Conjugation of Diclofenac with Novel Oleanolic Acid Derivatives Modulate Nrf2 and NF-κB Activity in Hepatic Cancer Cells and Normal Hepatocytes Leading to Enhancement of Its Therapeutic and Chemopreventive Potential

Abstract

Combining NSAIDs with conventional therapeutics was recently explored as a new strategy in cancer therapy. Our earlier studies showed that novel oleanolic acid oximes (OAO) conjugated with aspirin or indomethacin may enhance their anti-cancer potential through modulation of the Nrf2 and NF-κB signaling pathways. This study focused on the synthesis and biological evaluation of four diclofenac (DCL)–OAO derivative conjugates in the context of these pathways’ modification and hepatic cells survival. Treatment with the conjugates 4d, 3-diclofenacoxyiminoolean-12-en-28-oic acid morpholide, and 4c, 3-diclofenacoxyiminoolean-12-en-28-oic acid benzyl ester significantly reduced cell viability in comparison to the DCL alone. In THLE-2, immortalized normal hepatocytes treated with these conjugates resulted in the activation of Nrf2 and increased expression in SOD-1 and NQO1, while the opposite effect was observed in the HepG2 hepatoma cells. In both cell lines, reduced activation of the NF-κB and COX-2 expression was observed. In HepG2 cells, conjugates increased ROS production resulting from a reduced antioxidant defense, induced apoptosis, and inhibited cell proliferation. In addition, the OAO morpholide derivative and its DCL hybrid reduced the tumor volume in mice bearing xenografts. In conclusion, our study demonstrated that conjugating diclofenac with the OAO morpholide and a benzyl ester might enhance its anti-cancer activity in HCC.

Cancer Chemopreventive Role of Dietary Terpenoids by Modulating Keap1-Nrf2-ARE Signaling System—A Comprehensive Update

“…In addition, this combination enhanced the p62 expression in A549 cells. Conjugation of diclofenac with OA derivatives exhibited enhanced chemopreventive activity [171]. In immortalized normal THLE-2 hepatocyte cells, the OA conjugates activated Nrf2 and enhanced SOD-1 and NQO1 expression.…”

Anti-Cancer Potential of Synthetic Oleanolic Acid Derivatives and Their Conjugates with NSAIDs

“…The formation of several bonds between the DCL-OAO derivatives conjugates and amino acids within the cavity of the C-terminal Kelch domain of the Keap1 protein was demonstrated. More detailed analysis revealed an interaction with Arg415 and Gln530 within the tested cavity as the most significant for OAO derivatives with DCL, particularly the most active morpholide derivatives [ 39 ].…”

“…OAOs themselves, particularly OAO substituted with morpholide, may be considered therapeutic agents, which may support conventional treatment strategy [ 55 ]. In contrast to OAO conjugates with ASP, OAO hybrids with indomethacin and diclofenac reduced activation and expression, not only NF-κB, but also Nrf2 in hepatoma cells, while in normal cells, increased activation of Nrf2 was still observed ( Figure 3 and Figure 4 ) [ 39 , 62 ].…”

“…OAO–IND conjugates increase the activation of Nrf2 in normal hepatocytes by 25–55%, but inhibit its activation in HCC cells (by 30–40%) [ 62 ]. Similarly, OAO–DCL conjugates enhance the activation of Nrf2 in normal hepatocytes by 22–46% and inhibit activation of Nrf2 in HCC cells by 21–55% [ 39 ]. Figure was created with BioRender.com by the authors.…”

“… OAO–NSAIDs conjugates reduce NF-κB activation and expression of COX-2 in normal hepatocytes and HCC cells. OAO–NSAIDs inhibit activation of NF-κB in normal hepatocytes and in HCC cells by ~50–60% and ~40–50%, respectively [ 35 , 39 , 62 ]. Figure was created with BioRender.com by the authors.…”