Mechanisms of the deleterious effects of tamoxifen on mitochondrial respiration rate and phosphorylation efficiency

Inverse FASN and LDHA correlation drives metabolic resistance in breast cancer

BACKGROUND

Breast cancer manifests as a heterogeneous pathology marked by complex metabolic reprogramming essential to satisfy its energy demands. Oncogenic signals boost the metabolism, modifying fatty acid synthesis and glucose use from the onset to progression and therapy resistant-forms. However, the exact contribution of metabolic dependencies during tumor evolution remains unclear.

METHODS

In this study, we elucidate the connection between FASN and LDHA, pivotal metabolic genes, and their correlation with tumor grade and therapy response using datasets from public repositories. Subsequently, we evaluated the metabolic and proliferative functions upon FASN and LDHA inhibition in breast cancer models. Lastly, we integrated metabolomic and lipidomic analysis to define the contributions of metabolites, lipids, and precursors to the metabolic phenotypes.

RESULTS

Collectively, our findings indicate metabolic shifts during breast cancer progression, unvealling two distinct functional energy phenotypes associated with aggressiveness and therapy response. Specifically, FASN exhibits reduced expression in advance-grade tumors and therapy-resistant forms, whereas LDHA demonstrates higher expression. Additionally, the biological and metabolic impact of blocking the enzymatic activity of FASN and LDHA was correlated with resistant conditions.

CONCLUSIONS

These observations emphasize the intrinsic metabolic heterogeneity within breast cancer, thereby highlighting the relevance of metabolic interventions in the field of precision medicine.

F-box and leucine-rich repeat protein 16 controls tamoxifen sensitivity via regulation of mitochondrial respiration in estrogen receptor-positive breast cancer cells

Tamoxifen is one of the most effective therapeutic tools for estrogen receptor-positive (ER +) breast cancer. However, the intrinsic insensitivity and resistance to tamoxifen remains a significant hurdle for achieving optimal responses and curative therapy. In this study, we report that F-box and leucine-rich repeat protein 16 (FBXL16) is located in the mitochondria of ER + breast cancer cells. The mitochondrial FBXL16 plays an essential role in sustaining mitochondrial respiration and thereby regulates the sensitivity of ER + breast cancer cells to tamoxifen treatment. Importantly, high FBXL16 expression is significantly correlated with poor overall survival of ER + breast cancer patients. Moreover, mitochondrial inhibition phenocopies FBXL16 depletion in terms of sensitizing the ER + breast cancer cells to tamoxifen treatment. Together, our study demonstrates that FBXL16 acts as a novel regulator of tamoxifen sensitivity. Thus, targeting FBXL16 may serve as a promising approach for improving the therapeutic efficacy of tamoxifen in ER + breast cancer cells.

Repurposing Tamoxifen as Potential Host-Directed Therapeutic for Tuberculosis

The global burden of tuberculosis (TB) is aggravated by the continuously increasing emergence of drug resistance, highlighting the need for innovative therapeutic options. The concept of host-directed therapy (HDT) as adjunctive to classical antibacterial therapy with antibiotics represents a novel and promising approach for treating TB. Here, we have focused on repurposing the clinically used anticancer drug tamoxifen, which was identified as a molecule with strong host-directed activity against intracellular Mycobacterium tuberculosis (Mtb). Using a primary human macrophage Mtb infection model, we demonstrate the potential of tamoxifen against drug-sensitive as well as drug-resistant Mtb bacteria. The therapeutic effect of tamoxifen was confirmed in an in vivo TB model based on Mycobacterium marinum infection of zebrafish larvae. Tamoxifen had no direct antimicrobial effects at the concentrations used, confirming that tamoxifen acted as an HDT drug. Furthermore, we demonstrate that the antimycobacterial effect of tamoxifen is independent of its well-known target the estrogen receptor (ER) pathway, but instead acts by modulating autophagy, in particular the lysosomal pathway. Through RNA sequencing and microscopic colocalization studies, we show that tamoxifen stimulates lysosomal activation and increases the localization of mycobacteria in lysosomes both in vitro and in vivo, while inhibition of lysosomal activity during tamoxifen treatment partly restores mycobacterial survival. Thus, our work highlights the HDT potential of tamoxifen and proposes it as a repurposed molecule for the treatment of TB. IMPORTANCE Tuberculosis (TB) is the world's most lethal infectious disease caused by a bacterial pathogen, Mycobacterium tuberculosis. This pathogen evades the immune defenses of its host and grows intracellularly in immune cells, particularly inside macrophages. There is an urgent need for novel therapeutic strategies because treatment of TB patients is increasingly complicated by rising antibiotic resistance. In this study, we explored a breast cancer drug, tamoxifen, as a potential anti-TB drug. We show that tamoxifen acts as a so-called host-directed therapeutic, which means that it does not act directly on the bacteria but helps the host macrophages combat the infection more effectively. We confirmed the antimycobacterial effect of tamoxifen in a zebrafish model for TB and showed that it functions by promoting the delivery of mycobacteria to digestive organelles, the lysosomes. These results support the high potential of tamoxifen to be repurposed to fight antibiotic-resistant TB infections by host-directed therapy.

Tamoxifen induces radioresistance through NRF2-mediated metabolic reprogramming in breast cancer

BACKGROUND

Recently, we reported that tamoxifen-resistant (TAM-R) breast cancer cells are cross-resistant to irradiation. Here, we investigated the mechanisms associated with tamoxifen-induced radioresistance, aiming to prevent or reverse resistance and improve breast cancer treatment.

METHODS

Wild-type ERα-positive MCF7 and ERα-negative MDA-MB-231 breast cancer cells and their TAM-R counterparts were analyzed for cellular metabolism using the Seahorse metabolic analyzer. Real-time ROS production, toxicity, and antioxidant capacity in response to H2O2, tamoxifen, and irradiation were determined. Tumor material from 28 breast cancer patients before and after short-term presurgical tamoxifen (ClinicalTrials.gov Identifier: NCT00738777, August 19, 2008) and cellular material was analyzed for NRF2 gene expression and immunohistochemistry. Re-sensitization of TAM-R cells to irradiation was established using pharmacological inhibition.

RESULTS

TAM-R cells exhibited decreased oxygen consumption and increased glycolysis, suggesting mitochondrial dysfunction. However, this did not explain radioresistance, as cells without mitochondria (Rho-0) were actually more radiosensitive. Real-time measurement of ROS after tamoxifen and H2O2 exposure indicated lower ROS levels and toxicity in TAM-R cells. Consistently, higher antioxidant levels were found in TAM-R cells, providing protection from irradiation-induced ROS. NRF2, a main activator of the antioxidant response, was increased in TAM-R cells and in tumor tissue of patients treated with short-term presurgical tamoxifen. NRF2 inhibition re-sensitized TAM-R cells to irradiation.

CONCLUSION

Mechanisms underlying tamoxifen-induced radioresistance are linked to cellular adaptations to persistently increased ROS levels, leading to cells with chronically upregulated antioxidant capacity and glycolysis. Pharmacological inhibition of antioxidant responses re-sensitizes breast cancer cells to irradiation.

