Figure 1. 4T1 breast cancer model with simultaneous metastasis to the brain parenchyma and the dura.

(A) The distribution of metastatic lesions 10 days after administration of Fluc-tagged 4T1 cancer cells into the external or internal carotid artery was analyzed by ex-vivo bioluminescence imaging of the brain parenchyma (brain) and the skull/dura (skull). (B) Quantification of bioluminescence signal shown in A. Int: internal; Ext: external; (C) 3D in vivo bioluminescence imaging of cancer cells 10 days after their administration into the internal carotid artery. Dorsal (left) and side view (right) are shown. The majority of cancer lesions are localized at the top of the head, suggesting predominant tumor burden at the skull/dura. (D) H&E staining of coronal head sections containing dural metastases (red arrows). (E) Verhoeff-Van Gieson staining of dural metastases. Dura mater is marked with black arrows (left image). Invasion of cancer cells into the skull is marked with red arrows (left and right image). (F and G) Distribution of cancer lesions between the skull/dura and the brain parenchyma was analyzed by ex vivo bioluminescence imaging at 16 and 45 days post-cancer cell injection into the internal carotid artery using PyMT (F) and MDA-MB-231 cancer cell lines (G), respectively. Statistical significance in B, F and G was determined using two-tailed Student's T-test with unequal variance (p ≤ 0.05); n = 4.