The NIH/3T3 EGFR, NIH/3T3 HER2, NIH/3T3 EGFR/HER2 and SKOV-3 tumor xenograft models were used as calibrators for the HER quantification assays in order to convert the TR-FRET signal into the number of receptors per cell. The gene discussed is EGFR; the disease is neoplasm.