As previously mentioned, PGCCs (induced in various tumour cell lines after severe anti-cancer treatments and also found in smaller quantities in the control samples), were shown to be positive for meiotic proteins (MOS, REC8, DMC1, SPO11, POU5F1, DDX4, IFITM3), as revealed in individual cells by immunofluorescence [13,27,81,104,105] and time-series qPCR analysis after genotoxic treatments, along with senescence markers [7,8,9,10,11,12,13]; [13,27,81,104,105]. The gene discussed is DDX4; the disease is cancer.