Violacein induces death of resistant leukaemia cells via kinome reprogramming, endoplasmic reticulum stress and Golgi apparatus collapse

Pigments from pathogenic bacteria: a comprehensive update on recent advances

Bacterial pigments stand out as exceptional natural bioactive compounds with versatile functionalities. The pigments represent molecules from distinct chemical categories including terpenes, terpenoids, carotenoids, pyridine, pyrrole, indole, and phenazines, which are synthesized by diverse groups of bacteria. Their spectrum of physiological activities encompasses bioactive potentials that often confer fitness advantages to facilitate the survival of bacteria amid challenging environmental conditions. A large proportion of such pigments are produced by bacterial pathogens mostly as secondary metabolites. Their multifaceted properties augment potential applications in biomedical, food, pharmaceutical, textile, paint industries, bioremediation, and in biosensor development. Apart from possessing a less detrimental impact on health with environmentally beneficial attributes, tractable and scalable production strategies render bacterial pigments a sustainable option for novel biotechnological exploration for untapped discoveries. The review offers a comprehensive account of physiological role of pigments from bacterial pathogens, production strategies, and potential applications in various biomedical and biotechnological fields. Alongside, the prospect of combining bacterial pigment research with cutting-edge approaches like nanotechnology has been discussed to highlight future endeavours.

Molecular crosstalk between polyphenols and gut microbiota in cancer prevention

A growing body of evidence suggests that cancer remains a significant global health challenge, necessitating the development of novel therapeutic approaches. In recent years, the molecular crosstalk between polyphenols and gut microbiota has emerged as a promising pathway for cancer prevention. Polyphenols, abundant in many plant-based foods, possess diverse bioactive properties, including antioxidant, anti-inflammatory, and anticancer activities. The gut microbiota, a complex microbial community residing in the gastrointestinal tract, plays a crucial role in a host's health and disease risks. This review highlights cancer suppressive and oncogenic mechanisms of gut microbiota, the intricate interplay between gut microbiota modulation and polyphenol biotransformation, and the potential therapeutic implications of this interplay in cancer prevention. Furthermore, this review explores the molecular mechanisms underpinning the synergistic effects of polyphenols and the gut microbiota, such as modulation of signaling pathways and immune response and epigenetic modifications in animal and human studies. The current review also summarizes the challenges and future directions in this field, including the development of personalized approaches that consider interindividual variations in gut microbiota composition and function. Understanding the molecular crosstalk could offer new perspectives for the development of personalized cancer therapies targeting the polyphenol-gut axis. Future clinical trials are needed to validate the potential role of polyphenols and gut microbiota as innovative therapeutic strategies for cancer treatment.

Understanding the role of the gut microbiome in gastrointestinal cancer: A review

Gastrointestinal cancer represents one of the most diagnosed types of cancer. Cancer is a genetic and multifactorial disease, influenced by the host and environmental factors. It has been stated that 20% of cancer is caused by microorganisms such as Helicobacter pylori, hepatitis B and C virus, and human papillomavirus. In addition to these well-known microorganisms associated with cancer, it has been shown differences in the composition of the microbiota between healthy individuals and cancer patients. Some studies have suggested the existence of the selected microorganisms and their metabolites that can promote or inhibit tumorigenesis via some mechanisms. Recent findings have shown that gut microbiome and their metabolites can act as cancer promotors or inhibitors. It has been shown that gastrointestinal cancer can be caused by a dysregulation of the expression of non-coding RNA (ncRNA) through the gut microbiome. This review will summarize the latest reports regarding the relationship among gut microbiome, ncRNAs, and gastrointestinal cancer. The potential applications of diagnosing and cancer treatments will be discussed.

Violacein switches off low molecular weight tyrosine phosphatase and rewires mitochondria in colorectal cancer cells

In the last decade, emerging evidence has shown that low molecular weight protein tyrosine phosphatase (LMWPTP) not only contributes to the progression of cancer but is associated with prostate low survival rate and colorectal cancer metastasis. We report that LMWPTP favors the glycolytic profile in some tumors. Therefore, the focus of the present study was to identify metabolic enzymes that correlate with LMWPTP expression in patient samples. Exploratory data analysis from RNA-seq, proteomics, and histology staining, confirmed the higher expression of LMWPTP in CRC. Our descriptive statistical analyses indicate a positive expression correlation between LMWPTP and energy metabolism enzymes such as acetyl-CoA carboxylase (ACC) and fatty acid synthase (FASN). In addition, we examine the potential of violacein to reprogram energetic metabolism and LMWPTP activity. Violacein treatment induced a shift of glycolytic to oxidative metabolism associated with alteration in mitochondrial efficiency, as indicated by higher oxygen consumption rate. Particularly, violacein treated cells displayed higher proton leak and ATP-linked oxygen consumption rate (OCR) as an indicator of the OXPHOS preference. Notably, violacein is able to bind and inhibit LMWPTP. Since the LMWPTP acts as a hub of signaling pathways that offer tumor cells invasive advantages, such as survival and the ability to migrate, our findings highlight an unexplored potential of violacein in circumventing the metabolic plasticity of tumor cells.

Neuroprotective effects of violacein in a model of inherited amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by progressive death of motor neurons and muscle atrophy, with defective neuron-glia interplay and emergence of aberrant glial phenotypes having a role in disease pathology. Here, we have studied if the pigment violacein with several reported protective/antiproliferative properties may control highly neurotoxic astrocytes (AbAs) obtained from spinal cord cultures of symptomatic hSOD1G93A rats, and if it could be neuroprotective in this ALS experimental model. At concentrations lower than those reported as protective, violacein selectively killed aberrant astrocytes. Treatment of hSOD1G93A rats with doses equivalent to the concentrations that killed AbAs caused a marginally significant delay in survival, partially preserved the body weight and soleus muscle mass and improved the integrity of the neuromuscular junction. Reduced motor neuron death and glial reactivity was also found and likely related to decreased inflammation and matrix metalloproteinase-2 and -9. Thus, in spite that new experimental designs aimed at extending the lifespan of hSOD1G93A rats are needed, improvements observed upon violacein treatment suggest a significant therapeutic potential that deserves further studies.

