Evaluation of cell-line-derived xenograft tumours as controls for immunohistochemical testing for ER and PR

Quality control (QC) for immunohistochemistry (IHC) analysis routinely incorporates archived specimens for on-slide control material. We have assessed the utility of cell-line-derived xenograft (CDX) tumours for QC in breast estrogen receptor (ER) and progesterone receptor (PR) biomarker testing. Immunoblot and IHC analyses were used to select cell lines with different steady-state levels of ER and PR expression. CDX tumours all demonstrated consistent and comparable expression of ER and PR with corresponding cell lines from which they were derived. Three pathologists experienced in breast biomarker reporting scored tumours from different locations on mammary fat pads to determine reproducibility. Tumours from different locations were consistently scored as identical, and the CDX tumours representing different levels of biomarker expression were similar to patient-derived controls. Pathologists could not consistently distinguish CDX tumours from patient-derived controls, suggesting that within the appropriate quality management setting, CDX tumours may serve as control material for reporting purposes.