The C-terminal 26-residue peptide of serpin A1 stimulates proliferation of breast and liver cancer cells: role of protein kinase C and CD47

Retro-Inverso Collagen Modulator Peptide Derived from Serpin A1 with Enhanced Stability and Activity In Vitro

The rising demand for novel cosmeceutical ingredients has highlighted peptides as a significant category. Based on the collagen turnover modulation properties of SA1-III, a decapeptide derived from a serine protease inhibitor (serpin A1), this study focused on designing shorter, second-generation peptides endowed with improved properties. A tetrapeptide candidate was further modified employing the retro-inverso approach that uses d-amino acids aiming to enhance peptide stability against dermal enzymes. Surprisingly, the modified peptide AAT11RI displayed notably high activity in vitro, as compared to its precursors, and suggested a mode of action based on the inhibition of collagen degradation. It is worth noting that AAT11RI showcases stability against dermal enzymes contained in human skin homogenates due to its rationally designed structure that hampers recognition by most proteases. The rational approach we embraced in this study underscored the added value of substantiated claims in the design of new cosmeceutical ingredients, representing a rarity in the field.

CD47 Promotes Human Glioblastoma Invasion Through Activation of the PI3K/Akt Pathway

Cluster of differentiation 47 (CD47) overexpression is common in various malignancies. This study investigated whether CD47 promotes human glioblastoma invasion and, if so, the underlying mechanisms involved. CD47 expression was found to be stronger in tissues of patients with glioblastoma and in various cancer cell lines than in normal controls. CD47 downregulation via siRNA suppressed invasion in vitro, whereas CD47 overexpression through plasmid transfection exerted the opposite effect. However, overexpression or knocking down of CD47 had no effect on cell proliferation. Moreover, CD47 expression was related to Akt phosphorylation at the cellular molecular level. Suppression of Akt with a specific inhibitor impaired the invasion ability of CD47-overexpressing cells, indicating that stimulation of the PI3K/Akt pathway served as the downstream regulator of CD47-triggered invasion. These results suggest that CD47 might be a useful predictor of poor prognosis and metastasis and a potential target for treating glioblastomas.

From Normal Skin to Squamous Cell Carcinoma: A Quest for Novel Biomarkers

Squamous cells carcinoma (SCC) is the second most frequent of the keratinocyte-derived malignancies after basal cell carcinoma and is associated with a significant psychosocial and economic burden for both the patient himself and society. Reported risk factors for the malignant transformation of keratinocytes and development of SCC include ultraviolet light exposure, followed by chronic scarring and inflammation, exposure to chemical compounds (arsenic, insecticides, and pesticides), and immune-suppression. Despite various available treatment methods and recent advances in noninvasive or minimal invasive diagnostic techniques, the risk recurrence and metastasis are far from being negligible, even in patients with negative histological margins and lymph nodes. Analyzing normal, dysplastic, and malignant keratinocyte proteome holds special promise for novel biomarker discovery in SCC that could be used in the future for early detection, risk assessment, tumor monitoring, and development of targeted therapeutic strategies.

Serpin A1 C-Terminal Peptides as Collagen Turnover Modulators

The modulation of collagen turnover can be a relevant pharmacological target in the context of treating either pathological or pathophysiological conditions, such as collagen-related diseases and skin aging. Our recent work has focused on the search for short-chain peptides as lead compounds for further development of compounds that enhance the production of type I collagen. In this study we selected and synthesized overlapping peptides of the C-terminal portion of serpin A1 (residues 393-418), the impact of which on collagen production has been reported previously, in order to identify shorter and still active fragments and to provide insight on the mechanisms involved. The biological activity of each fragment was evaluated with cultured normal human dermal fibroblasts, and changes in the amounts of collagen were monitored in collected culture media by a sandwich ELISA technique developed in house. Interestingly, we identified a decapeptide, termed SA1-III (Ac-MGKVVNPTQK-NH2 ), as a promising candidate for our purposes; it is able to induce a significant increase in type I collagen levels in the culture medium of treated cells at micromolar concentrations.