Multi-target drug with potential applications: violacein in the spotlight

The aim of the current review is to address updated research on a natural pigment called violacein, with emphasis on its production, biological activity and applications. New information about violacein's action mechanisms as antitumor agent and about its synergistic action in drug delivery systems has brought new alternatives for anticancer therapy. Thus, violacein is introduced as reliable drug capable of overcoming at least three cancer hallmarks, namely: proliferative signaling, cell death resistance and metastasis. In addition, antimicrobial effects on several microorganisms affecting humans and other animals turn violacein into an attractive drug to combat resistant pathogens. Emphasis is given to effects of violacein combined with different agents, such as antibiotics, anticancer agents and nanoparticles. Although violacein is well-known for many decades, it remains an attractive compound. Thus, research groups have been making continuous effort to help improving its production in recent years, which can surely enable its pharmaceutical and chemical application as multi-task compound, even in the cosmetics and food industries.

HOXA13 in etiology and oncogenic potential of Barrett's esophagus

Barrett's esophagus in gastrointestinal reflux patients constitutes a columnar epithelium with distal characteristics, prone to progress to esophageal adenocarcinoma. HOX genes are known mediators of position-dependent morphology. Here we show HOX collinearity in the adult gut while Barrett's esophagus shows high HOXA13 expression in stem cells and their progeny. HOXA13 overexpression appears sufficient to explain both the phenotype (through downregulation of the epidermal differentiation complex) and the oncogenic potential of Barrett's esophagus. Intriguingly, employing a mouse model that contains a reporter coupled to the HOXA13 promotor we identify single HOXA13-positive cells distally from the physiological esophagus, which is mirrored in human physiology, but increased in Barrett's esophagus. Additionally, we observe that HOXA13 expression confers a competitive advantage to cells. We thus propose that Barrett's esophagus and associated esophageal adenocarcinoma is the consequence of expansion of this gastro-esophageal HOXA13-expressing compartment following epithelial injury.

Microbial synthesis of violacein pigment and its potential applications

Violacein is a pigment synthesized by Gram-negative bacteria such as Chromobacterium violaceum. It has garnered significant interest owing to its unique physiological and biological activities along with its synergistic effects with various antibiotics. In addition to C. violaceum, several microorganisms, including: Duganella sp., Pseudoalteromonas sp., Iodobacter sp., and Massilia sp., are known to produce violacein. Along with the identification of violacein-producing strains, the genetic regulation, quorum sensing mechanism, and sequence of the vio-operon involved in the biosynthesis of violacein have been elucidated. From an engineering perspective, the heterologous production of violacein using the genetically engineered Escherichia coli or Citrobacter freundii host has also been attempted. Genetic engineering of host cells involves the heterologous expression of genes involved in the vio operon and the optimization of metabolic pathways and gene regulation. Further, the crystallography of VioD and VioE was revealed, and mass production by enzyme engineering has been accelerated. In this review, we highlight the biologically assisted end-use applications of violacein (such as functional fabric development, nanoparticles, functional polymer composites, and sunscreen ingredients) and violacein activation mechanisms, production strains, and the results of mass production with engineered methods. The prospects for violacein research and engineering applications have also been discussed.

Biotechnological Activities and Applications of Bacterial Pigments Violacein and Prodigiosin

In this review, we discuss violacein and prodigiosin, two chromogenic bacterial secondary metabolites that have diverse biological activities. Although both compounds were "discovered" more than seven decades ago, interest into their biological applications has grown in the last two decades, particularly driven by their antimicrobial and anticancer properties. These topics will be discussed in the first half of this review. The latter half delves into the current efforts of groups to produce these two compounds. This includes in both their native bacterial hosts and heterogeneously in other bacterial hosts, including discussing some of the caveats related to the yields reported in the literature, and some of the synthetic biology techniques employed in this pursuit.

Violacein improves recombinant IgG production by controlling the cell cycle of Chinese hamster ovary cells

Chinese hamster ovary (CHO) cells are used as host cells for industrial monoclonal antibody (mAb) production. Cell cycle control is an effective approach to increase mAb production in the cell culture. Violacein, a purple-colored pigment produced by microorganisms, has diverse bioactive properties and has been proposed for various industrial applications. In this study, we evaluated the potency of violacein for cell cycle control and improvement of recombinant immunoglobulin G (IgG) production in CHO cells. Compared with the control, 0.9 μM violacein in a 14-day fed-batch culture increased the maximum IgG concentration by 37.6% via increasing the specific production rate and cell longevity. Cell cycle analysis showed that violacein induced G1 and G2/M phase arrest. However, the G1 arrest was observed only on day 1, while G2/M arrest lasted more than 3 days, suggesting that G2/M arrest mediated the violacein-induced enhanced IgG production. Moreover, in line with the increased protein expression, the expression levels of IgG mRNA and nutrient metabolic rates were also increased. N-Linked glycosylation and charge variant profiles were barely affected by violacein treatment. Our results indicate that violacein affects the cell cycle of CHO cells and increases IgG production without changing product quality, showing promise as a mAb production enhancer in CHO cells. The study provides insight into violacein utilization in industrial mAb manufacturing and can help develop advanced, effective mAb production technologies using CHO cell cultures.

