Enzyme-Linked Immunosorbent Assay to Quantify Targeting Molecules on Nanoparticles

Antibody and siRNA Nanocarriers to Suppress Wnt Signaling, Tumor Growth, and Lung Metastasis in Triple-Negative Breast Cancer

The paucity of targeted therapies for triple-negative breast cancer (TNBC) causes patients with this aggressive disease to suffer a poor clinical prognosis. A promising target for therapeutic intervention is the Wnt signaling pathway, which is activated in TNBC cells when extracellular Wnt ligands bind overexpressed Frizzled7 (FZD7) transmembrane receptors. This stabilizes intracellular β-catenin proteins that in turn promote transcription of oncogenes that drive tumor growth and metastasis. To suppress Wnt signaling in TNBC cells, we developed therapeutic nanoparticles (NPs) functionalized with FZD7 antibodies and β-catenin small interfering RNAs (siRNAs). The antibodies enable TNBC cell-specific binding and inhibit Wnt signaling by locking FZD7 receptors in a ligand unresponsive state, while the siRNAs suppress β-catenin through RNA interference. Compared to NPs coated with antibodies or siRNAs individually, NPs coated with both agents more potently reduce the expression of several Wnt related genes in TNBC cells, leading to greater inhibition of cell proliferation, migration, and spheroid formation. In two murine models of metastatic TNBC, the dual antibody/siRNA nanocarriers outperformed controls in terms of inhibiting tumor growth, metastasis, and recurrence. These findings demonstrate suppressing Wnt signaling at both the receptor and mRNA levels via antibody/siRNA nanocarriers is a promising approach to combat TNBC.

E-Selectin Targeted Gold Nanoshells to Inhibit Breast Cancer Cell Binding to Lung Endothelial Cells

Extravasation of circulating tumor cells (CTCs) from the vasculature is a key step in cancer metastasis. CTCs bind to cell adhesion molecules (CAMs) expressed by endothelial cells (ECs) for flow arrest prior to extravasation. While a number of EC-expressed CAMs have been implicated in facilitating CTC binding, this work investigated the efficacy of inhibiting cancer cell binding to human lung microvascular ECs via antibody blocking of E-selectin using antibody-functionalized gold nanoshells (NS). The antibody-functionalized gold NS were synthesized using both directional and non-directional antibody conjugation techniques with variations in synthesis parameters (linker length, amount of passivating agents, and ratio of antibodies to NS) to gain a better understanding of these properties on the resultant hydrodynamic diameter, zeta potential, and antibody loading density. We quantified the ability of E-selectin antibody-functionalized NS to bind human lung microvascular endothelial cells (HMVEC-Ls) under non-inflamed and inflamed (TNF-α) conditions to inhibit binding of triple-negative MDA-MB-231s. E-selectin-targeted NS prepared using non-directional conjugation had higher antibody loading than those prepared via directional conjugation, resulting in the conjugates having similar overall binding to HMVEC-Ls at a given antibody concentration. E-selectin-targeted NS reduced MDA-MB-231 binding to HMVEC-Ls by up to 41% as determined using an in vitro binding assay. These results provide useful insights into the characteristics of antibody-functionalized NS prepared under different conditions while also demonstrating proof of concept that these conjugates hold potential to inhibit CTC binding to ECs, a critical step in extravasation during metastasis.

Dual Regulation of miR-34a and Notch Signaling in Triple-Negative Breast Cancer by Antibody/miRNA Nanocarriers

Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer that lacks expression of the three most common receptors present on other subtypes, leaving it unsusceptible to current targeted or hormonal therapies. In this study, we introduce an alternative treatment strategy for TNBC that exploits its overexpression of Notch1 receptors and its underexpression of the tumor suppressive microRNA (miRNA) miR-34a. Studies have shown that introducing mimics of miR-34a to TNBC cells effectively inhibits cancer growth, but miR-34a cannot be administered in the clinic without a carrier. To enable delivery of miR-34a to TNBC cells, we encapsulated miR-34a mimics in poly(lactic-co-glycolic acid) nanoparticles (NPs) that were functionalized with Notch1 antibodies to produce N1-34a-NPs. In addition to binding Notch1 receptors overexpressed on the surface of TNBC cells, the antibodies in this formulation enable suppression of Notch signaling through signal cascade interference. Herein, we present the results of in vitro experiments that demonstrate N1-34a-NPs can regulate Notch signaling and downstream miR-34a targets in TNBC cells to induce senescence and reduce cell proliferation and migration. These studies demonstrate that NP-mediated co-delivery of miR-34a and Notch1 antibodies is a promising alternative treatment strategy for TNBC, warranting further optimization and in vivo investigation in future studies.

