Antineoplastic properties of bacteriocins: revisiting potential active agents

Bacteriocins in Cancer Treatment: Mechanisms and Clinical Potentials

Cancer poses a severe threat to human health. Although conventional chemotherapy remains a cornerstone of cancer treatment, its significant side effects and the growing issue of drug resistance necessitate the urgent search for more efficient and less toxic anticancer drugs. In recent years, bacteriocins, antimicrobial peptides of microbial origin, have garnered significant attention due to their targeted antitumor activity. This unique activity is mainly attributed to their cationic and amphiphilic nature, which enables bacteriocins to specifically kill tumor cells without harming normal cells. When involving non-membrane-disrupting mechanisms, such as apoptosis induction, cell cycle blockade, and metastasis inhibition, the core mechanism of action is achieved by disrupting cell membranes, which endows bacteriocins with low drug resistance and high selectivity. However, the susceptibility of bacteriocins to hydrolysis and hemolysis in vivo limits their clinical application. To overcome these challenges, structural optimization of bacteriocins or their combination with nanotechnology is proposed for future development. This review aims to study the mechanism of action and current research status of bacteriocins as anticancer treatments, thus providing new insights for their clinical development and application.

Bacteriocins: Curial guardians of gastrointestinal tract

The human gastrointestinal (GI) tract microbiome secretes various metabolites that play pivotal roles in maintaining host physiological balance and influencing disease progression. Among these metabolites, bacteriocins-small, heat-stable peptides synthesized by ribosomes-are notably prevalent in the GI region. Their multifaceted benefits have garnered significant interest in the scientific community. This review comprehensively explores the methods for mining bacteriocins (traditional separation and purification, bioinformatics, and artificial intelligence), their effects on the stomach and intestines, and their complex bioactive mechanisms. These mechanisms include flora regulation, biological barrier restoration, and intervention in epithelial cell pathways. By detailing each well-documented bacteriocin, we reveal the diverse ways in which bacteriocins interact with the GI environment. Moreover, the future research direction is prospected. By further studying the function and interaction of intestinal bacteriocins, we can discover new pharmacological targets and develop drugs targeting intestinal bacteriocins to regulate and improve human health. It provides innovative ideas and infinite possibilities for further exploration, development, and utilization of bacteriocins. The inevitable fact is that the continuously exploration of bacteriocins is sure to bring the promising future for demic GI health understanding and interference strategy.

Do Bacteria Provide an Alternative to Cancer Treatment and What Role Does Lactic Acid Bacteria Play?

Cancer is one of the leading causes of mortality and morbidity worldwide. According to 2022 statistics from the World Health Organization (WHO), close to 10 million deaths have been reported in 2020 and it is estimated that the number of cancer cases world-wide could increase to 21.6 million by 2030. Breast, lung, thyroid, pancreatic, liver, prostate, bladder, kidney, pelvis, colon, and rectum cancers are the most prevalent. Each year, approximately 400,000 children develop cancer. Treatment between countries vary, but usually includes either surgery, radiotherapy, or chemotherapy. Modern treatments such as hormone-, immuno- and antibody-based therapies are becoming increasingly popular. Several recent reports have been published on toxins, antibiotics, bacteriocins, non-ribosomal peptides, polyketides, phenylpropanoids, phenylflavonoids, purine nucleosides, short chain fatty acids (SCFAs) and enzymes with anticancer properties. Most of these molecules target cancer cells in a selective manner, either directly or indirectly through specific pathways. This review discusses the role of bacteria, including lactic acid bacteria, and their metabolites in the treatment of cancer.

Evaluation of Apoptotic Gene Expression in Hepatoma Cell Line (HepG2) Following Nisin Treatment

Objective:

The present study aims to examine the effects of nisin on the survival and apoptosis of the hepatoma cell line HepG2 and to investigate possible apoptosis pathways activated by nisin.

Materials and Methods:

For this purpose, viability and apoptosis of the cells were accomplished by the nisin treatment using the MTT assay and Annexin-V-fluorescein/propidium iodide (PI) double staining, respectively. Additionally, the human apoptosis PCR array was performed to determine pathways or genes activated by nisin during possible apoptosis.

Results:

The results of the present study showed that nisin was able to decrease cell viability (IC₅₀ ~ 40 µg/ml) in a dose-dependent manner and could induce apoptosis in HepG2 cells. PCR data indicated a considerable increase in the expression of genes, such as caspase and BCL2 families, involved in the induction of apoptosis.

