However, unlike in Irbp-Cyclin D1, p53ER(TAM)Ki/− tumor cells, the combination of 4OHT with etoposide in Irbp-Cyclin D1, p53−/− tumor cells resulted in no further effects (Fig. 4B, D, and F, compare columns 3 and 4; quantitation is shown in C, E, and G). This evidence concerns the gene TP53 and neoplasm.