Anti-human epidermal growth factor receptor 2 monoclonal antibody therapy for breast cancer

A Kinetically Controlled Bioconjugation Method for the Synthesis of Radioimmunoconjugates and the Development of a Domain Mapping MS-Workflow for Its Characterization

Immunoconjugates exploit the high affinity of monoclonal antibodies for a recognized antigen to selectively deliver a cytotoxic payload, such as drugs or radioactive nuclides, at the site of disease. Despite numerous techniques have been recently developed for site-selective bioconjugations of protein structures, reaction of ε-amine group of lysine residues with electrophilic reactants, such as activated esters (NHS), is the main method reported in the literature as it maintains proteins in their native conformation. Since antibodies hold a high number of lysine residues, a heterogeneous mixture of conjugates will be generated, which can result in decreased target affinity. Here, we report an intradomain regioselective bioconjugation between the monoclonal antibody Trastuzumab and the N-hydroxysuccinimide ester of the chelator 2,2',2″,2‴-(1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrayl)tetraacetic acid (DOTA) by a kinetically controlled reaction adding substoichiometric quantities of the activated ester to the mAb working at slightly basic pH. Liquid chromatography-mass spectrometry (LC-MS) analyses were carried out to assess the chelator-antibody ratio (CAR) and the number of chelating moieties linked to the mAb chains. Proteolysis experiments showed four lysine residues mainly involved in bioconjugation (K188 for the light chain and K30, K293, and K417 for the heavy chain), each of which was located in a different domain. Since the displayed intradomain regioselectivity, a domain mapping MS-workflow, based on a selective domain denaturation, was developed to quantify the percentage of chelator linked to each mAb domain. The resulting immunoconjugate mixture showed an average CAR of 0.9. About a third of the heavy chains were found as monoconjugated, whereas conjugation of the chelator in the light chain was negligible. Domain mapping showed the CH3 domain bearing 13% of conjugated DOTA, followed by CH2 and VH respectively bearing 12.5 and 11% of bonded chelator. Bioconjugation was not found in the CH1 domain, whereas for the light chain, only the CL domain was conjugated (6%). Data analysis based on LC-MS quantification of different analytical levels (intact, reduced chains, and domains) provided the immunoconjugate formulation. A mixture of immunoconjugates restricted to 15 species was obtained, and the percentage of each one within the mixture was calculated. In particular, species bearing 1 DOTA with a relative abundance ranging from 4 to 20-fold, in comparison to species bearing 2DOTA, were observed. Pairing of bioconjugation under kinetic control with the developed domain mapping MS-workflow could raise the standard of chemical quality for immunoconjugates obtained with commercially available reactants.

Peptide Ligands Specifically Targeting HER2 Receptor and the Role Played by a Synthetic Model System of the Receptor Extracellular Domain: Hypothesized Future Perspectives

A short (Fab)trastuzumab-derived peptide specific for HER2 receptor was identified. Its affinity for the model system HER2-DIVMP was found in a nanomolar range. The structural determinants responsible for the interaction between this ligand (A9) and HER2-DIVMP were investigated by both computational and NMR analysis. Next, the possibility of using A9 as HER2- specific probe for the nuclear medicine imaging was evaluated by conjugating A9 with the DTPA chelator and radiolabeling it with ¹¹¹In. The developed probe retained a nanomolar affinity to HER2-overexpressing cancer cells, however, some unspecific binding also occurred. The peptide internalization into cells by receptor-mediated endocytosis was also studied. Future perspectives are aimed at using A9 as a probe for molecular imaging diagnostics as well as active targeting of anticancer drugs. Lead structure optimization is needed to minimize the percentage of A9 unspecific binding and to increase the binding affinity to the receptor.

Hypoxia Attenuates Trastuzumab Uptake and Trastuzumab-Emtansine (T-DM1) Cytotoxicity through Redistribution of Phosphorylated Caveolin-1

The antibody-drug conjugate trastuzumab-emtansine (T-DM1) offers an additional treatment option for patients with HER2-amplified tumors. However, primary and acquired resistance is a limiting factor in a significant subset of patients. Hypoxia, a hallmark of cancer, regulates the trafficking of several receptor proteins with potential implications for tumor targeting. Here, we have investigated how hypoxic conditions may regulate T-DM1 treatment efficacy in breast cancer. The therapeutic effect of T-DM1 and its metabolites was evaluated in conjunction with biochemical, flow cytometry, and high-resolution imaging studies to elucidate the functional and mechanistic aspects of hypoxic regulation. HER2 and caveolin-1 expression was investigated in a well-annotated breast cancer cohort. We find that hypoxia fosters relative resistance to T-DM1 in HER2⁺ cells (SKBR3 and BT474). This effect was not a result of deregulated HER2 expression or resistance to emtansine and its metabolites. Instead, we show that hypoxia-induced translocation of caveolin-1 from cytoplasmic vesicles to the plasma membrane contributes to deficient trastuzumab internalization and T-DM1 chemosensitivity. Caveolin-1 depletion mimicked the hypoxic situation, indicating that vesicular caveolin-1 is indispensable for trastuzumab uptake and T-DM1 cytotoxicity. In vitro studies suggested that HER2 and caveolin-1 are not coregulated, which was supported by IHC analysis in patient tumors. We find that phosphorylation-deficient caveolin-1 inhibits trastuzumab internalization and T-DM1 cytotoxicity, suggesting a specific role for caveolin-1 phosphorylation in HER2 trafficking. IMPLICATIONS: Together, our data for the first time identify hypoxic regulation of caveolin-1 as a resistance mechanism to T-DM1 with potential implications for individualized treatment of breast cancer.