Antitumor activity of pamidronate in breast cancer cells transformed by low doses of α-particles and estrogen in vitro

Human breast cancer is a major cause of global morbidity and mortality in women and it is a process that involves numerous molecular and cellular alterations attributed to environmental substances and agents such as hormones. Bisphosphonates, such as pamidronate, are potent antiresorptive drugs used to the treatment of metabolic bone disease, exerting anti-proliferative, anti-migratory and apoptotic effects. The aim of this study was to evaluate gene and protein expression involved in these processes. An in vitro model was developed with the MCF-10F immortalized breast epithelial cell line exposed to low radiation doses of high LET (linear energy transfer) α-particles (150 keV/µm) and cultured in the presence of 17β-estradiol (estrogen). This model consisted of the following cell lines: i) MCF-10F, normal; ii) Alpha3, non-malignant; iii) Alpha5, pre-tumorigenic, and iv) Tumor2, derived from Alpha5 injected into the nude mice. Our previous results have shown that Alpha5 and Tumor2 increased cell proliferation, anchorage independency, invasive capabilities and tumor formation in nude mice in comparison to control. Expression of the gene (RT-qPCR) and protein (western blotting, flow cyto-metry) was measured. The results indicated that pamidronate decreased invasion, migration and Rho-A, c-Ha-ras, p53, Serpin-1, Caveolin-1, Bcl-xL and NFκB gene and protein expression. Thus, it seems that pamidronate may impinge upon cellular proliferation, invasion, metastasis and apoptosis and it may exert antitumor activity in breast cancer cells transformed by low doses of α-particles and estrogen in vitro.

iTRAQ-based quantitative proteome and phosphoprotein characterization reveals the central metabolism changes involved in wheat grain development

BACKGROUND

Wheat (Triticum aestivum L.) is an economically important grain crop. Two-dimensional gel-based approaches are limited by the low identification rate of proteins and lack of accurate protein quantitation. The recently developed isobaric tag for relative and absolute quantitation (iTRAQ) method allows sensitive and accurate protein quantification. Here, we performed the first iTRAQ-based quantitative proteome and phosphorylated proteins analyses during wheat grain development.

RESULTS

The proteome profiles and phosphoprotein characterization of the metabolic proteins during grain development of the elite Chinese bread wheat cultivar Yanyou 361 were studied using the iTRAQ-based quantitative proteome approach, TiO2 microcolumns, and liquid chromatography-tandem mass spectrometry (LC-MS/MS). Among 1,146 non-redundant proteins identified, 421 showed at least 2-fold differences in abundance, and they were identified as differentially expressed proteins (DEPs), including 256 upregulated and 165 downregulated proteins. Of the 421 DEPs, six protein expression patterns were identified, most of which were up, down, and up-down expression patterns. The 421 DEPs were classified into nine functional categories mainly involved in different metabolic processes and located in the membrane and cytoplasm. Hierarchical clustering analysis indicated that the DEPs involved in starch biosynthesis, storage proteins, and defense/stress-related proteins significantly accumulated at the late grain development stages, while those related to protein synthesis/assembly/degradation and photosynthesis showed an opposite expression model during grain development. Quantitative real-time polymerase chain reaction (qRT-PCR) analysis of 12 representative genes encoding different metabolic proteins showed certain transcriptional and translational expression differences during grain development. Phosphorylated proteins analyses demonstrated that 23 DEPs such as AGPase, sucrose synthase, Hsp90, and serpins were phosphorylated in the developing grains and were mainly involved in starch biosynthesis and stress/defense.

CONCLUSIONS

Our results revealed a complex quantitative proteome and phosphorylation profile during wheat grain development. Numerous DEPs are involved in grain starch and protein syntheses as well as adverse defense, which set an important basis for wheat yield and quality. Particularly, some key DEPs involved in starch biosynthesis and stress/defense were phosphorylated, suggesting their roles in wheat grain development.

