Rational development of a cytotoxic peptide to trigger cell death

CD74-AKT Axis Is a Potential Therapeutic Target in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) cells are often resistant to FAS (CD95)-mediated apoptosis, but the underlying molecular mechanism(s) is not fully understood yet. Notably, the expression of the type II transmembrane protein, CD74, is correlated with chemotherapy-resistant and more invasive forms of cancers via unknown mechanisms. Here, we analyzed gene expression pattern of cancer patients and/or patient-derived xenograft (PDX) models and found that mRNA and protein levels of CD74 are highly expressed in TNBC and correlated with cancer stem cells (CSCs) and epithelial-mesenchymal transition (EMT) properties. Mechanistically, we found that AKT activation is likely critical for maintaining CD74 expression and protein stability to favor its oncogenic functions. Physiologically, epidermal growth factor (EGF) along with CD74 could activate AKT signaling, likely through binding of phosphorylated AKT (S473) to CD74, whereas inhibition of AKT could impair stability of CD74. We also revealed that CD74 binds to FAS and interferes with the intrinsic signaling of FAS-mediated apoptosis. As such, selective targeting of the CD74/FAS complex using the AKT inhibitor along with the CD74-derived peptide could synergistically restore and activate FAS-mediated apoptosis. Therefore, our approach of mobilizing apoptosis pathways likely provides a rationale for TNBC treatment by targeting the CD74/FAS and CD74-AKT axes.

Chaperonin containing TCP-1 (CCT/TRiC) is a novel therapeutic and diagnostic target for neuroblastoma

Chaperonin containing TCP1 (CCT/TRiC) is a multi-subunit protein folding complex that enables the cancer phenotype to emerge from the mutational landscape that drives oncogenesis. We and others linked increased expression of CCT subunits to advanced tumor stage and invasiveness that inversely correlates with cancer patient outcomes. In this study, we examined the expression of the second CCT subunit, CCT2, using genomic databases of adult and pediatric tumors and normal tissues, and found that it was highly expressed in pediatric cancers, showing a significant difference compared to normal tissues. Histologic staining confirmed that CCT subunits are highly expressed in tumor tissues, which was exemplified in neuroblastoma. Using two neuroblastoma cells, MYCN-amplified, IMR-32 cells, and non-amplified, SK-N-AS cells, we assessed baseline levels for CCT subunits and found expressions comparable to the highly invasive triple-negative breast cancer (TNBC) cell line, MDA-MB-231. Exogenous expression of CCT2 in both SK-N-AS and IMR-32 cells resulted in morphological changes, such as larger cell size and increased adherence, with significant increases in the CCT substrates, actin, and tubulin, as well as increased migration. Depletion of CCT2 reversed these effects and reduced cell viability. We evaluated CCT as a therapeutic target in IMR-32 cells by testing a novel peptide CCT inhibitor, CT20p. Treatment with CT20p induced cell death in these neuroblastoma cells. The use of CCT2 as a biological indicator for detection of neuroblastoma cells shed in blood was examined by spiking IMR-32 cells into human blood and using an anti-CCT2 antibody for the identification of spiked cancer cells with the CellSearch system. Results showed that using CCT2 for the detection of neuroblastoma cells in blood was more effective than the conventional approach of using epithelial markers like cytokeratins. CCT2 plays an essential role in promoting the invasive capacity of neuroblastoma cells and thus offers the potential to act as a molecular target in the development of novel therapeutics and diagnostics for pediatric cancers.

Peptide Aggregation Induced Immunogenic Rupture (PAIIR)

Immunogenic cell death (ICD) arises when cells are under stress, and their membranes are damaged. They release damage-associated molecular patterns (DAMPs) that stimulate and drive the type and magnitude of the immune response. In the presence of an antigen, DAMPs ride the longevity and efficacy of antigen-specific immunity. Yet, no tool can induce the controlled ICD with predictable results. A peptide-based tool, [II], is designed that aggregates in the cell and causes cell membrane damage, generates ICD and DAMPs release on various cell types, and hence can act as an adjuvant. An influenza vaccine is prepared by combining [II] with influenza hemagglutinin (HA) subunit antigens. The results show that [II] induced significantly higher HA-specific immunoglobulin G1 (IgG1) and IgG2a antibodies than HA-only immunized mice, while the peptide itself did not elicit antibodies. This paper demonstrates the first peptide-aggregation induced immunogenic rupture (PAIIR) approach as a vaccine adjuvant. PAIIR is a promising adjuvant with a high potential to promote universal protection upon influenza HA vaccination.

The dual interaction of antimicrobial peptides on bacteria and cancer cells; mechanism of action and therapeutic strategies of nanostructures

Microbial infection and cancer are two leading causes of global mortality. Discovering and developing new therapeutics with better specificity having minimal side-effects and no drug resistance are of an immense need. In this regard, cationic antimicrobial peptides (AMP) with dual antimicrobial and anticancer activities are the ultimate choice. For better efficacy and improved stability, the AMPs available for treatment still required to be modified. There are several strategies in which AMPs can be enhanced through, for instance, nano-carrier application with high selectivity and specificity enables researchers to estimate the rate of drug delivery to a particular tissue. In this review we present the biology and modes of action of AMPs for both anticancer and antimicrobial activities as well as some modification strategies to improve the efficacy and selectivity of these AMPs.

