Effects of the Bowman-Birk inhibitor on growth, invasion, and clonogenic survival of human prostate epithelial cells and prostate cancer cells

Bowman-Birk Inhibitors: Insights into Family of Multifunctional Proteins and Peptides with Potential Therapeutical Applications

Bowman-Birk inhibitors (BBIs) are found primarily in seeds of legumes and in cereal grains. These canonical inhibitors share a highly conserved nine-amino acids binding loop motif CTP1SXPPXC (where P1 is the inhibitory active site, while X stands for various amino acids). They are natural controllers of plants' endogenous proteases, but they are also inhibitors of exogenous proteases present in microbials and insects. They are considered as plants' protective agents, as their elevated levels are observed during injury, presence of pathogens, or abiotic stress, i.a. Similar properties are observed for peptides isolated from amphibians' skin containing 11-amino acids disulfide-bridged loop CWTP1SXPPXPC. They are classified as Bowman-Birk like trypsin inhibitors (BBLTIs). These inhibitors are resistant to proteolysis and not toxic, and they are reported to be beneficial in the treatment of various pathological states. In this review, we summarize up-to-date research results regarding BBIs' and BBLTIs' inhibitory activity, immunomodulatory and anti-inflammatory activity, antimicrobial and insecticidal strength, as well as chemopreventive properties.

Identification and Target-Modification of SL-BBI: A Novel Bowman-Birk Type Trypsin Inhibitor from Sylvirana latouchii

The peptides from the ranacyclin family share similar active disulphide loop with plant-derived Bowman-Birk type inhibitors, some of which have the dual activities of trypsin inhibition and antimicrobial. Herein, a novel Bowman-Birk type trypsin inhibitor of the ranacyclin family was identified from the skin secretion of broad-folded frog (Sylvirana latouchii) by molecular cloning method and named as SL-BBI. After chemical synthesis, it was proved to be a potent inhibitor of trypsin with a Ki value of 230.5 nM and showed weak antimicrobial activity against tested microorganisms. Modified analogue K-SL maintains the original inhibitory activity with a Ki value of 77.27 nM while enhancing the antimicrobial activity. After the substitution of active P1 site to phenylalanine and P2' site to isoleucine, F-SL regenerated its inhibitory activity on chymotrypsin with a Ki value of 309.3 nM and exhibited antiproliferative effects on PC-3, MCF-7 and a series of non-small cell lung cancer cell lines without cell membrane damage. The affinity of F-SL for the β subunits in the yeast 20S proteasome showed by molecular docking simulations enriched the understanding of the possible action mode of Bowman-Birk type inhibitors. Further mechanistic studies have shown that F-SL can activate caspase 3/7 in H157 cells and induce apoptosis, which means it has the potential to become an anticancer agent.

Overexpression of the bioactive lunasin peptide in soybean and evaluation of its anti-inflammatory and anti-cancer activities in vitro

Lunasin, a bioactive peptide with a variety of physiological functions, was overexpressed in soybean to generate a transgenic soybean. Polymerase chain reaction (PCR) analysis suggested that lunasin was successfully inserted into the soybean genome, and three transgenic lines, L12, L43, and L45, were selected for further study. Lunasin expression was characterized in the lines by Western blot and ultra-performance liquid chromatography with tandem mass spectrometry. Enzyme-linked immunosorbent assay showed that lunasin content in L12, L43, and L45 lines was 1.47 mg g-1, 1.32 mg g-1 and 1.98 mg g-1, respectively; these values were significantly higher than that in wild-type soybean (0.94 mg g-1). Lunasin enrichments from transgenic soybean (LET) exhibited stronger DPPH, ABTS+, and oxygen radical scavenging activity than lunasin enrichments from wild-type soybean (LEW). Further, LET presented superior anti-inflammatory activity on lipopolysaccharide-induced macrophage cells compared to LEW, and it significantly suppressed the release of nitric oxide (NO) and pro-inflammatory cytokines including interleukin-1 and -6. Moreover, LET showed higher anti-proliferation activity on MDA-MB-231 cells than LEW. Immunofluorescence staining showed that LET could internalize into NIH-3T3 cells, and localize in the nucleus. In conclusion, it is feasible and efficient to produce lunasin through a transgenic soybean expression system. Lunasin overexpressing soybean could be consumed as a functional food in the diets of patients with cancer and obesity in the future.

Biotechnological, biomedical, and agronomical applications of plant protease inhibitors with high stability: A systematic review

Protease inhibitors (PIs) are regulatory proteins found in numerous animal tissues and fluids, plants, and microorganisms that reduce and inhibit the exacerbated and uncontrolled activity of the target proteases. Specific PIs are also effective tools for inactivating proteases involved in human diseases like arthritis, pancreatitis, hepatitis, cancer, AIDS, thrombosis, emphysema, hypertension, and muscular dystrophy among others. Plant PIs-small peptides with a high content of cystine residues in disulfide bridges-possess a remarkable resistance to heat treatment and a high stability against shifts in pH, denaturing agents, ionic strength, and proteolysis. In recent years, novel biologic activities have been reported for plant PIs, including antimicrobial, anticoagulant, antioxidant action plus inhibition of tumor-cell growth; thus pointing to possible applications in medicine, agriculture, and biotechnology. In this review, we provide a comparative overview of plant-PIs classifying them in four groups according of their thermal and pH stability (high stability and hyperstable -to temperature and to pHs-, respectively), then emphasizing the relevance of the physicochemical characteristics of these proteins for potential biotechnological and industrial applications. Finally, we analyze the biologic activities of the stable protease inhibitors previously characterized that are the most relevant to potential applications in biomedicine, the food industry, and agriculture.

