While chronic stress increased tumour cell VEGFC expression in primary mammary tumours in vivo (Fig. 4a), direct treatment of cultured tumour cells with the β-adrenoceptor agonist isoproterenol was insufficient to drive VEGFC expression in vitro (Fig. 4f), suggesting that a mediating factor is required for the effect of stress on tumour cell VEGFC expression in vivo. The gene discussed is VEGFC; the disease is breast cancer.