PCNA and neoplasm: MET was enriched in proliferating tumor cells featuring high levels of markers of cell cycle progression such as cyclins b1 and b2 (CCNB1, CCNB2), proliferating-cell nuclear antigen (PCNA) and Ki67 (MKI67) (Fig. 4c, right panel, Supplementary Table 6) and likely define yet another subset of MBM.