Mitochondrial adaptation in cancer drug resistance: prevalence, mechanisms, and management

Drug resistance represents a major obstacle in cancer management, and the mechanisms underlying stress adaptation of cancer cells in response to therapy-induced hostile environment are largely unknown. As the central organelle for cellular energy supply, mitochondria can rapidly undergo dynamic changes and integrate cellular signaling pathways to provide bioenergetic and biosynthetic flexibility for cancer cells, which contributes to multiple aspects of tumor characteristics, including drug resistance. Therefore, targeting mitochondria for cancer therapy and overcoming drug resistance has attracted increasing attention for various types of cancer. Multiple mitochondrial adaptation processes, including mitochondrial dynamics, mitochondrial metabolism, and mitochondrial apoptotic regulatory machinery, have been demonstrated to be potential targets. However, recent increasing insights into mitochondria have revealed the complexity of mitochondrial structure and functions, the elusive functions of mitochondria in tumor biology, and the targeting inaccessibility of mitochondria, which have posed challenges for the clinical application of mitochondrial-based cancer therapeutic strategies. Therefore, discovery of both novel mitochondria-targeting agents and innovative mitochondria-targeting approaches is urgently required. Here, we review the most recent literature to summarize the molecular mechanisms underlying mitochondrial stress adaptation and their intricate connection with cancer drug resistance. In addition, an overview of the emerging strategies to target mitochondria for effectively overcoming chemoresistance is highlighted, with an emphasis on drug repositioning and mitochondrial drug delivery approaches, which may accelerate the application of mitochondria-targeting compounds for cancer therapy.

Inducible Systemic Gcn1 Deletion in Mice Leads to Transient Body Weight Loss upon Tamoxifen Treatment Associated with Decrease of Fat and Liver Glycogen Storage

GCN1 is an evolutionarily-conserved ribosome-binding protein that mediates the amino acid starvation response as well as the ribotoxic stress response. We previously demonstrated that Gcn1 mutant mice lacking the GCN2-binding domain suffer from growth retardation and postnatal lethality via GCN2-independent mechanisms, while Gcn1-null mice die early in embryonic development. In this study, we explored the role of GCN1 in adult mice by generating tamoxifen-inducible conditional knockout (CKO) mice. Unexpectedly, the Gcn1 CKO mice showed body weight loss during tamoxifen treatment, which gradually recovered following its cessation. They also showed decreases in liver weight, hepatic glycogen and lipid contents, blood glucose and non-esterified fatty acids, and visceral white adipose tissue weight with no changes in food intake and viability. A decrease of serum VLDL suggested that hepatic lipid supply to the peripheral tissues was primarily impaired. Liver proteomic analysis revealed the downregulation of mitochondrial β-oxidation that accompanied increases of peroxisomal β-oxidation and aerobic glucose catabolism that maintain ATP levels. These findings show the involvement of GCN1 in hepatic lipid metabolism during tamoxifen treatment in adult mice.

Comprehensive understanding of multiple actions of anticancer drug tamoxifen in isolated mitochondria

Tamoxifen has been widely used in the treatment of estrogen receptor (ER)-positive breast cancer, whereas it also exhibits ER-independent anticancer effects in various cancer cell types. As one of the convincing mechanisms underlying the ER-independent effects, induction of apoptosis through mitochondrial dysfunction has been advocated. However, the mechanism of action of tamoxifen even at the isolated mitochondrial level is not fully understood and remains controversial. Here, we attempted to comprehensively understand tamoxifen's multiple actions in isolated rat liver mitochondria through not only revisiting the actions hitherto reported but also conducting originally designed experiments. Using submitochondrial particles, we found that tamoxifen has potential as an inhibitor of both respiratory complex I and ATP synthase. However, these inhibitory effects were not elicited in intact mitochondria, likely because penetration of tamoxifen across the inner mitochondrial membrane is highly restricted owing to its localized positive charge (-N+H(CH3)2). This restricted penetration may also explain why tamoxifen is unable to function as a protonophore-type uncoupler in mitochondria. Moreover, tamoxifen suppressed opening of the mitochondrial permeability transition pore induced by Ca2+ overload through enhancing phosphate uptake into the matrix. The photoaffinity labeling experiments using a photolabile tamoxifen derivative (pTAM1) indicated that pTAM1 specifically binds to voltage-dependent anion channels (VDACs) 1 and 3, which regulate transport of various substances into mitochondria. The binding of tamoxifen to VDAC1 and/or VDAC3 could be responsible for the enhancement of phosphate uptake. Taking all the results together, we consider the principal impairment of mitochondrial functions caused by tamoxifen.

Mitochondria as a Novel Target for Cancer Chemoprevention: Emergence of Mitochondrial-targeting Agents

Cancer chemoprevention is the most effective approach to control cancer in the population. Despite significant progress, chemoprevention has not been widely adopted because agents that are safe tend to be less effective and those that are highly effective tend to be toxic. Thus, there is an urgent need to develop novel and effective chemopreventive agents, such as mitochondria-targeted agents, that can prevent cancer and prolong survival. Mitochondria, the central site for cellular energy production, have important functions in cell survival and death. Several studies have revealed a significant role for mitochondrial metabolism in promoting cancer development and progression, making mitochondria a promising new target for cancer prevention. Conjugating delocalized lipophilic cations, such as triphenylphosphonium cation (TPP+), to compounds of interest is an effective approach for mitochondrial targeting. The hyperpolarized tumor cell membrane and mitochondrial membrane potential allow for selective accumulation of TPP⁺ conjugates in tumor cell mitochondria versus those in normal cells. This could enhance direct killing of precancerous, dysplastic, and tumor cells while minimizing potential toxicities to normal cells.

Mitochondrial dysfunction and apoptosis underlie the hepatotoxicity of perhexiline

Perhexiline is an anti-anginal drug developed in the late 1960s. Despite its therapeutic success, it caused severe hepatoxicity in selective patients, which resulted in its withdrawal from the market. In the current study we explored the molecular mechanisms underlying the cytotoxicity of perhexiline. In primary human hepatocytes, HepaRG cells, and HepG2 cells, perhexiline induced cell death in a concentration- and time-dependent manner. Perhexiline treatment also caused a significant increase in caspase 3/7 activity at 2 h and 4 h. Pretreatment with specific caspase inhibitors suggested that both intrinsic and extrinsic apoptotic pathways contributed to perhexiline-induced cytotoxicity, which was confirmed by increased expression of TNF-α, cleavage of caspase 3 and 9 upon perhexiline treatment. Moreover, perhexiline caused mitochondrial dysfunction, demonstrated by the classic glucose-galactose assay at 4 h and 24 h. Results from JC-1 staining suggested perhexiline caused loss of mitochondrial potential. Blocking mitochondrial permeability transition pore using inhibitor bongkrekic acid attenuated the cytotoxicity of perhexiline. Western blotting analysis also showed decreased expression level of pro-survival proteins Bcl-2 and Mcl-1, and increased expression of pro-apoptotic protein Bad. Direct measurement of the activity of individual components of the mitochondrial respiratory complex demonstrated that perhexiline strongly inhibited Complex IV and Complex V and moderately inhibited Complex II and Complex II + III. Overall, our data demonstrated that both mitochondrial dysfunction and apoptosis underlies perhexiline-induced hepatotoxicity.

From old to new - Repurposing drugs to target mitochondrial energy metabolism in cancer

Although we have entered the era of personalized medicine and tailored therapies, drugs that target a large variety of cancers regardless of individual patient differences would be a major advance nonetheless. This review article summarizes current concepts and therapeutic opportunities in the area of targeting aerobic mitochondrial energy metabolism in cancer. Old drugs previously used for diseases other than cancer, such as antibiotics and antidiabetics, have the potential to inhibit the growth of various tumor entities. Many drugs are reported to influence mitochondrial metabolism. However, here we consider only those drugs which predominantly inhibit oxidative phosphorylation.

