Inhibition of cancer cell proliferation by designed peptide amphiphiles

Supramolecular peptide nano-assemblies for cancer diagnosis and therapy: from molecular design to material synthesis and function-specific applications

Peptide molecule has high bioactivity, good biocompatibility, and excellent biodegradability. In addition, it has adjustable amino acid structure and sequence, which can be flexible designed and tailored to form supramolecular nano-assemblies with specific biomimicking, recognition, and targeting properties via molecular self-assembly. These unique properties of peptide nano-assemblies made it possible for utilizing them for biomedical and tissue engineering applications. In this review, we summarize recent progress on the motif design, self-assembly synthesis, and functional tailoring of peptide nano-assemblies for both cancer diagnosis and therapy. For this aim, firstly we demonstrate the methodologies on the synthesis of various functional pure and hybrid peptide nano-assemblies, by which the structural and functional tailoring of peptide nano-assemblies are introduced and discussed in detail. Secondly, we present the applications of peptide nano-assemblies for cancer diagnosis applications, including optical and magnetic imaging as well as biosensing of cancer cells. Thirdly, the design of peptide nano-assemblies for enzyme-mediated killing, chemo-therapy, photothermal therapy, and multi-therapy of cancer cells are introduced. Finally, the challenges and perspectives in this promising topic are discussed. This work will be useful for readers to understand the methodologies on peptide design and functional tailoring for highly effective, specific, and targeted diagnosis and therapy of cancers, and at the same time it will promote the development of cancer diagnosis and therapy by linking those knowledges in biological science, nanotechnology, biomedicine, tissue engineering, and analytical science.

Oncogenic and tumor suppressor function of MEIS and associated factors

MEIS proteins are historically associated with tumorigenesis, metastasis, and invasion in cancer. MEIS and associated PBX-HOX proteins may act as tumor suppressors or oncogenes in different cellular settings. Their expressions tend to be misregulated in various cancers. Bioinformatic analyses have suggested their upregulation in leukemia/lymphoma, thymoma, pancreas, glioma, and glioblastoma, and downregulation in cervical, uterine, rectum, and colon cancers. However, every cancer type includes, at least, a subtype with high MEIS expression. In addition, studies have highlighted that MEIS proteins and associated factors may function as diagnostic or therapeutic biomarkers for various diseases. Herein, MEIS proteins and associated factors in tumorigenesis are discussed with recent discoveries in addition to how they could be modulated by noncoding RNAs or newly developed small-molecule MEIS inhibitors.

Modulation of Antimicrobial Peptide Conformation and Aggregation by Terminal Lipidation and Surfactants

The function and properties of peptide-based materials depend not only on the amino acid sequence but also on the molecular conformations. In this paper, we chose a series of peptides G_m(XXKK)_nX-NH₂ (m = 0, 3; n = 2, 3; X = I, L, and V) as the model molecules and studied the conformation regulation through N-terminus lipidation and their formulation with surfactants. The structural and morphological transition of peptide self-assemblies have also been investigated via transmission electron microscopy, atomic force microscopy, circular dichroism spectroscopy, and small-angle neutron scattering. With the terminal alkylation, the molecular conformation changed from random coil to β-sheet or α-helix. The antimicrobial activities of alkylated peptide were different. C₁₆-G₃(IIKK)₃I-NH₂ showed antimicrobial activity against Streptococcus mutans, while C₁₆-(IIKK)₂I-NH₂ and C₁₆-G₃(IIKK)₂I-NH₂ did not kill the bacteria. The surfactant sodium dodecyl sulfonate could rapidly induce the self-assemblies of alkylated peptides (C₁₆-(IIKK)₂I-NH₂, C₁₆-G₃(IIKK)₂I-NH₂, C₁₆-G₃(VVKK)₂V-NH₂) from nanofibers to micelles, along with the conformation changing from β-sheet to α-helix. The cationic surfactant hexadecyl trimethyl ammonium bromide made the lipopeptide nanofibers thinner, and nonionic surfactant polyoxyethylene (23) lauryl ether (C₁₂EO₂₃) induced the nanofibers much more intensively. Both the activity and the conformation of the α-helical peptide could be modulated by lipidation. Then, the self-assembled morphologies of alkylated peptides could also be further regulated with surfactants through hydrophobic, electrostatic, and hydrogen-bonding interactions. These results provided useful strategies to regulate the molecular conformations in peptide-based material functionalization.