Conclusions:

The data from this study showed that overexpression of genes involved in the intrinsic pathway of apoptosis, especially caspase-9 and BID, increased apoptosis in HepG2 cells treated by nisin, compared to the control group.

Exploiting Zebrafish Xenografts for Testing the in vivo Antitumorigenic Activity of Microcin E492 Against Human Colorectal Cancer Cells

One of the approaches to address cancer treatment is to develop new drugs not only to obtain compounds with less side effects, but also to have a broader set of alternatives to tackle the resistant forms of this pathology. In this regard, growing evidence supports the use of bacteria-derived peptides such as bacteriocins, which have emerged as promising anti-cancer molecules. In addition to test the activity of these molecules on cancer cells in culture, their in vivo antitumorigenic properties must be validated in animal models. Although the standard approach for such assays employs experiments in nude mice, at the initial stages of testing, the use of high-throughput animal models would permit rapid proof-of-concept experiments, screening a high number of compounds, and thus increasing the possibilities of finding new anti-cancer molecules. A validated and promising alternative animal model are zebrafish larvae harboring xenografts of human cancer cells. Here, we addressed the anti-cancer properties of the antibacterial peptide microcin E492 (MccE492), a bacteriocin produced by Klebsiella pneumoniae, showing that this peptide has a marked cytotoxic effect on human colorectal cancer cells in vitro. Furthermore, we developed a zebrafish xenograft model using these cells to test the antitumor effect of MccE492 in vivo, demonstrating that intratumor injection of this peptide significantly reduced the tumor cell mass. Our results provide, for the first time, evidence of the in vivo antitumoral properties of a bacteriocin tested in an animal model. This evidence strongly supports the potential of this bacteriocin for the development of novel anti-cancer therapies.

Bacteriocin production by mucosal bacteria in current and previous colorectal neoplasia

BACKGROUND

Optimal therapy for colorectal carcinoma (CRC), a frequently diagnosed malignancy, does not exist. Some of colicins and microcins, ribosomally synthesized peptides by gramnegative bacteria, have shown significant biological activity specifically against different cancer cells in vitro and in vivo conditions. The aim of this prospective study was to evaluate natural colicin and microcin production by large intestinal mucosal bacteria in each stage of colorectal neoplasia and in those with a history of colorectal neoplasia.

METHODS

A total of 21 patients with non-advanced adenoma (non-a-A; 16/21 with current and 5/21 with history of non-a-A), 20 patients with advanced colorectal adenoma (a-A; 11/20 with current and 9/20 with history of a-A), 22 individuals with CRC (9/22 with current and 13/22 with history of CRC) and 20 controls were enrolled. Mucosal biopsies from the caecum, transverse colon and the rectum were taken during colonoscopy in each individual. Microbiological culture followed. Production of colicins and microcins was evaluated by PCR methods.

RESULTS

A total of 239 mucosal biopsies were taken. Production of colicins and microcins was significantly more frequent in individuals with non-a-A, a-A and CRC compared to controls. No significant difference in colicin and microcin production was found between patients with current and previous non-a-A, a-A and CRC. Significantly more frequent production of colicins was observed in men compared to women at the stage of colorectal carcinoma. A later onset of increased production of microcins during the adenoma-carcinoma sequence has been observed in males compared to females.

CONCLUSIONS

Strains isolated from large intestinal mucosa in patients with colorectal neoplasia produce colicins and microcins more frequently compared to controls. Bacteriocin production does not differ between patients with current and previous colorectal neoplasia. Fundamental differences in bacteriocin production have been confirmed between males and females.

Microcins in Enterobacteriaceae: Peptide Antimicrobials in the Eco-Active Intestinal Chemosphere

