WNK2 and neoplasm: Moreover, Lapatinib in combination with trastuzumab to HER2-overexpressing breast cancer cells SKBR3 and MCF7-HER2, inhibited mitogen-activated protein kinase (MAPK) phosphorylation and in vitro and in vivo tumor growth [16], suggesting that a mechanism of action of the combination may be clinically relevant and exploitable in the therapy of patients with HER2-positive tumors.