Evaluation of HER2-specific peptide ligand for its employment as radiolabeled imaging probe

HER2 transmembrane receptor is an important target in immunotherapy treatment of breast and gastroesophageal cancer. Molecular imaging of HER2 expression may provide essential prognostic and predictive information concerning disseminated cancer and aid in selection of an optimal therapy. Radiolabeled low molecular weight peptide ligands are particularly attractive as probes for molecular imaging, since they reach and bind to the target and clear from non-target organs and blood stream faster than bulky antibodies. In this study, we evaluated a potential HER2-imaging probe, an A9 nonapeptide, derived from the trastuzumab-Fab portion. Its cellular uptake was investigated by mass spectrometry analysis of the cytoplasmic cellular extracts. Moreover, based on in-silico modeling, DTPA chelator was conjugated to N-terminus of A9. ¹¹¹In-labeled A9 demonstrated nanomolar affinity to HER2-expressing BT474 cells and favorable biodistribution profile in NMRI mice. This study suggests that the peptide A9 represents a good lead candidate for development of molecular probe, to be used for imaging purposes and for the delivery of cytotoxic agents.

Synthesis, Characterization, and Biological Evaluation of Anti-HER2 Indocyanine Green-Encapsulated PEG-Coated PLGA Nanoparticles for Targeted Phototherapy of Breast Cancer Cells

Human epidermal growth factor receptor 2 (HER2)-overexpressed breast cancer is known to be more aggressive and resistant to medicinal treatment and therefore to whom an alternative therapeutics is needed. Indocyanine green (ICG) has been widely exploited in breast cancer phototherapy. However, drawbacks of accelerated degradation and short half-life (2-4 min) in blood seriously hamper its use in the clinic. To overcome these challenges, an anti-HER2 ICG-encapsulated polyethylene glycol-coated poly(lactic-co-glycolic acid) nanoparticles (HIPPNPs) were developed in this study. Through the analyses of degradation rate coefficients of ICG with and without polymeric encapsulation, the photostability of HIPPNP-entrapped ICG significantly enhanced 4 folds (P < 0.05) while its thermal stabilities at 4 and 37°C significantly enhanced 5 and 3 (P < 0.05 for each) folds, respectively, under equal lighting and/or heating treatment for 48 h. The target specificity of HIPPNPs to HER2-positive cells was demonstrated based on a 6-fold (P < 0.05) enhancement of uptake efficiency of HIPPNPs in MDA-MB-453/HER2(+) cells within 4 h as compared with that in MCF7/HER2(-) cells. Moreover, the HIPPNPs with ≤ 25 μM ICG equivalent were nontoxic to cells in the absence of light illumination, and enabled to generate similar amount of singlet oxygen and hyperthermia effect as compared with that used by free ICG upon NIR irradiation. After 808 nm-laser irradiation with intensity of 6 W/cm2 for 5 min, the viability of MDA-MB-453 cells pre-treated by HIPPNPs with ≥ 5 μM ICG equivalent for 4 h significantly reduced as compared with that treated by equal concentration of free ICG (P < 0.05) and > 90% of the cells were eradicated while the dose of HIPPNPs was increased to 25 μM ICG equivalent. In summary, the developed HIPPNPs are anticipated as a feasible tool for use in phototherapy of breast cancer cells with HER2 expression.

HER2 overexpression and amplification as a potential therapeutic target in colorectal cancer: analysis of 3256 patients enrolled in the QUASAR, FOCUS and PICCOLO colorectal cancer trials

HER2 overexpression/amplification is linked to trastuzumab response in breast/gastric cancers. One suggested anti‐EGFR resistance mechanism in colorectal cancer (CRC) is aberrant MEK–AKT pathway activation through HER2 up‐regulation. We assessed HER2‐amplification/overexpression in stage II–III and IV CRC patients, assessing relationships to KRAS/BRAF and outcome. Pathological material was obtained from 1914 patients in the QUASAR stage II–III trial and 1342 patients in stage IV trials (FOCUS and PICCOLO). Tissue microarrays were created for HER2 immunohistochemistry. HER2‐amplification was assessed using FISH and copy number variation. KRAS/BRAF mutation status was assessed by pyrosequencing. Progression‐free survival (PFS) and overall survival (OS) data were obtained for FOCUS/PICCOLO and recurrence and mortality for QUASAR; 29/1342 (2.2%) stage IV and 25/1914 (1.3%) stage II–III tumours showed HER2 protein overexpression. Of the HER2‐overexpressing cases, 27/28 (96.4%) stage IV tumours and 20/24 (83.3%) stage II–III tumours demonstrated HER2 amplification by FISH; 41/47 (87.2%) also showed copy number gains. HER2‐overexpression was associated with KRAS/BRAF wild‐type (WT) status at all stages: in 5.2% WT versus 1.0% mutated tumours (p < 0.0001) in stage IV and 2.1% versus 0.2% in stage II–III tumours (p = 0.01), respectively. HER2 was not associated with OS or PFS. At stage II–III, there was no significant correlation between HER2 overexpression and 5FU/FA response. A higher proportion of HER2‐overexpressing cases experienced recurrence, but the difference was not significant. HER2‐amplification/overexpression is identifiable by immunohistochemistry, occurring infrequently in stage II–III CRC, rising in stage IV and further in KRAS/BRAFWT tumours. The value of HER2‐targeted therapy in patients with HER2‐amplified CRC must be tested in a clinical trial. © 2015 The Authors. Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

