Ubc1 turnover contributes to the spindle assembly checkpoint in Saccharomyces cerevisiae

The spindle assembly checkpoint protects the integrity of the genome by ensuring that chromosomes are properly attached to the mitotic spindle before they are segregated during anaphase. Activation of the spindle checkpoint results in inhibition of the Anaphase-Promoting Complex (APC), an E3 ubiquitin ligase that triggers the metaphase-anaphase transition. Here, we show that levels of Ubc1, an E2 enzyme that functions in complex with the APC, modulate the response to spindle checkpoint activation in Saccharomyces cerevisiae. Overexpression of Ubc1 increased resistance to microtubule poisons, whereas Ubc1 shut-off sensitized cells. We also found that Ubc1 levels are regulated by the spindle checkpoint. Checkpoint activation or direct APC inhibition led to a decrease in Ubc1 levels, charging, and half-life. Additionally, stabilization of Ubc1 prevented its down-regulation by the spindle checkpoint and increased resistance to checkpoint-activating drugs. These results suggest that down-regulation of Ubc1 in response to spindle checkpoint signaling is necessary for a robust cell cycle arrest.

Abstract 2328: Interrogating the anti-cancer effects of co-enzyme Q10 (CoQ10) identifies metabolic and mitochondrial apoptotic responses as primary mechanisms in squamous cell carcinoma model

Targeting mitochondrial function as a therapeutic modality in cancer has been extensively investigated. BPM 31510 is a proprietary drug-lipid nanoconjugate formulation enabling delivery of supra-physiological concentrations of oxidized CoQ10 specifically into mitochondria. In this study, the anti-cancer properties of CoQ10 in squamous cell carcinoma (SCC) and its mechanism of action were investigated in in vivo xenograft and in vitro model systems. Nude mice were inoculated with a squamous carcinoma cell line isolated from tongue, SCC-25, and treated with a topical formulation containing 1.5% or 5% CoQ10. Treatment was associated with a dose-dependent delay in the detection of palatable tumors (14 ± 3 days vehicle control, 27 ± 7 days 1.5% cream, 39 ± 9 days 5% cream), (p<0.05). Histology and immunostaining analysis demonstrated a decrease in expression of VEGF in the treatment groups (p<0.05). The anti-cancer mechanism of action of CoQ10 was further investigated by interrogating the influence of CoQ10 exposure on molecular profiles using SCC-25 cells in vitro. Cell based assays, mRNA-based RT-PCR assays, and protein-based antibody chip microarrays confirmed an apoptotic response as a major anti-cancer effect in SCC-25 cells in response to CoQ10 exposure. The change in anti- and pro-apoptotic markers (Bcl-2 and caspase families) was independently confirmed by western blotting. In addition, global proteomic analysis revealed alterations in key metabolic proteins in the Pentose Phosphate Pathway (PPP). For example, expression of Transaldolase 1, an enzyme involved in the cellular protection against oxidative stress, resistance/susceptibility to apoptosis, and SCC tumor development and progression, was reduced 1.5 fold at both 6 and 24 hour time point in response to CoQ10 treatment. Together, the data suggests that CoQ10 influences cancer metabolism and redox pathway in activating apoptosis in SCC cancer model.

Citation Format: Niven R. Narain, Shiva Kazerounian, Shivani Khatu, Anne R. Diers, John McCook, Stephane Gesta, Robert S. Kirsner, Brian Berman, Rangaprasad Sarangarajan. Interrogating the anti-cancer effects of co-enzyme Q10 (CoQ10) identifies metabolic and mitochondrial apoptotic responses as primary mechanisms in squamous cell carcinoma model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2328.

Abstract 2982: Utility of S. cerevisiae genetic interactions in the mechanistic validation and therapeutic potential of highly conserved targets for drug discovery

Use of chemo-genetic interaction mediated synthetic lethality represents a strategy for mechanistic validation of targets and gene-based patient stratification for clinical development. Given that core pathways supporting cancer development and progression (cell cycle regulation, genome integrity, metabolism) are highly conserved, orthogonal model organisms represent powerful systems in which to identify synthetic lethal pairs for highly conserved human drug targets. BPM42522 is an enzyme in the ubiquitin proteasome system whose anti-cancer potential has been validated through genetic and pharmacologic modulation. The S. cerevisiae homolog of BPM42522 (yBPM42522) is a critical cell cycle-regulatory gene with 273 genetic interactions affecting fitness (Costanzo 2016). Negative genetic interactors regulate cellular processes validated for therapeutic intervention in oncology such as DNA replication and repair, protein turnover, and mitosis. Thus, mapping yBPM42522 negative genetic interactors to their human homologs and curating tumors in which they are altered may aid in identification of clinical contexts more susceptible to pharmacologic inhibition of BPM42522. To this end, conservation analysis of genetic interactors of yBPM42522 was performed, and coding mutations and deletion events were then characterized using The Cancer Genome Atlas (TCGA) tumor data. The most frequently altered genetic interactors across human tumors were reviewed for the direction and strength of the genetic interaction between their yeast homologs and yBPM42522, and mutations were curated by their likelihood to result in a loss of function. Those with strong negative genetic interactions with yBPM42522 and frequent mutation or deletion in its human homolog were prioritized. The resulting candidates included tumor suppressors (FBXW7, NF1), cell cycle regulators (CCNB1, CCNB3, BUB1B), and the NIMA kinase and GTPase-activating protein families (NEK3, NEK4, RASA1, RASAL2). TCGA database was used to determine if alterations in these candidate genes were prevalent in specific tumor types and whether they co-occurred with alterations in established cancer driver genes. Several candidate genetic interactors identified were frequently mutated or deleted in specific tumor types including uterine carcinosarcoma, uterine corpus endometrial carcinoma, ovarian serous cystadenocarcinoma, and mesothelioma. Moreover, these alterations were mutually exclusive with 96 reported cancer driver genes. Validation of the candidate genetic interactors for synthetic lethality with BPM42522 and their role in specific cancer types highlights the approach for rapid identification of synthetic lethality and its potential use to stratify patient populations most likely to benefit from therapeutic agents targeting highly conserved drug targets.

Citation Format: Anne R. Diers, Kris Richardson, Leonardo O. Rodrigues, Rangaprasad Sarangarajan, Niven R. Narain, Jennifer A. Benanti, Stephane Gesta. Utility of S. cerevisiae genetic interactions in the mechanistic validation and therapeutic potential of highly conserved targets for drug discovery [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2982.

Elevated levels of mitochondrial CoQ10 induce ROS-mediated apoptosis in pancreatic cancer

Reactive oxygen species (ROS) are implicated in triggering cell signalling events and pathways to promote and maintain tumorigenicity. Chemotherapy and radiation can induce ROS to elicit cell death allows for targeting ROS pathways for effective anti-cancer therapeutics. Coenzyme Q10 is a critical cofactor in the electron transport chain with complex biological functions that extend beyond mitochondrial respiration. This study demonstrates that delivery of oxidized Coenzyme Q10 (ubidecarenone) to increase mitochondrial Q-pool is associated with an increase in ROS generation, effectuating anti-cancer effects in a pancreatic cancer model. Consequent activation of cell death was observed in vitro in pancreatic cancer cells, and both human patient-derived organoids and tumour xenografts. The study is a first to demonstrate the effectiveness of oxidized ubidecarenone in targeting mitochondrial function resulting in an anti-cancer effect. Furthermore, these findings support the clinical development of proprietary formulation, BPM31510, for treatment of cancers with high ROS burden with potential sensitivity to ubidecarenone.

High levels of ubidecarenone (oxidized CoQ10) delivered using a drug-lipid conjugate nanodispersion (BPM31510) differentially affect redox status and growth in malignant glioma versus non-tumor cells

Metabolic reprogramming in cancer cells, vs. non-cancer cells, elevates levels of reactive oxygen species (ROS) leading to higher oxidative stress. The elevated ROS levels suggest a vulnerability to excess prooxidant loads leading to selective cell death, a therapeutically exploitable difference. Co-enzyme Q₁₀ (CoQ₁₀) an endogenous mitochondrial resident molecule, plays an important role in mitochondrial redox homeostasis, membrane integrity, and energy production. BPM31510 is a lipid-drug conjugate nanodispersion specifically formulated for delivery of supraphysiological concentrations of ubidecarenone (oxidized CoQ₁₀) to the cell and mitochondria, in both in vitro and in vivo model systems. In this study, we sought to investigate the therapeutic potential of ubidecarenone in the highly treatment-refractory glioblastoma. Rodent (C6) and human (U251) glioma cell lines, and non-tumor human astrocytes (HA) and rodent NIH3T3 fibroblast cell lines were utilized for experiments. Tumor cell lines exhibited a marked increase in sensitivity to ubidecarenone vs. non-tumor cell lines. Further, elevated mitochondrial superoxide production was noted in tumor cells vs. non-tumor cells hours before any changes in proliferation or the cell cycle could be detected. In vitro co-culture experiments show ubidecarenone differentially affecting tumor cells vs. non-tumor cells, resulting in an equilibrated culture. In vivo activity in a highly aggressive orthotopic C6 glioma model demonstrated a greater than 25% long-term survival rate. Based on these findings we conclude that high levels of ubidecarenone delivered using BPM31510 provide an effective therapeutic modality targeting cancer-specific modulation of redox mechanisms for anti-cancer effects.