Deficits in cerebellar granule cell development and social interactions in CD47 knockout mice

CD47 is involved in neurite differentiation in cultured neurons, but the function of CD47 in brain development is largely unknown. We determined that CD47 mRNA was robustly expressed in the developing cerebellum, especially in granule cells. CD47 protein was mainly expressed in the inner layer of the external granule layer (EGL), molecular layer, and internal granule layer (IGL), where granule cells individually become postmitotic and migrate, leading to neurite fasciculation. At postnatal day 8 (P8), CD47 knockout mice exhibited an increased number of proliferating granule cells in the EGL, whereas the CD47 agonist peptide 4N1K increased the number of postmitotic cells in primary granule cells. Knocking out the CD47 gene and anti-CD47 antibody impaired the radial migration of granule cells from the EGL to the IGL individually in mice and slice cultures. In primary granule cells, knocking out CD47 reduced the number of axonal collaterals and dendritic branches; by contrast, overexpressing CD47 or 4N1K treatment increased the axonal length and numbers of axonal collaterals and dendritic branches. Furthermore, the length of the fissure between Lobules VI and VII was decreased in CD47 knockout mice at P21 and at 14 wk after birth. Lastly, CD47 knockout mice exhibited increased social interaction at P21 and depressive-like behaviors at 10 wk after birth. Our study revealed that the cell adhesion molecule CD47 participates in multiple phases of granule cell development, including proliferation, migration, and neurite differentiation implying that aberrations of CD47 are risk factors that cause abnormalities in cerebellar development and atypical behaviors.

Serpin peptidase inhibitor clade A member 1 is a biomarker of poor prognosis in gastric cancer

Background:

In a previous study, we reported that serpin peptidase inhibitor clade A member 1 (serpinA1) is upregulated in Snail-overexpressing gastric cancer. Although serpinA1 has been studied in several types of cancer, little is known about its roles and mechanisms of action. In this study, we examined the role of serpinA1 in the migration and invasion of gastric cancers and determined its underlying mechanism.

Methods:

Expression levels were assessed by western blot analyses and real-time PCR. Snail binding to serpinA1 promoter was analysed by chromatin immunoprecipitation (ChIP) assays. The roles of serpinA1 were studied using cell invasion and migration assays. In addition, the clinicopathologic and prognostic significance of serpinA1 expression were validated in 400 gastric cancer patients using immunohistochemical analysis.

Results:

Overexpression of Snail resulted in upregulation of serpinA1 in gastric cancer cell lines, AGS and MKN45, whereas knockdown of Snail inhibited serpinA1 expression. Chromatin immunoprecipitation analysis showed that overexpression of Snail increased Snail recruitment to the serpinA1 promoter. Overexpression of serpinA1 increased the migration and invasion of gastric cancer cells, whereas knockdown of serpinA1 decreased invasion and migration. Moreover, serpinA1 increased mRNA levels and release of metalloproteinase-8 in gastric cancer cells. Serpin peptidase inhibitor clade A member 1 was observed in the cytoplasm of tumour cells and the stroma by immunohistochemistry. Enhanced serpinA1 expression was significantly associated with increased tumour size, advanced T stage, perineural invasion, lymphovascular invasion, lymph node metastases, and shorter overall survival.

Conclusions:

Serpin peptidase inhibitor clade A member 1 induces the invasion and migration of gastric cancer cells and its expression is associated with the progression of gastric cancer. These results may provide a potential target to prevent invasion and metastasis in gastric cancer.

