Dimeric HER2-specific affibody molecules inhibit proliferation of the SKBR-3 breast cancer cell line

Evaluating a targeted Palbociclib-Trastuzumab loaded smart niosome platform for treating HER2 positive breast cancer cells

In this study, we present a targeted and pH-sensitive niosomal (pHSN) formulation, incorporating quantum dot (QD)-labeled Trastuzumab (Trz) molecules for the specific delivery of Palbociclib (Pal) to cells overexpressing human epidermal growth factor receptor 2 (HER2). FTIR analyses confirmed the successful preparation of the pHSNs and their bioconjugation. The labeled Trz-conjugated Pal-pHSNs (Trz-Pal-pHSNs) exhibited a size of approximately 170 nm, displaying a spherical shape with a neutral surface charge of -1.2 mV. Pal encapsulation reached ∼86%, and the release pattern followed a two-phase pH-dependent mechanism. MTT assessments demonstrated enhanced apoptosis induction, particularly in HER2-positive cells, by Trz-Pal-pHSNs. Fluorescence imaging further validated the internalization of particles into cells. In conclusion, Trz-Pal-pHSNs emerge as a promising platform for personalized medicine in the treatment of HER2-positive breast cancer.

Peptides Targeting HER2-Positive Breast Cancer Cells and Applications in Tumor Imaging and Delivery of Chemotherapeutics

Breast cancer represents the most common cancer type and one of the major leading causes of death in the female worldwide population. Overexpression of HER2, a transmembrane glycoprotein related to the epidermal growth factor receptor, results in a biologically and clinically aggressive breast cancer subtype. It is also the primary driver for tumor detection and progression and, in addition to being an important prognostic factor in women diagnosed with breast cancer, HER2 is a widely known therapeutic target for drug development. The aim of this review is to provide an updated overview of the main approaches for the diagnosis and treatment of HER2-positive breast cancer proposed in the literature over the past decade. We focused on the different targeting strategies involving antibodies and peptides that have been explored with their relative outcomes and current limitations that need to be improved. The review also encompasses a discussion on targeted peptides acting as probes for molecular imaging. By using different types of HER2-targeting strategies, nanotechnology promises to overcome some of the current clinical challenges by developing novel HER2-guided nanosystems suitable as powerful tools in breast cancer imaging, targeting, and therapy.

Novel Bifunctional Affibody Molecules with Specific Binding to Both EBV LMP1 and LMP2 for Targeted Therapy of Nasopharyngeal Carcinoma

Antibodies are considered highly specific therapeutic agents in cancer medicines, and numerous formats have been developed. Among them, bispecific antibodies (BsAbs) have gained a lot of attention as a next-generation strategy for cancer therapy. However, poor tumor penetration is a major challenge because of their large size and thus contributes to suboptimal responses within cancer cells. On the other hand, affibody molecules are a new class of engineered affinity proteins and have achieved several promising results with their applications in molecular imaging diagnostics and targeted tumor therapy. In this study, an alternative format for bispecific molecules was constructed and investigated, named Z_LMP110-277 and Z_LMP277-110, that targets Epstein-Barr virus latent membrane protein 1 (LMP1) and latent membrane protein 2 (LMP2). Surface plasmon resonance (SPR), indirect immunofluorescence assay, co-immunoprecipitation, and near-infrared (NIR) imaging clearly demonstrated that Z_LMP110-277 and Z_LMP277-110 have good binding affinity and specificity for both LMP1 and LMP2 in vitro and in vivo. Moreover, Z_LMP110-277 and Z_LMP277-110, especially Z_LMP277-110, significantly reduced the cell viability of C666-1 and CNE-2Z as compared to their monospecific counterparts. Z_LMP110-277 and Z_LMP277-110 could inhibit phosphorylation of proteins modulated by the MEK/ERK/p90RSK signaling pathway, ultimately leading to suppression of oncogene nuclear translocations. Furthermore, Z_LMP110-277 and Z_LMP277-110 showed significant antitumor efficacy in nasopharyngeal carcinoma-bearing nude mice. Overall, our results demonstrated that Z_LMP110-277 and Z_LMP277-110, especially Z_LMP277-110, are promising novel prognostic indicators for molecular imaging and targeted tumor therapy of EBV-associated nasopharyngeal carcinoma.

Complementation Dependent Enzyme Prodrug Therapy Enables Targeted Activation of Prodrug on HER2-Positive Cancer Cells

Antibodies have been explored for decades for the delivery of small molecule cytotoxins directly to diseased cells. In antibody-directed enzyme prodrug therapy (ADEPT), antibodies are armed with enzymes that activate nontoxic prodrugs at tumor sites. However, this strategy failed clinically due to off-target toxicity associated with the enzyme prematurely activating prodrug systemically. We describe here the design of an antibody-fragment split enzyme platform that regains activity after binding to HER2, allowing for site-specific activation of a small molecule prodrug. We evaluated a library of fusion constructs for efficient targeting and complementation to identify the most promising split enzyme pair. The optimal pair was screened for substrate specificity among chromogenic, fluorogenic, and prodrug substrates. Evaluation of this system on HER2-positive cells revealed 7-fold higher toxicity of the activated prodrug over prodrug treatment alone. Demonstrating the potential of this strategy against a known clinical target provides the basis for a unique therapeutic platform in oncology.

