Ajay Gautam

Aerosol delivery of PEI–p53 complexes inhibits B16-F10 lung metastases through regulation of angiogenesis

Inhibition of pulmonary metastases poses a difficult clinical challenge for current therapeutic regimens. We have developed an aerosol system utilizing a cationic polymer, polyethyleneimine (PEI), for topical gene delivery to the lungs as a novel approach for treatment of lung cancer. Using a B16-F10 murine melanoma model in C57BL/6 mice, we previously demonstrated that aerosol delivery of PEI–p53 DNA resulted in highly significant reductions in the tumor burden (P<.001) in treated animals, and also lead to about 50% increase in the mean length of survival of the mice-bearing B16-F10 lung tumors. The mechanisms of this antitumor effect of p53 are investigated in this report. Here, we demonstrate that the p53 transfection leads to an up-regulation of the antiangiogenic factor thrombospondin-1 (TSP-1) in the lung tissue and the serum of the mice. Furthermore, there is a down-regulation of vascular endothelial growth factor (VEGF) in the lung tissue and serum of the B16-F10 tumor-bearing mice treated with PEI–p53 DNA complexes, compared with untreated tumor-bearing animals. In addition, staining for von Willebrand factor (vWF), a marker for the angiogenic blood vessels, revealed that p53 treatment leads to a decrease in the angiogenic phenotype of the B16-F10 tumors. Immunohistochemistry for transgene expression reveals that the PEI–p53 aerosol complexes transfect mainly the epithelial cells lining the airways, with diffuse transfection in the alveolar lining cells, as well as, the tumor foci in the lung tissue. There was also some evidence of apoptosis in the lung tumor foci of animals treated with p53. The data suggest that aerosol delivery of PEI–p53 complexes leads to inhibition of B16-F10 lung metastases, in part by suppression of angiogenesis.

Growth suppression of established human osteosarcoma lung metastases in mice by aerosol gene therapy with PEI-p53 complexes

Lung metastases are a frequent complication of osteosarcoma and a treatment that would reduce the severity of this complication would be of great benefit to patients. We have used a formulation consisting of polyethyleneimine (PEI) and a p53 gene administered in aerosol to treat established lung micrometastases as a model of human osteosarcoma in nude mice. The SAOS-LM6 cell line, a metastatic derivative of the p53 null SAOS-2 line, expresses high levels of p53 protein after in vitro transfection with PEI– p53 complexes as determined by ELISA, and transfection with both p53 wt and the p53 variant, p53 -CD(1–366) in vitro , results in a marked inhibition of SAOS-LM6 cell proliferation. Aerosol delivery of plasmid DNA containing either the p53 gene or a p53-CD(1–366) variant gene formulated with PEI to mice resulted in highly significant reductions in the numbers and size of tumors ( P <.001), the total number of tumor foci in the lungs ( P <.001) and the size of individual tumor nodules in treated animals compared to untreated, PEI only–treated and PEI–CAT–treated control animals. The different tissues examined did not reveal any signs of toxicity or inflammation after repeated exposure to PEI–DNA. The aerosol delivery of PEI-based formulations of p53 or synthetic p53 variant genes represents a promising new strategy for the treatment of established human osteosarcoma lung metastases. The noninvasive nature of aerosol delivery coupled with low toxicity also make this therapeutic approach potentially appropriate for combination therapy with either radio- or chemotherapy. Cancer Gene Therapy (2001) 8, 619–627.

Aerosol gene therapy

Gene therapy is a novel field of medicine that holds tremendous therapeutic potential for a variety of human diseases. Targeting of therapeutic gene delivery vectors to the lungs can be beneficial for treatment of various pulmonary diseases such as lung cancer, cystic fibrosis, pulmonary hypertension, alpha-1 antitrypsin deficiency, and asthma. Inhalation therapy using formulations delivered as aerosols targets the lungs through the pulmonary airways. The instant access and the high ratio of the drug deposited within the lungs noninvasively are the major advantages of aerosol delivery over other routes of administration. Delivery of gene formulations via aerosols is a relatively new field, which is less than a decade old. However, in this short period of time significant developments in aerosol delivery systems and vectors have resulted in major advances toward potential applications for various pulmonary diseases. This article will review these advances and the potential future applications of aerosol gene therapy technology.

Delivery Systems for Pulmonary Gene Therapy

Delivery of therapeutic genes to the lungs is an attractive strategy to correct a variety of pulmonary dysfunctions such as cystic fibrosis, alpha-1 antitrypsin deficiency, pulmonary hypertension, asthma, and lung cancer. Different delivery routes such as intratracheal instillation, aerosol and intravenous injection have been utilized with varying degrees of efficiency. Both viral and non-viral vectors, with their respective strengths and weaknesses, have achieved significant levels of transgene expression in the lungs. However, the application of gene therapy for the treatment of pulmonary disease has been handicapped by various barriers to the delivery vectors such as serum proteins during intravenous delivery, and surfactant proteins and mucus in the airway lumen during topical application of therapeutic genes. Immune and cytokine responses against the delivery vehicle are also major problems encountered in pulmonary gene therapy. Despite these shortcomings much progress has been made to enhance the efficiency, as well as lower the toxicity of gene therapy vehicles in the treatment of pulmonary disorders such as cystic fibrosis, lung cancer and asthma.