Alteration of mitochondrial DNA homeostasis in drug-induced liver injury

Mitochondrial DNA (mtDNA) encodes for 13 proteins involved in the oxidative phosphorylation (OXPHOS) process. In liver, genetic or acquired impairment of mtDNA homeostasis can reduce ATP output but also decrease fatty acid oxidation, thus leading to different hepatic lesions including massive necrosis and microvesicular steatosis. Hence, a severe impairment of mtDNA homeostasis can lead to liver failure and death. An increasing number of investigations report that some drugs can induce mitochondrial dysfunction and drug-induced liver injury (DILI) by altering mtDNA homeostasis. Some drugs such as ciprofloxacin, antiretroviral nucleoside reverse-transcriptase inhibitors and tacrine can inhibit hepatic mtDNA replication, thus inducing mtDNA depletion. Drug-induced reduced mtDNA levels can also be the consequence of reactive oxygen species-mediated oxidative damage to mtDNA, which triggers its degradation by mitochondrial nucleases. Such mechanism is suspected for acetaminophen and troglitazone. Other pharmaceuticals such as linezolid and tetracyclines can impair mtDNA translation, thus selectively reducing the synthesis of the 13 mtDNA-encoded proteins. Lastly, some drugs might alter the mtDNA methylation status but the pathophysiological consequences of such alteration are still unclear. Drug-induced impairment of mtDNA homeostasis is probably under-recognized since preclinical and post-marketing safety studies do not classically investigate mtDNA levels, mitochondrial protein synthesis and mtDNA oxidative damage.

Review article: drug-induced liver injury in the context of nonalcoholic fatty liver disease - a physiopathological and clinical integrated view

BACKGROUND

Nonalcoholic fatty disease (NAFLD) is the most common liver disease, since it is strongly associated with obesity and metabolic syndrome pandemics. NAFLD may affect drug disposal and has common pathophysiological mechanisms with drug-induced liver injury (DILI); this may predispose to hepatoxicity induced by certain drugs that share these pathophysiological mechanisms. In addition, drugs may trigger fatty liver and inflammation per se by mimicking NAFLD pathophysiological mechanisms.

AIMS

To provide a comprehensive update on (a) potential mechanisms whereby certain drugs can be more hepatotoxic in NAFLD patients, (b) the steatogenic effects of drugs, and (c) the mechanism involved in drug-induced steatohepatitis (DISH).

METHODS

A language- and date-unrestricted Medline literature search was conducted to identify pertinent basic and clinical studies on the topic.

RESULTS

Drugs can induce macrovesicular steatosis by mimicking NAFLD pathogenic factors, including insulin resistance and imbalance between fat gain and loss. Other forms of hepatic fat accumulation exist, such as microvesicular steatosis and phospholipidosis, and are mostly associated with acute mitochondrial dysfunction and defective lipophagy, respectively. Drug-induced mitochondrial dysfunction is also commonly involved in DISH. Patients with pre-existing NAFLD may be at higher risk of DILI induced by certain drugs, and polypharmacy in obese individuals to treat their comorbidities may be a contributing factor.

CONCLUSIONS

The relationship between DILI and NAFLD may be reciprocal: drugs can cause NAFLD by acting as steatogenic factors, and pre-existing NAFLD could be a predisposing condition for certain drugs to cause DILI. Polypharmacy associated with obesity might potentiate the association between this condition and DILI.

Immunosuppressant drug tacrolimus induced mitochondrial nephrotoxicity, modified PCNA and Bcl-2 expression attenuated by Ocimum basilicum L. in CD1 mice

Tacrolimus (TAC) is used sporadically as an immunosuppressive agent for organ transplantation, but its clinical used is limited due to its marked nephrotoxicity. Ocimum basilicum L. (Lamiaceae) (OB) had been shown to possess antioxidant, anti-inflammatory and nephroprotective activity, and effective at improving renal inflammation and glomerular. In our study, we aim to evaluate the efficacy of the OB against TAC-induced mitochondrial nephrotoxicity in CD1 mice. Mice were randomly divided into four groups. Group 1 (control group); administered orally with normal saline (1 mL/kg) for two weeks; Group 2 (OB extract treated-group) (500 mg/kg b.wt) gavaged once/day for two weeks; Group 3 (TAC-treated group) (3 mg/kg b.wt, administered ip once a day for two weeks); and Group 4; (TAC plus OB extract treated-group). Tacrolimus-induced nephrotoxicity was assessed biochemically and histopathologically. The OB extract was high in phenolic content (50.3 mg/g of gallic acid equivalent), total flavonoids (14.5 mg/g CE equivalent). The potential antioxidant efficacy of the extract (IC50) was 24.5 μg/mL. OB pretreatment significantly improved the TAC-induced changes in biochemical markers of nephrotoxicity for instance blood urea nitrogen (BUN), creatinine, total protein, and albumin (P < 0.01, when compared with TAC treated group). Also, it significantly restored the increase activities of TBARS, protein carbonyl (PC) (P < 0.001, when compared to healthy control group) and decreased activities of nonprotein thiol (NP-SH) levels, Mn-superoxide dismutase (Mn-SOD) and glutathione peroxidase (GPx) antioxidants of mitochondria. The nephroprotective efficacy of the OB leaves extract was further evident by histopathological analysis together with the PCNA-ir and Bcl2. The upshot of the present study revealed that the OB possessed significant antioxidant and nephroprotective activity and had a preventive effect on the biochemical alterations and histological changes in TAC-treated mice.

Mechanisms of Neurotoxic Symptoms as a Result of Breast Cancer and Its Treatment: Considerations on the Contribution of Stress, Inflammation, and Cellular Bioenergetics

PURPOSE OF REVIEW

Breast cancer and its treatment are associated with a range of neurotoxic symptoms, such as fatigue, cognitive impairment, and pain. Although these symptoms generally subside after treatment completion, they become chronic in a significant subset of patients. We here summarize recent findings on neuroinflammation, stress, and mitochondrial dysfunction as mechanistic pathways leading to neurotoxic symptom experience in breast cancer patients and survivors.

RECENT FINDINGS

Neuroinflammation related to stress or cancer treatment and stress resulting from diagnosis, treatment, or (cancer-related) worrying are important predictors of a neurotoxic symptom experience, both during and after treatment for breast cancer. Both inflammation and stress hormones, as well as cancer treatment, can induce mitochondrial dysfunction resulting in reduced cellular energy.

SUMMARY

We propose reduced cellular energy (mitochondrial dysfunction) induced by inflammation, oxygen radical production, and stress as a result of cancer and/or cancer treatment as a final mechanism underlying neurotoxic symptoms.

Antibiotic-non-antibiotic combinations for combating extremely drug-resistant Gram-negative 'superbugs'

The emergence of antimicrobial resistance of Gram-negative pathogens has become a worldwide crisis. The status quo for combating resistance is to employ synergistic combinations of antibiotics. Faced with this fast-approaching post-antibiotic era, it is critical that we devise strategies to prolong and maximize the clinical efficacy of existing antibiotics. Unfortunately, reports of extremely drug-resistant (XDR) Gram-negative pathogens have become more common. Combining antibiotics such as polymyxin B or the broad-spectrum tetracycline and minocycline with various FDA-approved non-antibiotic drugs have emerged as a novel combination strategy against otherwise untreatable XDR pathogens. This review surveys the available literature on the potential benefits of employing antibiotic-non-antibiotic drug combination therapy. The apex of this review highlights the clinical utility of this novel therapeutic strategy for combating infections caused by 'superbugs'.

