Targeting HER proteins in cancer therapy and the role of the non-target HER3

Combination therapy with anti-ErbB3 monoclonal antibodies and EGFR TKIs potently inhibits non-small cell lung cancer

Personalized therapy of advanced non-small cell lung cancer (NSCLC) has been improved by the introduction of EGFR tyrosine kinase inhibitors (TKIs), gefitinib and erlotinib. EGFR TKIs induce dramatic objective responses and increase survival in patients bearing sensitizing mutations in the EGFR intracytoplasmic tyrosine kinase domain. However, virtually all patients develop resistance, and this is responsible for disease relapse. Hence several efforts are being undertaken to understand the mechanisms of resistance in order to develop combination treatments capable to sensitize resistant cells to EGFR TKIs. Recent studies have suggested that upregulation of another member of the EGFR receptor family, namely ErbB3 is involved in drug resistance, through increased phosphorylation of its intracytoplasmic domain and activation of PI3K/AKT signaling. In this paper we first show, by using a set of malignant pleural effusion derived cell cultures (MPEDCC) from patients with lung adenocarcinoma, that surface ErbB3 expression correlates with increased AKT phosphorylation. Antibodies against ErbB3, namely A3, which we previously demonstrated to induce receptor internalization and degradation, inhibit growth and induce apoptosis only in cells overexpressing surface ErbB3. Furthermore, combination of anti-ErbB3 antibodies with EGFR TKIs synergistically affect cell proliferation in vitro, cause cell cycle arrest, up-regulate p21 expression and inhibit tumor growth in mouse xenografts. Importantly, potentiation of gefitinib by anti-ErbB3 antibodies occurs both in de novo and in ab initio resistant cells. Anti-ErbB3 mAbs strongly synergize also with the dual EGFR and HER2 inhibitor lapatinib. Our results suggest that combination treatment with EGFR TKI and antibodies against ErbB3 should be a promising approach to pursue in the clinic.

Targeting of erbB3 receptor to overcome resistance in cancer treatment

The erbB receptors, including the epidermal growth factor receptor (EGFR), erbB2 (also known as HER2/neu), erbB3 (or HER3), and erbB4 (or HER4), are often aberrantly activated in a wide variety of human cancers. They are excellent targets for selective anti-cancer therapies because of their transmembrane location and pro-oncogenic activity. While several therapeutic agents against erbB2 and/or EGFR have been used in the treatment of human cancers with efficacy, there has been relatively less emphasis on erbB3 as a molecular target. Elevated expression of erbB3 is frequently observed in various malignancies, where it promotes tumor progression via interactions with other receptor tyrosine kinases (RTKs) due to its lack of or weak intrinsic kinase activity. Studies on the underlying mechanisms implicate erbB3 as a major cause of treatment failure in cancer therapy, mainly through activation of the PI-3 K/Akt, MEK/MAPK, and Jak/Stat signaling pathways as well as Src kinase. It is believed that inhibition of erbB3 signaling may be required to overcome therapeutic resistance and effectively treat cancers. To date, no erbB3-targeted therapy has been approved for cancer treatment. Targeting of erbB3 receptor with a monoclonal antibody (Ab) is the only strategy currently under preclinical study and clinical evaluation. In this review, we focus on the role of erbB3-initiated signaling in the development of cancer drug resistance and discuss the latest advances in identifying therapeutic strategies inactivating erbB3 to overcome the resistance and enhance efficacy of cancer therapeutics.

HER2/HER3 heterodimers and p21 expression are capable of predicting adjuvant trastuzumab response in HER2+ breast cancer

Human epidermal growth factor receptor 2 (HER2) plays an important role in breast cancer progression and provides predictive information for response to targeted therapy including trastuzumab although this is limited. Downstream pathways, such as PI3K/Akt, are associated with HER2/HER3 heterodimerization promoting survival and proliferation amongst cancer cells. Thus, patient outcome and trastuzumab therapy effectiveness might be further characterised by HER2/HER3 dimerisation and its signalling pathways. HER2/HER3 dimerisation status was assessed, using chromogenic in situ Proximity Ligation Assay, in two breast cancer series: early stage primary breast cancer, including 224 HER2+ patients that were not submitted to trastuzumab, and HER2+ breast cancer where patients were treated with adjuvant trastuzumab (n = 143). Levels of biomarkers including PI3K, pAKT, ER, PgR, HER3, BCL2, p53, PTEN and p21 were measured using immunohistochemistry. Levels of HER2/HER3 heterodimers were compared with biomarker expression and patient outcome. An association between high levels of HER2/HER3 dimerisation and absence of hormone receptors, ER and PgR, was observed. We further show for the first time the presence of HER2/HER3 heterodimers and the loss of p21 expression in HER2+ breast cancer predicts a significantly poorer outcome when submitted to adjuvant trastuzumab. Breast cancer patients that reveal high levels of HER2/HER3 dimerisation and loss of p21 are associated with poor survival prognosis in patients with HER2+ breast cancer treated with adjuvant trastuzumab. Further quantification analysis of HER dimer/ligand complexes and downstream signalling pathways will begin to unravel the complex associations with patient outcome and its relationship with sensitivity to targeted treatment.

The E3 ubiquitin ligase NEDD4 negatively regulates HER3/ErbB3 level and signaling

HER3/ErbB3, a member of the epidermal growth factor receptor (EGFR) family, has a pivotal role in cancer and is emerging as a therapeutic antibody target. In this study, we identified NEDD4 (neural precursor cell expressed, developmentally downregulated 4) as a novel interaction partner and ubiquitin E3 ligase of human HER3. Using molecular and biochemical approaches, we demonstrated that the C-terminal tail of HER3 interacted with the WW domains of NEDD4 and the interaction was independent of neuregulin-1. Short hairpin RNA knockdown of NEDD4 elevated HER3 levels and resulted in increased HER3 signaling and cancer cell proliferation in vitro and in vivo. A similar inverse relationship between HER3 and NEDD4 levels was observed in prostate cancer tumor tissues. More importantly, the upregulated HER3 expression by NEDD4 knockdown sensitized cancer cells for growth inhibition by an anti-HER3 antibody. Taken together, our results suggest that low NEDD4 levels may predict activation of HER3 signaling and efficacies of anti-HER3 antibody therapies.

