Chemoprevention of breast cancer by tamoxifen: risks and opportunities

Anti-hyperplastic effects of the Dacryodes edulis (Burseraceae) leaves aqueous extract on tamoxifen-induced endometrium hyperplasia on Wistar rat

OBJECTIVES

Combining tamoxifen, the most common breast cancer hormonal therapy, with natural antitumor substances may prevent its hyperplastic effects on the uterine endometrium. Dacryodes edulis (DE) is traditionally recommended for the treatment of cancerous diseases. To investigate its antiproliferative properties, the present study was designed to assess the ability of the combined administration of tamoxifen with the aqueous extract of DE leaves to inhibit the trophic effect of this hormone therapy on rat uterine endometrium without compromising its non-proliferative effect on breast tissue.

METHODS

Ovariectomized (OVX) female Wistar rats were simultaneously treated with tamoxifen (10 mg/kg) intraperitoneally and DE leaves (at doses of 25, 50 and 100 mg/kgBW) by gavage. Control groups received either distilled water or tamoxifen alone. Treatments lasted 37 days. The 38th day, animals were sacrificed under anesthesia (diazepam: 10 mg/kgBW and ketamine: 50 mg/kgBW). The relative uterine weight was determined and the histological analysis of the uterus and mammary gland was performed. The oxidative status of the uterus was assessed and the levels of cholesterol and estradiol were evaluated in serum and uterus.

RESULTS

Tamoxifen increased uterine weight and induced endometrial hyperplasia. This effect was associated with increased uterine levels of cholesterol (164.22%; p < 0.001), estradiol (927.5%; p < 0.001) and malondiadehyde (86%; p < 0.05), but unchanged antioxidant enzymes activities. The administration of DE leaves unchanged tamoxifen-increased uterine weight but reduced uterine epithelium hypertrophy (56.4%; p < 0.01). DE also increased uterine levels of malondiadehyde and antioxidant enzymes. The levels of estradiol and cholesterol in the uterus decreased while no changes were observed in the mammary gland of animals treated with tamoxifen alone or in co-administration with DE.

CONCLUSIONS

D. edulis has antiproliferative properties and could complement endocrine therapy of estrogen-dependent breast cancer.

In Silico Investigation of a Chimeric IL24-LK6 Fusion Protein as a Potent Candidate Against Breast Cancer

Targeted delivery of therapeutic anticancer chimeric molecules enhances the efficacy of drug by improving cellular uptake and circulation time. Engineering the molecules to facilitate the specific interaction between chimeric protein and its receptor is critical to elucidate biological mechanism as well as accuracy in modeling of complexes. A theoretically designed novel protein-protein interfaces can serve as a bottom-up method for comprehensive understanding of interacting protein residues. This study was aimed for in silico analyses of a chimeric fusion protein against breast cancer. The amino acid sequences of the interleukin 24 (IL-24) and LK-6 peptide were used to design the chimeric fusion protein via a rigid linker. The secondary and tertiary structures along with physicochemical properties by ProtParam and solubility were predicted using online software. The validation and quality of the fusion protein was confirmed by Rampage and ERRAT2. The newly designed fusion construct has a total length of 179 amino acids. The top-ranked structure from alpha fold2 showed 18.1 KD molecular weight by ProtParam, quality factor of 94.152 by ERRAT, and a valid structure by a Ramachandran plot with 88.5% residues in the favored region. Finally, the docking and simulation studies were performed using HADDOCK and Desmond module of Schrodinger. The quality, validity, interaction analysis, and stability of the fusion protein depict a functional molecule. The fusion gene IL24-LK6 after cloning and expression in a suitable prokaryotic cell might be a useful candidate for developing a novel anticancer therapy.

Therapeutic Peptides for Treatment of Lung Diseases: Infection, Fibrosis, and Cancer

Various lung diseases endanger people's health. Side effects and pharmaceutical resistance complicate the treatment of acute lung injury, pulmonary fibrosis, and lung cancer, necessitating the development of novel treatments. Antimicrobial peptides (AMPs) are considered to serve as a viable alternative to conventional antibiotics. These peptides exhibit a broad antibacterial activity spectrum as well as immunomodulatory properties. Previous studies have shown that therapeutic peptides including AMPs had remarkable impacts on animal and cell models of acute lung injury, pulmonary fibrosis, and lung cancer. The purpose of this paper is to outline the potential curative effects and mechanisms of peptides in the three types of lung diseases mentioned above, which may be used as a therapeutic strategy in the future.

Targeting the NRF2/KEAP1 pathway in cervical and endometrial cancers

Cervical and endometrial cancers are among the most dangerous gynaecological malignancies, with high fatality and recurrence rates due to frequent diagnosis at an advanced stage and chemoresistance onset. The NRF2/KEAP1 signalling pathway plays an important role in protecting cells against oxidative damage due to increased reactive oxygen species (ROS) levels. NRF2, activated by ROS, induces the expression of antioxidant enzymes such as heme oxygenase, catalase, glutathione peroxidase and superoxide dismutase which neutralize ROS, protecting cells against oxidative stress damage. However, activation of NRF2/KEAP1 signalling in cancer cells results in chemoresistance, inactivating drug-mediated oxidative stress and protecting cancer cells from drug-induced cell death. We review the literature on the role of the NRF2/KEAP1 pathway in cervical and endometrial cancers, with a focus on the expression of its components and downstream genes. We also examine the role of the NRF2/KEAP1 pathway in chemotherapy resistance and how this pathway can be modulated by natural and synthetic modulators.

Anti-proliferative, apoptotic potential of synthesized selenium nanoparticles against breast cancer cell line (MCF7)

Nano-biotechnology has grown rapidly and become an integral part of modern disease diagnosis and treatment. The aim of this survey was to evaluate the anticancer activity of synthesized selenium nanoparticles (Se-NPs) against breast cancer cells (MCF-7). The prepared Se-NPs were examined by ultraviolet-visible spectroscopy, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscope (SEM), and energy dispersive spectroscopy (EDX). Antioxidant activity of Se-NPs property was studied by radical scavenging (DPPH) assay. The in-vitro cytotoxicity of Se-NPs was evaluated by MTT assay. In addition; the biological assessment (antioxidant and cytotoxicity) of synthesized Se-NPs was examined via molecular docking simulations. Synthesis of Se-NPs was characterized by several studies such as UV-absorbance, showing peak values in the range of 268 nm. Nanoparticle sizes of the nanoparticles are confirmed by dynamic light scattering analysis, indicating that average size is about 203 nm. The quantity of selenium in Se-NPs is 90.15% by weight, as confirmed by EDX. Synthesized Se-NPs have anti-proliferative effects on MCF-7 cell lines. Cytotoxicity and apoptotic potential assays exhibited a dose-dependent effect against MCF-7 cells using an MTT assay. Like anti-cancer activity, anti-oxidant activity of Se-NPs was dose-dependent. Findings showed that the Se-NPs complexes have the highest inhibitory effect against cytotoxic and antioxidant receptors. Results of this study demonstrated that Se-NPs had strong potential to scavenge free radicals and are cytotoxic against the MCF-7 cancer cell line.