Microcins are low-molecular-weight, ribosomally produced, highly stable, bacterial-inhibitory molecules involved in competitive, and amensalistic interactions between Enterobacteriaceae in the intestine. These interactions take place in a highly complex chemical landscape, the intestinal eco-active chemosphere, composed of chemical substances that positively or negatively influence bacterial growth, including those originated from nutrient uptake, and those produced by the action of the human or animal host and the intestinal microbiome. The contribution of bacteria results from their effect on the host generated molecules, on food and digested food, and organic substances from microbial origin, including from bacterial degradation. Here, we comprehensively review the main chemical substances present in the human intestinal chemosphere, particularly of those having inhibitory effects on microorganisms. With this background, and focusing on Enterobacteriaceae, the most relevant human pathogens from the intestinal microbiota, the microcin’s history and classification, mechanisms of action, and mechanisms involved in microcin’s immunity (in microcin producers) and resistance (non-producers) are reviewed. Products from the chemosphere likely modulate the ecological effects of microcin activity. Several cross-resistance mechanisms are shared by microcins, colicins, bacteriophages, and some conventional antibiotics, which are expected to produce cross-effects. Double-microcin-producing strains (such as microcins MccM and MccH47) have been successfully used for decades in the control of pathogenic gut organisms. Microcins are associated with successful gut colonization, facilitating translocation and invasion, leading to bacteremia, and urinary tract infections. In fact, Escherichia coli strains from the more invasive phylogroups (e.g., B2) are frequently microcinogenic. A publicly accessible APD3 database http://aps.unmc.edu/AP/ shows particular genes encoding microcins in 34.1% of E. coli strains (mostly MccV, MccM, MccH47, and MccI47), and much less in Shigella and Salmonella (<2%). Some 4.65% of Klebsiella pneumoniae are microcinogenic (mostly with MccE492), and even less in Enterobacter or Citrobacter (mostly MccS). The high frequency and variety of microcins in some Enterobacteriaceae indicate key ecological functions, a notion supported by their dominance in the intestinal microbiota of biosynthetic gene clusters involved in the synthesis of post-translationally modified peptide microcins.

Bacteriocins: perspective for the development of novel anticancer drugs

Antimicrobial peptides (AMPs) from prokaryotic source also known as bacteriocins are ribosomally synthesized by bacteria belonging to different eubacterial taxonomic branches. Most of these AMPs are low molecular weight cationic membrane active peptides that disrupt membrane by forming pores in target cell membranes resulting in cell death. While these peptides known to exhibit broad-spectrum antimicrobial activity, including antibacterial and antifungal, they displayed minimal cytotoxicity to the host cells. Their antimicrobial efficacy has been demonstrated in vivo using diverse animal infection models. Therefore, we have discussed some of the promising peptides for their ability towards potential therapeutic applications. Further, some of these bacteriocins have also been reported to exhibit significant biological activity against various types of cancer cells in different experimental studies. In fact, differential cytotoxicity towards cancer cells as compared to normal cells by certain bacteriocins directs for a much focused research to utilize these compounds as novel therapeutic agents. In this review, bacteriocins that demonstrated antitumor activity against diverse cancer cell lines have been discussed emphasizing their biochemical features, selectivity against extra targets and molecular mechanisms of action.

Anticancer properties of a defensin like class IId bacteriocin Laterosporulin10

Laterosporulin10 (LS10) is a defensin like peptide from Brevibacillus sp. strain SKDU10 that inhibited microbial pathogens. However, in this study, anticancer activity of LS10 was examined against different cancer cell lines and compared with normal cells. LS10 displayed cytotoxicity against cancer cells like MCF-7, HEK293T, HT1080, HeLa and H1299 at below 10 μM concentration, but not against prostate epithelium cells RWPE-1. Additionally, no hemolysis was observed at significantly higher concentration compared to IC₅₀ values observed for different cancer cell lines. Release of lactate dehydrogenase from cancer cell lines at 15 μM concentration upon 120 min treatment indicated the lytic ability of LS10. Accordingly, electron microscopy experiments also confirmed the necrotic effect of LS10 at 15 μM concentration against cancer cells. Furthermore, flow cytometry analysis of treated cancer cell lines revealed that LS10 induce apoptosis even at 2.5 μM concentration. Nevertheless, RWPE-1 cells remained viable even at 20 μM concentration. These results provide evidence that LS10 is an anticancer bacteriocin, which causes apoptotic and necrotic death of cancer cells at lower and higher concentrations, respectively. Taken all results together, the present study signifies that LS10 is an anticancer peptide that could be further developed for therapeutic applications.