Role of nonalcoholic fatty liver disease as risk factor for drug-induced hepatotoxicity

BACKGROUND

Obesity is often associated with nonalcoholic fatty liver disease (NAFLD), which refers to a large spectrum of hepatic lesions including fatty liver, nonalcoholic steatohepatitis (NASH) and cirrhosis. Different investigations showed or suggested that obesity and NAFLD are able to increase the risk of hepatotoxicity of different drugs. Some of these drugs could induce more frequently an acute hepatitis in obese individuals whereas others could worsen pre-existing NAFLD.

AIM

The main objective of the present review was to collect the available information regarding the role of NAFLD as risk factor for drug-induced hepatotoxicity. For this purpose, we performed a data-mining analysis using different queries including drug-induced liver injury (or DILI), drug-induced hepatotoxicity, fatty liver, nonalcoholic fatty liver disease (or NAFLD), steatosis and obesity. The main data from the collected articles are reported in this review and when available, some pathophysiological hypotheses are put forward.

RELEVANCE FOR PATIENTS

Drugs that could pose a potential risk in obese patients include compounds belonging to different pharmacological classes such as acetaminophen, halothane, methotrexate, rosiglitazone, stavudine and tamoxifen. For some of these drugs, experimental investigations in obese rodents confirmed the clinical observations and unveiled different pathophysiological mechanisms which could explain why these pharmaceuticals are particularly hepatotoxic in obesity and NAFLD. Other drugs such as pentoxifylline, phenobarbital and omeprazole might also pose a risk but more investigations are required to determine whether this risk is significant or not. Because obese people often take several drugs for the treatment of different obesity-related diseases such as type 2 diabetes, hyperlipidemia and coronary heart disease, it is urgent to identify the main pharmaceuticals that can cause acute hepatitis on a fatty liver background or induce NAFLD worsening.

The Importance of Patient-Specific Factors for Hepatic Drug Response and Toxicity

Responses to drugs and pharmacological treatments differ considerably between individuals. Importantly, only 50%-75% of patients have been shown to react adequately to pharmacological interventions, whereas the others experience either a lack of efficacy or suffer from adverse events. The liver is of central importance in the metabolism of most drugs. Because of this exposed status, hepatotoxicity is amongst the most common adverse drug reactions and hepatic liabilities are the most prevalent reason for the termination of development programs of novel drug candidates. In recent years, more and more factors were unveiled that shape hepatic drug responses and thus underlie the observed inter-individual variability. In this review, we provide a comprehensive overview of different principle mechanisms of drug hepatotoxicity and illustrate how patient-specific factors, such as genetic, physiological and environmental factors, can shape drug responses. Furthermore, we highlight other parameters, such as concomitantly prescribed medications or liver diseases and how they modulate drug toxicity, pharmacokinetics and dynamics. Finally, we discuss recent progress in the field of in vitro toxicity models and evaluate their utility in reflecting patient-specific factors to study inter-individual differences in drug response and toxicity, as this understanding is necessary to pave the way for a patient-adjusted medicine.

Tamoxifen enhances the cytotoxicity of conventional chemotherapy in esophageal adenocarcinoma cells

INTRODUCTION

Esophageal adenocarcinoma is a lethal malignancy which is increasing in incidence, and many patients receive chemotherapy as part of their treatment. We have previously demonstrated that esophageal adenocarcinoma-derived cell lines respond to treatment with estrogen receptor modulators, such as tamoxifen. Reports from breast cancer suggest that tamoxifen may attenuate the efficacy of other chemotherapeutic agents. We have therefore assessed the response of esophageal adenocarcinoma cell lines to tamoxifen therapy when given in combination with conventional agents.

METHODS

Two estrogen receptor (ER)-positive esophageal adenocarcinoma cell lines (OE-19 and OE-33) were treated with combinations of tamoxifen, cisplatin and 5-fluorouracil (5-FU). Effects on cell viability were measured using an MTS assay, and cell death was detected with annexin V/propidium iodide flow cytometry. To assess whether the efficacy of tamoxifen in these cell lines might be relevant to the clinical setting, we analyzed ER status in 10 esophageal adenocarcinoma tissue specimens by immunohistochemistry.

RESULTS

IC50 values (μM) for OE-19 and OE-33 were 11.2 and 7.1 for tamoxifen, 19.6 and 4.7 for cisplatin, and 1.7 and 5.9 for 5-FU, respectively. Cell death was detected in 11.9% and 15.8% of cells treated with tamoxifen, 7.9% and 8.7% cells treated with cisplatin, and 3.6% and 8.6% cells treated with 5-FU at their IC50s. The addition of tamoxifen to cisplatin increased cell death by 11.4% in OE-19 (p < 0.0001) and 16.3% in OE-33 (p < 0.0001). Similarly, the addition of tamoxifen to 5-FU increased cell death by 11.6% in OE-19 (p < 0.0001) and 15.9% in OE-33 (p < 0.0001). Eight of 10 tissue specimens showed positive staining for ERα and 7 of 10 for ERβ.

CONCLUSIONS

In a cell culture model the addition of tamoxifen to conventional chemotherapy appears to be both feasible and beneficial. Expression of ERα and ERβ was also confirmed in esophageal adenocarcinoma tissues.

Drug-induced fatty liver disease: An overview of pathogenesis and management

Over the past decades, many drugs have been identified, that can potentially induce steatohepatitis in the predisposed individual. Classically this has been incriminated to amiodarone, perhexiline, and 4,4'-diethylaminoethoxyhexestrol (DH), all of which have been found to independently induce the histologic picture of non-alcoholic steatohepatitis (NASH). Pathogenetic mechanisms of hepatotoxicity although still evolving, demonstrate that mitochondrial dysfunction, deranged ATP production and fatty acid catabolism likely play an important role. Drugs like steroid hormones can exacerbate the pathogenetic mechanisms that lead to NASH, and other drugs like tamoxifen, cisplatin and irenotecan have been shown to precipitate latent fatty liver as well. Further research aiming to elucidate the pathogenesis of drug-induced steatosis and steatohepatitis is needed in order to better design therapeutic targets.

Deciphering the Nongenomic, Mitochondrial Toxicity of Tamoxifens As Determined by Cell Metabolism and Redox Activity

Tamoxifen is not only considered a very potent chemotherapeutic adjuvant for estrogen receptor positive breast cancers but also a very good chemo-preventive drug. Recently, there has been a rising amount of evidence for a nongenomic cytotoxicity of tamoxifen, even in estrogen receptor negative cells, which has greatly confounded researchers. Clinically, the side effects of tamoxifen can be very serious, ranging from liver steatosis to cirrhosis, tumorigenesis, or onset of porphyrias. Herein, we deciphered the nongenomic, mitochondrial cytotoxicity of tamoxifen in estrogen receptor positive MCF7 versus triple-negative MDA-MB-231 cells, employing the mitochondrial complex III quinoloxidizing-center inhibitor myxothiazol. We showed a role for hydroxyl-radical-mediated lipid peroxidation, catalyzed by iron, stemming from the redox interactions of tamoxifen quinoid metabolites with complex III, resulting in Fenton-capable reduced quinones. The role of tamoxifen semiquinone species in mitochondrial toxicity was also shown together with evidence of mitochondrial DNA damage. Tamoxifen caused an overall metabolic (respiratory and glycolytic) rate decrease in the Pasteur type MCF cells, while in the Warburg type MDA-MB-231 cells the respiratory rate was not significantly affected and the glycolytiv rate was significantly boosted. The nongenomic cytotoxicity of tamoxifens was hence associated with the metabolic phenotype and redox activity of the cells, as in the present paradigm of Pasteur MCF7s versus Warburg MDA-MB-231 cells. Our present findings call for caution in the use of the drugs, especially as a chemopreventive and/or in cases of iron overload diseases.