Recent update on methodologies for extraction and analysis of soybean seed proteins

Soybean is one of the best sources of plant protein. Development of improved soybean cultivars through classical breeding and new biotech approaches is important to meet the growing global demand for soybeans. There is a critical need to investigate changes in protein content and profiles to ensure the safety and nutritional quality of new soybean varieties and their food products. A proteomics study begins with an optimal combination of extraction, separation and detection approaches. This review attempts to provide a summary of current updates in the methodologies used for extraction, separation and detection of protein from soybean, the basic foundations for good proteomic research. This information can be effectively used to investigate modifications in protein content and profiles in new varieties of soybeans and other crops. © 2018 Society of Chemical Industry.

Products of Early and Advanced Glycation in the Soy Milk Proteome

SCOPE

Thermal processing of soy milk kills pathogens and denatures anti-nutrition factors warranting microbiological safety, better digestibility, and longer storage. Additionally, Maillard reactions are triggered, yielding glycated proteins (Amadori/Heyns products) and a heterogeneous group of advanced glycation end-products (AGEs). These modifications alter the nutritional value, antigenicity, and digestibility of proteins. They also raise concerns about potentially toxic effects. This study aims at characterizing these modifications in proteins from different soy milk products.

METHODS AND RESULTS

Here, glycation and AGE-modification sites in the proteome of ultrahigh-temperature-treated natural soy milk, soy milk sweetened with hexose (fructose)-containing sweeteners (SSM), and sucrose as well as soy-based infant formulas (SIFs) from different manufacturers are reported for the first time. A bottom-up proteomic approach based on nano reversed-phase high-perfomance liquid chromatography-electrospray ionization-tandem mass spectrometry (nanoRP-HPLC-ESI-MS/MS) (collision-induced dissociation (CID) and electron transfer dissociation modes) identified 229 glycated peptides and 128 AGE-modified peptides resembling 53 proteins. The glycation sites are mainly derived from hexoses, whereas N^δ -carboxyethylarginine and methylglyoxal-derived hydroimidazolone are the main AGEs in soy milk.

CONCLUSION

The qualitative and quantitative data obtained here indicate that early glycation increases with harsher processing conditions (SIFs) and the addition of hexose-containing sweeteners (SSMs), whereas the latter sweeteners (but not the harsher processing) triggered more AGE modifications.

Soybean Bioactive Peptides and Their Functional Properties

Soy consumption has been associated with many potential health benefits in reducing chronic diseases such as obesity, cardiovascular disease, insulin-resistance/type II diabetes, certain type of cancers, and immune disorders. These physiological functions have been attributed to soy proteins either as intact soy protein or more commonly as functional or bioactive peptides derived from soybean processing. These findings have led to the approval of a health claim in the USA regarding the ability of soy proteins in reducing the risk for coronary heart disease and the acceptance of a health claim in Canada that soy protein can help lower cholesterol levels. Using different approaches, many soy bioactive peptides that have a variety of physiological functions such as hypolipidemic, anti-hypertensive, and anti-cancer properties, and anti-inflammatory, antioxidant, and immunomodulatory effects have been identified. Some soy peptides like lunasin and soymorphins possess more than one of these properties and play a role in the prevention of multiple chronic diseases. Overall, progress has been made in understanding the functional and bioactive components of soy. However, more studies are required to further identify their target organs, and elucidate their biological mechanisms of action in order to be potentially used as functional foods or even therapeutics for the prevention or treatment of chronic diseases.

Purification of lectin and Kunitz trypsin inhibitor from soya seeds

The search for potent and selective therapeutic agents is progressing by the study of natural compounds in plants. Plant-derived macromolecules are considered emerging therapeutic agents and an alternative to synthetic and small molecule drugs. Where it has long been known that plants possess medicinal properties, the compounds responsible for their action are in many cases still unknown: often only whole crude plant extracts or fractionated extracts are tested for the ability to inhibit common pathogens. Here, we present a fast protein liquid chromatography method for the separation of crude plant proteins. Kunitz trypsin inhibitor (KTI; 24.2 kDa) and lectin (31 kDa) were purified from Glycine max by liquid extraction followed by ion exchange column chromatography. The need for serial chromatographic separation steps has been eliminated by introducing more complex elution profiles hence reducing cost, time and improving recovery. The identity of KTI-A and lectin was confirmed by matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-ToF MS). Cell proliferation assays using B16F1 melanoma cells revealed that both KTI and the monomeric lectin retained some antiproliferative activity. This method could be useful for rapid and cost-effective purification of bioactive compounds from plant material.

Proteins in Soy Might Have a Higher Role in Cancer Prevention than Previously Expected: Soybean Protein Fractions Are More Effective MMP-9 Inhibitors Than Non-Protein Fractions, Even in Cooked Seeds

The search for anticancer MMP-9 inhibitors (MMPIs) in food products has become a major goal for research. MMPIs in soy have been related only to saponins and isoflavones, but recently, low specific protein fractions in soybeans were shown to reduce MMP-9 activity as well. The present work aimed at comparing the MMPI potential of protein fractions (P) and non-protein fractions (NP) isolated from soybean seeds, before and after soaking and cooking, mimicking dietary exposures. Reverse and substrate zymography, as well as a fluoregenic DQ gelatin assay were used to evaluate MMP-9 activities. Colon cancer cell migration and proliferation was also tested in HT29 cells. Regarding MMP-9 inhibition, proteins in soy presented IC₅₀ values 100 times lower than non-protein extracts, and remained active after cooking, suggesting that proteins may be more effective MMP-9 inhibitors than non-protein compounds. Using the determined IC₅₀ concentrations, NP fractions were able to induce higher inhibitions of HT29 cell migration and proliferation, but not through MMP-9 inhibition, whilst protein fractions were shown to specifically inhibit MMP-9 activity. Overall, our results show that protein fractions in soybeans might have a higher role in soy-related cancer prevention as MMPIs than previously expected. Being nontoxic and active at lower concentrations, the discovery of these heat-resistant specific MMPI proteins in soy can be of significant importance for cancer preventive diets, particularly considering the increasing use of soy proteins in food products and the controversy around isoflavones amongst consumers.