Enterocin AS-48 as Evidence for the Use of Bacteriocins as New Leishmanicidal Agents

We report the feasibility of enterocin AS-48, a circular cationic peptide produced by Enterococcus faecalis, as a new leishmanicidal agent. AS-48 is lethal to Leishmania promastigotes as well as to axenic and intracellular amastigotes at low micromolar concentrations, with scarce cytotoxicity to macrophages. AS-48 induced a fast bioenergetic collapse of L. donovani promastigotes but only a partial permeation of their plasma membrane with limited entrance of vital dyes, even at concentrations beyond its full lethality. Fluoresceinated AS-48 was visualized inside parasites by confocal microscopy and seen to cause mitochondrial depolarization and reactive oxygen species production. Altogether, AS-48 appeared to have a mixed leishmanicidal mechanism that includes both plasma membrane permeabilization and additional intracellular targets, with mitochondrial dysfunctionality being of special relevance. This complex leishmanicidal mechanism of AS-48 persisted even for the killing of intracellular amastigotes, as evidenced by transmission electron microscopy. We demonstrated the potentiality of AS-48 as a new and safe leishmanicidal agent, expanding the growing repertoire of eukaryotic targets for bacteriocins, and our results provide a proof of mechanism for the search of new leishmanicidal bacteriocins, whose diversity constitutes an almost endless source for new structures at moderate production cost and whose safe use on food preservation is well established.

Breast Cancer Targeting Peptide Binds Keratin 1: A New Molecular Marker for Targeted Drug Delivery to Breast Cancer

The biomarkers or receptors expressed on cancer cells and the targeting ligands with high binding affinity for biomarkers play a key role in early detection and treatment of breast cancer. The breast cancer targeting peptide p160 (12-mer) and its enzymatically stable analogue 18-4 (10-mer) showed marked potential for breast cancer drug delivery using cell studies and animal models. Herein, we used affinity purification, liquid chromatography-tandem mass spectrometry, and proteomics to identify keratin 1 (KRT1) as the target receptor highly expressed on breast cancer cells for p160 peptide(s). Western blot and immunocytochemistry in MCF-7 breast cancer cells confirmed the identity of KRT1. We demonstrate that the p160 or 18-4 binding to MCF-7 breast cancer cells is dependent on the expression of KRT1, and we confirm peptide-KRT1 binding specificity using SPR experiments (K_d ∼ 1.1 μM and 0.98 μM for p160 and 18-4, respectively). Furthermore, we assessed the ability of peptide 18-4 to improve the cellular uptake and anticancer activity of a pro-apoptotic antimicrobial peptide, microcin J25 (MccJ25), in breast cancer cells. A covalent conjugate of peptide 18-4 with MccJ25 showed preferential cytotoxicity toward breast cancer cells with minimal cytotoxicity against normal HUVEC cells. The conjugate inhibited the growth of MDA-MB-435 MDR multidrug-resistant cells with an IC₅₀ comparable to that of nonresistant cells. Conjugation improved selective cellular uptake of MccJ25, and the conjugate triggered cancer cell death by apoptosis. Our findings establish KRT1 as a new marker for breast cancer targeting. Additionally, it pinpoints the potential use of antimicrobial lasso peptides as a novel class of anticancer therapeutics.

Human extraintestinal pathogenic Escherichia coli strains differ in prevalence of virulence factors, phylogroups, and bacteriocin determinants

BACKGROUND

The study used a set of 407 human extraintestinal pathogenic E. coli strains (ExPEC) isolated from (1) skin and soft tissue infections, (2) respiratory infections, (3) intra-abdominal infections, and (4) genital smears. The set was tested for bacteriocin production, for prevalence of bacteriocin and virulence determinants, and for phylogenetic typing. Results obtained from the group of ExPEC strains were compared to data from our previously published analyses of 1283 fecal commensal E. coli strains.

RESULTS

The frequency of bacteriocinogeny was significantly higher in the set of ExPEC strains (63.1 %), compared to fecal E. coli (54.2 %; p < 0.01). Microcin producers and microcin determinants dominated in ExPEC strains, while colicin producers and colicin determinants were more frequent in fecal E. coli (p < 0.01). Higher production of microcin M and lower production of microcin B17, colicin Ib, and Js was detected in the set of ExPEC strains. ExPEC strains had a significantly higher prevalence of phylogenetic group B2 (52.6 %) compared to fecal E. coli strains (38.3 %; p < 0.01).

CONCLUSIONS

Human ExPEC strains were shown to differ from human fecal strains in a number of parameters including bacteriocin production, prevalence of several bacteriocin and virulence determinants, and prevalence of phylogenetic groups. Differences in these parameters were also identified within subgroups of ExPEC strains of diverse origin. While some microcin determinants (mM, mH47) were associated with virulent strains, other bacteriocin types (mB17, Ib, and Js) were associated with fecal flora.

