Multifunctional elastin-like polypeptide nanocarriers for efficient miRNA delivery in cancer therapy.

BACKGROUND: The exogenous delivery of miRNA to mimic and restore miRNA-34a activity in various cancer models holds significant promise in cancer treatment. Nevertheless, its effectiveness is often impeded by challenges, including a short half-life, propensity for off-target accumulation, susceptibility to inactivation by blood-based enzymes, concerns regarding patient safety, and the substantial cost associated with scaling up. As a means of overcoming these barriers, we propose the development of miRNA-loaded Tat-A86 nanoparticles by virtue of Tat-A86's ability to shield the loaded agent from external environmental factors, reducing degradation and inactivation, while enhancing circulation time and targeted accumulation. RESULTS: Genetically engineered Tat-A86, featuring 16 copies of the interleukin-4 receptor (IL-4R)-binding peptide (AP1), Tat for tumor penetration, and an elastin-like polypeptide (ELP) for presenting target ligands and ensuring stability, served as the basis for this delivery system. Comparative groups, including Tat-E60 and A86, were employed to discern differences in binding and penetration. The designed ELP-based nanoparticle Tat-A86 effectively condensed miRNA, forming stable nanocomplexes under physiological conditions. The miRNA/Tat-A86 formulation bound specifically to tumor cells and facilitated stable miRNA delivery into them, effectively inhibiting tumor growth. The efficacy of miRNA/Tat-A86 was further evaluated using three-dimensional spheroids of lewis lung carcinoma (LLC) as in vitro model and LLC tumor-bearing mice as an in vivo model. It was found that miRNA/Tat-A86 facilitates effective cell killing by markedly improving miRNA penetration, leading to a substantial reduction in the size of LLC spheroids. Compared to other controls, Tat-A86 demonstrated superior efficacy in suppressing the growth of 3D cellular aggregates. Moreover, at equivalent doses, miRNA-34a delivered by Tat-A86 inhibited the growth of LLC cells in allograft mice. CONCLUSIONS: Overall, these studies demonstrate that Tat-A86 nanoparticles can deliver miRNA systemically, overcoming the basic hurdles impeding miRNA delivery by facilitating both miRNA uptake and stability, ultimately leading to improved therapeutic effects.

Immune Checkpoint-Blocking Nanocages Cross the Blood-Brain Barrier and Impede Brain Tumor Growth.

Glioblastoma (GBM) is the deadliest tumor of the central nervous system, with a median survival of less than 15 months. Despite many trials, immune checkpoint-blocking (ICB) therapies using monoclonal antibodies against the PD-1/PD-L1 axis have demonstrated only limited benefits for GBM patients. Currently, the main hurdles in brain tumor therapy include limited drug delivery across the blood-brain barrier (BBB) and the profoundly immune-suppressive microenvironment of GBM. Thus, there is an urgent need for new therapeutics that can cross the BBB and target brain tumors to modulate the immune microenvironment. To this end, we developed an ICB strategy based on the BBB-permeable, 24-subunit human ferritin heavy chain, modifying the ferritin surface with 24 copies of PD-L1-blocking peptides to create ferritin-based ICB nanocages. The PD-L1pep ferritin nanocages first demonstrated their tumor-targeting and antitumor activities in an allograft colon cancer model. Next, we found that these PD-L1pep ferritin nanocages efficiently penetrated the BBB and targeted brain tumors through specific interactions with PD-L1, significantly inhibiting tumor growth in an orthotopic intracranial tumor model. The addition of PD-L1pep ferritin nanocages to triple in vitro cocultures of T cells, GBM cells, and glial cells significantly inhibited PD-1/PD-L1 interactions and restored T-cell activity. Collectively, these findings indicate that ferritin nanocages displaying PD-L1-blocking peptides can overcome the primary hurdle of brain tumor therapy and are, therefore, promising candidates for treating GBM.