Exosomal PTEN as a Predictive Marker of Aggressive Gliomas

Abstract

Background: Liquid biopsies have emerged as convenient alternative diagnostic methods to invasive biopsies, by evaluating disease-specific biomarkers and monitoring the disease risk noninvasively. Phosphatase and tensin homolog deleted in chromosome 10 (PTEN) is a potent tumor suppressor, and its deletion/mutations are common in gliomas. Objective: Evaluate the feasibility of non-invasive detection of PTEN and its downstream genes in serum exosomes of glioma patients. Materials and methods: PTEN, Yes-associated-protein 1 (YAP1), and lysyl oxidase (LOX) transcript expression were monitored through polymerase chain reaction (PCR) in serum exosomes and their paired tumor tissues. The impact of PTEN and its axis genes expression on the overall survival (OS) was monitored. Results: Out of the 106 glioma serum samples evaluated, PTEN was retained/lost in 65.4%/34.6% of the tumor samples while it was retained/lost in 67.1%/32.9% of their paired exosomal fractions. PTEN expression in both tissue and paired exosomal fractions was observed in 48.11% of the samples. Sanger sequencing detected three mutations (Chr10: 89720791(A>G), Chr10:89720749(C>T), and Chr10:89720850(A>G). Both PTEN-responsive downstream genes (YAP1) and LOX axis were upregulated in the PTEN-deficient samples. PTEN loss was associated with poor survival in the glioma patients (hazard ratio (HR) 0.68, confidence interval (CI): 0.35–1.31, P = 0.28). The OS of the exosomal PTEN cohort coincided with the tumor-tissue PTEN devoid group (HR 1.08, CI: 0.49–2.36, P = 0.85). While, old age yielded the worst prognosis; gender, location, and grade were not prognostic of OS in the multivariate analysis. Conclusions: PTEN and its responsive genes YAP1 and LOX can be detected in serum exosomes and can serve as essential tools for the non-invasive evaluation/identification of aggressive gliomas.