In contrast to what occurs without p53 – where cell proliferation only slightly decreases from P10 to P35 and then increases as invasive tumor progresses [Figure 4C, top panel; and [13]], proliferation decreased from P10 through P49 without p18Ink4c [Figure 4C, bottom panel], but exceeded that in the Irbp-Cyclin D1 cells [Figure 4C, bottom panel, compare with Figure 1B]. Here, CCND1 is linked to neoplasm.