Intravenous delivery of siRNA targeting CD47 effectively inhibits melanoma tumor growth and lung metastasis

CD47 is a "self marker" that is usually overexpressed on the surface of cancer cells to enable them to escape immunosurveillance. Recognition of CD47 by its receptor, signal regulatory protein α (SIRPα), which is expressed in the macrophages, inhibits phagocytic destruction of cancer cells by the macrophages. In this study, we have first shown that clinical isolates of human melanoma significantly upregulate CD47, possibly as a mechanism to defend themselves against the macrophages. We then exploited RNA interference (RNAi) technology to test the hypothesis that knocking down CD47 in the tumor cells will render them targets for macrophage destruction; hence, creating a novel anti-cancer therapy. Anti-CD47 siRNA was encapsulated in a liposome-protamine-hyaluronic acid (LPH) nanoparticle (NP) formulation to address the challenge of targeted delivery of siRNA-based therapeutics in vivo. Efficient silencing of CD47 in tumor tissues with systemic administration of LPH(CD47) also significantly inhibited the growth of melanoma tumors. In a lung metastasis model, LPH(CD47) efficiently inhibited lung metastasis to about 27% of the untreated control. Moreover, no hematopoietic toxicity was observed in the animals that received multiple doses of LPH(CD47). Our findings indicate CD47 as a potential prognostic marker for melanoma development as well as a target for therapeutic intervention with RNAi-based nanomedicines.

Serpin peptidase inhibitor clade A member 1 (SerpinA1) is a novel biomarker for progression of cutaneous squamous cell carcinoma

The incidence of keratinocyte-derived nonmelanoma skin cancers is increasing worldwide because of cumulative recreational exposure to sunlight. At present, no specific molecular markers are available for assessing the progression of premalignant actinic keratoses to invasive cutaneous squamous cell carcinoma (SCC). We examined the role of the Serpin family in skin SCCs. Expression profiling of cutaneous SCC cell lines (n = 8) revealed up-regulation of SerpinA1 compared with normal epidermal keratinocytes (n = 5). Analysis with quantitative RT-PCR showed that the mean level of SerpinA1 mRNA was markedly up-regulated in cutaneous SCC cell lines (n = 8) compared with in normal keratinocytes. SerpinA1 production by SCC cells was dependent on p38 mitogen-activated protein kinase activity and was up-regulated by epidermal growth factor, tumor necrosis factor-α, interferon-γ, and IL-1β. Immunostaining of tissue arrays with 148 human tissue samples revealed tumor cell-associated expression of SerpinA1 in 19 of 36 actinic keratoses, 22 of 29 Bowen's disease samples, 67 of 71 sporadic SCCs, and all 12 recessive dystrophic epidermolysis bullosa-associated SCCs examined. Moreover, tumor cell-associated SerpinA1 staining was detected in all chemically induced mouse skin SCCs studied (n = 17). Overexpression of SerpinA1 mRNA was also detected by quantitative RT-PCR in chemically induced mouse skin SCCs (n = 14) compared with control tissues (n = 14). These data identify SerpinA1 as a novel tumor cell-associated biomarker for progression of cutaneous SCCs.

Activation of CD47 receptors causes proliferation of human astrocytoma but not normal astrocytes via an Akt-dependent pathway

CD47 is a membrane receptor that plays pivotal roles in many pathophysiological processes, including infection, inflammation, cell spreading, proliferation, and apoptosis. We show that activation of CD47 increases proliferation of human U87 and U373 astrocytoma cells but not normal astrocytes. CD47 function-blocking antibodies inhibit proliferation of untreated U87 and U373 cells but not normal astrocytes, suggesting that CD47 may be constitutively activated in astrocytoma. CD47 expression levels were similar in our three cell types. CD47 couples to G-proteins in astrocytes and astrocytoma and especially to the Gβγ dimer. Downstream signaling following CD47 activation involves Gβγ dimer-dependent activation of the PI3K/Akt pathway in astrocytoma cells but not in normal astrocytes. This pathway is known to be deregulated in astrocytoma, leading to cell proliferation and enhanced survival signals. Putative PLIC-1 interaction with CD47 in astrocytoma cells but not astrocytes may contribute to the proliferative effect observed upon activation of CD47. Our data indicate that CD47 receptors have a stimulatory role in cell proliferation and demonstrate for the first time that CD47 signals via the PI3K/Akt pathway in cancerous cells but not normal cells.

