(A) The mRNA expression levels of ErbB family receptors, ErbB2, ErbB1 and ErbB3 in MMRV-ErbB2/neu mammary tumors were determined by qPCR (n=6) (B) The mRNA expression levels of ErbB ligands, EGF, HB-EGF and Nrg2 in MMTV-ErbB2/neu mammary tumors were determined by qPCR (n=6). Data is presented as mean ± S.E. Statistical significance was determined by ANOVA with Dunnett's adjustment (* p<0.05, ** p<0.01).