1. Department of Biological Sciences, Bowling Green State University, Bowling Green, OH 43403, USA
2. Department of Public and Allied Health, Bowling Green State University, Bowling Green, OH 43403, USA
The anti-inflammatory agent curcumin can selectively eliminate malignant rather than normal cells. The present study examined the effects of curcumin on the Lewis lung carcinoma (LLC) cell line and characterized a subpopulation surviving curcumin treatments. Cell density was measured after curcumin was applied at concentrations between 10 and 60 μM for 30 hours. Because of the high cell loss at 60 μM, this dose was chosen to select for surviving cells that were then used to establish a new cell line. The resulting line had approximately 20% slower growth than the original LLC cell line and based on ELISA contained less of two markers, NF-κB and ALDH1A, used to identify more aggressive cancer cells. We also injected cells from the original and surviving lines subcutaneously into syngeneic C57BL/6 mice and monitored tumor development over three weeks and found that the curcumin surviving-line remained tumorigenic. Because curcumin has been reported to kill cancer cells more effectively when administered with light, we examined this as a possible way of enhancing the efficacy of curcumin against LLC cells. When LLC cells were exposed to curcumin and light from a fluorescent lamp source, cell loss caused by 20 μM curcumin was enhanced by about 50%, supporting a therapeutic use of curcumin in combination with white light. This study is the first to characterize a curcumin-surviving subpopulation among lung cancer cells. It shows that curcumin at a high concentration either selects for an intrinsically less aggressive cell subpopulation or generates these cells. The findings further support a role for curcumin as an adjunct to traditional chemical or radiation therapy of lung and other cancers.
Keywords: Lewis lung carcinoma, curcumin, cancer stem cell, phototoxicity.