Dermcidin expression in hepatic cells improves survival without N-glycosylation, but requires asparagine residues

Preclinical Development of Seriniquinones as Selective Dermcidin Modulators for the Treatment of Melanoma

The bioactive natural product seriniquinone was discovered as a potential melanoma drug, which was produced by the as-yet-undescribed marine bacterium of the rare genus Serinicoccus. As part of a long-term research program aimed at the discovery of new agents for the treatment of cancer, seriniquinone revealed remarkable in vitro activity against a diversity of cancer cell lines in the US National Cancer Institute 60-cell line screening. Target deconvolution studies defined the seriniquinones as a new class of melanoma-selective agents that act in part by targeting dermcidin (DCD). The targeted DCD peptide has been recently examined and defined as a “pro-survival peptide” in cancer cells. While DCD was first isolated from human skin and thought to be only an antimicrobial peptide, currently DCD has been also identified as a peptide associated with the survival of cancer cells, through what is believed to be a disulfide-based conjugation with proteins that would normally induce apoptosis. However, the significantly enhanced potency of seriniquinone was of particular interest against the melanoma cell lines assessed in the NCI 60-cell line panel. This observed selectivity provided a driving force that resulted in a multidimensional program for the discovery of a usable drug with a new anticancer target and, therefore, a novel mode of action. Here, we provided an overview of the discovery and development efforts to date.

Proteome alterations in the aqueous humor reflect structural and functional phenotypes in patients with advanced normal-tension glaucoma

Previous reports have shown possible association between altered protein levels in aqueous humor (AH) and normal-tension glaucoma (NTG), but the underlying pathogenetic mechanism as well as specific molecular biomarkers for NTG remains still elusive. Here, we aimed to identify novel biomarkers for advanced NTG by analyzing the proteome of patient-derived AH and their correlation with various functional and structural parameters from the visual field test (VF), optical coherence tomography (OCT), and OCT angiography (OCTA). We determined differentially expressed proteins (DEPs) of the AH of patients with advanced NTG (n = 20) using label-free quantitative (LFQ) proteomics with pooled samples and data-independent acquisition (DIA) analysis with individual samples, and the roles of AH DEPs in biological pathways were evaluated using bioinformatics. We identified 603 proteins in the AH of patients with advanced NTG, and 61 of them were selected as DEPs via global proteome LFQ profiling. Individual DIA analyses identified a total of 12 DEPs as biomarker candidates, seven of which were upregulated, and five were downregulated. Gene ontology enrichment analysis revealed that those DEPs were mainly involved in the immune response. Moreover, IGFBP2, ENO1, C7, B2M, AMBP, DSP, and DCD showed a significant correlation with the mean deviation of VF and with peripapillary and macular parameters from OCT and OCTA. The present study provides possible molecular biomarkers for the diagnosis of advanced NTG.

Seriniquinones as Therapeutic Leads for Treatment of BRAF and NRAS Mutant Melanomas

Isolated from the marine bacteria Serinicoccus sp., seriniquinone (SQ1) has been characterized by its selective activity in melanoma cell lines marked by its modulation of human dermcidin and induction of autophagy and apoptosis. While an active lead, the lack of solubility of SQ1 in both organic and aqueous media has complicated its preclinical evaluation. In response, our team turned its effort to explore analogues with the goal of returning synthetically accessible materials with comparable selectivity and activity. The analogue SQ2 showed improved solubility and reached a 30-40-fold greater selectivity for melanoma cells. Here, we report a detailed comparison of the activity of SQ1 and SQ2 in SK-MEL-28 and SK-MEL-147 cell lines, carrying the top melanoma-associated mutations, BRAFV600E and NRASQ61R, respectively. These studies provide a definitive report on the activity, viability, clonogenicity, dermcidin expression, autophagy, and apoptosis induction following exposure to SQ1 or SQ2. Overall, these studies showed that SQ1 and SQ2 demonstrated comparable activity and modulation of dermcidin expression. These studies are further supported through the evaluation of a panel of basal expression of key-genes related to autophagy and apoptosis, providing further insight into the role of these mutations. To explore this rather as a survival or death mechanism, autophagy inhibition sensibilized BRAF mutants to SQ1 and SQ2, whereas the opposite happened to NRAS mutants. These data suggest that the seriniquinones remain active, independently of the melanoma mutation, and suggest the future combination of their application with inhibitors of autophagy to treat BRAF-mutated tumors.