Brotos de linhagens genéticas de soja: avaliação das propriedades físico-químicas

Resumo Brotos de soja são vegetais de consumo direto, obtidos de grãos germinados, que são utilizados há séculos nos países orientais. Suas características nutritivas e a facilidade de produção têm chamado a atenção de consumidores do Ocidente. Sementes pequenas com alto poder germinativo e vigor são qualidades inerentes para produção de brotos. Na Embrapa, essas características têm sido contempladas no programa de melhoramento genético para obtenção de cultivares de soja especiais para o consumo humano. O objetivo deste trabalho foi produzir e caracterizar a qualidade de brotos de soja obtidos a partir das linhagens BRM09-10505, BRM10-60599 e PF133002, em comparação com a cultivar BRS 216, desenvolvida para ser utilizada como brotos ou natto. Os brotos foram produzidos em bandejas dispostas em câmara de germinação (25°C e 99% de umidade relativa). Sementes e brotos foram avaliados nos seguintes aspectos: teor de proteínas, lipídios, cinzas, isoflavonas, inibidor de tripsina Kunitz, ácido fítico, comprimento e peso dos brotos. As sementes da BRM09-10505 apresentaram 95% de poder germinativo, seguida pela BRS 216 (93%) e pelas outras linhagens (88%, em média). A germinação pela mobilização dos compostos químicos aumentou os teores de proteínas (8,96%) e de isoflavonas (56,00%) e reduziu os teores de inibidor de tripsina Kunitz (26,91%) e de ácido fítico (13,78%). A cultivar BRS 216 apresentou o maior teor de proteína nas sementes (41,96 g.100 g-1) e nos brotos (47,70 g.100 g-1). A linhagem BRM09-10505 apresentou maior teor de inibidor de tripsina nas sementes (27,56 mg IT g-1) e nos brotos (19,62 mg. IT g-1); maior concentração de isoflavonas totais nas sementes (340,10 mg.100 g-1) e nos brotos (406,38 mg.100 g-1), e menor teor de ácido fítico nos brotos (1,13 g.100 g-1). Após quatro dias de germinação, destacaram-se, quanto ao comprimento e ao peso, a linhagem BRM09-10505 (8,03 cm e 214,36 g) e a cultivar BRS 216 (7,31 cm e 140,93 g). Entre as linhagens testadas, a linhagem BRM09-10505 apresentou bom potencial para produção de brotos.

Plant Protease Inhibitors in Therapeutics-Focus on Cancer Therapy

Plants are known to have many secondary metabolites and phytochemical compounds which are highly explored at biochemical and molecular genetics level and exploited enormously in the human health care sector. However, there are other less explored small molecular weight proteins, which inhibit proteases/proteinases. Plants are good sources of protease inhibitors (PIs) which protect them against diseases, insects, pests, and herbivores. In the past, proteinaceous PIs were considered primarily as protein-degrading enzymes. Nevertheless, this view has significantly changed and PIs are now treated as very important signaling molecules in many biological activities such as inflammation, apoptosis, blood clotting and hormone processing. In recent years, PIs have been examined extensively as therapeutic agents, primarily to deal with various human cancers. Interestingly, many plant-based PIs are also found to be effective against cardiovascular diseases, osteoporosis, inflammatory diseases and neurological disorders. Several plant PIs are under further evaluation in in vitro clinical trials. Among all types of PIs, Bowman-Birk inhibitors (BBI) have been studied extensively in the treatment of many diseases, especially in the field of cancer prevention. So far, crops such as beans, potatoes, barley, squash, millet, wheat, buckwheat, groundnut, chickpea, pigeonpea, corn, and pineapple have been identified as good sources of PIs. The PI content of such foods has a significant influence on human health disorders, particularly in the regions where people mostly depend on these kind of foods. These natural PIs vary in concentration, protease specificity, heat stability, and sometimes several PIs may be present in the same species or tissue. However, it is important to carry out individual studies to identify the potential effects of each PI on human health. PIs in plants make them incredible sources to determine novel PIs with specific pharmacological and therapeutic effects due to their peculiarity and superabundance.

Selective depletion of tumour suppressors Deleted in Colorectal Cancer (DCC) and neogenin by environmental and endogenous serine proteases: linking diet and cancer

BACKGROUND

The related tumour suppressor proteins Deleted in Colorectal Cancer (DCC) and neogenin are absent or weakly expressed in many cancers, whereas their insertion into cells suppresses oncogenic behaviour. Serine proteases influence the initiation and progression of cancers although the mechanisms are unknown.

METHODS

The effects of environmental (bacterial subtilisin) and endogenous mammalian (chymotrypsin) serine proteases were examined on protein expression in fresh, normal tissue and human neuroblastoma and mammary adenocarcinoma lines. Cell proliferation and migration assays (chemoattraction and wound closure) were used to examine cell function. Cells lacking DCC were transfected with an ectopic dcc plasmid.

RESULTS

Subtilisin and chymotrypsin selectively depleted DCC and neogenin from cells at nanomolar concentrations without affecting related proteins. Cells showed reduced adherence and increased migration, but after washing they re-attached within 24 h, with recovery of protein expression. These effects are induced by chymotryptic activity as they are prevented by chymostatin and the soybean Bowman-Birk inhibitor typical of many plant protease inhibitors.

CONCLUSIONS

Bacillus subtilis, which secretes subtilisin is widely present in soil, the environment and the intestinal contents, while subtilisin itself is used in meat processing, animal feed probiotics and many household cleaning agents. With chymotrypsin present in chyme, blood and tissues, these proteases may contribute to cancer development by depleting DCC and neogenin. Blocking their activity by Bowman-Birk inhibitors may explain the protective effects of a plant diet. Our findings identify a potential non-genetic contribution to cancer cell behaviour which may explain both the association of processed meats and other factors with cancer incidence and the protection afforded by plant-rich diets, with significant implications for cancer prevention.

