OPINION STATEMENT: About 15-20% of patients with early stage breast cancer present with tumors that have overexpression or amplification of the human epidermal growth factor receptor 2 (HER2) gene. Before 2005, these individuals had an increased risk of recurrence and death, but since then their outcomes have substantially improved with the adoption in most countries of adjuvant trastuzumab as a standard component of therapy for HER2-positive early-stage breast cancer. Consequently, access to high-quality and accurate HER2 testing methods is critical to accurately determine HER2 status, guide treatment decisions, and ultimately improve clinical outcomes. In 2012, the humanized monoclonal anti-HER antibody trastuzumab was the only approved HER2-targeted therapy in the adjuvant setting. Data from the first generation of trials combining it with various chemotherapy regimens showed significant improvements in disease-free and overall survival (DFS/OS). Based on results from five randomized clinical trials, a trastuzumab-containing regimen for up to 1 year is now considered standard for all patients with HER2-positive tumors larger than 1 cm in size who would have fulfilled eligibility to those studies, and this recommendation is sometimes extended to patients with stage I tumors greater than 0.5 cm (T1b). Second generation adjuvant studies with other HER2-targeted agents like lapatinib and pertuzumab are ongoing, and newer drugs like T-DM1 and neratinib are being actively tested in the metastatic setting.
Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. The impact factor represents a rough estimation of the journal's impact factor and does not reflect the actual current impact factor. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.
"This receptor tyrosine kinase is part of the epidermal growth factor receptor (EGFR) family, further including HER1 (EGFR), HER3 and HER4 . It is overexpressed in 10–20% of breast tumors, and the related subtype is associated with increased recurrence and mortality rates [2, 3]. The humanized monoclonal antibody trastuzumab targets specifically the extracellular domain of HER2 and is part of the adjuvant treatment of patients with HER2-positive (HER2+) early breast cancer  . "
[Show abstract][Hide abstract]ABSTRACT: Intrinsic and acquired resistance to the monoclonal antibody drug trastuzumab is a major problem in the treatment of HER2-positive breast cancer. A deeper understanding of the underlying mechanisms could help to develop new agents. Our intention was to detect genes and single nucleotide polymorphisms (SNPs) affecting trastuzumab efficiency in cell culture. Three HER2-positive breast cancer cell lines with different resistance phenotypes were analyzed. We chose BT474 as model of trastuzumab sensitivity, HCC1954 as model of intrinsic resistance, and BTR50, derived from BT474, as model of acquired resistance. Based on RNA-Seq data, we performed differential expression analyses on these cell lines with and without trastuzumab treatment. Differentially expressed genes between the resistant cell lines and BT474 are expected to contribute to resistance. Differentially expressed genes between untreated and trastuzumab treated BT474 are expected to contribute to drug efficacy. To exclude false positives from the candidate gene set, we removed genes that were also differentially expressed between untreated and trastuzumab treated BTR50. We further searched for SNPs in the untreated cell lines which could contribute to trastuzumab resistance. The analysis resulted in 54 differentially expressed candidate genes that might be connected to trastuzumab efficiency. 90% of 40 selected candidates were validated by RT-qPCR. ALPP, CALCOCO1, CAV1, CYP1A2 and IGFBP3 were significantly higher expressed in the trastuzumab treated than in the untreated BT474 cell line. GDF15, IL8, LCN2, PTGS2 and 20 other genes were significantly higher expressed in HCC1954 than in BT474, while NCAM2, COLEC12, AFF3, TFF3, NRCAM, GREB1 and TFF1 were significantly lower expressed. Additionally, we inferred SNPs in HCC1954 for CAV1, PTGS2, IL8 and IGFBP3. The latter also had a variation in BTR50. 20% of the validated subset have already been mentioned in literature. For half of them we called and analyzed SNPs. These results contribute to a better understanding of trastuzumab action and resistance mechanisms.
