ALDH1A1 and breast cancer: For example, upregulated genes included MKI67, a proliferation marker; ALDH1A1, a cancer stem cell marker;12 and TACC3, a gene associated with stemness and proliferation.13,14 Proliferation-related genes CCNB115 and MYBL216 were also upregulated, as was TFRC, a gene known to be overexpressed in proliferating malignant cells.17MUC1, an epithelial and breast cancer marker, was upregulated in this cluster.