Preparation and Characterization of Palladium Derivate-Loaded Micelle Formulation in Vitro as an Innovative Therapy Option against Non-Small Cell Lung Cancer Cells

Nanoparticles have been used in cancer treatments to target tumor and reduce side effects. In this study, we aimed to increase the effectiveness of palladium(II) complex [PdCl(terpy)](sac) ⋅ 2H₂ O, which previously showed anticancer potential, by preparing the nanoparticle formulation. An inhalable micellar dispersion containing a palladium(II) complex (PdNP) was prepared and its physicochemical characteristics were evaluated using in vitro tests. Morphology, size and surface charges of particle and loading/encapsulation efficiency of PdNP were analyzed by scanning electron microscopy, zeta sizer and inductively coupled plasma mass spectrometry while aerosol properties of PdNP were measured by the next generation impactor. A549 and H1299 non-small lung cancer cell types were used for cytotoxicity using SRB and ATP assays. Fluorescent staining and M30 antigen assay were carried out for cell death evaluation. Apoptosis was confirmed by flow cytometry analyses. SEM, particle size, and zeta potential results showed the particles have inhalable properties. The amount of the palladium(II) complex loaded into the particles was quantified which indicated high encapsulation efficiencies (97 %). The micellar dispersion expected to reach the alveolar region and the brachial region was determined 35 % and 47 %, respectively. PdNP showed an anti-growth effect by increasing reactive oxygen species that is followed by the induction of mitochondria-dependent apoptosis that is evidenced by pyknotic nuclei and M30 antigen level increments and disruption of polarization of membrane in mitochondria (Δψm). The results show that PdNP might be a promising inhalable novel complex to be used in non-small cell lung cancer, which warrants animal studies in further.

Is Curcumin the Answer to Future Chemotherapy Cocktail?

The rise in cancer cases in recent years is an alarming situation worldwide. Despite the tremendous research and invention of new cancer therapies, the clinical outcomes are not always reassuring. Cancer cells could develop several evasive mechanisms for their survivability and render therapeutic failure. The continuous use of conventional cancer therapies leads to chemoresistance, and a higher dose of treatment results in even greater toxicities among cancer patients. Therefore, the search for an alternative treatment modality is crucial to break this viscous cycle. This paper explores the suitability of curcumin combination treatment with other cancer therapies to curb cancer growth. We provide a critical insight to the mechanisms of action of curcumin, its role in combination therapy in various cancers, along with the molecular targets involved. Curcumin combination treatments were found to enhance anticancer effects, mediated by the multitargeting of several signalling pathways by curcumin and the co-administered cancer therapies. The preclinical and clinical evidence in curcumin combination therapy is critically analysed, and the future research direction of curcumin combination therapy is discussed.

New designed pH-responsive histidine-rich peptides with antitumor activity

Anticancer peptides have received widespread attention as alternative antitumor therapeutics due to their unique action mode. However, the systemic toxicity hampers their successful utilisation in tumour therapy. Here, the tumour acidic environment was used as a trigger to design a series of histidine-rich peptides by optimising the distribution of histidine and leucine based on the amphiphilic peptide LK, in hoping to achieve desirable acid-activate anticancer peptides. Among all the obtained peptides, L9H5-1 showed enhanced antitumor activity at acidic pH concomitant with low toxicity at normal pH, exhibiting excellent pH-response. At acidic pH, protonated L9H5-1 could rapidly kill tumour cells by efficient membrane disruption as evidenced by in vitro experiments, including increasing intracellular PI uptake and LDH release, dramatic membrane damage and increase of later apoptotic/necrotic cells. Moreover, no cell cycle arrest was observed after treated with L9H5-1. Interestingly, this study found that the new peptides with the same number of histidines and leucines displayed different pH-dependent antitumor activity, indicating that the position of amino acid alteration is extremely important for the design of acid-activated histidine-rich peptides. In short, our work provides a new avenue to develop new acid-activated anticancer peptides as promising antitumor drugs with high efficiency and good selectivity.

In Vitro and MD Simulation Study to Explore Physicochemical Parameters for Antibacterial Peptide to Become Potent Anticancer Peptide

Although the physicochemical properties of antimicrobial peptides (AMPs) and anticancer peptides (ACPs) are very similar, it remains unclear which specific parameter(s) of ACPs confer the major anticancer activity. By answering how to construct a short AMP/ACP that could easily be synthesized in the most cost effective way plus conferring a maximum anticancer effect is a very important scientific breakthrough in the development of protein/peptide drugs. In this study, an 18-amino-acids antimicrobial peptide, AcrAP1 (named AP1-Z1), was used as a template. Bioinformatics algorithms were then performed to design its six mutants (AP1-Z3a, AP1-Z3b, AP1-Z5a, AP1-Z5b, AP1-Z7, and AP1-Z9). After a series of in vitro experiments plus intensive computational analysis, the data demonstrated that AP1-Z5a and AP1-Z5b induced both apoptosis and anti-angiogenic effects to achieve the maximum anticancer activity. Specifically, the most effective mutant, AP1-Z5b, exhibited high selectivity for the charged membrane in molecular dynamics simulations. These findings clearly demonstrated that both charge and hydrophobicity play an important role and are necessary to reach an optimum equilibrium for optimizing the anticancer activity of AMPs. Overall, the present study provides a very crucial theoretical basis and important scientific evidence on the key physicochemical parameters of ACP drugs development.

Tamoxifen in horses: pharmacokinetics and safety study

Background

Tamoxifen (TAM), a selective modulator of estrogen receptors (SERMs) has been recently explored as a therapeutic option for the oral treatment of airway inflammation in the horse. The objective of this work was to establish pharmacokinetic parameters of TAM and its main metabolites in equines, as well as to determine its clinical safety in short-term treatments.

Results

We determined TAM and its three main metabolites (4-OH tamoxifen, endoxifen, and N-desmethyl tamoxifen) in plasma after single administration of 0.25 mg/kg in healthy adult horses (n = 12). A maximum concentration of TAM was achieved 3 h after the oral administration (4.65 pg/mL ± 1.69); 4-OH tamoxifen was the metabolite that reached the highest concentration (78 pg/mL ± 70), followed by N-desmethyl tamoxifen (0.43 pg / mL ± 0.48), and finally endoxifen (0.17 pg/mL ± 0.17). All metabolites showed peak concentration 2 h after oral administration of the drug. Oral TAM bioavailability was 13,15% ± 4,18, with a steady state volume of distribution of 7831 ± 2922 (L/kg). Elimination half-life was 15.40 ± 5.80 h, and clearance was 5876 ± 699 (mL/kg/min). Clinical safety of TAM was determined over a 7-day course of treatment (0.25 mg/kg, orally q 24 h, n = 20). No adverse effects were observed through clinical examination, blood hematology, serum biochemistry, ophthalmological and reproductive examinations. Endometrial edema observed in some mares was attributed to normal cyclic activity.

Conclusions

Tamoxifen has moderate oral bioavailability and a large volume of distribution, with three main metabolites in horses. Additionally, oral TAM administration over a 7-day treatment period demonstrated to be clinically safe, without adverse effects on clinical, hematological or serum biochemical parameters. These data could contribute to the continued research into this drug’s potential for the treatment of different inflammatory conditions in equine species.

Electronic supplementary material

The online version of this article (10.1186/s13620-019-0143-7) contains supplementary material, which is available to authorized users.