Chemotherapeutic effect of tamoxifen on temozolomide-resistant gliomas

Tamoxifen, a selective estrogen receptor modulator, is widely used in the chemotherapy of estrogen receptor-positive breast cancer. Recent studies have indicated that tamoxifen might have a potential chemotherapeutic effect on glioma. In the present study, we determined the chemotherapeutic action of tamoxifen on human glioma cell lines. Methylation of 06-methylguanine-DNA methyltransferase was identified in A172, U251, and BT325 glioma cell lines, but not in the U87 cell line. Consistently, A172, U251, and BT325 cell lines are resistant to temozolomide. Tamoxifen induced significant cytotoxic action in A172, U251, BT325, and U87 cell lines. Further, Hoechst 33342 staining and apoptosis flow cytometric analysis demonstrated that tamoxifen induced apoptosis in the BT325 cell line. Mitochondrial complex analysis indicated that tamoxifen, but not other estrogen receptor modulators, dose-dependently inhibits complex I activity. In summary, our study suggests that tamoxifen might have a chemotherapeutic effect on temozolomide-resistant glioma through its direct action on mitochondrial complex I inhibition and could provide further evidence to support future clinical trials of tamoxifen for the treatment of glioblastoma.

Strategies, models and biomarkers in experimental non-alcoholic fatty liver disease research

Non-alcoholic fatty liver disease encompasses a spectrum of liver diseases, including simple steatosis, steatohepatitis, liver fibrosis and cirrhosis and hepatocellular carcinoma. Non-alcoholic fatty liver disease is currently the most dominant chronic liver disease in Western countries due to the fact that hepatic steatosis is associated with insulin resistance, type 2 diabetes mellitus, obesity, metabolic syndrome and drug-induced injury. A variety of chemicals, mainly drugs, and diets is known to cause hepatic steatosis in humans and rodents. Experimental non-alcoholic fatty liver disease models rely on the application of a diet or the administration of drugs to laboratory animals or the exposure of hepatic cell lines to these drugs. More recently, genetically modified rodents or zebrafish have been introduced as non-alcoholic fatty liver disease models. Considerable interest now lies in the discovery and development of novel non-invasive biomarkers of non-alcoholic fatty liver disease, with specific focus on hepatic steatosis. Experimental diagnostic biomarkers of non-alcoholic fatty liver disease, such as (epi)genetic parameters and '-omics'-based read-outs are still in their infancy, but show great promise. In this paper, the array of tools and models for the study of liver steatosis is discussed. Furthermore, the current state-of-art regarding experimental biomarkers such as epigenetic, genetic, transcriptomic, proteomic and metabonomic biomarkers will be reviewed.

Cachexia: a problem of energetic inefficiency

An alteration of energy balance is the immediate cause of the so-called cachexia. Although alterations of energy intake are often associated with cachexia, it has lately became clear that an increased energy expenditure is the main cause of wasting associated with different types of pathological conditions, such as cancer, infections or chronic heart failure among others. Different types of molecular mechanisms contribute to energy expenditure and, therefore, involuntary body weight loss; among them, adenosine triphosphate (ATP) consumption by sarcoplasmic reticulum Ca(2+) pumps could represent a key mechanism. In other cases, an increase in energy inefficiency will further contribute to energy imbalance.

Mitochondrial toxicity in human pregnancy: an update on clinical and experimental approaches in the last 10 years

Mitochondrial toxicity can be one of the most dreadful consequences of exposure to a wide range of external agents including pathogens, therapeutic agents, abuse drugs, toxic gases and other harmful chemical substances. However, little is known about the effects of mitochondrial toxicity on pregnant women exposed to these agents that may exert transplacental activity and condition fetal remodeling. It has been hypothesized that mitochondrial toxicity may be involved in some adverse obstetric outcomes. In the present study, we investigated the association between exposure to mitochondrial toxic agents and pathologic conditions ranging from fertility defects, detrimental fetal development and impaired newborn health due to intra-uterine exposure. We have reviewed data from studies in human subjects to propose mechanisms of mitochondrial toxicity that could be associated with the symptoms present in both exposed pregnant and fetal patients. Since some therapeutic interventions or accidental exposure cannot be avoided, further research is needed to gain insight into the molecular pathways leading to mitochondrial toxicity during pregnancy. The ultimate objective of these studies should be to reduce the mitochondrial toxicity of these agents and establish biomarkers for gestational monitoring of harmful effects.

Mitochondria: the gateway for tamoxifen-induced liver injury

Tamoxifen (TAM) is routinely used in the treatment of breast carcinoma. TAM-induced liver injury remains a major concern, as TAM causes hepatic steatosis in a significant number of patients, which can progress toward steatohepatitis. Liver toxicity is generally believed to involve mitochondrial dysfunction and TAM exerts multiple deleterious effects on mitochondria, which may account for the hepatotoxicity observed in patients treated with TAM. Endoxifen (EDX), a key active metabolite of TAM that is being investigated as an alternative to TAM in breast cancer therapy, slightly affects mitochondria in comparison with TAM and this demonstration well correlates with the absence of alterations in the clinical parameters of individuals taking EDX. The steady-state plasma concentrations of TAM and its active metabolites EDX and 4-hydroxytamoxifen (OHTAM) in patients taking TAM are highly variable, reflecting genetic variants of CYP2D6 involved in TAM metabolism. Besides de genetic polymorphisms, the intake of drugs that influence the enzymatic activity of CYP2D6 compromises the therapeutic efficiency of TAM. The knowledge of the impact of the variability of TAM metabolism in the breast cancer treatment explains the discrepant outcomes observed in patients taking TAM, as well as the individual variability of idiosyncratic liver injury and other sides effects observed. Therefore, and contrarily to the clinical use of EDX, the need of therapeutic drug monitoring and a regular assessment of liver function biomarkers should be considered in patients under therapies with TAM. In this review we focus on the mitochondrial effects of TAM and its metabolites and on the role played by mitochondria in the initiating events leading to TAM-induced hepatotoxicity, as well as the clinical implications.

A systematic assessment of mitochondrial function identified novel signatures for drug-induced mitochondrial disruption in cells

Mitochondrial perturbation has been recognized as a contributing factor to various drug-induced organ toxicities. To address this issue, we developed a high-throughput flow cytometry-based mitochondrial signaling assay to systematically investigate mitochondrial/cellular parameters known to be directly impacted by mitochondrial dysfunction: mitochondrial membrane potential (MMP), mitochondrial reactive oxygen species (ROS), intracellular reduced glutathione (GSH) level, and cell viability. Modulation of these parameters by a training set of compounds, comprised of established mitochondrial poisons and 60 marketed drugs (30 nM to 1mM), was tested in HL-60 cells (a human pro-myelocytic leukemia cell line) cultured in either glucose-supplemented (GSM) or glucose-free (containing galactose/glutamine; GFM) RPMI-1640 media. Post-hoc bio-informatic analyses of IC50 or EC50 values for all parameters tested revealed that MMP depolarization in HL-60 cells cultured in GSM was the most reliable parameter for determining mitochondrial dysfunction in these cells. Disruptors of mitochondrial function depolarized MMP at concentrations lower than those that caused loss of cell viability, especially in cells cultured in GSM; cellular GSH levels correlated more closely to loss of viability in vitro. Some mitochondrial respiratory chain inhibitors increased mitochondrial ROS generation; however, measuring an increase in ROS alone was not sufficient to identify mitochondrial disruptors. Furthermore, hierarchical cluster analysis of all measured parameters provided confirmation that MMP depletion, without loss of cell viability, was the key signature for identifying mitochondrial disruptors. Subsequent classification of compounds based on ratios of IC50s of cell viability:MMP determined that this parameter is the most critical indicator of mitochondrial health in cells and provides a powerful tool to predict whether novel small molecule entities possess this liability.