Differential interactions of thrombospondin-1, -2, and -4 with CD47 and effects on cGMP signaling and ischemic injury responses

Thrombospondin-1 regulates nitric oxide (NO) signaling in vascular cells via CD47. Because CD47 binding motifs are conserved in the C-terminal signature domains of all five thrombospondins and indirect evidence has implied CD47 interactions with other family members, we compared activities of recombinant signature domains of thrombospondin-1, -2, and -4 to interact with CD47 and modulate cGMP signaling. Signature domains of thrombospondin-2 and -4 were less active than that of thrombospondin-1 for inhibiting binding of radiolabeled signature domain of thrombospondin-1 or SIRPalpha (signal-regulatory protein) to cells expressing CD47. Consistent with this binding selectivity, the signature domain of thrombospondin-1 was more potent than those of thrombospondin-2 or -4 for inhibiting NO-stimulated cGMP synthesis in vascular smooth muscle cells and downstream effects on cell adhesion. In contrast to thrombospondin-1- and CD47-null cells, primary vascular cells from thrombospondin-2-null mice lack enhanced basal and NO-stimulated cGMP signaling. Effects of endogenous thrombospondin-2 on NO/cGMP signaling could be detected only in thrombospondin-1-null cells. Furthermore, tissue survival of ischemic injury and acute recovery of blood flow in thrombospondin-2-nulls resembles that of wild type mice. Therefore, thrombospondin-1 is the dominant regulator of NO/cGMP signaling via CD47, and its limiting role in acute ischemic injury responses is not shared by thrombospondin-2.

Comparison of the effects of serpin A1, a recombinant serpin A1-IGF chimera and serpin A1 C-terminal peptide on wound healing

Serpin A1 (alpha1-antitrypsin, alpha1-proteinase inhibitor), a potent neutrophil elastase inhibitor, has therapeutic potential as a wound-healing agent. We compared the in vitro wound-healing action of serpin A1-IGF, a recombinant fusion protein of serpin A1(M351E-M358L) and insulin-like growth factor I with that observed in the presence of natural serpin A1 or A1-C26, the synthetic C-terminal 26 residue peptide of serpin A1, previously shown to have mitogenic and antiviral activities. All agents reduced wound sizes in monolayers of the kidney epithelial cell line LLC-PK1 and in primary cultures of human skin fibroblasts. Wound reduction in primary human keratinocytes was only observed with the serpin A1-IGF chimera. None of the factors stimulated cell proliferation using a colorimetric assay, with the exception of the serpin A1-IGF chimera, which caused a significant increase of cell proliferation and thymidine incorporation in human skin fibroblasts. However, wound healing by the A1-IGF chimera was reduced in keratinocytes in the presence of mitomycin C, suggesting a role of cell proliferation in wound reduction. The hydrophobic A1-C26 peptide significantly increased the production of collagen I in skin fibroblasts, an appealing asset for skin care applications.

Serpin A1 and CD91 as host instruments against HIV-1 infection: are extracellular antiviral peptides acting as intracellular messengers?

