A mechanopharmacology approach to overcome chemoresistance in pancreatic cancer.

Pancreatic ductal adenocarcinoma (PDAC) is a highly chemoresistant malignancy. This chemoresistant phenotype has been historically associated with genetic factors. Major biomedical research efforts were concentrated that resulted in the identification of subtypes characterized by specific genetic lesions and gene expression signatures that suggest important biological differences. However, to date, these distinct differences could not be exploited for therapeutic interventions. Apart from these genetic factors, desmoplasia and tumor microenvironment have been recognized as key contributors to PDAC chemoresistance. However, while several strategies targeting tumor-stroma have been explored including drugs against members of the Hedgehog family, they failed to meet the expectations in the clinical setting. These unsatisfactory clinical results suggest that, an important link between genetics and the influence of tumor microenvironment on PDAC chemoresistance remains to be elucidated. In this respect, mechanobiology is an emerging multidisciplinary field that encompasses cell and developmental biology as well as biophysics and bioengineering. Herein we provide a comprehensive overview of the key players in pancreatic cancer chemoresistance from the perspective of mechanobiology, and discuss novel experimental avenues such as elastic micropillar arrays that could provide fresh insights for the development of mechanobiology-targeted therapeutic approaches (know as mechanopharmacology) to overcome anticancer drug resistance in pancreatic cancer.

SIRT1-SIRT3 Axis Regulates Cellular Response to Oxidative Stress and Etoposide.

Sirtuins are conserved NAD+ -dependent deacylases. SIRT1 is a nuclear and cytoplasmic sirtuin involved in the control of histones a transcription factors function. SIRT3 is a mitochondrial protein, which regulates mitochondrial function. Although, both SIRT1 and SIRT3 have been implicated in resistance to cellular stress, the link between these two sirtuins has not been studied so far. Here we aimed to unravel: i) the role of SIRT1-SIRT3 axis for cellular response to oxidative stress and DNA damage; ii) how mammalian cells modulate such SIRT1-SIRT3 axis and which mechanisms are involved. Therefore, we analyzed the response to different stress stimuli in WT or SIRT1-silenced cell lines. Our results demonstrate that SIRT1-silenced cells are more resistant to H2 O2 and etoposide treatment showing decreased ROS accumulation, γ-H2AX phosphorylation, caspase-3 activation and PARP cleavage. Interestingly, we observed that SIRT1-silenced cells show an increased SIRT3 expression. To explore such a connection, we carried out luciferase assays on SIRT3 promoter demonstrating that SIRT1-silencing increases SIRT3 promoter activity and that such an effect depends on the presence of SP1 and ZF5 recognition sequences on SIRT3 promoter. Afterwards, we performed co-immunoprecipitation assays demonstrating that SIRT1 binds and deacetylates the transcription inhibitor ZF5 and that there is a decreased interaction between SP1 and ZF5 in SIRT1-silenced cells. Therefore, we speculate that acetylated ZF5 cannot bind and sequester SP1 that is free, then, to increase SIRT3 transcription. In conclusion, we demonstrate that cells with low SIRT1 levels can maintain their resistance and survival by increasing SIRT3 expression. J. Cell. Physiol. 232: 1835-1844, 2017. © 2016 Wiley Periodicals, Inc.

Synthetic small molecules as anti-biofilm agents in the struggle against antibiotic resistance.

Biofilm formation significantly contributes to microbial survival in hostile environments and it is currently considered a key virulence factor for pathogens responsible for serious chronic infections. In the last decade many efforts have been made to identify new agents able to modulate bacterial biofilm life cycle, and many compounds have shown interesting activities in inhibiting biofilm formation or in dispersing pre-formed biofilms. However, only a few of these compounds were tested using in vivo models for their clinical significance. Contrary to conventional antibiotics, most of the anti-biofilm compounds act as anti-virulence agents as they do not affect bacterial growth. In this review we selected the most relevant literature of the last decade, focusing on the development of synthetic small molecules able to prevent bacterial biofilm formation or to eradicate pre-existing biofilms of clinically relevant Gram-positive and Gram-negative pathogens. In addition, we provide a comprehensive list of the possible targets to counteract biofilm formation and development, as well as a detailed discussion the advantages and disadvantages of the different current biofilm-targeting strategies.

