Mechanical Amplification of Tumor Death Using Polymeric Nanoparticles

Mechanical Amplification Of Tumor Death Using Polymeric Nanoparticles

Michael J. Mitchell¹, Robert Langer¹

¹Chemical Engineering and David H. Koch Institute for Integrative Cancer Research, MIT, Cambridge MA 02139

Introduction: Regulation of receptor-mediated phenomena at the nanoscale in a controlled manner remains a challenge for a broad range of fields, including cell biology, medicine, and bioengineering. Fluid forces play a crucial role in receptor-mediated signaling necessary for physiological function, while materials such as nanoparticles (NPs) have demonstrated potential for spatiotemporal control of cellular signaling. Here, we have developed polymeric mechanical amplifiers that tether to the cell surface and increase receptor-mediated apoptosis in the presence of physiological fluid flow.

Materials and Methods: Polymeric NPs (size: 100-1000 nm) were conjugated to free amines on tumor cells via NHS crosslinker chemistry (Fig. 1A). Nondegradable polystyrene and degradable (PLGA, PCL) NPs bound to tumor cells were assessed using flow cytometry, brightfield, and confocal fluorescence microscopy. A cone-and-plate viscometer was used to apply a fluid shear force (2.0 dyn/cm²) to tumor cell suspensions and to amplify the force exerted by polymeric particles on tumor cells (Fig.1B). Tumor cells (COLO 205, PC-3, MCF-7) were treated with 0.1 μg/mL of a TNF-related apoptosis-inducing ligand (TRAIL) to assess receptor-mediated apoptosis. In vivo mechanical amplification of TRAIL apoptosis was assessed in nu/nu mouse models of lung metastasis.

Figure 1: (A) Conjugation of polymer amplifiers to tumor cell surface via NHS crosslinker chemistry. (B) Polymeric particles amplify force exerted on the tumor cell surface under fluid forces to increase mechanotransduction and therapeutic efficacy. (C) Confocal and brightfield images of 1 μm polymeric particles conjugated to the surface of tumor cells. Scale bars: 10 μm. (D) Particle-functionalized tumor cell viability after TRAIL treatment in the presence of shear force. **P<0.01. NS: not significant. Bioluminescence imaging (E) and quantification (F) of COLO 205 tumor cell burden in mice post-injection of targeted (t)-particles followed by TRAIL. ***P<0.001.

Results and Discussion: NHS crosslinker chemistry stably bound polymeric NPs to the tumor cell surface (Fig.1C). In the presence of fluid forces, polymeric NPs increased TRAIL apoptosis (Fig.1D). Increasing the number of NPs conjugated to the tumor cell surface enhanced TRAIL apoptosis under fluid shear exposure, while the therapeutic effect under static conditions was not altered. Inhibition studies indicated the response is caspase signaling-dependent, and increased tumor death receptor expression in the presence of shear forces was also observed. Targeted anti-EPCAM polymeric NPs delivered to tumor cells in vivo mechanically amplified a subsequent treatment of soluble TRAIL, and reduced both circulating tumor cells in blood and overall tumor cell burden in vivo by over 90% (Fig. 1E,F).

Conclusions: We conclude that surface-bound polymeric nanoparticles enhance receptor-mediated apoptosis in the presence of physiological shear forces, and represents a potentially new application for a broad range of nanotechnologies to maximize the capacity of receptor-mediated signaling and function in the presence of a ligand.