HER-2: A biomarker at the crossroads of breast cancer immunotherapy and molecular medicine

A liposome-based cancer vaccine for a rapid and high-titre anti-ErbB-2 antibody response

Vaccines are arguably the most important medical technology developed to date. However, effective treatment of diseases such as breast cancer have so far evaded standard vaccination strategies. One popular target for cancer treatment is the cell surface membrane protein, ErbB-2, also known as Her-2 or neu. It is localised to the cell surface and has raised expression in 15-30% of all breast cancers, as well as in ovarian, colon and lung cancer. Here, a liposomal system comprised of spatially separated ErbB-2 peptide, to activate B cells, and ovalbumin peptide OVA323-339, to provide non-cognate T cell support, was used to generate antibodies against the epitope of the ErbB-2 protein targeted by Pertuzumab, a monoclonal antibody licensed for the treatment of ErbB-2 expressing cancers. After just 7 days a raised (7.3-fold, p<0.01), isotype-switched, humoral immune response specific for the ErbB-2 peptide was achieved in mice with pre-existing immunity to OVA which were exposed to liposomes with external ErbB-2 and internal OVA323-339. The absence of pre-existing OVA immunity in the mice or OVA323-339 peptide in the liposomes removed the effect. The effect of this anti-ErbB-2 antibody response was characterised against an ErbB-2 overexpressing tumour cell line both in vitro and in vivo. Notably, antibody responses were demonstrated to induce cell death in vitro, resulting in 96% reduction in viable cells. This study, therefore, demonstrates the feasibility of this approach to generate a rapid, high-titre, isotype-switched, antibody response that specifically targets ErbB-2 overexpression on tumour cells and is capable of inducing cell death in vitro in the absence of complement or immune cells.

Intratumor lactate levels reflect HER2 addiction status in HER2-positive breast cancer

Despite different molecular tumor profiles indicate that human epidermal growth factor receptor 2 (HER2) messenger RNA (mRNA) levels mirror HER2 addiction and trastuzumab benefit in HER2-positive breast cancer (BC), the identification of noninvasive clinical predictors of trastuzumab sensitivity remains an unmet clinical need. In the current study, we investigated whether intratumor lactate levels reflect HER2 addiction and, in turn, trastuzumab susceptibility. Accordingly, the gene expression profiles of transgenic murine BC cell lines expressing the human d16HER2 variant (HER2-addicted) or human full-length HER2 (WTHER2; HER2-nonaddicted) revealed a significant enrichment of glycolysis-related gene pathways in HER2-addicted cells. We studied the metabolic content of 22 human HER2-positive BC by quantitative nuclear magnetic resonance spectroscopy and found that those cases with higher lactate levels were characterized by higher HER2 transcript levels. Moreover, gene expression analyses of HER2-positive BC samples from a TCGA data set revealed a significant enrichment in glycolysis-related pathways in high/HER2-addicted tumors. These data were confirmed by metabolic analyses of human HER2-positive BC cell lines with high or low HER2 transcript levels, which revealed significantly more active glycolytic metabolism in high HER2 transcript than in low HER2 transcript cells. Overall, our results provide evidence for noninvasive intratumor lactate detection as a potential metabolic biomarker of HER2 addiction and trastuzumab response suggesting the possibility to use in vivo imaging to assess lactate levels and, in turn, select HER2-positive BC patients who are more likely to benefit from anti-HER2 treatments.

Spatially marking and quantitatively counting membrane immunoglobulin M in live cells via Ag cluster-aptamer probes

A probe composed of an aptamer and a silver cluster, where the aptamer targets mIgM of live cells and the silver cluster provides fluorescent imaging and mass quantification of mIgM of live cells, is presented. This new probe simultaneously provides accurate spatial and mass information of mIgM in live cells.

