Figure 6.

HER2 expression is increased in bone metastases compared to matched primary tumors in luminal breast cancers. A, HER2 expression by IHC score was examined in bone metastases as compared to matched breast primary tumor in patients with luminal and HER2 amplified breast cancers (additional examples in Supplementary Figure 6). B, HER2 expression was quantitated by AQUA score of 19 matched bone metastasis and primary breast cancers. 12 of 14 (87%) luminal breast cancers (red) demonstrated significant increase in HER2 expression in bone metastasis compared to matched primary breast tumors (95% confidence interval: 57–98%). All cases of HER2 intrinsic subtype had high score except for two patients that received trastuzumab treatment (blue line falls below the clinical threshold line). Cell lines MDA-MB231 (basal/claudin-low), MCF7 (luminal) and SKBR3 (HER2 amplified) were used to determine the high and low levels of HER2. C, Fluorescence in situ hybridization (FISH) assay for HER2 amplification shows two normal copies of the HER2 gene in representative bone metastasis sample of a patient with luminal breast cancer, while bone metastasis sample from a patient with HER2-amplified primary tumor as a positive control show multiple copies of the HER2 gene.