Exhaled breath condensate biomarkers for the early diagnosis of lung cancer using proteomics

We explored whether the proteomic analysis of exhaled breath condensate (EBC) may provide biomarkers for noninvasive screening for the early detection of lung cancer (LC). EBC was collected from 192 individuals [49 control (C), 49 risk factor-smoking (S), 46 chronic obstructive pulmonary disease (COPD) and 48 LC]. With the use of liquid chromatography and tandem mass spectrometry, 348 different proteins with a different pattern among the four groups were identified in EBC samples. Significantly more proteins were identified in the EBC from LC compared with other groups (C: 12.4 ± 1.3; S: 15.3 ± 1; COPD: 14 ± 1.6; LC: 24.2 ± 3.6; P = 0.0001). Furthermore, the average number of proteins identified per sample was significantly higher in LC patients, and receiver operating characteristic curve (ROC) analysis showed an area under the curve of 0.8, indicating diagnostic value. Proteins frequently detected in EBC, such as dermcidin and hornerin, along with others much less frequently detected, such as hemoglobin and histones, were identified. Cytokeratins (KRTs) were the most abundant proteins in EBC samples, and levels of KRT6A, KRT6B, and KRT6C isoforms were significantly higher in samples from LC patients ( P = 0.0031, 0.0011, and 0.0009, respectively). Moreover, the amount of most KRTs in EBC samples from LC patients showed a significant positive correlation with tumor size. Finally, we used a random forest algorithm to generate a robust model using EBC protein data for the diagnosis of patients with LC where the area under the ROC curve obtained indicated a good classification (82%). Thus this study demonstrates that the proteomic analysis of EBC samples is an appropriated approach to develop biomarkers for the diagnosis of lung cancer.

Effect of purified fractions from cell culture supernate of high-density pre-B acute lymphoblastic leukemia cells (ALL3) on the growth of ALL3 cells at low density

The mechanisms underlying the aberrant growth and interactions between cells are not understood very well. The pre-B acute lymphoblastic leukemia cells directly obtained from an adult patient grow very poorly or do not grow at all at low density (LD), but grow better at high starting cell density (HD). We found that the LD ALL3 cells can be stimulated to grow in the presence of diffusible, soluble factors secreted by ALL3 cells themselves growing at high starting cell density. We then developed a biochemical purification procedure that allowed us to purify the factor(s) with stimulatory activity and analyzed them by nanoliquid chromatography-tandem mass spectrometry (nanoLC-MS/MS). Using nanoLC-MS/MS we have identified several proteins which were further processed using various bioinformatics tools. This resulted in eight protein candidates which might be responsible for the growth activity on non-growing LD ALL3 cells and their involvement in the stimulatory activity are discussed.

Anti-inflammatory peptide regulates the supply of heat shock protein 70 monomers: implications for aging and age-related disease

