PTEN and breast neoplasm: Inspection of whole cell lysates revealed increased levels of RNAPII Ser2P and Ser5P in CRISPR-PTEN HeLa cells, as well as in Pten−/− MEFs and a Pten−/− mouse breast tumor cell line (MycOE Pten Null) (52) (Figure 4A–C) when compared to PTEN WT HeLa cells.