Western blotting showed that Irbp-Cyclin D1, p18Ink4c -/- tumors still expressed the p53 protein [Figure 5D], and sequencing of p53 exons 5-8 did not reveal mutations in genomic DNA from nine different Irbp-Cyclin D1, p18Ink4c -/- pineal tumors (data not shown). The gene discussed is TP53; the disease is pineal body neoplasm.