Reducing the levels of toxic protein aggregates has become a focus of therapy for disorders like Alzheimer's and Parkinson's diseases, as well as for the general deterioration of cells and tissues during aging. One approach has been an attempt to influence the production or activity of a class of reparative chaperones called heat shock proteins (HSPs), of which HSP70 is a promising candidate. Manipulation of HSP70 expression results in disposal of misfolded protein aggregates that accumulate in aging and disease models. Recently, HSP70 has been shown to bind specifically to an amino-terminal sequence of a human diffusible survival evasion peptide (DSEP), dermcidin. This sequence includes CHEC-9, an orally available anti-inflammatory and cell survival peptide. In the present study, we found that the CHEC-9 peptide also binds HSP70 in the cytosol of the cerebral cortex after oral delivery in normal rats. Western analysis of non-heat-denatured, unreduced samples suggested that peptide treatment increased the level of active HSP70 monomers from the pool of chaperone oligomers, a process that may be stimulated by potentiation of the chaperone's adenosine triphosphatase (ATPase). In these samples, a small but consistent gel shift was observed for glyceraldehyde 3-phosphate dehydrogenase (GAPDH), a multifunctional protein whose aggregation is influenced by HSP70. CHEC-9 treatment of an in vitro model of α-synuclein aggregation also results in HSP70-dependent dissolution of these aggregates. HSP70 oligomer-monomer equilibrium and its potential to control protein aggregate disease warrant increased experimental attention, especially if a peptide fragment of an endogenous human protein can influence the process.

Antimicrobial peptides: Possible anti-infective agents

Multidrug-resistant bacterial, fungal, viral, and parasitic infections are major health threats. The Infectious Diseases Society of America has expressed concern on the decrease of pharmaceutical companies working on antibiotic research and development. However, small companies, along with academic research institutes, are stepping forward to develop novel therapeutic methods to overcome the present healthcare situation. Among the leading alternatives to current drugs are antimicrobial peptides (AMPs), which are abundantly distributed in nature. AMPs exhibit broad-spectrum activity against a wide variety of bacteria, fungi, viruses, and parasites, and even cancerous cells. They also show potential immunomodulatory properties, and are highly responsive to infectious agents and innate immuno-stimulatory molecules. In recent years, many AMPs have undergone or are undergoing clinical development, and a few are commercially available for topical and other applications. In this review, we outline selected anion and cationic AMPs which are at various stages of development, from preliminary analysis to clinical drug development. Moreover, we also consider current production methods and delivery tools for AMPs, which must be improved for the effective use of these agents.

Dermcidin exerts its oncogenic effects in breast cancer via modulation of ERBB signaling

Background

We previously identified dermicidin (DCD), which encodes a growth and survival factor, as a gene amplified and overexpressed in a subset of breast tumors. Patients with DCD-positive breast cancer have worse prognostic features. We therefore searched for specific molecular signatures in DCD-positive breast carcinomas from patients and representative cell lines.

Methods

DCD expression was evaluated by qRT-PCR, immunohistochemical and immunoblot assays in normal and neoplastic tissues and cell lines. To investigate the role of DCD in breast tumorigenesis, we analyzed the consequences of its downregulation in human breast cancer cell lines using three specific shRNA lentiviral vectors. Genes up- and down-regulated by DCD were identified using Affymetrix microarray and analyzed by MetaCore Platform.

Results

We identified DCD splice variant (DCD-SV) that is co-expressed with DCD in primary invasive breast carcinomas and in other tissue types and cell lines. DCD expression in breast tumors from patients with clinical follow up data correlated with high histological grade, HER2 amplification and luminal subtype. We found that loss of DCD expression led to reduced cell proliferation, resistance to apoptosis, and suppressed tumorigenesis in immunodeficient mice. Network analysis of gene expression data revealed perturbed ERBB signaling following DCD shRNA expression including changes in the expression of ERBB receptors and their ligands.

Conclusions

These findings imply that DCD promotes breast tumorigenesis via modulation of ERBB signaling pathways. As ERBB signaling is also important for neural survival, HER2+ breast tumors may highjack DCD’s neural survival-promoting functions to promote tumorigenesis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1022-6) contains supplementary material, which is available to authorized users.

Functional identity of receptors for proteolysis-inducing factor on human and murine skeletal muscle

Background:

Cachexia in both mice and humans is associated with tumour production of a sulphated glycoprotein called proteolysis-inducing factor (PIF). In mice PIF binds with high affinity to a surface receptor in skeletal muscle, but little is known about the human receptor. This study compares the human PIF receptor with the murine.