Mutational landscape implicates epithelial-mesenchymal transition gene TGF-β2 mutations for uterine carcinosarcoma after adjuvant tamoxifen therapy for breast carcinoma

Uterine carcinosarcoma (UCS) is a rare aggressive malignancy. Several reports previously described UCS occurring after tamoxifen therapy for breast carcinoma. However, the genetic landscape of tamoxifen-related UCS remains unclear. We performed whole-exome sequencing of two UCSs after tamoxifen therapy for breast carcinoma to determine mutational profile of UCSs and those corresponding breast carcinomas. Our results demonstrated that 374 somatic variants in 141 genes were shared across the two UCSs, whereas no shared somatic variations across the breast carcinomas were found. Pathway analysis indicated the MAPK pathway, including the epithelial-mesenchymal transition (EMT) inducer gene TGF-β2 mutations (c. 1039G > A and c. 1040C > T, both p.A347T), recurrently occurred in UCS, while ER-related gene EP300 (p.P16L) and ESR1 (p.V355I) mutations were identified independently in breast carcinomas. These findings highlight the EMT-related gene TGF-β2 variants in the tumorigenesis of tamoxifen-related UCS, support the possibility that tamoxifen mediates its effect on UCS by enhancing mutations of driver genes, and also provides the rationale for clinical investigation in ER-related gene mutation in breast carcinoma to predict the risk for UCS after tamoxifen treatment.

Tamoxifen activates Nrf2-dependent SQSTM1 transcription to promote endometrial hyperplasia

Long-term application of Tamoxifen (TAM) is usually recommended for hormone receptor positive breast cancer patients. Unfortunately, TAM will inevitably increase the incidence of endometrial hyperplasia even endometrial cancer. Despite of substantial investigations, no effective approaches to prevent TAM-induced endometrial carcinogenesis have been acknowledged. In this study, we found that inhibition of Nrf2 could be valuable to prevent TAM-induced endometrial hyperplasia. Upon TAM treatment, the mRNA and protein expression of autophagy adaptor SQSTM1 was specifically increased in endometrial cells but not breast cancer cells. Knocking-down of SQSTM1 expression retarded TAM-promoted growth of endometrial cancer cells. TAM stimulated SQSTM1 transcription specifically in endometrial cells by enhancing phosphorylation and nuclear translocation of Nrf2. Indeed, the expression of Nrf2 and SQSTM1 were positively correlated in primary endometrial tissues. In rats with TAM-induced endometrial hyperplasia, both Nrf2 and SQSTM1 expression were increased. Nrf2 inhibitor brusatol effectively attenuated TAM-induced SQSTM1 upregulation and endometrial hyperplasia. The kinase of Nrf2, PRKCD, was activated by TAM. Once PRKCD was depleted, TAM failed to promote Nrf2 phosphorylation and SQSTM1 expression. In summary, TAM stimulated Nrf2-dependent SQSTM1 transcription to promote endometrial hyperplasia by activating PRKCD. Therefore, blocking PRKCD-Nrf2-SQSTM1 signaling could be useful to prevent TAM-induced endometrial hyperplasia.

Selective cytotoxicity of the antibacterial peptide ABP-dHC-Cecropin A and its analog towards leukemia cells

Some cationic antibacterial peptides, with typical amphiphilic α-helical conformations in a membrane-mimicking environment, exhibit anticancer properties as a result of a similar mechanism of action towards both bacteria and cancer cells. We previously reported the cDNA sequence of the antimicrobial peptide ABP-dHC-Cecropin A precursor cloned from drury (Hyphantria cunea) (dHC). In the present study, we synthesized and structurally characterized ABP-dHC-Cecropin A and its analog, ABP-dHC-Cecropin A-K(24). Circular dichroism spectroscopy showed that ABP-dHC-Cecropin A and its analog adopt a well-defined α-helical structure in a 50% trifluorethanol solution. The cytotoxicity and cell selectivity of these peptides were further examined in three leukemia cell lines and two non-cancerous cell lines. The MTT assay indicated both of these peptides have a concentration-dependent cytotoxic effect in leukemia cells, although the observed cytotoxicity was greater with ABP-dHC-Cecropin A-K(24) treatment, whereas they were not cytotoxic towards the non-cancerous cell lines. Moreover, ABP-dHC-Cecropin A and its analog had a lower hemolytic effect in human red blood cells. Together, these results suggest the peptides are selectively cytotoxic towards leukemia cells. Confocal laser scanning microscopy determined that the peptides were concentrated at the surface of the leukemia cells, and changes in the cell membrane were determined with a permeability assay, which suggested that the anticancer activity of ABP-dHC-Cecropin A and its analog is a result of its presence at the leukemia cell membrane. ABP-dHC-Cecropin A and its analog may represent a novel anticancer agent for leukemia therapy, considering its cancer cell selectivity and relatively low cytotoxicity in normal cells.

An Investigation on a Novel Anti-tumor Fusion Peptide of FSH33-53-IIKK

A novel fusion peptide FSH_33-53-IIKK was designed and expected to combine the follicle stimulating hormone receptor (FSHR) targeting and tumor toxicity. In vitro and in vivo study showed the anti-tumor activity of FSH_33-53-IIKK was enhanced compared to that of IIKK only. FSH_33-53-IIKK could inhibit the growth of tumor via apoptosis and autophagy pathways. In summary, combining the tumor marker-target peptide and anti-tumor peptide together may be an efficient way to search for better anti-tumor candidates.

Expression and purification of toxic anti-breast cancer p28-NRC chimeric protein

BACKGROUND

Chimeric proteins consisting of a targeting moiety and a cytotoxic moiety are now under intense research focus for targeted therapy of cancer. Here, we report cloning, expression, and purification of such a targeted chimeric protein made up of p28 peptide as both targeting and anticancer moiety fused to NRC peptide as a cytotoxic moiety. However, since the antimicrobial activity of the NRC peptide would intervene expression of the chimeric protein in Escherichia coli, we evaluated the effects of two fusion tags, that is, thioredoxin (Trx) and 6x-His tags, and various expression conditions, on the expression of p28-NRC chimeric protein.

MATERIALS AND METHODS

In order to express the chimeric protein with only 6x-His tag, pET28 expression plasmid was used. Cloning in pET32 expression plasmid was performed to add both Trx and 6x-His tags to the chimeric protein. Expression of the chimeric protein with both plasmids was evaluated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blot analysis following optimization of expression conditions and host strains.

RESULTS

Expression of the chimeric protein in pET28a was performed. However, expression yield of the chimeric protein was low. Optimization of culture conditions and host strains led to reasonable expression yield of the toxic chimeric protein in pET32a vector. In cases of both plasmids, approximately 10 kDa deviation of the apparent molecular weight from the theoretical one was seen in SDS-PAGE of purified chimeric proteins.

CONCLUSIONS

The study leads to proper expression and purification yield of p28-NRC chimeric protein with Trx tag following optimizing culture conditions and host strains.

Membranolytic anticancer peptides

Understanding the structure–activity relationships and mechanisms of action of membranolytic anticancer peptides could help them advance to therapeutic success.