Abstract 2968: BPM31510, a Coenzyme Q10 (CoQ10) containing lipid nanodispersion, enhances radiation effects to prolong survival in a rodent glioblastoma model

BPM31510 is a Coenzyme Q10 (CoQ10)-containing lipid nanodispersion in clinical development for the treatment of glioblastoma. Prior results demonstrate that high doses of CoQ10 delivered via BPM31510 differentially increases oxidative stress in glioblastoma relative to non-tumor cells in vitro and extends long-term survival (LTS) in an in vivo glioblastoma model. Since a primary consequences of tumor irradiation is induction of oxidative stress, we hypothesized that BPM31510 treatment would result in an enhanced radiation response and influence survival outcomes.1 x 106 luciferase labeled C6 cells were implanted into the right striatum of Sprague Dawley rats. 4 days post-implantation, rats were randomized into one of four groups: (i) Saline injection ip bid; (ii) BPM31510 50 mg/kg ip bid to continue up to 35 days; (iii) 12 Gy radiotherapy (RT) to be administered on Day 8 post-implant with saline injection; and (iv) BPM31510 + RT. Tumor-bearing rats were monitored until death or Day 50. Log rank survival analysis indicated a marked enhancement of median survival with the addition of BPM31510 to RT. While neither RT nor BPM31510 enhanced median survival relative to saline, the combination was markedly more effective (median survival of 17, 19, 24 and >50 days for saline, BPM31510, RT and combination, respectively, p < 0.001). This was also reflected in increase in frequency of LTS, which was over 70% (11 of 14 rats) in the combination group (p < 0.01 compared to control). BPM31510 significantly enhanced the therapeutic efficacy of radiation in this model of glioblastoma. Effects on median survival and an enhancement of LTS with combination treatment were observed. While the mechanistic underpinnings are under investigation, the low toxicity profile of BPM31510 and its potential protective effects on normal cells may offer a unique strategy with which to enhance radiation.

Citation Format: Jiaxin Sun, Milton Merchant, Anne R. Diers, Shiva Kazerounian, Stephane Gesta, Niven R. Narain, Rangaprasad Sarangarajan, Seema Nagpal, Lawrence Recht. BPM31510, a Coenzyme Q10 (CoQ10) containing lipid nanodispersion, enhances radiation effects to prolong survival in a rodent glioblastoma model [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2968.

Abstract 3608: BPM31510 exploits differential redox vulnerabilities between normal and glioblastoma cells to mediate its anti-cancer effect

Glioblastoma is an aggressive cancer, the proliferative capacity of which is correlated with glycolytic metabolism. BPM31510 is a novel formulation for delivery of supraphysiological levels of ubidecarenone to the mitochondria, enabling cancer specific metabolic switches. It is being studied in Phase I clinical trials versus a number of tumors, including glioma. Here, the effects of ubidecarenone on viability and redox homeostasis of glioma and non-tumorigenic cells was assessed using in vitro monoculture and coculture systems and an in vivo preclinical model. BPM31510 administration (50 mg/kg bid i.p., beginning 4-8 days post-inoculation) resulted in over a 20% long term survival rate in C6 tumor-bearing rats. We next compared BPM31510 effects in vitro between glioma lines (rat C6, human U251) and murine NIH3T3 fibroblasts, as a stromal control. In monocultures, decreased growth was observed in glioma lines and NIH3T3 with increasing BPM31510 doses; however, glioma lines were 2-fold more sensitive to BPM31510 compared to NIH3T3 cells (IC50 glioma lines: 230 µM vs IC50 NIH3T3: >460 µM). To investigate the differential sensitivity to BPM31510, a coculture system was developed by coincubating 2 x 105 C6-GFP labeled cells and NIH3T3 cells. After 6 days of coculture, the percentage of C6 relative to NIH3T3 cells was lowest at doses of BPM31510 between 115 µM and 230 µM, evidence of greater sensitivity to BPM31510-induced cytotoxicity in the C6 glioma cells than the non-tumorigenic component. At higher doses, differential effects on cell viability were less apparent. The level of superoxide, a central reactive oxygen species important in redox homeostasis, was also assessed using Mitosox in cocultures. At a BPM31510 dose which resulted in maximal differential viability between C6 and NIH3T3 cells (230 μM), the maximal differential superoxide level was likewise greatest. The basal differential in Mitosox signal was 9-fold between C6 and NIH3T3 cells, and it increased to over 50-fold upon treatment with BPM31510 (230 μM), implying that BPM31510 exploits differential redox vulnerabilities between C6 and NIH3T3 to mediate its anti-cancer activity. At high doses of BPM31510, differential effects on superoxide levels were less apparent. In summary, BPM31510 has marked anti-cancer activity in rats implanted with C6 glioma, and its differential effects on the viability of normal and transformed cells are associated with maximal differences in BPM31510-induced superoxide production. Together, these data suggest that differential redox vulnerabilities between tumorigenic and non-tumorigenic cells may underpin the anti-cancer activity of BPM31510, and identification of in vivo correlates of redox indices may represent an avenue to improved measurement of anti-cancer efficacy as well as define patient populations responsive to BPM31510.

Citation Format: Jiaxin Sun, Seema Nagpal, Chirag Patel, Milton Merchant, Tiachang Jang, Anne R. Diers, Shiva Kazerounian, Stephane Gesta, Niven R. Narain, Rangaprasad Sarangarajan, Lawrence Recht. BPM31510 exploits differential redox vulnerabilities between normal and glioblastoma cells to mediate its anti-cancer effect [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3608.

Abstract 3530: Coenzyme Q10 (BPM31510-IV in clinical trials) increases mitochondrial Q-pool and modulates electron transport chain function to elicit cell death in pancreatic cancer cells

Mitochondria play a multifaceted role in tumorigenesis through regulation of energy production, biomass, redox state, and engagement of cell death pathways. The mitochondrial Q (coenzyme Q10)-pool facilitates electron transport from Complexes I and II to III and is essential for regulating these activities. Therefore, altering mitochondrial Q-pool homeostasis represents a potential therapeutic strategy in cancer. BPM 31510 is a Coenzyme Q10 containing lipid nanodispersion currently in clinical trials for pancreatic cancer. Here, we used BPM 31510 to assess how modulation of mitochondrial Q-pool homeostasis impacts mitochondrial electron transport chain function to activate regulated cell death. Pancreatic cancer cell lines (MIA PaCa-2 and Panc-1) represent models with sensitivity to BPM 31510 both in vitro and in vivo. Treatment with BPM 31510 (EC50 dose, 24 h) resulted in significant mitochondrial enrichment of CoQ10 compared to other subcellular compartments, and quantitatively, CoQ10 levels were 100 times higher in mitochondria isolated from BPM 31510 treated cells over untreated controls (MIA PaCa-2 untreated, 0.31 nmol/mg; treated, 39.4 nmol/mg; Panc1 untreated, 0.21 nmol/mg; treated, 29.3 nmol/mg). Alterations in mitochondrial respiration characterized by dose-dependent decreases in succinate- or glycerol-3-phosphate-fueled respiration were observed in cells treated with BPM 31510, while pyruvate or TMPD/ascorbate-fueled respiration was only modestly affected, suggesting that BPM31510 specifically impairs respiratory responses dependent on Complexes II/III. Moreover, in the presence of multiple mitochondrial substrates, total respiratory capacity was decreased and reliance on pyruvate (Complex I)-fueled respiration was increased with BPM 31510 treatment, indicative of bioenergetic remodeling. Concomitantly to BPM 31510-dependent changes in mitochondrial respiratory responses, BPM 31510 exposure increased oxidation of the reactive oxygen species (ROS) probes, CellROX Green and DCF-DA, increased oxidized glutathione, and decreased levels of the cellular reducing equivalent NADPH. Importantly, BPM 31510-induced death could be partially rescued by agents which alleviate electron transport chain impairment linking respiratory function to the anti-cancer mechanism of action of BPM 31510. Together, these data indicate that BPM31510 directly impairs the mitochondrial Q-pool and respiratory function resulting in oxidative stress and consequential cell death and thus provide mechanistic understanding of the anti-cancer activity of BPM31510.

Citation Format: Pallavi Awate, Tulin Dadali, Ryan Ng, Saie Mogre, Anne R. Diers, Hannah Rockwell, Justice McDaniel, Emily Chen, Fei Gao, Michael Kiebish, Stephane Gesta, Vivek Vishnudas, Niven R. Narain, Rangaprasad Sarangarajan. Coenzyme Q10 (BPM31510-IV in clinical trials) increases mitochondrial Q-pool and modulates electron transport chain function to elicit cell death in pancreatic cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3530.

Abstract 4724: Immuno-modulatory activity of BPM31510 supports T cell viability, proliferation, and function while reversing early signs of exhaustion

Regulation of mitochondrial metabolism is crucial to alter immune cell differentiation and function; therefore, therapeutic agents which regulate mitochondrial metabolism may have efficacy in immune-mediated tumor elimination. BPM31510 is a clinical stage, nanodispersion of ubidecarenone (coenzyme Q10), an electron transfer molecule in the mitochondrial electron transport chain required for oxidative phosphorylation. Here, we used BPM31510 to assess the role of CoQ10 in the regulation of T cell function. Healthy donor peripheral blood mononuclear cells (PBMCs) activated ex vivo with αCD3/CD28 beads were used as model system to test the effects of BPM31510 on viability and functionality of T cell subpopulations. In contrast to its ability to initiate regulated cell death in cancer cells, treatment of PBMCs with increasing concentrations of BPM31510 lead to an increased frequency of viable CD3+ cells. Further phenotypic analysis revealed that cytotoxic T cells (CD8+/CD3+) and T helper cells (CD4+/CD3+), as well as NKT cells (CD56+/CD3+), contributed to the observed increase in T cell frequency. Proliferation measurements by EdU-incorporation indicated enhanced cytotoxic T cell proliferation in BPM31510 treated PBMCs, and likewise, BPM31510 increased degranulation of activated cytotoxic T cells, as indicated by measurement of plasma membrane-exposed lysosomal-associated membrane protein 1 (CD107a). Consistent with the ex vivo observations, in vivo studies using the syngeneic MC38 murine tumor model demonstrated that BPM31510 administration resulted in a dose-dependent enhancement of the number of CD3+ cells in the tumor microenvironment with cytotoxic T cells (CD8+/CD3+) representing the largest population. Together, these data define a supportive effect of BPM31510 on T cell frequency, viability, and functionality. In addition, in ex vivo activated PBMCs, BPM31510 decreased the percentage of PD1+ T cells while simultaneously increasing the percentage of PD1- T cells in the population. Moreover, in the PD1+ T cell population, PD1 expression on the cell surface was increased while PD1- T cells experienced no change in cell surface expression of PD1. These data suggest BPM31510 treatment promotes highly functional cytotoxic T cells while cells with early signs of exhaustion are induced to follow the path of exhaustion and elimination. Collectively, these results define an immune-modulatory activity for BPM31510, particularly in the T cell compartment, in part, through regulation of T cell exhaustion; this may have important implications for the use of BPM31510 in ‘immunologically cold' tumor types or in combination with immune checkpoint blockade strategies.