Methods:

Human PIF was isolated from the G361 melanoma and murine PIF from the MAC16 colon adenocarcinoma. The human PIF receptor was isolated from human skeletal muscle myotubes. Protein synthesis and degradation induced by human and murine PIF was studied in human and murine skeletal muscle myotubes.

Results:

Both the human and murine PIF receptors showed the same immunoreactivity and Mr 40 000. Both murine and human PIF inhibited total protein synthesis and stimulated protein degradation in human and murine myotubes to about the same extent, and this was attenuated by a rabbit polyclonal antibody to the murine PIF receptor, but not by a non-specific rabbit antibody. Both murine and human PIF increased the activity of the ubiquitin–proteasome pathway in both human and murine myotubes, as evidenced by an increased ‘chymotrypsin-like' enzyme activity, protein expression of the 20S and 19S proteasome subunits, and increased expression of the ubiquitin ligases MuRF1 and MAFbx, and this was also attenuated by the anti-mouse PIF receptor antibody.

Conclusions:

These results suggest that the murine and human PIF receptors are identical.

The multiple facets of dermcidin in cell survival and host defense

Eccrine sweat glands, which are distributed over the whole bodies of primates and humans, have long been regarded mainly to have a function in thermoregulation. However, the discovery of dermcidin-derived antimicrobial peptides in eccrine sweat demonstrated that sweat actively participates in the constitutive innate immune defense of human skin against infection. In the meantime, a number of studies proved the importance of dermcidin in skin host defense. Several reports also state that peptides processed from the dermcidin precursor protein exhibit a range of other biological functions in neuronal and cancer cells. This review summarizes the evidence gathered until now concerning the expression of dermcidin and the functional relevance of dermcidin-derived peptides.

HSP70 natively and specifically associates with an N-terminal dermcidin-derived peptide that contains an HLA-A*03 antigenic epitope

Tumor cells very often have elevated expression of HSP70, the anti-apoptotic properties of which contribute to overall tumor survival. Independent of its anti-apoptotic properties, HSP70 was also suggested to be involved in the antigen presentation process by chaperoning cytosolic peptides, thus protecting them from rapid degradation and securing the peptide pool for further processing. In this study, we identified a 33-amino acid N-terminal dermcidin (DCD)-derived peptide from the repertoire of in vivo HSP70-associated peptides isolated from a leukemic cell line, K562. The DCD peptide has been previously shown to be involved in tumorigenesis, to increase tumor survival rate, to improve tumor stress resistance, and to aid growth. We show that HSP70 is a specific binding partner for the DCD prosurvival peptide and define an ATP-dependent DCD-binding site (GNPCH). We also identify an HLA-A*03 antigenic epitope within the DCD peptide, which follows and partially overlaps the HSP70-binding site (CHEASAAQK). This study describes the interaction between HSP70 and the DCD-derived prosurvival peptide, an interaction that may direct the peptide toward antigen presentation and independently contribute to the prosurvival mechanism mediated by DCD.

Variation in dermcidin expression in a range of primary human tumours and in hypoxic/oxidatively stressed human cell lines

