GENE-22. CORRELATION BETWEEN PIK3R1MET326ILE MUTATION, CYSTEINE-RICH PROTEIN 61 EXPRESSION AND POOR PROGNOSIS IN GLIOBLASTOMA

In spite of the development of treatments, long-term survival in patients with glioblastoma is very rare. Recently, studies about clarifying prognostic markers for glioblastoma have been growing. Previously we reported that median progression-free survival and overall survival (OS) of patients with high cysteine-rich protein 61 (CCN1) expression were significantly shorter than those of patients with low CCN1 expression. To investigate the molecular mechanisms that regulate CCN1 expression, we analysed 147 tumor samples from 80 glioblastoma patients and 67 lower grade glioma patients using next-generation and Sanger sequencing. Sequencing analysis showed that CCN1 high expression group includes PIK3R1Met326Ile more frequently (10/37 cases, 27.0%) than CCN1 low expression group (3/38 cases, 7.9%) in glioblastoma. We also found this mutation in corresponding blood samples. And multivariate analysis indicated that, high CCN1 expression and PIK3R1Met326Ile in glioblastoma patients were prognostic factors for OS ([HR=2.488 (1.298–4.769), p=0.006] and [HR=2.089 (1.020–4.277), p=0.0439], respectively. According to our results, the PIK3R1Met326Ile mutation related to CCN1 expression and poor prognosis in glioblastoma.