HER2 and uPAR cooperativity contribute to metastatic phenotype of HER2-positive breast cancer

Human epidermal growth factor receptor type 2 (HER2)-positive breast carcinoma is highly aggressive and mostly metastatic in nature though curable/manageable in part by molecular targeted therapy. Recent evidence suggests a subtype of cells within HER2-positive breast tumors that concomitantly expresses the urokinase plasminogen activator receptor (uPAR) with inherent stem cell/mesenchymal-like properties promoting tumor cell motility and a metastatic phenotype. This HER-positive/uPAR-positive subtype may be partially responsible for the failure of HER2-targeted treatment strategies. Herein we discuss and substantiate the cumulative preclinical and clinical evidence on HER2-uPAR cooperativity in terms of gene co-amplification and/or mRNA/protein co-overexpression. We then propose a regulatory signaling model that we hypothesize to maintain upregulation and cooperativity between HER2 and uPAR in aggressive breast cancer. An improved understanding of the HER2/uPAR interaction in breast cancer will provide critical biomolecular information that may help better predict disease course and response to therapy.

Pharmacokinetics, pharmacodynamics and physiologically-based pharmacokinetic modelling of monoclonal antibodies

Development of monoclonal antibodies (mAbs) and their functional derivatives represents a growing segment of the development pipeline in the pharmaceutical industry. More than 25 mAbs and derivatives have been approved for a variety of therapeutic applications. In addition, around 500 mAbs and derivatives are currently in different stages of development. mAbs are considered to be large molecule therapeutics (in general, they are 2-3 orders of magnitude larger than small chemical molecule therapeutics), but they are not just big chemicals. These compounds demonstrate much more complex pharmacokinetic and pharmacodynamic behaviour than small molecules. Because of their large size and relatively poor membrane permeability and instability in the conditions of the gastrointestinal tract, parenteral administration is the most usual route of administration. The rate and extent of mAb distribution is very slow and depends on extravasation in tissue, distribution within the particular tissue, and degradation. Elimination primarily happens via catabolism to peptides and amino acids. Although not definitive, work has been published to define the human tissues mainly involved in the elimination of mAbs, and it seems that many cells throughout the body are involved. mAbs can be targeted against many soluble or membrane-bound targets, thus these compounds may act by a variety of mechanisms to achieve their pharmacological effect. mAbs targeting soluble antigen generally exhibit linear elimination, whereas those targeting membrane-bound antigen often exhibit non-linear elimination, mainly due to target-mediated drug disposition (TMDD). The high-affinity interaction of mAbs and their derivatives with the pharmacological target can often result in non-linear pharmacokinetics. Because of species differences (particularly due to differences in target affinity and abundance) in the pharmacokinetics and pharmacodynamics of mAbs, pharmacokinetic/pharmacodynamic modelling of mAbs has been used routinely to expedite the development of mAbs and their derivatives and has been utilized to help in the selection of appropriate dose regimens. Although modelling approaches have helped to explain variability in both pharmacokinetic and pharmacodynamic properties of these drugs, there is a clear need for more complex models to improve understanding of pharmacokinetic processes and pharmacodynamic interactions of mAbs with the immune system. There are different approaches applied to physiologically based pharmacokinetic (PBPK) modelling of mAbs and important differences between the models developed. Some key additional features that need to be accounted for in PBPK models of mAbs are neonatal Fc receptor (FcRn; an important salvage mechanism for antibodies) binding, TMDD and lymph flow. Several models have been described incorporating some or all of these features and the use of PBPK models are expected to expand over the next few years.

An open-label safety study of lapatinib plus trastuzumab plus paclitaxel in first-line HER2-positive metastatic breast cancer

BACKGROUND

Recent data support the hypothesis that combining lapatinib and trastuzumab with taxane chemotherapy may offer added clinical benefit to patients with human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer (MBC). This study examined the safety of the triplet combination in first-line HER2-positive MBC.

PATIENTS AND METHODS

Patients were enrolled into three sequential cohorts; the last two cohorts were added by protocol amendment following review of safety data from cohort 1. Patients in cohort 1 received lapatinib (1000 mg/day) plus paclitaxel (80 mg/m(2) per week, 3 of every 4 weeks); cohort 2 received lapatinib (1000 mg/day) plus paclitaxel (70 mg/m(2) per week, 3 of every 4 weeks); and cohort 3 received lapatinib (750 mg/day) plus paclitaxel (80 mg/m(2) per week, 3 of every 4 weeks). All received standard trastuzumab dosing. The primary objective was assessment of dose-limiting toxicities, safety, and tolerability of this combination.