Discovery of Azurin-Like Anticancer Bacteriocins from Human Gut Microbiome through Homology Modeling and Molecular Docking against the Tumor Suppressor p53

Azurin from Pseudomonas aeruginosa is known anticancer bacteriocin, which can specifically penetrate human cancer cells and induce apoptosis. We hypothesized that pathogenic and commensal bacteria with long term residence in human body can produce azurin-like bacteriocins as a weapon against the invasion of cancers. In our previous work, putative bacteriocins have been screened from complete genomes of 66 dominant bacteria species in human gut microbiota and subsequently characterized by subjecting them as functional annotation algorithms with azurin as control. We have qualitatively predicted 14 putative bacteriocins that possessed functional properties very similar to those of azurin. In this work, we perform a number of quantitative and structure-based analyses including hydrophobic percentage calculation, structural modeling, and molecular docking study of bacteriocins of interest against protein p53, a cancer target. Finally, we have identified 8 putative bacteriocins that bind p53 in a same manner as p28-azurin and azurin, in which 3 peptides (p1seq16, p2seq20, and p3seq24) shared with our previous study and 5 novel ones (p1seq09, p2seq05, p2seq08, p3seq02, and p3seq17) discovered in the first time. These bacteriocins are suggested for further in vitro tests in different neoplastic line cells.

Biomedical applications of nisin

Nisin is a bacteriocin produced by a group of Gram-positive bacteria that belongs to Lactococcus and Streptococcus species. Nisin is classified as a Type A (I) lantibiotic that is synthesized from mRNA and the translated peptide contains several unusual amino acids due to post-translational modifications. Over the past few decades, nisin has been used widely as a food biopreservative. Since then, many natural and genetically modified variants of nisin have been identified and studied for their unique antimicrobial properties. Nisin is FDA approved and generally regarded as a safe peptide with recognized potential for clinical use. Over the past two decades the application of nisin has been extended to biomedical fields. Studies have reported that nisin can prevent the growth of drug-resistant bacterial strains, such as methicillin-resistant Staphylococcus aureus, Streptococcus pneumoniae, Enterococci and Clostridium difficile. Nisin has now been shown to have antimicrobial activity against both Gram-positive and Gram-negative disease-associated pathogens. Nisin has been reported to have anti-biofilm properties and can work synergistically in combination with conventional therapeutic drugs. In addition, like host-defence peptides, nisin may activate the adaptive immune response and have an immunomodulatory role. Increasing evidence indicates that nisin can influence the growth of tumours and exhibit selective cytotoxicity towards cancer cells. Collectively, the application of nisin has advanced beyond its role as a food biopreservative. Thus, this review will describe and compare studies on nisin and provide insight into its future biomedical applications.

Potential Applications of the Cyclic Peptide Enterocin AS-48 in the Preservation of Vegetable Foods and Beverages

Bacteriocins are antimicrobial peptides produced by bacteria. Among them, the enterococcal bacteriocin (enterocin) AS-48 stands for its peculiar characteristics and broad-spectrum antimicrobial activity. AS-48 belongs to the class of circular bacteriocins and has been studied in depth in several aspects: peptide structure, genetic determinants, and mode of action. Recently, a wealth of knowledge has accumulated on the antibacterial activity of this bacteriocin against foodborne pathogenic and spoilage bacteria in food systems, especially in vegetable foods and drinks. This work provides a general overview on the results from tests carried out with AS-48 in different vegetable food categories (such as fruit juices, ciders, sport and energy drinks, fresh fruits and vegetables, pre-cooked ready to eat foods, canned vegetables, and bakery products). Depending on the food substrate, the bacteriocin has been tested alone or as part of hurdle technology, in combination with physico-chemical treatments (such as mild heat treatments or high-intensity pulsed electric fields) and other antimicrobial substances (such as essential oils, phenolic compounds, and chemical preservatives). Since the work carried out on bacteriocins in preservation of vegetable foods and drinks is much more limited compared to meat and dairy products, the results reported for AS-48 may open new possibilities in the field of bacteriocin applications.

