Prevention of Orthotopic Human Lung Cancer Growth by Intratracheal Instillation of a Retroviral Antisense K-ras Construct

Abstract

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 tumor growth in vivo. A 2-kilobase genomic AS-K-ras DNA fragment linked to a β-actin promoter was cloned into the LNSX retroviral vector. The recombinant construct was packaged into GP+envAm12 cells and titers greater than 10⁶ colony-forming units/ml were obtained. Irradiated (350 cGy) nu/nu mice were first inoculated intratracheally with 10⁵ H460a human large cell lung carcinoma cells which have a codon 61 mutation of the K-ras oncogene. Three days later they received intratracheal instillation of viral supernatant (5 × 10⁶ colony-forming units/ml) from either LNSX, LNSX-AS-K-ras, LNSX-sense-K-ras producer cells, or medium daily for 3 days. At autopsy, 30 days after tumor cell inoculation, 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 efficacy of the viral supernatant was dose dependent. Intratracheal administration of retroviral LNSX-AS-K-ras supernatant prevents the growth of human lung cancer cells implanted orthotopically in nu/nu mice.