Refinement of an Orthotopic Lung Cancer Model in the Nude Rat

Abstract

Abstract. Over 85% of people with lung cancer eventually succumb to this disease, largely because current chemotherapies are ineffective. The testing and validation of promising new approaches generally rely on achieving responses with cell lines in vitro or in tumor xenografts in nude mice. However, quite often the results seen with these models are not recapitulated in the clinic, thus necessitating the need for better animal models of lung cancer for preclinical testing of new therapies. One promising model is that of orthotopic lung cancer, where xenografts of human lung cancer are established in lungs of immunodeficient rodents. The problems associated with this model include poor rates of engraftment, limited tumor multiplicity, and a heightened risk for surgical trauma. The purpose of our study was to develop an efficient approach to engraftment of orthotopic tumors throughout the lungs of the Rowett nude rat. Initially, we augmented immunosuppression in the rats with whole-body X-irradiation and then used orotracheal cannulas to intratracheally instill human cancer cells from the Calu-6 cell line. This protocol produced a low rate of engraftment and low tumor multiplicity. The hypothesis that slight disruption of the pulmonary epithelium or the surfactant layer would allow better tumor engraftment was tested by coadministration of either pancreatic elastase or ethylenediaminetetraacetic acid (EDTA) along with the cell instillations. Lung tumor engraftment was evaluated 8 weeks after instillation. The inclusion of elastase or EDTA with the Calu-6 cells resulted in an 80-100% engraftment rate, respectively. Coadministration of EDTA resulted in significantly larger and greater numbers of tumors/lung than those in elastase-treated animals. Temporal studies demonstrated that small nodules were scattered throughout the lung parenchyma 5 weeks after instilling Calu-6 cells and EDTA. These nodules grew to coalesce and form large masses that effaced Ͼ75% of the parenchyma at 9 weeks postinstillation. The refinements made through our studies have led to the development of an orthotopic lung cancer model that should facilitate the evaluation of novel therapies designed to treat or impede lung cancer development.

Inhibition of lung tumor growth by complex pulmonary delivery of drugs with oligonucleotides as suppressors of cellular resistance

“…It was shown (32) that a slight disruption of the pul- monary epithelium or the surfactant layer by coadministration of either pancreatic elastase or EDTA allowed significantly better tumor engraftment. At the same time, cancer cell suspensions tolerate this concentration of EDTA, and animals subjected to EDTA at this concentration exhibit no histological pulmonary abnormalities (32). Rapid growth of lung tumor developed in 80% of the animals.…”

“…A modified orthotopic model of lung cancer originally developed for nude rats was used (32). We developed and tested a similar procedure in mice.…”

Selective Inhibition of Fatty Acid Synthase for Lung Cancer Treatment

“…We adapted previously published methods to establish orthotopic xenografts (15). Anesthetized nude mice were placed on a 45j incline in a dorsal recumbent position, and human lung cancer cells (10 6 cells from freshly harvested cultures) were instilled into the trachea with modified 22-gauge i.v.…”

Systematic Urokinase-Activated Anthrax Toxin Therapy Produces Regressions of Subcutaneous Human Non–Small Cell Lung Tumor in Athymic Nude Mice

“…Importantly, direct tumor killing rather than growth inhibition was found. Further studies will be needed to extend these findings to other NSCLC cell lines and other models, such as orthotopic lung cancer models (25).…”