Biology subjects

Foley, J. R.

Publications and source records attributed to Foley, J. R..

5 recordsLinked to original sources

bioRxiv2024

Polyamine Depletion by D, L-alpha-difluoromethylornithine Inhibits Ewing Sarcoma Metastasis by Inducing Ferroptosis

AO_SCPLOWBSTRACTC_SCPLOWPolyamine metabolism and signaling play important roles in multiple cancers but have not previously been studied in Ewing sarcoma. Here, we show that blocking polyamine synthesis with D, L-alpha-difluoromethylornithine (DFMO) causes a G1 cell cycle arrest, dose-dependent decreases in sarcosphere formation from Ewing sarcoma cell lines growing in non-adherent conditions and a decrease in clonogenic growth in soft agar. Further, we utilized our orthotopic implantation/amputation model of Ewing sarcoma metastasis to demonstrate that DFMO slowed primary tumor growth in addition to limiting metastasis. RNA sequencing demonstrated gene expression patterns consistent with induction of ferroptosis caused by polyamine depletion. Induction of ferroptosis was validated in vitro by demonstrating that ferrostatin-1, an inhibitor of ferroptosis, allows sphere formation even in the presence of DFMO. Collectively, these results reveal a novel mechanism by which DFMO prevents metastasis - induction of ferroptosis due to polyamine depletion. Our results provide preclinical justification to test the ability of DFMO to prevent metastatic recurrence in Ewing sarcoma patients at high risk for relapse.

cancer biology↗

bioRxiv2023

Polyamine transport inhibition and cisplatin synergistically enhance tumor control through oxidative stress in murine head and neck cancer models

BackgroundSurgery and/or platinum-based chemoradiation remain standard of care for patients with head and neck squamous cell carcinoma (HNSCC). While these therapies are effective in a subset of patients, a substantial proportion experience recurrence or treatment resistance. As cisplatin mediates cytotoxicity through oxidative stress while polyamines play a role in redox regulation, we posited that combining cisplatin with polyamine transport inhibitor, AMXT-1501, would increase oxidative stress and tumor cell death in HNSCC cells. MethodsCell proliferation was measured in syngeneic mouse HNSCC cell lines treated with cisplatin {+/-} AMXT-1501. Synergy was determined by administering cisplatin and AMXT-1501 at a ratio of 1:10 to cancer cells in vitro. Cancer cells were transferred onto mouse flanks to test the efficacy of treatments in vivo. Reactive oxygen species (ROS) were measured. Cellular apoptosis was measured with flow cytometry using Annexin V/PI staining. High-performance liquid chromatography (HPLC) was used to quantify polyamines in cell lines. Cell viability and ROS were measured in the presence of exogenous cationic amino acids. ResultsThe combination of cisplatin and AMXT-1501 synergize in vitro on HNSCC cell lines. In vivo combination treatment resulted in tumor growth inhibition greater than either treatment individually. The combination treatment increased ROS production and induced apoptotic cell death. HPLC revealed the synergistic mechanism was independent of intracellular polyamine levels. Supplementation of cationic amino acids partially rescued cancer cell viability and reduced ROS. ConclusionAMXT-1501 enhances the cytotoxic effects of cisplatin in vitro and in vivo in aggressive HNSCC cell lines through a polyamine-independent mechanism.

cancer biology↗

bioRxiv2023

Difluoromethylornithine rebalances aberrant polyamine ratios in Snyder-Robinson syndrome: mechanism of action and therapeutic potential

