Aging induces changes in cancer formation and microbial content in a murine model of bladder cancer

Bladder cancer (BCa) incidence is tightly linked to aging. Older patients with BCa present with higher grade tumors and have worse outcomes on Bacillus-Calmette-Guerin (BCG) immunotherapy. Aging is also known to result in changes in the gut microbiome over mammalian lifespan, with recent studies linking alterations in the gut microbiome to changes in tumor immunity. There is limited information on the microbiome in BCa models though, despite known links to aging and immunotherapy. The purpose of this study was to evaluate how aging impacts tumor formation, inflammation, and the microbiome of mice given the model BCa carcinogen N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN). We hypothesized old animals would have larger, more inflamed tumors and a shift in their fecal microbiome compared to their younger counterparts. Young (~8-week-old) or old (~78-week-old) C57Bl/6J animals were administered 0.05% BBN in drinking water for 16 weeks and then euthanized or allowed to progress for an additional 4 weeks. After 16 weeks of BBN, old mice had higher bladder to body weight ratio than young mice, and also muscle invasive tumors, which were not seen in their young counterparts. Old animals also had increased innate immune recruitment, but CD4+/CD8+ T cell recruitment did not appear different. BBN dramatically altered the microbiome in both sets of animals as measured by ß-diversity, including changes in multiple genera of bacteria. These data suggest old mice have a differential response to BBN-induced BCa. Given the median age of patients with BCa, understanding how the aged phenotype interacts with BCa is imperative.

Abstract 2119: Intravenous vitamin C therapy for cisplatin ineligible bladder cancer patients (CI-MIBC): Early investigation into potential pharmacodynamic biomarkers

Neoadjuvant cisplatin based chemotherapy is considered standard of care for patients with locally advanced bladder cancer (BCa). However, upwards of 50% of patients are ineligible due to poor performance status, underlying kidney disease, peripheral neuropathy, hearing loss and/or cardiac disease. There are currently no accepted alternative regimens with significant activity, and many cisplatin ineligible patients usually proceed directly to surgery. Prior research in other cancers has indicated intravenous vitamin C (IVC), or ascorbate, may serve as a beneficial adjuvant to less toxic therapeutic regimens. We initiated a single arm, Simon 2-stage, Window of Opportunity trial using high dose IVC with single cycle gemcitabine/carboplatin (GCa) (NCT04046094). The primary outcome was pathologic downstaging. Twelve patients with newly diagnosed CI-MIBC were enrolled. Patients received single cycle GCa and IVC titrated to 350-400 mg/dL for ~21 days followed by cystectomy after ~4-6 weeks. As reported, pathological downstaging (<ypT2N0Mx) was present in 4 (33%) of patients. Three of the four patients had a complete response (ypT0NoMx) including one patient with plasmacytoid variant histology. Treatment was well tolerated with no attributable AE/SAEs. Given the discrepancy in response levels, we began identifying potential markers of pharmacodynamic efficacy to inform future trials. Novel data evaluating Ki67+ cells by immunohistochemistry indicate widespread proliferation in non-responders to IVC/GCa, whereas responding patients had visibly fewer positive cells, suggesting a direct effect on cell death and proliferation. TUNEL staining was present in all samples, although often minimally, and thus TUNEL may not yield enough signal to reliably make determinations about treatment outcomes. Urinary cytokine values were assessed using multiplex ELISA and reported as pg/mL urine. Multiple cytokines including IL-1RA, CCL2, IL-8, CXCL10 were present at markedly high concentrations in patients with BCa. Cytokine levels generally increased between diagnostic resection and radical cystectomy indicating potential immune activation by the IVC/GCa treatment. Cytokine levels generally fell between radical cystectomy and follow-up samples suggesting resolution of inflammation after cystectomy. In conclusion, IVC/GCa may be a viable alternative neoadjuvant treatment strategy for patients with BCa that are ineligible for cisplatin-based chemotherapy. Identifying biomarkers of response remains a major area of interest to refine study designs and identify patients most likely to benefit from therapy.

Citation Format: Benjamin L. Woolbright, Ganeshkumar Rajendran, Erika Abbott, Zeb Zacharias, Jon Houtman, Rahul Parikh, Qi Chen, Ameer Hamza, Elizabeth Wulff-Burchfield, Jeffrey M. Holzbeierlein, Jeanne Drisko, Michael D. Henry, John A. Taylor. Intravenous vitamin C therapy for cisplatin ineligible bladder cancer patients (CI-MIBC): Early investigation into potential pharmacodynamic biomarkers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2119.

Pyruvate Dehydrogenase Kinase 4 Deficiency Increases Tumorigenesis in a Murine Model of Bladder Cancer

Pyruvate dehydrogenase kinase 4 (PDK4) is a mitochondrial isozyme in the PDK family (PDK1-4) partially responsible for phosphorylation of pyruvate dehydrogenase (PDH). Phosphorylation of PDH is thought to result in a pro-proliferative shift in metabolism that sustains growth of cancer cells. Previous data from our lab indicate the pan-PDK inhibitor dichloroacetate (DCA) or acute genetic knockdown of PDK4 blocks proliferation of bladder cancer (BCa) cells. The goal of this study was to determine the role of PDK4 in an in vivo BCa model, with the hypothesis that genetic depletion of PDK4 would impair formation of BCa. PDK4−/− or WT animals were exposed to N-Butyl-N-(4-hydroxybutyl) nitrosamine (BBN) for 16 weeks, and tumors were allowed to develop for up to 7 additional weeks. PDK4−/− mice had significantly larger tumors at later time points. When animals were treated with cisplatin, PDK4−/− animals still had larger tumors than WT mice. PDK4 expression was assessed in human tissue and in mice. WT mice lost expression of PDK4 as tumors became muscle-invasive. Similar results were observed in human samples, wherein tumors had less expression of PDK4 than benign tissue. In summary, PDK4 has a complex, multifunctional role in BCa and may represent an underrecognized tumor suppressor.

Role of MIF1/MIF2/CD74 interactions in bladder cancer

Macrophage migration inhibitory factor (MIF1) is a pleiotropic cytokine involved in inflammation and cancer. Genetic knockout of Mif1 in the validated N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN) model of bladder cancer (BCa) resulted in stage arrest at non-muscle-invasive disease in prior studies. Small-molecule inhibition of MIF1 reduced cancer-associated outcomes, but it did not fully recapitulate genetic models. D-dopachrome tautomerase (gene symbol DDT), commonly referred to as MIF2, is a functional homolog of MIF1, and both MIF1 and MIF2 can bind the cell surface receptor CD74 on multiple cell types to initiate a signaling cascade. It has been proposed that this interaction mediates part of the protumorigenic effects of MIF1 and MIF2 and may explain the discordance in prior studies. We hypothesized that MIF2 functions redundantly with MIF1 in BCa development and progression. The Cancer Genome Atlas (TCGA) analysis indicated MIF and DDT expression were increased in BCa patients compared to control. 4-Iodopyridine (4-IPP), a combined MIF1/MIF2 inhibitor, was more efficacious than ISO-1, a MIF1-only inhibitor, in preventing cellular proliferation in BCa cell lines. To evaluate these findings in vivo, wild-type (WT) and Mif1^-/- animals were exposed to 0.05% BBN in drinking water for 16 weeks to initiate tumorigenesis and then evaluated over the subsequent 4 weeks for tumor formation and progression in the presence or absence of 4-IPP. 4-IPP reduced bladder weights in WT animals and bladder weights/tumor stage in Mif1^-/- animals. To determine whether MIF1/MIF2 functioned through CD74 in BCa, WT or Cd74^-/- animals were used in the same BBN model. Although these animals were partially protected against BBN-induced BCa, 4-IPP did not enhance this effect. In conclusion, our data suggest that MIF2 mechanistically functions in a similar protumorigenic manner to MIF1, and this is at least partially through CD74. Dual inhibition of MIF homologs is more efficacious at reducing tumor burden in this model of BCa. © 2022 The Pathological Society of Great Britain and Ireland.

Generation of pro-and anti-inflammatory mediators after acetaminophen overdose in surviving and non-surviving patients

Acetaminophen (APAP) overdose causes liver injury in animals and humans. Although well-studied in animals, limited longitudinal data exist on cytokine release after APAP overdose in patients. The purpose of this study was to quantify concentrations of cytokines in APAP overdose patients to determine if early cytokine or complement measurements can distinguish between surviving and non-surviving patients. Plasma was obtained from healthy controls, APAP overdose patients with no increase in liver transaminases, and surviving and non-surviving APAP overdose patients with severe liver injury. Interleukin-10 (IL-10), and CC chemokine ligand-2 (CCL2, MCP-1) were substantially elevated in surviving and non-surviving patients, whereas IL-6 and CXC chemokine ligand-8 (CXCL8, IL-8) had early elevations in a subset of patients only with liver injury. Day 1 IL-10 and IL-6 levels, and Day 2 CCL2, levels correlated positively with survival. There was no significant increase in IL-1α, IL-1β or TNF-α in any patient during the first week after APAP. Monitoring cytokines such as CCL2 may be a good indicator of patient prognosis; furthermore, these data indicate the inflammatory response after APAP overdose in patients is not mediated by a second phase of inflammation driven by the inflammasome.

