PCNA and neoplasm: Analysis of cyclin A (Figure 7B, D), cyclin B (Figure 7B, E) and PCNA (an additional classical marker of proliferation, Figure 7B, F) expressions in the tumor punches (TM) from PK+/+ and PK-/- mice shows an accumulation of these proteins in PK-/- TM punches when compared to PK+/+.