Fig. 1

Targeting CXCR4 abrogates trastuzumab resistance. A HER2 + breast cancer cells with or without primary trastuzumab resistance were examined for CXCR4 expression with its antibody (UMB2, Abcam) using western blot analysis. The density of the bands was quantitatively analyzed. B, C Cell lines with high expression of CXCR4 (HCC1419 and HCC202) and low expression of CXCR4 (BT474 and SKBR3) were seeded in 3D Matrigel and treated with trastuzumab (B) or AMD3100 with SDF-1α (4 ng/ml). (C). The total area of the acini was quantitatively analyzed (see “Materials and methods” section). D HCC1419 cells grown in 3D Matrigel culture were treated with trastuzumab (2 µg/ml), AMD3100 (1 µM), SDF-1α (4 ng/ml), or the combination. Photographs were taken on day 13 after the start of treatment. The total area of the acini was quantitatively analyzed using AlphaView SA software (E). F–I Clonogenic assay. HCC1419 (F) and HCC202 (H) cells were seeded at low density and treated with AMD3100 (0.5 µM), SDF-1α (4 ng/ml), trastuzumab (2.5 µg/ml), or the combination. The plates were scanned on day 18 after the start of treatment. Colony formation was quantitatively analyzed using AlphaView SA software. E, G, I Data were analyzed using one-way ANOVA and are reported as mean ± SD of triplicates, representing two independent experiments (*P < 0.0001 compared with vehicle)