The TRiCky Business of Protein Folding in Health and Disease

Maintenance of the cellular proteome or proteostasis is an essential process that when deregulated leads to diseases like neurological disorders and cancer. Central to proteostasis are the molecular chaperones that fold proteins into functional 3-dimensional (3D) shapes and prevent protein aggregation. Chaperonins, a family of chaperones found in all lineages of organisms, are efficient machines that fold proteins within central cavities. The eukaryotic Chaperonin Containing TCP1 (CCT), also known as Tailless complex polypeptide 1 (TCP-1) Ring Complex (TRiC), is a multi-subunit molecular complex that folds the obligate substrates, actin, and tubulin. But more than folding cytoskeletal proteins, CCT differs from most chaperones in its ability to fold proteins larger than its central folding chamber and in a sequential manner that enables it to tackle proteins with complex topologies or very large proteins and complexes. Unique features of CCT include an asymmetry of charges and ATP affinities across the eight subunits that form the hetero-oligomeric complex. Variable substrate binding capacities endow CCT with a plasticity that developed as the chaperonin evolved with eukaryotes and acquired functional capacity in the densely packed intracellular environment. Given the decades of discovery on the structure and function of CCT, much remains unknown such as the scope of its interactome. New findings on the role of CCT in disease, and potential for diagnostic and therapeutic uses, heighten the need to better understand the function of this essential molecular chaperone. Clues as to how CCT causes cancer or neurological disorders lie in the early studies of the chaperonin that form a foundational knowledgebase. In this review, we span the decades of CCT discoveries to provide critical context to the continued research on the diverse capacities in health and disease of this essential protein-folding complex.

Correlation between the secondary structure and surface activity of β-sheet forming cationic amphiphilic peptides and their anticancer activity

Cancer is one of the main causes of death worldwide. The current cancer treatment strategies often lack selectivity for cancer cells resulting in dose-limiting adverse effects and reduced quality of life. Recently, anticancer peptides (ACPs) have emerged as an alternative treatment with higher selectivity, less adverse effects, and lower propensity for drug resistance. However, most of the current studies on the ACPs are focused on α-helical ACPs and there is lack of systematic studies on β-sheet forming ACPs. Herein we report the development of a new series of rationally designed short cationic amphiphilic β-sheet forming ACPs and their structure activity relationship. The peptides had the general formula (XY1XY2)3, with X representing hydrophobic amino acids (isoleucine (I) or leucine (L)), Y1 and Y2 representing cationic amino acids (arginine (R) or lysine (K)). The cytotoxicity of the designed ACPs in HCT 116 colorectal cancer, HeLa cervical cancer and human dermal fibroblast (HDF) cells was assessed by MTT test. The physicochemical properties of the peptides were characterized by various techniques including RP-HPLC, LC-MS, and Circular Dichroism (CD) spectroscopy. The surface activity of the peptides at the air-water interface and their interaction with the lipid monolayers as models for cell membranes were studied by Langmuir trough. The peptides consisting of I with R and K had selective anticancer activity while the combination of L and R diminished the anticancer activity of the peptides but rendered them more toxic to HDFs. The anticancer activity of the peptides was directed by their surface activity (amphiphilicity) and their secondary structure in hydrophobic surfaces including cancer cell membranes. The selectivity of the peptides for cancer cells was a result of their higher penetration into cancer cell membranes compared to normal cell membranes. The peptides exerted their anticancer activity by disrupting the mitochondrial membranes and eventually apoptosis. The results presented in this study provide an insight into the structure-activity relationship of this class of ACPs which can be employed as guidance to design new ACPs with improved anticancer activity and lower toxicity against normal cells.

Advancement and Strategies for the Development of Peptide-Drug Conjugates: Pharmacokinetic Modulation, Role and Clinical Evidence Against Cancer Management

Currently, many new treatment strategies are being used for the management of cancer. Among them, chemotherapy based on peptides has been of great interest due to the unique features of peptides. This review discusses the role of peptide and peptides analogues in the treatment of cancer, with special emphasis on their pharmacokinetic modulation and research progress. Low molecular weight, targeted drug delivery, enhanced permeability, etc., of the peptide-linked drug conjugates, lead to an increase in the effectiveness of cancer therapy. Various peptides have recently been developed as drugs and vaccines with an altered pharmacokinetic parameter which has subsequently been assessed in different phases of the clinical study. Peptides have made a great impact in the area of cancer therapy and diagnosis. Targeted chemotherapy and drug delivery techniques using peptides are emerging as excellent tools in minimizing problems with conventional chemotherapy. It can be concluded that new advances in using peptides to treat different types of cancer have been shown by different clinical studies indicating that peptides could be used as an ideal therapeutic method in treating cancer due to the novel advantages of peptides. The development of identifying and synthesizing novel peptides could provide a promising choice to patients with cancer.

Multiple strategies for the treatment of invasive breast carcinoma: A comprehensive prospective

In this review, we emphasize on evolving therapeutic strategies and advances in the treatment of breast cancer (BC). This includes small-molecule inhibitors under preclinical and clinical investigation, phytoconstituents with antiproliferative potential, targeted therapies as antibodies and antibody-drug conjugates (ADCs), vaccines as immunotherapeutic agents and peptides as a novel approach inhibiting the interaction of oncogenic proteins. We provide an update of molecules under different phases of clinical investigation which aid in the identification of loopholes or shortcomings that can be overcomed with future breast cancer research.