Uridine prevents tamoxifen-induced liver lipid droplet accumulation

BACKGROUND

Tamoxifen, an agonist of estrogen receptor, is widely prescribed for the prevention and long-term treatment of breast cancer. A side effect of tamoxifen is fatty liver, which increases the risk for non-alcoholic fatty liver disease. Prevention of tamoxifen-induced fatty liver has the potential to improve the safety of long-term tamoxifen usage.

METHODS

Uridine, a pyrimidine nucleoside with reported protective effects against drug-induced fatty liver, was co-administered with tamoxifen in C57BL/6J mice. Liver lipid levels were evaluated with lipid visualization using coherent anti-Stokes Raman scatting (CARS) microscopy, biochemical assay measurement of triacylglyceride (TAG), and liquid chromatography coupled with mass spectrometry (LC-MS) measurement of membrane phospholipid. Blood TAG and cholesterol levels were measured. Mitochondrial respiration of primary hepatocytes in the presence of tamoxifen and/or uridine was evaluated by measuring oxygen consumption rate with an extracellular flux analyzer. Liver protein lysine acetylation profiles were evaluated with 1D and 2D Western blots. In addition, the relationship between endogenous uridine levels, fatty liver, and tamoxifen administration was evaluated in transgenic mice UPase1-/-and UPase1-TG.

RESULTS

Uridine co-administration prevented tamoxifen-induced liver lipid droplet accumulation in mice. The most prominent effect of uridine co-administration with tamoxifen was the stimulation of liver membrane phospholipid biosynthesis. Uridine had no protective effect against tamoxifen-induced impairment to mitochondrial respiration of primary hepatocytes or liver TAG and cholesterol export. Uridine had no effect on tamoxifen-induced changes to liver protein acetylation profile. Transgenic mice UPase1-/-with increased pyrimidine salvage activity were protected against tamoxifen-induced liver lipid droplet accumulation. In contrast, UPase1-TG mice with increased pyrimidine catabolism activity had intrinsic liver lipid droplet accumulation, which was aggravated following tamoxifen administration.

CONCLUSION

Uridine co-administration was effective at preventing tamoxifen-induced liver lipid droplet accumulation. The ability of uridine to prevent tamoxifen-induced fatty liver appeared to depend on the pyrimidine salvage pathway, which promotes biosynthesis of membrane phospholipid.

The combination of the antiestrogen endoxifen with all-trans-retinoic acid has anti-proliferative and anti-migration effects on melanoma cells without inducing significant toxicity in non-neoplasic cells

Melanoma incidence is dramatically increasing and the available treatments beyond partial efficacy have severe side effects. Retinoids are promising anticancer agents, but their clinical use has been limited by their toxicity, although a combination with other agents can possibly generate a therapeutic action at lower dosage. Thus, we investigated the effects of all-trans-retinoic acid combined with the antiestrogen endoxifen on melanoma cell proliferation and the effects were compared with its pro-drug tamoxifen. Moreover, we evaluated the effects of these combinations on non-neoplasic cells and assessed mitochondrial bioenergetic functions, to predict their potential toxicity. Individually, all-trans-retinoic acid and the antiestrogens endoxifen and tamoxifen decreased melanoma cell biomass, cell viability and DNA synthesis, without increased cell death, suggesting that the compounds inhibited cell proliferation. Noteworthy, endoxifen decreased cell proliferation more efficiently than tamoxifen. The combination of endoxifen with all-trans-retinoic acid enhanced the antiproliferative effects of the compounds individually more potently than tamoxifen, which did not enhance the effects induced by all-trans-retinoic acid alone, and blocked cell cycle progression in G1. Moreover, the combination of all-trans-retinoic acid with endoxifen significantly decreased melanoma cells migration, whereas the combination with tamoxifen did not present significant effects. At the concentrations used the compounds did not induce cytotoxicity in non-neoplasic cells and liver mitochondrial bioenergetic function was not affected. Altogether, our results show for the first time that a combined treatment of all-trans-retinoic acid with endoxifen may provide an anti-proliferative and anti-migration effect upon melanoma cells without major toxicity, offering a powerful therapeutic strategy for malignant melanoma.

Acitretin affects bioenergetics of liver mitochondria and promotes mitochondrial permeability transition: potential mechanisms of hepatotoxicity

Acitretin is a synthetic retinoid used for severe extensive psoriasis and it has been shown to be an effective and a safe therapeutic drug for other diseases including cancer when used in combination with other agents. However, cases of acitretin-associated liver injury have been documented, but the possible mechanisms of acitretin-associated hepatotoxicity and apoptosis are not entirely clarified. This study reports that mitochondrial dysfunctions may play an important role in liver injury and apoptosis induced by this retinoid. Acitretin (5-20 μM) impaired mitochondrial phosphorylation efficiency as demonstrated by the decrease in the state 3 respiration and ATP levels, and by the increase in the lag phase of ADP phosphorylation cycle, without affecting the membrane potential. Acitretin induced Ca(2+)-mediated mitochondrial permeability transition (MPT) and decreased the adenine nucleotide translocase (ANT) content. Acitretin-induced MPT was not prevented by thiol group protecting and antioxidant agents, excluding the involvement of oxidative stress mechanisms. However, MPT was prevented by ANT ligands ATP, ADP, tamoxifen and 4-hydroxytamoxifen, implying that the MPT induction by acitretin is mediated by the ANT. ANT plays a major role in promoting apoptosis and ATP synthesis, and it is still considered as a structural component of the pore with a regulatory role in MPT formation. Therefore, our results, including the decrease in the state 3 respiration and the increase in the lag phase of phosphorylation cycle, the ATP depletion and the induction of Ca(2+)-mediated MPT, indicate that acitretin-associated liver toxicity and apoptosis is possibly related with mitochondrial dysfunctions due to interactions with the ANT. Additionally, the combination of acitretin with other drugs, such as antiestrogens, which are able to inhibit the MPT, may contribute to decrease the toxicity induced by acitretin.

Differential gene expression in tamoxifen-resistant breast cancer cells revealed by a new analytical model of RNA-Seq data

Resistance to tamoxifen (Tam), a widely used antagonist of the estrogen receptor (ER), is a common obstacle to successful breast cancer treatment. While adjuvant therapy with Tam has been shown to significantly decrease the rate of disease recurrence and mortality, recurrent disease occurs in one third of patients treated with Tam within 5 years of therapy. A better understanding of gene expression alterations associated with Tam resistance will facilitate circumventing this problem. Using a next generation sequencing approach and a new bioinformatics model, we compared the transcriptomes of Tam-sensitive and Tam-resistant breast cancer cells for identification of genes involved in the development of Tam resistance. We identified differential expression of 1215 mRNA and 513 small RNA transcripts clustered into ERα functions, cell cycle regulation, transcription/translation, and mitochondrial dysfunction. The extent of alterations found at multiple levels of gene regulation highlights the ability of the Tam-resistant cells to modulate global gene expression. Alterations of small nucleolar RNA, oxidative phosphorylation, and proliferation processes in Tam-resistant cells present areas for diagnostic and therapeutic tool development for combating resistance to this anti-estrogen agent.

