PTCH1 and medulloblastoma: The majority of established medulloblastoma biomarkers examined (e.g. CTNNB1 in MBWNT; PTCH1/TP53/MYCN in MBSHH; MYC in MBGroup3; chr7 + /ch11- and i17q in MBGroup3/4) [14, 31, 42] were revealed as early clonal/initiating events in tumour development, consistent with their driver roles in experimental models of spontaneous tumourigenesis, where tested [13, 17, 36, 40].