Xiaoqing Cheng

Characterization of cerebellum metastasis mouse model. A, Hematoxylin and eosin (H&E) and IHC stained with GFAP, HER2, and ERα antibodies in the cerebellum metastasis model of HP tumor organoid cells. Scale bars of low-power images are 5 mm. Scale bars of high-power images are 500 μm. B, H&E and IHC stained with GFAP, ERα, and HER2 antibodies in the cerebellum metastasis model of H53 tumor organoid cells. Scale bars of low-power images are 5 mm. Scale bars of high-power images are 500 μm. C, IF stained with IBA1 and TMEM119 antibodies in the cerebellum metastasis model of HP organoid cells. Scale bars of low-power images are 5 mm. Scale bars of high-power images are 500 μm. D, IF stained with IBA1 and TMEM119 antibodies in the cerebellum metastasis model of H53 tumor organoid cells. Scale bars of low-power images are 5 mm. Scale bars of high-power images are 500 μm.

Differentially Expressed Genes

Spatial gene expression in mouse BCBM.

Characterization of murine breast cancer organoids.

Effect of CSF1R blocking antibody and IL34 CRISPR knockout.

Brain metastases occur in up to 40% of patients with stage IV breast cancer, and the cerebellum is a common site for metastases in HER2-positive breast cancer. We developed a syngeneic, immunocompetent mouse model of breast cancer brain metastases (BCBM) by stereotactically injecting murine breast cancer organoids into the cerebellum. Spatial transcriptomics on these brain metastases revealed that breast cancer cells produce interleukin-34 (IL34), which induces ARG1+ macrophages at the invading edge of metastases. IL34 expression in human brain metastasis samples was measured in two independent datasets, and IL34 was expressed widely in both HER2+ and HER2− human BCBM. Remarkably, IL34-deficient breast cancer cells failed to establish tumors in the mouse cerebellum. Furthermore, treatment with a blocking antibody against the IL34 receptor, CSF1R, led to tumor shrinkage, highlighting the translational potential of these findings, as a CSF1R-blocking antibody is FDA-approved for another indication, graft-versus-host disease.Significance:Targeting IL34–CSF1R is a potential new approach to treat BCBM and could be combined with existing therapies. IL34 expression is widely found in human BCBM.

Spatial feature plot of macrophage markers and related chemokines and cytokines.

Herceptin optical imaging of brain metastases. A, Contrast-enhanced T1- and T2-weighted MRIs of stereotaxic injection at 3 weeks after transplantation of HP organoids in C57BL/6 syngeneic mice. B, Representative BLI images of the cerebellum tumor at 3 weeks after organoid cell transplantation of HER2+ tumor organoids. C, Live animal in vivo imaging of NIR fluorophore–labeled trastuzumab (NIR-trastuzumab). Mice were injected with 100 μg of NIR-trastuzumab via the tail vein 24 hours prior to this imaging. D, Left, Brightfield images of dissected cerebellum tumor at 3 weeks after transplantation. Right, Imaging of NIR-trastuzumab after dissection. E, NIR-trastuzumab imaging was performed after 24 hours of formalin fixation of mouse brain tissues. Left, Brightfield images of formalin-fixed cerebellum tumor slices. Right, Imaging of NIR-trastuzumab after formalin fixation in the same cerebellum tumor slices.

Average_Expression in clusters