Vaccination with ErbB-2 peptides prevents cancer stem cell expansion and suppresses the development of spontaneous tumors in MMTV-PyMT transgenic mice

ErbB-2 has been implicated as a target for cancer-initiating cells in breast and other cancers. ErbB-2-directed peptide vaccines have been shown to be effective in prevention of spontaneous tumorigenesis of breast in neu transgenic mouse model, and cellular immunity is proposed as a mechanism for the anti-tumor efficacy. However, there has been no explanation as to how immunity suppresses tumorigenesis from the early stage carcinogenesis, when ErbB-2 expression in breast is low. Here, we investigated a peptide-based vaccine, which consists of two MHC class II epitopes derived from murine ErbB-2, to prevent the occurrence of spontaneous tumors in breast and assess immune impact on breast cancer stem cells. Female MMTV-PyMT transgenic mice were immunized with either ErbB-2 peptide vaccine, or a peptide from tetanus toxoid, or PBS in immune adjuvant. ErbB-2 peptides vaccine completely suppressed spontaneous breast tumors, and the efficacy was correlated with antigen-specific T-cell and antibody responses. In addition, immune serum from the mice of ErbB-2 vaccine group had an inhibitory effect on mammosphere-forming capacity and signaling through ErbB-2 and downstream Akt pathway in ErbB-2 overexpressing mouse mammary cancer cells. We provide evidence that multi-epitope class II peptides vaccine suppresses tumorigenesis of breast potentially by inhibiting the growth of cancer stem cells. We also suggest that a strategy of inducing strong immune responses using multi-epitope ErbB-2-directed helper vaccine might be useful in preventing breast cancer recurrence.

Mammalian plasma membrane proteins as potential biomarkers and drug targets

Defining the plasma membrane proteome is crucial to understand the role of plasma membrane in fundamental biological processes. Change in membrane proteins is one of the first events that take place under pathological conditions, making plasma membrane proteins a likely source of potential disease biomarkers with prognostic or diagnostic potential. Membrane proteins are also potential targets for monoclonal antibodies and other drugs that block receptors or inhibit enzymes essential to the disease progress. Despite several advanced methods recently developed for the analysis of hydrophobic proteins and proteins with posttranslational modifications, integral membrane proteins are still under-represented in plasma membrane proteome. Recent advances in proteomic investigation of plasma membrane proteins, defining their roles as diagnostic and prognostic disease biomarkers and as target molecules in disease treatment, are presented.

Co-administration of GP96 and Her2/neu DNA vaccine in a Her2 breast cancer model

Heat-shock proteins have biochemical and immunological roles in chaperoning/signaling and activation of innate and adaptive immune responses, respectively. Their effect on the immune response is due to a phenomenon known as cross-priming of antigen, in which exogenous antigens are presented via MHC class I by antigen presenting cells. GP96 exerts adjuvant activity with some viral and bacterial antigens when applied in the form of a DNA vaccine. In this study, animals with Her2-expressing tumors were vaccinated by co-administration of GP96+ Her2/neu DNA vaccines. Analyses of the immune response, 2 weeks after the last immunization revealed decreased CD4+ CD25+ Foxp3+ naturally occurring regulatory T cells (Tregs) at the tumor site and increased IFN-γ/IL-4 level. Nevertheless, the graph of tumor size demonstrated a bi-phasic pattern in which partial control of tumor progression initially occurred, but finally its effectiveness was inversely affected by tumor size.