Citation Format: Maria Nastke, Shiva Kazerounian, Nidhi Gaur, Shyamali Jayashankar, David Linsenmayer, Carrie Spencer, Arun Nambiar, Aishwarya Sarma, Anne R. Diers, Stephane Gesta, Vivek Vishnudas, Vikas P. Sukhatme, Niven R. Narain, Rangaprasad Sarangarajan. Immuno-modulatory activity of BPM31510 supports T cell viability, proliferation, and function while reversing early signs of exhaustion [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4724.

Abstract 873: BPM 31510, a clinical stage metabolic modulator, demonstrates therapeutic efficacy in glioblastoma models of temozolomide chemo-sensitive and resistance by targeting mitochondrial function

BPM31510 is a metabolic modulating agent composed of a parenteral nanodispersion of ubidecarenone which is currently in clinical studies for glioblastoma. Glioblastoma is a highly metabolic and aggressive malignancy with limited treatment options and dismal median survival. Temozolomide (TMZ) as a first line treatment option, however, 90% of recurrent gliomas acquire TMZ chemoresistance. Recently, acquisition to TMZ resistance has been correlated to alterations in mitochondrial metabolism. Thus, in the present study we sought to investigate whether BPM31510 could elicit anti-cancer activity in TMZ naïve and TMZ-chemoresistant glioma models. In vitro, in a 2D model BPM31510 treatment demonstrated anti-cancer activity in a panel of glioma cell lines (rat C6 and human U251-MG and U87-MG), and this effect was translatable in spheroidal 3D cultures. Importantly, in an aggressive rat C6 orthotopic glioma model, treatment with BPM31510 (50mg/kg/day, b.i.d) starting between 4 and 8 days post-implantation resulted in a 32% cure rate compared to 0% in controls (P < 0.001, Fisher's exact test), demonstrating an improved survival (P < 0.01, log rank survival), despite producing a minimal change in median survival (13 vs. 12 days). A marked increase in caspase3 staining was observed in tumors from BPM31510 treated animals compared to controls assessed at a similar time point post-tumor implantation, suggesting a strong apoptotic effect of this agent in vivo. Next, BPM31510 was examined in a cellular model of acquired TMZ resistance (TMZ-R) generated by exposing parental (chemosensitive naïve) U251-MG and U87-MG cells to increasing concentrations of TMZ for 9-12 months. Similar to parental cells, BPM31510 displayed anti-cancer activity in both TMZ-R cell models, as decreased cell viability and an increase in the percentage of apoptotic cells was observed upon BPM31510 treatment. Consistent with prior studies, compared to parental cells, TMZ-R cells demonstrated metabolic rewiring characterized by increases in mitochondrial function parameters and decreased extracellular acidification rate, indicative of glycolytic flux. Regardless of chemosensitivity, BPM31510 decreased mitochondrial substrate oxidation (e.g., succinate, glycerol-3-phosphate) at doses which induce cell death. Concomitantly, increases in the reactive oxygen species production were observed with BPM 31510 treatment in both parental and TMZ-R cell lines. Together, these data define a link between regulation of mitochondrial function and the anti-cancer activity of BPM31510 in both TMZ chemo-sensitive and resistant glioblastoma models, demonstrating a distinct approach in targeting mitochondrial metabolism for the treatment of this clinically intractable disease.

Citation Format: Tulin Dadali, Shreya Kulkarni, Ryan Ng, Pallavi Awate, Saie Mogre, Anne R. Diers, Taichang Jang, Milton Merchant, Jiaxin Sun, Stephane Gesta, Khampaseuth Thapa, Seema Nagpal, Lawrence Recht, Niven R. Narain, Rangaprasad Sarangarajan. BPM 31510, a clinical stage metabolic modulator, demonstrates therapeutic efficacy in glioblastoma models of temozolomide chemo-sensitive and resistance by targeting mitochondrial function [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 873.

Abstract 5576: BPM 31510, a clinical stage candidate demonstrates potent anti-tumor effect in an immune-competent syngeneic pancreatic cancer model

BPM 31510, a clinical stage nanodispersion of ubidecarenone, demonstrates anti-tumor effects by eliciting an anti-Warburg metabolic switch in cancer. Previous studies in an immune compromised PaCa2 xenograft model has unequivocally demonstrated significant efficacy of BPM 31510 on tumor volume and survival. The fundamental property of BPM 31510 to influence mitochondrial bioenergetics and the recognized interplay between T cell metabolism and maturation prompted investigation into the effects of BPM 31510 on T lymphocyte functions in eliciting anti-cancer effects. In this study BPM 31510 selectively influenced activation and maturation of T cells in murine peripheral blood mononuclear cells (PBMCs). Moreover, in addition to determining changes in the CD3+ population, changes in surface expression of PD-1 and CTLA4 along with the IFN-γ secretion were examined. Murine cancer cell lines exposed to BPM 31510 were associated with variable sensitivity with highly metabolic tumor types being most sensitive. Next, the anti-cancer activity of BPM 31510 in an in vivo immunocompetent syngeneic Pan02 rodent model was investigated. Murine Pan02 pancreatic cancer cells were implanted subcutaneously into C57BL/6 mice. Tumors with mean volume of 80 mm3 were treated twice a day with vehicle control or BPM 31510 at 25, 50, 100 mg/kg, administered intraperitoneal. Tumor volumes were measured every 4 days. At day 21 post treatment, tumors were harvested and analyzed for the level of infiltrating immune cells by immunofluorescent staining with CD8+ for T cells and F4/80 for tumor macrophages. These results demonstrate a dose-dependent reduction in tumor volume following 21 days of BPM 31510 treatment. In summary, BPM 31510 exerts potent anti-tumor effects through its dual function of modulating tumor cell metabolism and potentially influencing immune check-point to improve overall survival outcomes.

Citation Format: Shiva Kazerounian, Aishwarya Sarma, Nidhi Gaur, Maria D. Nastke, Tulin Dadali, Anne R. Diers, Stephane Gesta, Vivek K. Vishnudas, Rangaprasad Sarangarajan, Niven R. Narain. BPM 31510, a clinical stage candidate demonstrates potent anti-tumor effect in an immune-competent syngeneic pancreatic cancer model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5576. doi:10.1158/1538-7445.AM2017-5576

Effect of BPM31510 on radiosensitivity of temozolomide-resistant glioblastoma cell model and survival in in vivo C6 glioma rat model supporting phase I clinical investigation in GBM

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Background: Glioblastoma (GB) is characterized by dysregulated metabolism, utilizing glycolysis for energy production to support unrestricted growth. BPM 31510, an ubidecarenone containing lipid nanodispersion effectuates a switch in cancer energy sourcing from glycolysis towards mitochondrial OXPHOS, i.e. reverses Warburg effect, providing rationale for its potential utility in treatment of GB. The current study investigated utility of BPM31510 alone and in combination with temozolomide. Methods: In vitro (U251-MG human GB cell line) and in vivo (C6 glioma rat model) preclinical models of GB were used to assess the anti-cancer activity of BPM 31510 alone (100 mg/kg/d) and combination with TMZ/bevacizumab (BEV). In addition, an in vitro model of acquired TMZ chemo-resistance was established by progressive adaptation of parental U251-MG cells to increasing doses of TMZ. Parental and resistant subclones (TMZ-R) were used to define activity of BPM31510 in the TMZ-refractory setting. Results: In vitro results demonstrated that BPM 31510 has anti-cancer activity in both parental and TMZ-R U251-MG cells with EC50 values of ~400 µM and 800 µM, respectively. Importantly, BPM 31510 treatment also resensitized TMZ-R cell lines to TMZ. In vivo, BPM 31510 treatment was associated with increasing duration of survival; one fifth of the rats treated achieved survival greater than 15 days post implantation, a response not observed in the control or irradiation arms of the study. Assessment of the combination of BPM 31510 with TMZ or BEV in the in vivoC6 glioma rat model is ongoing. A phase I open-label, non-randomized clinical trial to evaluate the safety and tolerability of BPM31510 in patients with recurrent BEV-refractory GB, as well as the changes in GB metabolism by SUV-PET imaging in response to treatment is under investigation. Conclusions: Preclinical data demonstrate that BPM 31510 has potential anti-cancer activity alone and in combination with standard therapy regimens and alleviates TMZ chemo-resistance in preclinical models of GB. These results provide support of a Phase 1 clinical study of BPM31510 in GB; this study is actively enrolling.