In vitro Characterization of the Rapid Cytotoxicity of Anticancer Peptide HPRP-A2 through Membrane Destruction and Intracellular Mechanism against Gastric Cancer Cell Lines

In this study, HPRP-A2, a synthetic 15-mer cationic peptides with all D-amino acids, effectively inhibited the survival of gastric cell lines in a dose-dependent manner. Gastric tumor cells killing by HPRP-A2 involves a rapid collapse of the membrane integrity and intracellular pathways. Propidium iodide (PI) and lactate dehydrogenase (LDH) assays demonstrated that one-hour treatment with HPRP-A2 led to membrane permeability changes of BGC-823 cells in a dose-dependent manner. Moreover, HPRP-A2 induced apoptosis in BGC-823 cells involves a marked increase in generation of reactive oxygen species (ROS),caspase-3, -8 and -9 activation, a reduction of mitochondrial membrane potential (MMP), and cell cycle arrest in G1 phase. In addition to its inherent cytotoxicity, HPRP-A2 synergized strongly with doxorubicin (DOX) to enhance the efficacy of killing gastric tumor cells in vitro. We believe that HPRP-A2 with all D-amino acids could be a potent candidate of anticancer therapeutics, especially in combination therapy.

Enhanced killing of breast cancer cells by a d-amino acid analog of the winter flounder-derived pleurocidin NRC-03

Cationic antimicrobial peptides (CAPs) defend against pathogens and, in some cases, exhibit potent anticancer activities. We previously reported that the pleurocidin NRC-03 causes lysis of breast cancer and multiple myeloma cells. NRC-03 also reduces the EC50 of other cytotoxic compounds and prevents tumor growth in vivo. However, the therapeutic utility of NRC-03 may be limited by its susceptibility to degradation by proteases. The goal of this study was to characterize the anticancer activities of a d-amino acid analog of NRC-03 ([D]-NRC-03) that was predicted to be resistant to proteolytic degradation. Unlike NRC-03, [D]-NRC-03 was not degraded by human serum or trypsin and, in comparison to NRC-03, showed increased killing of breast cancer cells, including multidrug-resistant cells; however, [D]-NRC-03 was somewhat more cytotoxic than NRC-03 for several types of normal cells. Importantly, [D]-NRC-03 was more effective than NRC-03 in vivo since 4-fold less peptide was required for an equivalent inhibitory effect on the growth of breast cancer cell xenografts in immune-deficient mice. These findings demonstrate that a d-amino acid analog of NRC-03 overcomes a major limitation to the therapeutic use of NRC-03, namely peptide stability. Further modification of [D]-NRC-03 is required to improve its selectivity for cancer cells.

Buforin IIb induces endoplasmic reticulum stress-mediated apoptosis in HeLa cells

Buforin IIb, a novel cell-penetrating anticancer peptide derived from histone H2A, has been reported to induce mitochondria-dependent apoptosis in tumor cells. However, increasing evidence suggests that endoplasmic reticulum and mitochondria cooperate to signal cell death. In this study, we investigated the mechanism of buforin IIb-induced apoptosis in human cervical carcinoma HeLa cells by focusing on ER stress-mediated mitochondrial membrane permeabilization. Two-dimensional PAGE coupled with MALDI-TOF and western blot analysis showed that buforin IIb treatment of HeLa cells resulted in upregulation of ER stress proteins. PBA (ER stress inhibitor) and BAPTA/AM (Ca(2+) chelator) pretreatment rescued viability of buforin IIb-treated cells through abolishing phosphorylation of SAPK/JNK and p38 MAPK. SP600125 (SAPK/JNK inhibitor) and SB203580 (p38 MAPK inhibitor) attenuated down-regulation of Bcl-xL/Bcl-2, mitochondrial translocation of Bax, and cytochrome c release from mitochondria. Taken together, our data suggest that the ER stress pathway has an important role in the buforin IIb-induced apoptosis in HeLa cells.

Tryptophan as a probe to study the anticancer mechanism of action and specificity of α-helical anticancer peptides

In the present study, a single tryptophan, as a fluorescence probe, was shifted from the N-terminus to the middle and to the C-terminus of a 26-residue α-helical anticancer peptide sequence to study the mechanism of action and specificity. The hydrophobicity of peptides, as well as peptide helicity and self-associating ability, were slightly influenced by the position change of tryptophan in the peptide sequence, while the hemolytic activity and anticancer activity of the peptide analogs remained the same. The tryptophan fluorescence experiment demonstrated that peptide analogs were more selective against LUVs mimicking cancer cell membranes than LUVs mimicking normal cell membranes. During the interaction with target membranes, the N-terminus of an anticancer peptide may be inserted vertically or tilted into the hydrophobic components of the phospholipid bilayer first. The thermodynamic parameters of the peptides PNW and PCW, when interacting with zwitterionic DMPC or negatively charged DMPS, were determined by ITC. DSC experiments showed that peptide analogs significantly altered the phase transition profiles of DMPC, but did not dramatically modify the phase transition of DMPS. It is demonstrated that hydrophobic interactions are the main driving force for peptides interacting with normal cell membranes, whilst, electrostatic interactions dominate the interactions between peptides and cancer cell membranes. Utilizing tryptophan as a fluorescence probe molecule appears to be a practicable approach to determine the interaction of peptides with phospholipid bilayers.

Tamoxifen for women at high risk of breast cancer

Tamoxifen has been used as a treatment for women who have been diagnosed with breast cancer for roughly four decades and has been approved as chemoprevention for over ten years. Although tamoxifen has been proven to be beneficial in preventing breast cancer in high-risk women, its use has not been widely embraced. To some extent, this is due to several of its side effects, including an increased risk of endometrial cancer and pulmonary embolism, but these serious side effects are rare. The risks and benefits of tamoxifen chemoprevention should be considered for each patient.

Green synthesis of silver nanoparticles using Ganoderma neo-japonicum Imazeki: a potential cytotoxic agent against breast cancer cells

BACKGROUND

Silver nanoparticles (AgNPs) are an important class of nanomaterial for a wide range of industrial and biomedical applications. AgNPs have been used as antimicrobial and disinfectant agents due their detrimental effect on target cells. The aim of our study was to determine the cytotoxic effects of biologically synthesized AgNPs using hot aqueous extracts of the mycelia of Ganoderma neo-japonicum Imazeki on MDA-MB-231 human breast cancer cells.

METHODS

We developed a green method for the synthesis of water-soluble AgNPs by treating silver ions with hot aqueous extract of the mycelia of G. neo-japonicum. The formation of AgNPs was characterized by ultraviolet-visible absorption spectroscopy, X-ray diffraction, dynamic light scattering, and transmission electron microscopy. Furthermore, the toxicity of synthesized AgNPs was evaluated using a series of assays: such as cell viability, lactate dehydrogenase leakage, reactive oxygen species generation, caspase 3, DNA laddering, and terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick-end labeling in human breast cancer cells (MDA-MB-231).

RESULTS

The ultraviolet-visible absorption spectroscopy results showed a strong resonance centered on the surface of AgNPs at 420 nm. The X-ray diffraction analysis confirmed that the synthesized AgNPs were single-crystalline, corresponding with the result of transmission electron microscopy. Treatment of MDA-MB-231 breast cancer cells with various concentrations of AgNPs (1-10 μg/mL) for 24 hours revealed that AgNPs could inhibit cell viability and induce membrane leakage in a dose-dependent manner. Cells exposed to AgNPs showed increased reactive oxygen species and hydroxyl radical production. Furthermore, the apoptotic effects of AgNPs were confirmed by activation of caspase 3 and DNA nuclear fragmentation.

