Biology subjects

Spitz, D. R.

Publications and source records attributed to Spitz, D. R..

5 recordsLinked to original sources

bioRxiv2023

Auranofin Inhibition of Thioredoxin Reductase in a Preclinical Model of Small Cell Lung Cancer

Thioredoxin Reductase (TrxR) is a key enzyme in hydroperoxide detoxification through peroxiredoxin enzymes and in thiol-mediated redox regulation of cell signaling. Because cancer cells produce increased steady-state levels of reactive oxygen species (ROS; i.e., superoxide and hydrogen peroxide), TrxR is currently being targeted in clinical trials using the anti-rheumatic drug, auranofin (AF). AF treatment decreased TrxR activity and clonogenic survival in small cell lung cancer (SCLC) cell lines (DMS273 and DMS53) as well as the lung atypical (neuroendocrine tumor) NET cell line H727. AF treatment also significantly sensitized DMS273 and H727 cell lines in vitro to sorafenib, a multi-kinase inhibitor that was shown to decrease intracellular glutathione. The pharmacokinetic and pharmacodynamic properties of AF treatment in a mouse SCLC xenograft model was examined to maximize inhibition of TrxR activity without causing toxicity. AF was administered intraperitoneally at 2 mg/kg or 4 mg/kg (IP) once (QD) or twice daily (BID) for 1 to 5 days in mice with DMS273 xenografts. Plasma levels of AF were 10-20 M (determined by mass spectrometry of gold) and the optimal inhibition of TrxR (50 %) was obtained at 4 mg/kg once daily, with no effect on glutathione peroxidase 1 activity. When this daily AF treatment was extended for 14 days a significant prolongation of median survival from 19 to 23 days (p=0.04, N=30 controls, 28 AF) was observed without causing changes in animal bodyweight, CBCs, bone marrow toxicity, blood urea nitrogen, or creatinine. These results show that AF is an effective inhibitor of TrxR both in vitro and in vivo in SCLC, capable of sensitizing NETs and SCLC to sorafenib, and supports the hypothesis that AF could be used as an adjuvant therapy with agents known to induce disruptions in thiol metabolism to enhance therapeutic efficacy.

cancer biology↗

bioRxiv2023

Inhibition of serotonin biosynthesis in neuroendocrine neoplasm suppressestumor growth in vivo

Small bowel neuroendocrine tumors (SBNETs) originate from enterochromaffin cells in the intestine which synthesize and secrete serotonin. SBNETs express high levels of tryptophan hydroxylase 1 (Tph1), a key enzyme in serotonin biosynthesis. Patients with high serotonin level may develop carcinoid syndrome, which can be treated with somatostatin analogues and the Tph1 inhibitor telotristat ethyl in severe cases. Although the active drug telotristat can efficiently reduce serotonin levels, its effect on tumor growth is unclear. This study determined the effect of serotonin inhibition on tumor cell growth in vitro and in vivo. The levels of Tph1 in various neuroendocrine neoplasms (NENs) were determined and the biological effects of Tph1 inhibition in vitro and in vivo using genetic and pharmacologic approaches was tested. Gene and protein expression analyses were performed on patient tumors and cancer cell lines. shRNAs targeting TPH1 were used to create stable knockdown in BON cells. Control and knockdown lines were assessed for their growth rates in vitro and in vivo, angiogenesis potential, serotonin levels, endothelial cell tube formation, tumor weight, and tumor vascularity. TPH1 is highly expressed in SBNETs and many cancer types. TPH1 knockdown cells and telotristat treated cells showed similar growth rates as control cells in vitro. However, TPH1 knockdown cells formed smaller tumors in vivo and tumors were less vascularized. Although Tph1 inhibition with telotristat showed no effect on tumor cell growth in vitro, Tph1 inhibition reduced tumor formation in vivo. Serotonin inhibition in combination with other therapies is a promising new avenue for targeting metabolic vulnerabilities in NENs.

cancer biology↗

bioRxiv2023

Tubular Mitochondrial Pyruvate Carrier Disruption Elicits Redox Adaptations that Protect from Acute Kidney Injury

Energy-intensive kidney reabsorption processes essential for normal whole-body function are maintained by tubular epithelial cell metabolism. Tubular metabolism changes markedly following acute kidney injury (AKI), but which changes are adaptive versus maladaptive remain poorly understood. In publicly available data sets, we noticed a consistent downregulation of the mitochondrial pyruvate carrier (MPC) after AKI, which we experimentally confirmed. To test the functional consequences of MPC downregulation, we generated novel tubular epithelial cell-specific Mpc1 knockout (MPC TubKO) mice. 13C-glucose tracing, steady-state metabolomic profiling, and enzymatic activity assays revealed that MPC TubKO coordinately increased activities of the pentose phosphate pathway and the glutathione and thioredoxin oxidant defense systems. Following rhabdomyolysis-induced AKI, MPC TubKO decreased markers of kidney injury and oxidative damage and strikingly increased survival. Our findings suggest that decreased mitochondrial pyruvate uptake is a central adaptive response following AKI and raise the possibility of therapeutically modulating the MPC to attenuate AKI severity.

biochemistry↗

bioRxiv2022

H3.1Cys96 oxidation by mitochondrial ROS promotes chromatin remodeling, breast cancer progression to metastasis and multi-drug resistance

Transcription stability enforces cellular identity and is tightly controlled by restrictions imposed on both transcription factor function and target gene accessibility. Progression of cancer to metastasis and multi-drug resistance requires fluid transcriptional programs that can explore different genomic landscapes to enable clonal expansion of aggressive and treatment resistant phenotypes. Here, we show that increased levels of H2O2 produced in mitochondria leads to H3.1 oxidation at Cys96, a distinctive redox sensitive amino acid residue restricted to this histone variant, in the nucleus. The oxidation of Cys96 promotes the eviction of H3.1 from chromatin and its exchange with H3.3, thereby opening silenced portions of the chromatin. Mutation of Cys96 by an oxidation-resistant serine residue or quenching nuclear H2O2 reversed chemotherapy resistance and drove established metastatic disease into remission. Together, these results show that increased mitochondrial H2O2 production, characteristic of metabolic dysfunction, promotes transcriptional plasticity by removing structural chromatin restrictions imposed by the redox sensitive histone variant H3.1. We suggest that this new regulatory nexus between cancer metabolism and chromatin remodeling controls chromatin states that enable cancer progression and drug resistance acquisition.

cancer biology↗

bioRxiv2021

Sex Differences in Brain Tumor Glutamine Metabolism Reveal Sex-Specific Vulnerabilities to Treatment

Sex differences in normal metabolism are well described, but whether they persist in cancerous tissue is unknown. We assessed metabolite abundance in glioblastoma surgical specimens and found that male glioblastomas are enriched for amino acids, including glutamine. Using PET imaging, we found that gliomas in male patients exhibit significantly higher glutamine uptake. These sex differences were well-modeled in murine transformed astrocytes, in which male cells imported and metabolized more glutamine and were more sensitive to glutaminase 1 (GLS1) inhibition. The sensitivity to GLS1 inhibition in males was driven by their dependence on glutamine-derived glutamate for -ketoglutarate synthesis and TCA cycle replenishment. Females were resistant to GLS1 inhibition through greater pyruvate carboxylase-mediated TCA cycle replenishment. Thus, clinically important sex differences exist in targetable elements of metabolism. Recognition of sex-biased metabolism is an opportunity to improve treatments for all patients through further laboratory and clinical research.

cancer biology↗