Thiolate-based dinitrosyl iron complexes: Decomposition and detection and differentiation from S-nitrosothiols

Dinitrosyl iron complexes (DNIC) spontaneously form in aqueous solutions of Fe(II), nitric oxide (NO), and various anions. They exist as an equilibrium between diamagnetic, dimeric (bi-DNIC) and paramagnetic, monomeric (mono-DNIC) forms. Thiolate groups (e.g., on glutathione or protein cysteine residues) are the most biologically relevant anions to coordinate to Fe(II). Low molecular weight DNIC have previously been suggested to be important mediators of NO biology in cells, and emerging literature supports their role in the control of iron-dependent cellular processes. Recently, it was shown that DNIC may be one of the most abundant NO-derived products in cells and may serve as intermediates in the cellular formation of S-nitrosothiols. In this work, we examined the stability of low molecular weight DNIC and investigated issues with their detection in the presence of other NO-dependent metabolites such as S-nitrosothiols. By using spectrophotometric, Electron Paramagnetic Resonance, ozone-based chemiluminesence, and HPLC techniques we established that at neutral pH, bi-DNIC remain stable for hours, whereas excess thiol results in decomposition to form nitrite. NO was also detected during the decomposition, but no S-nitrosothiol formation was observed. Importantly, mercury chloride accelerated the degradation of DNIC; thus, the implications of this finding for the diagnostic use of mercury chloride in the detection of S-nitrosothiols were determined in simple and complex biological systems. We conclude S-nitrosothiol levels may have been substantially overestimated in all methods where mercury chloride has been used.

Abstract 212: BPM 31510 synergizes gemcitabine efficacy in pancreatic adenocarcinoma via mechanism independent of its anti-Warburg influence on metabolism

Pancreatic adenocarcinoma (PanCa) is associated with poor prognosis and overall survival. Current first-line therapeutics are cytotoxic agents targeting DNA based mechanistic end-points for efficacy, their use limited by dose associated toxicity. There is a critical need for therapeutics with novel mechanisms amenable to combination with current standard-of-care chemotherapy to improve outcomes. BPM 31510 is a drug that targets cellular metabolism networks, effectuating an anti-Warburg effect in cancer. The documented high metabolic phenotype observed in PanCa provided rationale for investigation of BPM 31510 alone and in combination with gemcitabine in in vitro and in vivo PanCa models. Based on BPM 31510 EC50/EC>90 values for MIA-PaCa-2 and Panc-1 PanCa cell lines in vitro, the PanCa cells were significantly more sensitive to BPM 31510 compared to fibroblasts. BPM 31510 treatment in a time- and dose-dependent manner decreased the PI- and Annexin V-negative (viable) population and a concomitant increase in the percentage of Annexin V-positive cells, with PI indicative of early and late apoptosis. The anti-cancer activity of BPM 31510 was assessed in vivo using MIA-PaCa-2 tumor-bearing immune-compromised mice. Treatment with increasing doses of BPM 31510 (0.5-50 mg/kg IP, 3X/week) significantly improved survival outcomes, with the highest dose extending median survival by more than 36 days compared to saline control. Moreover, combined treatment with BPM 31510 and gemcitabine (150 mg/kg IV, 1X/week, given on cycles, 3 weeks on 1 week) resulted in further extension of median survival over either treatment alone. The mechanistic underpinnings for the enhanced efficacy of combination treatment were explored in vitro. In MIA-PaCa-2 cells, co-treatment with BPM 31510 and gemcitabine increased indices of regulated cell death higher than observed for either treatment alone. In contrast, although treatment with either BPM 31510 or gemcitabine alone increased caspase-3 activity, co-treatment did not enhance caspase-3 activation, suggesting that BPM 31510 augments gemcitabine cytotoxicity through independent mechanisms. In fact, BPM31510, and not gemcitabine, increased the mitochondrial uncoupling efficient ratio and Stateapparent in MIA-PaCa-2 cells. Nonetheless, co-treatment with BPM 31510 and gemcitabine synergistically decreased the mitochondrial membrane potential (ΔΨm) in cells prior to cell death. Taken together, these data indicate that BPM 31510-driven bioenergetic alterations are separate from the effects of gemcitabine; however, their effects converge at the mitochondrion to dissipate ΔΨm and activate regulated cell death. The data suggests that combination of BPM 31510 with gemcitabine in pancreatic cancer will effectuate an efficacy response via independent mechanisms with improvement in therapeutic outcome.

Citation Format: Tulin Dadali, Anne R. Diers, Rakib Ouro-Djobo, Justin Bourdelais, Ezer Benaim, Bianca Jambhekar, Tony E. Walshe, Vivek K. Vishnudas, Joaquin J. Jimenez, Rangaprasad Sarangarajan, Niven R. Narain. BPM 31510 synergizes gemcitabine efficacy in pancreatic adenocarcinoma via mechanism independent of its anti-Warburg influence on metabolism. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 212.

Abstract 1014: The anti-Warburg agent BPM 31510 arbitrates fatty acid metabolism in eliciting an anticancer response

De-regulated lipid homeostasis is a key feature of the altered metabolic phenotype observed in cancer, particularly in the adipose-rich microenvironment of breast tumors. Mitochondria serve as a central hub for lipid metabolism through mitochondrial β-oxidation pathways and biosynthesis through production of citric acid cycle-derived citrate and the activity of ATP citrate lyase, the rate-limiting enzyme in lipid biosynthesis. We have previously demonstrated BPM 31510 ability to effectuate Warburg switch from glycolysis to mitochondrial oxidative phosphorylation resulting in activation of apoptosis in multiple cancers including triple negative breast cancer. The present investigated the role of BPM 31510 in influencing lipid metabolism in cancer cells to arbitrate its anti-cancer effect. Cell viability was assessed in MDA-MB231 and SkBr-3 breast cancer cells exposed to BPM 31510 alone or in combination with fatty metabolism inhibitors including C75, etomoxir, and trimetazidine, inhibitors of fatty acid synthase (FASN), carnitine palmitoyltransferase 1 (CPT-1), and β-oxidation, respectively, as well as a more pleiotropic fatty acid metabolism modulator, metformin. Breast cancer cells were more sensitive to BPM 31510 when treated in combination with C75, etomoxir, and trimetazidine as indicated by a left-shift in the BPM 31510 dose-response curve in both MDA-MB231 and SkBr-3 cells. In contrast, combined treatment with metformin did not alter cytotoxic responses to BPM 31510, indicating specificity for responses in fatty acid metabolism pathway modulation. Interestingly, BPM31510 treatment was associated with a dose- and time-dependent increase in mRNA expression of fatty acid metabolism gene products (FASN, CPT1, ACSL1) and accumulation of the triglyceride backbone, glycerol, in MDA-MB-231 cells. Structural lipidomic analysis used to assess the metabolic fate of BPM 31510 liposomal formulation components demonstrated that these were readily incorporated into prevalent diacyl-glyerol (DAG) and triacyl-glycerol (TAG) species along with de novo fatty acid species such as palmitate. Together, these results demonstrate that BPM 31510 alters endogenous and exogenous lipid homeostasis in breast cancer cells and rationale for potential combination with fatty acid metabolism inhibitors for anti-cancer therapy. The results expands on BPM 31510 anti-cancer mechanism, suggesting a central role in arbitrating the convergence of glycolysis, glucose and fatty acid oxidation pathways within the cancer cell metabolism network.

Citation Format: Bianca Jambhekar, Tulin Dadali, Anne R. Diers, Fei Gao, Hannah Rockwell, Emily Chen, Stephane Gesta, Vivek K. Vishnudas, Michael A. Kiebish, Niven R. Narain, Rangaprasad Sarangarajan. The anti-Warburg agent BPM 31510 arbitrates fatty acid metabolism in eliciting an anticancer response. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1014.

Abstract 208: BPM 31510-induced alteration in Complex II activity is functionally linked to cell death activation pathway in a preclinical model of triple-negative breast cancer

Although only 15-20% of total breast cancer diagnoses are of the triple-negative breast cancer (TNBC) subtype, they account for a significant portion of the mortality rate due to their more aggressive phenotype and a high risk of reoccurrence. Metabolic rewiring supports breast cancer progression and metastasis, particularly in ER-negative and triple-negative (TNBC) breast tumors. Thus, we examined the effects of BPM 31510, a metabolic-modulating agent in clinical trials for solid tumors, in in vitro and in vivo ER-negative and TNBC models. BPM 31510 EC50/EC>90 values were determined for a panel of the breast cancer cell lines and compared to non-tumorigenic MCF12A cells in vitro, and the MDA-MB231 and SkBr-3, TNBC and ER-negative models respectively, were found to be the most sensitive to BPM 31510. Treatment with BPM 31510 (EC50 and EC>90 doses) resulted in a time- and dose-dependent decrease the viable cell population (PI- and Annexin V-negative) and a concomitant increase in cells in early and late apoptosis (PI-negative and PI-positive Annexin V-positive cells, respectively), suggesting that BPM 31510 activates regulated cell death pathways. Consistent with the in vitro data, MDA-MB231 tumor-bearing mice had smaller tumors after 30 days of treatment with BPM 31510 and increased cleaved caspase 3 staining in resected tumors. In vitro, BPM 31510-dependent breast cancer cell death was preceded by mitochondrial membrane potential depolarization (TMRE flow cytometry) and alterations in mitochondrial respiration characterized by a consistent, dose-dependent decrease in succinate (Complex II)-fueled respiration with more varied responses to BPM 31510 in cells provided the Complex I substrates (pyruvate or palmitoyl carnitine). To investigate the role of Complex II in BPM 31510-mediated cell death, pharmacological inhibitors of the dicarboxylate site (malonate) and Qp site (atpenin A5) of Complex II were used in combination with BPM 31510 to assess the resultant effects on cell death in MDA-MB231 cells. Co-treatment with malonate significantly attenuated BPM 31510-mediated cell death while atpenin A5 did not affect BPM 31510-induced cell death, indicating succinate oxidation at the dicarboxylate site of Complex II is required, in part, for induction of cell death by BPM 31510. Together, these data demonstrate BPM 31510 has a potent anti-cancer activity in preclinical breast cancer models and define a functional link between Complex II activity and the mechanism of action for BPM 31510.

