Fig. 8: Assessment of the trafficking patterns of intravenously infused MB-labeled macrophages in solid tumors with US.

a Schematic of the experimental protocol employed to assess MB-MΦ accumulation in 4T1 murine breast cancer with US imaging following intravenous MB-MΦ infusion. “Created in BioRender. Kim (2025) https://BioRender.com/1jad7zr”. b Representative image of the tumor vasculature using US imaging following IV MB administration (\(5.5\times {10}^{7}\) MBs). In this tumor model the vessels tended to concentrate at the tumor periphery. c Representative B-mode and AMPI US images of the tumor before the MB-MФ administration, right after and 4- and 8-h post-administration. Scale bar 2 mm. All the images collected across the tumor are shown in Supplementary Fig. 11. d, e Quantitative analysis of the B-mode and AMPI image intensity at the 4 different time points (n = 5 animals). Data are presented as mean values ± SD. p values were determined by a one-way ANOVA followed by Tukey’s multiple comparisons. *p < 0.05, **p < 0.01; n.s. not significant. f Fluorescent images showing MB-MФ (magenta) accumulation in the TME (green—cancer cells) 8 h post intravenous administration. Yellow arrow indicates extravasated MФ. Note that there is a small crosstalk between the mcherry (MB-MΦ) and CD31 staining. Scale bar 100 μm. See also Supplementary Fig. 12. g–l Data from flow cytometry across different organs (liver, spleen, lungs, and tumor) and groups (with and without US imaging). g Relative MB-MФ counts across different organs, indicating that about 12% of viable MB-MΦs (compared to the host MΦs) accumulated in the tumor 8 h post intravenous administration. (n = 3 animals). h Representative gating plots (additional data are shown in Supplementary Fig. 13). i Percentage of MB-MФs in the total live cell population collected from each organ. (n = 3 animals). Data are presented as mean values ± SD. p values were determined by a one-way ANOVA followed by Tukey’s multiple comparisons. n.s. not significant. j The viability of the MB-MФs was uniform and above 65% across all organs and groups (i.e., with and without US imaging). (n = 3 animals). Data are presented as mean values ± SD. p values were determined by a one-way ANOVA followed by Tukey’s multiple comparisons. n.s. not significant. k Microscopy images of MB-MФs collected from the disassociated tumor showing that MΦs (pink) retain the MBs (indicated by black arrows in brightfield) for at least up to 8 h. l Phenotypic analysis of MB-MΦs from different organs. Data are presented as mean values ± SD. p values were determined by a one-way ANOVA followed by Tukey’s multiple comparisons. n.s. not significant. Source data are provided as a Source Data file.