Bowman-Birk inhibitor concentrate suppresses experimental autoimmune neuritis via shifting macrophages from M1 to M2 subtype

BACKGROUND

In the present study, we investigated the immuno-regulatory and therapeutic effects of Bowman-Birk inhibitor concentrate (BBIC) on experimental autoimmune neuritis (EAN), an animal model of Guillain-Barré syndrome (GBS) in human.

METHODS

EAN in Lewis rats induced by inoculation with peripheral nerve myelin P0 protein peptide 180-199 (P0 peptide) was treated with BBIC at two different therapeutic regimens.

RESULTS

Our data indicated that the administration of BBIC daily orally effectively inhibited and ameliorated the clinical and pathological signs of EAN. The suppression of EAN was associated with an insufficiency of autoreactive T cells, as reflected by inhibited P0 peptide-specific mononuclear cell proliferation and decreased in CD4 and CD8T cells infiltrating into the peripheral nervous system (PNS). BBIC might mediate its therapeutic effects by shifting macrophages from M1 to M2 subtype as evidenced by increasing Arg-1, CD206 and IL-10 and inhibiting IFN-γ, TNF-α, IL-12, iNOS and CD40 expressions on macrophages as well as enhancing anti-inflammatory cytokines IL-4 and IL-10 and decreasing inflammatory cytokines, IFN-γ, TNF-α and IL-17 in the PNS.

CONCLUSION

Our results suggest that BBIC may have therapeutic potential in human GBS and other autoimmune diseases in the future.

An effective and simple procedure to isolate abundant quantities of biologically active chemopreventive Lunasin Protease Inhibitor Concentrate (LPIC) from soybean

Lunasin is a 5-kDa soybean bioactive peptide with demonstrated anti-cancer and anti-inflammatory properties. Recently, purification methods have been developed to obtain gram quantities of lunasin. However, these methods are cumbersome, time consuming and cost-prohibitive. To overcome these constrains we have developed a novel method which involves extraction of soybean flour with 30% ethanol followed by preferential precipitation of lunasin and protease inhibitors by calcium. The calcium precipitated protein fraction, which we termed as Lunasin Protease Inhibitor Concentrate (LPIC), contains three abundant proteins with molecular weights of 21, 14 and 5 kDa. This simple procedure yields 3.2g of LPIC from 100g of soybean flour and the entire isolation procedure can be completed in less than 2h. Treatment of THP-1 human monocyte cell lines with LPIC resulted in suppression of lipopolysaccharide-stimulated cytokine expression, demonstrating that the LPIC isolated by our simple procedure is biologically active.

A continuous-flow mass biosensor for the real-time dynamic analysis of protease inhibition

A flow injection analysis–quartz crystal microbalance (FIA–QCM) biosensor system was introduced for probing the dynamic interactions during protease inhibition.

Bowman-Birk protease inhibitor from Vigna unguiculata seeds enhances the action of bradykinin-related peptides

The hydrolysis of bradykinin (Bk) by different classes of proteases in plasma and tissues leads to a decrease in its half-life. Here, Bk actions on smooth muscle and in vivo cardiovascular assays in association with a protease inhibitor, Black eyed-pea trypsin and chymotrypsin inhibitor (BTCI) and also under the effect of trypsin and chymotrypsin were evaluated. Two synthetic Bk-related peptides, Bk₁ and Bk₂, were used to investigate the importance of additional C-terminal amino acid residues on serine protease activity. BTCI forms complexes with Bk and analogues at pH 5.0, 7.4 and 9.0, presenting binding constants ranging from 10³ to 10⁴ M⁻¹. Formation of BTCI-Bk complexes is probably driven by hydrophobic forces, coupled with slight conformational changes in BTCI. In vitro assays using guinea pig (Cavia porcellus) ileum showed that Bk retains the ability to induce smooth muscle contraction in the presence of BTCI. Moreover, no alteration in the inhibitory activity of BTCI in complex with Bk and analogous was observed. When the BTCI and BTCI-Bk complexes were tested in vivo, a decrease of vascular resistance and consequent hypotension and potentiating renal and aortic vasodilatation induced by Bk and Bk₂ infusions was observed. These results indicate that BTCI-Bk complexes may be a reliable strategy to act as a carrier and protective approach for Bk-related peptides against plasma serine proteases cleavage, leading to an increase in their half-life. These findings also indicate that BTCI could remain stable in some tissues to inhibit chymotrypsin or trypsin-like enzymes that cleave and inactivate bradykinin in situ.

Soybean Bowman-Birk protease inhibitor (BBI): identification of the mechanisms of BBI suppressive effect on growth of two adenocarcinoma cell lines: AGS and HT29

BACKGROUND AND AIMS

Bowman-Birk protease inhibitor (BBI) has been well known to suppress the emergence and progression of different cancers. In the present study, the mechanisms by which BBI alters cancers have been addressed. To reach this goal, the effects of BBI on proliferation of and VEGF secretion by two cell lines (AGS: gastric adenocarcinoma and HT-29: colorectal adenocarcinoma) and also BBI effect on MMP-2 and 9 synthesis/secretion by AGS cells was evaluated.

METHODS

ELISA method was used to assess VEGF concentration and gelatin zymography was used to address MMP-2 and 9 production/excretion.

RESULTS

BBI had powerful inhibitory effect on proliferation and VEGF secretion by both cell lines. In addition, inhibition of MMP-2 and MMP-9 secreted by AGS cells suggests BBI as a potent inhibitor of gastric cancer progression. On the other hand, the results indicated that inhibition of MMP-2, MMP-9 and VEGF secretion is one of the mechanisms of anti-angiogenic effect of BBI.

CONCLUSION

BBI expresses powerful suppressive effect on tumor progression of two prevalent cancers: gastric adenocarcinoma and colorectal adenocarcinoma.

