A highly metastatic Lewis lung carcinoma orthotopic green fluorescent protein model

The Lewis lung carcinoma has been widely used for many important studies. H owever, the subcutaneous transplant or orthotopic cell-suspension injection models have not allowed the expression of its full metastatic potential. A powerful new highly metastatic model of the widely-used Lewis lung carcino ma is reported here using surgical orthotopic implantation (SOI) of tumor f ragments and enhanced green fluorescent protein (GFP) transduction of the t umor cells. To achieve this goal, we first developed in vitro a stable high -expression GFP transductant of the Lewis lung carcinoma with the pLEIN ret roviral expression vector containing the enhanced Aequorea victoria GFP gen e. Stable high-level expression of GFP was found maintained in vivo in subc utaneously-growing Lewis lung tumors. The in vivo GFP-expressing tumors wer e harvested and implanted as tissue fragments by SOI in the right lung of a dditional nude mice. This model resulted in rapid orthotopic growth and ext ensive metastasis visualized by GFP-expression. 100% of the animals had met astases on the ipsilateral diaphragmatic surface, contralateral diaphragmat ic surface, contralateral lung parenchima, and in mediastinal lymph nodes. Heart metastases were visualized in 40%, and brain metastases were visualiz ed in 30% of the SOI animals. Mice developed signs of respiratory distress between 10-15 days post-tumor implantation and were sacrificed. The use of GFP-transduced Lewis lung carcinoma transplanted by SOI reveals for the fir st time the high malignancy of this tumor and provides an important useful model for metastasis, angiogenesis and therapeutic studies.