Bladder cancer, inflammageing and microbiomes

Ageing is correlated with elevated bladder cancer incidence, morbidity and mortality. Advanced age is also associated with elevated markers of chronic inflammation and perturbations in gut and urinary tract microbiota. One reason for the increased incidence and mortality of bladder cancer in the elderly might be that age-associated changes in multiple microbiomes induce systemic metabolic changes that contribute to immune dysregulation with potentially tumorigenic effects. The gut and urinary microbiomes could be dysregulated in bladder cancer, although the effect of these changes is poorly understood. Each of these domains - the immune system, gut microbiome and urinary microbiome - might also influence the response of patients with bladder cancer to treatment. Improved understanding of age-related alterations to the immune system and gut and urinary microbiomes could provide possible insight into the risk of bladder cancer development and progression in the elderly. In patients with bladder cancer, improved understanding of microbiota might also provide potential targets for therapeutic intervention.

Abstract 3991: Ts65Dn Down syndrome mice reveal a potential therapeutic vulnerability in a BBN bladder cancer model and subset of bladder cancer cell lines

Trisomy 21, Down Syndrome, results in a constellation of symptoms including increased risk for leukemia. In contrast, mounting evidence indicates that people with Down Syndrome have lower rates of numerous solid tumors, particularly carcinogen driven cancers, even when adjusted for age. The mechanisms that dictate why this occurs are not well understood but could potentially yield actionable targets for treating or preventing cancer formation. We hypothesized Ts65Dn mice, a murine model of Down Syndrome, would be protected against BCa formation and could be evaluated as a genetic basis for the discovery of novel therapeutic targets in bladder cancer. Using the well characterized N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN) chemical carcinogen bladder cancer model we initiated tumors in Ts65Dn and WT mice. After 16 weeks BBN exposure, TS65Dn mice were found to have smaller bladder tumors by weight with a trend toward lower stages as compared to WT animals. RNA-sequencing was used to assess broad genomic changes in the tumors. Reactome analysis of the RNA-sequencing data indicated pathways associated with mitosis and the cell cycle were most affected in Ts65Dn mice, including downregulation of pathways associated with Aurora Kinase B (AURKB). AURKB is a pro-tumorigenic kinase known to enhance cell survival and proliferation. Bioinformatics analysis indicates that while AURKB is broadly expressed in most tissues, it is potently upregulated in bladder cancers, offering a potential therapeutic target. Using the AURKB specific inhibitor barasertib-HQPA we evaluated drug sensitivity in a set of BCa cell lines. Cell lines associated with a basal subtype gene signature (5637, HT-1376) were largely susceptible to barasertib with IC50 values in nM concentrations, whereas other BCa cell lines (HTB-5, T24) had IC50 values nearly 1,000X higher. We next assessed histone H3 phosphorylation, a known substrate of AURKB, to validate drug efficacy. Interestingly, inhibition of histone H3 phosphorylation was noted in all cell lines at nM concentrations, indicating that while barasertib is functionally active in both sets of cells, the anti-proliferative activity is not dependent upon phosphorylation of histone H3, but rather other factors that we have yet to determine. In conclusion, we have found Ts65Dn mice have reduced tumor formation when exposed to the BCa carcinogen BBN and furthermore, have identified AURKB as a potential therapeutic target. Use of Ts65Dn mice may be a relevant model for identifying potentially undefined tumorigenic agents in multiple cancers including bladder.

Citation Format: Binh Vo, Erika Abbott, Carolyn J. Vivian, Xena Moore, Ganeshkumar Rajendran, Katie Dennis, Benjamin L. Woolbright, Scott J. Weir, John A. Taylor. Ts65Dn Down syndrome mice reveal a potential therapeutic vulnerability in a BBN bladder cancer model and subset of bladder cancer cell lines [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3991.

Fosciclopirox clinical proof of concept in patients with nonmuscle invasive and muscle-invasive bladder cancer

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Background: Fosciclopirox (F) is being developed for the treatment of non-muscle invasive (NMIBC) and muscle invasive (MIBC) bladder cancer. F is a prodrug which is rapidly and completely metabolized in blood to its active metabolite, ciclopirox (CPX). In preclinical models of bladder cancer, CPX acts in part as a γ-secretase inhibitor by binding to γ-secretase complex proteins Presenilin 1 and Nicastrin, resulting in Notch and Wnt inhibition. The F Recommended Phase 2 Dose (RP2D), 900 mg/m2 administered IV over 20 minutes, was identified in the Phase 1 dose escalation trial (NCT03348514) in advanced solid tumor patients. Methods: The F RP2D was investigated in two early phase NMIBC and MIBC clinical proof of concept trials. In NCT04608045, neoadjuvant F was administered as monotherapy in cisplatin-ineligible (C-I) MIBC patients and in combination with gemcitabine + cisplatin in chemotherapy-eligible (C-E) MIBC patients. Clinical stage was assessed in pre-treatment (TURBT/CT) and post-treatment pathological state determined at radical cystectomy, (RC). The steady-state plasma and urine pharmacokinetics of F were also characterized. In NCT04525131, F was administered once daily for five days prior to TURBT. Pre- and post-treatment (at TURBT) bladder tumor samples underwent single cell sequencing to identify treatment effects on gene expression. Plasma, urine, and bladder tumor concentrations of F and its metabolites were determined in samples collected at TURBT. Results: Five C-E and 4 C-I MIBC patients received neoadjuvant F prior to RC. Twelve NMIBC patients received F prior to TURBT. There were no treatment-related serious adverse events observed in either study. Each patient experienced at least one treatment-emergent adverse event (TEAE), none of which resulted in study discontinuation. The most common TEAEs were nausea, fatigue, and constipation. Pathologic downstaging (< ypT2) of bladder tumors was observed in 3 C-E MIBC patients with 2 CRs (ypT0). Two of 4 C-I patients had evident clinical response by CT scan with only microscopic residual ypT2 disease. Treatment-related changes in expression of Notch 1, Notch 2, Hes 1, Hey-1, c-Myc, ß-catenin and survivin were observed in the majority of NMIBC patients. F disappeared from plasma within 2 hours of administration. The mean CPX elimination half-life of CPX, apparent systemic clearance, and volume of distribution values were 8.8 hours, 46 L/hr and 549 L, respectively. Mean plasma, tumor and urine concentrations of CPX at TURBT were approximately 27, 9 and 100 µM, respectively. Conclusions: To date, fosciclopirox is well tolerated and achieves sufficient systemic, tumor, and urine CPX exposure at the RP2D. Evidence of target inhibition was demonstrated in NMIBC tumors and preliminary signs of clinical activity observed in MIBC patients. Safety and efficacy trials are planned to confirm and expand findings in NMIBC and MIBC patients. Clinical trial information: NCT04608045; NCT04525131.

IV vitamin C with chemotherapy for cisplatin ineligible bladder cancer patients (CI-MIBC) first-stage analysis NCT04046094

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Background: Neo-adjuvant cisplatin-based chemotherapy (NAC) is considered standard of care for patients with locally advanced disease. However, ̃40% of patients are cisplatin ineligible (CI) due to renal insufficiency, hearing loss or poor performance status. Gemcitabine and carboplatin (GCa) has limited success in this setting. Patients usually proceed directly to cystectomy without realizing the potential survival benefit afforded by NAC. Intravenous ascorbate (vitamin C) administration (IVC) has been shown to improve the efficacy of carboplatin and gemcitabine-based therapy in other models. This single-arm, Simon 2-stage, window of opportunity trial included IVC with single cycle GCa to evaluate pathologic downstaging. We report on the interim first stage analysis of 12 patients. Methods: Patients with newly diagnosed CI-MIBC were enrolled and received single cycle GCa and IVC titrated to peak plasma concentration of 350 to 400 mg/dL (̃20 mM) for 21 days followed by cystectomy at 4-6 weeks from initiation of treatment. The primary outcome is pathological stage at cystectomy. Patients are then followed per NCCN guidelines with standard of care bloodwork, physical exam and imaging studies until progression and/or death. QOL is being evaluated by Functional Assessment of Cancer Therapy-Bladder (FACT-Bl). Results: All 12 patients completed GCa/IVC with 11 having had a cystectomy and 1 pending surgery. Pathological downstaging (yp < T2) was noted in 4 patients with 3 CRs (ypT0N0Mx) and 1 with residual ypTisN0Mx only. Of note, 1 CR was seen in a patient with locally advanced plasmacytoid variant. Participants tolerated treatment well with minimal treatment related AE/SAEs. Conclusions: Interim analysis of GCa-IVC NAC shows good tolerability with > 36% rate of downstaging. Of those with a pathological response, 75% achieved a CR. Continuation criteria has been met for stage 2. FACT-BI analysis and clinical follow up is ongoing and will be reported at study completion. Clinical trial information: NCT04046094.

