Trans-(±)-Kusunokinin Binding to AKR1B1 Inhibits Oxidative Stress and Proteins Involved in Migration in Aggressive Breast Cancer

Abstract

Synthetic trans-((Formula presented.))-kusunokinin (((Formula presented.))KU), a potential anticancer substance, was revealed to have an inhibitory effect on breast cancer. According to the computational modeling prediction, AKR1B1, an oxidative stress and cancer migration protein, could be a target protein of trans-((Formula presented.))-kusunokinin. In this study, we determined the binding of ((Formula presented.))KU and AKR1B1 on triple-negative breast and non-serous ovarian cancers. We found that ((Formula presented.))KU exhibited a cytotoxic effect that was significantly stronger than zopolrestat (ZP) and epalrestat (EP) (known AKR1B1 inhibitors) on breast and ovarian cancer cells. ((Formula presented.))KU inhibited aldose reductase activity that was stronger than trans-((Formula presented.))-arctiin (((Formula presented.))AR) but weaker than ZP and EP. Interestingly, ((Formula presented.))KU stabilized AKR1B1 on SKOV3 and Hs578T cells after being heated at 60 and 75 °C, respectively. ((Formula presented.))KU decreased malondialdehyde (MDA), an oxidative stress marker, on Hs578T cells in a dose-dependent manner and the suppression was stronger than EP. Furthermore, ((Formula presented.))KU downregulated AKR1B1 and its downstream proteins, including PKC-δ, NF-κB, AKT, Nrf2, COX2, Twist2 and N-cadherin and up-regulated E-cadherin. ((Formula presented.))KU showed an inhibitory effect on AKR1B1 and its downstream proteins, similar to siRNA–AKR1B1. Interestingly, the combination of siRNA–AKR1B1 with EP or ((Formula presented.))KU showed a greater effect on the suppression of AKR1B1, N-cadherin, E-cadherin and NF-κB than single treatments. Taken together, we concluded that ((Formula presented.))KU-bound AKR1B1 leads to the attenuation of cellular oxidative stress, as well as the aggressiveness of breast cancer cell migration.