Fig. 7
Analysis of GPR158 expression in tumour and control brain samples. Expression of GPR158 in CNS, and the five glioma subgroups oligodendroglioma, astrocytoma, GBM-IDH, early GBM and GBM, as defined by the integrated (morphological and molecular) diagnosis. a TCGA RNA sequencing (rsem) data indicate highest GPR158 expression in CNS (n = 5) and oligodendrogliomas (O, n = 84), a reduction in astrocytomas (A, n = 138), GBM-IDH (n = 9), and further down-regulation in 'early GBMs' (n = 54) and GBMs (n = 148). The differences between O, A/GBM-IDH, early-GBM and GBM (both IDHwt) are highly significant. (b) GPR158 RNA expression in frozen CNS and glioma tissue from our institution. Relative GPR158 expression levels measured by RT-qPCR is consistent with TCGA rsem data. c Expression levels of miR-449a in the same samples, and (d) plot of inverse correlation of miR-449a and GPR158 RNA expression levels. e CCND1 expression is higher in gliomas than in CNS but not significantly differentially expressed across all glioma groups in TGCA samples. f in our samples, CCND1 expression is lower in GBM than in oligodendrogliomas, in keeping with the observation in our brain tumour allografts (Figs. 6t, u, v) that the proliferative Rb/p53 tumours downregulate Ccdn1. g Representative histology and immunostaining patterns in tumours (n = 93) from our institution. GPR158 immunoreactivity is strong in CNS and oligodendroglioma, much weaker in astrocytoma, and nearly negative in IDH wild-type 'early' GBM and GBM. Mutant IDH1 is expressed in oligodendrogliomas and astrocytomas, but not in CNS, and glioblastomas. ATRX is lost only in IDH mutant astrocytomas. All other tumours and the CNS maintain ATRX expression. Scale bar corresponds to 100 µm. h Quantification of protein expression by whole slide imaging and image analysis of tissue sections immunostained for GPR158. CNS tissue shows the highest expression, followed by oligodendrogliomas and astrocytomas, whilst there is a significantly lower expression in IDH wild-type early-GBM and GBM, consistent with the RNA expression data shown in (a and b). Oligodendroglioma (n = 17), astrocytoma (n = 16), early-GBM (n = 12) and GBM (n = 34). CNS tissue data were obtained from tissue fragments within some of the resection specimens containing normal CNS. i Overview and summary of demographic parameters, tumour grade, integrated diagnosis and molecular profile of the tumours analysed in (e). There are two types of IDH mutant gliomas, oligodendrogliomas, defined by a loss of chromosomal arms 1p and 19q (1p/19q codeleted) and typically with a mutation in the telomerase reverse transcriptase (TERT) promoter, and astrocytomas or glioblastomas (GBM) which carry a mutation of alpha thalassemia/mental retardation syndrome X-linked (ATRX) resulting in functional loss of the protein. Patients with IDH mutant tumours are younger than those with IDH wild-type GBM. GPR158 levels are highest in oligodendrogliomas, lower in astrocytomas and lowest in GBM, as described above
