ABCB1 limits the cytotoxic activity of TAK-243, an inhibitor of the ubiquitin-activating enzyme UBA1.

Background: One of the major concerns of cancer therapy is the emergence of multidrug resistance (MDR). The MDR-associated ATP-binding cassette sub-family B member 1 (ABCB1) transporter is established to mediate resistance against numerous anticancer drugs. In this study, we demonstrated that the Ubiquitin-like modifier activating enzyme 1 (UBA1) inhibitor TAK-243 is transported by the ABCB1.

Methods: MTT assay was performed to evaluate the cytotoxicity of TAK-243. Western blot was carried out to investigate if TAK-243 affect to ABCB1 protein expression in cancer cells. High Performance Liquid Chromatography (HPLC) and ATPase assay were carried out to confirm TAK-243 as an ABCB1 substrate. [3H]-paclitaxel accumulation assay was used to determine the MDR reversal effect of TAK-243. Computational docking analysis was performed to investigate the drug-transporter binding position.

Results: The cytotoxicity profile showed that TAK-243 was less effective in ABCB1-overexpressing cells than in the parental cells, but pharmacological inhibition or knockout the gene of ABCB1 was able to reverse TAK-243 resistance. Furthermore, TAK-243 potently stimulated ABCB1 ATPase activity and the HPLC analysis revealed that TAK-243 accumulation was significantly reduced in ABCB1-overexpressing cells. Finally, the computational docking analysis indicates a high binding affinity between TAK-243 and human ABCB1 transporter.

Conclusions: Our data characterized TAK-243 as a substrate of ABCB1, which may predict limited anticancer effect of this compound in drug resistant tumors.