PBX3 hypermethylation in peripheral blood leukocytes predicts better prognosis in colorectal cancer: A propensity score analysis

OBJECTIVE

The significance of gene methylation in peripheral blood leukocytes (PBLs) for assessing cancer prognosis is poorly understood. Our purpose is to assess the association between PBX3 methylation in PBLs and colorectal cancer (CRC) prognosis.

METHODS

A total of 369 CRC patients were followed up for up to 10 years in this cohort study. PBL PBX3 methylation levels were determined by methylation-sensitive high-resolution melting. Cox regression models and Log-rank tests were used to analyze the associations between PBX3 methylation status and CRC prognosis with a propensity score (PS) method to control confounding biases.

RESULTS

In this study, we found that CRC patients with PBL PBX3 hypermethylation status had a better overall survival (OS) (hazard ratio [HR_PS-adjusted ], 0.72 [95% CI, 0.52-1.00]; P = 0.049). Subgroup analyses showed that the beneficial effect of PBX3 hypermethylation status on CRC 10-years OS remained significant among UICC stage III patients ([HR_PS-adjusted ], 0.60 [95% CI, 0.38 to 0.95]; P = 0.029) and colon cancer patients ([HR_PS-adjusted ], 0.49 [95% CI, 0.26 to 0.92]; P = 0.027).

CONCLUSION

PBL PBX3 hypermethylation is positively associated with better prognosis of CRC, especially for the UICC stage III CRC patients and colon cancer patients.

Aptamer-displaying peptide amphiphile micelles as a cell-targeted delivery vehicle of peptide cargoes

Peptide amphiphile micelles (PAMs) are attractive vehicles for the delivery of a variety of therapeutic and prophylactic peptides. However, a key limitation of PAMs is their lack of preferential targeting ability. In this paper, we describe our design of a PAM system that incorporates a DNA oligonucleotide amphiphile (antitail amphiphile-AA) to form A/PAMs. A cell-targeting DNA aptamer with a 3' extension sequence (tail) complementary to the AA is annealed to the surface to form aptamer-displaying PAMs (Aptamer~A/PAMs). Aptamer~A/PAMs are small, anionic, stable nanoparticles capable of delivering a large mass percentage peptide amphiphile (PA) compared to targeting DNA components. Aptamer~A/PAMs are stable for over 4 h in the presence of biological fluids. Additionally, the aptamer retains its cell-targeting properties when annealed to the A/PAM, thus leading to enhanced delivery to a specifically-targeted B-cell leukemia cell line. This exciting modular technology can be readily used with a library of different targeting aptamers and PAs, capable of improving the bioavailability and potency of the peptide cargo.

A hydrophobic residue in the TALE homeodomain of PBX1 promotes epithelial-to-mesenchymal transition of gastric carcinoma