Bacteriocins as Potential Anticancer Agents

Cancer remains one of the leading causes of deaths worldwide, despite advances in its treatment and detection. The conventional chemotherapeutic agents used for the treatment of cancer have non-specific toxicity toward normal body cells that cause various side effects. Secondly, cancer cells are known to develop chemotherapy resistance in due course of treatment. Thus, the demand for novel anti-cancer agents is increasing day by day. Some of the experimental studies have reported the therapeutic potential of bacteriocins against various types of cancer cell lines. Bacteriocins are ribosomally-synthesized cationic peptides secreted by almost all groups of bacteria. Some bacteriocins have shown selective cytotoxicity toward cancer cells as compared to normal cells. This makes them promising candidates for further investigation and clinical trials. In this review article, we present the overview of the various cancer cell-specific cytotoxic bacteriocins, their mode of action and efficacies.

Nisin ZP, a Bacteriocin and Food Preservative, Inhibits Head and Neck Cancer Tumorigenesis and Prolongs Survival

The use of small antimicrobial peptides or bacteriocins, like nisin, to treat cancer is a new approach that holds great promise. Nisin exemplifies this new approach because it has been used safely in humans for many years as a food preservative, and recent laboratory studies support its anti-tumor potential in head and neck cancer. Previously, we showed that nisin (2.5%, low content) has antitumor potential in head and neck squamous cell carcinoma (HNSCC) in vitro and in vivo. The current studies explored a naturally occurring variant of nisin (nisin ZP; 95%, high content) for its antitumor effects in vitro and in vivo. Nisin ZP induced the greatest level of apoptosis in HNSCC cells compared to low content nisin. HNSCC cells treated with increasing concentrations of nisin ZP exhibited increasing levels of apoptosis and decreasing levels of cell proliferation, clonogenic capacity, and sphere formation. Nisin ZP induced apoptosis through a calpain-dependent pathway in HNSCC cells but not in human oral keratinocytes. Nisin ZP also induced apoptosis dose-dependently in human umbilical vein endothelial cells (HUVEC) with concomitant decreases in vascular sprout formation in vitro and reduced intratumoral microvessel density in vivo. Nisin ZP reduced tumorigenesis in vivo and long-term treatment with nisin ZP extended survival. In addition, nisin treated mice exhibited normal organ histology with no evidence of inflammation, fibrosis or necrosis. In summary, nisin ZP exhibits greater antitumor effects than low content nisin, and thus has the potential to serve as a novel therapeutic for HNSCC.

Antimicrobial peptide m2163 or m2386 identified from Lactobacillus casei ATCC 334 can trigger apoptosis in the human colorectal cancer cell line SW480

Ribosomal synthesized antimicrobial peptides (AMPs) are widely distributed in nature and are toxic to certain microorganisms. Some of these AMPs are found to exhibit cytotoxic activity against the growth of cancer cells and thus have obvious anticancer potential. Here, we have studied the antiproliferation on the human colorectal cancer cell line SW480 of two AMPs, namely m2163 and m2386, identified by us from a lactic acid bacterium Lactobacillus casei ATCC 334 previously. A half maximal inhibitory concentration (IC50) of 40 μg/ml is determined first using the MTT (3-(4, 5-cimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay for either peptide m2163 or m2386. The apoptosis in treated SW480 cells by either peptide m2163 or m2386 is analyzed using flow cytometry with annexin V-fluorescein isothiocyanate (FITC) and propidium iodide double staining. These analyses show that a substantial population of treated SW480 cells can undergo apoptosis by either peptide m2163 or m2386. The real-time quantitative polymerase chain reaction (qPCR) and Western blot analyses are subsequently used to study how the apoptosis is induced in the treated SW480 cells by either peptide m2163 or m2386. While m2163 is found to induce the expression of Fas and TRAILR1, the expression of Fas, TNFR1, and TRAILR1 death receptors on the cell surface of treated SW480 cells is found to be induced by m2386. Further, the expression of some mitochondria-related apoptosis proteins such as Smac is found to be also induced, suggesting that either peptide m2163 or m2386 can trigger both the extrinsic and intrinsic apoptosis pathways. The cell membrane permeability is greatly enhanced upon treatment with either peptide m2163 or m2386 as analyzed by the flow cytometry using both FITC-labeled peptides. The flow cytometry is also used to analyze the fluorescence intensity given by FITC-m2163 in either the mitochondria or cytoplasm fraction of the treated and fractionated SW480 cells. It is found that the detected fluorescence intensity of the mitochondria fraction is much weaker than that of the cytoplasm one, suggesting that most of the FITC-m2163 peptides are located in the cytoplasm rather than the mitochondria. This is further confirmed by a confocal microscopy study that either peptide m2163 or m2386 can localize on the cell membrane for a substantial length of time and then penetrate into the cell cytoplasm to induce the apoptosis.

