Orthotopic Transplantation of Cancer Cells into Mice Lung Using a Stereotactic Technique

Primary radiotherapy is the treatment of choice for patients with locally advanced non-small cell lung carcinoma where surgery is unable to perform. Orthotopic tumor models, where tumor material is transplanted into the corresponding organ of origin, are used in preclinical studies to predict the clinical efficacy of newly developed treatment options. For radiooncological research, orthotopic lung tumor models should have the characteristics of growing locally and spread in a manner that resembles the growth and metastasis of a real clinical situation.

In light of these respects, luciferases expressing human lung carcinoma cells (A549) were used for orthotopic transplantation. Different transplantation techniques were tested: (i) injection of small tumor pieces (< 1 mm) of subcutaneous source tumors, (ii) percutaneous injection of cell suspensions in matrigel between two ribs or (iii) stereotactic-guided injection of few microliters of cell suspensions with matrigel. Tumor development was imaged twice weekly by optical imaging using IVIS Spectrum and cone beam CT integrated in the Small-Animal Image-Guided Radiotherapy (SAIGRT) platform, developed in our institute. Tumor histology was analyzed via staining with hematoxylin and eosin and human origin of tumors were verified by a specific anti-human Ki-67 antibody. Our experiments revealed a multifocal, early metastatic spreading after percutaneous injection of cell suspensions while the transplantation of small tumor pieces lead to a defined tumor mass after quite a long period of time. In contrast, our new stereotactic approach resulted in early solitary lung lesions mimicking a clinical scenario which will allow us to start image-guided radiotherapy treatment at an appropriate time point.

In the future different lung carcinoma cell lines will be orthotopically transplanted using the stereotactic technique and corresponding growth and metastatic potential will be compared in order to improve the selection of models for preclinical radiooncological experiments.