Allele-specific copy number analysis of tumors

We present an allele-specific copy number analysis of the in vivo breast cancer genome. We describe a unique bioinformatics approach, ASCAT (allele-specific copy number analysis of tumors), to accurately dissect the allele-specific copy number of solid tumors, simultaneously estimating and adjusting for both tumor ploidy and nonaberrant cell admixture. This allows calculation of "ASCAT profiles" (genome-wide allele-specific copy-number profiles) from which gains, losses, copy number-neutral events, and loss of heterozygosity (LOH) can accurately be determined. In an early-stage breast carcinoma series, we observe aneuploidy (>2.7n) in 45% of the cases and an average nonaberrant cell admixture of 49%. By aggregation of ASCAT profiles across our series, we obtain genomic frequency distributions of gains and losses, as well as genome-wide views of LOH and copy number-neutral events in breast cancer. In addition, the ASCAT profiles reveal differences in aberrant tumor cell fraction, ploidy, gains, losses, LOH, and copy number-neutral events between the five previously identified molecular breast cancer subtypes. Basal-like breast carcinomas have a significantly higher frequency of LOH compared with other subtypes, and their ASCAT profiles show large-scale loss of genomic material during tumor development, followed by a whole-genome duplication, resulting in near-triploid genomes. Finally, from the ASCAT profiles, we construct a genome-wide map of allelic skewness in breast cancer, indicating loci where one allele is preferentially lost, whereas the other allele is preferentially gained. We hypothesize that these alternative alleles have a different influence on breast carcinoma development.

HER-2 signaling, acquisition of growth factor independence, and regulation of biological networks associated with cell transformation

Activated oncogenes are the dominant drivers of malignant progression in human cancer, yet little is known about how the transformation from proto-oncogene to activated oncogene drives the expression of transformed phenotypes. An isogenic model of HER-2-mediated transformation of human mammary epithelial cells was used along with HER-2-amplified human breast cancers to investigate how HER-2 activation alters its properties as a signaling molecule and changes the networks of HER-2-regulated genes. Our results show that full oncogenic activation of HER-2 is the result of a transition in which activated HER-2 acquires dominant signaling properties that qualitatively alter the network of genes regulated by the activated oncogene compared with the proto-oncogene. Consequently, gene expression programs related to invasion, cell stress, and stemness become regulated by HER-2 in a manner not observed in nontransformed cells, even when HER-2 is overexpressed. Our results offer novel insights into biological processes that come under the control of HER-2 after it acquires full oncogenic potential.

Transcriptional switches: chemical approaches to gene regulation

Given the role of transcriptional misregulation in the pathogenesis of human disease, there is enormous interest in the development of molecules that exogenously control transcription in a defined manner. The past decade has seen many exciting advancements in the identification of molecules that mimic or inhibit the interactions between natural transcriptional activators and their binding partners. In this minireview, we focus on four activator.target protein complexes, highlighting recent advances as well as challenges in the field.

Immunogenicity of allo-vesicle carrying ERBB2 tumor antigen for dendritic cell-based anti-tumor immunotherapy

Dendritic cells (DCs) are able to orchestrate innate and acquired immunity and can activate and sustain a long-lasting anti-tumor immune response in vivo when used as anti-tumor cell therapy. The selection of the antigen and the choice of its formulation are key points in designing anti-cancer DC-based vaccines. Cell released vesicles/exosomes have been shown to transfer antigens, HLAI/peptide complexes and co-stimulatory molecules to recipient cells. In this study we describe the generation of an allogenic microvesicle cell factory in which the expression of a specific tumor antigen was combined to the expression of co-stimulatory and allogeneic molecules. The DG75 lymphoblastoid cell line was selected as microvesicle producer and transfected with ErbB2, as tumor antigen prototype. The shed microvesicles transferred antigenic components to recipient DCs, increasing their immunogenicity. DC pulsing resulted in cross-presentation of ErbB2 both in HLAI and HLAII compartments, and ErbB2-specific CD8+ T cells from cancer patients were activated by DCs pulsed with vesicle-bound ErbB2. The microvesicle cell factory proposed may represent a source of cell free immunogen to be used for DC-based cancer therapy.

Shc is required for ErbB2-induced inhibition of apoptosis but is dispensable for cell proliferation and disruption of cell polarity

