University of Sussex
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Enzastaurin inhibits ABCB1-mediated drug efflux independently of effects on protein kinase C signalling and the cellular p53 status

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posted on 2023-06-09, 03:25 authored by Matin Michaelis, Florian Rothweiler, Nadine Löschmann, Mohsen Sharifi, Taravat Ghafourian, Jindrich Cinatl Jr.
The PKCß inhibitor enzastaurin was tested in parental neuroblastoma and rhabdomyosarcoma cell lines, their vincristine-resistant sub-lines, primary neuroblastoma cells, ABCB1-transduced, ABCG2-transduced, and p53-depleted cells. Enzastaurin IC50s ranged from 3.3 to 9.5 µM in cell lines and primary cells independently of the ABCB1, ABCG2, or p53 status. Enzastaurin 0.3125 µM interfered with ABCB1-mediated drug transport. PKCa and PKCß may phosphorylate and activate ABCB1 under the control of p53. However, enzastaurin exerted similar effects on ABCB1 in the presence or absence of functional p53. Also, enzastaurin inhibited PKC signalling only in concentrations = 1.25 µM. The investigated cell lines did not express PKCß. PKCa depletion reduced PKC signalling but did not affect ABCB1 activity. Intracellular levels of the fluorescent ABCB1 substrate rhodamine 123 rapidly decreased after wash-out of extracellular enzastaurin, and enzastaurin induced ABCB1 ATPase activity resembling the ABCB1 substrate verapamil. Computational docking experiments detected a direct interaction of enzastaurin and ABCB1. These data suggest that enzastaurin directly interferes with ABCB1 function. Enzastaurin further inhibited ABCG2-mediated drug transport but by a different mechanism since it reduced ABCG2 ATPase activity. These findings are important for the further development of therapies combining enzastaurin with ABC transporter substrates.

History

Publication status

  • Published

File Version

  • Published version

Journal

Oncotarget

ISSN

1949-2553

Publisher

Impact Journals

Issue

19

Volume

6

Page range

17605-17620

Department affiliated with

  • Biochemistry Publications

Full text available

  • Yes

Peer reviewed?

  • Yes

Legacy Posted Date

2017-12-01

First Open Access (FOA) Date

2017-12-01

First Compliant Deposit (FCD) Date

2017-12-01