Interaction of tamoxifen and noise-induced damage to the cochlea

Tamoxifen has been used extensively in the treatment of breast cancer and other neoplasms. In addition to its well-known action on estrogen receptors it is also known to acutely block chloride channels that participate in cell volume regulation. Tamoxifen's role in preventing cochlear outer hair cell (OHC) swelling in vitro suggested that OHC swelling noted following noise exposure could potentially be a therapeutic target for tamoxifen in its role as a chloride channel blocker to help prevent noise-induced hearing loss. To investigate this possibility, the effects of exposure to tamoxifen on physiologic measures of cochlear function in the presence and absence of subsequent noise exposure were studied. Male Mongolian gerbils (2-4 months old) were randomly assigned to different groups. Tamoxifen at ∼10 mg/kg was administered to one of the groups. Five hours later they were exposed to a one-third octave band of noise centered at 8 kHz in a sound-isolation chamber for 30 min at 108 dB SPL. Compound action potential (CAP) thresholds and distortion product otoacoustic emission (DPOAE) levels were measured 30-35 days following noise exposure. Tamoxifen administration did not produce any changes in CAP thresholds and DPOAE levels when administered by itself in the absence of noise. Tamoxifen causes a significant increase in CAP thresholds from 8 to 15 kHz following noise exposure compared to CAP thresholds in animals exposed to noise alone. No significant differences were seen in the DPOAE levels in the f(2) = 8-15 kHz frequency range where maximum noise-induced increases in CAP thresholds were seen. Contrary to our original expectation, it is concluded that tamoxifen potentiates the degree of damage to the cochlea resulting from noise exposure.

The essential oils component p-cymene induces proton leak through Fo-ATP synthase and uncoupling of mitochondrial respiration

Essential oils can be used as antimicrobial, antioxidant, and anticarcinogenic agents or to preserve and give flavors to foods. The activity of phenolic-rich essential oils has been observed in fractions containing thymol and carvacrol which show synergistic effects with their precursor p-cymene. Their mode of action is related to several targets in the cell but specific mechanisms of activity and cytotoxic effects remain poorly characterized. Given the importance of mitochondria for cellular functions and their critical role in a vast number of diseases, this work evaluated the effects of p-cymene on mitochondrial functions. It was observed that p-cymene did not change the oxygen consumption by respiratory chain (state 2 respiration). However, p-cymene decreased the mitochondrial membrane potential (Δψ), depressed the rate of ADP phosphorylation (state 3), and stimulated the oxygen consumption after phosphorylation of ADP (state 4). The respiratory control ratio (state 3/state 4) was decreased as a consequence of the inhibition of state 3 and stimulation of state 4 respiration but the ADP/O index remained unaltered as well as the mitochondrial Ca²⁺ fluxes. Moreover, p-cymene did not induce mitochondrial membrane disruption but depressed the Δψ, and the stimulatory effect observed on state 4, similar to the effect observed on state 2 respiration plus ATP, was inhibited by oligomycin. These effects suggest that p-cymene allows a proton leak through the Fo fraction of the phosphorylative system, changing the mitochondrial proton motive force and ATP synthesis capacity. Therefore, these data suggest mitochondria as a target for p-cymene toxicity action mechanisms.

Influence of tamoxifen on gluconeogenesis and glycolysis in the perfused rat liver

The actions of tamoxifen, a selective estrogen receptor modulator used in chemotherapy and chemo-prevention of breast cancer, on glycolysis and gluconeogenesis were investigated in the isolated perfused rat liver. Tamoxifen inhibited gluconeogenesis from both lactate and fructose at very low concentrations (e.g., 5μM). The opposite, i.e., stimulation, was found for glycolysis from both endogenous glycogen and fructose. Oxygen uptake was unaffected, inhibited or stimulated, depending on the conditions. Stimulation occurred in both microsomes and mitochondria. Tamoxifen did not affect the most important key-enzymes of gluconeogenesis, namely, phosphoenolpyruvate carboxykinase, pyruvate carboxylase, fructose 1,6-bisphosphatase and glucose 6-phosphatase. Confirming previous observations, however, tamoxifen inhibited very strongly NADH- and succinate-oxidase of freeze-thawing disrupted mitochondria. Tamoxifen promoted the release of both lactate dehydrogenase (mainly cytosolic) and fumarase (mainly mitochondrial) into the perfusate. Tamoxifen (200μM) clearly diminished the ATP content and increased the ADP content of livers in the presence of lactate with a diminution of the ATP/ADP ratio from 1.67 to 0.79. The main causes for gluconeogenesis inhibition are probably: (a) inhibition of energy metabolism; (b) deviation of intermediates (malate and glucose 6-phosphate) for the production of NADPH required in hydroxylation and demethylation reactions; (c) deviation of glucosyl units toward glucuronidation reactions; (d) secondary inhibitory action of nitric oxide, whose production is stimulated by tamoxifen; (e) impairment of the cellular structure, especially the membrane structure. Stimulation of glycolysis is probably a compensatory phenomenon for the diminished mitochondrial ATP production. The multiple actions of tamoxifen at relatively low concentrations can represent a continuous burden to the overall hepatic functions during long treatment periods.

Immunohistochemical expression of mitochondrial membrane complexes (MMCs) I, III, IV and V in malignant and benign periampullary epithelium: a potential target for drug therapy of periampullary cancer?

Background

Mitochondrial membrane complexes (MMCs) are key mediators of cellular oxidative phosphorylation, and inhibiting them could lead to cell death. No published data are available on the relative abundance of MMCs in different periampullary cancers. Therefore, we studied the expression profile of MMCs I, III, IV and V in periampullary cancers, reactive pancreatitis, normal pancreas and chronic pancreatitis.

Methods

This was a retrospective study on tissue microarrays constructed from formalin-fixed paraffin-embedded tissue from 126 consecutive patients (cancer = 104, chronic pancreatitis = 22) undergoing pancreatic resections between June 2001 and June 2006. 78 specimens of chronic pancreatitis tissue were obtained adjacent to areas of cancer. Normal pancreatic tissue was obtained from the resection specimens in a total of 30 patients. Metastatic tumours in 61 regional lymph nodes from 61 patients were also studied.

Results

MMCs I, III, IV and V were highly expressed (p < 0.05) in all primary periampullary cancers compared with metastatic lymph nodes and adjacent benign pancreas. MMCs III, IV and V were highly expressed in all cancers regardless of type compared with chronic pancreatitis (p < 0.05). Higher expression of MMCs I and V was associated with better survival and may, in part, relate to lower expression of these MMCs in poorly differentiated tumours compared with well and moderately differentiated tumours.

Conclusions

Differential expression of MMCs III, IV and V in primary periampullary cancers compared with adjacent benign periampullary tissue and chronic pancreatitis is a novel finding, which may render them attractive anticancer targets.

Harnessing gene expression to identify the genetic basis of drug resistance

The advent of cost-effective genotyping and sequencing methods have recently made it possible to ask questions that address the genetic basis of phenotypic diversity and how natural variants interact with the environment. We developed Camelot (CAusal Modelling with Expression Linkage for cOmplex Traits), a statistical method that integrates genotype, gene expression and phenotype data to automatically build models that both predict complex quantitative phenotypes and identify genes that actively influence these traits. Camelot integrates genotype and gene expression data, both generated under a reference condition, to predict the response to entirely different conditions. We systematically applied our algorithm to data generated from a collection of yeast segregants, using genotype and gene expression data generated under drug-free conditions to predict the response to 94 drugs and experimentally confirmed 14 novel gene-drug interactions. Our approach is robust, applicable to other phenotypes and species, and has potential for applications in personalized medicine, for example, in predicting how an individual will respond to a previously unseen drug.