RESULTS

The most frequent adverse events (AEs) for all cohorts were diarrhea (89%), rash (79%), fatigue (73%), alopecia (63%), nausea (63%), and vomiting (40%). In cohorts 1 and 2, the incidence of grade 3 diarrhea was 62% and 50%, respectively; in cohort 3, the incidence was 25% (with prophylactic loperamide). Dehydration was the most frequent serious AE (10%). Across cohorts, overall response rate was 75%.

CONCLUSIONS

The dose-limiting toxicity of paclitaxel, trastuzumab, and lapatinib in first-line HER2-positive MBC was diarrhea. Of the triplet combinations tested, the cohort receiving 750 mg/day dose of lapatinib had the lowest incidence of diarrhea; therefore, this dose should be used in further studies on the treatment of MBC.

Molecular Mechanisms of Trastuzumab Resistance in HER2 Overexpressing Breast Cancer

The epidermal growth factor receptor 2 (HER2) is a tyrosine kinase overexpressed in nearly 20% to 25% of invasive breast cancers. Trastuzumab is a humanized monoclonal antibody that targets HER2. The majority of patients with metastatic breast cancer initially respond to trastuzumab, however, within 1 year of treatment disease progresses. Several molecular mechanisms have been described as contributing to the development of trastuzumab resistance. They could be grouped as impaired access of trastuzumab to HER2, upregulation of HER2 downstream signaling pathways, signaling of alternative pathways, and impaired immune antitumor mechanisms. However, since many of them have overlapping effects, it would be of great clinical impact to identify the principal signaling pathways involved in drug resistance. Significant efforts are being applied to find other therapeutic modalities besides trastuzumab treatment to be used alone or in combination with current modalities.

Copy number increase of HER-2 in colorectal cancers

HER-2 is involved in genetic instability and is overexpressed in a number of human carcinomas, including colorectal cancer (CRC). The choromosomal locus of HER-2, 17q21, is frequently amplified in breast cancer, but the correlation between copy-number variations and HER-2 overexpression in CRC has yet to be elucidated. The functional impact of such regions requires extensive investigation in large numbers of CRC samples. Case-matched tissues of colorectal adenocarcinomas and adjacent normal epithelia (n=134) were included in this study. Quantitative PCR was performed to examine the copy number and mRNA expression of HER-2 in CRC. The results showed that copy number gains of HER-2 were detected in a relatively high percentage of CRC samples (35.1%, 47 out of 134). A positive correlation was noted between the copy number increase of HER-2 and tumor progression. Furthermore, copy number gains of HER-2 showed a positive correlation with mRNA overexpression in CRC. However, the expression levels of HER-2 mRNA were also enhanced in the group of CRC samples with unaltered copy numbers. In conclusion, the findings suggest that a copy number increase of HER-2 is a potential diagnostic indicator for CRC; whether alone or in combination with other markers.

A conformationally constrained peptidomimetic binds to the extracellular region of HER2 protein

Human epidermal growth factor receptor 2 (HER2) is a member of the human epidermal growth factor receptor kinases (other members include EGFR or HER1, HER3, and HER4) that are involved in signaling cascades for cell growth and differentiation. It is well established that HER2-mediated heterodimerization has important implications in cancer. Deregulation of signaling pathways and overexpression of HER2 is known to occur in cancer cells, indicating a role of HER2 in tumorigenesis. Therefore, blocking HER2-mediated signaling has potential therapeutic value. We have designed several peptidomimetics to inhibit HER2-mediated signaling for cell growth. One of the compounds (HERP5, Arg-beta Naph-Phe) exhibited antiproliferative activity with IC(50) values in the micromolar-to-nanomolar range in breast cancer cell lines. Binding of fluorescently labeled HERP5 to HER2 protein was evaluated by fluorescence assay, microscopy, and circular dichroism spectroscopy. Results indicated that HERP5 binds to the extracellular region of the HER2 protein. Structure of the peptidomimetic HERP5 was studied by NMR and molecular dynamics simulations. Based on these results a model was proposed for HER2-EGFR dimerization and possible blocking by HERP5 peptidomimetic using a protein-protein docking method.

Structure-activity relationship of conformationally constrained peptidomimetics for antiproliferative activity in HER2-overexpressing breast cancer cell lines

Human epidermal growth factor receptor 2 (HER2) is a member of the human epidermal growth factor receptor kinases and is involved in a signaling cascade for cell growth and differentiation. It is well established that HER2-mediated heterodimerization has important implications in cancer. Deregulation of signaling pathways and overexpression of HER2 is known to occur in cancer cells, indicating the role of HER2 in tumorigenesis. Therefore, blocking HER2-mediated signaling has potential therapeutic value. We have designed several peptidomimetics to inhibit HER2-mediated signaling for cell growth. One of the compounds (compound 5, Arg-[3-amino-3(1-napthyl)-propionic acid]-Phe) exhibited antiproliferative activity with IC(50) values in the nanomolar to micromolar range in breast cancer cell lines. To further investigate the structure-activity relationship of the compounds, various analogs of compound 5 were designed. Conformational constraints were initiated in the peptidomimetic with introduction of a Pro residue in the peptidomimetic sequence. Results of antiproliferative activity indicated that analogs of compound 5 with C-and N-terminal ends capped (compound 16) and compound 9 with Asp at the C-terminal exhibited antiproliferative activity in the lower micromolar range against breast cancer cell lines. Introduction of conformational constraints such as Pro residue in the sequence or cyclization did not enhance the activity of the peptidomimetic. Competitive binding studies were carried out to evaluate the binding of potent peptidomimetics to HER2-overexpressing cancer cell lines. Results indicated that compounds exhibiting antiproliferative activity in breast cancer cell lines bind to the cells that overexpress HER2 protein.