Dermcidin acts as a survival factor in a variety of cancer cell lines under hypoxia or oxidative stress. The aim of this study was to evaluate dermcidin expression in cell lines following simulation of tumour microenvironmental conditions and in a range of primary tumours. Tumour tissues were collected from patients with oesophageal (28 samples), gastric (20), pancreatic (five), bile duct (one) and prostatic (52) carcinomas as well as 30 benign tissue samples, for assessment of dermcidin mRNA levels using real-time PCR. Dermcidin expression was assessed in prostatic and pancreatic cancer cell lines, with and without induction of hypoxia or oxidative stress. Dermcidin mRNA expression was very low or absent in both unstressed and stressed prostate cell lines. None of the primary prostate tissue, benign or malignant, expressed dermcidin mRNA. Only two (4%) of the gastro-oesophageal cancer samples expressed moderate quantities of dermcidin mRNA. However, three (60%) of the pancreatic cancer samples and the single cholangiocarcinoma specimen had moderate/high levels of dermcidin expression. Of the two pancreatic cancer cell lines, one expressed dermcidin moderately but neither showed a response to hypoxia or oxidative stress. Expression of dermcidin in human primary tumours appears highly variable and is not induced substantially by hypoxia/oxidative stress in cell line model systems. The relationship of these findings to dermcidin protein levels and cell survival remains to be determined.

The dermcidin gene in cancer: role in cachexia, carcinogenesis and tumour cell survival

PURPOSE OF REVIEW

The diverse protein products of the dermcidin gene are relevant to immunity, cancer cell progression and cancer cachexia. This article evaluates recent developments/controversies around dermcidin.

RECENT FINDINGS

Dermcidin has recently been shown to act as a survival/proliferation factor in hepatoma and prostate cancer cell lines. Recent studies suggest that the Y-P30 subunit of the dermcidin polypeptide offers a survival advantage in such cancer cells. Nevertheless, the relevance of Y-P30 to cancer growth in vivo, and mechanisms of action remain unknown. In mice, tumour cells appear to glycosylate the Y-P30 subunit, transforming it into a potent skeletal muscle proteolysis-inducing factor. Recent work has described a receptor and signal transduction pathways for murine glycosylated proteolysis-inducing factor. The absence of classical N-glycosylation sites in the human proteolysis-inducing factor peptide and the lack of specific tools for the detection of the key carbohydrate moieties conferring the proteolysis-inducing activity, however, remain barriers to confirming glycosylated proteolysis-inducing factor as a pro-cachectic factor in humans.

SUMMARY

There is a growing body of evidence illustrating dermcidin as an oncogene and Y-P30 as a survival factor. The biology of murine proteolysis-inducing factor as a pro-cachectic factor continues to evolve; however, its role in human biology remains speculative.

Is There a Human Homologue to the Murine Proteolysis-Inducing Factor?

PURPOSE

A tumor-derived proteolysis-inducing factor (PIF) is suggested to be a potent catabolic factor in skeletal muscle of mice and humans. We aimed to establish the clinical significance of PIF in cancer patients and to elucidate its structural features.

EXPERIMENTAL DESIGN

PIF was detected in human urine using a monoclonal antibody (mAb) and related to clinical outcomes. PIF immunoaffinity-purified using the mAb was purified/separated using reverse-phase high-performance liquid chromatography and two-dimensional electrophoresis. Ten human cancer cell lines were tested for expression of mRNA encoding PIF core peptide.

RESULTS

PIF immunoreactivity was present in 160 of 262 patients with advanced cancers of the lung, esophagus/stomach, and other organs. In a Kaplan-Meier survival analysis of 181 lung cancer patients, PIF was unrelated to survival; PIF status was also unrelated to skeletal muscle loss confirmed by computed tomography imaging. PIF was seen in 16 of 24 patients with chronic heart failure and thus is not exclusive to malignant disease. In-gel digestion and mass spectrometric analysis of immunoaffinity purified PIF from cancer patients consistently identified human albumin and immunoglobulins. We showed nonspecific binding of purified albumin and immunoglobulins to the anti-PIF mAb, which is thus not a useful tool for PIF detection or purification in humans. Finally, the human PIF core peptide was detected in human cancer cell lines using reverse transcription-PCR and nucleotide sequencing; however, none of the amplified products had a site for the glycosylation critical to the proteolysis-inducing activity of murine PIF.

CONCLUSIONS

A putative human homologue of murine PIF and its role in human cancer cachexia cannot be verified.

