SIX1 and Nephroblastoma: While expression of Six1 is low or absent in most adult tissues [11], it is re-expressed in a number of different human cancers including cervical [24], hepatocellular [25], ovarian [10], and breast cancer [11,26,27], as well as in alveolar rhabdomyosarcomas (RMS) [12,28], and Wilms' tumors [29].