ERBB2 and cancer: Then cells with nonmethylated ITGA4 alleles would produce integrin α4 protein the function of which in cancer is not yet well understood but, judging by depletion of nonmethylated ITGA4 alleles from the HER2 positive tumors, simultaneous presence of both HER2 and integrin α4 receptors is not beneficial for tumor cells (Fig. 6).