Purpose: Lung cancer has a dismal prognosis and comprises 5.5% of post-transplant malignancies. We explored whether rapamycin inhibits the growth and metastatic progression of non-small cell lung cancer (NSCLC).
Experimental design: Murine KLN-205 NSCLC was used as the model tumor in syngeneic DBA/2 mice to explore the effect of rapamycin on tumor growth and metastastic progression. We also examined the effect of rapamycin on cell cycle progression, apoptosis, and proliferation using murine KLN-205 NSCLC cells and human A-549 NSCLC cells as targets. The in vivo and in vitro effects of cyclosporine and those of rapamycin plus cyclosporine were also investigated.
Results: Rapamycin but not cyclosporine inhibited tumor growth; s.c. tumor volume was 1290 +/- 173 mm(3) in untreated DBA/2 mice, 246 +/- 80 mm(3) in mice treated with rapamycin, and 1203 +/- 227 mm(3) in mice treated with cyclosporine (P < 0.001). Rapamycin but not cyclosporine prevented the formation of distant metastases; eight of eight untreated mice and four of six mice treated with cyclosporine developed pulmonary metastases whereas only one of six mice treated with rapamycin developed pulmonary metastases (P = 0.003). In vitro, rapamycin induced cell cycle arrest at the G(1) checkpoint and blocked proliferation of both KLN-205 and A-549 cells but did not induce apoptosis. Cyclosporine did not prevent cell cycle progression and had a minimal antiproliferative effect on KLN-205 and A-549 cells.
Conclusions: The immunosuppressive macrolide rapamycin but not cyclosporine prevents the growth and metastatic progression of NSCLC. A rapamycin-based immunosuppressive regimen may be of value in recipients of allografts.