Bioengineering of virus-like particles as dynamic nanocarriers for in vivo delivery and targeting to solid tumours

Virus-like particles (VLPs) are known as self-assembled, non-replicative and non-infectious protein particles, which imitate the formation and structure of original wild type viruses, however, lack the viral genome and/or their fragments. The capacity of VLPs to encompass small molecules like nucleic acids and others has made them as novel vessels of nanocarriers for drug delivery applications. In addition, VLPs surface have the capacity to achieve variation of the surface display via several modification strategies including genetic modification, chemical modification, and non-covalent modification. Among the VLPs nanocarriers, Hepatitis B virus core (HBc) particles have been the most encouraging candidate. HBc particles are hollow nanoparticles in the range of 30-34 nm in diameter and 7 nm thick envelopes, consisting of 180 or 240 copies of identical polypeptide monomer. They also employ a distinctive position among the VLPs carriers due to the high-level synthesis, which serves as a strong protective capsid shell and efficient self-assembly properties. This review highlights on the bioengineering of HBc particles as dynamic nanocarriers for in vivo delivery and specific targeting to solid tumours.

Combinatorial in silico and in vivo evaluation of immune response elicitation by the affibody ZHER2

Due to the high affinity for binding to target molecules and also other unique attributes, affibodies have a great potential to be used in immunotherapeutic and diagnostic approaches. However, the possibility of undesirable immune response is still a great concern. In the current study, we investigated the possible antigenicity, allergenicity and cytotoxicity of the HER2-targeting affibody Z_HER2. The binding affinity of potential epitopes of the affibody to murine major histocompatibility complex (MHC) molecules was investigated by immunoinformatics tools and docking approaches. The possible interaction of Z_HER2 with human leukocyte antigens HLA-DP, HLA-DM, HLA-DQ and HLA-DR was also studied by protein-protein docking. Additionally, the synthesized affibody gene was expressed and the protein was purified for boosted immunization of Balb/c mice. Induced secretion of IFN-γ, IL-2, IL-4 and IL-10, and total serum IgG were assessed in the immunized mice. Furthermore, MTT cell viability test was performed to evaluate the cytotoxicity of Z_HER2 in splenocytes of the treated mice. In silico analyses showed the possible induction of the immune response by Z_HER2. While the affibody could elicit the secretion of cellular immune cytokines, it could not induce a significant humoral response in the treated mice and did not show any cytotoxic effects on the exposed splenocytes. These findings explain the practicability of Z_HER2 for therapeutic and in vivo diagnostic usages, though its ubiquitous application may need more studies.

The Influence of Domain Permutations of an Albumin-Binding Domain-Fused HER2-Targeting Affibody-Based Drug Conjugate on Tumor Cell Proliferation and Therapy Efficacy

Human epidermal growth factor receptor 2 (HER2) is a clinically validated target for breast cancer therapy. Previously, a drug-fused HER2-targeting affinity protein construct successfully extended the survival of mice bearing HER2-expressing xenografts. The aim of this study was to evaluate the influence of the number and positioning of the protein domains in the drug conjugate. Seven HER2-targeting affibody-based constructs, including one or two affibody molecules (Z) with or without an albumin-binding domain (ABD), namely Z, Z-ABD, ABD-Z, Z-Z, Z-Z-ABD, Z-ABD-Z, and ABD-Z-Z, were evaluated on their effects on cell growth, in vivo targeting, and biodistribution. The biodistribution study demonstrated that the monomeric constructs had longer blood retention and lower hepatic uptake than the dimeric ones. A dimeric construct, specifically ABD-Z-Z, could stimulate the proliferation of HER2 expressing SKOV-3 cells in vitro and the growth of tumors in vivo, whereas the monomeric construct Z-ABD could not. These two constructs demonstrated a therapeutic effect when coupled to mcDM1; however, the effect was more pronounced for the non-stimulating Z-ABD. The median survival of the mice treated with Z-ABD-mcDM1 was 63 days compared to the 37 days for those treated with ABD-Z-Z-mcDM1 or for the control animals. Domain permutation of an ABD-fused HER2-targeting affibody-based drug conjugate significantly influences tumor cell proliferation and therapy efficacy. The monomeric conjugate Z-ABD is the most promising format for targeted delivery of the cytotoxic drug DM1.

Improvement of Targeted Chemotherapy of HER2-positive Ovarian Malignant Cell Line by ZHER2-Idarubicin Conjugate: An in vitro Study

Background & Objective:

Overexpression of human epidermal growth factor receptor 2 (HER2) causes cell transformation and development of various types of malignancies. Idarubicin is an effective anti-neoplastic drug but its specific delivery to the targeted cells is still a great challenge. Affibody as a cost-effective peptide molecule with low molecular weight has a high affinity for HER2 receptors. Breast and ovarian cancers as wide speared types of malignancies are associated with high expression of HER2. In the current study, we assessed the cytotoxic effects of idarubicin-Z_HER2 affibody conjugate on the positive-HER2 cancer cell lines.