HOXA9 mediates and marks premalignant compartment size expansion in colonic adenomas

The transformation of normal colonic epithelium to colorectal cancer (CRC) involves a relatively ordered progression, and understanding the molecular alterations involved may aid rational design of strategies aimed at preventing or counteracting disease. Homeobox A9 (HOXA9) is an oncogene in leukemia and has been implicated in CRC pathology, although its role in disease etiology remains obscure at best. We observe that HOXA9 expression is increased in colonic adenomas compared with location-matched healthy colon epithelium. Its forced expression results in dramatic genetic and signaling changes, with increased expression of growth factors IGF1 and FLT3, super-activity of the AKT survival pathway and a concomitant increase in compartment size. Furthermore, a reduced mRNA expression of the epithelial to mesenchymal transition marker N-cadherin as well as reduced activity of the actin cytoskeletal mediator PAK was seen, which is in apparent agreement with an observed reduced migratory response in HOXA9-overexpressing cells. Thus, HOXA9 appears closely linked with adenoma growth while impairing migration and metastasis and hence is both a marker and driver of premalignant polyp growth. Colonic polyps grow but remain premalignant for up to decades. Here, we show that HOXA9 drives growth in premalignant polyps, but simultaneously prevents further transformation.

Forced expression of HOXA13 confers oncogenic hallmarks to esophageal keratinocytes

HOXA13 overexpression has been detected in human ESCC tissue and high HOXA13 protein expression is correlated with a shorter median survival time in ESCC patients. Although aberrant expression of HOXA13 in ESCC has thus been established, little is known regarding the functional consequences thereof. The present study aimed to examine to what extent aberrant HOXA13 might drive carcinogenesis in esophageal keratinocytes. To this end, we overexpressed HOXA13 in a non-transformed human esophageal cell line EPC2-hTERT, performed gene expression profiling to identify key processes and functions, and performed functional experiments. We found that HOXA13 expression confers oncogenic hallmarks to esophageal keratinocytes. It provides proliferation advantage to keratinocytes, reduces sensitivity to chemical agents, regulates MHC class I expression and differentiation status and promotes cellular migration. Our data indicate a crucial role of HOXA13 at early stages of esophageal carcinogenesis.

LMWPTP modulates the antioxidant response and autophagy process in human chronic myeloid leukemia cells

In the last decade, several reports highlight the importance of the low molecular weight protein tyrosine phosphatase (LMWPTP) in cancer aggressiveness and resistance. Specifically, in chronic myeloid leukemia, we have reported that high expression of the LMWPTP maintains Src and Bcr-Abl kinases in an activated status and the glucose metabolism is directed to lactate production and, in turn, favor the pentoses pathway (one of the key process for antioxidant and protective responses). In this present study, we investigated the possible correlation between the LMWPTP and autophagy. In resistant chronic myeloid leukemia cells, the antioxidant response is supported by the glycolytic metabolism and antioxidant enzymes such as SOD and catalase, both favored by the LMWPTP. Therefore, when the cells were challenged by hydrogen peroxide treatment, the LMWPTP level goes down as well as SOD, and in turn, autophagy process was stimulated. The findings presented here reveal a novel aspect by which LMWPTP cooperates for the resistance of CML towards stressor stimuli.

Assessment of in vitro cytotoxicity of imidazole ionic liquids and inclusion in targeted drug carriers containing violacein

Violacein (Viol) is a pigment produced by several Gram-negative bacteria with many bioactivities, such as anticancer, virucide, and antiparasitic. However, violacein is insoluble under physiological conditions preventing its potential therapeutic uses. Surface-active ionic liquids (SAILs) based on the cation 1-alkylimidazolium ([C_nHim]) with n = 10 to 16 alkyl carbon side chain lengths and acetate, bromide, methanesulfonate (S) or trifluoroacetate (F) as counterions were synthesized and screened to dissolve Viol in micellar aqueous media and for toxicological studies on the human lung carcinoma A549 cell line. Screening allowed the selection of 1.5 × 10⁻³% (w/v) [C₁₆Him]-S because it combines low cytotoxicity with 71.5% cell viability and good interaction with 95.2% of the violacein kept in micellar solution for at least 48 h. [Viol-([C₁₆Him]-S)] complex was used to develop an efficient hybrid solid lipid nanoparticle (SLN) carrier based on myristyl myristate and poloxamer 188 and tailored with folate to target cancer cells. Cellular SLN uptake was evaluated with fluorescent DiOC₁₈ on A549, HCT-116, and HeLa cell lines expressing or not the folate receptor. The results showed fivefold incorporation of Viol nanoparticles in HCT-116 and HeLa cell cultures, displaying a high level of folate receptor. Biophysical characterization of the hybrid solid lipid carrier containing Viol was performed by dynamic light scattering, Fourier transform infrared, X-ray diffraction and X-ray photoelectron spectroscopies, and by transmission electron and cryo-transmission microscopies.

Violacein (Viol) is a pigment produced by several Gram-negative bacteria with many bioactivities, such as anticancer, virucide, and antiparasitic.