Snyder-Robinson Syndrome (SRS) is caused by mutations in the spermine synthase (SMS) gene, the enzyme product of which converts the polyamine spermidine into spermine. Affecting primarily males, common manifestations of SRS include intellectual disability, osteoporosis, hypotonic musculature, and seizures, along with other, more variable symptoms. Currently, medical management focuses on treating symptoms without addressing the underlying molecular cause of the disease. Reduced SMS catalytic activity in cells of SRS patients causes the accumulation of spermidine, while spermine levels are reduced. The resulting exaggeration in spermidine-to-spermine ratio is a biochemical hallmark of SRS that tends to correlate with symptom severity in the patient. Our studies aim to pharmacologically manipulate polyamine metabolism to correct this polyamine imbalance and investigate the potential of this approach as a therapeutic strategy for affected individuals. Here we report the use of 2-difluoromethylornithine (DFMO; eflornithine), an FDA-approved inhibitor of polyamine biosynthesis, in re-establishing normal spermidine-to-spermine ratios in SRS patient cells. Through mechanistic studies, we demonstrate that, while reducing spermidine biosynthesis, DFMO also stimulates the conversion of existing spermidine into spermine in cell lines with hypomorphic variants of SMS. Further, DFMO treatment induces a compensatory uptake of exogenous polyamines, including spermine and spermine mimetics, cooperatively reducing spermidine and increasing spermine levels. In a Drosophila SRS model characterized by reduced lifespan, adding DFMO to the feed extends lifespan. As nearly all known SRS patient mutations are hypomorphic, these studies form a foundation for future translational studies with significant therapeutic potential.

biochemistry↗

bioRxiv2023

Reduction of Spermine Synthase Suppresses Tau Accumulation Through Autophagy Modulation in Tauopathy

Tauopathy, including Alzheimer Disease (AD), is characterized by Tau protein accumulation and autophagy dysregulation. Emerging evidence connects polyamine metabolism with the autophagy pathway, however the role of polyamines in Tauopathy remains unclear. In the present study we investigated the role of spermine synthase (SMS) in autophagy regulation and tau protein processing in Drosophila and human cellular models of Tauopathy. Our previous study showed that Drosophila spermine synthase (dSms) deficiency impairs lysosomal function and blocks autophagy flux. Interestingly, partial loss-of-function of SMS in heterozygous dSms flies extends lifespan and improves the climbing performance of flies with human Tau (hTau) overexpression. Mechanistic analysis showed that heterozygous loss-of-function mutation of dSms reduces hTau protein accumulation through enhancing autophagic flux. Measurement of polyamine levels detected a mild elevation of spermidine in flies with heterozygous loss of dSms. SMS knock-down in human neuronal or glial cells also upregulates autophagic flux and reduces Tau protein accumulation. Proteomics analysis of postmortem brain tissue from AD patients showed a significant albeit modest elevation of SMS protein level in AD-relevant brain regions compared to that of control brains consistently across several datasets. Taken together, our study uncovers a correlation between SMS protein level and AD pathogenesis and reveals that SMS reduction upregulates autophagy, promotes Tau clearance, and reduces Tau protein accumulation. These findings provide a new potential therapeutic target of Tauopathy.

neuroscience↗

bioRxiv2020

Inhibition of the polyamine synthesis enzyme ornithine decarboxylase sensitizes triple-negative breast cancer cells to cytotoxic chemotherapy

Treatment of triple-negative breast cancer (TNBC) is limited by a lack of effective molecular targeted therapies. Recent studies have identified metabolic alterations in cancer cells that can be targeted to improve responses to standard-of-care chemotherapy regimens. We found that exposure of TNBC cells to cytotoxic chemotherapy drugs leads to alterations in arginine and polyamine metabolites due to a reduction in the levels and activity of a rate-limiting polyamine biosynthetic enzyme ornithine decarboxylase (ODC). The reduction in ODC was mediated by its negative regulator, antizyme, targeting ODC to the proteasome for degradation. Treatment with the ODC inhibitor DFMO sensitized TNBC cells to chemotherapy, but this was not observed in receptor-positive breast cancer cells. Moreover, TNBC cell lines showed greater sensitivity to single-agent DFMO, and ODC levels were elevated in TNBC patient samples. Alterations in polyamine metabolism in response to chemotherapy, as well as preferential sensitization of TNBC cells to chemotherapy by DFMO, suggest that ODC may be a targetable metabolic vulnerability in TNBC.

cancer biology↗