Abstract 2911: Intersection of aging, the microbiome and inflammation in a mouse model of bladder cancer

Bladder cancer (BCa) is a disease strongly related to aging and remains a major source of morbidity and mortality in the elderly. Older patients are at greater risk of developing BCa and treatment outcomes remain poor. Interventions aimed at delaying recurrence and enhancing therapy would be highly beneficial given the aging US population and association with BCa. Aging is associated with baseline immune dysfunction, increasing risk for chronic diseases such as cancers. Compounding this issue, dysregulated inflammation in cancer results in a switch in the inflammatory milieu toward a pro-tumorigenic phenotype. Recent studies have indicated immune dysregulation in multiple cancers is also likely related to the changes in the underlying microbiome. The impact of age-related changes in the microbiome and inflammatory status, and how this relates to progression of tumorigenesis in the bladder have not yet been defined though. We hypothesized aging would enhance inflammation and carcinogenesis in a mouse model of carcinogen induced BCa. To determine how aging affects BCa, we exposed middle aged mice (14 months old at study start), and young mice (2 months old at study start) to the urothelial carcinogen N-Butyl-N-(4-hydroxybutyl) nitrosamine (BBN) 0.05% in drinking water for 6-20 weeks. Pathological analysis indicated older mice had higher indices of cellular inflammation at baseline and after BBN. Similarly, older mice had significantly more upregulation of pro-inflammatory mediators after 6 weeks exposure to BBN. While inflammatory metrics were increased, this did not extend to tumor size or stage. Middle aged mice (14 months) do not express prototypical biomarkers of aging yet though, and represent a very mild phenotype. To test the idea that truly older mice would be more susceptible to carcinogenesis, we treated young mice (8 weeks at start) or truly old mice (18 months at start) with 0.05% BBN for 16 weeks. We found older animals had larger tumors indicative of increased tumorigenesis after 16 weeks BBN. Moreover, multiple older mice muscle invasive tumors which were absent in the young group and increased recruitment of neutrophils indicative of increased inflammation. We subsequently analyzed the fecal microbiome using 16S sequencing of bacterial DNA. ß-diversity indices indicated substantial differences in microbiota constituency between young and older mice with cancer, although these differences were not observed at baseline. Future goals are to determine if aging-related alterations in the microbiome are responsible for the observed changes in tumor formation and inflammation. In conclusion, aged animals experience more inflammation, major changes in gut microbial content, and develop larger and more aggressive tumors after exposure to carcinogens implicating a pathological role for aging in BCa.

Citation Format: Benjamin L. Woolbright, Erika Abbott, Ganeshkumar Rajendran, Cuncong Zhong, Hao Xuan, Shahid Umar, John Arthur Taylor. Intersection of aging, the microbiome and inflammation in a mouse model of bladder cancer [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 2911.

Late Protective Effect of Netrin-1 in the Murine Acetaminophen Hepatotoxicity Model

Acetaminophen (APAP) overdose-induced acute liver failure is an important clinical problem in the United States and the current antidote N-acetylcysteine, has a short early therapeutic window. Since most patients present late to the clinic, there is need for novel late-acting therapeutic options. Though the neuronal guidance cue netrin-1, has been shown to promote hepatic repair and regeneration during liver ischemia/reperfusion injury, its effect in APAP-induced hepatotoxicity is unknown. In the quest for a late-acting therapeutic intervention in APAP-induced liver injury, we examined the role of netrin-1 in a mouse model of APAP overdose. Male C57BL/6J mice were cotreated with exogenous netrin-1 or vehicle control, along with 300 mg/kg APAP and euthanized at 6, 12, and 24 h. Significant elevations in alanine aminotransferase indicative of liver injury were seen in control mice at 6 h and this was not affected by netrin-1 administration. Also, netrin-1 treatment did not influence mitochondrial translocation of phospho-JNK, or peroxynitrite formation indicating that there was no interference with APAP-induced injury processes. Interestingly however, netrin-1 administration attenuated liver injury at 24 h, as seen by alanine aminotransferase levels and histology, at which time significant elevations in the netrin-1 receptor, adenosine A2B receptor (A2BAR) as well as macrophage infiltration was evident. Removal of resident macrophages with clodronate liposomes or treatment with the A2BAR antagonist PSB1115 blocked the protective effects of netrin-1. Thus, our data indicate a previously unrecognized role for netrin-1 in attenuation of APAP hepatotoxicity by enhancing recovery and regeneration, which is mediated through the A2BAR and involves resident liver macrophages.

Natural products as a means of overcoming cisplatin chemoresistance in bladder cancer

Cisplatin remains an integral part of the treatment for muscle invasive bladder cancer. A large number of patients do not respond to cisplatin-based chemotherapy and efficacious salvage regimens are limited. Immunotherapy has offered a second line of treatment; however, only approximately 20% of patients respond, and molecular subtyping of tumors indicates there may be significant overlap in those patients that respond to cisplatin and those patients that respond to immunotherapy. As such, restoring sensitivity to cisplatin remains a major hurdle to improving patient care. One potential source of compounds for enhancing cisplatin is naturally derived bioactive products such as phytochemicals, flavonoids and others. These compounds can activate a diverse array of different pathways, many of which can directly promote or inhibit cisplatin sensitivity. The purpose of this review is to understand current drug development in the area of natural products and to assess how these compounds may enhance cisplatin treatment in bladder cancer patients.

Abstract 5150: MIF-2 in bladder cancer: potential therapeutic target

Macrophage migration inhibitory factor (MIF1) is a pro-tumorigenic cytokine overexpressed in multiple cancers. Our previous data in a carcinogen (BBN) induced murine bladder cancer (BCa) model indicates genetic depletion of MIF1 induces stage arrest. Pharmacological inhibition of MIF1 with the inhibitor CPSI-1306 reduces tumor stage and bladder weights. These data indicate MIF1 is a therapeutic target in BCa. However, a second protein with significant homology to MIF1 was recently identified and termed MIF2. Both MIF1 and MIF2 bind and activate their receptor CD74 yielding significant functional homology and thus, targeting both proteins may be more efficacious. We hypothesize MIF2 recapitulates the pro-tumorigenic effects of MIF1 in BCa in a CD74 dependent manner. We assessed MIF1 and MIF2 by ELISA in serum from human patients with BCa and MIF1/2 expression were evaluated in TCGA. WT mice (C57Bl/6 background), MIF-/-, and CD74-/- mice were treated with 0.05% BBN for 16 weeks to induce BCa, and then switched to water. Tumors were allowed to develop until 20 weeks post initiation of BBN, a time frame consistent with muscle invasive tumor development. Some animals were given either vehicle, or a dual MIF1/MIF2 inhibitor 4-IPP (80mg/kg i.p. daily) for 4 weeks after cessation of BBN. We assessed bladder weights as a surrogate for tumor weight, tumor stage and immunohistochemistry for proliferation, angiogenesis and inflammation. In vitro cell proliferation was measured using the hexosaminidase assay and tautomerase activity was measured using two separate enzymatic assays for MIF tautomerase activity. MIF1 and MIF2 mRNA levels were elevated in TCGA. Analysis of serum from BCa patients indicated increased MIF1 and MIF2 in BCa patients, although this didn't reach statistical significance. 4-IPP treated C57Bl/6 animals had reductions in bladder weight, although tumor staging was similar between groups. 4-IPP treatment had no effect on bladder weights or tumor stage in CD74-/- mice supporting a role for CD74 mediated MIF signaling. To more fully assess the role of MIF2 directly, MIF1-/- mice were treated with 4-IPP to solely block MIF2

4-IPP treatment lead to major reductions in tumor stage, tumor incidence and bladder weight indicating inhibition of MIF2 may be more effective when MIF1 is chronically absent. Inflammation and proliferation trended lower, but did not reach statistical significance. MIF1 depletion did not affect MIF2 mRNA levels in bladder, heart or liver. In vitro treatment with 4-IPP substantially reduced proliferation of two high grade BCa cell lines (HTB-5, HTB-9) at concentrations consistent with doses found to inhibit recombinant MIF activity. These data indicate MIF1/2 enhance BCa tumorigenesis through activation of CD74. Combined MIF1/MIF2 may improve therapeutic targeting of MIF, especially during chronic MIF1 inhibition.

Citation Format: Ganeshkumar Rajendran, Benjamin L. Woolbright, Erika Abbott, Austin Martin, Katie Dennis, John Arthur Taylor. MIF-2 in bladder cancer: potential therapeutic target [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 5150.

Genomic heterogeneity in bladder cancer: challenges and possible solutions to improve outcomes

Histological and molecular analyses of urothelial carcinoma often reveal intratumoural and intertumoural heterogeneity at the genomic, transcriptional and cellular levels. Despite the clonal initiation of the tumour, progression and metastasis often arise from subclones that can develop naturally or during therapy, resulting in molecular alterations with a heterogeneous distribution. Variant histologies in tumour tissues that have developed distinct morphological characteristics divergent from urothelial carcinoma are extreme examples of tumour heterogeneity. Ultimately, heterogeneity contributes to drug resistance and relapse after therapy, resulting in poor survival outcomes. Mutation profile differences between patients with muscle-invasive and metastatic urothelial cancer (interpatient heterogeneity) probably contribute to variability in response to chemotherapy and immunotherapy as first-line treatments. Heterogeneity can occur on multiple levels and averaging or normalizing these alterations is crucial for clinical trial and drug design to enable appropriate therapeutic targeting. Identification of the extent of heterogeneity might shape the choice of monotherapy or additional combination treatments to target different drivers and genetic events. Identification of the lethal tumour cell clones is required to improve survival of patients with urothelial carcinoma.