Pre-B-cell leukemia homeobox 1 (PBX1) was originally identified as a proto-oncogene in human leukemia. Although this protein has been shown to contribute to cellular development and tumorigenesis, the role of PBX1 in gastric carcinoma (GC) remains unclear. In this study, we observed increased expression of PBX1 in GC tissues compared with adjacent normal tissues. This increase in PBX1 expression levels negatively correlated with HOXB9 mRNA expression and was also associated with malignancy and metastasis. PBX1 promoted proliferation and metastasis of GC cells both in vitro and in vivo. These phenomena were also accompanied by epithelial-to-mesenchymal transition (EMT). Additionally, we observed that PBX1 promotes the expression of tumor growth and angiogenic factors. A structural model of the PBX1-HOX complex revealed that hydrophobic binding between PBX1 and the hexapeptide motif might be required for EMT induction. This analysis also demonstrated that the Phe²⁵² residue in the first helix of the TALE homeodomain is involved in the latter hydrophobic binding reaction. In vitro data from PBX1 mutants suggest that PBX1 cannot promote tumorigenesis of GC cells via EMT induction when Phe²⁵² residues lose hydrophobicity. It is likely that the presence of this residue is essential in facilitating hydrophobic binding with the hexapeptide motif. These findings suggest that PBX1 may be a potential target for GC treatment and this study provides a platform to elucidate the molecular mechanisms that underpin the role of PBX1 in GC tumorigenesis.

PBX3 promotes gastric cancer invasion and metastasis by inducing epithelial-mesenchymal transition

The overexpression of pre-leukemia transcription factor 3 (PBX3) in tumors plays an important role in invasion, metastasis and proliferation in a variety of human cancer types. Tumor metastasis and angiogenesis significantly contribute to the progression of cancer and create challenges for cancer therapy. In the present study, reverse transcription-polymerase chain reaction demonstrated that PBX3 was upregulated in gastric cancer (GC) tissues and Transwell assay revealed that the overexpression of PBX3 promoted GC invasion and metastasis in vitro. In addition, a nude mouse xenograft model was established, which demonstrated that PBX3 promoted peritoneal metastases in vivo. Furthermore, the overexpression of PBX3 in GC promoted the tubular formation of human umbilical vein endothelial cells. Western blot analysis revealed that overexpressed PBX3 induced epithelial-mesenchymal transition (EMT) in GC, as measured by increases in the EMT protein markers N-cadherin and vimentin, while E-cadherin expression was reduced in PBX3-overexpressing GC cells. Contrasting results were observed in PBX3-knockdown GC cells. Additionally, the overexpression of PBX3 increased the levels of phosphorylated AKT (Ser473), which is involved in the progression of a variety of human cancers. Gelatin zymography assay demonstrated that the overexpression of PBX3 also elevated matrix metalloproteinase-9 activity in GC, which was closely associated with tumor metastasis and angiogenesis. Based on these findings, it may be concluded that PBX3 enhances invasion and metastasis in GC by promoting EMT, possibly via the AKT signaling pathway.

HOXB9 induction of mesenchymal-to-epithelial transition in gastric carcinoma is negatively regulated by its hexapeptide motif

HOXB9, a transcription factor, plays an important role in development. While HOXB9 has been implicated in tumorigenesis and metastasis, its mechanisms are variable and its role in gastric carcinoma (GC) remains unclear. In the present study, we demonstrated that the expression of HOXB9 decreased in gastric carcinoma and was associated with malignancy and metastasis. Re-expression of HOXB9 in gastric cell lines resulted in the suppression of cell proliferation, migration, and invasion, which was accompanied by the induction of mesenchymal-to-epithelial transition (MET). Comparative sequence analysis and examination of a HOXB9 structural model indicated that three sites might possibly be involved in MET regulation. The in vitro study of HOXB9 mutants showed that these were unable to inhibit MET induction. However, when overexpressing a HOXB9 mutant lacking the hexapeptide motif, a more potent MET induction and tumor suppression was observed compared to that of the wild-type, indicating that the presence of the hexapeptide motif reduced HOXB9 MET induction and tumor suppression activity. Therefore, the results of the present study suggested that HOXB9 is a tumor suppressor in gastric carcinoma, and its activity was controlled by different regulatory mechanisms such as the hexapeptide motif as a "brake" in this case. The results of these regulatory effects could lead to either oncogenic or tumor suppressive roles of HOXB9, depending on the context of the particular type of cancer involved.