Lgr5 over-expression is positively related to the tumor progression and HER2 expression in stage pTNM IV colorectal cancer

Recent studies display that Leucine-rich repeat-containing G-protein-coupled receptor 5 (Lgr5) appears to involve the initiation of colorectal cancer (CRC). However, its role in the progression of CRC is not clear at present. In the present study, the expression of Lgr5, HER2, VEGF, and Ki-67 was detected by immunohistochemistry in primary cancer tissue and the matched normal mucosa, metastatic lymph node and distant metastatic tissues in 42 CRC cases staged as pTNM IV. The correlation of Lgr5 over-expression with the CRC progression, survival time, and expression of HER2, VEGF, and Ki-67 was evaluated. Moreover, the Lgr5 expression at the invasive front or residual cancer cells around coagulation necrosis was compared with that at the center of CRC in 51 paraffin embedded tissues. The results revealed that Lgr5 over-expression was more frequently found in the metastatic tissues of both lymph nodes and distant area when compared with primary CRC tissue (P<0.05). Additionally, cancer cells in the invasive front and residual cancer cells around or among the coagulation necrosis presented stronger Lgr5 immunoreactivity than that at tumor center (P<0.05), and strong positive staining was often observed in tumor budding cells. While, HER2 over-expression was detected in 28.9% (IHC 3+) and 42.1% (IHC 3+/2+) of CRC patients, neither Lgr5 nor HER2 expression was significantly related to the prognosis of CRC patients, though there was a positive correlation between Lgr5 and HER2 (P<0.05) or Ki-67 expression (P<0.05). In conclusions, Lgr5 over-expression might involve the proliferation, invasion, and distant and regional metastasis of CRC cells, and has potential positive relation to HER2 expression.

Imaging of HER3-expressing xenografts in mice using a (99m)Tc(CO) 3-HEHEHE-Z HER3:08699 affibody molecule

PURPOSE

Human epidermal growth factor receptor type 3 (HER3) is a transmembrane receptor tyrosine kinase belonging to the HER (ErbB) receptor family. Membranous expression of HER3 is associated with trastuzumab resistance in breast cancer and the transition to androgen independence in prostate cancer. Imaging of HER3 expression in malignant tumors may provide important diagnostic information that can influence patient management. Affibody molecules with low picomolar affinity to HER3 were recently selected. The aim of this study was to investigate the feasibility of HER3 imaging using radiolabeled Affibody molecules.

METHODS

A HER3-binding Affibody molecule, Z08699, with a HEHEHE-tag on N-terminus was labeled with (99m)Tc(CO)3 using an IsoLink kit. In vitro and in vivo binding specificity and the cellular processing of the labeled binder were evaluated. Biodistribution of (99m)Tc(CO)3-HEHEHE-Z08699 was studied over time in mice bearing HER3-expressing xenografts.

RESULTS

HEHEHE-Z08699 was labeled with (99m)Tc(CO)3 with an isolated yield of >80 % and a purity of >99 %. Binding of (99m)Tc(CO)3-HEHEHE-Z08699 was specific to BT474 and MCF7 (breast cancer), and LS174T (colon cancer) cells. Cellular processing showed rapid binding and relatively quick internalization of the receptor/Affibody molecule complex (70 % of cell-associated radioactivity was internalized after 24 h). The tumor targeting was receptor mediated and the excretion was predominantly renal. Receptor-mediated uptake was also found in the liver, lung, stomach, intestine, and salivary glands. At 4 h pi, tumor-to-blood ratios were 7 ± 3 for BT474, and 6 ± 2 for LS174T xenografts. LS174T tumors were visualized by microSPECT 4 h pi.

CONCLUSIONS

The results of this study suggest the feasibility of HER3-imaging in malignant tumors using Affibody molecules.

Role of erbB3 receptors in cancer therapeutic resistance

ErbB3 receptors are unique members of the erbB receptor tyrosine kinases (RTKs), which are often aberrantly expressed and/or activated in human cancers. Unlike other members in the family, erbB3 lacks or has impaired kinase activity. To transduce cell signaling, erbB3 has to interact with other RTKs and to be phosphorylated by its interactive partners, of those, erbB2 is the most important one. ErbB3 is frequently co-expressed with other RTKs in cancer cells to activate oncogenic signaling, such as phosphoinositide-3-kinase/protein kinase B (Akt) pathway, mitogen-activated protein kinase kinase (MEK)/mitogen-activated protein kinase (MAPK) pathway, Janus kinase (Jak)/signal transducer and activator of transcription (Stat) pathway, etc. and thereby promote tumorigenesis. Numerous studies have demonstrated that activation of erbB3 signaling plays an important role in the progression of a variety of tumor types, such as erbB2-overexpressing breast cancer, castration-resistant prostate cancer, platinum refractory/resistant ovarian cancer, epidermal growth factor receptor TKI-resistant non-small-cell lung cancer, and others. Basic research on the underlying mechanisms implicated the functions of erbB3 as a major cause of treatment failure in cancer therapy. Thus, concomitant inhibition of erbB3 is thought to be required to overcome the resistance and to effectively treat human cancers. This review focuses on the latest advances in our understanding of erbB3-initiated signaling in the development of resistance to cancer treatments.

Unraveling trastuzumab and lapatinib inefficiency in gastric cancer: Future steps (Review)

The newly developed concept of oncogene addiction provides a rationale for the use of targeted therapies. In sharp contrast to the field of breast cancer treatment, attempts to target human epidermal growth factor receptor 2 (HER2) among gastric cancer (GC) patients have been unsatisfactory. The ToGA trial reported only a modest prolongation of progression-free survival (PFS) with trastuzumab and the subsequent TYTAN and LOGiC trials failed to demonstrate any survival advantage with lapatinib. These results suggest that a response to the molecular-targeted therapies is achieved in only a fraction of the patients; in addition, even responders may experience secondary resistance, with the efficacy of the treatment being decreased or abrogated over a short period of time. Considering the increased recognition of primary or acquired resistance, recent investigations on targeted therapies have been primarily focused on determining in advance the mechanisms that may mediate resistance to treatment and the methods through which such obstacles may be circumvented. The proposed molecules or mechanisms that may be responsible for the development of resistance to single HER2-targeted therapy include a dimerization partner or crosstalk with HER2, such as HER3 and MET, as well as any subsequent activation of their downstream pathways, which exhibit a partial overlap with those of HER2. Furthermore, genetic alterations that stimulate the aberrant activation of the pathways downstream of HER2 may be the underlying mechanisms that restore prosurvival signaling. These mechanisms generate a complex signaling network with a significant potential for signal amplification and diversification. Although in the early stages of description, several compounds have been suggested as next generation treatments for GC, with expectations for their delineating the function of such receptors or molecules, with subsequent contributions of specific survival signaling blockades. This review focuses on the current achievements of anti-HER2 therapies in GC and the plausible mechanisms of resistance to these therapies. Elucidating these mechanisms of resistance may provide valuable information pertinent to the design of future strategies to improve molecular-targeted therapies.