Amplification and overexpression of ErbB2 strongly correlates with aggressive breast cancers. A deeper understanding of pathways downstream of ErbB2 signaling that are required for the transformation of human mammary epithelial cells will identify novel strategies for therapeutic intervention in breast cancer. Using an inducible activation of ErbB2 autophosphorylation qsite mutants and the MCF-10A three-dimensional (3D) culture system, we investigated pathways used by ErbB2 to transform the epithelia. We report that ErbB2 induces cell proliferation and loss of 3D organization by redundant mechanisms, whereas it disrupts apical basal polarity and inhibits apoptosis using Tyr 1201 and Tyr 1226/7, respectively. Signals downstream of Tyr 1226/7 were also sufficient to confer paclitaxel resistance. The Tyr 1226/7 binds Shc, and the knockdown of Shc blocks the ability of ErbB2 to inhibit apoptosis and mediate paclitaxel resistance. Tyr 1226/7 is known to activate the Ras/Erk pathway; however, paclitaxel resistance did not correlate with the activation of Erk or Akt, suggesting the presence of a novel mechanism. Thus, our results show that targeting pathways used by ErbB2 to inhibit cell death is a better option than targeting cell proliferation pathways. Furthermore, we identify a novel function for Shc as a regulator of apoptosis and drug resistance in human mammary epithelial cells transformed by ErbB2.

Inhibition of ErbB2(Her2) expression with small molecule transcription factor mimics

Small molecules that mimic the transcriptional activation domain of eukaryotic transcriptional activators have the potential to serve as effective inhibitors of transcriptional processes. Here we show that one class of transcriptional activation domain mimics, amphipathic isoxazolidines, can be converted into inhibitors of gene expression mediated by the transcriptional activator ESX through small structural modifications. Addition of the small molecules leads to decreased expression of the cell surface growth receptor ErbB2(Her2) in ErbB2-positive cancer cells and, correspondingly, decreased proliferation.

Novel anti-filamin-A antibody detects a secreted variant of filamin-A in plasma from patients with breast carcinoma and high-grade astrocytoma

Identification of tumor-derived proteins in the circulation may allow for early detection of cancer and evaluation of therapeutic responses. To identify circulating tumor-derived proteins, mice were immunized with concentrated culture medium conditioned by human breast cancer cells. Antibodies generated by hybridomas were screened against conditioned media from both normal epithelial cells and tumor cells. Antibody selectively reacting with tumor cell-conditioned media was further characterized. This led to the development of a monoclonal antibody (Alper-p280) that reacts with a newly identified 280-kDa secreted variant of human filamin-A. Circulating filamin-A was detected in patient plasma samples using Alper-p280 in an ELISA assay. Human plasma samples from 134 patients with brain, breast, or ovarian cancer, 15 patients with active arthritis, and 76 healthy controls were analyzed. Filamin-A protein levels in human cell lines and tissues were analyzed by western blotting, immunohistochemistry, and electron and confocal microscopy. Circulating filamin-A was detected in the plasma of 109 of 143 patients with breast cancer and primary brain tumors. Plasma levels of filamin-A showed 89.5% sensitivity (95% confidence interval [CI] = 0.67% to 0.99%) and 97.8% specificity (95% CI = 0.88% to 0.99%) for glioblastoma at a cut-off of 21.0 ng/mL. Plasma levels of filamin-A (>36.0 ng/mL) had 96.7% sensitivity (95% CI = 0.80% to 0.99%) and 67.8% specificity (95% CI = 0.54% to 0.79%) for metastatic breast cancer. Filamin-A levels were increased in malignant breast or brain tissues, but not in normal control tissues. Filamin-A localized to lysosomes in MDA.MB.231 breast cancer cells, but not in normal human mammary epithelial cells, suggesting that filamin-A may undergo cancer-specific processing. Plasma filamin-A appears to be a specific and sensitive marker for patients with high-grade astrocytoma or metastatic breast cancer. Additional novel cancer biomarkers have been identified and are being developed alongside Alper-p280 for use in diagnosis of breast carcinoma and high-grade astrocytoma, and for use in the evaluation of therapeutic responses.

