Yong S. Jong

Cytokine immunotherapy of cancer with controlled release biodegradable microspheres in a human tumor xenograft/SCID mouse model.

Abstract A novel biodegradable poly(lactic acid) microsphere formulation was evaluated for in vivo cytokine immunotherapy of cancer in a human tumor xenograft/severe combined immunodeficiency (SCID) mouse model. Co-injection of interleukin-2 (IL-2)-loaded microspheres with tumor cells into a subcutaneous site resulted in the complete suppression of tumor engraftment in 80% of animals. In contrast, bovine-serum-albumin(BSA)-loaded particles or bolus injections of poly(ethylene glycol)/IL-2 were ineffective in preventing tumor growth. The antitumor effect of IL-2 released by the microspheres was shown to be mediated by the mouse natural killer cells. This is the first evidence that the rejection of human tumor xenografts can be provoked by the sustained in vivo delivery of IL-2 from biodegradable microspheres. The use of poly(lactic acid) microspheres to deliver cytokines to the tumor environment could provide a safer and simpler alternative to gene therapy protocols in the treatment of cancer.

Controlled release of plasmid DNA

Abstract Very large molecular weight reporter plasmids (pCMV- β gal, pSV- β gal) and lower molecular weight (herring sperm) DNA were encapsulated in polyethylene vinyl co-acetate (EVAc). In vitro release studies were performed to determine release rates and duration of delivery. The swelling behavior and morphological changes of these formulations were studied to elucidate the potential mechanism of DNA release. The bioactivity of the released plasmid DNA was assessed through analysis of conformation using agarose gel electrophoresis and in vitro transfection of C 2 C 12 myoblasts using liposome (Lipofectin™) complexation. Extraction of plasmid DNA from the delivery systems indicated that the fabrication conditions did not degrade the DNA. Depending on initial DNA loading, detectable levels were released for 1–6 months. Pore formation was accompanied by swelling which varied according to DNA loading as well as the type of DNA (herring sperm, plasmid). Conformational analysis of released plasmid DNA showed DNA was released without degradation and retained the ability to transfect cells in vitro. The results demonstrate that controlled release systems can be fabricated for the release of very large molecular weight plasmid DNA which may provide an alternative approach to plasmid-based gene transfer.

In vitro and in vivo degradation of double-walled polymer microspheres

Abstract By exploiting the phenomenon of phase separation, double-walled microspheres consisting of a core of one polymer surrounded by a coating of a second polymer were formed using a modified process of solvent evaporation. This paper discusses the characterization and in vitro and in vivo degradation of these microspheres made of two biodegradable polymers with poly(lactic acid) (PLA) as the external layer and poly( 1,3-bis(p-carboxyphenoxypropane)-co-(sebacic anhydride)) 20:80 (P(CPP:SA)20:80) as the inner core. The microspheres degraded in vitro were analyzed by Fourier-transform infrared (FTIR) spectroscopy, gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and optical and scanning electron microscopy (SEM). The same methods were used to characterize the microspheres used in the in vivo study before intramuscular implantation. The tissue containing the microspheres was explanted and studied histologically by optical microscopy and SEM. The microspheres from both studies showed the same patterns of degradation, albeit at slightly different rates. The polyanhydride was hydrolyzed into oligomers first, with the PLA degrading more slowly, decreasing in molecular weight and increasing in fragility over the course of the study. The main difference between the two studies was that in vitro the inner core of degrading polyanhydride was trapped by the outer layer of PLA, even as long as 187 days while after only 72 days in vivo the polyanhydride had disappeared.

IL-12 + GM-CSF microsphere therapy induces eradication of advanced spontaneous tumors in her-2/neu transgenic mice but fails to achieve long-term cure due to the inability to maintain effector T-cell activity.