Role of serine proteases in inflammation: Bowman-Birk protease inhibitor (BBI) as a potential therapy for autoimmune diseases

Serine proteases, a sub-category of the protease family, participate in various physiologic and pathologic conditions. Serine proteases are involved in different arms of the immune system and play an important role in inflammation. They have been evaluated as therapeutic targets in several inflammatory diseases. The Bowman-Birk protease inhibitor (BBI), a soybean-derived serine protease inhibitor, is resistant to temperature and acidic conditions. These characteristics make it a good candidate for oral administration, with no major side effects. In addition, the therapeutic effect of BBI has been shown in inflammatory diseases and cancer. We have demonstrated the immunoregulatory and anti-inflammatory effects of BBI in the experimental autoimmune encephalomyelitis (EAE) model of multiple sclerosis. Here we review the role of serine proteases in inflammatory diseases, with emphasis on the potential of BBI as a novel oral therapy for multiple sclerosis.

Imbibition of soybean seeds in warm water results in the release of copious amounts of Bowman-Birk protease inhibitor, a putative anticarcinogenic agent

Protease inhibitors play a protective role against pathogenic microorganisms and herbivorous insects. The two predominant protease inhibitors of soybean seeds are the Kunitz trypsin inhibitor (KTI) and Bowman-Birk protease inhibitor (BBI). In this study, we report that soybean seeds incubated in warm water release large amounts of proteins into the surrounding media. Two-dimensional gel electrophoresis analysis of the seed exudates resulted in the separation of 93 distinct protein spots out of which 90 spots were identified by LC-MS/MS. The basic 7S globulin and the BBI are the two predominant proteins found in the soybean seed exudates. In addition to 7S and 11S seed storage proteins, others known to protect the seeds against pathogens and pests including KTI, peroxidase, α-galactosidase, and endo-1.3-β-glucanase were also identified in the seed exudates. Soybean seed exudate obtained by incubating the seeds in warm water was also able to inhibit the growth of human breast cancer cell line MCF-7. Since soybean seeds release large amounts of enzymatically active BBI when immersed in warm water, our procedure could be exploited as a simplified alternative method for the preparation of BBI concentrate which is being used as a cancer chemoprotective agent.

Effects of Tepary bean (Phaseolus acutifolius) protease inhibitor and semipure lectin fractions on cancer cells

Some natural and synthetic protease inhibitors (PI), such as the Bowman-Birk PI from soybean, have anticancer effects. We previously purified and characterized a Bowman-Birk-type PI from Tepary bean (Phaseolus acutifolius) seeds (TBPI). A semipure protein fraction containing this inhibitor, when tested its in vitro effect on transformed cells, showed a differential cytotoxic effect, as well as an increase in cell attachment to culture dishes. In this article we report that lectins were responsible for the cytotoxic effect previously observed, exhibiting a differential, antiproliferative effect on nontransformed cells and on different lineages of cancer cells. Although the purified TBPI lacked cytotoxicity, it was found to be responsible for the increase in cell adhesion, decreasing culture dishes' extracellular matrix degradation, leading to a decrease of the in vitro cell invasion capacity. This effect coincided with the suppression of Matrix Metalloproteinase-9 activity. These results indicate that Tepary bean seeds contain at least 2 different groups of bioactive proteins with distinct effects on cancer cells.

Suppression of the later stages of radiation-induced carcinogenesis by antioxidant dietary formulations

We have previously reported data from a long-term carcinogenesis study indicating that dietary antioxidant supplements can suppress radiation-induced malignant lymphoma and harderian gland tumors induced by space radiations (specifically, 1 GeV/n iron ions or protons) in CBA/J mice. Two different antioxidant dietary supplements were used in these studies: a supplement containing a mixture of antioxidant agents [l-selenomethionine (SeM), N-acetyl cysteine (NAC), ascorbic acid, co-enzyme Q10, α-lipoic acid and vitamin E succinate], termed the AOX supplement, and another supplement known as Bowman-Birk Inhibitor Concentrate (BBIC). In the present report, the results from the earlier analysis of the harderian gland data from the published long-term animal study have been combined with new data derived from the same long-term animal study. In the earlier analysis, harderian glands were removed from animals exhibiting abnormalities (e.g. visibly swollen areas) around the eyes at the time of euthanasia or death in the long-term animal study. Abnormalities around the eyes were usually due to the development of tumors in the harderian glands of these mice. The new data presented here focused on the histopathological results obtained from analyses of the harderian glands of mice that did not have visible abnormalities around the eyes at the time of necropsy in the long-term animal study. In this paper, the original published data and the new data have been combined to provide a more complete evaluation of the harderian glands from animals in the long-term carcinogenesis study, with all available harderian glands from the animals processed and prepared for histopathological evaluation. The results indicate that, although dietary antioxidant supplements suppressed harderian gland tumors in a statistically significant fashion when all glands were analyzed, the antioxidant diets were less effective at suppressing the incidence of all harderian gland tumors than they were at suppressing the incidence of large harderian gland tumors (>2 mm) observed at animal necropsy. These results suggest that the dietary antioxidant formulations had major suppressive effects in the later stages of radiation-induced carcinogenesis in vivo. It is hypothesized that the dietary antioxidant formulations prevented the early-stage neoplastic growths from progressing to fully developed, malignant tumors. In addition, the antioxidant dietary formulations were very effective at preventing the development of proton- or iron-ion-induced malignant tumors, because, in contrast to irradiated controls, no malignant tumors were observed in the irradiated animals maintained on either of the dietary antioxidant diets.

The role of nutraceutical proteins and peptides in apoptosis, angiogenesis, and metastasis of cancer cells

The process of carcinogenesis is complex and not easy to eliminate. It includes the initial occurrence of genetic alterations which can lead to the inactivation of tumor-suppressor genes and further accumulation of genetic alterations during tumor progression. Looking for food and food components with biological properties, collectively called nutraceuticals, that can hinder such alterations and prevent the inactivation of tumor-suppressor genes is a very promising area for cancer prevention. Proteins and peptides are one group of nutraceuticals that show potential results in preventing the different stages of cancer including initiation, promotion, and progression. In this review, we summarized current knowledge on the use of nutraceutical proteins and peptides in cancer prevention and treatment. We focused on the role of plant protease inhibitors, lactoferrin and lactoferricin, shark cartilage, plant lectins, and lunasin in the apoptosis, angiogenesis, and metastasis of cancer cells. Also included are studies on bioavailability and clinical trials conducted on these promising proteins and peptides.