CCL16 Enhances the CD8+ and CD4+ T Cell Reactivity to Human Her-2 Elicited by Dendritic Cells Loaded with Rat Ortholog Her-2

T cells from HLA A2+ healthy donors were co-cultured with autologous dendritic cells (DC) loaded with apoptotic tumor cells expressing rat neu, and were induced to mature by tumor necrosis factor (TNF)α and interleukin (IL)-1β (mDC neu) or by the CCL16 chemokine (CCL16/mDC neu). Priming by CCL16/mDC neu induces a larger population of T cells that express cytoplasmatic interferon (IFN)γ, TNFα, perforin and granzyme B compared to those primed by mDC neu. T cells primed by CCL16/mDC neu release IFNγ in response to human HER-2+ cells and kill human HER-2+ target cells more efficiently than those primed by mDC neu. Our results show that both the loading of DC with xenogeneic rat neu and their maturation by CCL16 are two issues of critical importance for the elicitation of an effective response to human HER-2 in T cells from normal donors.

Aptamer directly evolved from live cells recognizes membrane bound immunoglobin heavy mu chain in Burkitt's lymphoma cells

The identification of tumor related cell membrane protein targets is important in understanding tumor progression, the development of new diagnostic tools, and potentially for identifying new therapeutic targets. Here we present a novel strategy for identifying proteins that are altered in their expression levels in a diseased cell using cell specific aptamers. Using an intact viable B-cell Burkitt's lymphoma cell line (Ramos cells) as the target, we have selected aptamers that recognize cell membrane proteins with high affinity. Among the selected aptamers that showed different recognition patterns with different cell lines of leukemia, the aptamer TD05 showed binding with Ramos cells. By chemically modifying TD05 to covalently cross-link with its target on Ramos cells to capture and to enrich the target receptors using streptavidin coated magnetic beads followed by mass spectrometry, we were able to identify membrane bound immunoglobin heavy mu chain as the target for TD05 aptamer. Immunoglobin heavy mu chain is a major component of the B-cell antigen receptor, which is expressed in Burkitt's lymphoma cells. This study demonstrates that this two step strategy, the development of high quality aptamer probes and then the identification of their target proteins, can be used to discover new disease related potential markers and thus enhance tumor diagnosis and therapy. The aptamer based strategy will enable effective molecular elucidation of disease related biomarkers and other interesting molecules.

Peptide vaccines of the HER-2/neu dimerization loop are effective in inhibiting mammary tumor growth in vivo

Human epidermal growth factor receptor-2 (HER-2)/neu (ErbB2), a member of the epidermal growth factor family of receptors, is overexpressed in 20-30% of breast cancers. It is an attractive target for receptor-directed antitumor therapy using mAbs. Unlike other epidermal growth factor receptor family members, HER-2/neu does not bind a high-affinity ligand, but rather functions as the preferred dimerization partner. Pertuzumab (Omnitarg) is a humanized mAb directed against the HER-2/neu dimerization domain that inhibits receptor signaling. The recent definition of the crystal structure of the HER-2/neu-pertuzumab complex demonstrated that the receptor dimerization region encompassed residues 266-333. Based on the three-dimensional structure of the complex, we have designed three conformational peptide constructs (sequences 266-296, 298-333, and 315-333) to mimic regions of the dimerization loop of the receptor and to characterize their in vitro and in vivo antitumor efficacy. All the constructs elicited high-affinity peptide Abs that inhibited multiple signaling pathways including HER-2/neu-specific inhibition of cellular proliferation and cytoplasmic receptor domain phosphorylation. All the peptide Abs showed Ab-dependent cellular cytotoxicity to varying degrees with the 266-296 constructs being equally effective as compared with Herceptin. The 266-296 peptide vaccine had statistically reduced tumor onset in both transplantable tumor models (FVB/n and BALB/c) and significant reduction in tumor development in two transgenic mouse tumor models (BALB-neuT and VEGF(+/-)Neu2-5(+/-)). The 266-296 construct represents the most promising candidate for antitumor vaccination and could also be used to treat a variety of cancers with either normal or elevated expression of HER-2 including breast, lung, ovarian, and prostate.

