A peptide trivalent arsenical inhibits tumor angiogenesis by perturbing mitochondrial function in angiogenic endothelial cells

AbstractMitochondria are the powerhouse of the cell and their disruption leads to cell death. We have used a peptide trivalent arsenical, 4-(N-(S-glutathionylacetyl)amino) phenylarsenoxide (GSAO), to inactivate the adenine nucleotide translocator (ANT) that exchanges matrix ATP for cytosolic ADP across the inner mitochondrial membrane and is the key component of the mitochondrial permeability transition pore (MPTP). GSAO triggered Ca2+-dependent MPTP opening by crosslinking Cys160 and Cys257 of ANT. GSAO treatment caused a concentration-dependent increase in superoxide levels, ATP depletion, mitochondrial depolarization, and apoptosis in proliferating, but not growth-quiescent, endothelial cells. Endothelial cell proliferation drives new blood vessel formation, or angiogenesis. GSAO inhibited angiogenesis in the chick chorioallantoic membrane and in solid tumors in mice. Consequently, GSAO inhibited tumor growth in mice with no apparent toxicity at efficacious doses

Targeting of two aspects of metabolism in breast cancer treatment

Deregulated metabolism is gaining recognition as a hallmark of cancer cells, and is being explored for therapeutic potential. The Warburg effect is a metabolic phenotype that occurs in 90% of tumors, where glycolysis is favored despite the presence of oxygen. Dichloroacetate (DCA) is a pyruvate dehydrogenase kinase (PDK) inhibitor that can reverse the Warburg effect. PENAO (4-(N-(S-penicillaminylacetyl)amino) phenylarsonous acid) is a novel anti-mitochondrial agent that targets the adenine nucleotide transporter in mitochondria and is currently in clinical trials for solid tumors. We have investigated the targeting of two aspects of metabolism, using DCA to promote mitochondrial activity combined with PENAO to inhibit mitochondrial activity, in breast and other carcinoma cell lines. PENAO was effective at low uM concentrations in luminal (T-47D) and triple negative (MDA-MB-231) breast cancer cells, in normoxia and hypoxia. The cytotoxicity of PENAO was enhanced by DCA by a mechanism involving increased reactive oxygen species in both T-47D and MDA-MB-231 cells, however further investigations found it did not always involve PDK2 inhibition or reduction of the mitochondrial membrane potential, which are the accepted mechanisms for DCA induction of apoptosis. Nevertheless, DCA sensitized all cancer cell lines tested toward apoptosis of PENAO. DCA and PENAO are both currently in clinical trials and targeting cancer metabolism with these drugs may offer options for difficult to treat cancers

The tumour metabolism inhibitors GSAO and PENAO react with cysteines 57 and 257 of mitochondrial adenine nucleotide translocase

<p>Abstract</p> <p>Background</p> <p>GSAO (4-(N-(S-glutathionylacetyl)amino) phenylarsonous acid) and PENAO (4-(N-(S-penicillaminylacetyl)amino) phenylarsonous acid) are tumour metabolism inhibitors that target adenine nucleotide translocase (ANT) of the inner-mitochondrial membrane. Both compounds are currently being trialled in patients with solid tumours. The trivalent arsenical moiety of GSAO and PENAO reacts with two matrix facing cysteine residues of ANT, inactivating the transporter. This leads to proliferation arrest and death of tumour and tumour-supporting cells.</p> <p>Results</p> <p>The two reactive ANT cysteine residues have been identified in this study by expressing cysteine mutants of human ANT1 in <it>Saccharomyces cerevisiae </it>and measuring interaction with the arsenical moiety of GSAO and PENAO. The arsenic atom of both compounds cross-links cysteine residues 57 and 257 of human ANT1.</p> <p>Conclusions</p> <p>The sulphur atoms of these two cysteines are 20 Å apart in the crystal structures of ANT and the optimal spacing of cysteine thiolates for reaction with As (III) is 3-4 Å. This implies that a significant conformational change in ANT is required for the organoarsenicals to react with cysteines 57 and 257. This conformational change may relate to the selectivity of the compounds for proliferating cells.</p

