ALDH1A1 and breast carcinoma: In this study, we evaluated 226 blood samples of 39 metastatic breast cancer patients during a follow-up of palliative chemo-, antibody, or hormonal therapy for the expression of ALDH1 and the EMT markers TWIST, Akt2, and PI3Kα, and correlated these findings with the presence of CTCs and the response to therapy.