Breast cancer: current and future endocrine therapies

Endocrine therapy forms a central modality in the treatment of estrogen receptor positive breast cancer. The routine use of 5 years of adjuvant tamoxifen has improved survival rates for early breast cancer, and more recently has evolved in the postmenopausal setting to include aromatase inhibitors. The optimal duration of adjuvant endocrine therapy remains an active area of clinical study with recent data supporting 10 years rather than 5 years of adjuvant tamoxifen. However, endocrine therapy is limited by the development of resistance, this can occur by a number of possible mechanisms and numerous studies have been performed which combine endocrine therapy with agents that modulate these mechanisms with the aim of preventing or delaying the emergence of resistance. Recent trial data regarding the combination of the mammalian target of rapamycin (mTOR) inhibitor, everolimus with endocrine therapy have resulted in a redefinition of the clinical treatment pathway in the metastatic setting. This review details the current endocrine therapy utilized in both early and advanced disease, as well as exploring potential new targets which modulate pathways of resistance, as well as agents which aim to modulate adrenal derived steroidogenic hormones.

Canine pulmonary adenocarcinoma tyrosine kinase receptor expression and phosphorylation

BACKGROUND

This study evaluated tyrosine kinase receptor (TKR) expression and activation in canine pulmonary adenocarcinoma (cpAC) biospecimens. As histological similarities exist between human and cpAC, we hypothesized that cpACs will have increased TKR mRNA and protein expression as well as TKR phosphorylation. The molecular profile of cpAC has not been well characterized making the selection of therapeutic targets that would potentially have relevant biological activity impossible. Therefore, the objectives of this study were to define TKR expression and their phosphorylation state in cpAC as well as to evaluate the tumors for the presence of potential epidermal growth factor receptor (EGFR) tyrosine kinase activating mutations in exons 18-21. Immunohistochemistry (IHC) for TKR expression was performed using a tissue microarray (TMA) constructed from twelve canine tumors and companion normal lung samples. Staining intensities of the IHC were quantified by a veterinary pathologist as well as by two different digitalized algorithm image analyses software programs. An antibody array was used to evaluate TKR phosphorylation of the tumor relative to the TKR phosphorylation of normal tissues with the resulting spot intensities quantified using array analysis software. Each EGFR exon PCR product from all of the tumors and non-affected lung tissues were sequenced using sequencing chemistry and the sequencing reactions were run on automated sequencer. Sequence alignments were made to the National Center for Biotechnology Information canine EGFR reference sequence.

RESULTS

The pro-angiogenic growth factor receptor, PDGFRα, had increased cpAC tumor mRNA, protein expression and phosphorylation when compared to the normal lung tissue biospecimens. Similar to human pulmonary adenocarcinoma, significant increases in cpAC tumor mRNA expression and receptor phosphorylation of the anaplastic lymphoma kinase (ALK) tyrosine receptor were present when compared to the corresponding normal lung tissue. The EGFR mRNA, protein expression and phosphorylation were not increased compared to the normal lung and no activating mutations were identified in exons 18-21.

CONCLUSIONS

Canine pulmonary adenocarcinoma TKRs are detected at both the mRNA and protein levels and are activated. Further investigation into the contribution of TKR activation in cpAC tumorigenesis is warranted.

Prognostic value of epidermal growth factor receptors in gastric cancer: a survival analysis by Weibull model incorporating long-term survivors

BACKGROUND

There is no consensus about the prognostic role of HER2 expression and that of other members of the EGFR family in gastric cancer patients. The aim of this study was to evaluate the prognostic value of the EGFR family in gastric cancer.

METHODS

This retrospective study included 201 patients with gastric and esophagogastric junction adenocarcinoma stages 0-IV (AJCC 6th edition) who underwent primary tumor resection. Tissues from primary tumors were analyzed by tissue microarray technology and immunohistochemistry. Correlations between receptor expression and clinicopathological characteristics were performed according to the chi-square test. Survival analysis was calculated according to the Weibull model with a mixture model incorporating long-term survivors. Multivariate analysis of prognostic factors was performed by a regression model incorporating long-term survivors with the Weibull distribution.

RESULTS

Membrane expression of HER1, HER2, and HER4 were 9, 17, and 15 %, respectively. No membrane expression of HER3 was observed. Cytoplasmic expression of HER1, HER3, and HER4 were 45, 62, and 24 %, respectively. HER2 and HER3 expression were correlated (p < 0.001) and associated with intestinal-type histology (p = 0.001 and p < 0.001, respectively) and advanced age (p = 0.011 and p = 0.008, respectively). According to a regression model adjusted for age, surgical radicality, surgical modality, Laurén histology, adjuvant therapy, TNM stage, and receptor expressions, only TNM stage showed prognostic influence.

CONCLUSIONS

According to analysis by a parametric model, the EGFR family did not have prognostic influence in the gastric cancer population studied. The data presented showed a correlation between HER2 and HER3 expression, which might suggest a potential role for HER2-HER3 heterodimerization inhibitors.

The progress of targeted therapy in advanced gastric cancer

Although palliative chemotherapy has been shown to prolong survival and improve quality of life, the survival of advanced gastric cancer (AGC) patients remains poor. With the advent of targeted therapy, many molecular targeted agents have been evaluated in clinical studies. Trastuzumab, an anti-HER2 monoclonal antibody, has shown activity against HER2-positive AGC and becomes the first targeted agent approved in AGC. Drugs that target epidermal growth factor receptor, including monoclonal antibody and tyrosine kinase inhibitor, do not bring survival benefit to patients with AGC. Additionally, vascular endothelial growth factor inhibitors are also under investigation. Ramucirumab has shown promising result. Other targeted agents are in preclinical or early clinical development, such as mammalian target of rapamycinm inhibitors and c-MET inhibitors.