Methods:

The cytotoxic effects of constructed idarubicin-Z_HER2 affibody conjugate on the SK-BR-3, SK-OV-3, and MCF-7 cells with various levels of HER2 expression were evaluated by MTT assay following 48 hours of incubation.

Results:

Idarubicin showed a potent and dose-dependent cytotoxic effect against all treated cell lines while the SK-OV-3 cells were significantly more sensitive. The dimeric form of the Z_HER2 affibody molecule showed a mild effect on the cell viability of all treated cells at its optimum concentration. The constructed Idarubicin-Z_HER2 affibody conjugate decreased the viability of SK-OV-3 cells at its optimal concentration, more efficiently and specifically than other treated cells.

Conclusion:

The Z_HER2-affibody conjugate of idarubicin has a more specific cytotoxic effect compared with idarubicin alone against HER2-overexpressing ovarian cancerous cells. It appears the Z_HER2-affibody conjugate of idarubicin has great potential to be implicated as an innovative anti-cancer agent in future clinical trials in patients with HER2-overexpressing ovarian cancer.

Specific targeting of HER2-positive human breast carcinoma SK-BR-3 cells by amygdaline-ZHER2 affibody conjugate

Amygdalin induces apoptotic death in several carcinoma cells. Affibody is an engineered protein with a high affinity for human epidermal receptor 2 (HER2). We assessed the cytotoxic effects of the amygdalin-Z_HER2 affibody conjugate on two breast carcinoma cell lines. The Z_HER2 affibody gene was synthesized and transferred into E. coli BL21 as an expression host. After purification, the Z_HER2 affibody was conjugated to amygdalin. The cytotoxic effects of amygdalin and its Z_HER2 affibody conjugate on the SK-BR-3, with overexpression of HER2, and MCF-7 cells were evaluated by MTT assay. The effects of amygdalin and its conjugate on apoptotic death and expression of pro-apoptotic Bax and anti-apoptotic Bcl-2 proteins were measured. Amygdalin individually showed a potent cytotoxic effect against both MCF-7 (IC₅₀ = 14.2 mg ml^-1) and SK-BR-3 cells (IC₅₀ = 13.7 mg ml^-1). However, the amygdalin-Z_HER2 affibody conjugate had a more cytotoxic effect on SK-BR-3 (IC₅₀ = 8.27 mg ml^-1) than MCF-7 cells (IC₅₀ = 19.8 mg ml^-1). Amygdalin had a significant apoptotic effect on both cell lines and the effect of its conjugate on SK-BR-3 cells was significantly more potent than MCF-7 cells. Amygdalin increased Bax and decreased Bcl-2 expression in both cell lines. However, the effect of its conjugate on the Bax and Bcl-2 expression in SK-BR-3 was more potent than MCF-7 cells. In conclusion, the amygdalin-Z_HER2 affibody conjugate may be considered as a valuable candidate for specific treatment of breast cancer patients with overexpression of HER2. However, further in vivo studies are required to explain the antitumoral effects of constructed amygdalin-Z_HER2 affibody conjugate.

HER2-Specific Pseudomonas Exotoxin A PE25 Based Fusions: Influence of Targeting Domain on Target Binding, Toxicity, and In Vivo Biodistribution

The human epidermal growth factor receptor 2 (HER2) is a clinically validated target for cancer therapy, and targeted therapies are often used in regimens for patients with a high HER2 expression level. Despite the success of current drugs, a number of patients succumb to their disease, which motivates development of novel drugs with other modes of action. We have previously shown that an albumin binding domain-derived affinity protein with specific affinity for HER2, ADAPT₆, can be used to deliver the highly cytotoxic protein domain PE25, a derivative of Pseudomonas exotoxin A, to HER2 overexpressing malignant cells, leading to potent and specific cell killing. In this study we expanded the investigation for an optimal targeting domain and constructed two fusion toxins where a HER2-binding affibody molecule, Z_HER2:2891, or the dual-HER2-binding hybrid Z_HER2:2891-ADAPT₆ were used for cancer cell targeting. We found that both targeting domains conferred strong binding to HER2; both to the purified extracellular domain and to the HER2 overexpressing cell line SKOV3. This resulted in fusion toxins with high cytotoxic potency toward cell lines with high expression levels of HER2, with EC₅₀ values between 10 and 100 pM. For extension of the plasma half-life, an albumin binding domain was also included. Intravenous injection of the fusion toxins into mice showed a profound influence of the targeting domain on biodistribution. Compared to previous results, with ADAPT₆ as targeting domain, Z_HER2:2891 gave rise to further extension of the plasma half-life and also shifted the clearance route of the fusion toxin from the liver to the kidneys. Collectively, the results show that the targeting domain has a major impact on uptake of PE25-based fusion toxins in different organs. The results also show that PE25-based fusion toxins with high affinity to HER2 do not necessarily increase the cytotoxicity beyond a certain point in affinity. In conclusion, Z_HER2:2891 has the most favorable characteristics as targeting domain for PE25.