Peptide Amphiphiles in Corneal Tissue Engineering

The increasing interest in effort towards creating alternative therapies have led to exciting breakthroughs in the attempt to bio-fabricate and engineer live tissues. This has been particularly evident in the development of new approaches applied to reconstruct corneal tissue. The need for tissue-engineered corneas is largely a response to the shortage of donor tissue and the lack of suitable alternative biological scaffolds preventing the treatment of millions of blind people worldwide. This review is focused on recent developments in corneal tissue engineering, specifically on the use of self-assembling peptide amphiphiles for this purpose. Recently, peptide amphiphiles have generated great interest as therapeutic molecules, both in vitro and in vivo. Here we introduce this rapidly developing field, and examine innovative applications of peptide amphiphiles to create natural bio-prosthetic corneal tissue in vitro. The advantages of peptide amphiphiles over other biomaterials, namely their wide range of functions and applications, versatility, and transferability are also discussed to better understand how these fascinating molecules can help solve current challenges in corneal regeneration.

Surfactant-induced assembly of enzymatically-stable peptide hydrogels

The secondary structure of peptides in the presence of interacting additives is an important topic of study, having implications in the application of peptide science to a broad range of modern technologies. Surfactants constitute a class of biologically relevant compounds that are known to influence both peptide conformation and aggregation or assembly. We have characterized the secondary structure of a linear nonapeptide composed of a hydrophobic alanine/phenylalanine core flanked by hydrophilic acid/amine units. We show that the anionic surfactant sodium dodecyl sulfate (SDS) induces the formation of β-sheets and macroscopic gelation in this otherwise unstructured peptide. Through comparison to related additives, we propose that SDS-induced secondary structure formation is the result of amphiphilicity created by electrostatic binding of SDS to the peptide. In addition, we demonstrate a novel utility of surfactants in manipulating and stabilizing peptide nanostructures. SDS is used to simultaneously induce secondary structure in a peptide and to inhibit the activity of a model enzyme, resulting in a peptide hydrogel that is impervious to enzymatic degradation. These results complement our understanding of the behavior of peptides in the presence of interacting secondary molecules and provide new potential pathways for programmable organization of peptides by the addition of such components.

Pbx3 and Meis1 cooperate through multiple mechanisms to support Hox-induced murine leukemia

Hox homeobox transcription factors drive leukemogenesis efficiently only in the presence of Meis or Pbx proteins. Here we show that Pbx3 and Meis1 need to dimerize to support Hox-induced leukemia and we analyze the molecular details of this cooperation. In the absence of Pbx3, Meis1 was highly unstable. As shown by a deletion analysis Meis1 degradation was contingent on a motif coinciding with the Pbx-binding domain. Either deletion of this sequence or binding to Pbx3 prolonged the half-life of Meis1 by preventing its ubiquitination. Meis1 break-down could also be blocked by inhibition of the ubiquitin proteasome system, indicating tight post-transcriptional control. In addition, Meis1 and Pbx3 cooperated genetically as overexpression of Pbx3 induced endogenous Meis1 transcription. These functional interactions translated into in vivo activity. Blocking Meis1/Pbx3 dimerization abrogated the ability to enhance proliferation and colony-forming cell numbers in primary cells transformed by Hoxa9. Furthermore, expression of Meis1 target genes Flt3 and Trib2 was dependent on Pbx3/Meis1 dimerization. This correlated with the requirement of Meis1 to bind Pbx3 in order to form high affinity DNA/Hoxa9/Meis1/Pbx3 complexes in vitro. Finally, kinetics and severity of disease in transplantation assays indicated that Pbx3/Meis1 dimers are rate-limiting factors for Hoxa9-induced leukemia.

