ERBB2 and breast cancer: A previous study reported enhanced PKCε levels in high histologic grade and human epidermal growth factor receptor-2 (HER2/ErbB2)-positive, estrogen receptor (ER)-negative, and PR-negative breast cancers [98], whereas another study suggested that PKCε is downregulated in all cancer stages, molecular subtypes, metastatic and nonmetastatic groups, and patients with or without anticancer drug treatment compared to healthy controls [99].