Antitumorigenic effect of insect-derived peptide poecilocorisin-1 in human skin cancer cells through regulation of Sp1 transcription factor

Malignant melanoma is highly resistant to conventional treatments and is one of the most aggressive types of skin cancers. Conventional cancer treatments are limited due to drug resistance, tumor selectivity, and solubility. Therefore, new treatments with fewer side effects and excellent effects should be developed. In previous studies, we have analyzed antimicrobial peptides (AMPs), which showed antibacterial and anti-inflammatory effects in insects, and some AMPs also exhibited anticancer efficacy. Anticancer peptides (ACPs) are known to have fewer side effects and high anticancer efficacy. In this study, the insect-derived peptide poecilocorisin-1 (PCC-1) did not induce toxicity in the human epithelial cell line HaCaT, but its potential as an anticancer agent was confirmed through specific effects of antiproliferation, apoptosis, and cell cycle arrest in two melanoma cell lines, SK-MEL-28 and G361. Additionally, we discovered a novel anticancer mechanism of insect-derived peptides in melanoma through the regulation of transcription factor Sp1 protein, which is overexpressed in cancer, apoptosis, and cell cycle-related proteins. Taken together, this study aims to clarify the anticancer efficacy and safety of insect-derived peptides and to present their potential as future therapeutic agents.

Antimicrobial peptides as potential therapeutics for breast cancer

Breast cancer is the most common and deadliest cancer in women worldwide. Although notable advances have been achieved in the treatment of breast cancer, the overall survival rate of metastatic breast cancer patients is still considerably low due to the development of resistance to breast cancer chemotherapeutic agents and the non-optimal specificity of the current generation of cancer medications. Hence, there is a growing interest in the search for alternative therapeutics with novel anticancer mechanisms. Recently, antimicrobial peptides (AMPs) have gained much attention due to their cost-effectiveness, high specificity of action, and robust efficacy. However, there are no clinical data available about their efficacy. This warrants the increasing need for clinical trials to be conducted to assess the efficacy of this new class of drugs. Here, we will focus on the recent progress in the use of AMPs for breast cancer therapy and will highlight their modes of action. Finally, we will discuss the combination of AMP-based therapeutics with other breast cancer therapy strategies, including nanotherapy and chemotherapy, which may provide a potential avenue for overcoming drug resistance.

Recent Advances in Therapeutic Peptides for Breast Cancer Treatment

Breast cancer is a heterogeneous malignancy and is the second leading cause of mortality among women around the world. Increasing the resistance to anti-cancer drugs in breast cancer cells persuades researchers to search the novel therapeutic approaches for the treatment of this malignancy. Among the novel methods, therapeutic peptides that target and disrupt tumor cells have been of great interest. Therapeutic peptides are short amino acid monomer chains with high specificity to bind and modulate a protein interaction of interest. Several advantages of peptides, such as specific binding on tumor cells surface, low molecular weight, and low toxicity on normal cells, make the peptides appealing therapeutic agents against solid tumors, particularly breast cancer. Also, the National Institutes of Health (NIH) describes therapeutic peptides as a suitable candidate for the treatment of drug-resistant breast cancer. In this review, we attempt to review the different therapeutic peptides against breast cancer cells that can be used in the treatment and diagnosis of the malignancy. Meanwhile, we presented an overview of peptide vaccines that have been developed for the treatment of breast cancer.

Chaperonin-Containing TCP1 Complex (CCT) Promotes Breast Cancer Growth Through Correlations With Key Cell Cycle Regulators

Uncontrolled proliferation as a result of dysregulated cell cycling is one of the hallmarks of cancer. Therapeutically targeting pathways that control the cell cycle would improve patient outcomes. However, the development of drug resistance and a limited number of inhibitors that target multiple cell cycle modulators are challenges that impede stopping the deregulated growth that leads to malignancy. To advance the discovery of new druggable targets for cell cycle inhibition, we investigated the role of Chaperonin-Containing TCP1 (CCT or TRiC) in breast cancer cells. CCT, a type II chaperonin, is a multi-subunit protein-folding complex that interacts with many oncoproteins and mutant tumor suppressors. CCT subunits are highly expressed in a number of cancers, including breast cancer. We found that expression of one of the CCT subunits, CCT2, inversely correlates with breast cancer patient survival and is subject to copy number alterations through genomic amplification. To investigate a role for CCT2 in the regulation of the cell cycle, we expressed an exogenous CCT2-FLAG construct in T47D and MCF7 luminal A breast cancer cells and examined cell proliferation under conditions of two-dimensional (2D) monolayer and three-dimensional (3D) spheroid cultures. Exogenous CCT2 increased the proliferation of cancer cells, resulting in larger and multiple spheroids as compared to control cells. CCT2-expressing cells were also able to undergo spheroid growth reversal, re-attaching, and resuming growth in 2D cultures. Such cells gained anchorage-independent growth. CCT2 expression in cells correlated with increased expression of MYC, especially in spheroid cultures, and other cell cycle regulators like CCND1 and CDK2, indicative of a novel activity that could contribute to the increase in cell growth. Statistically significant correlations between CCT2, MYC, and CCND1 were shown. Since CCT2 is located on chromosome 12q15, an amplicon frequently found in soft tissue cancers as well as breast cancer, CCT2 may have the basic characteristics of an oncogene. Our findings suggest that CCT2 could be an essential driver of cell division that may be a node through which pathways involving MYC, cyclin D1 and other proliferative factors could converge. Hence the therapeutic inhibition of CCT2 may have the potential to achieve multi-target inhibition, overcoming the limitations associated with single agent inhibitors.