Monoclonal antibody therapeutics with up to five specificities: functional enhancement through fusion of target-specific peptides

The recognition that few human diseases are thoroughly addressed by mono-specific, monoclonal antibodies (mAbs) continues to drive the development of antibody therapeutics with additional specificities and enhanced activity. Historically, efforts to engineer additional antigen recognition into molecules have relied predominantly on the reformatting of immunoglobulin domains. In this report we describe a series of fully functional mAbs to which additional specificities have been imparted through the recombinant fusion of relatively short polypeptides sequences. The sequences are selected for binding to a particular target from combinatorial libraries that express linear, disulfide-constrained, or domain-based structures. The potential for fusion of peptides to the N- and C- termini of both the heavy and light chains affords the bivalent expression of up to four different peptides. The resulting molecules, called zybodies, can gain up to four additional specificities, while retaining the original functionality and specificity of the scaffold antibody. We explore the use of two clinically significant oncology antibodies, trastuzumab and cetuximab, as zybody scaffolds and demonstrate functional enhancements in each case. The affect of fusion position on both peptide and scaffold function is explored, and penta-specific zybodies are demonstrated to simultaneously engage five targets (ErbB2, EGFR, IGF-1R, Ang2 and integrin αvβ3). Bispecific, trastuzumab-based zybodies targeting ErbB2 and Ang2 are shown to exhibit superior efficacy to trastuzumab in an angiogenesis-dependent xenograft tumor model. A cetuximab-based bispecific zybody that targeting EGFR and ErbB3 simultaneously disrupted multiple intracellular signaling pathways; inhibited tumor cell proliferation; and showed efficacy superior to that of cetuximab in a xenograft tumor model.

BAY 80-6946 is a highly selective intravenous PI3K inhibitor with potent p110α and p110δ activities in tumor cell lines and xenograft models

Because of the complexity derived from the existence of various phosphoinositide 3-kinase (PI3K) isoforms and their differential roles in cancers, development of PI3K inhibitors with differential pharmacologic and pharmacokinetic profiles would allow best exploration in different indications, combinations, and dosing regimens. Here, we report BAY 80-6946, a highly selective and potent pan-class I PI3K inhibitor with sub-nanomolar IC50s against PI3Kα and PI3Kδ. BAY 80-6946 exhibited preferential inhibition (about 10-fold) of AKT phosphorylation by PI3Kα compared with PI3Kβ in cells. BAY 80-6946 showed superior antitumor activity (>40-fold) in PIK3CA mutant and/or HER2 overexpression as compared with HER2-negative and wild-type PIK3CA breast cancer cell lines. In addition, BAY 80-6946 revealed potent activity to induce apoptosis in a subset of tumor cells with aberrant activation of PI3K as a single agent. In vivo, single intravenous administration of BAY 80-6946 exhibited higher exposure and prolonged inhibition of pAKT levels in tumors versus plasma. BAY 80-6946 is efficacious in tumors with activated PI3K when dosed either continuously or intermittently. Thus, BAY 80-6946 induced 100% complete tumor regression when dosed as a single agent every second day in rats bearing HER2-amplified and PIK3CA-mutated KPL4 breast tumors. In combination with paclitaxel, weekly dosing of BAY 80-6946 is sufficient to reach sustained response in all animals bearing patient-derived non-small cell lung cancer xenografts, despite a short plasma elimination half-life (1 hour) in mice. Thus, BAY 80-6946 is a promising agent with differential pharmacologic and pharmacokinetic properties for the treatment of PI3K-dependent human tumors.

The siRNA cocktail targeting VEGF and HER2 inhibition on the proliferation and induced apoptosis of gastric cancer cell

The aim of this study was to investigate the inhibitory effect of a siRNA cocktail targeting Vascular endothelial growth factor (VEGF) and Human epidermal growth factor receptor 2 (HER2) on cell proliferation, induced apoptosis and the expression of VEGF and HER2 in human gastric carcinoma cell. The silencing rate of pre-designed siRNAs that targeted VEGF and HER2 was detected by Real-time Quantitative PCR (RT-QPCR) analysis. Furthermore, the best silencing siRNA that targeted VEGF and HER2 was prepared as a cocktail to co-knockdown VEGF and HER2 expression at both mRNA and protein levels which were detected by RT-QPCR and Western blot analysis. Cell proliferation inhibition rates were determined by CCK8 assay. The effect of siRNA cocktail on cell apoptosis was determined by flow cytometry. The migration inhibition of siRNA cocktail was analyzed by wound-healing assay. The ability of VEGF to induce endothelial cells to proliferate was examined in HUVECs by the method of tube formation assay. The pre-designed siRNAs could inhibit VEGF and HER2 mRNA level. siRNA cocktail, and co-downregulation of VEGF and HER2 result in significant inhibition of gastric cancer growth and migration in vitro. The inhibition of VEGF and HER2 expressions can induce apoptosis of SGC-7901 cells.

Co-expression of receptors of the HER family correlates with clinical outcome in non-small cell lung cancer (NSCLC)

HER family receptors play a critical role in lung carcinogenesis. There is a growing body of evidence showing that cooperation between them contributes to a more aggressive tumor phenotype and impacts on their response to targeted therapy. We explored immunohistochemical co-expression of HER family receptors (HER1, HER2, HER3, HER4) and its potential role as prognostic factor in resected non-small cell lung cancer (NSCLC). Expression of HER family receptors was assessed by immunohistochemistry on 125 surgically resected NSCLC. Kaplan-Meier estimates of overall survival (OS), disease-free survival (DFS), and time to recurrence were calculated for clinical variables and HER expression, using the Cox model for multivariate analysis. HER1 and HER3 expression was detected more frequently in squamous cell carcinoma (p = 0.002 and p = <0.001, respectively). HER4 was more often expressed in patients older than 60 years (p = 0.02) and in tumors of low histological grade (p = 0.04). Cases which expressed only HER1 had a worse DFS (p = 0.01) and OS (p = 0.01) compared to cases expressing HER1 and one or more of the other family members and to cases which did not express HER1 but one of the other HERs. By multivariate analysis, stage was an independent prognostic factor for DFS and OS. Furthermore, different patterns of co-expression of HER family receptors showed a statistically significant correlation with a shorter DFS (p = 0.03) and OS (p = 0.02). Our findings suggest that expression of HER1 only is correlated with worse DFS and OS. A better understanding of the functional relationships between these receptors may lead to a useful predictive indicator of response to targeted therapy.