Window of opportunity trial to characterize the safety, pharmacokinetics, and pharmacodynamics of fosciclopirox (CPX-POM) in cisplatin-ineligible muscle invasive bladder cancer patients

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Background: Fosciclopirox (Ciclopirox Prodrug, CPX-POM) is being developed for the treatment of non-muscle invasive and muscle invasive (MIBC) bladder cancer. CPX-POM selectively delivers its active metabolite, ciclopirox (CPX), to the entire urinary tract following systemic administration. In a validated, chemical carcinogen mouse model of bladder cancer, CPX-POM treatment results in significant decreases in bladder weight, a clear migration to lower stage tumors, dose-dependent reductions in Ki67 and PCNA staining, and inhibition of Notch 1 and Wnt signaling. The safety, dose tolerance, pharmacokinetics and pharmacodynamics of IV CPX-POM have recently been characterized in 19 patients with advanced solid tumors (CPX-POM-001, NCT03348514). The safety and dose tolerance of IV CPX-POM was characterized across a dose range of 30 to 1200 mg/m2. The CPX-POM Recommended Phase 2 Dose (PR2D) of 900 mg/m2 administered IV over 20 minutes on Days 1-5 every 21 days was selected. Methods: Twelve cisplatin ineligible MIBC patients (Stage >T2, NO-N1, M0), scheduled for radical cystectomy (RC) will be enrolled in this window of opportunity study. Patients will receive two 21-day treatment cycles followed by RC within 14 days of completion of the second cycle. Safety and tolerability assessments will be made based on observed adverse and serious adverse events, physical examination, vital signs, electrocardiogram, clinical laboratory tests, and concomitant medications. Assessment of complete and partial pathologic response will be determined at RC. Ki67, Notch and Wnt signaling, and CD8+ lymphocyte tumor infiltration will be determined by immunohistochemistry. An unbiased approach to characterizing CPX-POM mechanisms of action will also be employed using RNAseq and ChIPseq. Serial blood (plasma) and complete urine specimens will be collected on Days 5-6 of Cycle 1 for determination of drug and metabolite concentrations by LC-MS/MS. Plasma and urine steady-state pharmacokinetics of CPX-POM, CPX and ciclopirox glucuronide will be characterized. Urine ß-glucuronidase activity is also being determined by ELISA. Clinical trial information: NCT03348514.

Safety, dose tolerance, pharmacokinetics, and pharmacodynamics of fosciclopirox (CPX-POM) in patients with advanced solid tumors

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Background: Fosciclopirox (CPX-POM) is being developed for the treatment of non-muscle invasive and muscle invasive bladder cancer. CPX-POM selectively delivers its active metabolite, ciclopirox (CPX), to the entire urinary tract following systemic administration. In a chemical carcinogen mouse model of bladder cancer, CPX-POM treatment resulted in significant decreases in bladder weight, migration to lower stage tumors, inhibition of cell proliferation as well as Notch 1 and Wnt signaling pathways. Methods: Study CPX-POM-001 (NCT03348514) is US multi-site, Phase I, open-label, dose escalation study characterizing the safety, dose tolerance, pharmacokinetics (PK) and pharmacodynamics of IV CPX-POM in advanced solid tumor patients. The PK of CPX-POM, CPX and ciclopirox glucuronide (CPX-G), were characterized in plasma and urine. Circulating biomarkers of Wnt and Notch, IL-6, IL-8 and VEGF were determined. Results: Nineteen patients were enrolled in the study. The starting dose of 30 mg/m2 was administered once daily on Days 1-5 of each 21-day treatment cycle. Doses were escalated to 1200 mg/m2. The MTD was determined to be 900 mg/m2. Overall, the number of treatment-related AE's tended to increase in frequency with dose, nausea and vomiting being the most common. Grade 3 confusion was observed in the 1200 mg/m2 cohort. Four AE's of Grade 1 confusion at 600 and 900 mg/m2. There was no evidence of QTc prolongation or other ECG abnormality. One patient in the 240 mg/m2 dose cohort, with a diagnosis of indolent primary fallopian tube tumor, achieved a partial response per RECIST 1.1. Metabolism of CPX-POM was rapid and complete. The clearance of CPX was dose proportional and time-independent. At MTD, steady-state 24-hour urine CPX concentrations of 215 µM were achieved. Evidence of Notch and Wnt inhibition was observed. Conclusions: IV CPX-POM was well tolerated with treatment-related AEs primarily CNS-related. At MTD, systemic and urinary CPX exposures exceeding in vitro IC50 values by several-fold. The 900 mg/m2 dose is currently being evaluated in an expansion cohort study in cisplatin-ineligible muscle invasive bladder cancer patients scheduled for cystectomy. Clinical trial information: NCT03348514.

Prostaglandin E2 as a therapeutic target in bladder cancer: From basic science to clinical trials

Bladder cancer (BCa) is a common solid tumor marked by high rates of recurrence, especially in non-muscle invasive disease. Prostaglandin E₂ (PGE₂) is a ubiquitously present lipid mediator responsible for numerous physiological actions. Inhibition of cyclooxygenase (COX) enzymes by the non-steroidal anti-inflammatory (NSAID) class of drugs results in reduced PGE₂ levels. NSAID usage has been associated with reductions in cancers such as BCa. Clinical trials using NSAIDs to prevent recurrence have had mixed results, but largely converge on issues with cardiotoxicity. The purpose of this review is to understand the basic science behind how and why inhibitors of PGE₂ may be effective against BCa, and to explore alternate therapeutic modalities for addressing the role of PGE₂ without the associated cardiotoxicity. We will address the role of PGE₂ in a diverse array of cancer-related functions including stemness, immunosuppression, proliferation, cellular signaling and more.

Mice deficient in pyruvate dehydrogenase kinase 4 are protected against acetaminophen-induced hepatotoxicity

Though mitochondrial oxidant stress plays a critical role in the progression of acetaminophen (APAP) overdose-induced liver damage, the influence of mitochondrial bioenergetics on this is not well characterized. This is important, since lifestyle and diet alter hepatic mitochondrial bioenergetics and an understanding of its effects on APAP-induced liver injury is clinically relevant. Pyruvate dehydrogenase (PDH) is critical to mitochondrial bioenergetics, since it controls the rate of generation of reducing equivalents driving respiration, and pyruvate dehydrogenase kinase 4 (PDK4) regulates (inhibits) PDH by phosphorylation. We examined APAP-induced liver injury in PDK4-deficient (PDK4^-/-) mice, which would have constitutively active PDH and hence elevated flux through the mitochondrial electron transport chain. PDK4^-/- mice showed significant protection against APAP-induced liver injury when compared to wild type (WT) mice as measured by ALT levels and histology. Deficiency of PDK4 did not alter APAP metabolism, with similar APAP-adduct levels in PDK4^-/- and WT mice, and no difference in JNK activation and translocation to mitochondria. However, subsequent amplification of mitochondrial dysfunction with release of mitochondrial AIF, peroxynitrite formation and DNA fragmentation were prevented. Interestingly, APAP induced a rapid decline in UCP2 protein levels in PDK4-deficient mice. These data suggest that adaptive changes in mitochondrial bioenergetics induced by enhanced respiratory chain flux in PDK4^-/- mice render them highly efficient in handling APAP-induced oxidant stress, probably through modulation of UCP2 levels. Further investigation of these specific adaptive mechanisms would provide better insight into the control exerted by mitochondrial bioenergetics on cellular responses to an APAP overdose.

Inflammation and Cell Death During Cholestasis: The Evolving Role of Bile Acids

Cholestasis results in blockage of bile flow whether the point of obstruction occurs extrahepatically or intrahepatically. Bile acids are a primary constituent of bile, and thus one of the primary outcomes is acute retention of bile acids in hepatocytes. Bile acids are normally secreted into the biliary tracts and then released into the small bowel before recirculating back to the liver. Retention of bile acids has long been hypothesized to be a primary cause of the associated liver injury that occurs during acute or chronic cholestasis. Despite this, a surge of papers in the last decade have reported a primary role for inflammation in the pathophysiology of cholestatic liver injury. Furthermore, it has increasingly been recognized that both the constituency of individual bile acids that make up the greater pool, as well as their conjugation status, is intimately involved in their toxicity, and this varies between species. Finally, the role of bile acids in drug-induced cholestatic liver injury remains an area of increasing interest. The purpose of this review is to critically evaluate current proposed mechanisms of cholestatic liver injury, with a focus on the evolving role of bile acids in cell death and inflammation.

Metabolic Flexibility in Cancer: Targeting the Pyruvate Dehydrogenase Kinase:Pyruvate Dehydrogenase Axis

Cancer cells use alterations of normal metabolic processes to sustain proliferation indefinitely. Transcriptional and posttranscriptional control of the pyruvate dehydrogenase kinase (PDK) family is one way in which cancer cells alter normal pyruvate metabolism to fuel proliferation. PDKs can phosphorylate and inactivate the pyruvate dehydrogenase complex (PDHC), which blocks oxidative metabolism of pyruvate by the mitochondria. This process is thought to enhance cancer cell growth by promoting anabolic pathways. Inhibition of PDKs induces cell death through increased PDH activity and subsequent increases in ROS production. The use of PDK inhibitors has seen widespread success as a potential therapeutic in laboratory models of multiple cancers; however, gaps still exist in our understanding of the biology of PDK regulation and function, especially in the context of individual PDKs. Efforts are currently underway to generate PDK-specific inhibitors and delineate the roles of individual PDK isozymes in specific cancers. The goal of this review is to understand the regulation of the PDK isozyme family, their role in cancer proliferation, and how to target this pathway therapeutically to specifically and effectively reduce cancer growth.

