PCNA and neoplasm: Western blotting analysis showed that overexpression of JFK was accompanied by increased accumulation of the Ki-67 and Pcna proteins but reduced levels of the p53 and Ing4 proteins, findings consistent with previous studies showing that JFK targets p53 and ING4 proteins for ubiquitination and degradation (Sun et al., 2009; Yan et al., 2015; Figure 1G) and supporting the aforementioned hypothesis that JFK impacts tumor progression through its function in SCFJFK in destabilizing tumor suppressor genes.