Role of phospholipase C in cell invasion and metastasis

Phospholipases are enzymes that use phospholipids as substrate and are classified in three major classes A, C and D based on the reaction they catalyse. Phosphatidylinositol-specific Phospholipase C enzymes utilize phosphatidylinositol 4,5-bisphosphate as substrate and cleave the bond between the glycerol and the phosphate to produce important second messenger such as inositol trisphosphate and diacylglycerol. The Phospholipase C members are the most well-known phospholipases for their role in lipid signalling and cell proliferation and comprise 13 isoforms classified in 6 distinct sub-families. In particular, signalling activated by Phospholipase C γ, mostly activated by receptor and non-receptor tyrosine kinases, is well characterized in different cell systems. Increasing evidence suggest that Phospholipase C γ plays a key role in cell migration and invasion. Because of its role in cell growth and invasion, aberrant Phospholipase C γ signalling can contribute to carcinogenesis. A major challenge facing investigators who seek to target Phospholipase C γ directly is the fact that it is considered an "undruggable" protein. Indeed, isoform specificity and toxicity represents a big hurdle in the development of Phospholipase C γ small molecule inhibitors. Therefore, a future development in the field could be the identification of interacting partners as therapeutic targets that could be more druggable than Phospholipase C γ.

Activation of an early feedback survival loop involving phospho-ErbB3 is a general response of melanoma cells to RAF/MEK inhibition and is abrogated by anti-ErbB3 antibodies

Background

Treatment of advanced melanoma has been improved with the advent of the BRAF inhibitors. However, a limitation to such treatment is the occurrence of resistance. Several mechanisms have been identified to be responsible for the development of resistance, either MEK-dependent or MEK-independent. In order to overcome resistance due to reactivation of MEK signaling, MEK inhibitors are being clinically developed with promising results. However, also in this case resistance inevitably occurs. It has been recently reported that ErbB3, a member of the EGFR receptor family, may be involved in the establishment of drug resistance.

Methods

Three melanoma cell lines were tested: LOX IMVI (BRAF V600E), MST-L (BRAF V600R) and WM266 (BRAF V600D). Phosphorylation of Receptor Tyrosine Kinases (RTKs) was assessed by an RTK array. Western blot analysis was performed on total protein extracts using anti-ErbB3, anti-AKT and anti-ERK 1/2 antibodies. The expression of neuregulin after vemurafenib treatment was assessed by Real Time PCR and Western blotting. The growth inhibitory effects of vemurafenib, GSK1120212b and/or anti-ErbB3 mAbs were evaluated by in vitro colony formation assays.

Results

In the present study we demonstrate that ErbB3 is the main RTK undergoing rapidly hyperphosphorylation upon either treatment with a BRAF inhibitor or with a MEK inhibitor in a panel of melanoma cell lines harboring a variety of V600BRAF mutations and that this results in a strong activation of phospho-AKT. Importantly, ErbB3 activation is fully abrogated by the simultaneous use of anti-ErbB3 monoclonal antibodies, which are also shown to potently synergize with BRAF inhibitors in the inactivation of both AKT and ERK pathways and in the inhibition of melanoma cell growth. We show that upregulation of phospho-ErbB3 is due to an autocrine loop involving increased transcription and production of neuregulin by melanoma cells.

Conclusions

On the basis of these results, we propose that initial co-treatment with BRAF and/or MEK inhibitors and anti-ErbB3 antibodies should be pursued as a strategy to reduce the ErbB3-dependent feedback survival mechanism and enhance duration of clinical response.

Epidermal growth factor receptor expression and KRAS and BRAF mutations: study of 39 sinonasal intestinal-type adenocarcinomas

Sinonasal intestinal-type adenocarcinomas (ITACs) are uncommon tumors of poor prognosis defined by their similarities to colorectal adenocarcinomas. The involvement of the epidermal growth factor receptor (EGFR) pathway in colorectal adenocarcinoma oncogenesis is well established, and the same is expected to apply to ITACs. In a series of 39 ITACs, we investigated EGFR amplification and chromosome 7 polysomy by fluorescence in situ hybridization; EGFR, KRAS, and BRAF mutational status by polymerase chain reaction sequencing; EGFR variant messenger RNA expression by quantitative reverse transcriptase polymerase chain reaction; and EGFR protein expression by immunohistochemistry with antibodies targeting the extracellular domain, the intracellular domain, and the phosphorylated isoform. The findings were analyzed with respect to clinical data, histologic typing, and patient outcome. EGFR amplification was observed in 3 cases with a focal distribution. EGFR proteins were overexpressed in all these foci with both extracellular domain and intracellular domain antibodies, suggesting involvement of the whole receptor. Chromosome 7 polysomy was observed in 15 cases and was not associated with EGFR protein expression. EGFR, KRAS, or BRAF mutations were observed in 5 different cases. The EGFRvIII mutant was not detected. In all cases, EGFR variants were expressed. There was no association between these molecular features and patient survival. In conclusion, (1) our study revealed various EGFR expression patterns in ITACs, indicating tumor heterogeneity; (2) EGFR amplification should be distinguished from chromosome 7 polysomy; (3) fluorescence in situ hybridization analysis could be guided by immunohistochemistry; and (4) ITACs share common alterations of the EGFR pathway with colorectal adenocarcinomas, except for a lower frequency of KRAS and BRAF mutations.

HER3 status by immunohistochemistry is correlated with poor prognosis in hormone receptor-negative breast cancer patients

Breast cancer is a highly heterogeneous malignancy. The triple-negative breast cancer (TNBC) and human epidermal growth factor receptor 2 (HER2) breast cancer subtypes are highly aggressive and are associated with a poor prognosis. The therapeutic targets for TNBC remain undefined, and many patients with the HER2 subtype acquire resistance to therapy after prolonged treatment. The objective of this study was to evaluate the prognostic significance of HER3 expression in invasive breast carcinoma. We established matched tissue microarray (TMA) blocks and clinical data from 950 cases of invasive breast carcinoma with long-term clinical follow-up data (median 109.7 months). Using the TMAs, we characterized the expression of ER, PR, HER2, EGFR, and HER3 by immunohistochemistry. Each case was classified as one of four IHC-based subtypes based on the expression of hormonal receptor (HR) and HER2. The clinicopathological characteristics and survival of 950 patients were analyzed by subtype. In the TNBC subtype, the HER3(+) group showed poorer disease-free survival (DFS, P = 0.010) and overall survival (OS, P = 0.015) than the HER3(-) group. In the HER2 subtype, the HER3(+) group also showed poorer DFS (P = 0.022) and OS (P = 0.077) than the HER3(-) group. However, there was no difference in patients with HR-positive breast cancer. HER3 expression was associated with poor DFS in both the TNBC and HER2 subtypes and poor OS in the TNBC subtype. HER3 overexpression is an important prognostic marker in hormone receptor-negative breast cancer, and further study is needed to clarify the role of HER-3 targeted treatment.

