Angiotensinogen promoter methylation predicts bevacizumab treatment response of patients with recurrent glioblastoma

Abstract

Patients with recurrent glioblastoma achieving response to bevacizumab combined with chemotherapy have clinical improvement and prolonged survival. High gene expression of angiotensinogen (AGT) is associated with a poor bevacizumab response. Because AGT expression is epigenetically regulated, we aimed to investigate whether AGT promoter methylation in tumor tissue predicts response to bevacizumab combination therapy in patients with recurrent glioblastoma. The study included 159 patients with recurrent glioblastoma, treated with bevacizumab combination treatment (training cohort, n = 77; validation cohort, n = 82). All patients could be evaluated for treatment response and biomarkers. DNA methylation of 4 CpG sites in the AGT promoter was measured using pyrosequencing. A model for nonresponse was established using logistic regression analysis. In the training cohort, lower methylation of each of the four CpG sites in the AGT promoter was significantly associated with nonresponse (all P < 0.05). Moreover, the mean methylation level of all four CpG sites was associated with an increased likelihood of not achieving response to bevacizumab combination therapy (twofold decrease: odds ratio = 3.01; 95% confidence interval: 1.41-6.44; P = 0.004). We developed a model for nonresponse in the training cohort, where a threshold of mean AGT promoter methylation levels was set to below 12%. The model could predict bevacizumab nonresponse with 96% specificity. Importantly, this predictor was also significantly associated with nonresponse in the validation cohort (P = 0.037). Taken together, our findings suggest that low AGT promoter methylation in tumor tissue predicts nonresponse to bevacizumab combination treatment in patients with recurrent glioblastoma. We have, thus, established and successfully validated a predictor for nonresponse that can be used to identify patients who will not benefit from bevacizumab combination therapy.Abbreviations 95% CI, 95% confidence interval; AGT, angiotensinogen; AUC, area under the receiving operating characteristic curve; CEBP, CCAAT/ enhancer-binding protein; CR, complete response; EIAED, enzyme-inducing anti-epileptic drug; OR, odds ratio; PD, progressive disease; PR, partial response; PS, ECOG performance status; SD, stable disease; STAT3, signal transducer and activator of transcription 3; VEGF, vascular endothelial growth factor A. 964Molecular Oncology 14 (2020) 964-973 ª

Upregulation of the Renin–Angiotensin System Is Associated with Patient Survival and the Tumour Microenvironment in Glioblastoma

“…Angiotensinogen is known to be expressed within the brain and highly expressed in glioblastoma patient samples [26,44]. Furthermore, low expression or promoter methylation of AGT has been associated with better response to bevacizumab at progression [24,25], suggesting its potential role in providing an alternative pathway for angiogenesis despite inhibition of vascular endothelial growth factor (VEGF).…”

“…The expression of RAS receptors (AGTR1, AGTR2, and ATP6AP2) has been demonstrated on the glioblastoma microvasculature [20,21], and the inhibition of AGTR1 or AGTR2 reduced glioblastoma cell growth in vitro and in vivo [19,22,23]. Furthermore, low expression of AGT has been associated with a favourable response to the anti-angiogenic treatment, bevacizumab, in glioblastoma patients at progression [24,25]. This suggests a potential role for the RAS in the growth of glioblastoma cells and a potential association with the TME.…”