292P Androgen receptor signalling is associated with resistance to temozolomide and tumour growth in glioblastoma

Abstract

The spectrum of sex differences in glioblastoma (GBM) is a rising topic. GBM is more frequent (sex ratio M:F=1.6) and data suggests worse prognosis in males (M) compared to females. Androgen receptor (AR) is expressed in GBM but its role in GBM outcome is not yet fully understood. We have selected from our tumour tissue bank: (i) GBM samples with clinical, and molecular annotations and (ii) GBM-patient derived cell lines–GBM-PDCL-with transcriptomic profiling and available tissue from parental tumours. AR expression was investigated using multiplex IHC Opal stained-FFPE sections. Sensitivity of PDCL to hormonotherapy (dihydrotestosterone DHT or enzalutamide EZT) alone or combined with temozolomide (TMZ) was assessed using the wst-1 assay. Response to drugs was correlated to AR expression (high: log2 [FPKM] >2 or low: log2 [FPKM] <2). DHT impact on tumour growth was studied in vivo after orthotopic grafting of ARhigh PDCL in athymic nude mice. In our cohort of 1188 IDH wildtype GBM patients, the sex ratio M:F was 1.68 and the median age at diagnosis was 57 years [18-69]. Compared to males, females have better prognosis with a median overall survival of 26.1 months vs 20.8 months (p<0.0001). In multivariate analysis, male gender was an independent prognostic factor: HR of 1.43 (p<0.0001) and varied through age i.e. 1.53, 1.51 and 1.38 for males <45 years, between 46-55 years and > 55 years, respectively. In GBM patients’ tumours, AR staining was positive in 5-30% tumour cells. In vitro, after 72h exposure to 10nM DHT, ARhigh GBM-PDCLs exhibit AR nuclear translocation and c-myc expression upregulation. AR pharmacological blockade increased TMZ sensitivity in ARhigh GBM-PDCLs regardless of the patient’s sex. In vivo, in ARhigh PDCL xenografted mice, DHT continuous exposure was associated with greater tumour growth as shown by bioluminescence analysis. Our study highlights the independent prognostic significance of sex in GBM patients, where younger males (˂55 year old) exhibit a worse prognosis. In GBM-PDCL, we show that androgen receptor signalling is (i) functional in vitro, (ii) associated with resistance to temozolomide, and (iii) stimulates in vivo growth of ARhigh PDCL orthotopic graft of GBM.