Exploiting the HSP60/10 chaperonin system as a chemotherapeutic target for colorectal cancer

Over the past few decades, an increasing variety of molecular chaperones have been investigated for their role in tumorigenesis and as potential chemotherapeutic targets; however, the 60 kDa Heat Shock Protein (HSP60), along with its HSP10 co-chaperone, have received little attention in this regard. In the present study, we investigated two series of our previously developed inhibitors of the bacterial homolog of HSP60/10, called GroEL/ES, for their selective cytotoxicity to cancerous over non-cancerous colorectal cells. We further developed a third "hybrid" series of analogs to identify new candidates with superior properties than the two parent scaffolds. Using a series of well-established HSP60/10 biochemical screens and cell-viability assays, we identified 24 inhibitors (14%) that exhibited > 3-fold selectivity for targeting colorectal cancer over non-cancerous cells. Notably, cell viability EC₅₀ results correlated with the relative expression of HSP60 in the mitochondria, suggesting a potential for this HSP60-targeting chemotherapeutic strategy as emerging evidence indicates that HSP60 is up-regulated in colorectal cancer tumors. Further examination of five lead candidates indicated their ability to inhibit the clonogenicity and migration of colorectal cancer cells. These promising results are the most thorough analysis and first reported instance of HSP60/10 inhibitors being able to selectively target colorectal cancer cells and highlight the potential of the HSP60/10 chaperonin system as a viable chemotherapeutic target.

Targeted nanomedicine modalities for prostate cancer treatment

Prostate cancer (PC) is the second most common cause of death amongst men in the USA. Therapy of PC has been transformed in the past decade by introducing novel therapeutics, advanced functional imaging and diagnostic approaches, next generation sequencing, as well as improved application of existing therapies in localized PC. Treatment of PC at the different stages of the disease may include surgery, androgen deprivation therapy (ADT), chemotherapy and radiation therapy. However, although ADT has proven efficacious in PC treatment, its effectiveness may be temporary, as these tumors frequently develop molecular mechanisms of therapy resistance, which allow them to survive and proliferate even under conditions of testosterone deprivation, inhibition of androgen receptor signaling, or cytotoxic drug treatment. Importantly, ADT was found to induce key alterations which frequently result in the formation of metastatic tumors displaying a therapy refractory phenotype. Hence, to overcome these serious therapeutic impediments, novel PC cell-targeted therapeutic strategies are being developed. These include diverse platforms enabling specific enhanced antitumor drug uptake and increased intracellular accumulation. Studies have shown that these novel treatment modalities lead to enhanced antitumor activity and diminished systemic toxicity due to the use of selective targeting and decreased drug doses. The underlying mechanism of targeting and internalization is based upon the interaction between a selective ligand, conjugated to a drug-loaded nanoparticle or directly to an anti-cancer drug, and a specific plasma membrane biomarker, uniquely overexpressed on the surface of PC cells. Another targeted therapeutic approach is the delivery of unique anti-oncogenic signaling pathway-based therapeutic drugs, which are selectively cytotoxic to PC cells. The current paper reviews PC targeted modalities reported in the past 6 years, and discusses both the advantages and limitations of the various targeted treatment strategies.

Polymeric Nanoparticles with a Sera-Derived Coating for Efficient Cancer Cell Uptake and Killing

Nanoparticle-mediated cancer drug delivery remains an inefficient process. The protein corona formed on nanoparticles (NPs) controls their biological identity and, if optimized, could enhance cancer cell uptake. In this study, a hyperbranched polyester polymer (HBPE) was synthesized from diethyl malonate and used to generate NPs that were subsequently coated with normal sera (NS) collected from mice. Cellular uptake of NS-treated HBPE-NPs was compared to PEGylated HBPE-NPs and was assessed using MDA-MB-231 triple-negative breast cancer (TNBC) cells as well as endothelial and monocytic cell lines. NS-treated HBPE-NPs were taken up by TNBC cells more efficiently than PEGylated HBPE-NPs, while evasion of monocyte uptake was comparable. NS coatings facilitated cancer cell uptake of HBPE-NPs, even after prior interaction of the particles with an endothelial layer. NS-treated HBPE-NPs were not inherently toxic, did not induce the migration of endothelial cells that could lead to angiogenesis, and could efficiently deliver cytotoxic doses of paclitaxel (taxol) to TNBC cells. These findings suggest that HBPE-NPs may adsorb select sera proteins that improve uptake by cancer cells, and such NPs could be used to advance the discovery of novel factors that improve the bioavailability and tissue distribution of drug-loaded polymeric NPs.

Cell-penetrating peptides in oncologic pharmacotherapy: A review

Cancer is the second leading cause of death in the world and its treatment is extremely challenging, mainly due to its complexity. Cell-Penetrating Peptides (CPPs) are peptides that can transport into the cell a wide variety of biologically active conjugates (or cargoes), and are, therefore, promising in the treatment and in the diagnosis of several types of cancer. Some notable examples are TAT and Penetratin, capable of penetrating the central nervous system (CNS) and, therefore, acting in cancers of this system, such as Glioblastoma Multiforme (GBM). These above-mentioned peptides, conjugated with traditional chemotherapeutic such as Doxorubicin (DOX) and Paclitaxel (PTX), have also been shown to induce apoptosis of breast and liver cancer cells, as well as in lung cancer cells, respectively. In other cancers, such as esophageal cancer, the attachment of Magainin 2 (MG2) to Bombesin (MG2B), another CPP, led to pronounced anticancer effects. Other examples are CopA3, that selectively decreased the viability of gastric cancer cells, and the CPP p28. Furthermore, in preclinical tests, the anti-tumor efficacy of this peptide was evaluated on human breast cancer, prostate cancer, ovarian cancer, and melanoma cells in vitro, leading to high expression of p53 and promoting cell cycle arrest. Despite the numerous in vitro and in vivo studies with promising results, and the increasing number of clinical trials using CPPs, few treatments reach the expected clinical efficacy. Usually, their clinical application is limited by its poor aqueous solubility, immunogenicity issues and dose-limiting toxicity. This review describes the most recent advances and innovations in the use of CPPs in several types of cancer, highlighting their crucial importance for various purposes, from therapeutic to diagnosis. Further clinical trials with these peptides are warranted to examine its effects on various types of cancer.

