Fig. 3. Expression of canine c-erbB-1, c-erbB-2 (cHER2), c-erbB-3, and c-erbB-4 receptor genes in canine mammary tumor (CMT) cells. Quantitative reverse transcriptase polymerase chain reaction (QrtPCR) assays were developed to amplify discreetly each canine receptor gene to assess mRNA expression profiles of each receptor in total CMT cell RNA of cell lines CMT9, CMT12, CMT27, CMT28, CMT47, and CMT119. Agarose gel electrophoresis of semi-quantitative rtPCR for each amplicon is also shown to validate loading and as positive controls. The mRNA levels of (A) erbB-1/EGFr, (B) erbB-2/HER2, (C) erbB-3/HER3, and (D) erbB-4/HER4 are shown. Expression profiles were assayed by QrtPCR. Normalized levels calculated and significance determined as described for ER1 mRNA expression.