The Bacterial Product Violacein Exerts an Immunostimulatory Effect Via TLR8

Violacein, an indole-derived, purple-colored natural pigment isolated from Chromobacterium violaceum has shown multiple biological activities. In this work, we studied the effect of violacein in different immune cell lines, namely THP-1, MonoMac 6, ANA-1, Raw 264.7 cells, as well as in human peripheral blood mononuclear cells (PBMCs). A stimulation of TNF-α production was observed in murine macrophages (ANA-1 and Raw 264.7), and in PBMCs, IL-6 and IL-1β secretion was detected. We obtained evidence of the molecular mechanism of activation by determining the mRNA expression pattern upon treatment with violacein in Raw 264.7 cells. Incubation with violacein caused activation of pathways related with an immune and inflammatory response. Our data utilizing TLR-transfected HEK-293 cells indicate that violacein activates the human TLR8 (hTLR8) receptor signaling pathway and not human TLR7 (hTLR7). Furthermore, we found that the immunostimulatory effect of violacein in PBMCs could be suppressed by the specific hTLR8 antagonist, CU-CPT9a. Finally, we studied the interaction of hTLR8 with violacein in silico and obtained evidence that violacein could bind to hTLR8 in a similar fashion to imidazoquinoline compounds. Therefore, our results indicate that violacein may have some potential in contributing to future immune therapy strategies.

Human mesenchymal stromal cells in adhesion to cell-derived extracellular matrix and titanium: Comparative kinome profile analysis

The extracellular matrix (ECM) physically supports cells and influences stem cell behaviour, modulating kinase-mediated signalling cascades. Cell-derived ECMs have emerged in bone regeneration as they reproduce physiological tissue-architecture and ameliorate mesenchymal stromal cell (MSC) properties. Titanium scaffolds show good mechanical properties, facilitate cell adhesion, and have been routinely used for bone tissue engineering (BTE). We analyzed the kinomic signature of human MSCs in adhesion to an osteopromotive osteoblast-derived ECM, and compared it to MSCs on titanium. PamChip kinase-array analysis revealed 63 phosphorylated peptides on ECM and 59 on titanium, with MSCs on ECM exhibiting significantly higher kinase activity than on titanium. MSCs on the two substrates showed overlapping kinome profiles, with activation of similar signalling pathways (FAK, ERK, and PI3K signalling). Inhibition of PI3K signalling in cells significantly reduced adhesion to ECM and increased the number of nonadherent cells on both substrates. In summary, this study comprehensively characterized the kinase activity in MSCs on cell-derived ECM and titanium, highlighting the role of PI3K signalling in kinomic changes regulating osteoblast viability and adhesion. Kinome profile analysis represents a powerful tool to select pathways to better understand cell behaviour. Osteoblast-derived ECM could be further investigated as titanium scaffold-coating to improve BTE.

Integrated constraints based analysis of an engineered violacein pathway in Escherichia coli

Strategies towards optimal violacein biosynthesis, a potential drug molecule, need systems level coordination of enzymatic activities of individual genes in a multigene operon vioABCDE. Constraints-based flux balance analysis of an extended iAF1260 model (iAF1260vio) with a reconstructed violacein module predicted growth and violacein yields in Escherichia coli accurately. Shadow price (SP) analysis identified tryptophan metabolism and NADPH as limiting. Increased tryptophan levels in Δpgi & ΔpheA were validated using in silico gene deletion analysis. Phenotypic phase plane (PhPP) analysis highlighted sensitivity between tryptophan and NADPH for violacein synthesis at molar growth yields. A synthetic VioABCDE operon (SYNO) sequence was designed to maximize Codon Adaptive Index (CAI: 0.9) and tune translation initiation rates (TIR: 2-50 fold higher) in E. coli. All pSYN E. coli transformants produced higher violacein, with a maximum six-fold increase in yields. The rational design E. coli: ΔpheA SYN: gave the highest violacein titers (33.8 mg/l). Such integrated approaches targeting multiple molecular hierarchies in the cell can be extended further to increase violacein yields.

Low dose Naltrexone for induction of remission in inflammatory bowel disease patients

BACKGROUND

Around 30% of patients with inflammatory bowel disease (IBD) are refractory to current IBD drugs or relapse over time. Novel treatments are called for, and low dose Naltrexone (LDN) may provide a safe, easily accessible alternative treatment option for these patients. We investigated the potential of LDN to induce clinical response in therapy refractory IBD patients, and investigated its direct effects on epithelial barrier function.

METHODS

Patients not in remission and not responding to conventional therapy were offered to initiate LDN as a concomitant treatment. In total 47 IBD patients prescribed LDN were followed prospectively for 12 weeks. Where available, endoscopic remission data, serum and biopsies were collected. Further the effect of Naltrexone on wound healing (scratch assay), cytokine production and endoplasmic reticulum (ER) stress (GRP78 and CHOP western blot analysis, immunohistochemistry) were investigated in HCT116 and CACO2 intestinal epithelial cells, human IBD intestinal organoids and patient samples.

RESULTS

Low dose Naltrexone induced clinical improvement in 74.5%, and remission in 25.5% of patients. Naltrexone improved wound healing and reduced ER stress induced by Tunicamycin, lipopolysaccharide or bacteria in epithelial barriers. Inflamed mucosa from IBD patients showed high ER stress levels, which was reduced in patients treated with LDN. Cytokine levels in neither epithelial cells nor serum from IBD patients were affected.

CONCLUSIONS

Naltrexone directly improves epithelial barrier function by improving wound healing and reducing mucosal ER stress levels. Low dose Naltrexone treatment is effective and safe, and could be considered for the treatment of therapy refractory IBD patients.