Citation Format: Tulin Dadali, Anne R. Diers, Arleide Lee, Ezer Benaim, Joaquin J. Jimenez, Stephane Gesta, Vivek K. Vishnudas, Rangaprasad Sarangarajan, Niven R. Narain. BPM 31510-induced alteration in Complex II activity is functionally linked to cell death activation pathway in a preclinical model of triple-negative breast cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 208.

Abstract C117: BPM 31510 enhances efficacy of gemcitabine through orthogonal mechanisms in a preclinical model of pancreatic adenocarcinoma

Despite global advances in cancer detection and treatment in some indications, the early diagnosis and overall survival rate for pancreatic cancer (PanCa) remains dismal. Thus, there is a critical need for novel therapeutics that may combine well with standard-of-care therapy or work through novel mechanisms. Given that most pancreatic tumors exhibit a highly metabolic phenotype, we examined the effects of BPM 31510 employing in vitro and in vivo PanCa models. BPM 31510 is a metabolic-modulating agent that reverses the Warburg effect and is currently in clinical development for solid tumors alone and in combination with chemotherapy. Determination of BPM 31510 IC50 values in vitro demonstrated the PanCa cell lines MIA PaCa-2 and Panc-1 cells were significantly more sensitive to BPM 31510 (IC50 = 137 and 455 μM, respectively) compared to primary fibroblasts (IC50 = 1537 μM). IC50 and IC90 doses of BPM 31510 also decreased the viable cell population while concomitantly increasing Annexin V- and PI-positive populations in both PanCa cell types, indicating BPM 31510 induces programmed cell death. Furthermore, in combination with gemcitabine (0.1-5 μM), BPM 31510 (100 μM) decreased cell viability by more than 75% compared to either treatment alone. In vivo, treatment of MIA PaCa-2 tumor-bearing mice with increasing doses of BPM 31510 (0.5-50 mg/kg IP, 3X/week) significantly improved median survival in a dose-dependent manner, with the highest dose extending median survival by more than 36 days compared to saline control. Moreover, while median survival of MIA PaCa-2 tumor-bearing mice treated with BPM 31510 (50 mg/kg IP, 1X/day) or gemcitabine (150 mg/kg IV, 1X/week, given on cycles, 3 weeks on 1 week) monotherapy was 77 and 63 days, respectively, combination treatment resulted in median survival improvement to 113.5 days. Examination of alternative dosing regimens revealed that more frequent dosing of BPM 31510 (2X or 3X/day) alone and in combination with gemcitabine further extended median survival in this model. The preliminary mechanistic insight into additive efficacy of combination treatment was explored in vitro. BPM 31510 treatment alone significantly altered multiple aspects of mitochondrial function in MIA PaCa-2 cells, indicating that BPM 31510-driven bioenergetic alterations are separate from the effects of gemcitabine. Hence, these data demonstrate that BPM 31510 has a potent anti-cancer activity alone and in combination with standard-of-care chemotherapy in preclinical PanCa models.

Citation Format: Tulin Dadali, Anne R. Diers, Arleide Lee, Rakibou Ouro-Djobo, Justin Bourdelais, Ezer Benaim, Bianca Jambhekar, Tony E. Walshe, Joaquin J. Jimenez, Vivek K. Vishnudas, Rangaprasad Sarangarajan, Niven R. Narain. BPM 31510 enhances efficacy of gemcitabine through orthogonal mechanisms in a preclinical model of pancreatic adenocarcinoma. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr C117.

Abstract 3488: BPM 31510 has broad utility as both a single agent and in combination with standard-of-care chemotherapy in triple-negative breast cancer

Deregulated metabolism is recognized as a ‘hallmark of cancer’ although our understanding of the interplay between metabolic pathway activity and responses to standard-of-care chemotherapy remains limited. In vitro studies have demonstrated that BPM 31510, a Coenzyme Q10-containing proprietary formulation, alters both glycolysis and mitochondrial OXPHOS in cancer cells. Building on the clinical observation that triple-negative breast cancer (TNBC) is distinctly glycolytic compared to other breast sub-types, we examined the effects of BPM 31510 alone and in combination with standard-of-care chemotherapy in a murine xenograft model of TNBC (MDA-MB231). Tumor-bearing mice were treated with cycles of the standard ‘TAC regimen’ (5mg/kg docetaxel and 1 mg/kg doxorubicin for 3 days followed by 35 mg/kg cyclophosphamide) with or without BPM 31510 every 3 weeks. As expected, chemotherapy treatment extended survival. Notably, BPM 31510 was more effective as a single agent compared to traditional chemotherapy and extended survival by more than 6 weeks. The combination of BPM 31510 with chemotherapy further enhanced survival over either treatment regimen alone, and this was associated with attenuated tumor growth over the duration of the study. Analysis of a subset of tumors after 2 cycles of treatment confirmed a decrease in tumor weight in all treatment conditions compared to control and a significant synergistic effect of combined therapy (p = 0.02). Importantly, changes were not observed in the weight of other organs from the same mice, suggesting lack of systemic toxicity. Evidence of decreased proliferation (Ki67 staining) and enhanced caspase activity were also observed in tumors by immunohistochemical analysis. Assessment of the BPM 31510 IC50 in vitro using a panel of primary human mammary epithelial cells (HMEC), non-tumorigenic (MCF12A), and breast cancer cell lines demonstrated selective cytotoxicity in cancer cells compared to primary and non-tumorigenic cells. Moreover, MDA-MB231 was the most sensitive to BPM 31510-induced cell death in the breast cancer cell panel that was representative of multiple breast tumor sub-types. Taken together, these data demonstrate that the metabolic modulating agent BPM 31510 has broad utility as both a single agent and in combination with standard-of-care in breast cancer including distinctly glycolytic TNBC for which prognosis is poor and few therapeutic options exist.

Citation Format: Niven R. Narain, Anne R. Diers, Arleide Lee, Rakibou Ouro-Djobo, Vivek K. Vishnudas, Ely Benaim, Joaquin J. Jimenez, Rangaprasad Sarangarajan. BPM 31510 has broad utility as both a single agent and in combination with standard-of-care chemotherapy in triple-negative breast cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3488. doi:10.1158/1538-7445.AM2015-3488

Abstract 3051: Functional bioenergetic signature predicts therapeutic responses to BPM 31510

Unlike personalized strategies to target actionable gene mutations, predicting patient responses to metabolism-targeted therapies requires a phenomic - as opposed to genomic - approach to patient stratification. BPM 31510 is a propriety, ubidecarenone-containing formulation that alters mitochondrial bioenergetics and is currently in clinical trials for treatment of solid tumors. Here, we sought to identify a functional bioenergetic signature which predicts therapeutic responses to BPM 31510 using an in vitro pan-cancer model. BPM 31510 displayed anti-cancer activity across a range of cancer cell lines including those derived from breast, prostate, pancreatic, and hepatocellular carcinoma tumors with IC50 values in the μM range (137-922 μM) comparable to circulating levels achieved in clinical trial patients. For each anatomical site, selective cytotoxicity was observed in cancer cell lines compared to their respective non-tumorigenic controls. Whether mutational status is associated with response to BPM 31510 was assessed using hybrid capture sequencing data from the publically-available Cancer Cell Line Encyclopedia; however, a lack of correlation was observed across all 50 ‘driver’ mutations assessed including TP53 (breast), ETV1 (prostate), and KRAS (pancreatic). In addition, sensitivity to BPM 31510 was not correlated with proliferation rate (R2 = 0.0005), in contrast to the well-established relationship for many standard-of-care chemotherapeutic agents, suggesting that sensitivity to BPM 31510 is governed by alternative mechanisms. Using whole-cell integrated energy metabolism parameters coupled with mitochondrial substrate-level oxidation measurements, we identified cancer cell types with high glycolytic flux and low mitochondrial respiration as particularly sensitive to BPM 31510-induced cell death (R2 = 0.6140 and 0.9557, respectively). Moreover, assessment of substrate-specific oxidation of mitochondrial substrates (e.g., pyruvate, glutamate, succinate, palmitoyl carnitine, β-hydroxy-butyrate) and subsequent bioinformatics analysis revealed additional stratification parameters and a predictive functional bioenergetic signature for therapeutic responses to BPM 31510. Taken together, these data demonstrate that the anti-cancer effects of BPM 31510 are not governed by mutational status, nor proliferative capacity, but instead are dictated by the functional bioenergetic status of cancer cells. Our findings also highlight the importance of phenotypic stratification approaches to complement those at the level of the genome, particularly in the setting of anti-metabolic cancer therapies.

Citation Format: Anne R. Diers, Michael A. Kiebish, Arleide Lee, Rakibou Ouro-Djobo, Stephane Gesta, Vivek K. Vishnudas, Rangaprasad Sarangarajan, Niven R. Narain. Functional bioenergetic signature predicts therapeutic responses to BPM 31510. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3051. doi:10.1158/1538-7445.AM2015-3051

Inhibition of an NAD⁺ salvage pathway provides efficient and selective toxicity to human pluripotent stem cells

The tumorigenic potential of human pluripotent stem cells (hPSCs) is a major limitation to the widespread use of hPSC derivatives in the clinic. Here, we demonstrate that the small molecule STF-31 is effective at eliminating undifferentiated hPSCs across a broad range of cell culture conditions with important advantages over previously described methods that target metabolic processes. Although STF-31 was originally described as an inhibitor of glucose transporter 1, these data support the reclassification of STF-31 as a specific NAD⁺ salvage pathway inhibitor through the inhibition of nicotinamide phosphoribosyltransferase (NAMPT). These findings demonstrate the importance of an NAD⁺ salvage pathway in hPSC biology and describe how inhibition of NAMPT can effectively eliminate hPSCs from culture. These results will advance and accelerate the development of safe, clinically relevant hPSC-derived cell-based therapies.

