Sonobiopsy for minimally invasive, spatiotemporally-controlled, and sensitive detection of glioblastoma-derived circulating tumor DNA

Abstract

Though surgical biopsies provide direct access to tissue for genomic characterization of brain cancer, they are invasive and pose significant clinical risks. Brain cancer management via blood-based liquid biopsies is a minimally invasive alternative; however, the blood-brain barrier (BBB) restricts the release of brain tumor-derived molecular biomarkers necessary for sensitive diagnosis. Methods: A mouse glioblastoma multiforme (GBM) model was used to demonstrate the capability of focused ultrasound (FUS)-enabled liquid biopsy (sonobiopsy) to improve the diagnostic sensitivity of brain tumor-specific genetic mutations compared with conventional blood-based liquid biopsy. Furthermore, a pig GBM model was developed to characterize the translational implications of sonobiopsy in humans. Magnetic resonance imaging (MRI)-guided FUS sonication was performed in mice and pigs to locally enhance the BBB permeability of the GBM tumor. Contrast-enhanced T 1 -weighted MR images were acquired to evaluate the BBB permeability change. Blood was collected immediately after FUS sonication. Droplet digital PCR was used to quantify the levels of brain tumor-specific genetic mutations in the circulating tumor DNA (ctDNA). Histological staining was performed to evaluate the potential for off-target tissue damage by sonobiopsy. Results: Sonobiopsy improved the detection sensitivity of EGFRvIII from 7.14% to 64.71% and TERT C228T from 14.29% to 45.83% in the mouse GBM model. It also improved the diagnostic sensitivity of EGFRvIII from 28.57% to 100% and TERT C228T from 42.86% to 71.43% in the porcine GBM model. Conclusion: Sonobiopsy disrupts the BBB at the spatially-targeted brain location, releases tumor-derived DNA into the blood circulation, and enables timely collection of ctDNA. Converging evidence from both mouse and pig GBM models strongly supports the clinical translation of sonobiopsy for the minimally invasive, spatiotemporally-controlled, and sensitive molecular characterization of brain cancer.

Transcranial focused ultrasound-induced blood‒brain barrier opening in mice without shaving hairs

“…1(A). This system was used in our previous MR-guided FUS-BBBO studies 10,19,20 . The system consisted of an MRIcompatible FUS transducer (Imasonics, Voray-sur-l'Ognon, France) made of a seven-element annular array with a center frequency of 1.5 MHz, an aperture of 25 mm, and a radius of curvature of 20 mm.…”

“…The axial and lateral full widths at half maximums of the FUS transducer were 5.5 mm and 1.2 mm, respectively. The acoustic pressure reported in this study was corrected for 18% mouse skull insertion loss 10,19 . A passive cavitation detection (PCD) sensor integrated at the center of the FUS transducer had a center frequency of 1.6 MHz and a 6-dB bandwidth of 754 kHz.…”

Advances in Immunotherapy for the Treatment of Adult Glioblastoma: Overcoming Chemical and Physical Barriers

“…Approaches include the passage of IL-12 [ 177 ], immune checkpoint inhibitors [ 106 , 116 , 178 , 179 , 180 , 181 ], and natural killer cells [ 182 ]. In addition to transient disruption facilitating the diffusion of therapeutics into the brain, disruption of the BBB can also enable the release of tumor biomarkers, which can assist in assessing the treatment response [ 183 ].…”

Strategies, considerations, and recent advancements in the development of liquid biopsy for glioblastoma: a step towards individualized medicine in glioblastoma

“…55 Whether this low level of plasma ctDNA is due to the BBB remains a point of controversy, as one study found that disruption of the BBB has no impact on the ability of GBM cells to shed ctDNA, 54 while other groups have shown that disruption of the BBB increases ctDNA in CSF/plasma and may increase detection specificity. 53,56 Circulating tumor DNA also possesses a half-life of less than 2 hours, necessitating rapid sample processing for analysis. 57 Despite these technical limitations, ctDNA is a potentially robust source of diagnostic and prognostic information in the setting of GBM.…”