CONCLUSION

The results indicate that AgNPs possess cytotoxic effects with apoptotic features and suggest that the reactive oxygen species generated by AgNPs have a significant role in apoptosis. The present findings suggest that AgNPs could contribute to the development of a suitable anticancer drug, which may lead to the development of a novel nanomedicine for the treatment of cancers.

Current scenario of peptide-based drugs: the key roles of cationic antitumor and antiviral peptides

Cationic antimicrobial peptides (AMPs) and host defense peptides (HDPs) show vast potential as peptide-based drugs. Great effort has been made in order to exploit their mechanisms of action, aiming to identify their targets as well as to enhance their activity and bioavailability. In this review, we will focus on both naturally occurring and designed antiviral and antitumor cationic peptides, including those here called promiscuous, in which multiple targets are associated with a single peptide structure. Emphasis will be given to their biochemical features, selectivity against extra targets, and molecular mechanisms. Peptides which possess antitumor activity against different cancer cell lines will be discussed, as well as peptides which inhibit virus replication, focusing on their applications for human health, animal health and agriculture, and their potential as new therapeutic drugs. Moreover, the current scenario for production and the use of nanotechnology as delivery tool for both classes of cationic peptides, as well as the perspectives on improving them is considered.

Cytotoxicity of biologically synthesized silver nanoparticles in MDA-MB-231 human breast cancer cells

Silver nanoparticles (AgNPs) have been used as an antimicrobial and disinfectant agents. However, there is limited information about antitumor potential. Therefore, this study focused on determining cytotoxic effects of AgNPs on MDA-MB-231 breast cancer cells and its mechanism of cell death. Herein, we developed a green method for synthesis of AgNPs using culture supernatant of Bacillus funiculus, and synthesized AgNPs were characterized by various analytical techniques such as UV-visible spectrophotometer, particle size analyzer, and transmission electron microscopy (TEM). The toxicity was evaluated using cell viability, metabolic activity, and oxidative stress. MDA-MB-231 breast cancer cells were treated with various concentrations of AgNPs (5 to 25 μg/mL) for 24 h. We found that AgNPs inhibited the growth in a dose-dependent manner using MTT assay. AgNPs showed dose-dependent cytotoxicity against MDA-MB-231 cells through activation of the lactate dehydrogenase (LDH), caspase-3, reactive oxygen species (ROS) generation, eventually leading to induction of apoptosis which was further confirmed through resulting nuclear fragmentation. The present results showed that AgNPs might be a potential alternative agent for human breast cancer therapy.

Design of potent, non-toxic anticancer peptides based on the structure of the antimicrobial peptide, temporin-1CEa

Recent advances in the search for novel anticancer agents have indicated that the positively charged antimicrobial peptides have emerged as promising agents offering several advantages over the conventional anticancer drugs. As a naturally occurring, cationic, α-helical antimicrobial peptide, temproin-1CEa has been proved to exhibit a potent anticancer effect and a moderate hemolytic activity. In order to reduce the hemolytic activity of temporin-1CEa and improve its anticancer potency towards a range of human breast cancer cells, in the present study, six analogs of temporin-1CEa were rationally designed and synthesized. The amphipathicity levels and α-helical structural patterns of peptides were reserved, while their cationic property and hydrophobicity were changed. The results of MTT and hemolysis assay indicated that the analog peptides displayed an improved anticancer activity and showed an overall optimized therapeutic index. The hydrophobicity of peptides was positively correlated with their hemolytic and antitumor activities. Moreover, the data suggest a strategy of increasing the cationicity while maintaining the moderate hydrophobicity of naturally occurring amphipathic α-helical peptides to generate analogs with improved cytotoxicity against tumor cells but decreased activity against non-neoplastic cells such as human erythrocytes. This work highlights the potential for rational design and synthesis of improved antimicrobial peptides that have the capability to be used therapeutically for treatment of cancers.

The elimination of P-glycoprotein over-expressing cancer cells by antimicrobial cationic peptide NK-2: the unique way of multi-drug resistance modulation

Most chemotherapeutics harm normal cells causing severe side effects and induce the development of resistance in cancer cells. Antimicrobial peptides (AMPs), recognized as anti-cancer agents, may overcome these limitations. The most studied mechanism underlying multi-drug resistance (MDR) is the over-expression of cell membrane transporter P-glycoprotein (P-gp), which extrudes a variety of hydrophobic drugs. Additionally, P-gp contributes to cell membrane composition and increases the net negative charge on cell surface. We postulated that NK-lysin derived cationic peptide NK-2 might discriminate and preferentially eliminate P-gp over-expressing cancer cells. To test this hypothesis, we employed MDR non-small cell lung carcinoma (NCI-H460/R) and colorectal carcinoma (DLD1-TxR) cell lines with high P-gp expression. MDR cancer cells that survived NK-2 treatment had decreased P-gp expression and were more susceptible to doxorubicin. We found that NK-2 more readily eliminated P-gp high-expressing cells. Acting in 'carpet-like' manner NK-2 co-localized with P-gp on the MDR cancer cell membrane. The inhibition of P-gp reduced the NK-2 effect in MDR cancer cells and, vice versa, NK-2 decreased P-gp transport activity. In conclusion, NK-2 could modulate MDR in unique way, eliminating the P-gp high-expressing cells from heterogeneous cancers and making them more vulnerable to classical drug treatment.

Improved anticancer potency by head-to-tail cyclization of short cationic anticancer peptides containing a lipophilic β(2,2) -amino acid

We have recently reported a series of synthetic anticancer heptapeptides (H-KKWβ(2,2) WKK-NH(2) ) containing a central achiral and lipophilic β(2,2) -amino acid that display low toxicity against non-malignant cells and high proteolytic stability. In the present study, we have further investigated the effects of increasing the rigidity and amphipathicity of two of our lead heptapeptides by preparing a series of seven to five residue cyclic peptides containing the two most promising β(2,2) -amino acid derivatives as part of the central lipophilic core. The peptides were tested for anticancer activity against human Burkitt's lymphoma (Ramos cells), haemolytic activity against human red blood cells (RBC) and cytotoxicity against healthy human lung fibroblast cells (MRC-5). The results demonstrated a considerable increase in anticancer potency following head-to-tail peptide cyclization, especially for the shortest derivatives lacking a tryptophan residue. High-resolution NMR studies and molecular dynamics simulations together with an annexin-V-FITC and propidium iodide fluorescent assay showed that the peptides had a membrane disruptive mode of action and that the more potent peptides penetrated deeper into the lipid bilayer. The need for new anticancer drugs with novel modes of action is demanding, and development of short cyclic anticancer peptides with an overall rigidified and amphipathic structure is a promising approach to new anticancer agents.

Synthesis of anticancer heptapeptides containing a unique lipophilic β(2,2) -amino acid building block

We report a series of synthetic anticancer heptapeptides (H-KKWβ(2,2) WKK-NH(2)) containing eight different central lipophilic β(2,2) -amino acid building blocks, which have demonstrated high efficiency when used as scaffolds in small cationic antimicrobial peptides and peptidomimetics. The most potent peptides in the present study had IC(50) values of 9-23 µm against human Burkitt's lymphoma and murine B-cell lymphoma and were all nonhaemolytic (EC(50)  > 200 µm). The most promising peptide 10e also demonstrated low toxicity against human embryonic lung fibroblast cells and peripheral blood mononuclear cells and exceptional proteolytic stability.

