STAT3 and metastatic neoplasm: Having previously reported a high frequency of increased STAT3 activation in RCC, especially in metastatic disease (Horiguchi et al, 2002b), we thought that STAT3 could be a novel therapeutic target for RCC and, in this study, examined whether the STAT3 inhibitor WP1066 shows antitumour activity against RCC in vitro and in vivo.