Passive antibody-mediated immunotherapy for the treatment of malignant gliomas

Despite advances in understanding the molecular mechanisms of brain cancer, the outcome of patients with malignant gliomas treated according to the current standard of care remains poor. Novel therapies are needed, and immunotherapy has emerged with great promise. The diffuse infiltration of malignant gliomas is a major challenge to effective treatment; immunotherapy has the advantage of accessing the entire brain with specificity for tumor cells. Therapeutic immune approaches include cytokine therapy, passive immunotherapy, and active immunotherapy. Cytokine therapy involves the administration of immunomodulatory cytokines to activate the immune system. Active immunotherapy is the generation or augmentation of an immune response, typically by vaccination against tumor antigens. Passive immunotherapy connotes either adoptive therapy, in which tumor-specific immune cells are expanded ex vivo and reintroduced into the patient, or passive antibody-mediated therapy. In this article, the authors discuss the preclinical and clinical studies that have used passive antibody-mediated immunotherapy, otherwise known as serotherapy, for the treatment of malignant gliomas.

Design, synthesis, and docking studies of peptidomimetics based on HER2-herceptin binding site with potential antiproliferative activity against breast cancer cell lines

Epidermal growth factor receptor kinase and the related human epidermal growth factor receptor-2 (HER2, ErbB2) are two growth factor receptors that have implications in cancer. The overexpression or activation of HER2 occurs frequently in breast, ovarian, and lung cancers, making it an important therapeutic target in the treatment of cancer. Blocking HER2-mediated signaling with antibodies or small molecules has been shown to be effective in inhibiting cell growth. After analyzing the crystal structure of the HER2-herceptin complex, several peptidomimetics (HERP5, 6, and 7) were designed to inhibit HER2-mediated signaling for cell growth. We have used an in silico screening method to investigate the chemical diversity of the designed compounds. autodock software was used to dock the different analogs of HERP5 and HERP7 with HER2 protein extracellular domain. A total of 53 compounds were docked to HER2 protein, and their binding modes were analyzed in terms of docking energy, hydrogen bonding, and hydrophobic interactions. Compounds that exhibited low-energy docked structures were chosen for chemical synthesis and biological activity. Two of the compounds (HERP5 and HERP7) exhibited antiproliferative activity, with IC(50) values of 0.396 microm and 0.143 microm, respectively, against SKBR-3 cell lines (breast cancer cell lines) that overexpress HER2 protein.

Borderline HER‐2 breast cancer cases: Histochemical versus real‐time PCR analysis and impact of different cut‐off values

Seventy-one cases that had resulted borderline for HER-2 protein expression at conventional immunohistochemical assay (2+) were assessed for HER-2 gene amplification by real-time PCR and by FISH in accordance with the manufacturer's recommendations (gene amplification with ratio >or=2 in both methods). Thirty-three out of 71 cases (47%) resulted amplified at real-time PCR analysis, whereas 15 cases resulted positive at FISH (21%). Apparently, PCR was more sensitive than FISH in HER-2 determination, only 10 cases resulting amplified in both tests. When the mean ratio value obtained in all PCR experiments was adopted as threshold in determining HER-2 gene amplification, the apparent sensitivity of PCR was reduced but correlation between PCR and FISH results was dramatically increased. Furthermore, when the mean PCR ratio value observed in the FISH-positive group was chosen as threshold, the best agreement between PCR and FISH results was achieved. Therefore, we found that the proposed threshold ratio value of >or=2 is not accurate in separating HER-2 amplified and non-amplified cases. We suggest that the threshold ratio value in PCR tests should be determined in each laboratory using FISH controlled cases. Finally, above certain in-lab generated threshold values, PCR might be proposed as a highly predictive positive test in HER-2 assessment.

Is overexpression of HER-2 a predictor of prognosis in colorectal cancer?

Background

The development of novel chemotherapeutic agents in colorectal cancer has improved survival. Following initial response to chemotherapeutic strategies many patients develop refractory disease. This poses a significant challenge common to many cancer subtypes. Newer agents such as Bevacizumab have successfully targeted the tyrosine kinase receptor epidermal growth factor receptor in metastatic colorectal cancer. Human epidermal growth factor receptor-2 is another member of the tyrosine kinase receptor family which has been successfully targeted in breast cancer. This may play a role in colorectal cancer. We conducted a clinicopathological study to determine if overexpression of human epidermal growth factor receptor-2 is a predictor of outcome in a cohort of patients with colorectal cancer.

Methods

Clinicopathological data and paraffin-embedded specimens were collected on 132 consecutive patients who underwent colorectal resections over a 24-month period at Mayo General Hospital. Twenty-six contained non-malignant disease. Her-2/neu protein overexpression was detected using immunohistochemistry (IHC). The HER-2 4B5 Ventana monoclonal antibody was used. Fluorescent insitu hybridisation (FISH) was performed using INFORM HER-2/Neu Plus. Results were correlated with established clinical and pathological predictors of outcome including TNM stage. Statistical analysis was performed using SPSS version 11.5.