Elucidation of Therapeutic Peptide Binding Partners from Isolated Mitochondria

CT20p is a protein derived from the C-terminus of Bax. It has selective cytotoxicity for cancer cells, such as the sensitive triple-negative MDA-MB-231 breast adenocarcinoma cells, but not normal cells like the resistant MCF-10A epithelial breast cells. To understand the reason for the peptide’s selective toxicity, a "pull-down" experiment with biotinylated CT20p (biotin-CT20p) and whole-cell protein lysates from breast cancer and normal cells were performed. These studies revealed that CT20p binds to a cytosolic protein called chaperonin-containing TCP-1 (CCT), a molecular chaperone that folds actin and tubulin. However, this method could not detect possible rare interactions made by CT20p with mitochondrial proteins. To determine whether CT20p is associated with mitochondrial proteins as part of the mechanism by which it induces cell death, mitochondrial protein lysates from MDA-MB-231 and MCF-10A cells were isolated and a streptavidin-agarose pulldown procedure using biotin-CT20p was performed. Protein interactions were visualized by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) using silver staining. The results of the experimental procedure showed that biotin-CT20p did not "pull down" any observable mitochondrial proteins from the sensitive MDA-MB-231 cells, indicating that the peptide may not interact with mitochondrial proteins in breast cancer cells. Rather, the interactions observed with biotin-CT20p were with mitochondrial proteins derived from resistant MCF-10A cells, indicating that these interactions were not driving the cancer-selective cell death process. The absence of CT20p-associated proteins from the mitochondrial lysates of MDA-MB-231 breast cancer cells supports the hypothesis that CT20p, unlike the parent protein, Bax, exerts its cytotoxic effects via a cytosolic protein.

Targeting chaperonin containing TCP1 (CCT) as a molecular therapeutic for small cell lung cancer

Identifying new druggable targets is desired to meet the needs for effective cancer treatments. To this end, we previously reported the efficacy of a therapeutic peptide called CT20p that displays selective cytotoxicity through inhibition of a multi-subunit, protein-folding complex called Chaperonin-Containing TCP-1 (CCT). To investigate the role of CCT in cancer progression, we examined protein levels of CCT subunits in liver, prostate, and lung cancer using human tissue microarrays. We found that these cancers expressed higher levels of CCT2 as compared to normal tissues. Small cell lung cancer (SCLC) stood out as having statistically significant difference in CCT2. Higher levels of CCT2 in tumors from lung cancer patients were also associated with decreased survival. Using SCLC cell lines, we observed detectable amounts of CCT subunits and cells were susceptible to killing by CT20p. Treatment with CT20p, delivered to cells using polymeric nanoparticles, was cytotoxic to all SCLC cell lines, decreasing the levels of CCT client proteins like STAT3. In contrast, treatment with a STAT3 inhibitor was effective in one of the SCLC cell lines. While we found that CCT levels could vary in cell lines, normal tissues had low levels of CCT and minimal toxicity to liver or kidney function was observed in mice treated with CT20p. These results indicate that in SCLC, changes in CCT levels could be used as a biomarker for diagnosis and that targeting CCT for inhibition with CT20p is a promising treatment approach for those cancers such as SCLC that currently lack targeted therapeutics.

The functional domains for Bax∆2 aggregate-mediated caspase 8-dependent cell death

Bax∆2 is a functional pro-apoptotic Bax isoform having alterations in its N-terminus, but sharing the rest of its sequence with Baxα. Bax∆2 is unable to target mitochondria due to the loss of helix α1. Instead, it forms cytosolic aggregates and activates caspase 8. However, the functional domain(s) responsible for BaxΔ2 behavior have remained elusive. Here we show that disruption of helix α1 makes Baxα mimic the behavior of Bax∆2. However, the other alterations in the Bax∆2 N-terminus have no significant impact on aggregation or cell death. We found that the hallmark BH3 domain is necessary but not sufficient for aggregation-mediated cell death. We also noted that the core region shared by Baxα and Bax∆2 is required for the formation of large aggregates, which is essential for BaxΔ2 cytotoxicity. However, aggregation by itself is unable to trigger cell death without the C-terminus. Interestingly, the C-terminal helical conformation, not its primary sequence, appears to be critical for caspase 8 recruitment and activation. As Bax∆2 shares core and C-terminal sequences with most Bax isoforms, our results not only reveal a structural basis for Bax∆2-induced cell death, but also imply an intrinsic potential for aggregate-mediated caspase 8-dependent cell death in other Bax family members.

