Extracellular vesicles (EVs) have emerged as a promising carrier system for the delivery of therapeutic payloads in multiple disease models, including cancer. However, effective targeting of EVs to cancerous tissue remains a challenge. Here, it is shown that nonviral transfection of myeloid-derived suppressor cells (MDSCs) can be leveraged to drive targeted release of engineered EVs that can modulate transfer and overexpression of therapeutic anticancer genes in tumor cells and tissue. MDSCs are immature immune cells that exhibit enhanced tropism toward tumor tissue and play a role in modulating tumor progression. Current MDSC research has been mostly focused on mitigating immunosuppression in the tumor niche; however, the tumor homing abilities of these cells present untapped potential to deliver EV therapeutics directly to cancerous tissue. In vivo and ex vivo studies with murine models of breast cancer show that nonviral transfection of MDSCs does not hinder their ability to home to cancerous tissue. Moreover, transfected MDSCs can release engineered EVs and mediate antitumoral responses via paracrine signaling, including decreased invasion/metastatic activity and increased apoptosis/necrosis. Altogether, these findings indicate that MDSCs can be a powerful tool for the deployment of EV-based therapeutics to tumor tissue.

Purpose: Pancreatic cancer remains an unsolved health issue, with its rapid progression and resistance to modern therapy leading to poor prognoses for most patients. The prevalence of metastasis in pancreatic cancer makes complete tumor location and removal rare, and those who do have resectable disease have only a 20% 5-year survival rate. In recent years, nanoparticles have been explored as targeted delivery agents for chemotherapeutic drugs and imaging dyes, however few have achieved clinical success due to overestimation of biological phenomena and reliance on passive targeting systems. In this work, an enzyme-responsive nanoparticle has been developed for increased active pancreatic tumor targeting and specific release at biologically-significant enzyme concentrations. Methods: Mesoporous silica nanoparticles were formed using a scaffold of hexadecyltrimethylammonium bromide (CTAB) at 80°C. The scaffold was removed to form wormhole-like pores using a series of dialysis procedures. Transmission electron microscopy (TEM) confirmed the 35 nm diameter and porous structure of the particles. The particles were then loaded with IR780 dye, and surfaces were functionalized with (3-aminopropyl) triethoxysilane (APTES). The loaded particles were then encapsulated with a combination of Type A and Type B gelatin, followed by a stabilizing polyvinylpyrrolidone (PVP) layer. Dynamic light scattering (DLS) and zeta potential were used to confirm coating. Coated particle samples were exposed to collagenase type IV (MMP-9) enzyme to test encapsulation efficiency and enzyme sensitivity. Enzyme-treated and intact samples were transferred to tissue phantoms, and Multispectral optoacoustic tomography (MSOT) was used for comparative analysis. Results: TEM confirmed the formation of stable 35 nm silica nanoparticles with a wormhole-like pore structure. Zeta potential decrease from 55 mV to 5 mV and DLS particle diameter increase from 35 nm to 334.5 nm indicated binding of gelatin and PVP to particle surfaces. MSOT imaging showed 10 X increased signals from untreated nanoparticles as compared to enzyme-treated nanoparticles, indicating that dye molecules remained inside the pores of coated particles and were released when exposed to MMP-9. Conclusion: Gelatin/PVP-coated mesoporous silica nanoparticles encapsulated dye and demonstrated MMP-9 activated dye release at biologically-relevant enzyme concentrations. Citation Format: Kylie Nairon, Abhilash Samykutty, Molly W. McNally, Girish Mishra, William E. Grizzle, Lacey R. McNally. Enzymatically-responsive tumor-targeted mesoporous silica nanoparticle for identification of pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4664.

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Current in vitro 3D models of liver tissue have been limited by the inability to study the effects of specific extracellular matrix (ECM) components on cell phenotypes. This is in part due to limitations in the availability of chemical modifications appropriate for this purpose. For example, hyaluronic acid (HA), which is a natural ECM component within the liver, lacks key ECM motifs (e.g., RGD peptides) that support cell adhesion. However, the addition of maleimide (Mal) groups to HA could facilitate the conjugation of ECM biomimetic peptides with thiol-containing end groups. In this study, we characterized a new crosslinkable hydrogel (i.e., HA-Mal) that yielded a simplified ECM-mimicking microenvironment supportive of 3D liver cell culture. We then performed a series of experiments to assess the impact of physical and biochemical signaling in the form of RGD peptide incorporation and TGF- ß supplementation, respectively, on hepatic functionality. Hepatic stellate cells (i.e., LX-2) exhibited increased cell-matrix interactions in the form of cell spreading and elongation within HA-Mal matrices containing RGD peptides, enabling physical adhesions, whereas hepatocyte-like cells (HepG2) had reduced albumin and urea production. We further exposed the encapsulated cells to soluble TGF-ß to elicit a fibrosis-like state. In the presence of TGF-ß biochemical signals, LX-2 cells became activated and HepG2 functionality significantly decreased in both RGD-containing and RGD-free hydrogels. Altogether, in this study we have developed a hydrogel biomaterial platform that allows for discrete manipulation of specific ECM motifs within the hydrogel to better understand the roles of cell-matrix interactions on cell phenotype and overall liver functionality.