Stimuli-responsive self-assembling peptides made from antibacterial peptides

How to use bioactive peptide sequences as fundamental building blocks to make hydrogel materials which are stimuli-responsive? In this article, we provide a novel designed peptide comprising two antibacterial peptide sequences (KIGAKI)3-NH2 and a central tetrapeptide linker. Results show that balancing the forces of the electrostatic repulsion of the charged lysine residues against the hydrophobic collapse of the isoleucine and alanine residues and backbone β-sheet hydrogen bonding allows the structural transition and formation of individually dispersed nanofibers. Circular Dichroism (CD) and rheology analysis demonstrated that the designed peptide can undergo an abrupt structural transition from a random coil to a stable unimolecular β-hairpin conformation and subsequently form an elastic hydrogel when exposed to external stimuli such as pH, ionic strength and heat. The assembly kinetics of the obtained antibacterial sequence comprising peptide (ASCP) was studied by time-lapse Atomic Force Microscopy (AFM) and Thioflavin T (ThT) binding assay. In addition, the inherent antibacterial activity of the peptide hydrogel was confirmed by the antibacterial assay against Escherichia coli. This example described epitomizes the use of bioactive peptide sequences in the design of finite self-assembled structures with potential inherent activity. These hydrogel materials may find applications in drug delivery, tissue engineering and regenerative medicine.

Structure and flexibility of nanoscale protein cages designed by symmetric self-assembly

Designing protein molecules that self-assemble into complex architectures is an outstanding goal in the area of nanobiotechnology. One design strategy for doing this involves genetically fusing together two natural proteins, each of which is known to form a simple oligomer on its own (e.g., a dimer or trimer). If two such components can be fused in a geometrically predefined configuration, that designed subunit can, in principle, assemble into highly symmetric architectures. Initial experiments showed that a 12-subunit tetrahedral cage, 16 nm in diameter, could be constructed following such a procedure [Padilla, J. E.; et al. Proc. Natl. Acad. Sci. U.S.A. 2001, 98, 2217; Lai, Y. T.; et al. Science 2012, 336, 1129]. Here we characterize multiple crystal structures of protein cages constructed in this way, including cages assembled from two mutant forms of the same basic protein subunit. The flexibilities of the designed assemblies and their deviations from the target model are described, along with implications for further design developments.

Genome-wide reprogramming of the chromatin landscape underlies endocrine therapy resistance in breast cancer

The estrogen receptor (ER)α drives growth in two-thirds of all breast cancers. Several targeted therapies, collectively termed endocrine therapy, impinge on estrogen-induced ERα activation to block tumor growth. However, half of ERα-positive breast cancers are tolerant or acquire resistance to endocrine therapy. We demonstrate that genome-wide reprogramming of the chromatin landscape, defined by epigenomic maps for regulatory elements or transcriptional activation and chromatin openness, underlies resistance to endocrine therapy. This annotation reveals endocrine therapy-response specific regulatory networks where NOTCH pathway is overactivated in resistant breast cancer cells, whereas classical ERα signaling is epigenetically disengaged. Blocking NOTCH signaling abrogates growth of resistant breast cancer cells. Its activation state in primary breast tumors is a prognostic factor of resistance in endocrine treated patients. Overall, our work demonstrates that chromatin landscape reprogramming underlies changes in regulatory networks driving endocrine therapy resistance in breast cancer.

The prolactin receptor mediates HOXA1-stimulated oncogenicity in mammary carcinoma cells

