[PMC free article] [PubMed] [Google Scholar] (14) Billard C BH3Mimetics: Status of the Field and New Developments. 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 studies that demonstrate N1-ABT-NPs can preferentially bind TNBC cells 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. Keywords: gene regulation, drug delivery, multivalency, Notch signaling, nanocarrier, signal cascade interference, targeted cancer nanomedicine Graphical Abstract Triple-negative breast cancer (TNBC) is an aggressive disease that accounts for 15C25% of all breast cancer cases, yet it lacks effective treatment strategies.1,2 As its name implies, TNBC does not express the three most common receptors found on other subtypes of breast cancer: estrogen receptor, progesterone receptor, and human epidermal growth factor CHIR-090 receptor 2. This characteristic lack of expression leaves TNBC unsusceptible to current targeted or hormonal therapies, thus resulting in high mortality and recurrence rates.1C3 Here we exploited TNBC cells overexpression of Bcl-2 anti-apoptotic proteins and Notch-1 receptors to develop an effective targeted therapy.4C8 The p53 apoptotic pathway is activated in healthy cells KBTBD6 when they experience external stress or DNA damage.2 Upon activation, acetylated p53 migrates to the mitochondria where it induces Bax-mediated release of cytochrome c. Cytochrome c then stimulates a series of caspase activations that ultimately promote apoptosis in the cell.9 In TNBC, however, the pro-survival protein Bcl-2 is overexpressed, and this amplification is associated with poor prognosis.10,11 Bcl-2 binds to Bax, suppressing cytochrome c release from the mitochondria to prevent initiation of apoptosis9,12 (Scheme 1a). Thus, inhibiting Bcl-2 to promote apoptosis is a promising alternative strategy to combat TNBC.6 Open in a separate window Scheme 1. Depiction of How Notch Signaling and Bcl-2 Contribute to TNBC Progression and How N1-ABT-NPs Could Be Utilized to Inhibit These Pathways and Slow Tumor Growthand colorectal cancer models.16 Jin and colleagues similarly coencapsulated ABT-737 and an IRAK1/4 inhibitor in PEG-modified poly(lactic-co-glycolic CHIR-090 acid) (PLGA) NPs to synergistically treat T cell acute lymphoblastic leukemia (T-ALL).22 They demonstrated that IRAK/ABT-NPs could effectively induce an apoptotic T-ALL fraction at a concentration 2-fold lower than the free drug combination and significantly restore white blood cell numbers in the peripheral blood of a T-ALL mouse model.22 The demonstration that these two NP formulations could effectively mitigate the side effects of ABT-737 while maintaining its potency prompted us to develop a NP platform for targeted delivery of ABT-737 to TNBC. In designing this platform, we desired not only to provide targeted delivery of ABT-737 to TNBC cells but also to combat resistance to ABT-737 that is present in TNBC cells and driven by Notch signaling. Recent studies in a variety of cancers have shown that aberrant activation of Notch signaling contributes to cellular resistance to ABT-737.15,17,23 In brief, the Notch signaling pathway is activated in cancer cells when Jagged/Delta ligands on signal sending cells interact with Notch receptors on signal receiving cells. This leads to a sequence of two cleavages of the Notch transmembrane receptor by ADAM 10/17 and the and reduce tumor burden potential, absorbance, and enzyme-linked immunosorbent assay (ELISA) measurements, which demonstrated that antibodies were successfully conjugated to the surface of ABT-737-loaded NPs. Before antibody conjugation, ABT-737-loaded NPs CHIR-090 had a hydrodynamic diameter of 52.8 0.9 nm and a surface charge of ?41.3 5.6 mV, with 48 potential of 48.4 4.5 nm and ?14.4 1.2 mV, respectively. Upon conjugation of IgG or Notch-1 antibodies, the ABT-737-loaded NPs hydrodynamic diameter increased by approximately 20 nm and the potential approached neutral, indicating successful antibody attachment (Figure 1b). During antibody conjugation, about 50% of the encapsulated ABT-737.