Co-treatment with therapeutic neural stem cells expressing carboxyl esterase and CPT-11 inhibit growth of primary and metastatic lung cancers in mice

In this study, neural stem cells (NSCs)-derived enzyme/prodrug therapy (NDEPT) was used to treat primary lung cancer or metastatic lung cancer in the brain. To confirm the anti-tumor effect of NSCs expressing carboxyl esterase (CE), A549 lung cancer cells were treated with HB1.F3.CE cells and CPT-11. A significant decrease in the viability/proliferation of lung cancer cells was observed compared to negative controls or cells treated with CPT-11 alone. To produce a mouse model of primary lung cancer or lung cancer metastasis to the brain, A549 cells were implanted in the dorsal area of the mouse or right hemisphere. CM-DiI pre-stained stem cells were implanted near the primary lung cancer tumor mass or in the contralateral brain. Two days after stem cells injection, mice were inoculated with CPT-11 (13.5 kg/mouse/day) via intraperitoneal injection. In the primary lung cancer mouse models, tumor mass was 80% lower in response to HB1.F3.CE in conjunction with CPT-11, while it was only reduced by 40% in the group treated with CPT-11 alone. Additionally, therapeutic efficacy of co-treatment with stem cells and CPT-11 was confirmed by detection of apoptosis and necrosis in primary and metastatic lung cancer tissues. By secreting VEGF, tumor cells modulate Erk1/2 and Akt signaling and migration of stem cells. This further increased tumor-selectivity of stem cell/prodrug co-therapy. Overall, these results indicate that NSCs expressing the therapeutic gene may be a powerful tool for treatment of primary lung cancer or metastasis of lung cancer to the brain.