Activating Mutations in ERBB2 and Their Impact on Diagnostics and Treatment

Despite the ongoing “war on cancer,” cancer remains one of the major causes of human morbidity and mortality. A new paradigm of targeted therapies holds the most promise for the future, making identification of tumor-specific therapeutic targets of prime importance. ERBB2/HER2, best known for its role in breast cancer tumorigenesis, can be targeted by two types of pharmacological manipulation: antibody therapy against the extracellular receptor domain and small molecule compounds against the intracellular tyrosine kinase domain. Aberrant activation of ERBB2 by gene amplification has been shown to participate in the pathophysiology of breast, ovarian, gastric, colorectal, lung, brain, and head and neck tumors. However, the advent of next-generation sequencing technologies has enabled efficient identification of activating molecular alterations of ERBB2. In this review, we will focus on the functional role of these somatic mutations that cause ERBB2 receptor activation. We will additionally discuss the current preclinical and clinical therapeutic strategies for targeting mutationally activated ERBB2.

Targeted therapies of metastatic breast cancer: relationships with cancer stem cells

In the last years, many targeted agents have been developed for metastatic breast cancer (MBC) treatment and are being tested in clinical trials. In spite of this, apart from epidermal growth factor receptor 2 (HER2) positive subset, no significant increase in the median overall survival (OS) has been reported. Similarly to conventional chemo- and radiotherapy, the cancer stem cell theory has been evoked to explain the frustrating results often obtained with this emerging category of drugs. This review examines the results in MBC of the approved targeted therapies or those currently under evaluation in experimental studies or in clinical trials, in the light of their relationships with breast CSCs and of the efforts to circumvent the development of resistance. In the next, there is the principal need to investigate if the effects on CSCs may be used to overcome cancer resistance and it will be opportune to consider whether molecular targeted therapies should be used alone or combined with conventional therapy, or with a different target drug specific for CSCs.

mTOR inhibitors in advanced breast cancer: ready for prime time?

Current therapeutic approaches for advanced breast cancer frequently target receptors mediating cell survival and proliferation, such as the estrogen receptor and/or progesterone receptor and human epidermal growth factor receptor-2. Although these approaches are effective for many patients, treatment resistance is common. Therefore, new treatment approaches are needed for patients with advanced breast cancer. Mammalian target of rapamycin is a highly conserved serine-threonine kinase that acts as a major signaling hub that integrates and synergizes with cellular proliferation, survival, and/or motility signals mediated by estrogen receptor, human epidermal growth factor receptor-2, and other receptor tyrosine kinases. Dysregulation of mammalian target of rapamycin signaling occurs in various tumor types, including breast cancer, and has been associated with cancer pathogenesis, disease progression, and treatment resistance. Recent clinical trials show that combined inhibition of mammalian target of rapamycin and estrogen receptor represents an effective strategy for treating hormone receptor-positive advanced breast cancer progressing on nonsteroidal aromatase inhibitor therapy, and data from ongoing trials combining mammalian target of rapamycin inhibition with human epidermal growth factor receptor-2-targeted therapy are awaited. This review focuses on the molecular rationale underlying strategies to enhance sensitivity to treatment in hormone receptor-positive and human epidermal growth factor receptor-2-positive advanced breast cancer, the clinical efficacy of such approaches, and future perspectives.

The promise of anti-ErbB3 monoclonals as new cancer therapeutics

In the last 3-5 years strong evidence has been gathered demonstrating ErbB3 as a key node for the progression of several cancer types. From the mechanistic standpoint the intracellular region of this receptor is rich of tyrosine residues that, upon phosphorylation, become high affinity binding sites for PI3K and other proteins involved in signal transduction. The involvement of ErbB3 occurs at different levels, most likely as a consequence of its promiscuity in the interaction with other RTKs of the same or other families. Several efforts are therefore being put in the development of antibodies that target this receptor either singly or in combination with other synergizing receptors. Some of these compounds have already entered clinical development. Although clinical proof-of-concept has not yet been achieved, this is likely to occur soon and will further accelerate the inclusion of anti-ErbB3 monoclonals in the repertoire of anticancer agents for more effective combination therapy. In this paper we review the wealth of anti-ErbB3 antibodies under development and compare their properties and potential to become marketed drugs.

Downregulation of HER3 by a novel antisense oligonucleotide, EZN-3920, improves the antitumor activity of EGFR and HER2 tyrosine kinase inhibitors in animal models

Among the four human EGF receptor (HER) family members (EGFR, HER2, HER3, HER4), HER3 is of particular interest as it interacts with HER2 and EGFR via heterodimerization and is a key link to the phosphoinositide 3-kinase (PI3K)/AKT signal transduction axis. Recent studies indicate that HER3 plays a critical role in mediating resistance to agents that target EGFR or HER2. As HER3 lacks significant kinase activity and cannot be inhibited by tyrosine kinase inhibitors, neutralizing antibodies and alternative inhibitors of HER3 have been sought as cancer therapeutics. We describe here a locked nucleic acid (LNA)-based HER3 antisense oligonucleotide, EZN-3920, that specifically downmodulated the expression of HER3, which was associated with growth inhibition. EZN-3920 effectively downmodulated HER3 expression, HER3-driven PI3K/AKT signaling pathway, and growth in tumors derived from BT474M1 breast and HCC827 lung carcinoma cell lines, which overexpress HER2 and EGFR, respectively. Furthermore, when EZN-3920 was coadministered with gefitinib or lapatinib in xenograft tumor models, enhanced antitumor activity compared with the effect of monotherapy was found. The effect was associated with a blockade of induced HER3 mRNA expression caused by lapatinib or gefitinib treatment. Finally, EZN-3920 sustained its antiproliferative effect in trastuzumab-resistant cells and three independently derived gefitinib-resistant cells. Our findings show that downmodulation of HER3 by EZN-3920 leads to the suppression of tumor growth in vitro and in vivo, suggesting that HER3 can be an effective target for the treatment of various cancers that have been activated by HER3 alone or where HER3 activation is associated with EGFR or HER2 expression.

Investigational therapies targeting the ErbB (EGFR, HER2, HER3, HER4) family in GI cancers

INTRODUCTION

Gastrointestinal (GI) malignancies account for nearly one-fourth of all cancer-related deaths in the United States and approximately 30% of all cancer-related deaths worldwide. Use of combination cytotoxic therapy offers a modest improvement in survival, but the prognosis and long-term survival of most patients with GI cancer remains poor. In certain GI malignancies, therapies that target members of the HER family of receptors have positively impacted patient care.

