Nine- and twelve-membered triaza-macrocycles were appended to one end of homospermidine to make polyamine lassos. These compounds were shown to be potent polyamine transport inhibitors (PTIs) using pancreatic ductal adenocarcinoma L3.6pl cells, which have high polyamine transport activity. The smaller triazacyclononane-based lasso significantly reduced the uptake of a fluorescent polyamine probe and inhibited spermidine uptake and reduced intracellular polyamine levels in difluoromethylornithine (DFMO)-treated L3.6pl cells. Both designs were shown to be effective inhibitors of 3H-spermidine uptake, with the smaller lasso outperforming the larger lasso. When the smaller lasso was challenged to inhibit each of the three radiolabeled native polyamines, it had similar K i values as those of the known PTIs, Trimer44NMe and AMXT1501. Because of these promising properties, these materials may have future anticancer applications in polyamine blocking therapy, an approach that couples a polyamine biosynthesis inhibitor (DFMO) with a PTI to lower intracellular polyamines and suppress cell growth.
Polyamine biosynthesis is regulated by ornithine decarboxylase (ODC), which is transcriptionally activated by c-Myc. A large library was screened to find molecules that potentiate the ODC inhibitor, difluoromethylornithine (DFMO). Anthranilic acid derivatives were identified as DFMO adjunct agents. Further studies identified the far upstream binding protein 1 (FUBP1) as the target of lead compound 9. FUBP1 is a single-stranded DNA/RNA binding protein and a master controller of specific genes including c-Myc and p21. We showed that 9 does not inhibit 3 H-spermidine uptake yet works synergistically with DFMO to limit cell growth in the presence of exogenous spermidine. Compound 9 was also shown to inhibit the KH4 FUBP1−FUSE interaction in a gel shift assay, bind to FUBP1 in a ChIP assay, reduce both c-Myc mRNA and protein expression, increase p21 mRNA and protein expression, and deplete intracellular polyamines. This promising hit opens the door to new FUBP1 inhibitors with increased potency.
Of all human tissues, the human pancreas has the highest level of the polyamine spermidine. Pancreatic cancers use these high levels to drive their growth. Indeed, polyamine metabolism plays critical roles in many cellular processes including transcription, translation, and chromatin remodeling. Therefore, therapies, which deplete the intracellular pools of the native polyamines putrescine, spermidine, and spermine, result in cell growth arrest. Inhibitors have been designed to inhibit the rate limiting enzyme in polyamine biosynthesis, i.e., ornithine decarboxylase (ODC). Indeed, the ODC inhibitor difluoromethylornithine (DFMO), has a forty year history in the clinic with mixed results as an oncology therapeutic. Unfortunately, DFMO‐treated cancer cells often respond by increasing polyamine import to restore their depleted polyamine pools. Therefore, in order to establish sustained intracellular polyamine depletion, a combination therapy of DFMO and a polyamine transport inhibitor (PTI) is required.New polyamine transport inhibitors are needed because all existing PTIs are polyamine‐based and can give rise to off‐target effects. To address this need, we have developed new PTI agents predicated upon a benzoic acid scaffold. This report describes our development of these new agents and their use to inhibit the uptake of radiolabeled spermidine and block the rescue of DFMO‐treated pancreatic cancer cells by exogenous spermidine. Since pancreatic ductal adenocarcinoma (PDAC) is the most common pancreatic cancer, we have focused on this cancer type in our studies. A success here could lead to new therapies for the world's most deadly cancer, which currently has a five year survival of only 8%.Support or Funding Information2016 Florida Translational Research Program and the 2018 Bankhead‐Coley Cancer Research Program Award # 8BC05.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
Polyamines are essential growth factors for normal and malignant cells. Cells obtain polyamines via biosynthesis or transport from the extracellular environment and polyamine depletion therapy is an attractive option to inhibit the growth of cancer cells. Previous reports have indicated that depletion therapy (e.g. androgen depletion in prostate cancer) can lead to epigenetic changes resulting in resistance to the therapy and aggressive metastatic cancer. We were interested to know if polyamine depletion driven by treatment with the polyamine biosynthesis inhibitor difluoromethylornithine (DFMO) could lead to similar outcomes. The pancreatic cancer cell line Panc‐1 was passaged for 10 generations on IC50 and IC75 concentrations of DFMO, after which a decreased sensitivity to DFMO was observed. Our results indicate the need for further investigation into the mechanism of resistance to DFMO, and it's potential consequences for clinical outcomes.Support or Funding InformationUniversity of Central Florida, College of Sciences Seed AwardThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.