A single intratumoral injection of interleukin-12 and granulocyte-macrophage colony-stimulating factor-encapsulated microspheres induced the regression of advanced spontaneous mammary tumors, suppressed additional tumor development, and enhanced survival in her-2/neu transgenic mice. Posttherapy tumor eradication was dependent on both CD4+ and CD8+ T cells and correlated with the tumor infiltration kinetics of a transient effector T-cell response. Upon long-term monitoring, tumor regression was found to be temporary, and disease-free survival was not achieved despite the development of systemic anti-tumor cytotoxic T-cell memory and antibody responses. Repeated immunization of mice enhanced short-term tumor suppression, resulting in the complete regression of primary tumors in up to 40% of the mice, but did not improve long-term survival owing to recurrence. The failure of chronic therapy to achieve complete cure was associated with an inability to maintain the intensity of the posttherapy effector T-cell response in this model.

Novel desiccants based on designed polymeric blends

We describe a novel concept for the preparation of desiccants based on polymeric blends. A hydrophilic channeling agent (e.g., PEG) is blended with a hydrophobic polymer (e.g., polypropylene) to produce interconnecting hydrophilic channels within the hydrophobic polymer. To make the system desiccating, a water-absorbing material is blended into the polymeric matrix to become distributed within the hydrophilic portion. The resultant blend may be molded and cast into plug-type inserts and liners for closed containers, or formed into films, sheets, beads, or pellets; its uses include pharmaceutical and industrial applications.

Human inflammatory cells within the tumor microenvironment of lung tumor xenografts mediate tumor growth suppression in situ that depends on and is augmented by interleukin-12

The human tumor microenvironment includes a mixture of tumor cells, inflammatory cells, fibroblasts, and endothelial cells, all of which are tethered to an extracellular matrix. It has been difficult to study the dynamic interactions of these cells in human tumors in situ for obvious ethical and logistical considerations that prohibit experimental manipulations of tumors while still in patients. Fresh tissue from human lung tumor biopsy implanted into SCID mice was shown to remain viable, and the histologic appearance of the tumor microenvironment was maintained in the tumor xenografts for at least 3 months. In this study, the authors established that the inflammatory cells within human tumor xenografts can suppress tumor growth, and that this suppression is a result, in part, of endogenously produced interleukin-12 (IL-12) because IL-12 neutralizing antibodies enhance the growth of the tumor xenografts. The tumor-inhibitory activity of the inflammatory leukocytes is also enhanced by the local and sustained release of human recombinant IL-12 into the tumor microenvironment from cytokine-loaded biodegradable microspheres. Neither the anti–IL-12 neutralizing antibody nor the delivery of exogenous IL-12 from microspheres had any effect on tumor xenografts in the absence of the inflammatory leukocytes. In conclusion, the inflammatory cells within the tumor microenvironment of human lung tumor xenografts are functional and can suppress tumor growth, and the dynamic effects of the inflammatory cells can be modulated by exogenous cytokines.

Cytokines delivered by biodegradable microspheres promote effective suppression of human tumors by human peripheral blood lymphocytes in the SCID-winn model

A new technology for the local and sustained delivery of immunostimulatory molecules to the tumor environment for cancer immunotherapy was evaluated. The ability of cytokines delivered by biodegradable microspheres to promote the antitumor activity of human peripheral blood lymphocytes (PBL) was tested in a human PBL, human tumor, and SCID mouse (SCID–Winn) model. Co-engraftment of human recombinant IL-12–loaded microspheres with human PBL and tumors in SCID mice promoted complete tumor suppression in as many as 100% of the mice, whereas microspheres loaded with polyethyleneglycol–interleukin-2 suppressed but did not eliminate the growth of tumor xenografts. Control microspheres (loaded with bovine serum albumin) in the presence of human PBL or cytokine-loaded microspheres in the absence of human PBL had no tumor-suppressive effect. Coincident with the enhancement of the human PBL-mediated antitumor activity in mice treated with IL-12–loaded microspheres was the production and release of human IFN-&ggr; indicating that IL-12 released from the microspheres results in the activation of the engrafted human PBL. The results establish that biodegradable microspheres represent an effective tool for the local and sustained delivery of cytokines to the tumor environment for cancer immunotherapy.