SOX9 and neoplasm: Moreover, SOX9 silencing in MDA-MB-231 cells reduced the tumour formation capacity in vivo (tumour-initiating cell frequency was estimated of 1/71.7 in shC, completely abolished (1/infinite) in sh9.1 and 1/4145.5 in sh9.2; Fig. 6c; Supplementary Fig. 6b–c), in agreement with other reports12.