A novel class of mitochondria-targeted soft electrophiles modifies mitochondrial proteins and inhibits mitochondrial metabolism in breast cancer cells through redox mechanisms

Despite advances in screening and treatment over the past several years, breast cancer remains a leading cause of cancer-related death among women in the United States. A major goal in breast cancer treatment is to develop safe and clinically useful therapeutic agents that will prevent the recurrence of breast cancers after front-line therapeutics have failed. Ideally, these agents would have relatively low toxicity against normal cells, and will specifically inhibit the growth and proliferation of cancer cells. Our group and others have previously demonstrated that breast cancer cells exhibit increased mitochondrial oxygen consumption compared with non-tumorigenic breast epithelial cells. This suggests that it may be possible to deliver redox active compounds to the mitochondria to selectively inhibit cancer cell metabolism. To demonstrate proof-of-principle, a series of mitochondria-targeted soft electrophiles (MTSEs) has been designed which selectively accumulate within the mitochondria of highly energetic breast cancer cells and modify mitochondrial proteins. A prototype MTSE, IBTP, significantly inhibits mitochondrial oxidative phosphorylation, resulting in decreased breast cancer cell proliferation, cell attachment, and migration in vitro. These results suggest MTSEs may represent a novel class of anti-cancer agents that prevent cancer cell growth by modification of specific mitochondrial proteins.

Cancer cell metabolism and the modulating effects of nitric oxide

Altered metabolic phenotype has been recognized as a hallmark of tumor cells for many years, but this aspect of the cancer phenotype has come into greater focus in recent years. NOS2 (inducible nitric oxide synthase of iNOS) has been implicated as a component in many aggressive tumor phenotypes, including melanoma, glioblastoma, and breast cancer. Nitric oxide has been well established as a modulator of cellular bioenergetics pathways, in many ways similar to the alteration of cellular metabolism observed in aggressive tumors. In this review we attempt to bring these concepts together with the general hypothesis that one function of NOS2 and NO in cancer is to modulate metabolic processes to facilitate increased tumor aggression. There are many mechanisms by which NO can modulate tumor metabolism, including direct inhibition of respiration, alterations in mitochondrial mass, oxidative inhibition of bioenergetic enzymes, and the stimulation of secondary signaling pathways. Here we review metabolic alterations in the context of cancer cells and discuss the role of NO as a potential mediator of these changes.

Abstract 3358: Significant increase in survival of triple negative breast cancer animal model in response to BPM31510 alone or in combination with standard of care: BPM31510 mediated dynamic metabolic (Warburg) shift in breast cancer as potential mechanism

This study demonstrates that BPM 31510, a Coenzyme Q10 containing proprietary formulation to influences cellular metabolism that is deregulated in cancers and is now considered to be a “hallmark of cancer”. These studies demonstrate that BPM 31510 alone or in combination with standard of care significantly improved survival of triple negative breast cancer (TNBC) animal model. To further tease out beneficial effects of BPM31510, human breast cancer cells of varying receptor status (SKBR3, MDA-MB231) were subjected to either (a) pretreatment with BPM 31510 (6 h) followed co-incubation with chemotherapeutic agents for 48-72 h or (b) co-treatment with BPM 31510 and chemotherapeutic agents, and cancer cell responses were compared to non-tumorigenic mammary cells (MCF12A). Cellular bioenergetics profiling revealed that BPM 31510 shifted cellular metabolism from glycolysis to mitochondrial metabolism, and this metabolic shift was associated with significant increases in reactive oxygen species (ROS). Both BPM 31510 alone or pretreatment and cotreatment strategies with BPM 31510 plus standard of care resulted in significant decreases in viable breast cancer cells when compared to chemotherapeutic agents; however, minimal effects were observed in MCF12A cells. In contrast, BPM 31510 in combination with chemotherapeutic agents amplified caspase 3 activation and apoptotic cell death, indicating BPM 31510 enhances apoptotic signaling. Taken together, these data demonstrate that BPM 31510 is a novel agent that reengages the cellular metabolic and apoptotic machinery of cancer cells independent of genetic make-up underlying malignancy. In addition, BPM 31510 enhances the cytotoxicity of standard-of-care chemotherapeutic agents in breast cancer cells through regulation of mitochondrial metabolism and oxidative stress. These findings confirm that BPM 31510 is a novel, paradigm shifting agent with multiple utility (as a single agent or in combination) in breast cancer including TNBCs that otherwise have poor prognosis and limited therapeutic options.

Citation Format: Niven R. Narain, Anne R. Diers, Tony E. Walshe, Arleide Lee, Rakib Ouro-Djobo, Vivek K. Vishnudas, Ely Benaim, Rangaprasad Sarangarajan. Significant increase in survival of triple negative breast cancer animal model in response to BPM31510 alone or in combination with standard of care: BPM31510 mediated dynamic metabolic (Warburg) shift in breast cancer as potential mechanism. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3358. doi:10.1158/1538-7445.AM2014-3358

S-Nitrosation of monocarboxylate transporter 1: inhibition of pyruvate-fueled respiration and proliferation of breast cancer cells

Energy substrates metabolized through mitochondria (e.g., pyruvate, glutamine) are required for biosynthesis of macromolecules in proliferating cells. Because several mitochondrial proteins are known to be targets of S-nitrosation, we determined whether bioenergetics are modulated by S-nitrosation and defined the subsequent effects on proliferation. The nitrosating agent S-nitroso-L-cysteine (L-CysNO) was used to initiate intracellular S-nitrosation, and treatment decreased mitochondrial function and inhibited proliferation of MCF7 mammary adenocarcinoma cells. Surprisingly, the d-isomer of CysNO (D-CysNO), which is not transported into cells, also caused mitochondrial dysfunction and limited proliferation. Both L- and D-CysNO also inhibited cellular pyruvate uptake and caused S-nitrosation of thiol groups on monocarboxylate transporter 1, a proton-linked pyruvate transporter. These data demonstrate the importance of mitochondrial metabolism in proliferative responses in breast cancer and highlight a novel role for inhibition of metabolic substrate uptake through S-nitrosation of exofacial protein thiols in cellular responses to nitrosative stress.

Metastasis suppressor KISS1 seems to reverse the Warburg effect by enhancing mitochondrial biogenesis

Cancer cells tend to utilize aerobic glycolysis even under normoxic conditions, commonly called the "Warburg effect." Aerobic glycolysis often directly correlates with malignancy, but its purpose, if any, in metastasis remains unclear. When wild-type KISS1 metastasis suppressor is expressed, aerobic glycolysis decreases and oxidative phosphorylation predominates. However, when KISS1 is missing the secretion signal peptide (ΔSS), invasion and metastasis are no longer suppressed and cells continue to metabolize using aerobic glycolysis. KISS1-expressing cells have 30% to 50% more mitochondrial mass than ΔSS-expressing cells, which are accompanied by correspondingly increased mitochondrial gene expression and higher expression of PGC1α, a master coactivator that regulates mitochondrial mass and metabolism. PGC1α-mediated downstream pathways (i.e., fatty acid synthesis and β-oxidation) are differentially regulated by KISS1, apparently reliant upon direct KISS1 interaction with NRF1, a major transcription factor involved in mitochondrial biogenesis. Since the downstream effects could be reversed using short hairpin RNA to KISS1 or PGC1α, these data appear to directly connect changes in mitochondria mass, cellular glucose metabolism, and metastasis.

Detection of S-nitrosothiols

BACKGROUND

S-nitrosothiols have been recognized as biologically-relevant products of nitric oxide that are involved in many of the diverse activities of this free radical.

SCOPE OF REVIEW

This review serves to discuss current methods for the detection and analysis of protein S-nitrosothiols. The major methods of S-nitrosothiol detection include chemiluminescence-based methods and switch-based methods, each of which comes in various flavors with advantages and caveats.

MAJOR CONCLUSIONS

The detection of S-nitrosothiols is challenging and prone to many artifacts. Accurate measurements require an understanding of the underlying chemistry of the methods involved and the use of appropriate controls.

GENERAL SIGNIFICANCE

Nothing is more important to a field of research than robust methodology that is generally trusted. The field of S-nitrosation has developed such methods but, as S-nitrosothiols are easy to introduce as artifacts, it is vital that current users learn from the lessons of the past. This article is part of a Special Issue entitled Current methods to study reactive oxygen species - pros and cons and biophysics of membrane proteins. Guest Editor: Christine Winterbourn.

Effect of nitric oxide on naphthoquinone toxicity in endothelial cells: role of bioenergetic dysfunction and poly (ADP-ribose) polymerase activation

When produced at physiological levels, reactive oxygen species (ROS) can act as signaling molecules to regulate normal vascular function. Produced under pathological conditions, ROS can contribute to the oxidative damage of cellular components (e.g., DNA and proteins) and trigger cell death. Moreover, the reaction of superoxide with nitric oxide (NO) produces the strong oxidant peroxynitrite and decreases NO bioavailability, both of which may contribute to activation of cell death pathways. The effects of ROS generated from the 1,4-naphthoquinones alone and in combination with NO on the activation status of poly(ADP-ribose) polymerase (PARP) and cell viability were examined. Treatment with redox cycling quinones activates PARP, and this stimulatory effect is attenuated in the presence of NO. Mitochondria play a central role in cell death signaling pathways and are a target of oxidants. We show that simultaneous exposure of endothelial cells to NO and ROS results in mitochondrial dysfunction, ATP and NAD(+) depletion, and cell death. Alone, NO and ROS have only minor effects on cellular bioenergetics. Further, PARP inhibition does not attenuate reduced cell viability or mitochondrial dysfunction. These results show that concomitant exposure to NO and ROS impairs energy metabolism and triggers PARP-independent cell death. While superoxide-mediated PARP activation is attenuated in the presence of NO, PARP inhibition does not modify the loss of mitochondrial function or adenine and pyridine nucleotide pools and subsequent bioenergetic dysfunction. These findings suggest that the mechanisms by which ROS and NO induce endothelial cell death are closely linked to the maintenance of mitochondrial function and not overactivation of PARP.