PSMA-Targeted Theranostic Nanocarrier for Prostate Cancer

Herein, we report the use of a theranostic nanocarrier (Folate-HBPE(CT20p)) to deliver a therapeutic peptide to prostate cancer tumors that express PSMA (folate hydrolase 1). The therapeutic peptide (CT20p) targets and inhibits the chaperonin-containing TCP-1 (CCT) protein-folding complex, is selectively cytotoxic to cancer cells, and is non-toxic to normal tissue. With the delivery of CT20p to prostate cancer cells via PSMA, a dual level of cancer specificity is achieved: (1) selective targeting to PSMA-expressing prostate tumors, and (2) specific cytotoxicity to cancer cells with minimal toxicity to normal cells. The PSMA-targeting theranostic nanocarrier can image PSMA-expressing cells and tumors when a near infrared dye is used as cargo. Meanwhile, it can be used to treat PSMA-expressing tumors when a therapeutic, such as the CT20p peptide, is encapsulated within the nanocarrier. Even when these PSMA-targeting nanocarriers are taken up by macrophages, minimal cell death is observed in these cells, in contrast with doxorubicin-based therapeutics that result in significant macrophage death. Incubation of PSMA-expressing prostate cancer cells with the Folate-HBPE(CT20p) nanocarriers induces considerable changes in cell morphology, reduction in the levels of integrin β1, and lower cell adhesion, eventually resulting in cell death. These results are relevant as integrin β1 plays a key role in prostate cancer invasion and metastatic potential. In addition, the use of the developed PSMA-targeting nanocarrier facilitates the selective in vivo delivery of CT20p to PSMA-positive tumor, inducing significant reduction in tumor size.

Evaluation of the use of therapeutic peptides for cancer treatment

Cancer along with cardiovascular disease are the main causes of death in the industrialised countries around the World. Conventional cancer treatments are losing their therapeutic uses due to drug resistance, lack of tumour selectivity and solubility and as such there is a need to develop new therapeutic agents. Therapeutic peptides are a promising and a novel approach to treat many diseases including cancer. They have several advantages over proteins or antibodies: as they are (a) easy to synthesise, (b) have a high target specificity and selectivity and (c) have low toxicity. Therapeutic peptides do have some significant drawbacks related to their stability and short half-life. In this review, strategies used to overcome peptide limitations and to enhance their therapeutic effect will be compared. The use of short cell permeable peptides that interfere and inhibit protein-protein interactions will also be evaluated.

Lipid raft-mediated miR-3908 inhibition of migration of breast cancer cell line MCF-7 by regulating the interactions between AdipoR1 and Flotillin-1

Background

The mechanisms of lipid raft regulation by microRNAs in breast cancer are not fully understood. This work focused on the evaluation and identification of miR-3908, which may be a potential biomarker related to the migration of breast cancer cells, and elucidates lipid-raft-regulating cell migration in breast cancer.

Methods

To confirm the prediction that miR-3908 is matched with AdipoR1, we used 3’-UTR luciferase activity of AdipoR1 to assess this. Then, human breast cancer cell line MCF-7 was cultured in the absence or presence of the mimics or inhibitors of miR-3908, after which the biological functions of MCF-7 cells were analyzed. The protein expression of AdipoR1, AMPK, and SIRT-1 were examined. The interaction between AdipoR1 and Flotillin-1, or its effects on lipid rafts on regulating cell migration of MCF-7, was also investigated.

Results

AdipoR1 is a direct target of miR-3908. miR-3908 suppresses the expression of AdipoR1 and its downstream pathway genes, including AMPK, p-AMPK, and SIRT-1. miR-3908 enhances the process of breast cancer cell clonogenicity. miR-3908 exerts its effects on the proliferation and migration of MCF-7 cells, which are mediated by lipid rafts regulating AdipoR1’s ability to bind Flotillin-1.

Conclusions

miR-3908 is a crucial mediator of the migration process in breast cancer cells. Lipid rafts regulate the interactions between AdipoR1 and Flotillin-1 and then the migration process associated with miR-3908 in MCF-7 cells. Our findings suggest that targeting miR-3908 and the lipid raft, may be a promising strategy for the treatment and prevention of breast cancer.

Chaperonin Containing TCP-1 Protein Level in Breast Cancer Cells Predicts Therapeutic Application of a Cytotoxic Peptide

PURPOSE

Metastatic disease is a leading cause of death for patients with breast cancer, driving the need for new therapies. CT20p is a peptide previously discovered by our group that displays cancer-specific cytotoxicity. To design the optimal therapeutic use of the peptide, we identified the intracellular target of CT20p in breast cancer cells, correlating expression patterns of the target with susceptibility to CT20p.

EXPERIMENTAL DESIGN

Using polymeric nanoparticles to deliver CT20p, we assessed cytoskeletal changes, cell migration, adhesion, and viability in cells treated with the peptide. Protein pull-down experiments, coupled to mass spectrometry, enabled identification of the peptide's intracellular target. Biochemical and histologic techniques validated target identity in human cell lines and breast cancer tissue microarrays and revealed susceptibility patterns to CT20p.

RESULTS

Chaperonin containing TCP-1 (CCT) was identified as the intracellular target of CT20p. Cancer cells susceptible to CT20p had increased CCT, and overexpression of CCTβ, a subunit of the CCT complex, enhanced susceptibility to CT20p. Susceptible cells displayed reduced tubulin, a substrate of CCT, and inhibition of migration upon CT20p treatment. CCTβ levels were higher in invasive ductal carcinomas than in cancer adjacent tissues and increased with breast cancer stage. Decreased breast cancer patient survival correlated with genomic alternations in CCTβ and higher levels of the chaperone.

