PREVENTION OF ORTHOTOPIC HUMAN LUNG-CANCER GROWTH BY INTRATRACHEAL INSTILLATION OF A RETROVIRAL ANTISENSE K-RAS CONSTRUCT

An orthotopic human lung cancer model in nu/nu mice was used to study the effect of an antisense K-ras (AS-K-ras) retroviral construct on tu mor growth in vivo. A 2-kilobase genomic AS-K-ras DNA fragment linked to a beta-actin promoter was cloned into the LNSX retroviral vector. T he recombinant construct was packaged into GP+envAm12 cells and titers greater than 10(6) colony-forming units/ml were obtained. Irradiated (350 cGy) nu/nu mice were first inoculated intratracheally with 10(5) H460a human large cell lung carcinoma cells which have a codon 61 muta tion of the K-ras oncogene. Three days later they received intratrache al instillation of viral supernatant (5 x 10(6) colony-forming units/m l) from either LNSX, LNSX-AS-K-ras, LNSX-sense-K-ras producer cells, o r medium daily for 3 days. At autopsy, 30 days after tumor cell inocul ation, 90% of the control mice had tumors whereas 87% of mice treated with the LNSX-AS-K-ras viral supernatant were free of tumors. The effi cacy of the viral supernatant was dose dependent. Intratracheal admini stration of retroviral LNSX-AS-K-ras supernatant prevents the growth o f human lung cancer cells implanted orthotopically in nu/nu mice.