Role of c-MET Inhibitors in Overcoming Drug Resistance in Spheroid Models of Primary Human Pancreatic Cancer and Stellate Cells.

Pancreatic stellate cells (PSCs) are a key component of tumor microenvironment in pancreatic ductal adenocarcinoma (PDAC) and contribute to drug resistance. c-MET receptor tyrosine kinase activation plays an important role in tumorigenesis in different cancers including PDAC. In this study, effects of PSC conditioned medium (PCM) on c-MET phosphorylation (by immunocytochemistry enzyme-linked immunosorbent assay (ELISA)) and drug response (by sulforhodamine B assay) were investigated in five primary PDAC cells. In novel 3D-spheroid co-cultures of cyan fluorescence protein (CFP)-firefly luciferase (Fluc)-expressing primary human PDAC cells and green fluorescence protein (GFP)-expressing immortalized PSCs, PDAC cell growth and chemosensitivity were examined by luciferase assay, while spheroids' architecture was evaluated by confocal microscopy. The highest phospho-c-MET expression was detected in PDAC5 and its subclone sorted for "stage specific embryonic antigen-4" (PDAC5 (SSEA4)). PCM of cells pre-incubated with PDAC conditioned medium, containing increased hepatocyte growth factor (HGF) levels, made PDAC cells significantly more resistant to gemcitabine, but not to c-MET inhibitors. Hetero-spheroids containing both PSCs and PDAC5 (SSEA4) cells were more resistant to gemcitabine compared to PDAC5 (SSEA4) homo-spheroids. However, c-MET inhibitors (tivantinib, PHA-665752 and crizotinib) were equally effective in both spheroid models. Experiments with primary human PSCs confirmed the main findings. In conclusion, we developed spheroid models to evaluate PSC-PDAC reciprocal interaction, unraveling c-MET inhibition as an important therapeutic option against drug resistant PDAC.

The microbiome of pancreatic cancer: from molecular diagnostics to new therapeutic approaches to overcome chemoresistance caused by metabolic inactivation of gemcitabine.

Introduction: Pancreatic cancer is a complex disease, with an extremely poor response to chemotherapy. Emerging evidence indicates that the tumor microenvironment (TME) might play an important role in mediating chemoresistance. Areas covered: The evaluated study by Geller and collaborators describes several bacterial species within pancreatic tumor tissues and TME and investigated their roles in gemcitabine chemoresistance. Intratumor bacteria express the enzyme cytidine deaminase (CDD), whose long form (CDDL) was shown to metabolize gemcitabine into its inactive metabolite. CDDL is mostly expressed by Gammaproteobacteria and this was among the most common species in pancreatic cancer tissues. Interestingly, mouse models of colorectal cancer injected with bacterial CDDL displayed a reduced response to gemcitabine, but this resistance was neutralized by the antibiotic ciprofloxacin. Expert Commentary: The increased knowledge on the microbiome in pancreatic tissues, as well as its role in chemoresistance, will provide innovative prognostic and therapeutic strategies.

Pyrazole-based inhibitors of enhancer of zeste homologue 2 induce apoptosis and autophagy in cancer cells.

Novel pyrazole-based EZH2 inhibitors have been prepared through a molecular pruning approach from known inhibitors bearing a bicyclic moiety as a central scaffold. The hit compound 1o (N-((4,6-dimethyl-2-oxo-1,2-dihydropyridin-3-yl)methyl)-5-methyl-1-phenyl-1H-pyrazole-4-carboxamide) showed low micromolar EZH2/PRC2 inhibition and high selectivity towards a panel of other methyltransferases. Moreover, 1o displayed cell growth arrest in breast MDA-MB231, leukaemia K562, and neuroblastoma SK-N-BE cancer cells joined to reduction of H3K27me3 levels and induction of apoptosis and autophagy.This article is part of a discussion meeting issue 'Frontiers in epigenetic chemical biology'.

