Abstract 4432: Low miR-222 expression levels predict long-term survival of patients affected by glioblastoma

Abstract

Introduction MicroRNAs (miRNAs) are small non-coding RNAs which are known to play an important role in proliferation, differentiation, invasion and angiogenesis of different malignant tumors. The role of tissue and blood level of miRNAs as useful bio-markers of gliomagenesis is also increasing. Interest is growing on tissue and plasma miR-222 level as prognostic marker in first line chemo- and radiotherapy treated patients with glioma, the mechanisms of action and the target genes of this miRNA in gliomagenesis being under extensive investigation. Furthermore, some evidence exist that miR-221 and miR-222 are upregulated in glioblastoma (GBM) patients and that these paralogues target O(6)-methylguanine-DNA methyltransferase (MGMT) mRNA. Here we focused on the prognostic role of tissue miR-222 in GBM patients. Experimental procedures 63 GBM patients were included in the analysis (overall survival (OS) range: 8-122 months). For each patient formalin-fixed paraffin-embedded tissue samples at first surgery were collected. miR-222 expression level was analyzed by qRT-PCR with TaqMan probe, normalizing miR-222 level on miR-U6 level. OS was analyzed by Kaplan-Meyer (K-M) survival curves. MGMT methylation analysis by pyrosequencing on tumoral DNA is on-going. Results In silico analysis of The Cancer Genome Atlas (TCGA) for GBM defined a median OS of 13.6 months in the whole sample population (n=199). Comparison of median OS, done stratifying two groups according to median tissue miR-222 expression level (low 222 vs high 222), showed a significant increased OS in low 222 patients (14.3 vs 13.1 months, p=0.017). Interestingly, K-M curves overlapped for the first 14 months and then diverged after. In particular, K-M analyses starting from 14 months revealed a significantly increased hazard ratio for high 222 patients (HR 1.96, 95% CI = 1.25 - 3.09, p<0.004) in respect to low 222 patients, being the median OS prolonged of further 15.1 months in low 222 and of 6.6 months in high 222 patients. On this basis, we tested the hypothesis of a possible role of miR-222 in a local sample population of 63 GBM patients with prolonged survival. MiR-222 expression level was measured as described above. Therefore, patients were stratified in two groups according to median tissue miR-222 expression level (low 222 vs high 222) and OS analysed on a K-M curve. The Hazard Ratio for high 222 patients was significantly higher (HR=5.30, 95% CI = 2.53-11.11, p<0.0001), being the median OS of 55 month in low 222 vs 30 months in high 222 GBM patients, respectively. Conclusions Quantitative analysis of miR-222 expression in the tumor tissue obtained at first surgery might provide a relevant prediction of prolonged survival in GBM patients. Further conclusions will be presented on the relationship between miR-222 and MGMT which will shed light on a possible role of miR-222 on gene methylation and GBM epigenetics. Citation Format: Laura Lattanzio, Marzia Borgognone, Rossella Merli, M. Cristina Dechecchi, Gianluigi Dorelli, Cristina Mocellini, Andrea Talacchi, Daniela Vivenza, Federica Tonissi, Alessandra Santangelo, Fabrizio Giordano, Caludio Ghimenton, Albino Eccher, Sergio Pericotti, Luisa Zanolla, Claudio Bernucci, Marco Merlano, Cristiana Lo Nigro, Giulio Cabrini. Low miR-222 expression levels predict long-term survival of patients affected by glioblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4432. doi:10.1158/1538-7445.AM2017-4432