ZEB1 and breast cancer: Another study assessing EMT in CTCs intentionally used negative selection only as their method of CTC purification and observed the overexpression of at least one of the following EMT promoting transcription factors; TWIST1, SNAIL1, SLUG, zinc finger E-box-binding homeobox 1 (ZEB1) and FOXC2 in 15.4 % of breast cancer patients by qRT-PCR [104].