Results

114 were HER-2/Neu negative using IHC, 7 showed barely perceptible positivity (1+), 9 showed moderate staining (2+) and 2 were strongly positive (3+). There was no correlation with gender, age, grade, Dukes' stage, TNM stage, time to recurrence and 5-year survival (p > 0.05). FISH was applied to all 2+ and 3+ cases as well as some negative cases selected at random. Three were amplified (2 were 3+ and 1 was 2+). Similarly, HER-2 gene overexpression did not correlate with established prognostic indicators.

Conclusion

HER-2 protein is over expressed in 11% of colorectal cancer patients. The gene encoding HER-2 is amplified in 3% of cases. Overexpression of HER-2 is not a predictor of outcome. However, patients who over express HER-2 may respond to Herceptin therapy.

Associations between the uptake of 111In-DTPA-trastuzumab, HER2 density and response to trastuzumab (Herceptin) in athymic mice bearing subcutaneous human tumour xenografts

PURPOSE

The purpose of the study was to investigate the associations between uptake of (111)In-DTPA-trastuzumab, tumour HER2 density and response to trastuzumab (Herceptin) of human breast cancer (BC) xenografts in athymic mice.

MATERIALS AND METHODS

The tumour uptake of (111)In-DTPA-trastuzumab in athymic mice bearing BC xenografts with increasing HER2 density (0 to 3+) was evaluated. Specific uptake ratios were established in biodistribution (SUR) and imaging studies (ROI-SUR) using (111)In-labeled mouse IgG ((111)In-DTPA-mIgG). Further corrections were made for circulating radioactivity using tumour-to-blood ratios defined as a localization index (LI) and region-of-interest localization index (ROI-LI), respectively. Mice were treated with trastuzumab (Herceptin). A tumour growth inhibition index (TGI) was calculated and relative TGIs calculated by dividing the TGI of control by that of trastuzumab-treated mice.

RESULTS

Strong, nonlinear associations with HER2 density were obtained if the uptake of (111)In-DTPA-trastuzumab was corrected for nonspecific IgG localization (i.e., SUR; r (2) = 0.99) and circulating radioactivity (i.e., LI; r (2) = 0.87), but without these corrections, the association between HER2 density and tumour uptake was poor (r (2) = 0.22). There was a strong association between ROI-SUR and ROI-LI values and HER2 expression (r (2) = 0.90 and r (2) = 0.95, respectively. All tumours were imaged. Relative TGI values were associated with increasing uncorrected tumour uptake of (111)In-DTPA-trastuzumab but not always with HER2 density (i.e., MCF-HER2-18 cells with trastuzumab-resistance).

CONCLUSION

HER2 expression (0 to 3+) can be differentiated using (111)In-DTPA-trastuzumab, but requires correction of tumour uptake for nonspecific IgG localization and circulating radioactivity. The uncorrected uptake of (111)In-DTPA-trastuzumab was associated with tumour response to trastuzumab.

Development of real-time quantitative reverse transcription-PCR for Her2 detection in peripheral blood from patients with breast cancer

BACKGROUND

Amplification of the Her2neu oncogene is a well known indicator of poor prognosis in breast cancer patients. The implementation into the clinical setting of therapeutical strategies directly targeting the Her2neu gene product, has create the need for the development of non-invasive analytical techniques in order to monitoring minimal residual disease and response to the treatment.

METHODS

To detect the expression of Her2neu mRNA in peripheral blood, we developed a specific real-time quantitative reverse transcription-PCR (QPCR) assay. The analyses were performed on blood samples obtained from 30 breast cancer patients positive for Her2neu overexpression by immunohistochemical analysis (IHC), 10 breast cancer patients negative for Her2neu overexpression, and 24 healthy controls.

RESULTS

Her2neu positive tumors showed a significant increase in mRNA transcripts as compared with both healthy controls (n=24) and Her2neu negative patients (n=10). After establishing a cut-off value, 18 out of the 30 Her2neu positive patient scored positive for Her2neu expression, whereas only 1 out of the 10 Her2neu negative patients was weakly positive.

CONCLUSIONS

Her2neu QPCR is suitable method for Her2neu overexpression detection in peripheral blood from clinical samples of breast cancer patients. QPCR could be used to identify breast cancer patients with poor prognosis and for monitoring response to the therapy.

Mechanisms of disease: understanding resistance to HER2-targeted therapy in human breast cancer

Trastuzumab is a monoclonal antibody targeted against the human epidermal growth factor receptor (HER) 2 tyrosine kinase receptor, which is overexpressed in approximately 25% of invasive breast cancers. The majority of patients with metastatic breast cancer who initially respond to trastuzumab, however, demonstrate disease progression within 1 year of treatment initiation. Preclinical studies have indicated several molecular mechanisms that could contribute to the development of trastuzumab resistance. Increased signaling via the phosphatidylinositol 3-kinase/Akt pathway could contribute to trastuzumab resistance because of activation of multiple receptor pathways that include HER2-related receptors or non-HER receptors such as the insulin-like growth factor 1 receptor, which appears to be involved in a cross-talk with HER2 in resistant cells. Additionally, loss of function of the tumor suppressor PTEN gene, the negative regulator of Akt, results in heightened Akt signaling that leads to decreased sensitivity to trastuzumab. Decreased interaction between trastuzumab and its target receptor HER2, which is due to steric hindrance of HER2 by cell surface proteins such as mucin-4 (MUC4), may block the inhibitory actions of trastuzumab. Novel therapies targeted against these aberrant molecular pathways offer hope that the effectiveness and duration of response to trastuzumab can be greatly improved.

