CDKN1A and diffuse intrinsic pontine glioma: And while the overexpression of WIP1 mildly abrogates accumulation of p53Ser15 phosphorylation following UV exposure and increases the expression of p21 in MB, and knockdown sensitizes to ionizing radiation in Diffuse Intrinsic Pontine Glioma (DIPG), the level of sensitization achievable in MB is not clear (157).