Characteristics of membrane transport, metabolism, and target protein binding of cyclic depsipeptide destruxin E in HeLa cells.

Cyclic peptides have attracted attention as new modalities for drug development owing to their unique pharmacokinetic and pharmacodynamic properties. Destruxin E, a 19-membered cyclodepsipeptide, is a promising candidate drug for cancer therapy. The purpose of the present study was to clarify the molecular mechanisms underlying membrane transport, metabolism, and the binding for target molecules of destruxin E in human cervical carcinoma HeLa cells used as a model of cancer cells. The influx transport and the intracellular metabolism of destruxin E were non-saturable and saturable, respectively, at up to 10 μM. The intracellular amounts of destruxin E and destruxin E-diol after incubation of destruxin E with the cells significantly decreased at 4 °C compared to those at 37 °C. Destruxin E-diol, but not destruxin E, undergoes efflux transport out of cells via P-gp/MDR1/ABCB1 and BCRP/ABCG2. The epoxide hydrolase EPHX2 functions as a potent metabolizing enzyme that can convert the epoxide of destruxin E to the destruxin E-diol. Treatment with an EPHX2 inhibitor increased the intracellular destruxin E levels and enhanced the inhibitory activity of vacuolar type-H ATPase. These results suggest that epoxide hydrolase could be a regulatory factor for intracellular destruxin E levels and its pharmacological activity.