Computing correlations in mRNA expression between these 18 genes across all cancer samples of a given type, and combining the results in a meta-analysis over cancer types (“Materials and methods”), revealed a core cluster of positively correlated oncogenes, which included UHRF1, EZH2, TTF2, SUV39H2, PCNA, WHSC1, and RAD54L (Fig. 4b). Here, PCNA is linked to cancer.