Characterization of a novel curcumin analog P1 as potent inhibitor of the NF-κB signaling pathway with distinct mechanisms

Curcumin has shown promising anticancer activity, which relies on its inhibition on NF-κB pathway. In this study, we characterized the pharmacological profile of a novel curcumin analog P1 and elucidate the related mechanisms.

P1 is a novel curcumin analog with potent anticancer activities, which exerts a distinct inhibition on the NF-κB pathway.

HEK293/NF-κB cells, stably transfected with an NF-κB-responsive luciferase reporter plasmid, were generated for high-throughput screen (HTS). Eight cancer cell lines, including PC3, COLO 205, HeLa cells etc. were tested. Cell viability was assessed using the sulforhodamine B (SRB) assays. Cell apoptosis was evaluated using FACS, immunocytochemistry, and Western blotting. H2-DCFDA and MitoSOX Red were used to detect cellular and mitochondrial reactive oxygen species (ROS). The mitochondrial function was evaluated using mitochondrial oxygen consumption assay.

P1, a tropinone curcumin, was found in HTS targeting the NF-κB pathway. Its IC50 value in inhibition of TNF-α-induced NF-κB activation was 0.8 μmol/L, whereas its IC50 values in inhibiting the growth of A549 and HeLa cells were 1.24 and 0.69 μmol/L, respectively, which was 20- to 30-fold more potent than curcumin. The inhibition of P1 on the NF-κB pathway was further addressed in HeLa cells. The compound up to 10 μmol/L did not affect the binding of NF-κB to DNA, but markedly inhibited NF-κB nuclear translocation, IκB degradation and IκB kinase phosphorylation. The compound (1 and 3 μmol/L) concentration-dependently induced ROS generation, whereas curcumin up to 20 μmol/L had no effect. P1-induced ROS generation was mainly localized in mitochondria, and reversed by NAC. Moreover, the compound significantly enhanced TNF-α-induced apoptosis.