Abstract PS2-23: Prospective study of circulating cancer-associated macrophage-like cells (CAMLs) in obese patients with advanced breast cancer

Background Cancer-associated macrophage-like cells (CAMLs) are rare circulating gigantic atypical cells exclusively found in the peripheral blood of patients with solid cancers. CAMLs potentially originate from tumor-associated macrophages in the tumor microenvironment and may have a prognostic role in breast cancer. Obesity-induced local hypoxia attracts macrophages to the tumor microenvironment and activates macrophages to induce chronic inflammation, which can lead to breast cancer progression. However, little is known about the relationship between CAMLs, obesity, and body fat distribution. Also, the role of the CAMLs on breast cancer development needs to be investigated. We hypothesized that the number and size of CAMLs are correlated with body mass index (BMI), and we investigated the relationship between CAMLs and body composition. Materials and methods We prospectively collected 10 ml of peripheral blood from 30 patients initially diagnosed with advanced breast cancer who underwent computed tomography. Blood samples were drawn in CellSave tubes to preserve peripheral blood mononuclear cells. We used the CellSieve microfiltering system to isolate and identify CAMLs. After enumerating cells, we analyzed immunofluorescent staining for DAPI, CD14, CD45, CXCR4, and cytokeratin. CAMLs were identified by cell surface markers (CD14+, CD45+, and cytokeratin+) and morphology (multinuclear and giant cells >30 µm). BMI was measured at the time of diagnosis. The in-house 3D imaging analysis software Medical Executable for the Efficient and Robust Quantification of Adipose Tissue was used to calculate the total amount of abdominal visceral fat tissue (VAT) and subcutaneous fat tissue (SAT) between the upper diaphragm and pelvic end using multi-detector computed tomography data. The VAT:SAT ratio was also calculated. We quantified the expression of C-X-C chemokine receptor type 4 (CXCR4) in CAMLs to investigate the metastatic potential of the cells. Finally, we determined the relationship between the characteristics of CAMLs and BMI, body composition parameters, and CXCR4 using the Pearson correlation test. Results Of 30 collected samples, two had an inadequate amount of blood for evaluation. Among the remaining 28, we detected CAMLs in 24. The median BMI was 30.4 kg/m2, and half of the patients were categorized as obese by the World Health Organization BMI classification. BMI was correlated with the number (r=0.39, p=0.043), average size (r=0.42, p=0.039), and maximum size (r=0.50, p=0.013) of CAMLs. In body composition analysis, the maximum size of CAMLs was correlated with the total amount of VAT (r=0.51, p=0.012) and SAT (r=0.44, p=0.037) but not the VAT:SAT ratio. The number of CAMLs was correlated with maximum CXCR4 expression in CAMLs (r=0.58, p=0.004). CAMLs size and CXCR4 expression were inversely correlated. Conclusion The number and size of CAMLs are correlated with BMI, but CAMLs characteristics are not related to body composition. The number of CAMLs was associated with CXCR4, which indicated its metastatic potential. Further studies are needed to elucidate the biological role of CAMLs, especially whether the increased number and size of CAMLs in obesity reflect the tumor microenvironment. Citation Format: Toshiaki Iwase, Aaroh Parikh, Onur Sahin, Akshara S Raghavendra, Maryanne E Sapon, Anjali James, Tushaar V Shrimanker, Sudpreeda Chainitikun, Kumiko Kida, Daniel L Adams, Cha-Mei Tang, Andrea YD Medrano, Ann H Klopp, Naoto T Ueno. Prospective study of circulating cancer-associated macrophage-like cells (CAMLs) in obese patients with advanced breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS2-23.