Herceptin: mechanisms of action and resistance

HER-2 is overexpressed in 20-25% of invasive breast cancers and is associated with an aggressive tumor phenotype and reduced survival rate. The HER-2 status of a tumor is the critical determinant of response to the HER-2-targeted antibody Herceptin. Thus, accurate assessment of HER-2 expression levels is essential for identifying breast cancer patients who will benefit from HER-2-targeted therapy. Herceptin combined with chemotherapy increases response rates, time to disease progression, and survival. However, the majority of cancers that initially respond to Herceptin begin to progress again within 1 year. This review describes mechanisms by which Herceptin inhibits cell growth in breast cancers that overexpress HER-2 and highlights possible mechanisms contributing to Herceptin resistance.

Imaging of HER2/neu expression in BT-474 human breast cancer xenografts in athymic mice using [99mTc]-HYNIC-trastuzumab (Herceptin) Fab fragments

OBJECTIVE

To evaluate the ability of trastuzumab (Herceptin) Fab, labelled with (99m)Tc through introduced hydrazinenicotinamide (HYNIC) functionalities, to image HER2/neu-overexpressing human breast cancer xenografts in athymic mice.

METHODS

Fab fragments were produced by immobilized papain digestion of trastuzumab immunoglobulin G (IgG), followed by purification by ultrafiltration. The immunoreactivity of trastuzumab Fab was evaluated by receptor-binding assays against HER2/neu-positive SK-BR-3 human breast cancer cells. Trastuzumab Fab fragments were labelled with (99m)Tc following modification with HYNIC N-hydroxysuccinimide ester. Biodistribution and tumour imaging studies were performed in athymic mice bearing subcutaneous HER2/neu-overexpressing BT-474 human breast cancer xenografts following intravenous injection of 1.1 or 25 MBq of [(99m)Tc]-trastuzumab Fab (30 microg), respectively. The specificity of tumour uptake was assessed by comparison with that of [(99m)Tc]-labelled irrelevant anti-CD33 HuM195 Fab.

RESULTS

Trastuzumab Fab was pure and exhibited preserved immunoreactivity towards SK-BR-3 cells (K(d) = 1.6 x 10(-8) M). Modification with HYNIC diminished its receptor-binding affinity fourfold. [(99m)Tc]-trastuzumab Fab localized avidly and specifically in BT-474 xenografts, achieving a tumour uptake of 10.7% of the injected dose (ID) per gram and a tumour to blood (T/B) ratio of 3 : 1 at 24 h. The tumour uptake and T/B ratio for [(99m)Tc]-trastuzumab Fab were significantly higher than those for control [(99m)Tc]-HuM195 Fab (2.6% ID x g(-1) and 0.9 : 1, respectively; P<0.05). Tumours were imaged as early as 2 h post-injection of [(99m)Tc]-trastuzumab Fab, but were more clearly visualized at 6 and 24 h post-injection.

CONCLUSIONS

[(99m)Tc]-HYNIC-trastuzumab Fab localized specifically in HER2/neu-overexpressing human breast cancer xenografts in athymic mice, allowing imaging of the tumours within the useful lifetime of the radionuclide.

Imaging of HER2/neu-positive BT-474 human breast cancer xenografts in athymic mice using 111In-trastuzumab (Herceptin) Fab fragments

Trastuzumab (Herceptin) Fab were prepared by digestion of intact IgG with immobilized papain, derivatized with diethylenetriaminepentaacetic acid (DTPA) and radiolabeled with (111)In. The dissociation constant (Kd) for binding of Fab to HER2/neu-positive SK-BR-3 human breast cancer cells was two- to threefold higher than for intact IgG (14-36 vs. 8-14 nM). The binding affinity was not significantly decreased after DTPA derivatization (Kd=47 nM). (111)In-trastuzumab Fab localized specifically in HER2/neu-positive BT-474 human breast cancer xenografts in athymic mice with tumor uptake of 7.8+/-0.7% injected dose (ID)/g and tumor/blood ratio of 25.2+/-1.6 at 72 h postinjection compared with 2.7+/-0.7% ID/g and 7.0+/-0.9 for (111)In-HuM195 anti-CD33 Fab (significantly different, P<.001). Small (3-5 mm in diameter) BT-474 tumors were imaged with (111)In-trastuzumab Fab as early as 24 h postinjection.