Inhibitor of heat-shock protein 90 enhances the antitumor effect of DNA vaccine targeting clients of heat-shock protein

Geldanamycin (GA), a heat-shock protein (HSP) 90 inhibitor, induces degradation of HSP90 client proteins, which may promote the presentation of degradation peptides with major histocompatibility complex class I on cancer cells. We hypothesized that GA may enhance the efficacy of DNA vaccination, and investigated the therapeutic effect of the combination of GA and a DNA vaccine against HSP90 clients p185(neu) and Met. The efficacy of various doses of GA combined with an N-terminal neu (N'-neu) DNA vaccine was investigated in a transplanted tumor constitutively overexpressing endogenous p185(neu). Low-dose (2.5 mug) but not high-dose (10 microg) GA enhanced the effect of N'-neu DNA vaccination on the inhibition of murine bladder tumor-2 tumors in syngeneic C3H mice. Anti-p185(neu) antibody titers were similar among all treated groups. Significantly increased infiltrations of CD8(+) T cells and NK cells were observed at tumor sites. GA sensitized tumor cells to the cytotoxic effects of lymphocytes. Depletion of CD8(+) T cells eliminated most of the therapeutic efficacy; in contrast, depletion of CD4(+) T cells enhanced the therapeutic efficacy. A similar enhancing effect was observed for the combination of GA and a DNA vaccine targeting the Met oncogene. Our results support the use of combination of GA and DNA vaccination against GA-targeted proteins.

Autologous neu DNA vaccine can be as effective as xenogenic neu DNA vaccine by altering administration route

We examined the therapeutic efficacy of xenogenic human N'-terminal neu DNA vaccine and autologous mouse N'-terminal neu DNA vaccine on MBT-2 tumor cells in C3H mice. Intramuscular injection of xenogenic and autologous neu DNA vaccines produced comparable therapeutic efficacies. Mouse and human N'-neu DNA vaccine induced tumor infiltration of CD8(+) T cells, while the human vaccine was less effective at stimulating natural killer cells. Depletion of CD8(+) T cells abolished the therapeutic efficacy of both types of DNA vaccines. On the other hand, xenogenic neu DNA vaccine showed significantly better therapeutic efficacy than autologous DNA vaccine with gene gun immunization. Increased infiltration of CD8(+) T cells was correlated with enhanced therapeutic efficacy in the human N'-neu group of mice. Therefore, intramuscular injection can enhance the therapeutic efficacy of autologous neu DNA vaccine.

Metallothionein as a prognostic biomarker in breast cancer

Breast cancer is the most common cancer in women, with a general upward trend in incidence. Basic and clinical breast cancer research has continued at a rapid pace, in the endeavor to understand the biology of the disease so as to improve management of patients. Besides traditional pathological indicators, expression of molecular markers in breast cancer has also been comprehensively investigated. This paper will focus on the prognostic utility of metallothioneins (MTs), a family of low molecular weight metal binding proteins encoded by at least 10 functional MT genes that are associated with cell proliferation in breast cancer. Evidence that MT is a potential prognostic biomarker for breast cancer is supported by many reports in the literature. Expression of the MT protein has been detected by immunohistochemistry in a significant portion of invasive ductal breast cancers. MT expression has also been well studied in association with traditional clinico-pathological parameters of breast cancers. Generally, higher MT expression in breast cancers is predictive of worse patient outcomes. The relationship of MT isoforms to histological grade, estrogen receptor (ER) status, and prognosis will also be discussed.

Cancer despite immunosurveillance: immunoselection and immunosubversion

Numerous innate and adaptive immune effector cells and molecules participate in the recognition and destruction of cancer cells, a process that is known as cancer immunosurveillance. But cancer cells avoid such immunosurveillance through the outgrowth of poorly immunogenic tumour-cell variants (immunoselection) and through subversion of the immune system (immunosubversion). At the early stages of carcinogenesis, cell-intrinsic barriers to tumour development seem to be associated with stimulation of an active antitumour immune response, whereas overt tumour development seems to correlate with changes in the immunogenic properties of tumour cells. The permanent success of treatments for cancer might depend on using immunogenic chemotherapy to re-establish antitumour immune responses.