Direct Amplification of Tissue Factor:Factor VIIa Procoagulant Activity by Bile Acids Drives Intrahepatic Coagulation

OBJECTIVE

Regulation of TF (tissue factor):FVIIa (coagulation factor VIIa) complex procoagulant activity is especially critical in tissues where plasma can contact TF-expressing cells. One example is the liver, where hepatocytes are routinely exposed to plasma because of the fenestrated sinusoidal endothelium. Although liver-associated TF contributes to coagulation, the mechanisms controlling the TF:FVIIa complex activity in this tissue are not known. Approach and Results: Common bile duct ligation in mice triggered rapid hepatocyte TF-dependent intrahepatic coagulation coincident with increased plasma bile acids, which occurred at a time before observable liver damage. Similarly, plasma TAT (thrombin-antithrombin) levels increased in cholestatic patients without concurrent hepatocellular injury. Pathologically relevant concentrations of the bile acid glycochenodeoxycholic acid rapidly increased hepatocyte TF-dependent procoagulant activity in vitro, independent of de novo TF synthesis and necrotic or apoptotic cell death. Glycochenodeoxycholic acid increased hepatocyte TF activity even in the presence of the phosphatidylserine-blocking protein lactadherin. Interestingly, glycochenodeoxycholic acid and taurochenodeoxycholic acid increased the procoagulant activity of the TF:FVIIa complex relipidated in unilamellar phosphatidylcholine vesicles, which was linked to an apparent decrease in the K_m for FX (coagulation factor X). Notably, the zwitterionic detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate, a bile acid structural analog, did not increase relipidated TF:FVIIa activity. Bile acids directly enhanced factor X activation by recombinant soluble TF:FVIIa complex but had no effect on FVIIa alone.

CONCLUSIONS

The results indicate that bile acids directly accelerate TF:FVIIa-driven coagulation reactions, suggesting a novel mechanism whereby elevation in a physiological mediator can directly increase TF:FVIIa procoagulant activity.

Tumor M2-PK: A novel urine marker of bladder cancer

PURPOSE

Bladder cancer is a "Warburg-like" tumor characterized by a reliance on aerobic glycolysis and expression of pyruvate kinase M2 (PKM2). PKM2 oscillates between an active tetramer and an inactive dimer. We aim to further characterize PKM2, in particular PKM2 dimer, as a urinary biomarker of bladder cancer and a potential target for treatment.

METHODS

HTB-9, HTB-5, and UM-UC3 bladder cancer cells were assessed for proliferation under differential glucose levels using the hexosaminidase assay. Western blot and Blue-native analysis was performed for protein expression of PKM2. Shikonin, an herb that is known to bind and inhibit PKM2, was utilized to determine if PKM2 has a role in glucose usage and cellular proliferation in bladder cancer cells by caspase activity assay. Institutional review board approval was obtained to collect healthy control and bladder cancer patient urine samples. The ScheBo M2-PK EDTA Plasma Test was performed on urine samples to assess urine Tumor M2-PK values.

RESULTS

The three bladder cancer cell lines tested all demonstrate statistically significant increases in proliferation when exposed to higher level of glucose (200mg/dL). Similarly, low doses of glucose (25mg/dL) result in reduced proliferation. Increased cell growth in higher glucose concentration correlated with up-regulation of PKM2 protein expression. Shikonin, a PKM2 inhibitor, reduced cell proliferation and switched PKM2 isoforms from the dimer to tetramer. Lastly, dimer PKM2 (Tumor-M2PK) levels were assessed in the urine samples from bladder cancer (Bca) patients and healthy controls. Tumor M2-PK significantly correlated with the presence of BCa in our subjects.

CONCLUSIONS

Our studies demonstrate the potential of PKM2, specifically the dimer (Tumor-M2PK) as a target of drug therapy and as a urinary marker for bladder cancer.

Leukocyte cell derived chemotaxin-2 (Lect2) as a predictor of survival in adult acute liver failure

Background

One of the major issues in the field of acute liver failure (ALF) is the lack of reliable biomarkers that predict outcome. Many cases present with very limited treatment options and prognostic indicators are invaluable. We tested whether leukocyte cell derived chemotaxin 2 can be used as a prognostic biomarker to predict patient survival either alone or in combination with other routine clinical parameters.

Methods

Serum samples and associated clinical data from came from two independent sources, the Acute Liver Failure Study Group (ALFSG) registry and the University of Kansas Medical Center. We analyzed a total of 61 cases, each with individual time points collected over a period of 0 to 7 days after hospital admission. Analysis was developed to compare responses in survivors vs. non-survivors.

Results

The data indicate that survivors had significantly lower serum levels of leukocyte cell derived chemotaxin 2 compared to non-survivors (P=0.03). Further, it was able to predict patient survival when taken together with either international normalized ratio (INR) alone (71% concordance) or INR and bilirubin (76% concordance) or INR and serum albumin (77% concordance). Furthermore, when we analyzed data for each day, serum Lect2 and INR taken together were able to predict survival at day three after hospital admission with 86.3% concordance.

Conclusions

These studies have revealed test batteries consisting of easily available serum tests that are concordant with survival status of ALF patients early during the clinical course.

The role of phosphoglycerate mutase 2 in UM-UC3 bladder cancer cell metabolism

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Background: Bladder cancer remains the fourth most common cancer in American males with a higher risk of recurrence and progression for patients with diabetes mellitus. Urothelial bladder cancer is characterized by aerobic glycolysis with upregulation of glycolytic enzymes (known as the Warburg effect) such as phosphoglycerate mutase. Phosphoglycerate mutase 2 (PGAM2), a reversible glycolytic enzyme expressed highly in muscle, represents a target for modulation because of its differential expression from another isoform, phosphoglycerate mutase 1. PGAM2 knockdown may impact bladder cancer growth significantly via its effect on glucose metabolism at different glucose concentrations seen in patients with diabetes mellitus. Methods: UM-UC3 bladder cancer cells were assessed for PGAM2 expression at different glucose concentrations via Western blot and quantitative PCR. One native UM-UC3 line, three PGAM2 knockdown lines, and one vector control cell line were included in the western blot study. Cellular proliferation was analyzed using an enzyme based hexoseaminidase assay and was further supported with an automated cell counter. The effects of cisplatin were also investigated. Results: Increased PGAM2 expression at increased glucose concentrations in UM-UC3 was confirmed by Western blot and quantitative PCR. PGAM2 knockdown cells responded differently to changes in glucose concentration compared to the control cell lines, with a large increase in growth at a low glucose level of 25mg/dL after day 4. Cell proliferation demonstrated similar growth between the knockdown and controls at higher glucose concentrations of 100 and 200mg/dL. Proliferation data using automated cell counter demonstrate the same growth trend. Conclusions: Increased cell growth of PGAM2 knockdowns, most notably at 25mg/dL, suggests that PGAM2 may play a different role in glycolysis than expected, possibly serving as a modulator in cell growth instead of a simple reversible enzyme. We are currently investigating its differential expression compared to PGAM1, an enzyme recently characterized to have an opposite effect to PGAM2.

Sortilin 1 Loss-of-Function Protects Against Cholestatic Liver Injury by Attenuating Hepatic Bile Acid Accumulation in Bile Duct Ligated Mice

Sortilin 1 (Sort1) is an intracellular trafficking receptor that mediates protein sorting in the endocytic or secretory pathways. Recent studies revealed a role of Sort1 in the regulation of cholesterol and bile acid (BA) metabolism. This study further investigated the role of Sort1 in modulating BA detoxification and cholestatic liver injury in bile duct ligated mice. We found that Sort1 knockout (KO) mice had attenuated liver injury 24 h after bile duct ligation (BDL), which was mainly attributed to less bile infarct formation. Sham-operated Sort1 KO mice had about 20% larger BA pool size than sham-operated wildtype (WT) mice, but 24 h after BDL Sort1 KO mice had significantly attenuated hepatic BA accumulation and smaller BA pool size. After 14 days BDL, Sort1 KO mice showed significantly lower hepatic BA concentration and reduced expression of inflammatory and fibrotic marker genes, but similar degree of liver fibrosis compared with WT mice. Unbiased quantitative proteomics revealed that Sort1 KO mice had increased hepatic BA sulfotransferase 2A1, but unaltered phase-I BA metabolizing cytochrome P450s or phase-III BA efflux transporters. Consistently, Sort1 KO mice showed elevated plasma sulfated taurocholate after BDL. Finally, we found that liver Sort1 was repressed after BDL, which may be due to BA activation of farnesoid x receptor. In conclusion, we report a role of Sort1 in the regulation of hepatic BA detoxification and cholestatic liver injury in mice. The mechanisms underlying increased hepatic BA elimination in Sort1 KO mice after BDL require further investigation.

Measuring Apoptosis and Necrosis in Cholestatic Liver Injury

Cholestasis can be induced by obstruction of bile ducts or intrahepatic toxicity of drugs and chemicals. However, the mode of cell death during cholestasis, i.e., apoptosis or necrosis, has been controversial. There are fundamental reasons for the controversies, both of which are discussed here, namely the design of experiments and the use of parameters with limited specificity for a certain mode of cell death. Based on the assumption that cholestatic liver injury is caused by accumulation of bile acids, rodent (mainly rat) hepatocytes have been exposed to hydrophobic, glycine-conjugated bile acids, which resulted in apoptotic cell death. The problems with this experimental design are that in rodents bile acids are predominantly taurine conjugated and rodent hepatocytes are never exposed to these levels of glycine-conjugated bile acids. In contrast, taurine-conjugated bile acids trigger inflammatory gene activation in rodent hepatocytes and a necro-inflammatory injury in vivo. On the other hand, human hepatocytes are more resistant to glycine-conjugated bile acids and die by necrosis when exposed to high biliary levels of these bile acids. In this chapter, we describe multiple assays including the caspase activity assay, which is specific for apoptosis, and the general cell death assays alanine aminotransferase or lactate dehydrogenase activities in cell culture medium or plasma. An increase in these enzyme activities without caspase activity indicates necrotic cell death. Thus, both the experimental design and the selection of cell death parameters are critical for the relevance of the experiments for the human pathophysiology.