The tumour metabolism inhibitors GSAO and PENAO react with cysteines 57 and 257 of mitochondrial adenine nucleotide translocase

Background: GSAO (4-(N-(S-glutathionylacetyl)amino) phenylarsonous acid) and PENAO (4-(N-(S-penicillaminylacetyl) amino) phenylarsonous acid) are tumour metabolism inhibitors that target adenine nucleotide translocase (ANT) of the inner-mitochondrial membrane. Both compounds are currently being trialled in patients with solid tumours. The trivalent arsenical moiety of GSAO and PENAO reacts with two matrix facing cysteine residues of ANT, inactivating the transporter. This leads to proliferation arrest and death of tumour and tumour-supporting cells. Results: The two reactive ANT cysteine residues have been identified in this study by expressing cysteine mutants of human ANT1 in Saccharomyces cerevisiae and measuring interaction with the arsenical moiety of GSAO and PENAO. The arsenic atom of both compounds cross-links cysteine residues 57 and 257 of human ANT1. Conclusions: The sulphur atoms of these two cysteines are 20 Å apart in the crystal structures of ANT and the optimal spacing of cysteine thiolates for reaction with As (III) is 3-4 Å. This implies that a significant conformational change in ANT is required for the organoarsenicals to react with cysteines 57 and 257. This conformational change may relate to the selectivity of the compounds for proliferating cells

Insight into the selectivity of arsenic trioxide for acute promyelocytic leukemia cells by characterizing Saccharomyces cerevisiae deletion strains that are sensitive or resistant to the metalloid

The genome-wide set of Saccharomyces cerevisiae deletion strains provides the opportunity to analyze how other organisms may respond to toxic agents. Since arsenic trioxide selectively kills human acute promyelocytic leukemia (APL) cells by a poorly understood mechanism we screened the yeast deletion strains for sensitivity or resistance. In addition to confirming mutants previously identified as sensitive to sodium arsenite, a large number of additional genes, and cellular processes, were required for arsenic trioxide tolerance. Of the 4546 mutants, 7.6% were more sensitive to arsenic trioxide than the wild type, while 1.5% was more resistant. IC50 values for all sensitive and resistant mutants were determined. Prominent as sensitive was that missing the MAP kinase, Hog1. The most resistant lacked the plasma-membrane glycerol and arsenite transporter, Fps1. Hog1 and Fps1 control the response to osmotic stress in yeast by regulating glycerol production and plasma membrane flux, respectively. We therefore tested whether APL cells have impaired osmoregulation. The APL cell line NB4 did not produce glycerol in response to osmotic stress and underwent apoptotic cell death. Moreover, the glycerol content of NB4 and differentiated NB4 cells correlated with the level of arsenic trioxide uptake and the sensitivity of the cells. Additionally, NB4 cells accumulated more arsenic trioxide than non-APL cells and were more sensitive. These findings demonstrate the usefulness of the S. cerevisiae deletion set and show that the selectivity of arsenic trioxide for APL cells relates, at least in part, to impaired osmoregulation and control of uptake of the drug

Mechanism of selectivity of an angiogenesis inhibitor from screening a genome-wide set of saccharomyces cerevisiae deletion strains

