observed in Mertk-/- mice receiving neutralizing IFNγ antibody. Mertk is highly expressed on alveolar macrophages. Transcriptomic changes observed in primary Mertk-/- alveolar macrophages were associated with leukocyte activation, cellular motility, and response to stimulus. Mertk deficiency similarly enhanced proinflammatory gene expression in S. pneumoniae-stimulated alveolar macrophages in vitro and in pneumonic lung tissue. Thus, Mertk contributes to alveolar macrophage homeostasis through the receptor’s immunomodulatory role. Naive Mertk-/- alveolar macrophages appear primed for an inflammatory response to S. pneumoniae leading to greater cell motility, improved bacterial killing and enhancement of other innate immune cells through the production of inflammatory mediators.
Project description:Streptococcus pneumoniae is the leading cause of community-acquired pneumonia. Mertk is an efferocytosis receptor involved in the recognition and removal of apoptotic debris by macrophages and other phagocytic cells. Here we show that Mertk negatively regulates the clearance of S. pneumoniae, as measured by the greater number of viable bacteria in the lung of wild type vs. Mertk-/- mice 24 hours post-inoculation. The impaired clearance observed in wild type mice was associated with a greater number of neutrophils in the bronchoalveolar lavage (BAL) and lower concentration of IFNγ in the BAL fluid; however, similar enhancement of clearance was observed in Mertk-/- mice receiving neutralizing IFNγ antibody. Mertk is highly expressed on alveolar macrophages. Transcriptomic changes observed in primary Mertk-/- alveolar macrophages were associated with leukocyte activation, cellular motility, and response to stimulus. Mertk deficiency similarly enhanced proinflammatory gene expression in S. pneumoniae-stimulated alveolar macrophages in vitro and in pneumonic lung tissue. Thus, Mertk contributes to alveolar macrophage homeostasis through the receptor’s immunomodulatory role. Naive Mertk-/- alveolar macrophages appear primed for an inflammatory response to S. pneumoniae leading to greater cell motility, improved bacterial killing and enhancement of other innate immune cells through the production of inflammatory mediators.
Project description:Molecularly-targeted agents have improved outcomes for a subset of patients with BRAF-mutated melanoma, but treatment of resistant and BRAF wild-type tumors remains a challenge. The MERTK receptor tyrosine kinase is aberrantly expressed in melanoma and can contribute to oncogenic phenotypes. Here we report the effect of treatment with a MERTK-selective small molecule inhibitor, UNC2025, in preclinical models of melanoma. In melanoma cell lines, treatment with UNC2025 potently inhibited phosphorylation of MERTK and downstream signaling, induced cell death, and decreased colony formation. In patient-derived melanoma xenograft models, treatment with UNC2025 blocked or significantly reduced tumor growth. Importantly, UNC2025 had similar biochemical and functional effects in both BRAF-mutated and BRAF wild-type models and irrespective of NRAS mutational status, implicating MERTK inhibition as a potential therapeutic strategy in tumors that are not amenable to BRAF-targeting and for which there are limited treatment options. In BRAF-mutated cell lines, combined treatment with UNC2025 and the BRAF inhibitor vemurafenib provided effective inhibition of oncogenic signaling through ERK, AKT, and STAT6, increased induction of cell death, and decreased colony-forming potential. Similarly, in NRAS-mutated cell lines, addition of UNC2025 to cobimetinib therapy increased cell death and decreased colony-forming potential. In a BRAF-mutated patient-derived xenograft, treatment with combined UNC2025 and vemurafenib was well-tolerated and significantly decreased tumor growth compared with vemurafenib alone. These data support the use of UNC2025 for treatment of melanoma, irrespective of BRAF or NRAS mutational status, and suggest a role for MERTK and targeted combination therapy in BRAF and NRAS-mutated melanoma.