MerTK, a receptor tyrosine kinase (RTK) of the TYRO3/AXL/MerTK family, is expressed in myeloid lineage cells in which it acts to suppress proinflammatory cytokines following ingestion of apoptotic material. Using syngeneic mouse models of breast cancer, melanoma, and colon cancer, we found that tumors grew slowly and were poorly metastatic in MerTK -/-mice. Transplantation of MerTK -/-bone marrow, but not wild-type bone marrow, into lethally irradiated MMTV-PyVmT mice (a model of metastatic breast cancer) decreased tumor growth and altered cytokine production by tumor CD11b + cells. Although MerTK expression was not required for tumor infiltration by leukocytes, MerTK -/-leukocytes exhibited lower tumor cell-induced expression of wound healing cytokines, e.g., IL-10 and growth arrest-specific 6 (GAS6), and enhanced expression of acute inflammatory cytokines, e.g., IL-12 and IL-6. Intratumoral CD8 + T lymphocyte numbers were higher and lymphocyte proliferation was increased in tumor-bearing MerTK -/-mice compared with tumor-bearing wild-type mice. Antibody-mediated CD8 + T lymphocyte depletion restored tumor growth in MerTK -/-mice. These data demonstrate that MerTK signaling in tumor-associated CD11b + leukocytes promotes tumor growth by dampening acute inflammatory cytokines while inducing wound healing cytokines. These results suggest that inhibition of MerTK in the tumor microenvironment may have clinical benefit, stimulating antitumor immune responses or enhancing immunotherapeutic strategies.
Type 2 cancers have nearly twice the TAM density of type 1 cancers. This difference may be due to M1 macrophage predominance in the stroma of type 2 cancers.
Objective-Autologous bone marrow (BM) cells with a faulty gene corrected by gene targeting could provide a powerful therapeutic option for patients with genetic blood diseases. Achieving this goal is hindered by the low abundance of therapeutically useful BM cells and the difficulty of maintaining them in tissue culture long enough for completing gene targeting without them differentiating. Our objective was to devise a simple long-term culture system, using unfractioned BM cells, that maintains and expands therapeutically useful cells for ≥4 weeks.Materials and Methods-From 2 to 60 million BM cells from wild-type (WT) mice, or from mice carrying a truncated erythropoietin receptor transgene (tEpoR-tg), were plated with or without irradiated fetal-liver derived AFT024 stromal cells in 25 cm 2 culture flasks. Four-week cultured cells were analyzed and transplanted into sublethally irradiated thalassemic mice (1 million cells / mouse).Results-After 4 weeks, the cultures with AFT024 cells had extensive "cobblestone" areas. Optimum expansion of Sca-1 positive cells was 5.5-fold with 20 × 10 6 WT cells/flask and 27-fold with 2 × 10 6 tEpoR-tg cells. More than 85% of thalassemic mice transplanted with either type of cells had almost complete reversal of their thalassemic phenotype for at least 6 months, including blood smear dysmorphology, reticulocytosis, high ferritin plasma levels and hepatic/renal hemosiderosis.Conclusion-When plated at high cell densities on irradiated fetal-liver derived stromal cells, BM cells from WT mice maintain their therapeutic potential for 4 weeks in culture, which is sufficient time for correction of a faulty gene by targeting.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.