CONCLUSIONS

Increased CCT protein in breast cancer cells underlies the cytotoxicity of CT20p. CCT is thus a potential target for therapeutic intervention and serves as a companion diagnostic to personalize the therapeutic use of CT20p for breast cancer treatment. Clin Cancer Res; 22(17); 4366-79. ©2016 AACR.

Bak apoptotic pores involve a flexible C-terminal region and juxtaposition of the C-terminal transmembrane domains

Bak and Bax mediate apoptotic cell death by oligomerizing and forming a pore in the mitochondrial outer membrane. Both proteins anchor to the outer membrane via a C-terminal transmembrane domain, although its topology within the apoptotic pore is not known. Cysteine-scanning mutagenesis and hydrophilic labeling confirmed that in healthy mitochondria the Bak α9 segment traverses the outer membrane, with 11 central residues shielded from labeling. After pore formation those residues remained shielded, indicating that α9 does not line a pore. Bak (and Bax) activation allowed linkage of α9 to neighboring α9 segments, identifying an α9:α9 interface in Bak (and Bax) oligomers. Although the linkage pattern along α9 indicated a preferred packing surface, there was no evidence of a dimerization motif. Rather, the interface was invoked in part by Bak conformation change and in part by BH3:groove dimerization. The α9:α9 interaction may constitute a secondary interface in Bak oligomers, as it could link BH3:groove dimers to high-order oligomers. Moreover, as high-order oligomers were generated when α9:α9 linkage in the membrane was combined with α6:α6 linkage on the membrane surface, the α6-α9 region in oligomerized Bak is flexible. These findings provide the first view of Bak carboxy terminus (C terminus) membrane topology within the apoptotic pore.

Safflower polysaccharide inhibits the proliferation and metastasis of MCF-7 breast cancer cell

Breast cancer accounts for 22.9% of all types of cancer in females worldwide. Safflower polysaccharide (SPS) is an active fraction purified from safflower petals (Carthamus tinctorius L). The present study investigated the effects of safflower polysaccharide on the proliferation and metastasis of breast cancer cells. Cell viability was analyzed using an MTT assay following treatment of the MCF‑7 cells with increasing concentrations of SPS. The results demonstrated that the SPS compound significantly inhibited the proliferation of the MCF‑7 human breast cancer cell line and these inhibitory effects increased in a dose‑ and time‑dependent manner. The half maximal inhibitory concentration (IC50) value of SPS on breast cancer cells, following treatment for 72 h, was detected using an MTT assay and was calculated as 0.12 mg/ml. The apoptotic rate was detected using flow cytometry in the MCF‑7 human breast cancer cell line and the results revealed that SPS induced cell apoptosis. The apoptotic rate of the MCF‑7 cells treated with SPS was significantly higher compared with that of the untreated cells and increased in a dose‑dependent manner. The expression of B‑cell lymphoma 2 (Bcl‑2) was downregulated and the expression of Bcl‑2‑associated X protein was upregulated in the MCF‑7 cells treated with SPS in a time‑dependent manner. Additionally, the expression of matrix metalloproteinase‑9 was significantly reduced and the expression of tissue inhibitor of metalloproteinase‑1 was increased in the MCF‑7 human breast cancer cell treated with SPS. These results demonstrated that SPS inhibited the metastasis of MCF‑7 breast cancer cells and understanding the underlying mechanisms may provide novel strategies in breast cancer therapy.

Dawn of advanced molecular medicine: nanotechnological advancements in cancer imaging and therapy

Nanotechnology plays an increasingly important role not only in our everyday life (with all its benefits and dangers) but also in medicine. Nanoparticles are to date the most intriguing option to deliver high concentrations of agents specifically and directly to cancer cells; therefore, a wide variety of these nanomaterials has been developed and explored. These span the range from simple nanoagents to sophisticated smart devices for drug delivery or imaging. Nanomaterials usually provide a large surface area, allowing for decoration with a large amount of moieties on the surface for either additional functionalities or targeting. Besides using particles solely for imaging purposes, they can also carry as a payload a therapeutic agent. If both are combined within the same particle, a theranostic agent is created. The sophistication of highly developed nanotechnology targeting approaches provides a promising means for many clinical implementations and can provide improved applications for otherwise suboptimal formulations. In this review we will explore nanotechnology both for imaging and therapy to provide a general overview of the field and its impact on cancer imaging and therapy.

Apoptosis inducing, conformationally constrained, dimeric peptide analogs of KLA with submicromolar cell penetrating abilities

The apoptosis inducing KLA peptide, (KLAKLAK)2, possesses an ability to disrupt mitochondrial membranes. However, this peptide has a poor eukaryotic cell penetrating potential and, as a result, it requires the assistance of other cell penetrating peptides for effective translocation in micromolar concentrations. In an effort to improve the cell penetrating potential of KLA, we have created a library in which pairs of residues on its hydrophobic face are replaced by Cys. The double Cys mutants were then transformed to bundle dimers by oxidatively generating two intermolecular disulfide bonds. We envisioned that once transported into cells, the disulfide bonds would undergo reductive cleavage to generate the monomeric peptides. The results of these studies showed that one of the mutant peptides, dimer B, has a high cell penetrating ability that corresponds to 100% of fluorescence positive cells at 250 nM. Even though dimer B induces disruption of the mitochondrial potential and cytochrome c release followed by caspase activation at submicromolar concentrations, it displays an LD50 of 1.6 μM under serum conditions using HeLa cells. Taken together, the results demonstrate that the strategy involving formation of bundle dimeric peptides is viable for the design of apoptosis inducing KLA peptide that translocate into cells at submicromolar concentrations.

