Abstract
Real-time monitoring of drug efficacy in glioblastoma multiforme (GBM) is a major clinical problem as serial re-biopsy of primary tumours is often not a clinical option. MGMT (O6-methylguanine DNA methyltransferase) and APNG (alkylpurine-DNA-N-glycosylase) are key enzymes capable of repairing temozolomide-induced DNA damages and their levels in tissue are inversely related to treatment efficacy. Yet, serial clinical analysis remains difficult, and, when done, primarily relies on promoter methylation studies of tumour biopsy material at the time of initial surgery. Here we present a microfluidic chip to analyse mRNA levels of MGMT and APNG in enriched tumour exosomes obtained from blood. We show that exosomal mRNA levels of these enzymes correlate well with levels found in parental cells and that levels change considerably during treatment of seven patients. We propose that if validated on a larger cohort of patients, the method may be used to predict drug response in GBM patients.
Highlights
Real-time monitoring of drug efficacy in glioblastoma multiforme (GBM) is a major clinical problem as serial re-biopsy of primary tumours is often not a clinical option
We examined whether GBM-derived exosomes assume similar mRNA profiles to those found in their originating cells
We examined the kinetics of methylguanine DNA methyltransferase (MGMT)/APNG mRNA changes following TMZ treatment
Summary
Real-time monitoring of drug efficacy in glioblastoma multiforme (GBM) is a major clinical problem as serial re-biopsy of primary tumours is often not a clinical option. Exosomes are membrane-bound phospholipid nanovesicles (50–200 nm in diameter) actively secreted by mammalian cells and, in particular, dividing tumour cells[7,8] They are abundant (4109 vesicles ml À 1 in serum), stable and contain unique proteins and nucleic acids reflective of their cells of origin[4,9,10]. The iMER system integrates immunomagnetic selection, RNA collection and real-time PCR into a single microfluidic chip format Using this technology, we compared the mRNA profiles of GBM-derived exosomes against those of their cells of origin and followed dynamic sequential changes on treatment initiation. We analysed clinical blood samples from patients with confirmed GBM, and showed that exosomal mRNA profiles could be correlated to treatment response, independent of the initial epigenetic status in tissue biopsy
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