Escherichia coli strains of phylogenetic group B2 and D and bacteriocin production are associated with advanced colorectal neoplasia

Background

Colorectal cancer (CRC) is the 3rd most common cancer worldwide and the Czech Republic has the 6th highest incidence of CRC worldwide. Large intestinal microbiota play in its etiopathogenesis important role. Bacteriocins are proteins, produced by bacteria from the Enterobacteriaceae family. The aim of our prospective study was to assess the colonization of large intestinal mucosa by Escherichia coli strains and to investigate their bacteriocin production.

Methods

A total of 30 consecutive patients with colorectal adenoma, CRA (17 men, 13 women, aged 39–79, mean age 63 ± 9), 30 patients with CRC (23 men, 7 women, aged 38–86, mean age 67 ± 11) and 20 healthy controls (9 men, 11 women, age 23–84, mean age 55 ± 15) were enrolled into prospective study. Mucosal biopsies were taken in the caecum, transverse colon and rectum during pancolonoscopy. Microbiological culture, isolation and identification of bacteria followed. Bacteriocin production was assessed by growth inhibition of indicator strains E. coli K12-Row, E. coli C6 (phi), and Shigella sonnei 17. Identification of bacteriocin-encoding determinants and E. coli phylogroups was performed using PCR methods.

Results

A total of 622 strains were isolated and further investigated. A significantly higher frequency of simultaneous production of colicins and microcins was revealed in the group of patients with CRC, when compared to patients with CRA, p = 0.031. A significantly higher frequency of E. coli phylogroup D was found in patients with CRC, when compared to controls, p = 0.044. A significantly higher prevalence of bacteriocinogeny was confirmed in patients with advanced adenoma when compared to patients with non-advanced adenoma, p = 0.010. Increasing bacteriocinogeny was associated with an increasing stage of CRC (assessed according to TNM classification). Either E. coli phylogroup B2 or E. coli phylogroup D were isolated in biopsies of patients with right-sided CRC. A statistically higher incidence of E. coli phylogroup B2 was found in patients with right-sided CRC when compared to patients with left-sided CRC, p = 0.028.

Conclusions

Large intestinal mucosa of patients with more advanced colorectal neoplasia is colonized with more virulent strains of E. coli and higher production of bacteriocins is observed in these patients when compared to those with less advanced colorectal neoplasia.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-014-0733-7) contains supplementary material, which is available to authorized users.

Accumulation of single-stranded DNA in Escherichia coli carrying the colicin plasmid pColE3-CA38

We sequenced the complete 7118 bp circular plasmid pColE3-CA38 (pColE3) from Escherichia coli, located the previously identified colicin components together with two new ORFs that have homology to mobilization and transfer proteins, and found that pColE3 is highly similar to a plasmid present in enterohemorrhagic E. coli O111. We also found that unusual aspects of the plasmid include the inability to be completely digested with restriction endonucleases and asymmetric Phred DNA sequencing quality scores, with significantly lower scores in the forward direction relative to the colicin and immunity proteins consistent with plus (+) strand DNA. Comparing the A260 with picogreen double-stranded DNA (dsDNA) fluorescence and oligreen single-stranded DNA (ssDNA) fluorescence as well as metachromatic staining by acridine orange, we found that the undigested pColE3 DNA stains preferentially as ssDNA and that it coexists with dsDNA. We also identified ssDNA in pColE5 and pColE9 but not in pColE1. Colicin plasmids producing ssDNA may represent a new subclass of rolling-circle replication plasmids and add to the known similarities between colicins and filamentous phage.

Novel formulations for antimicrobial peptides

Peptides in general hold much promise as a major ingredient in novel supramolecular assemblies. They may become essential in vaccine design, antimicrobial chemotherapy, cancer immunotherapy, food preservation, organs transplants, design of novel materials for dentistry, formulations against diabetes and other important strategical applications. This review discusses how novel formulations may improve the therapeutic index of antimicrobial peptides by protecting their activity and improving their bioavailability. The diversity of novel formulations using lipids, liposomes, nanoparticles, polymers, micelles, etc., within the limits of nanotechnology may also provide novel applications going beyond antimicrobial chemotherapy.

