XYLT2 and glioblastoma: In both cases, it involved the upregulation of the ERK negative feedback inhibitor loop previously described in glioblastoma [11], and also of downstream transcription factors FOS, FOSB and JUNB. In addition, SHC1, SHC2 and SHC3, encoding the adaptor proteins activating Ras in complex with Grb2 and Sos, were highly and specifically overexpressed in the M6 prolactinoma.