The HOX genes are a highly conserved subgroup of homeodomain-containing transcription factors that are crucial to normal development. Forced expression of HOXA1 results in oncogenic transformation of immortalized human mammary cells with aggressive tumour formation in vivo. Microarray analysis identified that the prolactin receptor (PRLR) was significantly upregulated by forced expression of HOXA1 in mammary carcinoma cells. To determine prolactin (PRL) involvement in HOXA1‑induced oncogenicity in mammary carcinoma cells (MCF-7), we examined the effect of human prolactin (hPRL)-initiated PRLR signal transduction on changes in cellular behaviour mediated by HOXA1. Forced expression of HOXA1 in MCF-7 cells increased PRLR mRNA and protein expression. Forced expression of HOXA1 also enhanced hPRL-stimulated phosphorylation of both STAT5A/B and p44/42 MAPK, and increased subsequent transcriptional activity of STAT5A and STAT5B, and Elk-1 and Sap1a, respectively. Moreover, forced expression of HOXA1 in MCF-7 cells enhanced the hPRL‑stimulated increase in total cell number as a consequence of enhanced cell proliferation and cell survival, and also enhanced hPRL-stimulated anchorage-independent growth in soft agar. Increased anchorage-independent growth was attenuated by the PRLR antagonist ∆1-9-G129R‑hPRL. In conclusion, we have demonstrated that HOXA1 increases expression of the cell surface receptor PRLR and enhances PRLR-mediated signal transduction. Thus, the PRLR is one mediator of HOXA1‑stimulated oncogenicity in mammary carcinoma cells.

MicroRNA-196a promotes non-small cell lung cancer cell proliferation and invasion through targeting HOXA5

BACKGROUND

MicroRNAs (miRNAs) are short, non-coding RNAs (~22 nt) that play important roles in the pathogenesis of human diseases by negatively regulating gene expression. Although miR-196a has been implicated in several other cancers, its role in non-small cell lung cancer (NSCLC) is unknown. The aim of the present study was to examine the expression pattern of miR-196a in NSCLC and its clinical significance, as well as its biological role in tumor progression.

METHODS

Expression of miR-196a was analyzed in 34 NSCLC tissues and five NSCLC cell lines by quantitative reverse-transcription polymerase chain reaction (qRT-PCR). The effect of DNA methylation on miR-196a expression was investigated by 5-aza-2-deoxy-cytidine treatment and bisulfite sequencing. The effect of miR-196a on proliferation was evaluated by MTT and colony formation assays, and cell migration and invasion were evaluated by transwell assays. Analysis of target protein expression was determined by western blotting. Luciferase reporter plasmids were constructed to confirm the action of miR-196a on downstream target genes, including HOXA5. Differences between the results were tested for significance using Student's t-test (two-tailed).

RESULTS

miR-196a was highly expressed both in NSCLC samples and cell lines compared with their corresponding normal counterparts, and the expression of miR-196a may be affected by DNA demethylation. Higher expression of miR-196a in NSCLC tissues was associated with a higher clinical stage, and also correlated with NSCLC lymph-node metastasis. In vitro functional assays demonstrated that modulation of miR-196a expression affected NSCLC cell proliferation, migration and invasion. Our analysis showed that miR-196a suppressed the expression of HOXA5 both at the mRNA and protein levels, and luciferase assays confirmed that miR-196a directly bound to the 3'untranslated region of HOXA5. Knockdown of HOXA5 expression in A549 cells using RNAi was shown to promote NSCLC cell proliferation, migration and invasion. Finally, we observed an inverse correlation between HOXA5 and miR-196a expression in NSCLC tissues.

CONCLUSIONS

Our findings indicate that miR-196a is significantly up-regulated in NSCLC tissues, and regulates NSCLC cell proliferation, migration and invasion, partially via the down-regulation of HOXA5. Thus, miR-196a may represent a potential therapeutic target for NSCLC intervention.

A Peptide-Based Material for Therapeutic Carbon Monoxide Delivery

We report on the preparation of the first material for therapeutic delivery of CO. A peptide amphiphile was synthesized with a covalently attached ruthenium tricarbonyl. Self-assembled nanofiber gels containing this peptide spontaneously released CO with prolonged release kinetics compared to soluble CO donors. Oxidatively stressed cardiomyocytes had improved viability when treated with this peptide, demonstrating its potential as a biodegradable gel for localized therapeutic CO delivery.

