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PMID: 31488209 Published · epublish English Journal Article Research Support, Non-U.S. Gov't

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

Breast cancer research : BCR ·Vol. 21 ·No. 1 ·2019-00-05 ·Pages 103

Bosiljcic M, Cederberg RA, Hamilton MJ, LePard NE, Harbourne BT, Collier JL, Halvorsen EC, Shi R, Franks SE, Kim AY, Banáth JP, Hamer M, Rossi FM, Bennewith KL

Abstract

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.

Keywords

4T07 4T1 67NR Eosinophils Gemcitabine Macrophages Metastasis Myeloid-derived suppressor cells Tumor resection

MeSH Terms

Animals Antigens, Ly/metabolism Antineoplastic Agents/pharmacology,therapeutic use CD11b Antigen/metabolism Cell Line, Tumor Combined Modality Therapy Deoxycytidine/analogs & derivatives,therapeutic use Eosinophils/pathology Female Killer Cells, Natural/pathology Lung Neoplasms/immunology,secondary,therapy Macrophages/pathology Mammary Neoplasms, Experimental/pathology Mastectomy Mice Mice, Inbred BALB C Myeloid-Derived Suppressor Cells/drug effects,immunology

Chemicals

Antigens, Ly Antineoplastic Agents CD11b Antigen Itgam protein, mouse Ly6G antigen, mouse Deoxycytidine gemcitabine

Authors & Affiliations

14 authors, click to expand affiliations / ORCID

Bosiljcic Momir

Integrative Oncology Department, BC Cancer Research Centre, Room 10-108, 675 West 10th Avenue, Vancouver, British Columbia, V5Z 1L3, Canada. | Pathology and Laboratory Medicine, University of British Columbia, Vancouver, British Columbia, Canada.

Cederberg Rachel A

Hamilton Melisa J