Abstract 1864: Mitochondrial bioenergetics of metastatic breast cancer cells in response to decreasing oxygen tension

Solid tumors are characterized by regions of low oxygen tension, which play a central role in tumor progression and resistance to therapy. The major organelle affected by reduced oxygen tension is the mitochondrion, which has to functionally adapt to maintain cellular bioenergetics for the cell survival. In the present study, a novel experimental approach was developed to examine the real-time bioenergetic changes during adaptation to various oxygen tensions ranging from 20% to < 1% oxygen using highly sensitive extracellular flux technology. Oxygen was gradually removed from the culture medium, and bioenergetic changes were measured in normal breast epithelial (MCF10A) and metastatic cancer cell lines (MDA-MB-231 and MCF10CA clones). We found that breast cancer cells, but not MCF10A cells, rapidly responded to low oxygen tension by stabilizing HIF-1α, increasing hypoxia responsive gene expression, and stimulating cellular uptake of glucose, confirming previous observations. In addition, breast cancer cells increased extracellular acidification rate (ECAR) or glycolysis during adaptation to low oxygen tension, and this effect was markedly lower in MCF10A cells. Interestingly, breast cancer cells exhibited a biphasic response in oxygen consumption rate (OCR) as the oxygen tension was reduced gradually from 20% to <1.0%, a response not previously described. This effect is HIF-1α-dependent, as silencing HIF-1α function in cancer cells completely abolished the biphasic response in OCR and increase in ECAR. Moreover, cancer cells demonstrated the ability to restore and maintain its OCR steadily at specific oxygen tension either during deoxygenation or reoxygenation, an effect not observed in HIF-1α silenced cells. Additional studies confirmed that the initial stimulation of OCR is due to increased mitochondrial respiration. In conclusion, our results suggest that HIF-1α provides high degree of bioenergetic flexibility under different oxygen tensions which may confer an adaptive advantage in the ever-changing tumor microenvironment as well as during invasion and metastasis. Moreover, these differences may be useful in screening novel therapeutic agents that target the bioenergetics of cancer cells in response to low oxygen tension.

Citation Format: Praveen K. Vayalil, Anne R. Diers, Claudia R. Olivia, Corinne E. Griguer, Victor Darley-Usmar, Douglas R. Hurst, Danny R. Welch, Aimee Landar. Mitochondrial bioenergetics of metastatic breast cancer cells in response to decreasing oxygen tension. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1864. doi:10.1158/1538-7445.AM2013-1864

Abstract 3866: The KISS1 metastasis suppressor appears to reverse the Warburg effect by enhancing mitochondria biogenesis

Cancer cells tend to utilize aerobic glycolysis even under normoxic conditions, which is commonly called the “Warburg Effect.” Aerobic glycolysis often directly correlates with malignant potential. Though its purpose remains unclear, the “Warburg Effect” is thought to confer advantages to proliferation, survival and dissemination to cancer cells by increasing uptake of nutrients into biomass. KISS1 protein is secreted and proteolytically cleaved into kisspeptins (KP) that block the colonization of disseminated metastatic C8161.9 human melanoma cells at secondary sites. In this study, we hypothesized that KISS1 metastasis suppression occurs via regulation of aerobic glycolysis. Comparison of bioenergetic and metabolic aspects of glucose metabolism showed that all KISS1-secreting clones were less invasive, took up less glucose, produced less lactate which corresponds to higher pH[Ex], effects which were reversed when cells were transduced with shRNA to KISS1. The metabolism, invasion, and metastasis changes did not occur when KISS1 was missing the signal peptide (ΔSS). Utilizing a Seahorse bioanalyzer, KISS1, but not ΔSS cells showed significantly decreased extracellular acidification rates, increased O2 consumption and elevated mitochondria reserve capacity, an indicator of mitochondrial condition and a parameter thought to improve the cells’ ability to cope with oxidative stress. KISS1-expressing cells have 30-50% more mitochondria compared to vector or ΔSS-expressing cells. Increased mitochondrial mass was accompanied by significantly increased expression of mitochondrial genes involved in apoptosis and mitophagy, protein processing and trafficking. Increased mitochondrial mass correlated with higher PGC1α considered to be a master co-activator that regulates mitochondrial mass and metabolism. Interestingly, KISS1 differentially affects PGC1α-mediated downstream pathways, i.e. fatty acid synthesis and β-oxidation. KISS1-mediated up-regulation of mitochondria biogenesis appears to rely on KISS1 interaction with NRF1, a major transcription factor of mitochondria biogenesis. KP10 (which can activate the KISS1 receptor) does not alter pH[Ex] since the metastatic tumor cells do not express KISS1R. This paradox - metastasis and metabolic changes require secretion, but responding cells do not have the receptor - raises questions regarding the mechanism. Nonetheless, these data appear to directly connect changes in mitochondria mass, cellular glucose metabolism and metastasis. [Support: CA134581, Natl. Fndn. Cancer Res., Komen SAC110037].

Citation Format: Wen Liu, Benjamin H. Beck, Kedar S. Vaidya, Kevin T. Nash, Anne R. Diers, Kyle P. Feeley, Aimee Landar, Scott W. Ballinger, Danny R. Welch. The KISS1 metastasis suppressor appears to reverse the Warburg effect by enhancing mitochondria biogenesis. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3866. doi:10.1158/1538-7445.AM2013-3866

S-nitrosoglutathione

BACKGROUND

S-Nitrosoglutathione (GSNO) is the S-nitrosated derivative of glutathione and is thought to be a critical mediator of the down stream signaling effects of nitric oxide (NO). GSNO has also been implicated as a contributor to various disease states.

SCOPE OF REVIEW

This review focuses on the chemical nature of GSNO, its biological activities, the evidence that it is an endogenous mediator of NO action, and implications for therapeutic use.

MAJOR CONCLUSIONS

GSNO clearly exerts its cellular actions through both NO- and S-nitrosation-dependent mechanisms; however, the chemical and biological aspects of this compound should be placed in the context of S-nitrosation as a whole.

GENERAL SIGNIFICANCE

GSNO is a central intermediate in formation and degradation of cellular S-nitrosothiols with potential therapeutic applications; thus, it remains an important molecule of study. This article is part of a Special Issue entitled Cellular functions of glutathione.

Nitrosative stress and redox-cycling agents synergize to cause mitochondrial dysfunction and cell death in endothelial cells

Nitric oxide production by the endothelium is required for normal vascular homeostasis; however, in conditions of oxidative stress, interactions of nitric oxide with reactive oxygen species (ROS) are thought to underlie endothelial dysfunction. Beyond canonical nitric oxide signaling pathways, nitric oxide production results in the post-translational modification of protein thiols, termed S-nitrosation. The potential interplay between S-nitrosation and ROS remains poorly understood and is the focus of the current study. The effects of the S-nitrosating agent S-nitrosocysteine (CysNO) in combination with redox-cycling agents was examined in bovine aortic endothelial cells (BAEC). CysNO significantly impairs mitochondrial function and depletes the NADH/NAD⁺ pool; however, these changes do not result in cell death. When faced with the additional stressor of a redox-cycling agent used to generate ROS, further loss of NAD⁺ occurs, and cellular ATP pools are depleted. Cellular S-nitrosothiols also accumulate, and cell death is triggered. These data demonstrate that CysNO sensitizes endothelial cells to redox-cycling agent-dependent mitochondrial dysfunction and cell death and identify attenuated degradation of S-nitrosothiols as one potential mechanism for the enhanced cytotoxicity.

Oxidative modification of proteins: an emerging mechanism of cell signaling

There are a wide variety of reactive species which can affect cell function, including reactive oxygen, nitrogen, and lipid species. Some are formed endogenously through enzymatic or non-enzymatic pathways, and others are introduced through diet or environmental exposure. Many of these reactive species can interact with biomolecules and can result in oxidative post-translational modification of proteins. It is well documented that some oxidative modifications cause macromolecular damage and cell death. However, a growing body of evidence suggests that certain classes of reactive species initiate cell signaling by reacting with specific side chains of peptide residues without causing cell death. This process is generally termed "redox signaling," and its role in physiological and pathological processes is a subject of active investigation. This review will give an overview of oxidative protein modification as a mechanism of redox signaling, including types of reactive species and how they modify proteins, examples of modified proteins, and a discussion about the current concepts in this area.

Subsets of ATP-sensitive potassium channel (KATP) inhibitors increase gap junctional intercellular communication in metastatic cancer cell lines independent of SUR expression

Gap junctional intercellular communication (GJIC) regulates cellular homeostasis by propagating signaling molecules, exchanging cellular metabolites, and coupling electrical signals. In cancer, cells exhibit altered rates of GJIC which may play a role in neoplastic progression. K(ATP) channels help maintain membrane polarity and linkages between K(ATP) channel activity and rates of GJIC have been established. The mechanistic relationship has not been fully elucidated. We report the effects of treatment with multiple K(ATP) antagonist compounds on GJIC in metastatic cell lines demonstrating an increase in communication rates following treatment with compounds possessing specificities towards the SUR2 subunit of K(ATP). These effects remained consistent using cell lines with different expression levels of SUR1 and SUR2, suggesting possible off target effects on GJIC by these compounds.

