Objectives: Mobilization of immune cells is often associated with prognosis and treatment response for many diseases. The objective of this study was to test whether mobilization of CD11b+ myeloid cells could be noninvasively imaged by PET/CT. Methods: Anti-mouse CD11b antibody was labeled with 64Cu. Immunocompetent mice with 12-o-tetradecanoylphorbol-13-acetate (TPA)-induced acute inflammation in the ears, lipopolysaccharide (LPS)-induced inflammation in the lung, mice bearing 3 different syngeneic murine tumors (4T1 mammary carcinoma, CMS4 sarcoma, and CT26 colon carcinoma), and mice bearing ID8 ovarian cancer undergoing photothermal therapy were imaged with [64Cu]-labeled anti-CD11b. microPET-CT imaging and biodistribution were obtained at 24 h after intravenous injection of the radiotracer. Subpopulations of bone marrow cells, cells from spleen, and cells from the disease sites were analyzed by flow cytometry and/or immunohistochemistry (IHC) staining. Results: 64Cu-labeled anti-CD11b bound specifically to CD11b+ myeloid cells. microPET-CT images showed significantly higher uptake of 64Cu-DOTA-anti-CD11b antibody at the inflammatory sites and tumors undergoing photothermal therapy. In addition, microPET-CT images also revealed mobilization of CD11b+ cells from bone marrow to secondary lymphoid organs (spleen and/or lymph nodes). Interestingly, mice bearing 4T1 carcinoma displayed a markedly different imaging/distribution pattern compared to mice bearing CMS4 and CT26 tumors, characterized by a significant increase in blood pool and liver activities with corresponding reduction in the uptake of the radiotracer in the bone marrow and the spleen in different stages of tumor development. These findings were evaluated in the context of flow cytometry and IHC analyses. Conclusions: The differential distribution pattern of 64Cu-labeled anti-CD11b in different disease models could be attributed to mobilization of CD11b+ cells. PET/CT may be used to image systems response of immune cells to disease development and treatments. (Supported in part by the John S. Dunn Foundation)

Citation Format: Qizhen Cao, Qian Huang, Chun Li. microPET/CT imaging of the mobilization of CD11b+ cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4207.