Inhibition of Wnt signaling by Frizzled7 antibody-coated nanoshells sensitizes triple-negative breast cancer cells to the autophagy regulator chloroquine

Despite improvements in our understanding of the biology behind triple-negative breast cancer (TNBC), it remains a devastating disease due to lack of an effective targeted therapy. Inhibiting Wnt signaling is a promising strategy to combat TNBC because Wnt signaling drives TNBC progression, chemoresistance, and stemness. However, Wnt inhibition can lead to upregulation of autophagy, which confers therapeutic resistance. This provides an opportunity for combination therapy, as autophagy inhibitors applied concurrently with Wnt inhibitors could increase treatment efficacy. Here, we applied the autophagy inhibitor chloroquine (CQ) to TNBC cells in combination with Frizzled7 antibody-coated nanoshells (FZD7-NS) that suppress Wnt signaling by blocking Wnt ligand/FZD7 receptor interactions, and evaluated this dual treatment in vitro. We found that FZD7-NS can inhibit Axin2 and CyclinD1, two targets of canonical Wnt signaling, and increase the expression of LC3, an autophagy marker. When FZD7-NS and CQ are applied together, they reduce the expression of several stemness genes in TNBC cells, leading to inhibition of TNBC cell migration and self-renewal. Notably, co-delivery of FZD7-NS and CQ is more effective than either therapy alone or the combination of CQ with free FZD7 antibodies. This demonstrates that the nanocarrier design is important to its therapeutic utility. Overall, these findings indicate that combined regulation of Wnt signaling and autophagy by FZD7-NS and CQ is a promising strategy to combat TNBC.

Nanoparticle-Mediated Co-Delivery of Notch-1 Antibodies and ABT-737 as a Potent Treatment Strategy for Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) accounts for nearly one-quarter of all breast cancer cases, but effective targeted therapies for this disease remain elusive because TNBC cells lack expression of the three most common receptors seen on other subtypes of breast cancer. Here, we exploit TNBC cells' overexpression of Notch-1 receptors and Bcl-2 anti-apoptotic proteins to provide an effective targeted therapy. Prior studies have shown that the small molecule drug ABT-737, which inhibits Bcl-2 to reinstate apoptotic signaling, is a promising candidate for TNBC therapy. However, ABT-737 is poorly soluble in aqueous conditions, and its orally bioavailable derivative causes severe thrombocytopenia. To enable targeted delivery of ABT-737 to TNBC and enhance its therapeutic efficacy, we encapsulated the drug in poly(lactic-co-glycolic acid) nanoparticles (NPs) that were functionalized with Notch-1 antibodies to produce N1-ABT-NPs. The antibodies in this NP platform enable both TNBC cell-specific binding and suppression of Notch signaling within TNBC cells by locking the Notch-1 receptors in a ligand unresponsive state. This Notch inhibition potentiates the effect of ABT-737 by up-regulating Noxa, resulting in effective killing of TNBC cells. We present the results of in vitro studies that demonstrate N1-ABT-NPs can preferentially bind TNBC cells versus noncancerous breast epithelial cells to effectively regulate Bcl-2 and Notch signaling to induce cell death. Further, we show that N1-ABT-NPs can accumulate in subcutaneous TNBC xenograft tumors in mice following systemic administration to reduce tumor burden and extend animal survival. Together, these findings demonstrate that NP-mediated co-delivery of Notch-1 antibodies and ABT-737 is a potent treatment strategy for TNBC that may improve patient outcomes with further development and implementation.