Type 2 Endometrial Cancer is Associated With a High Density of Tumor-Associated Macrophages in the Stromal Compartment.

INTRODUCTION: Tumor-associated macrophages (TAMs) play a pivotal role in orchestrating the microenvironment. The TAMs differentially polarize into M1 or M2 macrophages with distinct actions. The aim of our work is to characterize density, subtype, and location of TAMs in endometrial hyperplasia and cancer. METHODS: Formalin-fixed, paraffin-embedded sections of hyperplasia (n = 5), type 1 (n = 5), and type 2 (n = 5) endometrial cancer were stained with anti-CD68 and anti-CD163 monoclonal antibodies as markers for total TAMs and M2 TAMs, respectively. Macrophages were counted at 40× magnification in 10 high-power fields (HPFs) per slide by 4 observers. Repeated measures models were constructed to determine the relationships between macrophages and lesion categories. RESULTS: Most CD68+ TAMs were located in the stromal (mean = 41.0/HPF) compared to epithelial (mean = 11.0/HPF) or luminal (mean = 11.6/HPF) compartments. Similar but reduced findings were observed for CD163+ (M2 subtype) TAMs. The CD68+ stromal TAM density was highest in patients with type 2 cancers (mean = 54.0/HPF) compared to those with type 1 cancers (mean = 35.5/HPF) and hyperplasia (mean = 29.0/HPF). Women with hyperplasia had more CD163+ (M2 subtype) TAMs (26.7/HPF) than patients with either type of cancer (type 1 = 12.5/HPF and type 2 = 11.5/HPF). Based on the repeated measures models, type 2 cancers had 38.6/HPF more CD68+ TAMs than type 1 cancers (P < .0001) and type 1 and type 2 cancers had similar numbers of CD163+ TAMs (P = .27). CONCLUSIONS: 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.

MerTK inhibition in tumor leukocytes decreases tumor growth and metastasis.

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.

Therapeutic benefits in thalassemic mice transplanted with long-term-cultured bone marrow cells.

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 maintaining them in tissue culture long enough to complete gene targeting without 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 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, 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) truncated erythropoietin receptor transgene 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. CONCLUSIONS: 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.