M-Trap: Exosome-Based Capture of Tumor Cells as a New Technology in Peritoneal Metastasis

Remodeling targeted tissues for reception of tumor cells metastasizing from primary lesions is a consequence of communication between the tumor and the environment that governs metastasis. This study describes a novel approach that aims to disrupt the process of metastasis by interfering with this intense dialogue.

Proteomics and adhesion assays identified exosomes purified from the ascitic fluid of ovarian cancer patients (n = 9) as intermediaries of tumor cell attachment. A novel tumor cell capture device was fabricated by embedding exosomes onto a 3D scaffold (metastatic trap [M-Trap]). Murine models of ovarian metastasis (n = 3 to 34 mice per group) were used to demonstrate the efficacy of M-Trap to capture metastatic cells disseminating in the peritoneal cavity. Kaplan-Meier survival curves were used to estimate cumulative survival probabilities. All statistical tests were two-sided.

The exosome-based M-Trap device promoted tumor cell adhesion with a nonpharmacological mode of action. M-Trap served as a preferential site for metastasis formation and completely remodeled the pattern of peritoneal metastasis in clinically relevant models of ovarian cancer. Most importantly, M-Trap demonstrated a statistically significant benefit in survival outcomes, with mean survival increasing from 117.5 to 198.8 days in the presence of M-Trap; removal of the device upon tumor cell capture further improved survival to a mean of 309.4 days (P < .001).

Metastatic trap (M-Trap) design and characterization of mode of action. A) Exosomes purified from ascites of ovarian cancer patients (25 µL at 2 µg/µL) were embedded into the 3D scaffold; representative electron microscopy (TEM) of a fiber of the 3D nanomesh scaffold with adhered exosomes, in comparison with the surface of a fiber of the scaffold in the absence of exosomes (insert; scale bar = 5 μm). B) Representative electron microscopy (TEM) images showing immunogold staining of exosomes adhered to M-Trap device, revealed by TEM as vesicles containing CD9 (left panel) and CD81 (right panel) colloidal gold particles (scale bar = 500nm for both panels). C) Substrate-bound nonpharmacological mode of action of M-Trap as demonstrated by release experiments. DiD-labeled exosomes (25 µl at 2 µg/µl) were immersed in phosphate-buffered solution, and supernatants and devices (scaffold) were collected at indicated times and fluorescent imaged (in vivo image system). D) Representative fluorescent images of SKOV3 cells adhered to a fiber of the 3D scaffold in the presence (M-Trap; right panel) or not (Scaffold; left panel) of exosomes under dynamic orbital rotation conditions (scale bar = 100 μm). E) Luminometer quantification of calcein-labeled SKOV3 cells captured under dynamic conditions to bare 3D scaffolds (scaffold); bare 3D scaffolds decorated with tetraspanins CD9 (scaffold + CD9) or CD81 (scaffold + CD81); bare 3D scaffold pretreated with Poly-Hema (scaffold Poly-Hema); M-Trap device (M-Trap); M-Trap device pretreated with blocking antibodies against CD9 (M-Trap + anti-CD9); and CD81 (M-Trap + anti-CD81). Modulation of cell adhesion resulted in a gradual capacity to capture SKOV3 cells with a maximal effect by M-Trap (data are means from three independent experiments). Error bars represent standard deviation (P = .001, M-Trap versus bare scaffold, two-sided Student’s t test). SN = supernatant.

A potent artificial premetastatic niche based on exosomes is an effective approach to impair the crosstalk between metastatic cells and their environment. In the clinical setting, the capacity to modulate the pattern of dissemination represents an opportunity to control the process of metastasis. In summary, M-Trap transforms a systemic, fatal disease into a focalized disease where proven therapeutic approaches such as surgery can extend survival.