3 research outputs found
Bifunctional Elastin-like Polypeptide Nanoparticles Bind Rapamycin and Integrins and Suppress Tumor Growth in Vivo
Recombinant
protein–polymer scaffolds such as elastin-like
polypeptides (ELPs) offer drug-delivery opportunities including biocompatibility,
monodispersity, and multifunctionality. We recently reported that
the fusion of FK-506 binding protein 12 (FKBP) to an ELP nanoparticle
(FSI) increases rapamycin (Rapa) solubility, suppresses tumor growth
in breast cancer xenografts, and reduces side effects observed with
free-drug controls. This new report significantly advances this carrier
strategy by demonstrating the coassembly of two different ELP diblock
copolymers containing drug-loading and tumor-targeting domains. A
new ELP nanoparticle (ISR) was synthesized that includes the canonical
integrin-targeting ligand (Arg-Gly-Asp, RGD). FSI and ISR mixed in
a 1:1 molar ratio coassemble into bifunctional nanoparticles containing
both the FKBP domain for Rapa loading and the RGD ligand for integrin
binding. Coassembled nanoparticles were evaluated for bifunctionality
by performing in vitro cell-binding and drug-retention assays and
in vivo MDA-MB-468 breast tumor regression and tumor-accumulation
studies. The bifunctional nanoparticle demonstrated superior cell
target binding and similar drug retention to FSI; however, it enhanced
the formulation potency, such that tumor growth was suppressed at
a 3-fold lower dose compared to an untargeted FSI–Rapa control.
This data suggests that ELP-mediated scaffolds are useful tools for
generating multifunctional nanomedicines with potential activity in
cancer
Multimeric Disintegrin Protein Polymer Fusions That Target Tumor Vasculature
Recombinant protein therapeutics
have increased in number and frequency
since the introduction of human insulin, 25 years ago. Presently,
proteins and peptides are commonly used in the clinic. However, the
incorporation of peptides into clinically approved nanomedicines has
been limited. Reasons for this include the challenges of decorating
pharmaceutical-grade nanoparticles with proteins by a process that
is robust, scalable, and cost-effective. As an alternative to covalent
bioconjugation between a protein and nanoparticle, we report that
biologically active proteins may themselves mediate the formation
of small multimers through steric stabilization by large protein polymers.
Unlike multistep purification and bioconjugation, this approach is
completed during biosynthesis. As proof-of-principle, the disintegrin
protein called vicrostatin (VCN) was fused to an elastin-like polypeptide
(A192). A significant fraction of fusion proteins self-assembled into
multimers with a hydrodynamic radius of 15.9 nm. The A192-VCN fusion
proteins compete specifically for cell-surface integrins on human
umbilical vein endothelial cells (HUVECs) and two breast cancer cell
lines, MDA-MB-231 and MDA-MB-435. Confocal microscopy revealed that,
unlike linear RGD-containing protein polymers, the disintegrin fusion
protein undergoes rapid cellular internalization. To explore their
potential clinical applications, fusion proteins were characterized
using small animal positron emission tomography (microPET). Passive
tumor accumulation was observed for control protein polymers; however,
the tumor accumulation of A192-VCN was saturable, which is consistent
with integrin-mediated binding. The fusion of a protein polymer and
disintegrin results in a higher intratumoral contrast compared to
free VCN or A192 alone. Given the diversity of disintegrin proteins
with specificity for various cell-surface integrins, disintegrin fusions
are a new source of biomaterials with potential diagnostic and therapeutic
applications