Apoptosis and lysosome membrane permeabilization induction on breast cancer cells by an anticarcinogenic Bowman-Birk protease inhibitor from Vigna unguiculata seeds

In this work, we report the effects of a Bowman-Birk protease inhibitor, the Black-Eyed Pea Trypsin/Chymotrypsin Inhibitor - BTCI, purified from Vigna unguiculata seeds, on the MCF-7 breast cancer cells. The treatment of MCF-7 with 200microM BTCI for 72h induced significant reduction of the cell viability and proliferation (arrest in S and G2/M phase). These cytostatic effects were accompanied by acute morphological modifications including the alteration of the nuclear morphology, plasma membrane fragmentation, cytoplasm disorganization, presence of double-membrane vesicles, mitochondrial swelling, and an increase in the size of lysosomes. Significative DNA fragmentation, annexin-V(+) cell number increase, mitochondrial membrane potential reduction, and cytoplasm acidification were also detected. All together, these cytostatic and cytotoxic results point out to BTCI-induced apoptosis cell death associated with severe cell morphological alterations and lysosome membrane permeabilization. Our study confirms the anticarcinogenic potential of Bowman-Birk protease inhibitors and identifies BTCI as a promising tool for drug developments aimed at the treatment of breast cancer.

Induction of apoptosis in the LNCaP human prostate carcinoma cell line and prostate adenocarcinomas of SV40T antigen transgenic rats by the Bowman-Birk inhibitor

The soybean-derived serine protease inhibitor, Bowman-Birk inhibitor (BBI), has been reported as a potent chemoprevention agent against several types of tumors. The present study was undertaken to evaluate the effects of BBI on androgen-sensitive/dependent prostate cancers using a human prostate cancer cell (LNCaP) and the transgenic rats developing adenocarcinoma of the prostate (TRAP) model. Treatment of LNCaP prostate cancer cells with 500 microg/mL BBI resulted in inhibition of viability measured on WST-1 assays, with induction of connexin 43 (Cx43) and cleaved caspase-3 protein expression. Feeding of 3% roughly prepared BBI (BBIC) to TRAP from the age 3 weeks to 13 weeks resulted in significant reduction of the relative epithelial areas within the acinus and multiplicity of the adenocarcinomas in the lateral prostate lobes. Cx43- and terminal deoxynucleotidyl transferase mediated dUTP-biotin end labeling of fragmented DNA (TUNEL)-positive apoptotic cancer cells were more frequently observed in the lateral prostates treated with BBIC than in the controls. These in vivo and in vitro results suggest that BBI possesses chemopreventive activity associated with induction of Cx43 expression and apoptosis.

Bauhinia Kunitz-type proteinase inhibitors: structural characteristics and biological properties

Plant proteinase inhibitors are involved in the regulation of the activity of many proteinases and, in consequence, in biological processes driven by proteolysis. In this review, we summarize recent results on the activity of native Bauhinia inhibitors and synthetic derivatives. Structural and functional characteristics and the potential therapeutic use of these inhibitors are also discussed.

Lunasin: a novel cancer preventive seed Peptide

Cancer is one of the leading causes of deaths in the Western world. Approximately one-third of these deaths are preventable by lifestyle factors, including modification of nutritional habits. Studies have demonstrated that adequate nutrition with certain types of foods containing bioactive compounds might offer significant protection against carcinogenesis. Soybeans contain a variety of phytochemicals with demonstrated anticancer activity, including isoflavones, protease inhibitors, and more recently lunasin, a novel cancer preventive seed peptide. Initially isolated from soybean, lunasin has also been reported in barley and wheat. The purpose of this review is to summarize the most recent evidence on the possible benefits of lunasin for cancer prevention.

The biochemical and functional food properties of the bowman-birk inhibitor

The Bowman-Birk inhibitor (BBI) is a small water-soluble protein present in soybean and almost all monocotyledonous and dicotyledonous seeds. The molecular size of BBI ranges from 1,513 Da to about 20,000 Da. BBI is to seeds what alpha(1)-antitrypsin is to humans. Soy-based food products rich in BBI include soybean grits, soymilk, oilcake, soybean isolate, and soybean protein concentrate. BBI is stable within the pH range encountered in most foods, can withstand boiling water temperature for 10 min, resistant to the pH range and proteolytic enzymes of the gastrointestinal tract, bioavailable, and not allergenic. BBI reduces the proteolytic activities of trypsin, chymotrypsin, elastase, cathepsin G, and chymase, serine protease-dependent matrix metalloproteinases, urokinase protein activator, mitogen activated protein kinase, and PI3 kinase, and upregulates connexin 43 (Cx43) expression. Several studies have demonstrated the efficacy of BBI against tumor cells in vitro, animal models, and human phase IIa clinical trials. FDA considers BBI as a drug. In 1999, FDA allowed a health claim on food labels stating that a daily diet containing 25 grams of soy protein, also low in saturated fat and cholesterol, may reduce the risk of heart disease [corrected] This review highlights the biochemical and functional food properties of the Bowman-Birk inhibitor.