Antibacterial mode of action of violacein from Chromobacterium violaceum UTM5 against Staphylococcus aureus and methicillin-resistant Staphylococcus aureus (MRSA)

Violacein, violet pigment produced by Chromobacterium violaceum, has attracted much attention recently due to its pharmacological properties including antibacterial activity. The present study investigated possible antibacterial mode of action of violacein from C. violaceum UTM5 against Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) strains. Violet fraction was obtained by cultivating C. violaceum UTM5 in liquid pineapple waste medium, extracted, and fractionated using ethyl acetate and vacuum liquid chromatography technique. Violacein was quantified as major compound in violet fraction using HPLC analysis. Violet fraction displayed bacteriostatic activity against S. aureus ATCC 29213 and methicillin-resistant S. aureus ATCC 43300 with minimum inhibitory concentration (MIC) of 3.9 μg/mL. Fluorescence dyes for membrane damage and scanning electron microscopic analysis confirmed the inhibitory effect by disruption on membrane integrity, morphological alternations, and rupture of the cell membranes of both strains. Transmission electron microscopic analysis showed membrane damage, mesosome formation, and leakage of intracellular constituents of both bacterial strains. Mode of action of violet fraction on the cell membrane integrity of both strains was shown by release of protein, K⁺, and extracellular adenosine 5'-triphosphate (ATP) with 110.5 μg/mL, 2.34 μg/mL, and 87.24 ng/μL, respectively, at 48 h of incubation. Violet fraction was toxic to human embryonic kidney (HEK293) and human fetal lung fibroblast (IMR90) cell lines with LC₅₀ value of 0.998 ± 0.058 and 0.387 ± 0.002 μg/mL, respectively. Thus, violet fraction showed a strong antibacterial property by disrupting the membrane integrity of S. aureus and MRSA strains. This is the first report on the possible mode of antibacterial action of violet fraction from C. violaceum UTM5 on S. aureus and MRSA strains.

The gastrointestinal microbiota and its role in oncogenesis

Advances in research techniques have made it possible to map the microbial communities in the gastrointestinal (GI) tract, where the majority of bacteria in the human body reside. Disturbances in these communities are referred to as dysbiosis and have been associated with GI cancers. Although dysbiosis is observed in several GI malignancies, the specific role of these changes has not been understood to the extent of Helicobacter pylori (HP) in gastric cancer (GC). This review will address the bacterial communities along the GI tract, from the oral cavity to the anal canal, particularly focusing on bacterial dysbiosis and carcinogenesis. Just as non-HP bacteria in the stomach may interact with HP in gastric carcinogenesis, the same may hold true for other GI tract malignancies, where an interplay between microbes in carcinogenesis seems conceivable, especially in colorectal cancer (CRC). In the last part of this review we will discuss the potential mechanisms of bacterial dysbiosis in GI carcinogenesis.

Action and function of Chromobacterium violaceum in health and disease: Violacein as a promising metabolite to counteract gastroenterological diseases

Chromobacterium violaceum is a Gram negative, β-proteobacterium found in the microbiota of tropical and subtropical environments. Although considered an opportunistic pathogen, infection rapidly progress to fatal sepsis, with metastatic abscesses. It is noteworthy the multidrug resistant phenotype of C. violaceum and the possibility of relapse. Recently, an influence of global climate in the incidence of cases beyond the previous areas has been observed. Furthermore, chronic granulomatous disease has been considered a risk factor to infection. Despite the increase in C. violaceum infection incidence and high mortality, most clinicians are not familiar with it. This review pointed out important features of this life threatening microorganism, including its pathogenicity, mechanistic aspects, genetic and drug resistance associated factors, and the clinical association with chronic granulomatous disease. In addition, its main metabolite violacein may be a promising agent to counteract gastroenterological diseases, such as colorectal cancer and inflammatory gastric lesions.

Genetic host factors in Helicobacter pylori-induced carcinogenesis: Emerging new paradigms

Helicobacter Pylori is a gram negative rod shaped microaerophilic bacterium that colonizes the stomach of approximately half the world's population. Infection with c may cause chronic gastritis which via a quite well described process known as Correas cascade can progress through sequential development of atrophic gastritis, intestinal metaplasia and dysplasia to gastric cancer. H. pylori is currently the only bacterium that is classified as a class 1 carcinogen by the WHO, although the exact mechanisms by which this bacterium contributes to gastric carcinogenesis are still poorly understood. Only a minority of H. pylori-infected patients will eventually develop gastric cancer, suggesting that host factors may be important in determining the outcome of H. pylori infection. This is supported by a growing body of evidence suggesting that the host genetic background contributes to risk of H. pylori infection and gastric carcinogenesis. In particular single nucleotide polymorphisms in genes that influence bacterial handling via pattern recognition receptors appear to be involved, further strengthening the link between host risk factors, H. pylori incidence and cancer. Many of these genes influence cellular pathways leading to inflammatory signaling, inflammasome formation and autophagy. In this review we summarize known carcinogenic effects of H. pylori, and discuss recent findings that implicate host genetic pattern recognition pathways in the development of gastric cancer and their relation with H. pylori.

Violacein induces death of RAS-mutated metastatic melanoma by impairing autophagy process

Treatment of metastatic melanoma still remains a challenge, since in advanced stage it is refractory to conventional treatments. Most patients with melanoma have either B-RAF or N-RAS mutations, and these oncogenes lead to activation of the RAS-RAF-MEK-ERK and AKT signal pathway, keeping active the proliferation and survival pathways in the cell. Therefore, the identification of small molecules that block metastatic cell proliferation and induce cell death is needed. Violacein, a pigment produced by Chromobacterium violaceum found in Amazon River, has been used by our group as a biotool for scrutinizing signaling pathways associated with proliferation, survival, aggressiveness, and resistance of cancer cells. In the present study, we demonstrate that violacein diminished the viability of RAS- and RAF-mutated melanoma cells (IC₅₀ value ∼500 nM), and more important, this effect was not abolished after treatment medium removal. Furthermore, violacein was able to reduce significantly the invasion capacity of metastatic melanoma cells in 3D culture. In the molecular context, we have shown for the first time that violacein causes a strong drop on histone deacetylase 6 expression, a proliferating activator, in melanoma cells. Besides, an inhibition of AXL and AKT was detected. All these molecular events propitiate an inhibition of autophagy, and consequently, melanoma cell death by apoptosis.