Functions of the C-terminal domains of apoptosis-related proteins of the Bcl-2 family

Bcl-2 family proteins are involved in cell homeostasis, where they regulate cell death. Some of these proteins are pro-apoptotic and others pro-survival. Moreover, many of them share a similar domain composition with several of the so-called BH domains, although some only have a BH3 domain. A C-terminal domain is present in all the multi-BH domain proteins and in some of the BH3-only ones. This C-terminal domain is hydrophobic or amphipathic, for which reason it was thought when they were discovered that they were membrane anchors. Although this is indeed one of their functions, it has since been observed that they may also serve as regulators of the function of some members of this family, such as Bax. They may also serve to recognize the target membrane of some of these proteins, which only after an apoptotic signal, are incorporated into a membrane. It has been shown that peptides that imitate the sequence of C-terminal domains can form pores and may serve as a model to design cytotoxic molecules.

The CT20 peptide causes detachment and death of metastatic breast cancer cells by promoting mitochondrial aggregation and cytoskeletal disruption

Metastasis accounts for most deaths from breast cancer, driving the need for new therapeutics that can impede disease progression. Rationally designed peptides that take advantage of cancer-specific differences in cellular physiology are an emerging technology that offer promise as a treatment for metastatic breast cancer. We developed CT20p, a hydrophobic peptide based on the C terminus of Bax that exhibits similarities with antimicrobial peptides, and previously reported that CT20p has unique cytotoxic actions independent of full-length Bax. In this study, we identified the intracellular actions of CT20p which precede cancer cell-specific detachment and death. Previously, we found that CT20p migrated in the heavy membrane fractions of cancer cell lysates. Here, using MDA-MB-231 breast cancer cells, we demonstrated that CT20p localizes to the mitochondria, leading to fusion-like aggregation and mitochondrial membrane hyperpolarization. As a result, the distribution and movement of mitochondria in CT20p-treated MDA-MB-231 cells was markedly impaired, particularly in cell protrusions. In contrast, CT20p did not associate with the mitochondria of normal breast epithelial MCF-10A cells, causing little change in the mitochondrial membrane potential, morphology or localization. In MDA-MB-231 cells, CT20p triggered cell detachment that was preceded by decreased levels of α5β1 integrins and reduced F-actin polymerization. Using folate-targeted nanoparticles to encapsulate and deliver CT20p to murine tumors, we achieved significant tumor regression within days of peptide treatment. These results suggest that CT20p has application in the treatment of metastatic disease as a cancer-specific therapeutic peptide that perturbs mitochondrial morphology and movement ultimately culminating in disruption of the actin cytoskeleton, cell detachment, and loss of cell viability.

Hyperbranched polyester nanorods with pyrrolo[2,1-a]isoquinoline end groups for fluorescent recognition of Fe3+

Novel hyperbranched polyester nanorods HBPE-CICA₆ and HBPE-CICA₂ were obtained and used to establish a highly sensitive fluorescent sensor for Fe³⁺ ions.

Nanoscale drug delivery platforms overcome platinum-based resistance in cancer cells due to abnormal membrane protein trafficking

The development of cellular resistance to platinum-based chemotherapies is often associated with reduced intracellular platinum concentrations. In some models, this reduction is due to abnormal membrane protein trafficking, resulting in reduced uptake by transporters at the cell surface. Given the central role of platinum drugs in the clinic, it is critical to overcome cisplatin resistance by bypassing the plasma membrane barrier to significantly increase the intracellular cisplatin concentration enough to inhibit the proliferation of cisplatin-resistant cells. Therefore, rational design of appropriate nanoscale drug delivery platforms (nDDPs) loaded with cisplatin or other platinum analogues as payloads is a possible strategy to solve this problem. This review will focus on the known mechanism of membrane trafficking in cisplatin-resistant cells and the development and employment of nDDPs to improve cell uptake of cisplatin.

Molecular basis for membrane pore formation by Bax protein carboxyl terminus

Bax protein plays a key role in mitochondrial membrane permeabilization and cytochrome c release upon apoptosis. Our recent data have indicated that the 20-residue C-terminal peptide of Bax (BaxC-KK; VTIFVAGVLTASLTIWKKMG), when expressed intracellularly, translocates to the mitochondria and exerts lethal effect on cancer cells. Moreover, the BaxC-KK peptide, as well as two mutants where the two lysines are replaced with glutamate (BaxC-EE) or leucine (BaxC-LL), have been shown to form relatively large pores in lipid membranes, composed of up to eight peptide molecules per pore. Here the pore structure is analyzed by polarized Fourier transform infrared, circular dichroism, and fluorescence experiments on the peptides reconstituted in phospholipid membranes. The peptides assume an α/β-type secondary structure within membranes. Both β-strands and α-helices are significantly (by 30-60 deg) tilted relative to the membrane normal. The tryptophan residue embeds into zwitterionic membranes at 8-9 Å from the membrane center. The membrane anionic charge causes a deeper insertion of tryptophan for BaxC-KK and BaxC-LL but not for BaxC-EE. Combined with the pore stoichiometry determined earlier, these structural constraints allow construction of a model of the pore where eight peptide molecules form an "α/β-ring" structure within the membrane. These results identify a strong membranotropic activity of Bax C-terminus and propose a new mechanism by which peptides can efficiently perforate cell membranes. Knowledge on the pore forming mechanism of the peptide may facilitate development of peptide-based therapies to kill cancer or other detrimental cells such as bacteria or fungi.