Self-assembling peptide scaffolds for regenerative medicine

Biomaterials made from self-assembling, short peptides and peptide derivatives have great potential to generate powerful new therapies in regenerative medicine. The high signaling capacity and therapeutic efficacy of peptidic scaffolds has been established in several animal models, and the development of more complex, hierarchical structures based on peptide materials is underway. This highlight discusses several classes of self-assembling peptide-based materials, including peptide amphiphiles, Fmoc-peptides, self-complementary ionic peptides, hairpin peptides, and others. The self-assembly designs, bioactive signalling strategies, and cell signalling capabilities of these bioactive materials are reported. The future challenges of the field are also discussed, including short-term goals such as integration with biopolymers and traditional implants, and long term goals, such as immune system programming, subcellular targeting, and the development of highly integrated scaffold systems.

The Pbx interaction motif of Hoxa1 is essential for its oncogenic activity

Hoxa1 belongs to the Hox family of homeodomain transcription factors involved in patterning embryonic territories and governing organogenetic processes. In addition to its developmental functions, Hoxa1 has been shown to be an oncogene and to be overexpressed in the mammary gland in response to a deregulation of the autocrine growth hormone. It has therefore been suggested that Hoxa1 plays a pivotal role in the process linking autocrine growth hormone misregulation and mammary carcinogenesis. Like most Hox proteins, Hoxa1 can interact with Pbx proteins. This interaction relies on a Hox hexapeptidic sequence centred on conserved Tryptophan and Methionine residues. To address the importance of the Hox-Pbx interaction for the oncogenic activity of Hoxa1, we characterized here the properties of a Hoxa1 variant with substituted residues in the hexapeptide and demonstrate that the Hoxa1 mutant lost its ability to stimulate cell proliferation, anchorage-independent cell growth, and loss of contact inhibition. Therefore, the hexapeptide motif of Hoxa1 is required to confer its oncogenic activity, supporting the view that this activity relies on the ability of Hoxa1 to interact with Pbx.

Pioneer factors: directing transcriptional regulators within the chromatin environment

Chromatin is a well-known obstacle to transcription as it controls DNA accessibility, which directly impacts the recruitment of the transcriptional machinery. The recent burst of functional genomic studies provides new clues as to how transcriptional competency is regulated in this context. In this review, we discuss how these studies have shed light on a specialized subset of transcription factors, defined as pioneer factors, which direct recruitment of downstream transcription factors to establish lineage-specific transcriptional programs. In particular, we present evidence of an interplay between pioneer factors and the epigenome that could be central to this process. Finally, we discuss how pioneer factors, whose expression and function are altered in tumors, are also being considered for their prognostic value and should therefore be regarded as potential therapeutic targets. Thus, pioneer factors emerge as key players that connect the epigenome and transcription in health and disease.

Materials from peptide assembly: towards the treatment of cancer and transmittable disease

As the prevalence of cancer and transmittable disease persists, the development of new and more advanced therapies remains a priority in medical research. An emerging platform for the treatment of these illnesses is the use of materials formed via peptide assembly where the bulk material itself acts as the therapeutic. Higher ordered peptide structures with defined chemistry are capable of cellular targeting, recognition, and internalization. Recent design efforts are being made to exploit the nanoscale definition of the materials formed by assembling peptides to target cancer and microbial cells and to function as vaccines. This review focuses on assembled peptide materials that actively participate in the biological processes important to cancer and transmittable diseases to exert an anticipated functional outcome.

Regulation of PBX3 expression by androgen and Let-7d in prostate cancer

Background

The pre-leukemia transcription factor 3 (PBX) is part of the PBX family of transcription factors, which is known to regulate genes involved in differentiation of urogenital organs and steroidogenesis. This is of interest with regard to prostate cancer progression as regulation of steroidogenesis is one of the mechanisms involved in the development of castration-resistant prostate cancer. In light of this we wanted to investigate the possible involvement of androgen regulation of PBX3 expression in prostate cancer.

