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Identifying Inhibitors of the HBx-DDB1 Interaction Using a Split Luciferase Assay System
Published on: December 21, 2019
A cell-based high-throughput screen identifies inhibitors that overcome P-glycoprotein (Pgp)-mediated multidrug
Rida Zahra1, Muhammad Furqan1, Rahim Ullah1
1Department of Biology, Syed Babar Ali School of Science and Engineering, Lahore University of Management Sciences, Lahore, Pakistan.
Abstract:
Multidrug resistance (MDR) to chemotherapeutic drugs remains one of the major impediments to the treatment of cancer. Discovery and development of drugs that can prevent and reverse the acquisition of multidrug resistance constitute a foremost challenge in cancer therapeutics. In this work, we screened a library of 1,127 compounds with known targets for their ability to overcome Pgp-mediated multidrug resistance in cancer cell lines. We identified four compounds (CHIR-124, Elesclomol, Tyrphostin-9 and Brefeldin A) that inhibited the growth of two pairs of parental and Pgp-overexpressing multidrug-resistant cell lines with similar potency irrespective of their Pgp status. Mechanistically, CHIR-124 (a potent inhibitor of Chk1 kinase) inhibited Pgp activity in both multidrug-resistant cell lines (KB-V1 and A2780-Pac-Res) as determined through cell-based Pgp-efflux assays. Other three inhibitors on the contrary, were effective in Pgp-overexpressing resistant cells without increasing the cellular accumulation of a Pgp substrate, indicating that they overcome resistance by avoiding efflux through Pgp. None of these compounds modulated the expression of Pgp in resistant cell lines. PIK-75, a PI3 Kinase inhibitor, was also determined to inhibit Pgp activity, despite being equally potent in only one of the two pairs of resistant and parental cell lines. Strong binding of both CHIR-124 and PIK-75 to Pgp was predicted through docking studies and both compounds inhibited Pgp in a biochemical assay. The inhibition of Pgp causes accumulation of these compounds in the cells where they can modulate the function of their target proteins and thereby inhibit cell proliferation. In conclusion, we have identified compounds with various cellular targets that overcome multidrug resistance in Pgp-overexpressing cell lines through mechanisms that include Pgp inhibition and efflux evasion. These compounds, therefore, can avoid challenges associated with the co-administration of Pgp inhibitors with chemotherapeutic or targeted drugs such as additive toxicities and differing pharmacokinetic properties.
Insights
Researchers screened 1,127 compounds to overcome P-glycoprotein (Pgp)-mediated multidrug resistance in cancer. Four compounds were identified that inhibit cancer cell growth by either blocking Pgp or evading its efflux, offering new therapeutic strategies.
Area of Science:
- Oncology
- Pharmacology
- Molecular Biology
Background:
- Multidrug resistance (MDR) is a major obstacle in cancer chemotherapy.
- P-glycoprotein (Pgp) overexpression is a key mechanism driving MDR.
- Developing drugs to overcome Pgp-mediated resistance is a critical challenge.
Purpose of the Study:
- To screen a library of compounds for their ability to overcome Pgp-mediated MDR.
- To identify novel compounds that can reverse or prevent multidrug resistance in cancer cell lines.
- To elucidate the mechanisms by which identified compounds overcome Pgp-mediated resistance.
Main Methods:
- Screening of 1,127 compounds against Pgp-overexpressing cancer cell lines.
- Cell-based Pgp-efflux assays to determine Pgp activity.
- Docking studies and biochemical assays to confirm compound binding and inhibition of Pgp.
- Assessment of compound potency in parental versus resistant cell lines.
Main Results:
- Four compounds (CHIR-124, Elesclomol, Tyrphostin-9, Brefeldin A) inhibited growth of resistant cells similarly to parental cells.
- CHIR-124 directly inhibited Pgp activity.
- Elesclomol, Tyrphostin-9, and Brefeldin A overcame resistance by avoiding Pgp efflux.
- PIK-75 also inhibited Pgp activity, with strong predicted binding.
- None of the compounds altered Pgp expression levels.
Conclusions:
- Identified compounds with diverse cellular targets can overcome Pgp-mediated MDR.
- Mechanisms include direct Pgp inhibition and Pgp efflux evasion.
- These compounds may offer advantages over traditional Pgp inhibitors by avoiding co-administration toxicities and pharmacokinetic issues.
