Extended Data Fig. 4: Lama2 is predominantly expressed by astrocytes, and is stripped from vessels over the course of metastatic progression.
From: Astrocytic laminin-211 drives disseminated breast tumor cell dormancy in brain
a) Transcript expression levels for Lama2, Agrin, Col18A1, and Vcan for astrocytes, neurons, oligodendrocyte progenitor cells (OPC), newly formed oligodendrocytes, myelinating oligodendrocytes, microglia and endothelial cells, immunopanned from adult murine brains and sequenced by RNAseq. Data are reported as FPKM, and were generated by querying brainrnaseq.org. b, c) Representative Z-projections of disseminated (b) mCherry-MDA-MB-231 cells (false colored green for consistency) or (c) eGFP-T4-2 cells in brains of NOD-SCID mice ~8 weeks after intracardiac inoculation, demonstrating that stripping of (b) Laminin-α2 but not of (c) other laminins coincides with metastatic progression. Arrows indicate Ki67+ nuclei in a micrometastatic cluster. Scale bar = 20 μm for three leftmost panels and 100 μm for MACRO-Metastasis. Images representative of n = 6 sections per mouse acquired for n = 3 mice per condition. d) Representative IF staining for Laminin-α2 (left panels) and pan-laminin (right panels) to assess vessel coverage in brain-tropic MDA-MB-231-BR7-derived metastatic lesions. Scale bar = 20 µm. From left to right, images representative of n = 13, 10, 12 and 16 independent fields obtained across n = 4 mice. e) Mean fluorescent intensity of Laminin-α2 and pan-laminin within macrometastatic lesions (‘Tumour’) and lesion-adjacent regions (‘Adjacent’). ***P < 0.0001 when comparing tumour to adjacent tissue, for n = 51 total lesions across 4 mice by unpaired, two-tailed t-test. Data are presented as mean values + /− SEM.
