2. Academic Validation
  3. ENT1 blockade by CNX-774 overcomes resistance to DHODH inhibition in pancreatic cancer

ENT1 blockade by CNX-774 overcomes resistance to DHODH inhibition in pancreatic cancer

  • Cancer Lett. 2023 Jan 1:552:215981. doi: 10.1016/j.canlet.2022.215981.
Nicholas J Mullen 1,  Ravi Thakur 2,  Surendra K Shukla 2,  Nina V Chaika 1,  Sai Sundeep Kollala 1,  Dezhen Wang 1,  Chunbo He 2,  Yuki Fujii 2,  Shikhar Sharma 2,  Scott E Mulder 1,  David B Sykes 3,  Pankaj K Singh 4
Affiliations

Affiliations

  • 1 Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE, 68198, USA.
  • 2 Department of Oncology Science, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73014, USA.
  • 3 Center for Regenerative Medicine, Massachusetts General Hospital, Boston, MA, USA; Harvard Stem Cell Institute, Cambridge, MA, 02114, USA.
  • 4 Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE, 68198, USA; Department of Oncology Science, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73014, USA; OU Health Stephenson Cancer Center, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104, USA. Electronic address: [email protected].
PMID: 36341997 DOI: 10.1016/j.canlet.2022.215981
Abstract

Inhibitors of Dihydroorotate Dehydrogenase (DHODH), a key enzyme for de novo synthesis of pyrimidine nucleotides, have failed in clinical trials for various cancers despite robust efficacy in preclinical animal models. To probe for druggable mediators of DHODH inhibitor resistance, we performed a combination screen with a small molecule library against pancreatic Cancer cell lines that are highly resistant to the DHODH inhibitor brequinar (BQ). The screen revealed that CNX-774, a preclinical Bruton tyrosine kinase (Btk) inhibitor, sensitizes resistant cell lines to BQ. Mechanistic studies showed that this effect is independent of Btk and instead results from inhibition of equilibrative nucleoside transporter 1 (ENT1) by CNX-774. We show that ENT1 mediates BQ resistance by taking up extracellular uridine, which is salvaged to generate pyrimidine nucleotides in a DHODH-independent manner. In BQ-resistant cell lines, BQ monotherapy slowed proliferation and caused modest pyrimidine nucleotide depletion, whereas combination treatment with BQ and CNX-774 led to profound cell viability loss and pyrimidine starvation. We also identify N-acetylneuraminic acid accumulation as a potential marker of the therapeutic efficacy of DHODH inhibitors. In an aggressive, immunocompetent pancreatic Cancer mouse model, combined targeting of DHODH and ENT1 dramatically suppressed tumor growth and prolonged mouse survival. Overall, our study defines CNX-774 as a previously uncharacterized ENT1 inhibitor and provides strong proof of concept support for dual targeting of DHODH and ENT1 in pancreatic Cancer.

Keywords

CNX-774; Cancer metabolism; DHODH inhibitor; Nucleoside transporter; Nucleotide metabolism; Pancreatic cancer; Therapy resistance.

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