Results

In this study, we show that PBX3 is post-transcriptionally regulated by androgen in prostate cancer cells and that the effect might be independent of the androgen receptor. Furthermore, PBX3 was identified as a target of Let-7d, an androgen regulated microRNA. Let-7d was down-regulated in malignant compared to benign prostate tissue, whereas up-regulation of PBX3 expression was observed.

Conclusions

We demonstrate that PBX3 is up-regulated in prostate cancer and post- transcriptionally regulated by androgen through Let-7d.

De novo designed peptides for biological applications

In recent years our ability to design and assemble peptide-based materials and objects de novo (i.e. from first principles) has improved considerably. This brings us to a point where the resulting assemblies are quite sophisticated and amenable to engineering in new functions. Whilst such systems could be used in a variety of ways, biological applications are of particular interest because of the demand for biocompatible, readily produced systems with potential as drug-delivery agents, components of biosensors and scaffolds for 3D cell and tissue culture. This tutorial review describes the building blocks (or tectons) that are being used in peptide assembly, highlights a range of materials and objects that have been produced, notably hydrogels and virus-like particles, and introduces a number of potential applications for the designs.

DNA replication, development and cancer: a homeotic connection?

The homeotic proteins are transcription factors, highly conserved in metazoan organisms, exerting a pivotal role in development and differentiation. They individually display a loose specificity for the DNA sequence they can bind, but operate mainly in multi-molecular associations that assure their target and function specificity. Homeotic proteins are known to play a role in the positive or negative regulation of cell proliferation. Furthermore, many homeotic proteins are actually proto-oncogenes, since different translocations involving their genes cause tumors, particularly in the hematopoietic system. A one-hybrid screen to detect proteins with affinity for the lamin B2 replication origin identified three homeotic proteins, namely HoxA13, HoxC10 and HoxC13. Recent data demonstrate that the HoxC13 oncoprotein specifically associates with replication foci and binds in vitro and in vivo to several human DNA replication origins. Moreover, Hox proteins interact with geminin, a regulator of cell cycle progression, and control the interaction of this protein with the DNA replication licensing factor Ctd1. Thus, the homeotic proteins, by participating directly in the function of DNA replication origins, may provide a direct link between the accurate regulation of DNA replication required by the morphogenetic program and the deregulation of this process typical of cancer.

Induction of cancer cell death by self-assembling nanostructures incorporating a cytotoxic peptide

Nanotechnology offers novel delivery vehicles for cancer therapeutics. Potential advantages of nanoscale platforms include improved pharmacokinetics, encapsulation of cytotoxic agents, enhanced accumulation of therapeutics in the tumor microenvironment, and improved therapeutic structures and bioactivity. Here, we report the design of a novel amphiphilic molecule that self-assembles into nanostructures for intracellular delivery of cytotoxic peptides. Specifically, a cationic alpha-helical (KLAKLAK)(2) peptide that is known to induce cancer cell death by membrane disruption was integrated into a peptide amphiphile (PA) that self-assembles into bioactive, cylindrical nanofibers. PAs are composed of a hydrophobic alkyl tail, a beta-sheet forming peptide, and a bioactive peptide that is displayed on the surface of the nanofiber after self-assembly. PA nanostructures that included (KLAKLAK)(2) were readily internalized by breast cancer cells, in contrast to the (KLAKLAK)(2) peptide that on its own was not cell permeable. (KLAKLAK)(2) nanostructures, but not the peptides alone, also induced breast cancer cell death by caspase-independent and Bax/Bak-independent mechanisms associated with membrane disruption. Significantly, (KLAKLAK)(2) nanostructures induced cell death more robustly in transformed breast epithelial cells than in untransformed cells, suggesting a degree of tumor selectivity. Our results provide proof-of-principle that self-assembling PAs can be rationally designed to generate nanostructures that can efficiently deliver cytotoxic peptides to cancer cells.