Serpin A1 (alpha1-antitrypsin, alpha1-proteinase inhibitor) has been shown to be a non-cytolytic antiviral factor present in blood and effective against HIV infection. The best known physiological role of serpin A1 is to inhibit neutrophil elastase, a proteinase which is secreted by neutrophils at sites of infection and inflammation. Decreased HIV-infectivity is associated with decreased density of membrane-associated elastase. The enzyme may facilitate binding of the HIV membrane protein gp120 to host cells, and it specifically cleaves SDF-1, the physiological ligand of the HIV-1 co-receptor CXCR4. It has been suggested that one of the actions of serpin A1 as antiviral agent is to reduce HIV infectivity, and this property could be due to elastase inhibition. However, the most dramatic effect of serpin A1 is inhibition of HIV production. In vitro experiments indicate that the C-terminal peptide of serpin A1, produced during the formation of the complex of serpin with serine proteinases, may be responsible for the inhibition of HIV-1 expression in infected cells. This peptide, an integral part of the serpin-enzyme complex, is internalized by several scavenger receptors. Peptides corresponding to the C-terminal section of serpin A1 inhibit HIV-1 long-terminal-repeat-driven transcription and interact with nuclear proteins, such as alpha1-fetoprotein transcription factor. LDL-receptor-related protein 1 (LRP1/CD91), the best known receptor for serpin-enzyme complexes, is up-regulated in monocytes of HIV-1-infected true non-progressors. CD91 could be one of the major players in host resistance against HIV-1. It has the capacity of internalizing antiviral peptides such as serpin C-terminal fragments and alpha-defensins, and is at the same time the receptor for heat-shock proteins in antigen-presenting cells, in which chaperoned viral peptides could lead to the induction of cytotoxic T-cell responses.

The C-terminal 26-residue peptide of serpin A1 is an inhibitor of HIV-1

Serpin A1 (alpha1-proteinase inhibitor) inhibits human immunodeficiency virus 1 (HIV-1) production by mechanisms which remain to be elucidated. The complex formation of serpin A1 with proteinases eliminates the proteolytic activity and generates a fragment corresponding to the serpin C-terminal 36-residue peptide. Here, we show that the C-terminal 26-residue peptide of serpin A1 (A1-C26) inhibits HIV-long terminal repeat (LTR)-driven transcription in epithelial cells transfected with HIV-1 LTR promoter-driven genes. A1-C26 increased STAT1 phosphorylation and strongly reduced viral expression in a monocytic cell line infected with HIV-1 NL4-3. This reduction of expression was also observed in HIV-1 infected, PHA-activated peripheral blood mononuclear cells. In HIV-1 infected cells, the inhibitory activity of HIV-1 caused by B9-C23 and C1-C26, the A1-C26 homologues corresponding to the C-terminal sections of serpin B9 and serpin C1, was much lower than that obtained with A1-C26. These serpin peptides represent a novel class of antiviral agents.

Mechanism of synergy between T cell signals and C8-substituted guanine nucleosides in humoral immunity: B lymphotropic cytokines induce responsiveness to 8-mercaptoguanosine

B lymphocytes require a source of T cell-like help to produce antibody to T cell-dependent antigens. T cell-derived lymphokines and C8-substituted guanine ribonucleosides (such as 8-mercaptoguanosine; 8MGuo) are effective sources of such T cell-like help. Addition of T cell-derived lymphokines to antigen-activated B cells together with 8MGuo results in synergistic B cell differentiation, amplifying the sum of the individual responses twofold to four-fold. Lymphokine activity is required at initiation of culture for optimal synergy with 8MGuo, whereas the nucleoside can be added up to 48 hr after the lymphokines with full synergy. 8MGuo provides a perceived T cell-like differentiation signal to B cells from immunodeficient xid mice, thereby distinguishing a subset of Lyb-5- nucleoside-responsive B cells from those activated by soluble anti-mu followed by B cell stimulatory factor-1, interleukin 1, and B cell differentiation factors, which are Lyb-5+. Moreover, at least a subset of the B cells recruited by the synergistic interaction of lymphokines and nucleoside is distinct from that responsive to 8MGuo + antigen, insofar as Sephadex G-10 nonadherent xid B cells fail to respond to either 8MGuo or lymphokines alone, but do respond to the combination. A distinct subpopulation can also be demonstrated among normal B cells by limiting dilution analysis in which the precursor frequency of antigen-reactive B cells in the presence of lymphokines or nucleoside alone increases substantially when both agents are present together. In concert with the kinetic data, these observations suggest that synergy derives at least in part from the ability of lymphokines to induce one or more elements the absence of which limits the capacity of a distinct B cell subpopulation to respond to 8MGuo.