However, we observe a significant attenuation of tyrosine kinase signalling in tumours from the bitransgenic MMTV-myr-Akt1, MMTV-c-ErbB2 animals compared with tumours from the MMTV-c-ErbB2 animals, particularly with regard to ErbB3 and Src. This evidence concerns the gene AKT1 and neoplasm.