New paradigms to assess consequences of long-term low-dose curcumin exposure in lung cancer cells.

Curcumin has been investigated extensively for cancer prevention, but it has been proposed that long-term treatments may promote clonal evolution and gain of cellular resistance, potentially rendering cancer cells less sensitive to future therapeutic interventions. Here, we used long-term, low-dose treatments to determine the potential for adverse effects in non-small cell lung cancer (NSCLC) cells. IC₅₀s for curcumin, cisplatin, and pemetrexed in A549, PC9, and PC9ER NSCLC cells were evaluated using growth curves. IC₅₀s were subsequently re-assessed following long-term, low-dose curcumin treatment and a three-month treatment withdrawal period, with a concurrent assessment of oncology-related protein expression. Doublet cisplatin/pemetrexed-resistant cell lines were created and the IC₅₀ for curcumin was determined. Organotypic NSCLC-fibroblast co-culture models were used to assess the effects of curcumin on invasive capacity. Following long-term treatment/treatment withdrawal, there was no significant change in IC₅₀s for the chemotherapy drugs, with chemotherapy-resistant cell lines exhibiting similar sensitivity to curcumin as their non-resistant counterparts. Curcumin (0.25–0.5 µM) was able to inhibit the invasion of both native and chemo-resistant NSCLC cells in the organotypic co-culture model. In summary, long-term curcumin treatment in models of NSCLC neither resulted in the acquisition of pro-carcinogenic phenotypes nor caused resistance to chemotherapy agents.