AREAS COVERED

In this review, we discuss the significance of the HER family of receptors in esophagogastric, hepatobiliary, pancreatic, and colorectal cancers and explain the rationale supporting the use of monoclonal antibodies (mAbs) and small molecule tyrosine kinase inhibitors (TKIs) to inhibit HER activation and downstream events that contribute to tumor proliferation, migration, and survival.

EXPERT OPINION

Despite recent advances, the treatment of GI cancers remains challenging. Therapies targeting the HER family of receptors have been extensively studied in these malignancies with inconsistent results. The rationale behind varied tumor responses with these agents remains uncertain. We believe that additional studies are needed to identify biomarkers that could help identify a population of patients who would be more responsive to a given therapy.

Analysis of bypass signaling in EGFR pathway and profiling of bypass genes for predicting response to anticancer EGFR tyrosine kinase inhibitors

Some drugs, such as anticancer EGFR tyrosine kinase inhibitors, elicit markedly different clinical response rates due to differences in drug bypass signaling as well as genetic variations of drug target and downstream drug-resistant genes. The profiles of these bypass signaling are expected to be useful for improved drug response prediction, which have not been systematically explored previously. In this work, we searched and analyzed 16 literature-reported EGFR tyrosine kinase inhibitor bypass signaling routes in the EGFR pathway, which include 5 compensatory routes of EGFR transactivation by another receptor, and 11 alternative routes activated by another receptor. These 16 routes are reportedly regulated by 11 bypass genes. Their expression profiles together with the mutational, amplification and expression profiles of EGFR and 4 downstream drug-resistant genes, were used as new sets of biomarkers for identifying 53 NSCLC cell-lines sensitive or resistant to EGFR tyrosine kinase inhibitors gefitinib, erlotinib and lapatinib. The collective profiles of all 16 genes distinguish sensitive and resistant cell-lines are better than those of individual genes and the combined EGFR and downstream drug resistant genes, and their derived cell-line response rates are consistent with the reported clinical response rates of the three drugs. The usefulness of cell-line data for drug response studies was further analyzed by comparing the expression profiles of EGFR and bypass genes in NSCLC cell-lines and patient samples, and by using a machine learning feature selection method for selecting drug response biomarkers. Our study suggested that the profiles of drug bypass signaling are highly useful for improved drug response prediction.

HER3 overexpression and survival in solid tumors: a meta-analysis

BACKGROUND

The human epidermal growth factor receptor 3 (HER3) is an ErbB/HER family member that dimerizes with other ErbB receptors such as HER2. Numerous agents against HER3 are in clinical development despite variable data for the prognostic impact of HER3 expression. Here we report a meta-analysis of the association of HER3 expression and survival in solid tumors.

METHODS

PubMed was searched for studies evaluating expression of HER3 (as measured by immunohistochemistry) and overall survival (OS) in solid tumors. Published data were extracted and computed into odds ratios (ORs) for death at 3 and 5 years. Data were pooled using the Mantel-Haenszel random-effect model. All statistical tests were two-sided.

RESULTS

Analysis included 12 studies: three that evaluated colorectal cancer, two that evaluated gastric cancer, two that evaluated breast cancer, and one each that evaluated melanoma, ovarian cancer, head and neck cancer, pancreatic cancer, and cervical cancer. The median percentage of cancers with HER3 overexpression was 42.2%. HER3 was associated with worse OS at both 3 years (OR = 2.24, 95% confidence interval [CI] = 1.77 to 2.83, P < .001) and 5 years (OR = 2.20, 95% CI = 1.75 to 2.76, P < .001). Among studies with common HER2 overexpression (breast, gastric, and ovarian cancers), the magnitude of effect of HER3 on OS was statistically significantly greater for both 3-year OS (OR = 3.12, 95% CI = 2.24 to 4.37) and 5-year OS (OR = 2.84, 95% CI = 2.09 to 3.88).

CONCLUSIONS

Expression of HER3 is associated with worse survival in solid tumors. The influence of HER3 may be greater in those tumors where HER2 is commonly overexpressed.

Advances in Targeting HER3 as an Anticancer Therapy

HER3 (ErbB3) is a unique member of the human epidermal growth factor receptor (EGFR) family (ErbB family). It functions only through dimerization with other members of the ErbB family and modulates activity and sensitivity to targeted cancer therapies. This paper briefly describes the mechanism of HER3 in signal transduction and its potential role in acquired resistance to EGFR- and HER2-targeted therapies. We also consider recent developments in HER3-targeting therapeutics and their combination with inhibitors of other ErbB members in clinical applications.

Redirected T cells that target pancreatic adenocarcinoma antigens eliminate tumors and metastases in mice

BACKGROUND & AIMS

Pancreatic adenocarcinoma (PAC) is often diagnosed at an advanced and inoperable stage, and standard systemic treatments are generally ineffective. We investigated the effects of adoptive transfer of tumor-specific T cells that express chimeric antibody-based receptors (CAR) to mice with primary and metastatic PAC xenografts.

METHODS

Human effector T cells were genetically modified to express CAR against Her2/neu or CD24, a putative PAC stem cell antigen. The antitumor reactivity of the engineered T cells (T-bodies) was evaluated in SCID mice with different PAC xenografts. A total of 1 × 10(7) T-bodies were injected via the tail vein or directly administered to the subcutaneous tumor on 3 or 4 alternating days. Mice were then given twice-daily intraperitoneal injections of interleukin-2 for 10 days.

RESULTS

Intratumor injection of human CD24 and Her2/neu-specific T-bodies completely eliminated the tumors from most animals. Intravenous injection of T-bodies reduced tumor size and prolonged survival of mice with orthotopically transplanted tumors; more than 50% of animals appeared to be disease-free more than 2 months later. Additional systemic administration of T-bodies 8 weeks after the initial injection eliminated primary tumors, along with liver and draining lymph node metastases. A single administration of the Her2/neu-specific T-bodies prolonged the survival of mice with tumors in which most of the cells expressed the target antigen. In contrast, the CD24-specific T-bodies prolonged survival of mice in which only a subpopulation of the tumor cells expressed the antigen.

CONCLUSIONS

CAR-redirected T cells stop growth and metastasis of PAC xenografts in mice. T-bodies specific to CD24, a putative cancer stem cell antigen, were effective against PAC xenografts that had only a subset of antigen-expressing cells.

