CBM-11EXOSOMAL AND CLINICAL ANALYSIS OF EGFR AMPLIFICATION AND EGFRvIII EXPRESSION IN INDIAN GLIOMA PATIENTS

BACKGROUND: Molecular profiling of brain tumors is currently performed through tissue biopsy, which is risky, and also inaccurate due to tumor heterogeneity. It has been shown that non-invasive profiling can be performed using exosomes. Exosomes are nano shuttles harboring both RNA and DNA from the cell of origin. In this report we present an optimized clinical detection method for profiling brain tumors. We used serum exosomes to detect the presence of a tumor specific EGFRvIII, a splice variant of the Epidermal growth factor receptor (EGFR) receptor, and a target of several anti-cancer products, including Rindopepimut. METHODS: Serum and paired glioma tissue biopsies with a confirmed histopathology were collected as per approved ethics protocol. RNA was isolated using commercial kits (Invitrogen). Quantification of wild-type EGFR and EGFRvIII variant expression was performed using a semi-nested PCR with GAPDH as an internal control. Paired biopsy tissue is used as an internal control for comparison. Additionally EGFR amplification was also performed by Vysis EGFR/CEP7 FISH. We also performed overall survival analysis using Kaplan –Meier Survival curve analysis. Clinical pathology was correlated with tissue and exosomal EGFRvIII expression. Comparisons between groups were performed using student t-tests. Survival differences between groups were compared using the log-rank test. RESULTS: Tumor specific EGFRvIII was detected by PCR in 26 of 73 glioma samples and confirmed by sequencing. Exosomal EGFRvIII detection is absent in healthy controls. Distinct expression profile in exosomal EGFRvIII expression was observed among different grades of glioma. Exosomal EGFRvIII detection rate is more prominent in patients exhibiting wild-type EGFR, detected through FISH and PCR. Overall-survival is independent of EGFR wild type or EGFRvIII expression. CONCLUSION: The above data indicate that exosomes may have a utility in detecting brain tumors through simple blood test without an invasive biopsy. Further validation is needed for regular clinical use.