Identification & Characterization of lactobacillus salavarius bacteriocins and its relevance in cancer therapeutics

Therapeutic agents with a goal to eradicate cancer needs to capable of inhibiting the growth and kill, any preformed tumor and should also inhibit oncogenic transformation of normal cells to cancer cells. Bacteriocins are bacterial proteins produced to prevent the growth of competing microorganisms in a particular biological niche and have been proved to possess antineoplastic activity. The entire genome of Lactobacillus salavarius was scanned for putative bacteriocins and subsequently these bacteriocins were characterized by subjecting them as functional annotation algorithms. Azurin is a well characterized bacteriocins with proven cytostatic and apoptotic effect against human cancer cell and was taken as control. Functional characterization revealed that the three bacteriocins Lsl_003, Lsl_0510, Lsl_0554 possessed functional properties very similar to that of Azurin. Molecular screening of these bacteriocins against the common cancer targets p53, Rb1 and AR revealed that Lsl_0510 possessed highest binding affinity towards the all the three receptors making it to ideal candidate for future cancer therapeutics.

ABBREVIATIONS

P53 - Protein 53, Rb1 - Retinoblastoma 1, AR - Androgen Receptor, Lsl - Lactobacillus salavarius.

Development of Class IIa Bacteriocins as Therapeutic Agents

Class IIa bacteriocins have been primarily explored as natural food preservatives, but there is much interest in exploring the application of these peptides as therapeutic antimicrobial agents. Bacteriocins of this class possess antimicrobial activity against several important human pathogens. Therefore, the therapeutic development of these bacteriocins will be reviewed. Biological and chemical modifications to both stabilize and increase the potency of bacteriocins are discussed, as well as the optimization of their production and purification. The suitability of bacteriocins as pharmaceuticals is explored through determinations of cytotoxicity, effects on the natural microbiota, and in vivo efficacy in mouse models. Recent results suggest that class IIa bacteriocins show promise as a class of therapeutic agents.

Solution structure of LCI, a novel antimicrobial peptide from Bacillus subtilis

LCI, a 47-residue cationic antimicrobial peptide (AMP) found in Bacillus subtilis, is one of the main effective components that have strong antimicrobial activity against Xanthomonas campestris pv Oryzea and Pseudomonas solanacearum PE1, etc. To provide insight into the activity of the peptide, we used nuclear magnetic resonance spectroscopy to determine the structure of recombinant LCI. The solution structure of LCI has a novel topology, containing a four-strand antiparallel β-sheet as the dominant secondary structure. It is the first structure of the LCI protein family. Different from any known β-structure AMPs, LCI contains no disulfide bridge or circular structure, suggesting that LCI is also a novel β-structure AMP.

[Host defense peptides and peptidomimetics as new weapons for cancer treatment]

Host defence peptides (HDP) produced by almost all species of living organisms and widely recognized as antimicrobial antibiotics have also proved to be capable of killing a wide variety of cancer cells. In this respect they have many advantages over conventional cytotoxic chemotherapeutic agents. They seem to kill cancer cells by effects on plasma membranes and/or the membranes of mitochondria. They are often effective against multidrug-resistant cells. They have a broad spectrum of activity in that their killing effects are not restricted to particular kinds of cancer. Above all they commonly have few side effects in that they do not have the same detrimental effects on normal cells as they do on cancer cells. It has been demonstrated that HDP can be used as effective adjuvants to conventional chemotherapeutic agents. In addition they have effects on neo-angiogenesis which is important in relation to tumour growth. HDP have been shown to be powerful immunomodulators in a number of circumstances and in this respect they are believed to be instrumental in strengthening immunological host defence against cancer cells. Importantly it has also been shown that certain HDP have the capability to alter the capacity of cells to import Ca ions by affecting the location and thus function of calreticulin. Such changes it has been argued are significant in facilitating the killing of tumour cells by immunogical means. HDP constitute a novel class of anticancer agents for which, as we develop better knowledge of their pharmacokinetic profiles and learn better how to tailor their administration, hold high promise to augment or even replace the currently available cytotoxic anticancer chemotherapeutic agents most of which owe their efficacy to their capacity to bind to and damage target cell DNA.