Advances in Chromobacterium violaceum and properties of violacein-Its main secondary metabolite: A review

Chromobacterium violaceum is important in the production of violacein, like other bacteria, such as Alteromonas, Janthinobacterium, Pseudoalteromonas, Duganella, Collimonas and Escherichia. Violacein is a versatile pigment, where it exhibits several biological activities, and every year, it shows increasing commercially interesting uses, especially for industrial applications in cosmetics, medicines and fabrics. This review on violacein focuses mainly on the last five years of research regarding this target compound and describes production and importance of quorum sensing in C. violaceum, mechanistic aspects of its biosynthesis, monitoring processes, genetic perspectives, pathogenic effects, antiparasitic and antimicrobial activities, immunomodulatory potential and uses, antitumor potential and industrial applications.

Violacein induces apoptosis in human breast cancer cells through up regulation of BAX, p53 and down regulation of MDM2

We aimed to explore the anticancer potential of violacein and its time, dose dependent mechanism of action in human MCF-7 breast cancer cells. We observed, violacein inhibit MCF-7 cells viability in a time and dose-dependent manner, IC50 value was 4.5 μM in 24 h, 1.7 μM in 48 h and 0.51 μM in 72 h. Violacein triggered generation of intra cellular ROS even from the lower doses, significant ROS production was observed from 0.25, 0.45 μM dose range and it is relative to higher doses. Further we fixed 0.45 μM and 4.5 μM as an experimental dose for relative dose dependent analysis. In nuclear staining, after 48 h 0.45 μM dose showed characteristic apoptotic morphological changes such as, 59% of cells in apoptosis and 11% of cells in necrotic stage, also in 72 h we found 68% in apoptosis and 12% in necrotic stage. However, 4.5 μM (IC50) dose of violacein, 78% of cells became apoptotic and 21% in necrotic after 48 h; but in 72 h only 61% cells are in apoptotic, necrosis was increased to 38%. Violacein increased both mitochondrial and extra mitochondrial apoptotic pathway related gene expressions; it was confirmed by increased CYP1A, GPX, GSK3β and TNF-α gene. Further, 0.45 and 4.5 μM of violacein increased apoptotic genes, such as Bax, p53, caspase 3, Fas, FADD and markedly reduced Bcl-2 and MDM2 expression levels to two fold when compared to control. In addition violacein upregulated poly ADP-ribose polymerase (PARP), CDKN1A and caspase-9 significantly (p≤0.05) when compared to control. Relative quantification of caspase-8 was differently expressed; there were no changes in 0.45 μM, but in 4.5 μM we found two fold increased caspase-8 expression. In conclusion, lower dose of violacein treatment induced apoptosis in human breast cancer MCF-7 cells through TNF-α and p53 dependent mitochondrial pathways.

Violacein, an indole-derived purple-colored natural pigment produced by Janthinobacterium lividum, inhibits the growth of head and neck carcinoma cell lines both in vitro and in vivo

Violacein (VIO; 3-[1,2-dihydro-5-(5-hydroxy-1H-indol-3-yl)-2-oxo-3H-pyrrol-3-ylidene]-1,3-dihydro-2H-indol-2-one), an indole-derived purple-colored pigment, produced by a limited number of Gram-negative bacteria species, including Chromobacterium violaceum and Janthinobacterium lividum, has been demonstrated to have anti-cancer activity, as it interferes with survival transduction signaling pathways in different cancer models. Head and neck carcinoma (HNC) represents the sixth most common and one of the most fatal cancers worldwide. We determined whether VIO was able to inhibit head and neck cancer cell growth both in vitro and in vivo. We provide evidence that VIO treatment of human and mouse head and neck cancer cell lines inhibits cell growth and induces autophagy and apoptosis. In fact, VIO treatment increased PARP-1 cleavage, the Bax/Bcl-2 ratio, the inhibition of ERK1 and ERK2 phosphorylation, and the expression of light chain 3-II (LC3-II). Moreover, VIO was able to induce p53 degradation, cytoplasmic nuclear factor kappa B (NF-κB) accumulation, and reactive oxygen species (ROS) production. VIO induced a significant increase in ROS production. VIO administration was safe in BALB/c mice and reduced the growth of transplanted salivary gland cancer cells (SALTO) in vivo and prolonged median survival. Taken together, our results indicate that the treatment of head and neck cancer cells with VIO can be useful in inhibiting in vivo and in vitro cancer cell growth. VIO may represent a suitable tool for the local treatment of HNC in combination with standard therapies.

PAK2 is an effector of TSC1/2 signaling independent of mTOR and a potential therapeutic target for Tuberous Sclerosis Complex

Tuberous sclerosis complex (TSC) is caused by inactivating mutations in either TSC1 or TSC2 and is characterized by uncontrolled mTORC1 activation. Drugs that reduce mTOR activity are only partially successful in the treatment of TSC, suggesting that mTOR-independent pathways play a role in disease development. Here, kinome profiles of wild-type and Tsc2^−/− mouse embryonic fibroblasts (MEFs) were generated, revealing a prominent role for PAK2 in signal transduction downstream of TSC1/2. Further investigation showed that the effect of the TSC1/2 complex on PAK2 is mediated through RHEB, but is independent of mTOR and p21RAC. We also demonstrated that PAK2 over-activation is likely responsible for the migratory and cell cycle abnormalities observed in Tsc2^−/− MEFs. Finally, we detected high levels of PAK2 activation in giant cells in the brains of TSC patients. These results show that PAK2 is a direct effector of TSC1-TSC2-RHEB signaling and a new target for rational drug therapy in TSC.

