Abstract
Tumor associated macrophages are an essential part of the tumor microenvironment. Consequently, bone marrow-derived monocytes (BMDMs) are continuously recruited to tumors and are therefore seen as ideal delivery vehicles with tumor-targeting properties. By using immune cell depleting agents and macroscopic in vivo fluorescence imaging, we demonstrated that removal of endogenous monocytes and macrophages (but not neutrophils) leads to an increased tumor accumulation of exogenously administered BMDMs. By means of intravital microscopy (IVM), we confirmed our macroscopic findings on a cellular level and visualized in real time the migration of the donor BMDMs in the tumors of living animals. Moreover, IVM also revealed that clodronate-mediated depletion drastically increases the circulation time of the exogenously administered BMDMs. In summary, these new insights illustrate that impairment of the mononuclear phagocyte system increases the circulation time and tumor accumulation of donor BMDMs.
Highlights
Recruitment of immune cells to the tumor microenvironment followed by successful recognition of the tumor cells is essential for terminating tumor progression [1]
We demonstrated that depletion of macrophages and monocytes by clodronate (CLO) liposomes increased the accumulation of exogenously administered bone marrow-derived monocytes (BMDMs) in the tumor, lungs and spleen of mice
By combining advanced macroscopic and microscopic in vivo fluorescence imaging techniques, we revealed that depletion of macrophages and monocytes increased the blood circulation time, tumor-homing and extravasation of BMDMs at the tumor
Summary
Recruitment of immune cells to the tumor microenvironment followed by successful recognition of the tumor cells is essential for terminating tumor progression [1]. This fundamental process can contribute to the level of tumor malignancy [2,3]. This dual role of the immune system in the development of a tumor has been described by the immunoediting theory and consists of three consecutive phases: elimination, equilibrium and escape. Most of the tumor cells are killed by the immune system.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
