RHBDF1 and breast cancer: Since protein kinase C-ζ (PKCζ) is a critical component of the apicobasal polarity complex of mammary epithelial cells [21, 22], and is highly expressed in breast cancer cells in the TCGA database (P < 0.01) (Fig. 2A), we investigated RHBDF1 and PKCζ protein levels in human breast cancer tissues and cancer-adjacent normal tissues (para-cancerous tissues).