Chemoprevention of Rat Prostate Carcinogenesis by Soy Isoflavones and by Bowman-Birk Inhibitor

Epidemiology studies suggest that soy consumption confers protection against human prostate cancer. To identify the soy component(s) that may be responsible for this chemopreventive activity, studies were conducted to determine the influence of a soy isoflavone mixture (PTI G-2535; 45% genistein, 22% daidzein, 2% glycitein) and a soy-derived protease inhibitor (Bowman-Birk Inhibitor Concentrate; BBIC) on prostate carcinogenesis in rats. Prostate cancers were induced in male Wistar-Unilever rats by a sequential regimen of cyproterone acetate and testosterone propionate, followed by a single intravenous injection of N-methyl-N-nitrosourea (MNU) and chronic androgen stimulation. In separate studies, PTI G-2535 and BBIC were administered continuously at 0 (control), 200, or 2000 mg/kg diet, beginning 1 wk post-MNU. PTI G-2535 and BBIC both conferred modest, but statistically significant and dose-related protection against carcinogenesis in the dorsolateral+anterior prostate. These data demonstrate that both the isoflavone and protein (protease inhibitor) components of soy can inhibit prostate carcinogenesis in the rat. However, the modest individual activities of soy isoflavones and BBIC suggest that while both components may contribute to the chemopreventive activity of soy, combination administration (or exposure to whole soy) may be more effective in prostate cancer prevention than is administration of either component alone.

Evaluation of chemopreventive agents for genotoxic activity

We conducted genetic toxicity evaluations of 11 candidate chemopreventive agents with the potential for inhibiting carcinogenesis in humans at increased risk of cancer. The compounds were evaluated for bacterial mutagenesis in the Salmonella-E. coli assay, for mammalian mutagenesis in mouse lymphoma cells, for chromosome aberrations in Chinese Hamster Ovary (CHO) cells, and for micronucleus induction in mouse bone marrow. Tested agents were indole 3-carbinol (I3C), bowman-birk inhibitor concentrate (BBIC), black tea polyphenols (BTP), farnesol, geraniol, l-Se-methylselenocysteine (SeMC), 5,6-dihydro-4H-cyclopenta[1,2]-dithiol-3-thione(DC-D3T), 4'-bromoflavone, 2,5,7,8-tetramethyl-(2R-[4R,8R,12-trimethyltridecyl] chroman-6-yloxy) acetic acid (alpha-TEA), SR13668 (2,10-dicarbethoxy-6-methoxy-5,7-dihydro-indolo[2,3-b] carbazole and SR16157 (3-O-sulfamoyloxy-7alpha-methyl-21-(2-N,N-diethylaminoethoxy)-19-norpregna-1,3,5(10)-triene). All these agents, except I3C and BTP, were negative in the Salmonella-E. coli assay in the presence and absence of metabolic activation (S9). I3C and BTP induced a weak mutagenic response in the presence and absence of S9 with strains TA100 and TA98, respectively. Of the three compounds tested in the mouse lymphoma assay (I3C, BBIC, and BTP), only BTP was mutagenic in the presence of S9. In the chromosomal aberration assay, of the 8 compounds that were tested, 4'-bromoflavone elicited a positive response in the absence of S9 only, while SR16157 was positive in the presence of S9. The results with geraniol remain inconclusive. I3C, BBIC and BTP were not tested in the chromosomal aberration assay. None of the 11 agents induced micronuclei in mouse bone marrow erythrocytes.

Crystal structure of the anticarcinogenic Bowman-Birk inhibitor from snail medic (Medicago scutellata) seeds complexed with bovine trypsin

The structure of the ternary complex of the anticarcinogenic Bowman-Birk protease inhibitor purified from snail medic (Medicago scutellata) seeds (MSTI) and two molecules of bovine trypsin has been solved by X-ray diffraction analysis of single crystals to a resolution of 2.0 A. This is the highest resolution model of a ternary complex of this type currently available. The two binding loops of the MSTI differ in only one amino acid and have in both cases an arginine in position P1. The distances between the residues of the inhibitor at the binding interface and the trypsin side chains that recognize them are almost identical in the two sites. When compared to the NMR model of the uncomplexed MSTI, the inhibitor in the functional assembly with trypsin shows the largest differences in the two P2' residues. Compared with the similar ternary complex of the soybean trypsin inhibitor, this model shows very small differences in the polypeptide chain of the trypsin binding sites and its largest difference in the area between Asp 26 and His 32 of the MSTI which in the soybean inhibitor has an extra Leu inserted in position 29.

Protease inhibitors and their peptidomimetic derivatives as potential drugs

Precise spatial and temporal regulation of proteolytic activity is essential to human physiology. Modulation of protease activity with synthetic peptidomimetic inhibitors has proven to be clinically useful for treating human immunodeficiency virus (HIV) and hypertension and shows potential for medicinal application in cancer, obesity, cardiovascular, inflammatory, neurodegenerative diseases, and various infectious and parasitic diseases. Exploration of natural inhibitors and synthesis of peptidomimetic molecules has provided many promising compounds performing successfully in animal studies. Several protease inhibitors are undergoing further evaluation in human clinical trials. New research strategies are now focusing on the need for improved comprehension of protease-regulated cascades, along with precise selection of targets and improved inhibitor specificity. It remains to be seen which second generation agents will evolve into approved drugs or complementary therapies.

Lunasin: a cancer-preventive soy peptide

Lunasin is a novel, cancer-preventive peptide whose efficacy against chemical carcinogens and oncogenes has been demonstrated in mammalian cells and in a skin cancer mouse model. Isolated and characterized in soy, lunasin peptide is also documented in barley. Lunasin is found in all of the genotypes analyzed from the US soy germ plasm collection and in commercially available soy proteins. Pilot studies show that lunasin is bioavailable in mice and rats when orally ingested, opening the way for dietary administration in cancer prevention studies. Lunasin internalizes into mammalian cells within minutes of exogenous application, and localizes in the nucleus after 18 hours. It inhibits acetylation of core histones in mammalian cells. In spite of its cancer-preventive properties, lunasin does not affect the growth rate of normal and established cancer cell lines. An epigenetic mechanism of action is proposed whereby lunasin selectively kills cells being transformed or newly transformed by binding to deacetylated core histones exposed by the transformation event, disrupting the dynamics of histone acetylation-deacetylation and leading to cell death.