Regulation of mitochondrial respiratory chain biogenesis by estrogens/estrogen receptors and physiological, pathological and pharmacological implications

There has been increasing evidence pointing to the mitochondrial respiratory chain (MRC) as a novel and important target for the actions of 17beta-estradiol (E(2)) and estrogen receptors (ER) in a number of cell types and tissues that have high demands for mitochondrial energy metabolism. This novel E(2)-mediated mitochondrial pathway involves the cooperation of both nuclear and mitochondrial ERalpha and ERbeta and their co-activators on the coordinate regulation of both nuclear DNA- and mitochondrial DNA-encoded genes for MRC proteins. In this paper, we have: 1) comprehensively reviewed studies that reveal a novel role of estrogens and ERs in the regulation of MRC biogenesis; 2) discussed their physiological, pathological and pharmacological implications in the control of cell proliferation and apoptosis in relation to estrogen-mediated carcinogenesis, anti-cancer drug resistance in human breast cancer cells, neuroprotection for Alzheimer's disease and Parkinson's disease in brain, cardiovascular protection in human heart and their beneficial effects in lens physiology related to cataract in the eye; and 3) pointed out new research directions to address the key questions in this important and newly emerging area. We also suggest a novel conceptual approach that will contribute to innovative regimens for the prevention or treatment of a wide variety of medical complications based on E(2)/ER-mediated MRC biogenesis pathway.

Cisplatin impairs rat liver mitochondrial functions by inducing changes on membrane ion permeability: prevention by thiol group protecting agents

Cisplatin (CisPt) is the most important platinum anticancer drug widely used in the treatment of head, neck, ovarian and testicular cancers. However, the mechanisms by which CisPt induces cytotoxicity, namely hepatotoxicity, are not completely understood. The goal of this study was to investigate the influence of CisPt on rat liver mitochondrial functions (Ca(2+)-induced mitochondrial permeability transition (MPT), mitochondrial bioenergetics, and mitochondrial oxidative stress) to better understand the mechanism underlying its hepatotoxicity. The effect of thiol group protecting agents and some antioxidants against CisPt-induced mitochondrial damage was also investigated. Treatment of rat liver mitochondria with CisPt (20nmol/mg protein) induced Ca(2+)-dependent mitochondrial swelling, depolarization of membrane potential (DeltaPsi), Ca(2+) release, and NAD(P)H fluorescence intensity decay. These effects were prevented by cyclosporine A (CyA), a potent and specific inhibitor of the MPT. In the concentration range of up to 40nmol/mg protein, CisPt slightly inhibited state 3 and stimulated state 2 and state 4 respiration rates using succinate as respiratory substrate. The respiratory indexes, respiratory control ratio (RCR) and ADP/O ratios, the DeltaPsi, and the ADP phosphorylation rate were also depressed. CisPt induced mitochondrial inner membrane permeabilization to protons (proton leak) but did not induce significant changes on mitochondrial H(2)O(2) generation. All the effects induced by CisPt on rat liver mitochondria were prevented by thiol group protecting agents namely, glutathione (GSH), dithiothreitol (DTT), N-acetyl-L-cysteine (NAC) and cysteine (CYS), whereas superoxide-dismutase (SOD), catalase (CAT) and ascorbate (ASC) were without effect. In conclusion, the anticancer drug CisPt: (1) increases the sensitivity of mitochondria to Ca(2+)-induced MPT; (2) interferes with mitochondrial bioenergetics by increasing mitochondrial inner membrane permeabilization to H(+); (3) does not significantly affect H(2)O(2) generation by mitochondria; (4) its mitochondrial damaging effects are protected by thiol group protecting agents. Based on these conclusions, it is possible to hypothesise that small changes on the redox-status of thiol groups, affecting membrane permeability to cations (Ca(2+) and H(+)) underlie CisPt-induced liver mitochondrial damage, putatively responsible for its hepatotoxicity. Therefore, we propose that CisPt-induced mitochondrial damage and consequent hepatotoxicity could be prevented by using thiol group protecting agents as therapeutic adjuvants.

Cancer chemoprevention: a radical perspective

Cancer chemopreventive agents block the transformation of normal cells and/or suppress the promotion of premalignant cells to malignant cells. Certain agents may achieve these objectives by modulating xenobiotic biotransformation, protecting cellular elements from oxidative damage, or promoting a more differentiated phenotype in target cells. Conversely, various cancer chemopreventive agents can encourage apoptosis in premalignant and malignant cells in vivo and/or in vitro, which is conceivably another anticancer mechanism. Furthermore, it is evident that many of these apoptogenic agents function as prooxidants in vitro. The constitutive intracellular redox environment dictates a cell's response to an agent that alters this environment. Thus, it is highly probable that normal cells, through adaption, could acquire resistance to transformation via exposure to a chemopreventive agent that promotes oxidative stress or disrupts the normal redox tone of these cells. In contrast, transformed cells, which typically endure an oxidizing intracellular environment, would ultimately succumb to apoptosis due to an uncontrollable production of reactive oxygen species caused by the same agent. Here, we provide evidence to support the hypothesis that reactive oxygen species and cellular redox tone are exploitable targets in cancer chemoprevention via the stimulation of cytoprotection in normal cells and/or the induction of apoptosis in transformed cells.

Role of mitochondria in tamoxifen-induced rapid death of MCF-7 breast cancer cells

Tamoxifen (Tam) is widely used in chemotherapy of estrogen receptor-positive breast cancer. It inhibits proliferation and induces apoptosis of breast cancer cells by estrogen receptor-dependent modulation of gene expression, but recent reports have shown that Tam (especially at pharmacological concentrations) has also rapid nongenomic effects. Here we studied the mechanisms by which Tam exerts rapid effects on breast cancer cell viability. In serum-free medium 5-7 microM Tam induced death of MCF-7 and MDA-MB-231 cells in a time-dependent manner in less than 60 min. This was associated with release of mitochondrial cytochrome c, a decrease of mitochondrial membrane potential and an increase in production of reactive oxygen species (ROS). This suggests that disruption of mitochondrial function has a primary role in the acute death response of the cells. Accordingly, bongkrekic acid, an inhibitor of mitochondrial permeability transition, was able to protect MCF-7 cells against Tam. Rapid cell death induction by Tam was not associated with immediate activation of caspase-9 or cleavage of poly (ADP-ribose) polymerase. It was not blocked by the caspase inhibitor z-Val-Ala-Asp-fluoromethylketone either. Diphenylene ionodium (DPI), an inhibitor of NADPH oxidase, was able to prevent Tam-induced cell death but not cytochrome c release, which suggests that ROS act distal to cytochrome c. The pure antiestrogen ICI 182780 (1 microM) could partly oppose the effect of Tam in estrogen receptor positive MCF-7 cells, but not in estrogen receptor negative MDA-MB-231 cells. Pre-culturing MCF-7 cells in the absence of 17beta-estradiol (E(2)) or in the presence of a low Tam concentration (1 microM) made the cells even more susceptible to rapid death induction by 5 or 7 microM Tam. This effect was associated with decreased levels of the anti-apoptotic proteins Bcl-X(L) and Bcl-2. In conclusion, our results demonstrate induction of a rapid mitochondrial cell death program in breast cancer cells at pharmacological concentrations of Tam, which are achievable in tumor tissue of Tam-treated breast cancer patients. These mechanisms may contribute to the ability of Tam therapy to induce death of breast cancer cells.