Fig. 2. BCRP is overexpressed in breast cancer cells enriched in the brain.

(A) Representative images of BCRP IHC staining and quantification of DAB OD in the tumor cells found in the PyMT#1 model in both primary tumors (n = 3 mice) and BCBM (n = 6 mice). (B) Representative images of BCRP IHC staining and quantification of DAB OD in the tumor cells found in the KB1P model in both primary tumors (n = 8 mice) and BCBM (n = 6 mice). (C) Representative images of P-gp IHC staining and quantification of DAB OD in the tumor cells found in the PyMT model in both primary tumors (n = 3 mice) and BCBM (n = 5 mice). (D) Representative images of BCRP IHC staining and quantification of DAB OD in the tumor cells found in the KB1P model in both primary tumors (n = 5 mice) and BCBM (n = 8 mice). (E to G) Representative images and quantification of DAB OD of IHC staining of BCRP in organoids derived from primary mammary tumors (left) and BCBM (right) in (E) the PyMT#1 model, (F) the KB1P model, and (G) the PyMT#2 model. For (E) to (G), n = 3 biological repeats with one technical replicate per repeat. For (A) to (G), data are presented as means ± SEM. (H) Log₂ fold change in mRNA expression of ABC transporters genes in BCBM compared to patient-matched primary tumors from the Cosgrove dataset (26). (I) Representative images of IHC staining of BCRP in cancer cells in human BCBM samples.