Pleurocidin-family cationic antimicrobial peptides are cytolytic for breast carcinoma cells and prevent growth of tumor xenografts

Introduction

Cationic antimicrobial peptides (CAPs) defend against microbial pathogens; however, certain CAPs also exhibit anticancer activity. The purpose of this investigation was to determine the effect of the pleurocidin-family CAPs, NRC-03 and NRC-07, on breast cancer cells.

Methods

MTT (3-(4,5-dimethylthiazol-2-yl)2,5-diphenyltetrazolium bromide) and acid phosphatase cell-viability assays were used to assess NRC-03- and NRC-07-mediated killing of breast carcinoma cells. Erythrocyte lysis was determined with hemolysis assay. NRC-03 and NRC-07 binding to breast cancer cells and normal fibroblasts was assessed with fluorescence microscopy by using biotinylated-NRC-03 and -NRC-07. Lactate dehydrogenase-release assays and scanning electron microscopy were used to evaluate the effect of NRC-03 and NRC-07 on the cell membrane. Flow-cytometric analysis of 3,3'-dihexyloxacarbocyanine iodide- and dihydroethidium-stained breast cancer cells was used to evaluate the effects of NRC-03 and NRC-07 on mitochondrial membrane integrity and reactive oxygen species (ROS) production, respectively. Tumoricidal activity of NRC-03 and NRC-07 was evaluated in NOD SCID mice bearing breast cancer xenografts.

Results

NRC-03 and NRC-07 killed breast cancer cells, including drug-resistant variants, and human mammary epithelial cells but showed little or no lysis of human dermal fibroblasts, umbilical vein endothelial cells, or erythrocytes. Sublethal doses of NRC-03 and, to a lesser extent, NRC-07 significantly reduced the median effective concentration (EC₅₀) of cisplatin for breast cancer cells. NRC-03 and NRC-07 bound to breast cancer cells but not fibroblasts, suggesting that killing required peptide binding to target cells. NRC-03- and NRC-07-mediated killing of breast cancer cells correlated with expression of several different anionic cell-surface molecules, suggesting that NRC-03 and NRC-07 bind to a variety of negatively-charged cell-surface molecules. NRC-03 and NRC-07 also caused significant and irreversible cell-membrane damage in breast cancer cells but not in fibroblasts. NRC-03- and NRC-07-mediated cell death involved, but did not require, mitochondrial membrane damage and ROS production. Importantly, intratumoral administration of NRC-03 and NRC-07 killed breast cancer cells grown as xenografts in NOD SCID mice.

Conclusions

These findings warrant the development of stable and targeted forms of NRC-03 and/or NRC-07 that might be used alone or in combination with conventional chemotherapeutic drugs for the treatment of breast cancer.

Membrane-active host defense peptides--challenges and perspectives for the development of novel anticancer drugs

Although much progress has been achieved in the development of cancer therapies in recent decades, problems continue to arise particularly with respect to chemotherapy due to resistance to and low specificity of currently available drugs. Host defense peptides as effector molecules of innate immunity represent a novel strategy for the development of alternative anticancer drug molecules. These cationic amphipathic peptides are able to discriminate between neoplastic and non-neoplastic cells interacting specifically with negatively charged membrane components such as phosphatidylserine (PS), sialic acid or heparan sulfate, which differ between cancer and non-cancer cells. Furthermore, an increased number of microvilli has been found on cancer cells leading to an increase in cell surface area, which may in turn enhance their susceptibility to anticancer peptides. Thus, part of this review will be devoted to the differences in membrane composition of non-cancer and cancer cells with a focus on the exposure of PS on the outer membrane. Normally, surface exposed PS triggers apoptosis, which can however be circumvented by cancer cells by various means.

Host defense peptides, which selectively target differences between cancer and non-cancer cell membranes, have excellent tumor tissue penetration and can thus reach the site of both primary tumor and distant metastasis. Since these molecules kill their target cells rapidly and mainly by perturbing the integrity of the plasma membrane, resistance is less likely to occur. Hence, a chapter will also describe studies related to the molecular mechanisms of membrane damage as well as alternative non-membrane related mechanisms. In vivo studies have demonstrated that host defense peptides display anticancer activity against a number of cancers such as e.g. leukemia, prostate, ascite and ovarian tumors, yet so far none of these peptides has made it on the market. Nevertheless, optimization of host defense peptides using various strategies to enhance further selectivity and serum stability is expected to yield novel anticancer drugs with improved properties in respect of cancer cell toxicity as well as reduced development of drug resistance.

Enhancement of the cancer targeting specificity of buforin IIb by fusion with an anionic peptide via a matrix metalloproteinases-cleavable linker

Buforin IIb is a novel cell-penetrating anticancer peptide derived from histone H2A. In this study, we enhanced the cancer targeting specificity of buforin IIb using a tumor-associated enzyme-controlled activation strategy. Buforin IIb was fused with an anionic peptide (modified magainin intervening sequence, MMIS), which neutralizes the positive charge of buforin IIb and thus renders it inactive, via a matrix metalloproteinases (MMPs)-cleavable linker. The resulting MMIS:buforin IIb fusion peptide was completely inactive against MMPs-nonproducing cells. However, when the fusion peptide was administrated to MMPs-producing cancer cells, it regained the killing activity by releasing free buforin IIb through MMPs-mediated cleavage. Moreover, the activity of the fusion peptide toward MMPs-producing cancer cells was significantly decreased when the cells were pretreated with a MMP inhibitor. Taken together, these data indicate that the cancer targeting specificity of MMIS:buforin IIb is enhanced compared to the parent peptide by reactivation at the specialized areas where MMPs are pathologically produced.

Oncolytic designer host defense peptide suppresses growth of human liposarcoma

Sarcomas display a rare and heterogeneous group of tumors. Treatment options are limited. Host defense peptides (HDPs), effector molecules of the innate immune system, might provide a more effective treatment option. The aim of our study was to analyze the oncolytic activity and mode of action of a designer HDP. In vitro, the human liposarcoma cell line SW-872 and primary human fibroblasts as a control were exposed to [D]-K(3)H(3)L(9), a 15-mer D,L-amino acid designer peptide. Cell growth (MTT assay), proliferation (BrdU assay) and genotoxicity (TUNEL assay) were analyzed. The mode of action was examined via fluorescence-activated cell sorter (FACS) analysis and confocal laser scanning microscopy. In vivo, [D]-K(3)H(3)L(9) (n = 7) was administered intratumorally in a SW-872 xenograft mouse model (Foxn1nu/nu). Phosphate buffered saline served as a control (n = 5). After 4 weeks, tumor sections were histologically analyzed with respect to proliferation, cytotoxicity, vessel density and signs of apoptosis and necrosis, respectively. In vitro, [D]-K(3)H(3)L(9) highly significantly (p < 0.01) inhibited cell metabolism and proliferation. TUNEL assay revealed corresponding genotoxicity. FACS analysis suggested induction of necrosis as a cause of cell death. The mean tumor volume of the control group exponentially increased sevenfold, whereas the mean tumor growth was negligible in the treatment group. Macroscopically, [D]-K(3)H(3)L(9) induced full tumor remission in 43% of treated animals and partial remission in 43%. Vessel density was significantly reduced by 52%. Morphological analyses supported the hypothesis of cancer cell killing by necrosis. In summary, [D]-K(3)H(3)L(9) exerts very promising oncolytic activity on liposarcoma cells. Our study demonstrates the potential of HDPs as a novel therapeutic option in future soft tissue sarcoma therapy.

