Targeting myeloid-derived suppressor cells in combination with primary mammary tumor resection reduces metastatic growth in the lungs

• Published in: Breast cancer research : BCR Vol. 21; no. 1; p. 103
• Main Authors: Bosiljcic, Momir, Cederberg, Rachel A, Hamilton, Melisa J, LePard, Nancy E, Harbourne, Bryant T, Collier, Jenna L, Halvorsen, Elizabeth C, Shi, Rocky, Franks, S Elizabeth, Kim, Ada Y, Banáth, Judit P, Hamer, Mark, Rossi, Fabio M, Bennewith, Kevin L
• Format: Journal Article
• Language: English
• Published: England BioMed Central Ltd 05.09.2019; BioMed Central; BMC
• Subjects: Animals; Antigens, Ly - metabolism; Antineoplastic Agents - pharmacology; Antineoplastic Agents - therapeutic use; Bone marrow; Bone tumors; Breast cancer; Cancer metastasis; Care and treatment; CD11b antigen; CD11b Antigen - metabolism; Cell Line, Tumor; Chemotherapy; Colony-stimulating factor; Combined Modality Therapy; Dendritic cells; Deoxycytidine - analogs & derivatives; Deoxycytidine - therapeutic use; Effector cells; Eosinophils; Eosinophils - pathology; Female; Flow cytometry; Gemcitabine; Genetic aspects; Granulocyte colony-stimulating factor; Immunotherapy; Killer cells; Killer Cells, Natural - pathology; Leukocytes (eosinophilic); Leukocytes (granulocytic); Lung Neoplasms - immunology; Lung Neoplasms - secondary; Lung Neoplasms - therapy; Lungs; Lymphocytes; Macrophages; Macrophages - pathology; Mammary gland; Mammary Neoplasms, Experimental - pathology; Mastectomy; Metastases; Metastasis; Mice; Mice, Inbred BALB C; Monocytes; Murinae; Myeloid-derived suppressor cells; Myeloid-Derived Suppressor Cells - drug effects; Myeloid-Derived Suppressor Cells - immunology; Peripheral blood; Proteins; Solid tumors; Spleen; Suppressor cells; Surgery; Tumor cells; Tumor removal; Tumor resection; Tumors; Tumor resection; 4T1; Gemcitabine; Myeloid-derived suppressor cells; Metastasis; 67NR; Macrophages; 4T07; Eosinophils
• ISSN: 1465-542X; 1465-5411; 1465-542X
• DOI: 10.1186/s13058-019-1189-x

Solid tumors produce proteins that can induce the accumulation of bone marrow-derived cells in various tissues, and these cells can enhance metastatic tumor growth by several mechanisms. 4T1 murine mammary tumors are known to produce granulocyte colony-stimulating factor (G-CSF) and increase the numbers of immunosuppressive CD11b Gr1 myeloid-derived suppressor cells (MDSCs) in tissues such as the spleen and lungs of tumor-bearing mice. While surgical resection of primary tumors decreases MDSC levels in the spleen, the longevity and impact of MDSCs and other immune cells in the lungs after tumor resection have been less studied. We used mass cytometry time of flight (CyTOF) and flow cytometry to quantify MDSCs in the spleen, peripheral blood, and lungs of mice bearing orthotopic murine mammary tumors. We also tested the effect of primary tumor resection and/or gemcitabine treatment on the levels of MDSCs, other immune suppressor and effector cells, and metastatic tumor cells in the lungs. We have found that, similar to mice with 4T1 tumors, mice bearing metastatic 4T07 tumors also exhibit accumulation of CD11b Gr1 MDSCs in the spleen and lungs, while tissues of mice with non-metastatic 67NR tumors do not contain MDSCs. Mice with orthotopically implanted 4T1 tumors have increased granulocytic (G-) MDSCs, monocytic (M-) MDSCs, macrophages, eosinophils, and NK cells in the lungs. Resection of primary 4T1 tumors decreases G-MDSCs, M-MDSCs, and macrophages in the lungs within 48 h, but significant numbers of functional immunosuppressive G-MDSCs persist in the lungs for 2 weeks after tumor resection, indicative of an environment that can promote metastatic tumor growth. The chemotherapeutic agent gemcitabine depletes G-MDSCs, M-MDSCs, macrophages, and eosinophils in the lungs of 4T1 tumor-bearing mice, and we found that treating mice with gemcitabine after primary tumor resection decreases residual G-MDSCs in the lungs and decreases subsequent metastatic growth. Our data support the development of therapeutic strategies to target MDSCs and to monitor MDSC levels before and after primary tumor resection to enhance the effectiveness of immune-based therapies and improve the treatment of metastatic breast cancer in the clinic.