Improved local and systemic anti-tumor efficacy for irreversible electroporation in immunocompetent versus immunodeficient mice.

Irreversible electroporation (IRE) is a non-thermal focal ablation technique that uses a series of brief but intense electric pulses delivered into a targeted region of tissue, killing the cells by irrecoverably disrupting cellular membrane integrity. This study investigates if there is an improved local anti-tumor response in immunocompetent (IC) BALB/c versus immunodeficient (ID) nude mice, including the potential for a systemic protective effect against rechallenge. Subcutaneous murine renal carcinoma tumors were treated with an IRE pulsing protocol that used 60% of the predicted voltage required to invoke complete regressions in the ID mice. Tumors were followed for 34 days following treatment for 11 treated mice from each strain, and 7 controls from each strain. Mouse survival based on tumor burden and the progression-free disease period was substantially longer in the treated IC mice relative to the treated ID mice and sham controls for both strains. Treated IC mice were rechallenged with the same cell line 18 days after treatment, where growth of the second tumors was shown to be significantly reduced or prevented entirely. There was robust CD3+ cell infiltration in some treated BALB/C mice, with immunocytes focused at the transition between viable and dead tumor. There was no difference in the low immunocyte presence for untreated tumors, nude mice, and matrigel-only injections in both strains. These findings suggest IRE therapy may have greater therapeutic efficacy in immunocompetent patients than what has been suggested by immunodeficient models, and that IRE may invoke a systemic response beyond the targeted ablation region.

Interaction of poly(glycoamidoamine) DNA delivery vehicles with cell-surface glycosaminoglycans leads to polyplex internalization in a manner not solely dependent on charge.

Understanding the mechanisms of cellular internalization is necessary for rational design of efficient polymers for DNA delivery. In this paper, we present evidence that poly(glycoamidoamine) (PGAA)-DNA complexes (polyplexes) interact with cell-surface glycosaminoglycans (GAGs) in a manner that is not solely dependent on charge. The presence of GAGs appears to be necessary for efficient cellular uptake, as polyplex internalization was decreased in GAG-deficient CHO (pgsA-745) cells. However, uptake was nearly unaffected in cells deficient only in heparan sulfate. Internalization of PGAA polyplexes appears to be dependent on GAG sulfation in mammalian cell lines, yet the PGAA polymers are decomplexed from pDNA by high concentrations of GAGs in a charge-independent manner. This finding suggests that interactions between the carbohydrates on the polymer and GAGs may contribute to polyplex binding. Quartz crystal microbalance studies support the findings that relative PGAA polyplex-GAG binding affinities are also not completely mediated by charge. As measured by dynamic light scattering and TEM, GAGs appear to accumulate on the surface of polyplexes without disrupting them at a lower concentration, which may stimulate cellular internalization due to close interactions between the polyplexes and the GAGs. Gel electrophoresis and fluorescence measurements of an intercalating dye suggest that polyplex interaction with GAGs can induce dissociation, which could represent a potential pDNA release mechanism. These results imply that similar interactions may occur on cell surfaces, and strongly supports the hypothesis that GAGs function as cell surface receptors for polyplexes formed with PGAA vehicles.