Specific Targeting of HER2-Positive Head and Neck Squamous Cell Carcinoma Line HN5 by Idarubicin-ZHER2 Affibody Conjugate

BACKGROUND

Expression of human epidermal growth factor receptor type 2 (HER2) in head and neck squamous cell carcinoma (HNSCC) cell line HN5 can be employed with great opportunities of success for specific targeting of anti-cancer chemotherapeutic agents.

OBJECTIVE

In the current study, HER2-specific affibody molecule, ZHER2:342 (an engineered protein with great affinity for HER2 receptors) was selected for conjugation to idarubicin (an anti-neoplastic antibiotic).

METHOD

ZHER2:342 affibody gene with one added cysteine code at the its 5' end was synthesized de novo and then inserted into pET302 plasmid and transferred to E. Coli BL21 hosting system. After induction of protein expression, the recombinant ZHER2 affibody molecules were purified using Ni- NTA resin and purity was analyzed through SDS-PAGE. Affinity-purified affibody molecules were conjugated to idarubicin through a heterobifunctional crosslinker, sulfosuccinimidyl 4-(Nmaleimidomethyl) cyclohexane-1-carboxylate (Sulfo-SMCC). Specific toxicity of idarubicin-ZHER2 affibody conjugate against two HER2-positive cells, HN5 and MCF-7 was assessed through MTT assay after an exposure time of 48 hours with different concentrations of conjugate.

RESULTS

Idarubicin in the non-conjugated form showed potent toxic effects against both cell lines, while HN5 cells were significantly more sensitive compared to MCF-7 cells. Dimeric ZHER2 affibody showed a mild decreasing effect on growth of both HN5 and MCF-7 cells at optimum concentration. Idarubicin-ZHER2 affibody conjugate at an optimum concentration reduced viability of HN5 cell line more efficiently compared to MCF-7 cell line.

CONCLUSION

In conclusion, idarubicin-ZHER2 affibody conjugate in optimum concentrations can be used for specific targeting and killing of HN5 cells.

Novel EBV LMP-2-affibody and affitoxin in molecular imaging and targeted therapy of nasopharyngeal carcinoma

Epstein-Barr virus (EBV) infection is closely linked to several human malignancies including endemic Burkitt’s lymphoma, Hodgkin’s lymphoma and nasopharyngeal carcinomas (NPC). Latent membrane protein 2 (LMP-2) of EBV plays a pivotal role in pathogenesis of EBV-related tumors and thus, is a potential target for diagnosis and targeted therapy of EBV LMP-2⁺ malignant cancers. Affibody molecules are developing as imaging probes and tumor-targeted delivery of small molecules. In this study, four EBV LMP-2-binding affibodies (Z_{EBV LMP-2}12, Z_{EBV LMP-2}132, Z_{EBV LMP-2}137, and Z_{EBV LMP-2}142) were identified by screening a phage-displayed LMP-2 peptide library for molecular imaging and targeted therapy in EBV xenograft mice model. Z_{EBV LMP-2} affibody has high binding affinity for EBV LMP-2 and accumulates in mouse tumor derived from EBV LMP-2⁺ xenografts for 24 h after intravenous (IV) injection. Subsequent fusion of Pseudomonas exotoxin PE38KDEL to the Z_{EBV LMP-2} 142 affibody led to production of Z142X affitoxin. This fused Z142X affitoxin exhibits high cytotoxicity specific for EBV⁺ cells in vitro and significant antitumor effect in mice bearing EBV⁺ tumor xenografts by IV injection. The data provide the proof of principle that EBV LMP-2-speicifc affibody molecules are useful for molecular imaging diagnosis and have potentials for targeted therapy of LMP-2-expressing EBV malignancies.

Molecular imaging diagnosis and targeted therapy have been successfully used for several types of tumors, but not yet applied to diagnose or treat EBV-associated NPC. Affibody molecules are small proteins engineered to bind to a large number of target proteins with high affinity, and therefore, can be developed as potential biopharmaceutical drugs for molecular diagnosis and therapeutic applications. In the present study, we screened and characterized EBV LMP-2-specific affibodies and evaluated their usage in molecular imaging of LMP-2 expressing cells and EBV LMP-2 tumor-bearing mice. Subsequently, we engineered and obtained an EBV LMP-2 affitoxin based on EBV LMP-2-binding affibodies and demonstrated its targeted cytotoxicity for EBV⁺ cell lines in vitro and in vivo. Our data indicate that the EBV LMP-2-specific affibody and its derived affitoxin are useful for diagnosis of LMP-2 expressing cells and targeted therapy of EBV-derived, LMP-2⁺ malignancies.