Dermcidin expression confers a survival advantage in prostate cancer cells subjected to oxidative stress or hypoxia

BACKGROUND

Dermcidin (DCD) is a candidate survival gene in breast cancer. DCD gene expression has been identified in prostate cancer cell lines and primary prostate cancer tissue. The DCD protein is composed of proteolysis-inducing factor-core peptide (PIF-CP) and the skin antimicrobial DCD-1. The aim of this work was to: (i) establish if the DCD gene confers resistance of prostate cancer cells to hypoxia and oxidative stress; (ii) identify the component of the gene transcript responsible for this effect.

METHODS

Site-directed mutagenesis was used to create mutant DCD vectors. PC-3M prostate cancer cells were stably transfected with pcDNA3.1+ vectors encoding the entire DCD cDNA, mutant DCD vectors, or a control empty vector. Oxidative stress was produced using menadione, glucose oxidase, or hydrogen peroxide. Cell hypoxia was induced by incubation at 0.2% oxygen.

RESULTS

Comparison of cell growth showed a 54.5% relative-proliferative advantage for the DCD-transfected PC-3M cells compared with sham-transfected cells after 8 days of cell growth (P = 0.03). Overexpression of DCD provided upto 36% absolute survival advantage over sham-transfected cells following induction of oxidative stress or hypoxia (P = 0.004). On exposure to hypoxia or oxidative stress PC-3M cells overexpressing the entire DCD gene had upto 42% survival advantage over those transfectants lacking the PIF-CP sequence (P = 0.004).

CONCLUSIONS

DCD and PIF-CP are proliferation and survival factors in prostate cancer cells subjected to stressors found in the prostate cancer microenvironment. Thus, DCD and specifically PIF-CP are potential targets for the treatment of prostate cancer.

Inhibition of secreted phospholipase A2 by neuron survival and anti-inflammatory peptide CHEC-9

BACKGROUND

The nonapeptide CHEC-9 (CHEASAAQC), a putative inhibitor of secreted phospholipase A2 (sPLA2), has been shown previously to inhibit neuron death and aspects of the inflammatory response following systemic treatment of rats with cerebral cortex lesions. In this study, the properties of CHEC-9 inhibition of sPLA2 enzymes were investigated, using a venom-derived sPLA2 group I and the plasma of rats and humans as the sources of enzyme activity. The results highlight the advantages of inhibitors with uncompetitive properties for inflammatory disorders including those resulting in degeneration of neurons.

METHODS

Samples of enzyme and plasma were reacted with 1-Palmitoyl-2-Pyrenedecanoyl Phosphatidylcholine, a sPLA2 substrate that forms phospholipid vesicles in aqueous solutions. Some of the plasma samples were collected from restrained peptide-treated rats in order to confirm the validity of the in vitro assays for extrapolation to in vivo effects of the peptide. The enzyme reactions were analyzed in terms of well-studied relationships between the degree of inhibition and the concentrations of different reactants. We also examined interactions between different components of the reaction mixture on native polyacrylamide gels.

RESULTS

In all cases, the peptide showed the properties of an uncompetitive (or anti-competitive) enzyme inhibitor with Ki values less than 100 nanomolar. The electrophoresis experiments suggested CHEC-9 modifies the binding properties of the enzyme only in the presence of substrate, consistent with its classification as an uncompetitive inhibitor. Both the in vitro observations and the analysis of plasma samples from restrained rats injected with peptide suggest the efficacy of the peptide increases under conditions of high enzyme activity.

CONCLUSION

Modeling studies by others have shown that uncompetitive inhibitors may be optimal for enzyme inhibition therapy because, unlike competitive inhibitors, they are not rendered ineffective by the accumulation of unmodified substrate. Such conditions likely apply to several instances of neuroinflammation where there are cascading increases in sPLA2s and their substrates, both systemically and in the CNS. Thus, the present results may explain the efficacy of CHEC-9 in vivo.