Oncogenicity evaluations of chemopreventive soy components in p53((+/-)) (p53 knockout) mice

Epidemiologic data suggest that soy consumption may protect against cancer induction in several tissues in humans. Although the soy components responsible for this activity remain unidentified, isoflavones (e.g., genistein) and protease inhibitors (e.g., Bowman-Birk inhibitor complex [BBIC]) demonstrate chemopreventive activity in several animal cancer models. As part of their preclinical development for cancer prevention, PTI G-2535 (a soy isoflavone mixture containing 45% genistein, 23% daidzein, and 4% glycitein) and BBIC were evaluated for oncogenicity in p53((+/-)) mice. In separate studies, groups of 25 p53((+/-)) mice/sex received daily gavage exposure to PTI G-2535 (0, 250, 1000, or 2500 mg/kg/day) or BBIC (0, 500, 1000, or 2000 mg/kg/day) for 6 months. The high doses of both PTI G-2535 and BBIC were limited by viscosity. p-Cresidine (400 mg/kg/day) served as a positive-control article in both studies. PTI G-2535 induced no gross toxicity in any animal, but did induce a dose-related suppression of body weight gain in male mice. Modest hematologic alterations and increased liver and spleen weights were seen in both sexes exposed to the isoflavone mixture. BBIC had no significant effect on body weight, food consumption, clinical pathology, or organ weights in either sex. Histopathologic evaluations demonstrated no increases in the incidence of either benign or malignant tumors in any group of p53((+/-)) mice exposed to PTI G-2535 or to BBIC. By contrast, the positive-control article, p-cresidine, induced urinary bladder cancers in both studies. Neither PTI G-2535 nor BBIC demonstrates any evidence of oncogenicity in the p53((+/-)) mouse model.

Purification and primary structure determination of two Bowman-Birk type trypsin isoinhibitors from Cratylia mollis seeds

Two Bowman-Birk type trypsin inhibitors (CmTI(1) and CmTI(2)) were purified from Cratylia mollis seeds by acetone precipitation, ion exchange, gel filtration and reverse-phase chromatography. CmTI(1) and CmTI(2), with 77 and 78 amino acid residues, respectively, were sequenced in their entirety and show a high structural similarity to Bowman-Birk inhibitors from other Leguminosae. The putative reactive sites of CmTI(1) are a lysine residue at position 22 and a tyrosine residue at position 49. Different reactive sites, as identified by their alignment with related inhibitors, were found for CmTI(2): lysine at position 22 and leucine at position 49. The dissociation constant K(i) of the complex with trypsin is 1.4 nM. The apparent molecular mass is 17 kDa without DDT and 11 kDa with reducing agent and heating.

Monoclonal Antibodies Against Soybean Bowman-Birk Inhibitor Recognize the Protease-Reactive Loops

Monoclonal antibodies against soybean Bowman-Birk protease inhibitor (BBI) have been generated and used to detect and quantify BBI in foods, soybean germplasm, and animal tissues and fluids. The purpose of this study was to determine the recognition sites of two monoclonal antibodies to BBI (mAb 238 and mAb 217) in relation to the protease-inhibitory sites of BBI. The results showed that (1) the binding of mAb 238 can be blocked by trypsin and that of mAb 217 by chymotrypsin; (2) the trypsin or chymotrypsin inhibitory activities of BBI are blocked by mAb 238 or mAb 217, respectively; and (3) mAb 238 failed to recognize a tryptic loop mutant BBI variant and mAb 217 was unable to bind a chymotryptic loop mutant BBI variant. These findings demonstrate that the epitopes recognized by mAb 238 and mAb 217 reside, at least in part, in the tryptic and chymotryptic loops of BBI, respectively.

Lunasin suppresses E1A-mediated transformation of mammalian cells but does not inhibit growth of immortalized and established cancer cell lines

Lunasin, a novel and promising chemopreventive compound isolated from soybean cotyledon, is a 43-amino acid peptide that contains a -RGD-cell adhesion motif followed by 8 aspartic acid residues at the carboxyl end and a structurally conserved helix region. We showed previously that lunasin peptide applied exogenously reduces foci formation in mouse fibroblast cells treated with chemical carcinogens and inhibits skin tumorigenesis induced by chemical carcinogens in mice when applied topically. In this study, lunasin peptide applied to cell culture suppresses foci formation in E1A-transfected mouse fibroblast NIH 3T3 cells. Within 18 h of exogenous application, lunasin internalizes into the cell and localizes in the nucleus. In an initial study of genes affected by lunasin, the peptide increases p21 protein levels fivefold in cells transfected with E1A but not in untransfected cells. In contrast to its inhibitory effects on cell transformation, lunasin has no effect on growth of imicroMortalized (nontumorigenc) and established cancer cells. This is the first report that lunasin suppresses transformation of mamicroMalian cells induced by an oncogene (E1A) in addition to chemical carcinogens.

Anticarcinogenic properties of a daidzein-rich fraction isolated from soybean

In a previous study, we demonstrated that the methanol extract of soybean powder contains an active component(s) that promotes the differentiation of HL-60 cells. Partial purification of the extract, using solvent fractionation and silica gel chromatography, produced an active fraction rich in daidzein. The daidzein-rich fraction (DRF) was evaluated for its cancer preventive potential by assessing its cytotoxic activity and effect on the expression of the transforming growth factor beta (TGF-beta) family of cytokines and their receptors. DRF appeared to exert cytotoxic activity via an apoptotic pathway as evaluated by a DNA fragmentation assay and caspase-3 induction. DRF also increased the expression of TGF-beta2, but had little effect on the expression of other members of the TGF-beta family of cytokines and their receptors, or on the expression of the vascular endothelial growth factor gene. In conclusion, the DRF isolated from the methanol extract of soybean may have the potential to prevent tumorigenesis and, therefore, deserves to undergo further evaluation of its active component(s) and in vivo evaluation for anticarcinogenic efficacy.