Furthermore, it will have to be ascertained in future preclinical and clinical experiments whether the induction of apoptosis in tumours during DARPin monotherapy is rapid and potent enough in order to eliminate cells that otherwise would acquire new cancerous mutations, bearing, for example, constitutively active PI3K, and to what degree cells from heterogeneous breast tumours, harbouring preexisting mutations, would have a selective growth advantage. Here, PIK3CA is linked to breast neoplasm.