1,4-Dihydropyridines Active on the SIRT1/AMPK Pathway Ameliorate Skin Repair and Mitochondrial Function and Exhibit Inhibition of Proliferation in Cancer Cells.

Modulators of sirtuins are considered promising therapeutic targets for the treatment of cancer, cardiovascular, metabolic, inflammatory, and neurodegenerative diseases. Here we prepared new 1,4-dihydropyridines (DHPs) bearing changes at the C2/C6, C3/C5, C4, or N1 position. Tested with the SIRTainty procedure, some of them displayed increased SIRT1 activation with respect to the prototype 3a, high NO release in HaCat cells, and ameliorated skin repair in a mouse model of wound healing. In C2C12 myoblasts, two of them improved mitochondrial density and functions. All the effects were reverted by coadministration of compound C (9), an AMPK inhibitor, or of EX-527 (10), a SIRT1 inhibitor, highlighting the involvement of the SIRT1/AMPK pathway in the action of DHPs. Finally, tested in a panel of cancer cells, the water-soluble form of 3a, compound 8, displayed antiproliferative effects in the range of 8-35 µM and increased H4K16 deacetylation, suggesting a possible role for SIRT1 activators in cancer therapy.

One Special Question to Start with: Can HIF/NFkB be a Target in Inflammation?

Hypoxia and Inflammation are strictly interconnected with important consequences at clinical and therapeutic level. While cell and tissue damage due to acute hypoxia mostly leads to cell necrosis, in chronic hypoxia, cells that are located closer to vessels are able to survive adapting their phenotype through the expression of a number of genes, including proinflammatory receptors for alarmins. These receptors are activated by alarmins released by necrotic cells and generate signals for master transcription factors such as NFkB, AP1, etc. which control hundreds of genes for innate immunity and damage repair. Clinical consequences of chronic inflammatory reparative response activation include cell and tissue remodeling, damage in the primary site and, the systemic involvement of distant organs and tissues. Thus every time a tissue environment becomes stably hypoxic, inflammation can be activated followed by chronic damage and cell death or repair with vessel proliferation and fibrosis. This pathway can occur in cancer, myocardial infarction and stroke, diabetes, obesity, neurodegenerative diseases, chronic and autoimmune diseases and age-related diseases. Interestingly, proinflammatory gene expression can be observed earlier in hypoxic tissue cells and, in addition, in activated resident or recruited leukocytes. Herewith, the reciprocal relationships between hypoxia and inflammation will be shortly reviewed to underline the possible therapeutic targets to control hypoxia-related inflammation in a number of epidemiologically important human diseases and conditions.

SIRT5 regulation of ammonia-induced autophagy and mitophagy.

In liver the mitochondrial sirtuin, SIRT5, controls ammonia detoxification by regulating CPS1, the first enzyme of the urea cycle. However, while SIRT5 is ubiquitously expressed, urea cycle and CPS1 are only present in the liver and, to a minor extent, in the kidney. To address the possibility that SIRT5 is involved in ammonia production also in nonliver cells, clones of human breast cancer cell lines MDA-MB-231 and mouse myoblast C2C12, overexpressing or silenced for SIRT5 were produced. Our results show that ammonia production increased in SIRT5-silenced and decreased in SIRT5-overexpressing cells. We also obtained the same ammonia increase when using a new specific inhibitor of SIRT5 called MC3482. SIRT5 regulates ammonia production by controlling glutamine metabolism. In fact, in the mitochondria, glutamine is transformed in glutamate by the enzyme glutaminase, a reaction producing ammonia. We found that SIRT5 and glutaminase coimmunoprecipitated and that SIRT5 inhibition resulted in an increased succinylation of glutaminase. We next determined that autophagy and mitophagy were increased by ammonia by measuring autophagic proteolysis of long-lived proteins, increase of autophagy markers MAP1LC3B, GABARAP, and GABARAPL2, mitophagy markers BNIP3 and the PINK1-PARK2 system as well as mitochondrial morphology and dynamics. We observed that autophagy and mitophagy increased in SIRT5-silenced cells and in WT cells treated with MC3482 and decreased in SIRT5-overexpressing cells. Moreover, glutaminase inhibition or glutamine withdrawal completely prevented autophagy. In conclusion we propose that the role of SIRT5 in nonliver cells is to regulate ammonia production and ammonia-induced autophagy by regulating glutamine metabolism.