Cationic amphiphilic peptides with cancer-selective toxicity

During the last two decades cationic amphiphilic peptides and peptide sequences (CAPs) with cancer-selective toxicity have appeared. Based on their spectrum of anticancer activity CAPs can be divided into two major classes. The first class includes peptides that are highly potent against both bacteria and cancer cells, but not against mammalian cells. The second class includes peptides that are toxic to bacteria, and both mammalian cancer and non-cancer cells. Most antimicrobial and anticancer CAPs share a common membranolytic mode of action that results either in the selective disruption of the cancer cell membrane or permeation and swelling of mitochondria. The electrostatic attraction between the negatively charged membrane components of bacterial and cancer cells and CAPs is believed to play a crucial role in the disruption of bacterial and cancer cell membranes. This mode of action appears to bypass established resistance mechanisms. However, it is currently unclear as to why some CAPs kill cancer cells when others do not. In addition, non-membranolytic mode of actions of CAPs is increasingly recognized to contribute significantly to the anticancer activity of certain CAPs. The development of CAP-based chemotherapeutics is complicated due to the traditionally poor pharmacokinetic properties and high manufacturing costs of peptides and the low intrinsic selectivity for cancer cells. Peptidomimetic approaches combined with novel selective delivery devices show promise in overcoming some of these obstacles. Furthermore, the ability of CAPs to bypass established resistance mechanisms provides an attractive strategy to develop novel lead structures for cancer treatment.

The effect of self-assembling peptide RADA16-I on the growth of human leukemia cells in vitro and in nude mice

Nanofiber scaffolds formed by self-assembling peptide RADA16-I have been used for the study of cell proliferation to mimic an extracellular matrix. In this study, we investigated the effect of RADA16-I on the growth of human leukemia cells in vitro and in nude mice. Self-assembly assessment showed that RADA16-I molecules have excellent self-assembling ability to form stable nanofibers. MTT assay displayed that RADA16-I has no cytotoxicity for leukemia cells and human umbilical vein endothelial cells (HUVECs) in vitro. However, RADA16-I inhibited the growth of K562 tumors in nude mice. Furthermore, we found RADA16-I inhibited vascular tube-formation by HUVECs in vitro. Our data suggested that nanofiber scaffolds formed by RADA16-I could change tumor microenvironments, and inhibit the growth of tumors. The study helps to encourage further design of self-assembling systems for cancer therapy.

Novel mode of action of polybia-MPI, a novel antimicrobial peptide, in multi-drug resistant leukemic cells

As the frequent emergency of resistant tumor cells during treatment, the development of new agents with new modes of action attracts a great deal of interest. Polybia-MPI was a short cationic alpha-helical amphiphilic peptide that has selective toxicity toward cancer cells but no hemolytic activity. Its target selectivity is based on the binding preference to membranes containing anionic phospholipids by electrostatic driving. Its ability to make PI and trypan blue permeate into tumor cells at the same rate (within minutes), suggests a killing mechanism that involves plasma membrane perturbation. SEM and confocal microscopy experiments verified that the cell died as a result of acute injury and bursting, suggesting necrosis. As compared to the conventional chemotherapy, polybia-MPI targets at the cell membrane rather than enters into the cell to exert its action. So it is difficult for tumor cells to develop resistance to polybia-MPI during treatment and its action is not affected by the common multi-drug resistant mechanism. Although this is an initial study that looked at its in vitro activity rather than the in vivo activity, with the increasing resistance of conventional chemotherapy, polybia-MPI may offer a novel therapeutic strategy in the treatment of multi-drug resistant cancer.

David Kupfer, Ph.D. A mentor and a scientist

I worked with the late Dr. David Kupfer for nearly nine years at the Worcester Foundation/University of Massachusetts Medical School, Worcester, MA. I was involved in the metabolism of methoxychlor and tamoxifen, the areas of research close to David's heart. We demonstrated the metabolic pathways of these compounds in rats and humans, and the covalent binding to microsomal proteins that could result in long-term toxic manifestations. I learned a lot from David, who was a mentor and friend/colleague. His death has left a void in my heart and he will be sorely missed.

Efeito do tamoxifeno no perfil das proteínas plasmáticas em condição de diabetes mellitus tipo 1

OBJETIVO: Considerando-se que importantes avanços científicos têm sido obtidos através de estudos com Diabetes mellitus experimental, e que a ação do tamoxifeno em humanos permanece obscura, o presente trabalho objetiva acompanhar as modificações promovidas pelo diabetes e tamoxifeno no perfil eletroforético das proteínas plasmáticas. MÉTODOS: Foram utilizados 27 ratos fêmeas Wistar (180-220g peso corporal), divididos randomicamente em 5 grupos: C1 (n=3, receberam veículo), C2 (n=3, sem tratamento), T (n=5, tratados com tamoxifeno, 0,3mg/kg/dia), D (n=8, diabéticos experimentais por estreptozotocina, 45mg/Kg) e DT (n=8, diabéticos tratados com tamoxifeno). A eletroforese foi realizada em acetato de celulose, pH 8,6-8,8, cuba TECNOW, e as fitas foram coradas em Ponceau S. As proteínas totais foram determinadas pelo método do Biureto (Kit Labtest). Os proteinogramas foram obtidos em densitômetro BioSystems BTS-235. RESULTADOS: Albumina diminuiu progressivamente nos grupos T, D e DT; a fração a1 aumentou nos grupos T e DT; a fração a2 aumentou nos grupos T e D, havendo efeito aditivo no grupo DT; a fração b aumentou nos grupos T e D; a fração g aumentou nos grupos T, D e DT. CONCLUSÃO: Os resultados indicam uma resposta de fase aguda, com efeito aditivo do tamoxifeno e diabetes, sugerindo uma provável lesão hepática.

Interactions of the stereoisomers of alpha-hydroxytamoxifen with human hydroxysteroid sulfotransferase SULT2A1 and rat hydroxysteroid sulfotransferase STa

Tamoxifen (TAM) is a nonsteroidal antiestrogenic drug that is widely used for the treatment of estrogen receptor-dependent breast cancer. An increased risk of endometrial cancer in some patients treated with TAM has been linked to the metabolic formation of alpha-hydroxytamoxifen (alpha-OHTAM) and its subsequent sulfation. Alpha-OHTAM has been found to be a substrate for rat and human hydroxysteroid sulfotransferases (STa and SULT2A1, respectively). Since stereochemistry plays an important role in the interactions of hydroxysteroid sulfotransferases with their substrates, we have now investigated the interactions of each of the stereoisomers of alpha-OHTAM with highly purified recombinant STa and SULT2A1. Methods for the preparation of the enantiomers of E- and Z-alpha-OHTAM were developed. When each of the four enantiomers was examined with rat STa, E-(+)-alpha-OHTAM was the only substrate for the enzyme, whereas E-(-)-alpha-OHTAM, Z-(+)-alpha-OHTAM, and Z-(-)-alpha-OHTAM were inhibitors of the sulfation of E-(+)-alpha-OHTAM catalyzed by STa. The dissociation constants for the alpha-OHTAM enantiomers indicated that they bound to STa with similar affinity, but only the E-(+)-enantiomer was a substrate. In contrast to the results obtained with rat hydroxysteroid sulfotransferase STa, all enantiomers of alpha-OHTAM were substrates for the human SULT2A1. Moreover, kcat/Km values with SULT2A1 were higher with the Z enantiomers than with the E enantiomers. As a result of the potential for interconversion of the E and Z geometric isomers upon metabolism, the sulfation of the Z isomers may be of greater concern in human tissues than has been previously assumed.

