ACTR2 and neoplasm: Strikingly, all three immortalised cell lines stopped cycling in response to Arp2/3 inhibition, like MCF10A cells (Fig. 7a), whereas all 6 transformed ones, i.e., the ones giving rise to tumours upon grafting, continued to cycle upon Arp2/3 inhibition, like MCF10DCIS.com cells (Fig. 7b).