Do Tumor-Induced Myeloid-Derived Suppressor Cells Proliferate Outside of the Bone Marrow?
Mentor 1
Douglas Steeber
Location
Union Wisconsin Room
Start Date
27-4-2018 1:00 PM
Description
Myeloid-derived suppressor cells (MDSCs) are a heterogeneous class of immunosuppressive cells that, under pathological conditions, circulate in very high numbers and accumulate in the lymph nodes, spleen, and at tumor sites. MDSCs can be separated into two distinct populations, polymorphonuclear MDSCs (PMN-MDSCs) and monocytic MDSCs (M-MDSCs), based on the expression of cell surface markers. Previous studies in the lab using flow cytometry suggested that actively proliferating PMN-MDSCs and M-MDSCs were present in tumor-bearing mice outside of the bone marrow, specifically in the spleen and tumor tissue. The purpose of the present study was to follow up on this unexpected result using immunofluorescence microscopy to directly identify proliferating MDSCs in the tumor. To address this, 4T1 tumors were induced in female BALB/c mice and allowed to grow for 4 weeks. One hour prior to tissue harvest, the mice were injected with bromodeoxyuridine (BrdU), a thymidine analog used to identify proliferating cells. Harvested tissues were placed in OCT medium, rapidly frozen, and sectioned using a cryostat. Sections were labeled with antibodies specific for BrdU and an MDSC surface marker, Ly6G. A nuclear stain, DAPI, was used to identify all cells within the tissue section. Labeled sections were viewed using fluorescence microscopy. Multiple images from each tissue section were captured using a monochromatic digital camera, pseudocolored and overlayed. Data was collected from two separate tumors. Within tumor tissue, MDSCs were seen organized in large clusters and also as individual cells disbursed throughout the tissue. Interestingly, while BrdU+ proliferating tumor cells were abundant, few if any BrdU+ MDSCs were observed. This difference in results may be due to heterogeneity between tumors and therefore more tumors need to be analyzed before a final conclusion can be made.
Do Tumor-Induced Myeloid-Derived Suppressor Cells Proliferate Outside of the Bone Marrow?
Union Wisconsin Room
Myeloid-derived suppressor cells (MDSCs) are a heterogeneous class of immunosuppressive cells that, under pathological conditions, circulate in very high numbers and accumulate in the lymph nodes, spleen, and at tumor sites. MDSCs can be separated into two distinct populations, polymorphonuclear MDSCs (PMN-MDSCs) and monocytic MDSCs (M-MDSCs), based on the expression of cell surface markers. Previous studies in the lab using flow cytometry suggested that actively proliferating PMN-MDSCs and M-MDSCs were present in tumor-bearing mice outside of the bone marrow, specifically in the spleen and tumor tissue. The purpose of the present study was to follow up on this unexpected result using immunofluorescence microscopy to directly identify proliferating MDSCs in the tumor. To address this, 4T1 tumors were induced in female BALB/c mice and allowed to grow for 4 weeks. One hour prior to tissue harvest, the mice were injected with bromodeoxyuridine (BrdU), a thymidine analog used to identify proliferating cells. Harvested tissues were placed in OCT medium, rapidly frozen, and sectioned using a cryostat. Sections were labeled with antibodies specific for BrdU and an MDSC surface marker, Ly6G. A nuclear stain, DAPI, was used to identify all cells within the tissue section. Labeled sections were viewed using fluorescence microscopy. Multiple images from each tissue section were captured using a monochromatic digital camera, pseudocolored and overlayed. Data was collected from two separate tumors. Within tumor tissue, MDSCs were seen organized in large clusters and also as individual cells disbursed throughout the tissue. Interestingly, while BrdU+ proliferating tumor cells were abundant, few if any BrdU+ MDSCs were observed. This difference in results may be due to heterogeneity between tumors and therefore more tumors need to be analyzed before a final conclusion can be made.