Mito-tempo protects against acute liver injury but induces limited secondary apoptosis during the late phase of acetaminophen hepatotoxicity

We previously reported that delayed treatment with Mito-tempo (MT), a mitochondria-targeted superoxide dismutase mimetic, protects against the early phase of acetaminophen (APAP) hepatotoxicity by inhibiting peroxynitrite formation. However, whether this protection is sustained to the late phase of toxicity is unknown. To investigate the late protection, C57Bl/6J mice were treated with 300 mg/kg APAP followed by 20 mg/kg MT 1.5 h or 3 h later. We found that both MT treatments protected against the late phase of APAP hepatotoxicity at 12 and 24 h. Surprisingly, MT-treated mice demonstrated a significant increase in apoptotic hepatocytes, while the necrotic phenotype was observed almost exclusively in mice treated with APAP alone. In addition, there was a significant increase in caspase-3 activity and cleavage in the livers of MT-treated mice. Immunostaining for active caspase-3 revealed that the positively stained hepatocytes were exclusively in centrilobular areas. Treatment with the pan-caspase inhibitor ZVD-fmk (10 mg/kg) 2 h post-APAP neutralized this caspase activation and provided additional protection against APAP hepatotoxicity. Treatment with N-acetylcysteine, the current standard of care for APAP poisoning, protected but did not induce this apoptotic phenotype. Mechanistically, MT treatment inhibited APAP-induced RIP3 kinase expression, and RIP3-deficient mice showed caspase activation and apoptotic morphology in hepatocytes analogous to MT treatment. These data suggest that while necrosis is the primary cause of cell death after APAP hepatotoxicity, treatment with the antioxidant MT may switch the mode of cell death to secondary apoptosis in some cells. Modulation of mitochondrial oxidative stress and RIP3 kinase expression play critical roles in this switch.

Mechanisms of Inflammatory Liver Injury and Drug-Induced Hepatotoxicity

PURPOSE OF REVIEW

This article provides a brief overview of mechanisms of inflammatory liver injury and how this applies to drug hepatotoxicity with a particular emphasis on the role of inflammation in acetaminophen-induced liver injury.

RECENT FINDINGS

Significant progress has been made in the last decade in our understanding of the initiation of sterile inflammation after necrotic cell death by the release of damage-associated molecular patterns and their recognition by toll-like receptors and others on macrophages. These events trigger the formation of cytokines and chemokines directly or with assistance of inflammasome activation thereby activating and recruiting leukocytes including neutrophils and monocyte-derived macrophages into the necrotic areas. Although this sterile inflammatory response is mainly geared towards the removal of necrotic cell debris and preparation of regeneration, there are conditions where these innate immune cells can aggravate the initial injury. The mechanisms and controversial findings of the innate immunity are being discussed in detail. In contrast, drug metabolism and formation of a reactive metabolite that binds to proteins in the absence of extensive cell death, can induce an adaptive immune response, which eventually also results in severe liver injury. However, the initiating event appears to be the formation of protein adducts, which act as haptens to activate an adaptive immune response. Overall, these mechanisms are less well understood.

SUMMARY

The past decade has revolutionized our understanding of the mechanisms that control the interplay between cell death and innate or adaptive immune responses. This report provides an update on these mechanisms.

Abstract 4972: PDK inhibition sensitizes bladder tumors to cisplatin

Pyruvate Dehydrogenase Kinase-4 (PDK4) is a member of the PDK enzyme family. PDKs phosphorylate and inactivate the pyruvate dehydrogenase (PDH) complex, shunting pyruvate into the cytoplasm for oxidative metabolism, a phenomenon known as aerobic glycolysis or the Warburg Effect. This confers both growth advantages and resistance to chemotherapy. We previously noted that high grade human bladder tumors have substantial upregulation of PDK4, in the absence of other PDKs. We hypothesized PDK4 would be upregulated in bladder tumors, and inhibition of PDK4 would reduce bladder tumor growth and sensitize cells to cisplatin. We explored tested this hypothesis in cell culture and xenograft and carcinogen induced mouse models. Substantial overexpression of PDK4 (20-120 fold) was confirmed by qPCR in multiple bladder cancer cell lines as compared to UROtsa cells, a benign urothelial cell line. Treatment with dichloroacetate (DCA), a pan-specific PDK inhibitor, significantly increased PDH activity and reduced cellular proliferation in HTB-9 and HTB-5 cancer cells. In line with previous studies in other tumors, DCA also sensitized HTB-9 and HTB-5 cells to cisplatin induced cell death. Notably, this was not through enhanced apoptosis, as caspase activity did not increase, but rather co-treatment resulted in significant increases in LDH release, a marker of necrosis, and increased PI/Annexin V positive cells in DCA plus cisplatin treated cells compared to DCA or cisplatin alone. Inhibition of apoptosis with z-VAD-fmk confirmed the increased necrosis, as DCA plus cisplatin treated cells still had significant increases in cell death compared to DCA or cisplatin alone. Treatment of HTB-9 tumor xenografts with DCA or cisplatin did not reduce tumor volumes; however, co-treatment with both compounds resulted in significant reductions in viable tumor weights, along with increased TUNEL staining. As DCA is a pan-specific PDK inhibitor (PDK1-4), we also used the recently generated PS10 compound with equal specificity for PDK2 and PDK4. PS10 also significantly increased PDH activity, sensitized UM-UC3 cells to cisplatin and reduced cellular proliferation at concentrations at, and above 20µM. To further validate PDK inhibition as a therapeutic target, C57Bl/6J WT mice were treated with 0.05% BBN in the drinking water for 14 weeks to initiate tumorigenesis, and then treated with 70mg/kg PS10 daily +/- weekly[B1] ip cisplatin for 3 weeks. PS10 alone had no effect. While cisplatin reduced bladder weights, only PS10 plus cisplatin resulted in significant reduction in bladder tumor weight. Inhibition of PDKs sensitizes bladder cancers to cisplatin both in vitro and in vivo, as well as having direct anti-proliferative effects in vitro. PDK inhibition may be a useful and novel way to enhance cisplatin based therapies in bladder cancer.

Citation Format: Sambantham Shanmugam, Erika Abbott, Justin Penticuff, Dharamainder Choudhary, Benjamin L. Woolbright, John A. Taylor. PDK inhibition sensitizes bladder tumors to cisplatin [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 4972.

Abstract 3560: Targeting the MIF receptor CD74 in bladder cancer tumorigenesis

Macrophage migration inhibitory factor (MIF) is a pleiotropic cytokine that can stimulate cellular proliferation in multiple tumors. Our previous data indicates genetic deletion of MIF results in T1 stage arrest in the N-Butyl-N-(4-hydroxybutyl) nitrosamine (BBN) induced bladder cancer model. Similarly, pharmacological inhibition of MIF results in lower stage tumors and reduced bladder weights when given therapeutically. CD74 is a human leukocyte antigen class II trafficking and processing protein that also functions as an extracellular receptor for MIF. Additionally, CD74 complexes with CD44 to act as the cognate MIF receptor complex, and upregulation of CD74 has been noted in high grade bladder cancer. We hypothesized CD74 would be upregulated in malignant bladder cancer cell lines, and knockout of CD74 would reduce bladder cancer tumorigenesis in the murine BBN model. The objectives of this study were to determine the effect of CD74 knockout on development and progression of urothelial cell carcinoma; as well as evaluate expression of the putative MIF signaling axis in BCa cell lines. BCa cell lines HTB-9, HTB-5, RT-4, T24 and HT-1376 and benign urothelial UROtsa cells were analyzed for MIF, CD74, and CD44 expression via quantitative PCR or western blot to assess expression of the MIF signaling axis. CD74 and CD44 expression by q-PCR were dramatically elevated in BCa cell lines vs. benign cell lines. Protein levels of CD74 and CD44 were elevated in multiple cell lines as well. MIF expression levels did not change between cell lines. To ascertain differences in BCa tumorigeneis, WT C57Bl/6J mice or CD74-/- mice were given 0.05% BBN in the drinking water for 22 weeks. Bladders were weighed and evaluated for pathologic staging by histology. After exposure to BBN, bladders from CD74-/- mice had a 33% reduction in weight vs. WT bladders (p=.062). Pathological analysis revealed lower stage tumors in bladders of CD74-/- mice (33% incidence; 6.7% pTa, 0% pTis, 6.7% pT1, 20% pT2, 6.7% pT3) as compared to bladders of WT mice (81.3% incidence; 0% pTa, 6.3% pTis, 25% pT1, 12.5% pT2, 37.5% pT3), which was a statistically significant reduction in tumor stage. Lower tumor stage correlated significantly with the CD74-/- genotype (p=0.02, Fisher's Exact Test). These data suggest CD74 likely mediates a portion of the effects of MIF in BCa, raising the possibility of both CD74 dependent, and independent MIF signaling pathways.

Citation Format: Justin Penticuff, Sambantham Shanmugam, Joshua Warrick, Brian Chase, Erika Abbott, Benjamin L. Woolbright, John A. Taylor. Targeting the MIF receptor CD74 in bladder cancer tumorigenesis [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 3560.

