Self-assembling protein nanocarrier for selective delivery of cytotoxic polypeptides to CXCR4^(+) head and neck squamous cell carcinoma tumors

Loco-regional recurrences and distant metastases represent the main cause of head and neck squamous cell carcinoma(HNSCC) mortality. The overexpression of chemokine receptor 4(CXCR4) in HNSCC primary tumors associates with higher risk of developing loco-regional recurrences and distant metastases, thus making CXCR4 an ideal entry pathway for targeted drug delivery. In this context, our group has generated the self-assembling protein nanocarrier T22-GFP-H6, displaying multiple T22 peptidic ligands that specifically target CXCR4. This study aimed to validate T22-GFP-H6 as a suitable nanocarrier to selectively deliver cytotoxic agents to CXCR4^(+)tumors in a HNSCC model. Here we demonstrate that T22-GFP-H6 selectively internalizes in CXCR4^(+)HNSCC cells, achieving a high accumulation in CXCR4^(+)tumors in vivo, while showing negligible nanocarrier distribution in non-tumor bearing organs. Moreover, this T22-empowered nanocarrier can incorporate bacterial toxin domains to generate therapeutic nanotoxins that induce cell death in CXCR4-overexpressing tumors in the absence of histological alterations in normal organs. Altogether, these results show the potential use of this T22-empowered nanocarrier platform to incorporate polypeptidic domains of choice to selectively eliminate CXCR4^(+)cells in HNSCC. Remarkably, to our knowledge, this is the first study testing targeted proteinonly nanoparticles in this cancer type, which may represent a novel treatment approach for HNSCC patients.

Engineering a recombinant chlorotoxin as celltargeted cytotoxic nanoparticles

Cytotoxic proteins have a wide applicability in human therapies, especially in those conditions that require efficient and selective cell killing, such as cancer. Chlorotoxin (CTX) is a small (4 kDa) basic peptide from the venom of the yellow scorpion Leiurus quinquestriatus , which blocks small-conductance chloride channels thus paralyzing the scorpion prey. Being not extremely potent as a cytotoxin (for instance when compared with ribosome-inactivating proteins), it has gained interest as a targeting agent.

The spectrum of building block conformers sustains the biophysical properties of clinically-oriented self-assembling protein nanoparticles

Histidine-rich peptides confer self-assembling properties to recombinant proteins through the supramolecular coordination with divalent cations.This fact allows the cost-effective,large-scale generation of microscopic and macroscopic protein materials with intriguing biomedical properties.Among such materials,resulting from the simple bioproduction of protein building blocks,homomeric nanoparticles are of special value as multivalent interactors and drug carriers.Interestingly,we have here identified that the assembly of a given His-tagged protein might render distinguishable categories of self-assembling protein nanoparticles.This fact has been scrutinized through the nanobody-containing fusion proteins EM1-GFP-H6 and A3C8-GFP-H6,whose biosynthesis results in two distinguishable populations of building blocks.In one of them,the assembling and disassembling is controllable by cations.However,a second population immediately self-assembles upon purification through a non-regulatable pathway,rendering larger nanoparticles with specific biological properties.The structural analyses of both model proteins and nanoparticles revealed important conformational variability in the building blocks.This fact renders different structural and functional categories of the final soft materials resulting from the participation of energetically unstable intermediates in the oligomerization process.These data illustrate the complexity of the Hismediated protein assembling in recombinant proteins but they also offer clues for a better design and refinement of protein-based nanomedicines,which,resulting from biological fabrication,show an architectonic flexibility unusual among biomaterials.