"Lapatinib is the very first orally available epidermal growth factor receptor/human epidermal growth factor receptor 2 (EGFR/HER2) dual kinase inhibitor approved by the FDA. It is now used as a first-line treatment for HER2-positive breast cancers or metastatic breast cancer patients in combination with capecitabine or letrozole (Gomez et al., 2008; Jelovac & Wolff, 2012). Although lapatinib has demonstrated success in the pharmacotherapy of breast cancer, several issues remain in its clinical use. "
[Show abstract][Hide abstract]ABSTRACT: Abstract Mechanism-based inactivation (MBI) of CYP450 enzymes is a unique form of inhibition in which the enzymatic machinery of the victim is responsible for generation of the reactive metabolite. This precondition sets up a time-dependency for the inactivation process, a hallmark feature that characterizes all MBI. Yet, MBI itself is a complex biochemical phenomenon that operates in different modes, namely, covalent binding to apoprotein, covalent binding of the porphyrin group and also complexation of the catalytic iron. Using lapatinib as a recent example of toxicological interest, we present an example of a mixed-function MBI that can confound clinical drug-drug interactions manifestation. Lapatinib exhibits both covalent binding to the apoprotein and formation of a metabolite-intermediate complex in an enzyme-selective manner (CYP3A4 versus CYP3A5), each with different reactive metabolites. The clinical implication of this effect is also contingent upon genetic polymorphisms of the enzyme involved as well as the co-administration of other substrates, inhibitors or inducers, culminating in drug-drug interactions. This understanding recapitulates the importance of applying isoform-specific mechanistic investigations to develop customized strategies to manage such outcomes.
Full-text · Article · Feb 2015 · Drug Metabolism Reviews
"The role of the orphan receptor ErbB-2 in dysregulation of the ErbB network is of major interest, due to its overexpression in 10- 20% of breast tumours, diagnosed as HER2-positive. Furthermore, its role as favoured dimerisation partner independent on ligand-activation implies oncogenic potential303132. The therapeutic antibodies trastuzumab and pertuzumab have especially been designed to target ErbB-2 . "
[Show abstract][Hide abstract]ABSTRACT: Background
Despite promising progress in targeted breast cancer therapy, drug resistance remains challenging. The monoclonal antibody drugs trastuzumab and pertuzumab as well as the small molecule inhibitor erlotinib were designed to prevent ErbB-2 and ErbB-1 receptor induced deregulated protein signalling, contributing to tumour progression. The oncogenic potential of ErbB receptors unfolds in case of overexpression or mutations. Dimerisation with other receptors allows to bypass pathway blockades. Our intention is to reconstruct the ErbB network to reveal resistance mechanisms. We used longitudinal proteomic data of ErbB receptors and downstream targets in the ErbB-2 amplified breast cancer cell lines BT474, SKBR3 and HCC1954 treated with erlotinib, trastuzumab or pertuzumab, alone or combined, up to 60 minutes and 30 hours, respectively. In a Boolean modelling approach, signalling networks were reconstructed based on these data in a cell line and time course specific manner, including prior literature knowledge. Finally, we simulated network response to inhibitor combinations to detect signalling nodes reflecting growth inhibition.
The networks pointed to cell line specific activation patterns of the MAPK and PI3K pathway. In BT474, the PI3K signal route was favoured, while in SKBR3, novel edges highlighted MAPK signalling. In HCC1954, the inferred edges stimulated both pathways. For example, we uncovered feedback loops amplifying PI3K signalling, in line with the known trastuzumab resistance of this cell line. In the perturbation simulations on the short-term networks, we analysed ERK1/2, AKT and p70S6K. The results indicated a pathway specific drug response, driven by the type of growth factor stimulus. HCC1954 revealed an edgetic type of PIK3CA-mutation, contributing to trastuzumab inefficacy. Drug impact on the AKT and ERK1/2 signalling axes is mirrored by effects on RB and RPS6, relating to phenotypic events like cell growth or proliferation. Therefore, we additionally analysed RB and RPS6 in the long-term networks.
We derived protein interaction models for three breast cancer cell lines. Changes compared to the common reference network hint towards individual characteristics and potential drug resistance mechanisms. Simulation of perturbations were consistent with the experimental data, confirming our combined reverse and forward engineering approach as valuable for drug discovery and personalised medicine.
Full-text · Article · Jun 2014 · BMC Systems Biology