Background: The synthetic tripeptide arsenical 4-(N-(S-glutathionylacetyl)amino) phenylarsenoxide (GSAO) is an angiogenesis inhibitor that targets the mitochondria of actively dividing but not quiescent endothelial cells, arresting their proliferation and causing apoptosis. Normal endothelial cells are much more sensitive to GSAO than tumor cells. To elucidate the mechanism of tumor cell resistance, we identified yeast genes that are necessary for resistance to GSAO. Methods: We screened a genome-wide set of 4546 Saccharomyces cerevisiae deletion strains to identify GSAO-sensitive strains. We then examined GSAO accumulation in and proliferation activity of endothelial cells (BAECs) and tumor cells treated with GSAO and modulators of pathways and proteins identified in the yeast screen. We also examined GSAO effects on proliferation of mammalian cells transfected with transporter protein constructs. Results: Eighty-eight deletion strains were sensitive to GSAO. The most sensitive strains had deletions of genes whose products are involved in vacuolar function (corresponding to drug transport in mammalian cells) and glutathione synthesis. BAECs were more sensitive to GSAO than tumor cells, and cell sensitivity to GSAO was approximately proportional to cellular glutathione levels. Treatment of BAECs and tumor cells with MK-571, an inhibitor of multidrug resistance-associated protein (MRP), or with buthionine sulfoximine, an inhibitor of glutathione synthesis, increased their sensitivity to GSAO. Mammalian cells transfected with MRP1 or MRP2 were resistant to GSAO, whereas cells transfected with MRP3, MRP4, MRP5, P-glypoprotein, or breast cancer resistance protein were not. Conclusions: Differences in MRP activity and cellular glutathione levels contribute to the selectivity of GSAO for endothelial versus tumor cells. MRP1 and/or MRP2 may transport GSAO from resistant cells, with glutathione acting as a cotransporter. Genetic screening in yeast is a powerful tool for understanding drug action in mammalian cells

A Phase 1 study for safety and pharmacokinetics of BIO101 (20‐hydroxyecdysone) in healthy young and older adults

Abstract Background Sarcopenia is an age‐related skeletal muscle disorder characterized by loss of muscle mass and strength leading to mobility disability. 20‐Hydroxyecdysone (20E) is a polyhydroxylated plant steroid that demonstrates pharmacological effects in many disease animal models including ageing/sarcopenia. BIO101 is a 20E purified investigational drug (≥97%) that previously demonstrated good toxicology profiles in rat and dog. BIO101 is evaluated in healthy young and older adults in a Phase 1 study. Methods This study is a Single Ascending Dose (SAD) followed by a 14‐day Multiple Ascending Dose (MAD). In SAD, BIO101 was administered orally to 16 young adults at doses from 100 to 1400 mg and to 8 older adults (age ≥65 years) at 1400 mg. In MAD, doses of 350 mg once daily (qd), 350 mg twice daily (bid) and 450 mg bid were administered to 10 older adults. The primary objective was to evaluate safety and pharmacokinetics (PK), including dosing of circulating metabolites. Pharmacodynamic effects were investigated with regard to myostatin, procollagen‐III‐amino‐terminal propeptide (PIIINP), myoglobin, creatine‐kinase Muscle Brain (CKMB), renin and aldosterone plasma/serum levels. Results BIO101 showed a good safety profile with only mild to moderate adverse events and a satisfactory pharmacokinetic profile. In SAD, at 100 mg to 1400 mg, mean Cmax and areas under the curve increased less than dose‐proportionally. Mean half‐life was short (2.4–4.9 h), and mean renal clearance was comparable in all doses (4.05–5.05 L/h). Mean plasma exposure was slightly lower in older adults (22% lower for Cmax and 13%–15% lower for AUCs) compared with young subjects. In MAD, 350 and 450 mg bid led to a slight accumulation over 14 days (mean ratio of accumulation [Rac] of 1.31 in both cohorts). Reduction of biomarkers (myoglobin, CK‐MB) mean serum levels (vs. baseline) was observed at 450 mg bid. Two major metabolites of 20E (14‐deoxy‐20‐hydroxyecdysone and 14‐deoxypoststerone) were identified and quantified. Conclusions BIO101 shows a good safety and pharmacokinetic profile that led to the selection of doses for the subsequent interventional clinical trials of Phase 2 in age‐related sarcopenia (SARA‐INT) and Phase 3 in Covid‐19 (COVA)

Resolution and improved synthesis of (±)-arsenicin A: a natural adamantane-type tetraarsenical possessing strong anti-acute promelocytic leukemia cell line activity

The resolution and improved synthesis of the naturally occurring, adamantane-type, tetraarsenical (±)-Arsenicin A is reported. The five-step synthesis of (±)-Arsenicin A from methylenebis(phenylarsinic acid) affords (±)-Arsenicin A as air-stable, colo