MTAP and Huntington disease: Due to data availability, the protein level positivity of MTAP was used as a surrogate biomarker of 9p21 loss based upon the observations that p16 does not stain well by IHC; TCGA genomics data showed that all of the MTAP-HD bladder cancers were also CDKN2A-HD (Fig. 1d, e); and HD of MTAP led to a marked decrease in its mean gene expression levels in bulk tumor tissues (Fig. 1c) which was further reflected at the protein level.