The Role of Pyruvate Dehydrogenase Kinase-4 (PDK4) in Bladder Cancer and Chemoresistance

Advanced bladder cancer remains a major source of mortality, with poor treatment options. Cisplatin-based chemotherapy is the standard treatment, however many patients are or become resistant. One potential cause of chemoresistance is the Warburg effect, a metabolic switch to aerobic glycolysis that occurs in many cancers. Upregulation of the pyruvate dehydrogenase kinase family (PDK1-PDK4) is associated with aerobic glycolysis and chemoresistance through inhibition of the pyruvate dehydrogenase complex (PDH). We have previously observed upregulation of PDK4 in high-grade compared with low-grade bladder cancers. We initiated this study to determine if inhibition of PDK4 could reduce tumor growth rates or sensitize bladder cancer cells to cisplatin. Upregulation of PDK4 in malignant bladder cancer cell lines as compared with benign transformed urothelial cells was confirmed using qPCR. Inhibition of PDK4 with dichloroacetate (DCA) resulted in increased PDH activity, reduced cell growth, and G₀-G₁ phase arrest in bladder cancer cells. Similarly, siRNA knockdown of PDK4 inhibited bladder cancer cell proliferation. Cotreatment of bladder cancer cells with cisplatin and DCA did not increase caspase-3 activity but did enhance overall cell death in vitro Although daily treatment with 200 mg/kg DCA alone did not reduce tumor volumes in a xenograft model, combination treatment with cisplatin resulted in dramatically reduced tumor volumes as compared with either DCA or cisplatin alone. This was attributed to substantial intratumoral necrosis. These findings indicate inhibition of PDK4 may potentiate cisplatin-induced cell death and warrant further studies investigating the mechanism through which this occurs. Mol Cancer Ther; 17(9); 2004-12. ©2018 AACR.

Alcoholic Hepatitis: Lost in Translation

Alcoholic hepatitis is the most severe and acute form of alcoholic liver disease. The mortality rate associated with alcoholic hepatitis is high, largely due to the lack of suitable pharmacological interventions. While there has been substantial research in the area, generating pharmacological interventions has been plagued by the lack of a robust mouse model both for testing and for understanding the underlying pathology. A number of major notable advances have been made in this area recently, with the goal of generating a mouse model of alcoholic hepatitis. The purpose of this article is to review recent advances in modeling alcoholic liver disease both in vitro and in vivo in the mouse, and place them in the context of the greater spectrum of alcoholic liver disease, with a focus on how we can translate current advances into a high-fidelity model of alcoholic hepatitis. In addition, we will review the basic mechanisms of alcoholic hepatitis as it is currently understood, focusing on recent advancements in diagnosis, prognosis and current pathophysiology, especially as it relates to the profound immune dysfunction present during alcoholic hepatitis.

Cell Death and Prognosis of Mortality in Alcoholic Hepatitis Patients Using Plasma Keratin-18

Alcoholic liver disease encompasses the progressive stages of liver dysfunction that culminates in alcoholic cirrhosis (AC) and in severe cases alcoholic hepatitis (AH). Currently, prognostic scores have limited specificity and sensitivity. Plasma keratin-18 (K18) levels are elevated during liver disease and may be biomarkers of outcome. The objective of this study was to determine if total K18 (M65) or caspase-cleaved K18 (M30) levels were different between AC and AH patients. M65 and M30 levels were measured in the plasma of consented healthy controls and patients with AC and AH. Cell death was assessed by TUNEL staining and caspase activity. M65 and M30 values were significantly higher in AC patients compared to healthy controls and further increased in AH patients. The M65 values and the M30/M65 ratios of nonsurviving AH patients were significantly elevated above their surviving counterparts and healthy controls. Statistical analysis indicated that M30/M65 ratios outperformed current indices for accurately distinguishing the prognosis of AH patients. These scores occurred with minimal increase in plasma cell death markers such as ALT and AST. Serum caspase activity, TUNEL staining, and M30 immunohistochemistry in biopsies indicated that serum and tissue values may not correlate well with overall cell death. In conclusion, both M65 and M30 differentiate AH from AC patients, and M65 values and the M30/M65 ratio are capable of predicting early stage mortality; however, they may not accurately reflect pure hepatocyte cell death in these populations, as they do not strongly correlate with traditional cell death markers.

SATB1 and bladder cancer: Is there a functional link?

PURPOSE

SATB1, a global genome organizer, has been shown to play a role in the development and progression of some solid tumors, but its role in bladder cancer is undetermined. Moreover, there is conflicting data about the role of SATB1 in other tumors. This study was initiated to assess a potential role for SATB1 with the hypothesis that SATB1 acts as a tumor promoter in bladder cancer.

MATERIALS AND METHODS

We evaluated SATB1 expression in bladder cancer cell lines (HTB-5, HTB-9) and compared them to a benign urothelial cell line (UROtsa). Short-hairpin RNA was used to silence SATB1 in multiple cell lines, and cell death and cell proliferation were assessed using multiple assays.

RESULTS

SATB1 expression was increased significantly in all cancer cell lines compared to benign urothelial cells. SATB1 expression was knocked down by short-hairpin RNA and functional outcomes, including cell number, cell-cycle arrest, cell viability, and apoptosis after cisplatin treatment, were measured. Surprisingly, knockdown of SATB1 in 2 high-grade cancer cell lines showed opposing functional roles. Compared to the non-silencing control, HTB-5 cells, showed decreased cellular proliferation and increased sensitivity to cisplatin, whereas HTB-9 cells, showed increased cell numbers and increased resistance to cisplatin.

CONCLUSION

We conclude that our results in bladder cancer are consistent with the conflicting data reported in other cancers, and that SATB1 might have different roles in cancer dependent on genetic background and stage of the cancer.

Induction of mitochondrial biogenesis protects against acetaminophen hepatotoxicity

Mitochondrial biogenesis (MB) is an adaptive response to maintain metabolic homeostasis after mitochondrial dysfunction. Induction of MB during APAP hepatotoxicity has not been studied. To investigate this, mice were treated with toxic doses of APAP and euthanized between 0 and 96 h. At early time points, APAP caused both mitochondrial dysfunction and reduction of mitochondrial mass, indicated by reduced activity of electron transport chain (ETC) complexes I and IV and depletion of mitochondrial DNA (mtDNA), respectively. Both ETC activity and mtDNA gradually recovered after 12 h, suggesting that MB occurs at late time points after APAP overdose. Immunofluorescent staining of mitochondria with mitochondrial outer membrane protein Tom20 further demonstrated that MB occurs selectively in hepatocytes surrounding necrotic areas. MB signaling mediators including PPARγ co-activator 1-α (Pgc-1α), nuclear respiratory factor-1 (Nrf-1) and mitochondrial fission protein dynamin-related protein-1 (Drp-1) were induced. Pgc-1α was selectively increased in hepatocytes surrounding necrotic areas. In addition, the time course of MB induction coincides with increased liver regeneration. Post-treatment with the known MB inducer SRT1720 increased Pgc-1α expression and liver regeneration, resulting in protection against late liver injury after APAP overdose. Thus, induction of MB is an important feature during APAP hepatotoxicity and liver regeneration.

Disruption of Estrogen Receptor Alpha in Rats Results in Faster Initiation of Compensatory Regeneration Despite Higher Liver Injury After Carbon Tetrachloride Treatment

Estrogen receptor alpha (ESR1) is 1 of the 2 intracellular receptors for estrogen and is expressed by hepatocytes in the liver. The role of ESR1 in the regulation of toxicant-induced liver injury and compensatory regeneration is not completely clear. We investigated the role of ESR1 in liver regeneration after carbon tetrachloride (CCl₄)-induced liver injury using wild type (WT) and ESR1 knockout (ESR1-KO) rats. Adult female WT and ESR1-KO rats were treated with 1 mL/kg CCl₄ and euthanized over a time course of 0 to 48 hours. Liver injury measured by serum alanine amino transaminase, and histopathological analysis showed significantly higher liver injury in ESR1-KO as compared to WT rats. Hematoxylin and eosin staining revealed 2-fold higher necrosis and significant inflammatory cell infiltration in ESR1-KO rats. Chloracetate esterase staining revealed higher neutrophil infiltration in ESR1-KO rat livers. Interestingly, proliferating cell nuclear antigen immunohistochemistry showed that in spite of 2-fold higher liver injury, the ESR1-KO rats had equal liver regeneration as compared to WT rats. Western blot analysis of cyclin D1 and phosphorylated Rb, proteins involved in the initiation of the cell cycle, was significantly higher at all time points in ESR1-KO rats. Further analysis revealed faster activation of canonical Wnt/β-catenin and NF-κB signaling in ESR1-KO rats characterized by higher activated β-catenin and phosphorylated p65 at 12 hours after CCl₄ treatment. Taken together, these data indicate that ESR1-mediated signaling inhibits liver regeneration by downregulation of Wnt signaling resulting in lower cyclin D1 activation after chemical-induced liver injury.

