Interestingly, the expression of t-DARPP has been implicated in resistance to the HER2 targeted agent, trastuzumab, in HER2 positive breast cancer cells via sustained signalling through phosphatidylinositol-4,5 bisphosphate 3-kinase (PI3K)/akt pathway and activation of PKA in vitro19–23, and in conferring a survival advantage to the HER2 targeted agent, lapatinib24. This evidence concerns the gene ERBB2 and breast cancer.