A Novel Affibody-Auristatin E Conjugate With a Potent and Selective Activity Against HER2+ Cell Lines

Targeted therapy is a new type of cancer treatment that most often uses biologically active drugs attached to a monoclonal antibody. This so called antibody-drug conjugate strategy allows the use of highly toxic substances that target tumor cells specifically, leaving healthy tissues largely unaffected. Over the last few years, antibody-drug conjugates have become a powerful tool in cancer treatment. We developed and characterized a novel cytotoxic conjugate against HER2 tumors in which the antibody has been substituted with a much smaller molecule: the affibody. The conjugate is composed of the ZHER2:2891 affibody that recognizes HER2 and a highly potent cytotoxic drug auristatin E. The ZHER2:2891 molecule does not contain cysteine(s) in its amino acid sequence. We generated 3 variants of ZHER2:2891, each containing a single cysteine to allow conjugation through the maleimide group that is present in the cytotoxic component. In 2 variants, we introduced single S46C and D53C substitutions. In the third variant, a short Drug Conjugation Sequence (DCS) containing a single cysteine was introduced at the C-terminus of ZHER2:2891, resulting in ZHER2:2891-DCS. The latter variant exhibited a significantly higher conjugation yield, and therefore its cytotoxicity has been studied more thoroughly. The ZHER2:2891-DCS-MMAE conjugate killed the HER2-overexpressing SK-BR-3 and MDA-MB-453 cells efficiently (IC50 values of 5.2 and 24.8 nM, respectively). The T-47-D and MDA-MB-231 cells that express normal levels of HER2 were significantly less sensitive to the conjugate (IC50 values of 135.6 and 161.5 nM, respectively). Overall, we have demonstrated for the first time that proteins other than antibodies/antibody fragments can be successfully combined with a linker-drug module, resulting in conjugates that eliminate cancer cells selectively.

Discovery of Benzo[g]quinazolin benzenesulfonamide derivatives as dual EGFR/HER2 inhibitors

An array of some new N-(substituted)-2-((4-oxo-3-(4-sulfamoylphenyl)-3,4-dihydrobenzo[g]quinazolin-2-yl)thio)acetamide 5-19 were synthesized from the starting compound 4-(2-mercapto-4-oxobenzo[g]quinazolin-3(4H)-yl)benzenesulfonamide 4, to be assessed for their cytotoxic activity against A549 lung cancer cell line and to determine their inhibitory effect on EGFR tyrosine kinase enzyme. Compounds 5-19 showed high activity towards A549 cell line with IC50 values of 0.12-8.70 μM. Compounds 6, 12 and 18 were the most potent in this series. These compounds were further screened as dual inhibitors for EGFR/HER2 enzymes in comparison with erlotinib and were found to possess very potent activity. Compound 12 showed the highest activity with IC50 values of 0.06 μM and 0.30 μM towards EGFR and HER2, respectively. Accordingly, the apoptotic effect of the most potent compounds 6, 12 and 18 was investigated and showed a marked increase in the level of caspases-3 by 6, 9 and 8 folds, respectively, compared to the control cells. Moreover, Molecular modeling was performed inside the active site of EGFR, keeping in mind their binding possibilities, bond lengths, angles and energy scores. It was found that the most active compounds demonstrated the best binding scores in the active site of EGFR, which may clarify their high inhibition profile.

A Conjugate Based on Anti-HER2 Diaffibody and Auristatin E Targets HER2-Positive Cancer Cells

Antibody-drug conjugates (ADCs) have recently emerged as efficient and selective cancer treatment therapeutics. Currently, alternative forms of drug carriers that can replace monoclonal antibodies are under intensive investigation. Here, a cytotoxic conjugate of an anti-HER2 (Human Epidermal Growth Factor Receptor 2) diaffibody with monomethyl-auristatin E (MMAE) is proposed as a potential anticancer therapeutic. The anti-HER2 diaffibody was based on the Z_HER2:4 affibody amino acid sequence. The anti-HER2 diaffibody has been expressed as a His-tagged protein in E. coli and purified by Ni-nitrilotriacetyl (Ni-NTA) agarose chromatography. The molecule was properly folded, and the high affinity and specificity of its interaction with HER2 was confirmed by surface plasmon resonance (SPR) and flow cytometry, respectively. The (Z_HER2:4)₂DCS-MMAE conjugate was obtained by coupling the maleimide group linked with MMAE to cysteines, which were introduced in a drug conjugation sequence (DCS). Cytotoxicity of the conjugate was evaluated using the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide MTT assay and the xCELLigence Real-Time Cell Analyzer. Our experiments demonstrated that the conjugate delivered auristatin E specifically to HER2-positive tumor cells, which finally led to their death. These results indicate that the cytotoxic diaffibody conjugate is a highly potent molecule for the treatment of various types of cancer overexpressing HER2 receptors.