Drug development for ovarian hyper-stimulation and anti-cancer treatment: blocking of gonadotropin signaling for epiregulin and amphiregulin biosynthesis

Gonadotropins play a crucial role in ovarian homeostasis and fertilization through the activation of the cAMP cascade. However, gonadotropin hyper-stimulation may be associated with higher risk for ovarian cancer development. It has been suggested, that high gonadotropin levels in peritoneal and ovarian cystic fluids of patients suffering from benign ovarian cysts, may lead to malignancy. Moreover, we have recently discovered that gonadotropin stimulation can activate the MAPK cascade in target cells. Using DNA microarray technology and RNA from human granulosa cells, we discovered that stimulation with saturating doses of gonadotropins dramatically elevates activity of genes coding for epiregulin and amphiregulin. These gene products can bind and activate the EGF receptor and ERBB4, which are associated with the development of various cancers such as ovarian, breast endometrial and other non-gynecological malignancies. Gonadotropin receptors are expressed not only in the gonads, but also in non-gonadal tissues and in cancer cells. The discovery that gonadotropins activate certain mitogenic signal transduction pathways, may serve as a guide for novel anti-cancer therapy by (1) specific interference at the receptor level to block the gonadotropic response, or arresting the receptor expression and (2) blocking downstream mitogenic signals generated by these hormones, like attenuation of the expression of epiregulin and amphiregulin that belong to the EGF family, using anti-sense and/or SiRNA techniques targeted to suppress their expression. Moreover, since amphiregulin and epiregulin act as mediators of luteinizing hormone (LH) action in the mammalian ovulatory follicles, regulation of the expression of these factors may open new possibilities in treatment of ovarian malfunction implicated with ovarian hyper-stimulation.

Monoclonal Antibodies Produced by Muscle after Plasmid Injection and Electroporation

Antibodies are useful for the treatment of a variety of diseases. We here demonstrate that mouse muscle produced monoclonal antibodies (mAb) after a single injection of immunoglobulin genes as plasmid DNA. In vivo electroporation of muscle greatly enhanced antibody production. For chimeric antibodies, levels of 50-200 ng mAb/ml serum were obtained but levels declined after 7-14 days due to an immune response against the xenogeneic parts of the antibody. By contrast, fully mouse antibodies persisted in serum for at least 7 months. mAb produced by the muscle had correct structure, specificity, and biological effector functions. The findings were extended to a larger animal, the sheep, in which mAb serum levels of 30-50 ng/ml were obtained. Sustained levels of serum mAb, induced by single injection of Ig genes and electroporation of muscle cells, may offer significant advantages in the treatment of human diseases.

Cytoplasmic p21WAF1/CIP1 expression is correlated with HER-2/ neu in breast cancer and is an independent predictor of prognosis

BACKGROUND

HER-2 (c-erbB2/Neu) predicts the prognosis of and may influence treatment responses in breast cancer. HER-2 activity induces the cytoplasmic location of p21WAFI/CIPI in cell culture, accompanied by resistance to apoptosis. p21WAFI/CIPI is a cyclin-dependent kinase inhibitor activated by p53 to produce cell cycle arrest in association with nuclear localisation of p21WAFI/CIPI. We previously showed that higher levels of cytoplasmic p21WAFI/CIPI in breast cancers predicted reduced survival at 5 years. The present study examined HER-2 and p21WAFI/CIPI expression in a series of breast cancers with up to 9 years of follow-up, to evaluate whether in vitro findings were related to clinical data and the effect on outcome.

METHODS

The CB11 anti-HER2 monoclonal antibody and the DAKO Envision Plus system were used to evaluate HER-2 expression in 73 patients. p21WAFI/CIPI staining was performed as described previously using the mouse monoclonal antibody Ab-1 (Calbiochem, Cambridge, MA, USA).

RESULTS

HER-2 was evaluable in 67 patients and was expressed in 19% of cases, predicting reduced overall survival (P = 0.02) and reduced relapse-free survival (P = 0.004; Cox regression model). HER-2-positive tumours showed proportionately higher cytoplasmic p21WAFI/CIPI staining using an intensity distribution score (median, 95) compared with HER-2-negative cancers (median, 47) (P = 0.005). There was a much weaker association between nuclear p21WAFI/CIPI and HER-2 expression (P = 0.05), suggesting an inverse relationship between nuclear p21WAF1/CIP1 and HER-2.

CONCLUSION

This study highlights a new pathway by which HER-2 may modify cancer behaviour. HER-2 as a predictor of poor prognosis may partly relate to its ability to influence the relocalisation of p21WAFI/CIPI from the nucleus to the cytoplasm, resulting in a loss of p21WAFI/CIPItumour suppressor functions. Cytoplasmic p21WAFI/CIPI may be a surrogate marker of functional HER-2 in vivo.

Role of steroid hormones and growth factors in breast cancer

Breast cancer is the most common cancer in women worldwide and its incidence is increasing. Oestrogens and mitogenic growth factors may play an important role in the development of breast cancer, whereas inhibitory growth factors may prevent the development of breast cancer. Only about 5 to 10% of cases of breast cancer are due to inheritance of mutations in the BRCA1 or BRCA2 tumour suppressor genes. Mutations in the p53 tumour suppressor gene are commonly found in sporadic breast cancers. Retinoic acid and carotenoids may play a protective role in breast cancer since they inhibit the growth of the oestrogen receptor-positive MCF-7 breast cancer cell line. The presence of oestrogen and progesterone receptors predicts the likelihood of benefit from hormonal therapy. Amplification of the c-erbB2 oncogene in breast cancers is associated with a poor prognosis. It is now apparent that there is a complex, productive cross-talk between oestrogen-directed and growth factor-directed pathways which are believed to markedly reinforce their individual cellular effects on growth and gene responses.