PCNA and cancer: Interestingly, population B resembles cluster 3 identified in this publication, which was characterized by high expression of mesenchymal markers, including SNAI2, and low expression of proliferative genes, such as KI67, PCNA, and CCND1. Population B expresses low levels of AKT1, and AKT1low cancer cells have been reported to be quiescent cells that survive chemotherapy in breast tumors (Kabraji et al., 2017).