Role of the inflammasome in acetaminophen-induced liver injury and acute liver failure

Drug-induced acute liver failure carries a high morbidity and mortality rate. Acetaminophen overdose is the number one cause of acute liver failure and remains a major problem in Western medicine. Administration of N-acetyl cysteine is an effective antidote when given before the initial rise in toxicity; however, many patients present to the hospital after this stage occurs. As such, treatments which can alleviate late-stage acetaminophen-induced acute liver failure are imperative. While the initial mechanisms of toxicity are well described, a debate has recently occurred in the literature over whether there is a second phase of injury, mediated by inflammatory processes. Critical to this potential inflammatory process is the activation of caspase-1 and interleukin-1β by a molecular complex known as the inflammasome. Several different stimuli for the formation of multiple different inflammasome complexes have been identified. Formation of the NACHT, leucine-rich repeat (LRR) and pyrin (PYD) domains-containing protein 3 (Nalp3) inflammasome in particular, has directly been attributed to late-stage acetaminophen toxicity. In this review, we will discuss the mechanisms of acetaminophen-induced liver injury in mice and man with a particular focus on the role of inflammation and the inflammasome.

Plasma biomarkers to study mechanisms of liver injury in patients with hypoxic hepatitis

BACKGROUND & AIMS

Hypoxic hepatitis is a clinical condition precipitated by prolonged periods of oxygen deprivation to the liver. It can have several underlying causes. Despite its prevalence in critically ill patients, which can reach upwards of 10%, very little is known about the mechanisms of injury. Thus, we set out to measure previously identified circulating biomarkers in an attempt to describe mechanisms of injury following hypoxic hepatitis.

METHODS

Plasma from patients diagnosed with hypoxic hepatitis was collected for this study. Biomarkers of hepatocellular injury, mitochondrial damage and cell death were measured. These results were compared against results obtained from well-characterized acetaminophen overdose patients.

RESULTS

At peak injury, ALT measured 4082±606 U/L and gradually decreased over 5 days, corresponding to the clinically observed pattern of hypoxic hepatitis. Levels of GDH showed a similar pattern, but neither ALT nor GDH were significantly higher in these patients than in acetaminophen patients. Plasma levels of DNA fragments mimicked hepatocellular injury as measured by ALT and miRNA-122. Interestingly, we found a significant increase in caspase-cleaved cytokeratin-18; however, the full-length form greatly exceeded the cleaved form at the time of maximum injury (45837±12085 vs 2528±1074 U/L). We also found an increase in acHMGB1 at later time points indicating a possible role of inflammation, but cytokine levels at these times were actually decreased relative to early time points.

CONCLUSIONS

The mechanism of injury following hypoxic hepatitis involves mitochondrial damage and DNA fragmentation. Importantly, necrosis, rather than apoptosis, is the main mode of cell death.

The impact of sterile inflammation in acute liver injury

BACKGROUND

The liver has a number of functions in innate immunity. These functions predispose the liver to innate immune-mediated liver injury when inflammation goes unchecked. Significant progress has been made in the last 25 years on sterile inflammatory liver injury in a number of models; however, a great deal of controversy and many questions about the nature of sterile inflammation still exist.

AIM

The goal of this article is to review sterile inflammatory liver injury using both a basic approach to what constitutes the inflammatory injury, and through examination of current models of liver injury and inflammation. This information will be tied to human patient conditions when appropriate.

RELEVANCE FOR PATIENTS

Inflammation is one of the most critical factors for managing in-patient liver disease in a number of scenarios. More information is needed for both scientists and clinicians to develop rational treatments.

Differential susceptibility to acetaminophen-induced liver injury in sub-strains of C57BL/6 mice: 6N versus 6J

Mouse models of acetaminophen (APAP) hepatotoxicity are considered relevant for the human pathophysiology. The C57BL/6 strain is most popular because it is the background strain of gene knock-out mice. However, conflicting results in the literature may have been caused by sub-strain mismatches, e.g. C57BL/6J and C57BL/6N. This study was initiated to determine the mechanism behind the sub-strain susceptibility to APAP toxicity. C57BL/6N and C57BL/6J mice were dosed with 200 mg/kg APAP and sacrificed at different time points. C57BL/6N mice developed significantly more liver injury as measured by plasma ALT activities and histology. Although there was no difference in glutathione depletion or cytochrome P450 activity between groups, C57BL/6N had a higher glutathione disulfide-to-glutathione ratio and more APAP protein adducts. C57BL/6N showed more mitochondrial translocation of phospho-JNK and BAX, and more release of mitochondrial intermembrane proteins apoptosis-inducing factor (AIF), second mitochondria-derived activator of caspases (SMAC), which caused more DNA fragmentation. The increased mitochondrial dysfunction was confirmed in vitro as C57BL/6N hepatocytes had a more precipitous drop in JC-1 fluorescence after APAP exposure.

CONCLUSION

C57BL/6N mice are more susceptible to APAP-induced hepatotoxicity, likely due to increased formation of APAP-protein adducts and a subsequent enhancement of mitochondrial dysfunction associated with aggravated nuclear DNA fragmentation.

Therapeutic targets for cholestatic liver injury

INTRODUCTION

Cholestasis is a reduction in bile flow that occurs during numerous pathologies. Blockage of the biliary tracts results in hepatic accumulation of bile acids or their conjugate bile salts. The molecular mechanisms behind liver injury associated with cholestasis are extensively studied, but not well understood. Multiple models of obstructive cholestasis result in a significant inflammatory infiltrate at the sites of necrosis that characterize the injury.

AREAS COVERED

This review will focus on direct bile acid toxicity during cholestasis, bile acid signaling processes and on the development and continuation of inflammation during cholestasis, with a focus on novel proposed molecular mediators of neutrophil recruitment. While significant progress has been made on these molecular mechanisms, a continued focus on how cholestasis and the innate immune system interact is necessary to discover targetable therapeutics that might protect the liver while leaving global immunity intact.

EXPERT OPINION

While bile acid toxicity likely occurs in humans and other mammals when toxic bile acids accumulate, persistent inflammation is likely responsible for continued liver injury during obstructive cholestasis. Targeting molecular mediators of inflammation may help prevent liver injury during acute cholestasis both in murine models and human patients.

Lack of direct cytotoxicity of extracellular ATP against hepatocytes: role in the mechanism of acetaminophen hepatotoxicity

BACKGROUND

Acetaminophen (APAP) hepatotoxicity is a major cause of acute liver failure in many countries. Mechanistic studies in mice and humans have implicated formation of a reactive metabolite, mitochondrial dysfunction and oxidant stress as critical events in the pathophysiology of APAP-induced liver cell death. It was recently suggested that ATP released from necrotic cells can directly cause cell death in mouse hepatocytes and in a hepatoma cell line (HepG2).

AIM

To assess if ATP can directly cause cell toxicity in hepatocytes and evaluate their relevance in the human system.

METHODS

Primary mouse hepatocytes, human HepG2 cells, the metabolically competent human HepaRG cell line and freshly isolated primary human hepatocytes were exposed to 10-100 µM ATP or ATγPin the presence or absence of 5-10 mM APAP for 9-24 h.

RESULTS

ATP or ATγP was unable to directly cause cell toxicity in all 4 types of hepatocytes. In addition, ATP did not enhance APAP-induced cell death observed in primary mouse or human hepatocytes, or in HepaRG cells as measured by LDH release and by propidium iodide staining in primary mouse hepatocytes. Furthermore, addition of ATP did not cause mitochondrial dysfunction or enhance APAP-induced mitochondrial dysfunction in primary murine hepatocytes, although ATP did cause cell death in murine RAW macrophages.

CONCLUSIONS

It is unlikely that ATP released from necrotic cells can significantly affect cell death in human or mouse liver during APAP hepatotoxicity.

RELEVANCE FOR PATIENTS

Understanding the mechanisms of APAP-induced cell injury is critical for identifying novel therapeutic targets to prevent liver injury and acute liver failure in APAP overdose patients.

Lack of Direct Cytotoxicity of Extracellular ATP against Hepatocytes: Role in the Mechanism of Acetaminophen Hepatotoxicity

BACKGROUND

Acetaminophen (APAP) hepatotoxicity is a major cause of acute liver failure in many countries. Mechanistic studies in mice and humans have implicated formation of a reactive metabolite, mitochondrial dysfunction and oxidant stress as critical events in the pathophysiology of APAP-induced liver cell death. It was recently suggested that ATP released from necrotic cells can directly cause cell death in mouse hepatocytes and in a hepatoma cell line (HepG2).

AIM

To assess if ATP can directly cause cell toxicity in hepatocytes and evaluate their relevance in the human system.

METHODS

Primary mouse hepatocytes, human HepG2 cells, the metabolically competent human HepaRG cell line and freshly isolated primary human hepatocytes were exposed to 10-100 μM ATP or ATγP in the presence or absence of 5-10 mM APAP for 9-24 h.

RESULTS

ATP or ATγP was unable to directly cause cell toxicity in all 4 types of hepatocytes. In addition, ATP did not enhance APAP-induced cell death observed in primary mouse or human hepatocytes, or in HepaRG cells as measured by LDH release and by propidium iodide staining in primary mouse hepatocytes. Furthermore, addition of ATP did not cause mitochondrial dysfunction or enhance APAP-induced mitochondrial dysfunction in primary murine hepatocytes, although ATP did cause cell death in murine RAW macrophages.

CONCLUSIONS

It is unlikely that ATP released from necrotic cells can significantly affect cell death in human or mouse liver during APAP hepatotoxicity.

RELEVANCE FOR PATIENTS

Understanding the mechanisms of APAP-induced cell injury is critical for identifying novel therapeutic targets to prevent liver injury and acute liver failure in APAP overdose patients.