(452d) Mixed Posh Inhibitor Micelles As a Novel Leukemia Therapeutic Modality

Acute lymphoblastic leukemia (ALL) is a neoplastic cancer associated with high-risk and poor prognosis for which few effective treatments exist.¹ Published data has shown that the protein region ‘Plenty of SH3 Domains’ (POSH) regulates lymphocyte signaling² and competition for this binding region within the cytosol by a novel peptide (POSH_inhib) leads to significant cell death in greater than 90% of T cell and B cell leukemias evaluated to date. While exciting, therapeutic peptides are notoriously difficult to discriminately deliver intracellularly to desired cell populations. Peptide amphiphile micelles are self-assembled nanomaterials which have been shown capable of trafficking in the blood and facilitating intracellular delivery.³ Additionally, DNA aptamers capable of preferentially binding cancer cells over healthy cells have been created allowing for selective cellular targeting.⁴ In specific, recent work by the investigator team has shown DNA aptamers can selectively delivering associated cargo to B cell leukemias (under review). By co-assembling POSH_inhib peptide amphiphiles with a B cell leukemia targeting aptamer within mixed micelles, a modular therapeutic nanoparticle modality has been built.

POSH_inhib peptide amphiphiles were synthesized by covalently conjugating two hydrophobic aliphatic palmitic acid tails to the hydrophilic POSH_inhib peptide. DNA amphiphiles were synthesized by a maleimide-thiol reaction with a lipid. Upon co-solubilizing the two components in water, small spherical micelles were formed and characterized. Targeting aptamer (C10.36) was associated with the micelles via annealing to the DNA amphiphile. Transmission electron micoscopy, critical micelle concentration assessment, stability determination, and Forster resonance energy transfer were utilized to confirm the nanostructure produced. Mixed micelles with the targeting aptamer outperformed micelles with control aptamers via both flow cytometry and confocal microscopy analysis in the human B cell leukemia cell line NALM6. In addition, micelles containing therapeutic POSH_inhib peptide were evaluated and showed selective toxicity to cancer cells over controls.

References:

1. Davies, S. M.; Mehta, P. A., Pediatric acute lymphoblastic leukemia: Is there still a role for transplant? Hematology, the Education Program 2010, 2010, 363-367.
2. Cunningham, C. A.; Knudson, K. M.; Peng, B. J.; Teixeiro, E.; Daniels, M. A., The POSH/JIP-1 scaffold network regulates TCR-mediated JNK1 signals and effector funciton in CD8(+) T cells. European Journal of Immunology 2013, 43, (12), 3361-3371.
3. Missirlis, D.; Khant, H.; Tirrell, M., Mechanisms of peptide amphiphile internalization by SJSA-1 cells in vitro. Biochemistry 2009, 48, (15), 3304-3314.
4. Felipe Opazo, L. E., Line Hansen, Falk Rohrbach, JesperWengel, Jørgen Kjems, and Günter Mayer, Modular Assembly of Cell-targeting Devices Based on an Uncommon G-quadruplex Aptamer. Molecular Therapy—Nucleic Acids 2015, 4, (251).