Violacein: Properties and Production of a Versatile Bacterial Pigment

Violacein-producing bacteria, with their striking purple hues, have undoubtedly piqued the curiosity of scientists since their first discovery. The bisindole violacein is formed by the condensation of two tryptophan molecules through the action of five proteins. The genes required for its production, vioABCDE, and the regulatory mechanisms employed have been studied within a small number of violacein-producing strains. As a compound, violacein is known to have diverse biological activities, including being an anticancer agent and being an antibiotic against Staphylococcus aureus and other Gram-positive pathogens. Identifying the biological roles of this pigmented molecule is of particular interest, and understanding violacein's function and mechanism of action has relevance to those unmasking any of its commercial or therapeutic benefits. Unfortunately, the production of violacein and its related derivatives is not easy and so various groups are also seeking to improve the fermentative yields of violacein through genetic engineering and synthetic biology. This review discusses the recent trends in the research and production of violacein by both natural and genetically modified bacterial strains.

Violacein induces cell death by triggering mitochondrial membrane hyperpolarization in vitro

Background

Violacein is a purple pigment from Chromobacterium violaceum that possesses diverse biological and pharmacological properties. Among these, pro-oxidant and antioxidant activities have been suggested. However, the cytotoxic mechanisms induced by violacein are poorly understood and the improvement in knowledge regarding these cell death mechanisms will be useful to develop new therapeutic approaches. Considering this, in our work, we investigated the pro-oxidant effects of violacein in non-tumor (CHO-K1 and MRC-5) and tumor (HeLa) cell lines, searching for a better understanding of reactive oxygen species (ROS) production and cell death induction.

Results

Cytotoxicity induced by violacein was observed in the three cell lines; however, MRC-5 and HeLa cells were shown to be more sensitive to violacein treatment. Although punctual alterations in the antioxidant apparatus and increase in oxidative stress biomarkers was observed in some violacein concentrations, no association was found between increased oxidative stress and induction of cell death. However, the increase of mitochondrial membrane potential was observed.

Conclusions

In fact, the increase of mitochondrial membrane potential in MRC-5 and HeLa cells suggests that mitochondrial membrane hyperpolarization might be the main cause of cell death triggered by violacein.

Violacein Treatment Modulates Acute and Chronic Inflammation through the Suppression of Cytokine Production and Induction of Regulatory T Cells

Inflammation is a necessary process to control infection. However, exacerbated inflammation, acute or chronic, promotes deleterious effects in the organism. Violacein (viola), a quorum sensing metabolite from the Gram-negative bacterium Chromobacterium violaceum, has been shown to protect mice from malaria and to have beneficial effects on tumors. However, it is not known whether this drug possesses anti-inflammatory activity. In this study, we investigated whether viola administration is able to reduce acute and chronic autoimmune inflammation. For that purpose, C57BL/6 mice were intraperitoneally injected with 1 μg of LPS and were treated with viola (3.5mg/kg) via i.p. at the same time-point. Three hours later, the levels of inflammatory cytokines in the sera and phenotypical characterization of leukocytes were determined. Mice treated with viola presented a significant reduction in the production of inflammatory cytokines compared with untreated mice. Interestingly, although viola is a compound derived from bacteria, it did not induce inflammation upon administration to naïve mice. To test whether viola would protect mice from an autoimmune inflammation, Experimental Autoimmune Encephalomyelitis (EAE)-inflicted mice were given viola i.p. at disease onset, at the 10th day from immunization. Viola-treated mice developed mild EAE disease in contrast with placebo-treated mice. The frequencies of dendritic cells and macrophages were unaltered in EAE mice treated with viola. However, the sole administration of viola augmented the levels of splenic regulatory T cells (CD4+Foxp3+). We also found that adoptive transfer of viola-elicited regulatory T cells significantly reduced EAE. Our study shows, for the first time, that violacein is able to modulate acute and chronic inflammation. Amelioration relied in suppression of cytokine production (in acute inflammation) and stimulation of regulatory T cells (in chronic inflammation). New studies must be conducted in order to assess the possible use of viola in therapeutic approaches in human autoimmune diseases.

Violacein induces p44/42 mitogen-activated protein kinase-mediated solid tumor cell death and inhibits tumor cell migration

Microbial secondary metabolites have emerged as alternative novel drugs for the treatment of human cancers. Violacein, a purple pigment produced by Chromobacterium violaceum, was investigated in the present study for its anti-tumor properties in tumor cell lines. Clinically applicable concentrations of violacein were demonstrated to inhibit the proliferative capacity of tumor cell lines according to a crystal violet proliferation assay. The underlying mechanism was the promotion of apoptotic cell death, as indicated by poly(ADP ribose) polymerase cleavage and p44/42 mitogen-activated protein kinase signaling determined by western blot analysis. Collectively, this provided mechanistic evidence that violacein elicits extracellular-signal regulated kinase-induced apoptosis via the intrinsic pathway. The anti-malignant properties of violacein in the present study were further demonstrated by its inhibitory effects on brain tumor cell migration, specifically glioblastomas, one of the most invasive and therapeutically resistant neoplasms in the clinic. Additionally, solid tumors examined in the present study displayed differential cellular responses and sensitivities to violacein as observed by morphologically induced cellular changes that contributed to its anti-migratory properties. In conclusion, violacein is a novel natural product with the potential to kill several types of human tumor cell lines, as well as prevent disease recurrence by antagonizing cellular processes that contribute to metastatic invasion.