Assessing bioenergetic function in response to oxidative stress by metabolic profiling

It is now clear that mitochondria are an important target for oxidative stress in a broad range of pathologies, including cardiovascular disease, diabetes, neurodegeneration, and cancer. Methods for assessing the impact of reactive species on isolated mitochondria are well established but constrained by the need for large amounts of material to prepare intact mitochondria for polarographic measurements. With the availability of high-resolution polarography and fluorescence techniques for the measurement of oxygen concentration in solution, measurements of mitochondrial function in intact cells can be made. Recently, the development of extracellular flux methods to monitor changes in oxygen concentration and pH in cultures of adherent cells in multiple-sample wells simultaneously has greatly enhanced the ability to measure bioenergetic function in response to oxidative stress. Here we describe these methods in detail using representative cell types from renal, cardiovascular, nervous, and tumorigenic model systems while illustrating the application of three protocols to analyze the bioenergetic response of cells to oxidative stress.

Differential regulation of metabolism by nitric oxide and S-nitrosothiols in endothelial cells

S-nitrosation of thiols in key proteins in cell signaling pathways is thought to be an important contributor to nitric oxide (NO)-dependent control of vascular (patho)physiology. Multiple metabolic enzymes are targets of both NO and S-nitrosation, including those involved in glycolysis and oxidative phosphorylation. Thus it is important to understand how these metabolic pathways are integrated by NO-dependent mechanisms. Here, we compared the effects of NO and S-nitrosation on both glycolysis and oxidative phosphorylation in bovine aortic endothelial cells using extracellular flux technology to determine common and unique points of regulation. The compound S-nitroso-L-cysteine (L-CysNO) was used to initiate intracellular S-nitrosation since it is transported into cells and results in stable S-nitrosation in vitro. Its effects were compared with the NO donor DetaNONOate (DetaNO). DetaNO treatment caused only a decrease in the reserve respiratory capacity; however, L-CysNO impaired both this parameter and basal respiration in a concentration-dependent manner. In addition, DetaNO stimulated extracellular acidification rate (ECAR), a surrogate marker of glycolysis, whereas L-CysNO stimulated ECAR at low concentrations and inhibited it at higher concentrations. Moreover, a temporal relationship between NO- and S-nitrosation-mediated effects on metabolism was identified, whereby NO caused a rapid impairment in mitochondrial function, which was eventually overwhelmed by S-nitrosation-dependent processes. Taken together, these results suggest that severe pharmacological nitrosative stress may differentially regulate metabolic pathways through both intracellular S-nitrosation and NO-dependent mechanisms. Moreover, these data provide insight into the role of NO and related compounds in vascular (patho)physiology.

Methaemalbumin formation in sickle cell disease: effect on oxidative protein modification and HO-1 induction

Normally, cell free haemoglobin is bound by haptoglobin and efficiently cleared. However, the chronic haemolysis in sickle cell disease (SCD) overwhelms haptoglobin binding capacity and protein turnover, resulting in elevated cell free haemoglobin. Cell free haemoglobin acts as both a scavenger of vasoactive nitric oxide and a pro-oxidant. In addition, methaemoglobin (metHb) releases the haem moiety, which can bind to albumin to form methaemalbumin (metHSA). This study used electron paramagnetic resonance to detect metHSA in SCD plasma and demonstrated that haptoglobin prevents haem transfer from metHb to HSA. MetHSA may either provide a second line of defence against haemoglobin/haem-mediated oxidation or contribute to the pro-oxidant environment of SCD plasma. We demonstrated that HSA inhibited oxidative protein modification induced by metHb. Additionally, we showed that while metHb induced haem oxygenase 1 (HO-1), an indicator of oxidative stress, HSA attenuated metHb induction of this enzyme, thereby limiting the potential benefits of HO-1. Furthermore, HO-1 induction by metHSA was less than HO-1 induction by equimolar metHb not bound to albumin. Our findings confirm the presence of metHSA in SCD and suggest that haem transfer from metHb to HSA reduces the oxidative effects of free haemoglobin/haem on endothelium with both beneficial (reduced protein oxidation) and potentially harmful (reduced HO-1 induction) outcomes.

Abstract 965: The KISS1 metastasis suppressor appears to reverse the ‘Warburg Effect’

In 1924, Otto Warburg described the preference of cancer cells for glycolytic metabolism, even under normoxic conditions and that these metabolic changes directly correlate with malignant potential of several cancers. Although its purpose remains unclear, the “Warburg Effect” is thought to confer proliferative and survival advantages by increasing uptake of nutrients into biomass. The KISS1 metastasis suppressor protein is secreted and proteolytically cleaved into so-called kisspeptins (KP) that block the colonization of metastatic C8161.9 human melanoma cells at secondary sites. We asked whether secreted KISS1 mediates its inhibitory effects on metastatic growth through regulation of the “Warburg Effect.” Comparing multiple bioenergetic and metabolic aspects of glucose metabolism in C8161.9 ± KISS1 showed that all KISS1-secreting clones had significantly (P<0.05) reduced invasion (60%) and reduced lactate production (100 mg/dL vs. 128 mg/dL). Irrespective of cell density, KISS1-expressing cells had a significantly higher extracellular pH (pHe=7.2) compared to cells transfected with empty vector or cells transfected with KISS1 harboring a deleted signal sequence (ΔSS; pHe=6.7). Utilizing a Seahorse® bioanalyzer, reduced extracellular acidification by KISS1 cells was verified concomitant with increased O2 consumption. Interestingly, mitochondrial reserve capacity, an indicator thought to reflect a cell's ability to cope with oxidative stresses, was also elevated in KISS1-expressing cells. Using mitochondrial-selective fluorescent probes, C8161.9KISS1 melanoma and MDA-MB-435KISS1 breast carcinoma cells have ∼30% more mitochondria compared to empty vector or KISS1ΔSS-expressing cells. Increased mitochondrial number in KISS1-expressing cells was correlated with higher levels of PGC-1α, a major mitochondrial biogenesis regulatory molecule, which was confirmed using siRNA to KISS1. Expression of KISS1 also protected C8161.9 cells from dichloroacetate-induced cell death. Unexpectedly, addition of KP10 to C8161.9 cells did not alter pHe, raising questions regarding the mechanism by which KISS1/KP alter PGC-1α in the absence of KISS1 receptor expression in the tumor cells. Nonetheless, these data appear to directly connect changes in mitochondrial number, metabolic pathway regulation and the metastatic process. Future studies will determine whether the increase in mitochondrial number is directly responsible for the change in glycolytic metabolism and whether these changes are necessary for KISS1's effects on metastatic growth. Support: RO1-CA134981, the National Foundation for Cancer Research, METAvivor, and UAB Med-into-Grad Fellowship.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 965. doi:10.1158/1538-7445.AM2011-965

Homotypic gap junctional communication associated with metastasis suppression increases with PKA activity and is unaffected by PI3K inhibition

Loss of gap junctional intercellular communication (GJIC) between cancer cells is a common characteristic of malignant transformation. This communication is mediated by connexin proteins that make up the functional units of gap junctions. Connexins are highly regulated at the protein level and phosphorylation events play a key role in their trafficking and degradation. The metastasis suppressor breast cancer metastasis suppressor 1 (BRMS1) upregulates GJIC and decreases phosphoinositide-3-kinase (PI3K) signaling. On the basis of these observations, we set out to determine whether there was a link between PI3K and GJIC in tumorigenic and metastatic cell lines. Treatment of cells with the well-known PI3K inhibitor LY294002, and its structural analogue LY303511, which does not inhibit PI3K, increased homotypic GJIC; however, we found the effect to be independent of PI3K/AKT inhibition. We show in multiple cancer cell lines of varying metastatic capability that GJIC can be restored without enforced expression of a connexin gene. In addition, while levels of connexin 43 remained unchanged, its relocalization from the cytosol to the plasma membrane was observed. Both LY294002 and LY303511 increased the activity of protein kinase A (PKA). Moreover, PKA blockade by the small molecule inhibitor H89 decreased the LY294002/LY303511-mediated increase in GJIC. Collectively, our findings show a connection between PKA activity and GJIC mediated by PI3K-independent mechanisms of LY294002 and LY303511. Manipulation of these signaling pathways could prove useful for antimetastatic therapy.

Mitochondrial electron transport chain blockers enhance 2-deoxy-D-glucose induced oxidative stress and cell killing in human colon carcinoma cells

Increasing evidence suggests that cancer cells (relative to normal cells) have altered mitochondrial electron transport chains (ETC) that are more likely to form reactive oxygen species (ROS; i.e., O(2)(*-) and H(2)O(2)) resulting in a condition of chronic metabolic oxidative stress, that maybe compensated for by increasing glucose and hydroperoxide metabolism. In the current study, the ability of an inhibitor of glucose metabolism, 2-deoxy-D-glucose (2DG), combined with mitochondrial electron transport chain blockers (ETCBs) to enhance oxidative stress and cytotoxicity was determined in human colon cancer cells. Treatment of HT29 and HCT116 cancer cells with Antimycin A (Ant A) or rotenone (Rot) increased carboxy-dichlorodihydrofluorescein diacetate (H2DCFDA) and dihydroethidine (DHE) oxidation, caused the accumulation of glutathione disulfide and enhanced 2DG-induced cell killing. In contrast, Rot did not enhance the toxicity of 2DG in normal human fibroblasts supporting the hypotheses that cancer cells are more susceptible to inhibition of glucose metabolism in the presence of ETCBs. In addition, 2-methoxy-antimycin A (Meth A; an analog of Ant A that does not have ETCB activity) did not enhance 2DG-induced DHE oxidation or cytotoxicity in cancer cells. Finally, in HT29 tumor bearing mice treated with the combination of 2DG (500 mg/kg) + Rot (2 mg/kg) the average rate of tumor growth was significantly slower when compared to control or either drug alone. These results show that 2DG-induced cytotoxicity and oxidative stress can be significantly enhanced by ETCBs in human colon cancer cells both in vitro and in vivo.