Sirtuins and resveratrol-derived compounds: a model for understanding the beneficial effects of the Mediterranean diet.

The beneficial effects of the Mediterranean diet (MD) had been first observed about 50 years ago. Consumption of fresh vegetables and fruits, cereals, red wine, nuts, legumes, etc. has been regarded as the primary factor for protection from many human pathologies by the Mediterranean diet. Subsequently, this was attributed to the presence of polyphenols and their derivatives that, by exerting an anti-inflammatory and anti-oxidative effect, can be involved in the prevention of many diseases. Clinical trials, observational studies and meta-analysis have demonstrated an antiageing effect of MD accompanied by a reduced risk of age-related pathologies, such as cardiovascular, metabolic and neurodegenerative diseases, as well as cancer. The scientific explanation of such beneficial effects was limited to the reduction of the oxidative stress by compounds present in the MD. However, recently, this view is changing thanks to new studies aimed to uncover the molecular mechanism(s) activated by components of this diet. In particular, a new class of proteins called sirtuins have gained the attention of the scientific community because of their antiageing effects, their ability to protect from cardiovascular, metabolic, neurodegenerative diseases, cancer and to extend lifespan in lower organisms as well as in mammals. Interestingly, resveratrol a polyphenol present in grapes, nuts and berries has been shown to activate sirtuins and such activation is able to explain most of the beneficial effects of the MD. In this review, we will highlight the importance of MD with particular attention to the possible molecular pathways that have been shown to be influenced by it. We will describe the state of the art leading to demonstrate the important role of sirtuins as principal intracellular mediators of the beneficial effects of the MD. Finally, we will also introduce how Mediterranean diet may influence microbioma composition and stem cells function.

Bridging hypoxia, inflammation and estrogen receptors in thyroid cancer progression.

Thyroid cancer is a common endocrine-related cancer with a higher incidence in women than in men. Thyroid tumors are classified on the basis of their histopathology as papillary, follicular, medullary, and undifferentiated or anaplastic. Epidemiological and in vitro or in vivo studies have suggested a correlation between incidence of thyroid malignancies and hormones. In particular, growing evidence indicates a role of estrogens and estrogen receptors (ERs) in thyroid tumorigenesis, reprogramming and progression. In this scenario, estrogens are hypothesized to contribute to the observed female predominance of thyroid cancer in reproductive years. However, the precise contribution of estrogens in thyroid proliferative disease initiation and progression is not well understood. HIF-1α and NF-κB are two transcription factors very frequently activated in tumors and involved in tumor growth, progression and resistance to chemotherapy. In fact, HIF-1α and NF-κB together regulate transcription of over a thousand genes that, in turn, control vital cellular processes such as adaptation to the hypoxia, metabolic and differentiation reprogramming, inflammatory-reparative response, extracellular matrix digestion, migration and invasion, adhesion, etc. Because of this wide involvement, they could control in an integrated manner the origin of the malignant phenotype. Interestingly, hypoxia and inflammation have been sequentially bridged in tumors by the discovery that alarmin receptors genes such as RAGE, P2X7 and some TLRs are activated by HIF-1α; and that, in turn, alarmin receptors strongly activate NF-κB and proinflammatory gene expression, evidencing all the hallmarks of the malignant phenotype. Recently, a large number of drugs have been identified that inhibit one or both transcription factors with promising results in terms of controlling tumor progression. In addition, many of these inhibitors are natural compounds or off-label drugs already used to cure other pathologies. Some of them are undergoing clinical trials and soon they will be used alone or in combination with standard anti-tumoral agents to achieve a better treatment of tumors to achieve a reduction of metastasis formation and, more importantly, a net increase in survival. This review highlights the central role of HIF-1α activated in hypoxic regions of the tumor, of NF-κB activation and proinflammatory gene expression in transformed thyroid cells to understand their progression toward malignancy. The role of ER-α will be underlined, considering also its role in reprogramming cancer cells.