An Hsp27-related, dominant-negative-acting intracellular estradiol-binding protein

New World primates (NWPs) exhibit a compensated form of resistance to gonadal steroid hormones. We demonstrated recently that estrogen resistance in NWP cells was associated with the overexpression of two proteins, a nonreceptor-related, dominant-negative-acting estrogen response element (ERE)-binding protein (ERE-BP) and an intracellular estradiol-binding protein (IEBP). Based on the N-terminal sequences of tryptic fragments of IEBP isolated from a 17beta-estradiol (E2) affinity column we cloned a full-length cDNA for IEBP from the estrogen-resistant NWP cell line, B95-8. Subsequent sequence analysis revealed 87% sequence identity between the deduced peptide for IEBP and human Hsp27. When hormone-responsive, wild-type Old World primate (OWP) cells were transiently transfected with IEBP cDNA, E2-directed ERE reporter luciferase activity was reduced by 50% compared with vector only-transfected OWP cells (p < 0.0018). When IEBP and ERE-BP were cotransfected, ERE promoter-reporter activity was reduced by a further 60% (p < 0.0001). Electrophoresis mobility shift analyses showed that IEBP neither bound to ERE nor competed with the estrogen receptor (ER) for binding to ERE. However, there was evidence of protein-protein interaction of IEBP and ERalpha; IEBP was coimmunoprecipitated with anti-ERalpha antibody in wild-type cells stably transfected with IEBP. A specific interaction between ERalpha and IEBP was confirmed in glutathione S-transferase pull-down and yeast two-hybrid assays. Data indicate that the Hsp27-related IEBP interacts with the ligand binding domain of the ERalpha. In summary, by inhibiting the ERalpha-E2 interaction, IEBP acts to squelch ERalpha-directed ERE-regulated transactivation and promote estrogen resistance in NWP cells.

Cancer prevention and therapy: strategies and problems

During the next years, molecular diagnostic science and the pharmaceutical industry will face increasing demand for personalized medicine. Therapeutic treatments should be tailored to the needs of individual patient. Patients will inquire for information about potential tumor detection at an early stage when disease can be more likely to be arrested or cured with specific regimens of drug therapy. To respond to this demand, science and industry need to modulate therapeutic approaches to the continuous development of cancer. Now more than ever, it is necessary to fill the knowledge hiatus between the "beginning" and the "end" of cancer development, i.e we need to critically analyze the extensive multi-step process of cancer development that still remains poorly understood.

New lytic peptides based on the D,L-amphipathic helix motif preferentially kill tumor cells compared to normal cells

Despite significant advances in cancer therapy, there is an urgent need for drugs with a new mode of action that will preferentially kill cancer cells. Several cationic antimicrobial peptides, which bind strongly to negatively charged membranes, were shown to kill cancer cells slightly better than normal cells. This was explained by a slight increase (3-9%) in the level of the negatively charged membrane phosphatidylserine (PS) in many cancer cells compared to their normal counterparts. Unfortunately, however, these peptides are inactivated by serum components. Here we synthesized and investigated the anticancer activity and the role of peptide charge, peptide structure, and phospholipid headgroup charge on the activity of a new group of diastereomeric lytic peptides (containing D- and L-forms of leucine and lysine; 15-17 amino acids long). The peptides are highly toxic to cancer cells, to a degree similar to or larger than that of mitomycin C. However, compared with mitomycin C and many native antimicrobial peptides, they are more selective for cancer cells. The peptides were investigated for (i) their binding to mono- and bilayer membranes by using the surface plasmon resonance (SPR) technique, (ii) their ability to permeate membranes by using fluorescence spectroscopy, (iii) their structure and their effect on the lipid order by using ATR-FTIR spectroscopy, and (iv) their ability to bind to cancer versus normal cells by using confocal microscopy. The data suggest that the peptides disintegrate the cell membrane in a detergent-like manner. However, in contrast to native antimicrobial peptides, the diastereomers bind and permeate similarly zwitterionic and PS-containing model membranes. Therefore, cell selectivity is probably determined mainly by improved electrostatic attraction of the peptides to acidic components on the surface of cancer cells (e.g., O-glycosylation of mucines). The simple composition of the diastereomeric peptides and their stability regarding enzymatic degradation by serum components make them excellent candidates for new chemotherapeutic drugs.

A novel lytic peptide composed of DL-amino acids selectively kills cancer cells in culture and in mice

The high toxicity of most chemotherapeutic drugs and their inactivation by multidrug resistance phenotypes motivated extensive search for drugs with new modes of action. We designed a short cationic diastereomeric peptide composed of d- and l-leucines, lysines, and arginines that has selective toxicity toward cancer cells and significantly inhibits lung metastasis formation in mice (86%) with no detectable side effects. Its ability to depolarize the transmembrane potential of cancer cells at the same rate (within minutes) and concentration (3 micro m), at which it shows biological activity, suggests a killing mechanism that involves plasma membrane perturbation. Confocal microscopy experiments verified that the cells died as a result of acute injury, swelling, and bursting, suggesting necrosis. Biosensor binding experiments and attenuated total reflectance-Fourier transform infrared spectroscopy using model membranes have substantiated its high selectivity toward cancer cells. Although this is an initial study that looked at tumor formation rather than the ability of the peptides to reduce established tumors, the simple sequence of the peptide, its high solubility, substantial resistance to degradation, and inactivation by serum components might make it a good candidate for future anticancer treatment.

Analysis of the interaction between alpha-1-acid glycoprotein and tamoxifen and its metabolites

Tamoxifen is administered for the treatment of breast cancer; however resistance to therapy is commonplace. Postulated mechanisms of resistance to tamoxifen include altered pharmacology of the drug, changes in the structure and function of the oestrogen receptor and expression of genes that function to support the growth of cells resistant to tamoxifen. However, binding of drugs to proteins found in the plasma is known to affect the efficacy of drugs and alter their distribution. It is already known that tamoxifen is bound 99% to albumin. We investigated the interaction between the plasma protein, alpha-1-acid glycoprotein (AGP), and tamoxifen, since if binding did occur then the free plasma concentration of the drug would be reduced, resulting in the minimum effective concentration of tamoxifen not being attained. Using a recently described intrinsic fluorescence technique for the study of drug-protein interactions, the extent of binding between tamoxifen citrate and AGP was determined. Furthermore, analysis of binding of the known active metabolites of tamoxifen (4-hydroxytamoxifen, N-desmethyltamoxifen, N-desdimethyltamoxifen, cis-alpha-hydroxytamoxifen and trans-alpha-hydroxytamoxifen) to AGP was conducted. Tamoxifen citrate and metabolites were shown to bind AGP, however the level of interaction was low and negligible at the concentration of the drug found in the plasma.