Violacein anticancer activity is enhanced under hypoxia

Current cancer treatments of solid tumours such as chemotherapy and radiotherapy, have yet to produce effective therapeutic results due to non-specific targeting. This has led to many complications, such as toxicities in cancer patients. The ability of natural compounds in inducing programmed cell death (apoptosis), a process dysregulated in cancer cells, has been extensively studied in recent studies. This study assessed the anti-proliferative activity of violacein in a number of human cancer cell lines under normal and hypoxic conditions. Furthermore, we investigated its effects in a tumour‑bearing subcutaneous mouse model. We also examined the ability of a tumour‑targeting Salmonella strain to produce violacein for local delivery within the tumour microenvironment. The results showed that hypoxia significantly increased the cytotoxic effects of violacein. The most significant reduction in the IC50 was in the HT29 (12.6-fold) and HCT116 (4.8-fold) colon cancer cell lines, HN5 head and neck squamous carcinoma cell line (6.5-fold), and MCF-7 breast ductal carcinoma cell line (4-fold). Among the cell lines tested for active caspase-3/7 activity, violacein only increased caspase-3/7 activity in the A549 non-small lung cancer cell line. In vivo efficacy of violacein showed that HN5 tumour‑bearing mice had regressed tumours during the treatment period and survival increased. The results also showed that transfer of the violacein biosynthetic cluster into the oncolytic strain VNP20009 of Salmonella resulted in the production of active violacein, suggesting targeted delivery of violacein by VNP20009. Taken together, our study has shown that hypoxia synergises the effects of violacein and the results from the in vivo administration of violacein require further investigation of violacein as an anticancer chemotherapeutic.

Violacein inhibits matrix metalloproteinase mediated CXCR4 expression: potential anti-tumor effect in cancer invasion and metastasis

Matrix metalloproteinases (MMP-2 and -9) play an important role in the tumor metastasis through cleavage of proinflammatory cytokines. Violacein a small molecule produced by Chromobacterium violaceum and has been implicated with anti-cancer effects. In this study we investigated the molecular basis of violacein mediated downregulation of CXCL12/CXCR4, chemokine-receptor ligand interaction. Zymography analysis demonstrated that violacein significantly inhibited the cytokine (TNFα and TGFβ) mediated MMP-2 activation in MCF-7 breast cancer cell line. MMP-2 plays a critical role in the secretion of inflammatory chemokine, CXCL12, involved in cell migration and cancer metastasis. ELISA analysis demonstrated that violacein inhibited the secretion of CXCL12 from the activated MCF-7 cells. Further, we show that MMP-2/-9 act synergistically at two distinct steps towards the membrane expression of the tumor metastasis chemokine receptor, CXCR4. Violacein efficiently downregulated the CXCR4 membrane expression through MMP-9 inhibition. Taken together, these studies demonstrate a unique anti-tumor mechanism of action of violacein through reduction of CXCL12/CXCR4 interaction. These studies could offer a novel venue for violacein in cancer therapy.

Calix[6]arene bypasses human pancreatic cancer aggressiveness: downregulation of receptor tyrosine kinases and induction of cell death by reticulum stress and autophagy

Pancreatic cancer ranks fourth among cancer-related causes of death in North America. Minimal progress has been made in the diagnosis and treatment of patients with late-stage tumors. Moreover, pancreatic cancer aggressiveness is closely related to high levels of pro-survival mediators, which can ultimately lead to rapid disease progression, resistance and metastasis. The main goal of this study was to define the mechanisms by which calix[6]arene, but not other calixarenes, efficiently decreases the aggressiveness of a drug resistant human pancreas carcinoma cell line (Panc-1). Calix[6]arene was more potent in reducing Panc-1 cell viability than gemcitabine and 5-fluorouracil. In relation to the underlying mechanisms of cytotoxic effects, it led to cell cycle arrest in the G0/G1 phase through downregulation of PIM1, CDK2, CDK4 and retinoblastoma proteins. Importantly, calix[6]arene abolished signal transduction of Mer and AXL tyrosine kinase receptors, both of which are usually overexpressed in pancreatic cancer. Accordingly, inhibition of PI3K and mTOR was also observed, and these proteins are positively modulated by Mer and AXL. Despite decreasing the phosphorylation of AKT at Thr308, calix[6]arene caused an increase in phosphorylation at Ser473. These findings in conjunction with increased BiP and IRE1-α provide a molecular basis explaining the capacity of calix[6]arene to trigger endoplasmic reticulum stress and autophagic cell death. Our findings highlight calix[6]arene as a potential candidate for overcoming pancreatic cancer aggressiveness. Importantly, we provide evidence that calix[6]arene affects a broad array of key targets that are usually dysfunctional in pancreatic cancer, a highly desirable characteristic for chemotherapeutics.

Carbocyclization versus oxycyclization on the metal-catalyzed reactions of oxyallenyl C3-linked indoles

The preparation of previously unknown (indol-3-yl)-α-allenols and -allenones was accomplished from indole-3-carbaldehydes, through indium-mediated Barbier allenylation reaction taking advantage of the N-(2-pyridyl)sulfonyl group. Metal-catalyzed cyclizations of oxyallenyl C3-linked indoles proceeded in two ways depending on the presence or absence of the N-(2-pyridyl)sulfonyl group. For allenols, gold-catalyzed oxycyclization occurred in the presence of the protecting group; in the absence of the protecting group, palladium- and gold-catalyzed benzannulations operated. On the contrary, under gold catalysis furyl-indoles were obtained as exclusive products from NH-allenones, while 5-endo carbocyclization adducts were the major components starting from N-SO2py-protected allenones. These cyclization reactions have been developed experimentally, and their mechanisms have additionally been investigated by a computational study.