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Published on: June 14, 2021
Exploring a repurposed candidate with dual hIDO1/hTDO2 inhibitory potential for anticancer efficacy identified
Nourhan M Aboomar1,2, Omar Essam1,2, Afnan Hassan1,2,3
1Drug Design and Discovery Lab, Zewail City of Science and Technology, Ahmed Zewail Road, October Gardens, Cairo, 12578, Giza, Egypt.
Abstract:
Discovering effective anti-cancer agents poses a formidable challenge given the limited efficacy of current therapeutic modalities against various cancer types due to intrinsic resistance mechanisms. Cancer immunochemotherapy is an alternative strategy for breast cancer treatment and overcoming cancer resistance. Human Indoleamine 2,3-dioxygenase (hIDO1) and human Tryptophan 2,3-dioxygenase 2 (hTDO2) play pivotal roles in tryptophan metabolism, leading to the generation of kynurenine and other bioactive metabolites. This process facilitates the de novo synthesis of Nicotinamide Dinucleotide (NAD), promoting cancer resistance. This study identified a new dual hIDO1/hTDO2 inhibitor using a drug repurposing strategy of FDA-approved drugs. Herein, we delineate the development of a ligand-based pharmacophore model based on a training set of 12 compounds with reported hIDO1/hTDO2 inhibitory activity. We conducted a pharmacophore search followed by high-throughput virtual screening of 2568 FDA-approved drugs against both enzymes, resulting in ten hits, four of them with high potential of dual inhibitory activity. For further in silico and in vitro biological investigation, the anti-hypercholesterolemic drug Pitavastatin deemed the drug of choice in this study. Molecular dynamics (MD) simulations demonstrated that Pitavastatin forms stable complexes with both hIDO1 and hTDO2 receptors, providing a structural basis for its potential therapeutic efficacy. At nanomolar (nM) concentration, it exhibited remarkable in vitro enzyme inhibitory activity against both examined enzymes. Additionally, Pitavastatin demonstrated potent cytotoxic activity against BT-549, MCF-7, and HepG2 cell lines (IC50 = 16.82, 9.52, and 1.84 µM, respectively). Its anticancer activity was primarily due to the induction of G1/S phase arrest as discovered through cell cycle analysis of HepG2 cancer cells. Ultimately, treating HepG2 cancer cells with Pitavastatin affected significant activation of caspase-3 accompanied by down-regulation of cellular apoptotic biomarkers such as IDO, TDO, STAT3, P21, P27, IL-6, and AhR.
Insights
This study repurposed the drug Pitavastatin as a dual inhibitor of hIDO1 and hTDO2 enzymes, crucial for cancer resistance. Pitavastatin shows potent anticancer effects by inducing cell cycle arrest and apoptosis in cancer cells.
Area of Science:
- Biochemistry
- Pharmacology
- Oncology
Background:
- Cancer resistance limits current therapies.
- Indoleamine 2,3-dioxygenase (IDO1) and Tryptophan 2,3-dioxygenase (TDO2) enzymes promote cancer resistance by altering tryptophan metabolism.
- Developing dual IDO1/TDO2 inhibitors is a promising strategy for cancer immunochemotherapy.
Purpose of the Study:
- To identify a novel dual inhibitor of human Indoleamine 2,3-dioxygenase (hIDO1) and human Tryptophan 2,3-dioxygenase 2 (hTDO2) using FDA-approved drugs.
- To evaluate the in silico and in vitro efficacy of the identified drug as an anticancer agent.
Main Methods:
- Developed a ligand-based pharmacophore model for hIDO1/hTDO2.
- Performed high-throughput virtual screening of 2568 FDA-approved drugs.
- Conducted molecular dynamics simulations and in vitro enzyme inhibition assays.
- Assessed cytotoxic activity and cell cycle effects in cancer cell lines.
Main Results:
- Identified Pitavastatin as a potent dual hIDO1/hTDO2 inhibitor.
- Pitavastatin demonstrated stable binding to both enzymes and nanomolar inhibitory activity.
- Exhibited significant cytotoxic effects against breast and liver cancer cell lines (BT-549, MCF-7, HepG2).
- Induced G1/S phase arrest and apoptosis, evidenced by caspase-3 activation and downregulation of key biomarkers.
Conclusions:
- Pitavastatin is a promising drug candidate for cancer therapy due to its dual hIDO1/hTDO2 inhibitory and anticancer properties.
- Drug repurposing offers an efficient strategy for discovering novel cancer therapeutics.
- Targeting IDO1/TDO2 pathway with Pitavastatin warrants further investigation for breast and liver cancers.