Structure-based Design of Peptides with High Affinity and Specificity to HER2 Positive Tumors

To identify peptides with high affinity and specificity against human epidermal growth factor receptor 2 (HER2), a series of peptides were designed based on the structure of HER2 and its Z(HER2:342) affibody. By using a combination protocol of molecular dynamics modeling, MM/GBSA binding free energy calculations, and binding free energy decomposition analysis, two novel peptides with 27 residues, pep27 and pep27-24M, were successfully obtained. Immunocytochemistry and flow cytometry analysis verified that both peptides can specifically bind to the extracellular domain of HER2 protein at cellular level. The Surface Plasmon Resonance imaging (SPRi) analysis showed that dissociation constants (K D) of these two peptides were around 300 nmol/L. Furthermore, fluorescence imaging of peptides against nude mice xenografted with SKBR3 cells indicated that both peptides have strong affinity and high specificity to HER2 positive tumors.

Small sized EGFR1 and HER2 specific bifunctional antibody for targeted cancer therapy

Targeting tumors using miniature antibodies is a novel and attractive therapeutic approach, as these biomolecules exhibit low immunogenicity, rapid clearance, and high targeting specificity. However, most of the small-sized antibodies in existence do not exhibit marked anti-tumor effects, which limit their use in targeted cancer immunotherapy. To overcome this difficulty in targeting multiple biomarkers by combination therapies, we designed a new bifunctional antibody, named MaAbNA (multivalent antibody comprised of nanobody and affibody moieties), capable of targeting EGFR1 and HER2, which are widely overexpressed in a variety of tumor types. The small-sized (29 kDa) MaAbNA, which was expressed in E.coli, consists of one anti-EGFR1 nanobody and two anti-HER2 affibodies, and possesses high affinity (KD) for EGFR1 (~4.1 nM) and HER2 (~4.7 nM). In order to enhance its anti-tumor activity, MaAbNA was conjugated with adriamycin (ADM) using a PEG2000 linker, forming a new complex anticancer drug, MaAbNA-PEG2000-ADM. MaAbNA exhibited high inhibitory effects on tumor cells over-expressing both EGFR1 and HER2, but displayed minimal cytotoxicity in cells expressing low levels of EGFR1 and HER2. Moreover, MaAbNA-PEG2000-ADM displayed increased tumoricidal effects than ADM or MaAbNA alone, as well exhibited greater antitumor efficacy than EGFR1 (Cetuximab) and HER2 (Herceptin) antibody drugs. The ability of MaAbNA to regulate expression of downstream oncogenes c-jun, c-fos, c-myc, as well as AEG-1 for therapeutic potential was evaluated by qPCR and western-blot analyses. The antitumor efficacy of MaAbNA and its derivative MaAbNA-PEG2000-ADM were validated in vivo, highlighting the potential for use of MaAbNA as a highly tumor-specific dual molecular imaging probe and targeted cancer therapeutic.

Design, synthesis and characterization of peptidomimetic conjugate of BODIPY targeting HER2 protein extracellular domain

Among the EGFRs, HER2 is a major heterodimer partner and also has important implications in the formation of particular tumors. Interaction of HER2 protein with other EGFR proteins can be modulated by small molecule ligands and, hence, these protein-protein interactions play a key role in biochemical reactions related to control of cell growth. A peptidomimetic (compound 5-1) that binds to HER2 protein extracellular domain and inhibits protein-protein interactions of EGFRs was conjugated with BODIPY (4,4-difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-s-indacene). Conjugation of BODIPY to the peptidomimetic was investigated by different approaches. The conjugate was characterized for its ability to bind to HER2 overexpressing SKBR-3 and BT-474 cells. Furthermore, cellular uptake of conjugate of BODIPY was studied in the presence of membrane tracker and Lyso tracker using confocal microscopy. Our results suggested that fluorescently labeled compound 5-7 binds to the extracellular domain and stays in the membrane for nearly 24 h. After 24 h there is an indication of internalization of the conjugate. Inhibition of protein-protein interaction and downstream signaling effect of compound 5-1 was also studied by proximity ligation assay and Western blot analysis. Results suggested that compound 5-1 inhibit protein-protein interactions of HER2-HER3 and phosphorylation of HER2 in a time-dependent manner.

The HER2-binding affibody molecule (Z(HER2∶342))₂ increases radiosensitivity in SKBR-3 cells

We have previously shown that the HER2-specific affibody molecule (Z_HER2∶342)₂ inhibits proliferation of SKBR-3 cells. Here, we continue to investigate its biological effects in vitro by studying receptor dimerization and clonogenic survival following irradiation. We found that (Z_HER2∶342)₂ sensitizes the HER2-overexpressing cell line SKBR-3 to ionizing radiation. The survival after exposure to (Z_HER2∶342)₂ and 8 Gy (S_8Gy 0.006) was decreased by a factor four compared to the untreated (S_8Gy 0.023). The low HER2-expressing cell line MCF-7 was more radiosensitive than SKBR-3 but did not respond to (Z_HER2∶342)₂. Treatment by (Z_HER2∶342)₂ strongly increased the levels of dimerized and phosphorylated HER2 even after 5 minutes of stimulation. The monomeric Z_HER2∶342 does not seem to be able to induce receptor phosphorylation and dimerization or sensitize cells to irradiation.

Generation and evaluation of bispecific affibody molecules for simultaneous targeting of EGFR and HER2

Coexpression of several ErbB receptors has been found in many cancers and has been linked with increased aggressiveness of tumors and a worse patient prognosis. This makes the simultaneous targeting of two surface receptors by using bispecific constructs an increasingly appreciated strategy. Here, we have generated six such bispecific targeting proteins, each comprising two monomeric affibody molecules with specific binding to either of the two human epidermal growth factor receptors, EGFR and HER2, respectively. The bispecific constructs were designed with (i) alternative positioning (N- or C-terminal) of the different affibody molecules, (ii) two alternative peptide linkers (Gly(4)Ser)(3) or (Ser(4)Gly)(3), and (iii) affibody molecules with different affinity (nanomolar or picomolar) for HER2. Using both Biacore technology and cell binding assays, it was demonstrated that all six constructs could bind simultaneously to both their target proteins. N-terminal positioning of the inherent monomeric affibody molecules was favorable to promote the binding to the respective target. Interestingly, bispecific constructs containing the novel (Ser(4)Gly)(3) linker displayed a higher affinity in cell binding, as compared to constructs containing the more conventional linker, (Gly(4)Ser)(3). It could further be concluded that bispecific constructs (but not the monomeric affibody molecules) induced dimer formation and phosphorylation of EGFR in SKBR3 cells, which express fairly high levels of both receptors. It was also investigated whether the bispecific binding would influence cell growth or sensitize cells for ionizing radiation, but no such effects were observed.

Antitumor activity of phenethyl isothiocyanate in HER2-positive breast cancer models

BACKGROUND

HER2 is an oncogene, expression of which leads to poor prognosis in 30% of breast cancer patients. Although trastuzumab is apparently an effective therapy against HER2-positive tumors, its systemic toxicity and resistance in the majority of patients restricts its applicability. In this study we evaluated the effects of phenethyl isothiocyanate (PEITC) in HER2-positive breast cancer cells.

METHODS

MDA-MB-231 and MCF-7 breast cancer cells stably transfected with HER2 (high HER2 (HH)) were used in this study. The effect of PEITC was evaluated using cytotoxicity and apoptosis assay in these syngeneic cells. Western blotting was used to delineate HER2 signaling. SCID/NOD mice were implanted with MDA-MB-231 (HH) xenografts.

RESULTS

Our results show that treatment of MDA-MB-231 and MCF-7 cells with varying concentrations of PEITC for 24 h extensively reduced the survival of the cells with a 50% inhibitory concentration (IC50) of 8 μM in MDA-MB-231 and 14 μM in MCF-7 cells. PEITC treatment substantially decreased the expression of HER2, epidermal growth factor receptor (EGFR) and phosphorylation of signal transducer and activator of transcription 3 (STAT3) at Tyr-705. The expression of BCL-2-associated × (BAX) and BIM proteins were increased, whereas the levels of B cell lymphoma-extra large (BCL-XL) and X-linked inhibitor of apoptosis protein (XIAP) were significantly decreased in both the cell lines in response to PEITC treatment. Substantial cleavage of caspase 3 and poly-ADP ribose polymerase (PARP) were associated with PEITC-mediated apoptosis in MDA-MB-231 and MCF-7 cells. Notably, transient silencing of HER2 decreased and overexpressing HER2 increased the effects of PEITC. Furthermore, reactive oxygen species (ROS) generation, mitochondrial depolarization and apoptosis by PEITC treatment were much higher in breast cancer cells expressing higher levels of HER2 (HH) as compared to parent cell lines. The IC50 of PEITC following 24 h of treatment was reduced remarkably to 5 μM in MDA-MB-231 (HH) and 4 μM in MCF-7 (HH) cells, stably overexpressing HER2. Oral administration of 12 μM PEITC significantly suppressed the growth of breast tumor xenografts in SCID/NOD mice. In agreement with our in vitro results, tumors from PEITC-treated mice demonstrated reduced HER2, EGFR and STAT3 expression and increased apoptosis as revealed by cleavage of caspase 3 and PARP. In addition our results show that PEITC can enhance the efficacy of doxorubicin.

CONCLUSIONS

Our results show a unique specificity of PEITC in inducing apoptosis in HER2-expressing tumor cells in vitro and in vivo and enhancing the effects of doxorubicin. This unique specificity of PEITC offers promise to a subset of breast cancer patients overexpressing HER2.

Engineering antibodies for cancer therapy

The advent of modern antibody engineering has led to numerous successes in the application of these proteins for cancer therapy in the 13 years since the first Food and Drug Administration approval, which has stimulated active interest in developing more and better drugs based on these molecules. A wide range of tools for discovering and engineering antibodies has been brought to bear on this challenge in the past two decades. Here, we summarize mechanisms of monoclonal antibody therapeutic activity, challenges to effective antibody-based treatment, existing technologies for antibody engineering, and current concepts for engineering new antibody formats and antibody alternatives as next generation biopharmaceuticals for cancer treatment.

Engineered high-affinity affibody molecules targeting platelet-derived growth factor receptor β in vivo

Platelet-derived growth factor receptor (PDGFR) β is a marker of stromal pericytes and fibroblasts and represents an interesting target for both diagnosis and therapy of solid tumors. A receptor-specific imaging agent would be a useful tool for further understanding the prognostic role of this receptor in vivo. Affibody molecules constitute a class of very small binding proteins that are highly suited for in vivo imaging applications and that can be selected to specifically recognize a desired target protein. Here we describe the isolation of PDGFRβ-specific Affibody molecules with subnanomolar affinity. First-generation Affibody molecules were generated from a large naive library using phage display selection. Subsequently, sequences from binders having a desired selectivity profile and competing with the natural ligand for binding were used in the design of an affinity maturation library, which was created using a single partially randomized oligonucleotide. From this second-generation library, Affibody molecules with a 10-fold improvement in affinity (K(d)=0.4-0.5 nM) for human PDGFRβ and a 4-fold improvement in affinity (K(d)=6-7 nM) for murine PDGFRβ were isolated and characterized. Complete reversible folding after heating to 90 °C, as demonstrated by circular dichroism analysis, supports tolerance to labeling conditions for molecular imaging. The binders were highly specific, as verified by dot blot showing staining reactivity only with human and murine PDGFRβ, but not with human PDGFRα, or a panel of control proteins including 16 abundant human serum proteins. The final binder recognized the native conformation of PDGFRβ expressed in murine NIH-3T3 fibroblasts and human AU565 cells, and inhibited ligand-induced receptor phosphorylation in PDGFRβ-transfected porcine aortic endothelial cells. The PDGFRβ-specific Affibody molecule also accumulated around tumoral blood vessels in a model of spontaneous insulinoma, confirming a potential for in vivo targeting.

Structural basis for high-affinity HER2 receptor binding by an engineered protein

The human epidermal growth factor receptor 2 (HER2) is specifically overexpressed in tumors of several cancers, including an aggressive form of breast cancer. It is therefore a target for both cancer diagnostics and therapy. The 58 amino acid residue Zher2 affibody molecule was previously engineered as a high-affinity binder of HER2. Here we determined the structure of Zher2 in solution and the crystal structure of Zher2 in complex with the HER2 extracellular domain. Zher2 binds to a conformational epitope on HER2 that is distant from those recognized by the therapeutic antibodies trastuzumab and pertuzumab. Its small size and lack of interference may provide Zher2 with advantages for diagnostic use or even for delivery of therapeutic agents to HER2-expressing tumors when trastuzumab or pertuzumab are already employed. Biophysical characterization shows that Zher2 is thermodynamically stable in the folded state yet undergoing conformational interconversion on a submillisecond time scale. The data suggest that it is the HER2-binding conformation that is formed transiently prior to binding. Still, binding is very strong with a dissociation constant K(D) = 22 pM, and perfect conformational homogeneity is therefore not necessarily required in engineered binding proteins. A comparison of the original Z domain scaffold to free and bound Zher2 structures reveals how high-affinity binding has evolved during selection and affinity maturation and suggests how a compromise between binding surface optimization and stability and dynamics of the unbound state has been reached.

Development of an optimized protocol for studying the interaction of filamentous bacteriophage with mammalian cells by fluorescence microscopy

Filamentous bacteriophage has been proposed as a vehicle that can carry and deliver therapeutics into mammalian cells for disease treatment, thus a protocol for imaging phage-cell interaction is essential. Because high signal intensity is necessary to study the mechanism of interaction between filamentous bacteriophage and mammalian cells, it is important to optimize the procedure for fluorescence labeling of phage in order to understand such interaction. Here, we describe a procedure that gives intense fluorescence labeling and can show interactions between fd-tet bacteriophage selected from phage libraries and mammalian cells (SKBR-3 and MCF-10A). The indirect labeling of phage with dye-conjugated antibody and cytoskeleton associated proteins was significantly enhanced in the presence of a cross-linking reagent called dithiobissuccinimidylpropionate (DSP) as shown by qualitative and quantitative fluorescence microscopy. The use of DSP resulted in high signal intensity in fluorescence imaging of phage-cell complex. The DSP cross-linker is believed to preserve soluble unbound proteins for fluorescence imaging. The interaction between the phage and mammalian cells was further confirmed by scanning electron microscopy.

Grading the commercial optical biosensor literature-Class of 2008: 'The Mighty Binders'

Optical biosensor technology continues to be the method of choice for label-free, real-time interaction analysis. But when it comes to improving the quality of the biosensor literature, education should be fundamental. Of the 1413 articles published in 2008, less than 30% would pass the requirements for high-school chemistry. To teach by example, we spotlight 10 papers that illustrate how to implement the technology properly. Then we grade every paper published in 2008 on a scale from A to F and outline what features make a biosensor article fabulous, middling or abysmal. To help improve the quality of published data, we focus on a few experimental, analysis and presentation mistakes that are alarmingly common. With the literature as a guide, we want to ensure that no user is left behind.