Novel anti-ErbB3 monoclonal antibodies show therapeutic efficacy in xenografted and spontaneous mouse tumors

The role of the ErbB3 receptor in signal transduction is to augment the signaling repertoire of active heterodimeric ErbB receptor complexes through activating the PI3K/AKT pathway, which in turn promotes survival and proliferation. ErbB3 has recently been proposed to be involved in acquired resistance to tyrosine kinase inhibitors (TKIs), and is therefore a promising new drug cancer target. Since ErbB3 is a kinase defective receptor, it cannot be targeted by small molecule inhibitors, whereas monoclonal antibodies may offer a viable strategy for pharmacological intervention. In this study, we have utilized DNA electroporation (DNA-EP) to generate a set of novel hybridomas directed against human ErbB3, which have been characterized for their biochemical and functional properties and selected for their ability to negatively regulate the ErbB3-mediated signaling pathway. In vitro, the anti-ErbB3 antibodies modulate the growth rate of cancer cells of different origins. In vivo they show antitumoral properties in a xenograft model of human pancreatic tumor and in the ErbB2-driven carcinogenesis genetically engineered mouse model (GEMM) for mammary tumor, the BALB/neuT. Our data confirm that downregulating the ErbB3-mediated signals with the use of anti-ErbB3 monoclonal antibodies is both feasible and relevant for therapeutic purposes and provides new opportunities for novel anti-ErbB3 combinatory strategies for cancer treatment.

HER3 overexpression is a prognostic indicator of extrahepatic cholangiocarcinoma

Members of the HER (ERBB) receptor protein tyrosine kinase family play an important role in regulating cellular division, proliferation, differentiation, and migration and have prognostic significance in a number of cancers. Here, we sought to define their role in extrahepatic cholangiocarcinoma (EHCC). HER2 and HER3 protein expression was studied in 230 EHCC cases using a tissue microarray and compared with clinicopathological variables, including the survival of EHCC patients. HER3 was predominantly localized to the cytoplasm, whereas HER2 exhibited a membranous expression pattern. Overexpression of HER2 and HER3 was observed in 6 % (13/224) and 39 % (90/230) of EHCCs, respectively. Membranous HER2 overexpression occurred more frequently in intraductal papillary neoplasms with an associated invasive carcinoma than in tubular adenocarcinomas (P = 0.02). HER3 protein was more commonly overexpressed in nodular and infiltrative than in papillary tumors (P = 0.03). HER3 overexpression was associated with decreased survival in both univariate (P = 0.01) and multivariate (P = 0.008) analyses, whereas HER2 overexpression was not associated with survival. HER2 and HER3 are overexpressed in subsets of EHCC patients. Notably, HER3 overexpression is correlated with decreased patient survival, suggesting that HER3 constitutes a prognostic factor as well as a potential candidate for targeted therapy.

Advanced HER2-positive gastric cancer: current and future targeted therapies

The prognostic value of human epidermal growth factor receptor 2 (HER2) in gastric cancer is controversial. Consensus guidelines have standardized the testing of HER2 status in gastric cancer. Overexpression of this receptor occurs in approximately 20% of gastric and gastro-esophageal junction adenocarcinomas, predominantly those of the intestinal type. Recently, trastuzumab has emerged as the first targeted drug to improve overall survival when combined with chemotherapy in advanced HER2-positive gastric cancer. Primary and secondary resistance to trastuzumab has become a major problem and new strategies to overcome this resistance are needed. A high percentage of advanced HER2-positive gastric cancer patients who progress on trastuzumab therapy are candidates for second-line therapy. New families of targeted drugs, including tyrosine kinase inhibitors (TKIs) such as lapatinib and PF-00299804, mammalian target of rapamycin (mTOR) pathway inhibitors such as everolimus, heat-shock protein 90 (HSP90) inhibitors such as AUY922, HER dimerization inhibitors such as pertuzumab, and antibody-chemotherapy conjugates such as trastuzumab-emtansine (T-DM1), could offer alternative second-line treatments when trastuzumab-based first-line therapy fails.

Akt expression and compartmentalization in prediction of clinical outcome in HER2-positive metastatic breast cancer patients treated with trastuzumab

Trastuzumab is effective in about half of HER2-positive breast cancer patients. The PI3K/Akt signalling pathway plays an important role in the process of primary and secondary resistance to anti-HER2 targeted therapy. We evaluated the relationship between expression, activation and subcellular localization of selected Akt isoforms and response to trastuzumab-based anti-HER2 targeted therapy in patients with HER2-positive metastatic breast cancer. Seventy-four women with verified HER2-positive breast cancer were treated with trastuzumab for metastatic disease. Immunohistochemistry was used to evaluate Akt1, Akt2, pAkt Thr308 and pAkt Ser473 expression. For pAkt, cytoplasmic and nuclear fractions were assessed separately. Even though Akt isoforms were expressed in the majority of tumours, activated Akt (pAkt) was present in the cytoplasm only and not in the nucleus in >20% of tumours, and there was no pAkt at all in another 7–13% of tumours. Patients whose tumours showed strong Akt2 expression and had pAkt (pAkt-Thr308 and/or pAkt-Ser473) detectable in the cytoplasm as well as nucleus (n+c), exhibited improved time to progression (TTP) and overall survival from the initiation of trastuzumab therapy (OSt). Patients with tumours with strong Akt2 and pAkt Thr308 (n+c) had superior TTP (17.0 vs. 7.6 months, P=0.024; HR 0.52) and OSt (51.8 vs. 16.8 months, P=0.0009; HR 0.34) compared to other tumours. Similar results were found for strong Akt2 and pAkt Ser473 (n+c): TTP 13.1 vs. 7.2 months (P=0.085, HR 0.62) and OSt 50.8 vs. 17.0 months (P=0.009; HR 0.45). This study is the first to prove the significance of Akt kinase isoform, activity and compartmentalization for the prediction of response to trastuzumab-based therapy in patients with HER2-positive metastatic breast cancer.

Correlation of HER2, p95HER2 and HER3 expression and treatment outcome of lapatinib plus capecitabine in her2-positive metastatic breast cancer

BACKGROUND

Lapatinib plus capecitabine is an effective treatment option for trastuzumab-refractory HER2-positive metastatic breast cancer. We have investigated the correlation between quantitative measures of HER2, p95HER2, and HER3 and treatment outcomes using lapatinib and capecitabine.

METHODS

Total HER2 (H2T), p95HER2 (p95), and total HER3 (H3T) expression were quantified in formalin-fixed paraffin-embedded samples using the VeraTag assays. Patients received lapatinib and capecitabine treatment following trastuzumab failure according to the Lapatinib Expanded Access Program. The association between the protein expression levels and clinical outcomes was analyzed.

RESULTS

A total of 52 patients were evaluable. H2T level was significantly higher in responders (median 93.49 in partial response, 47.66 in stable disease, and 17.27 in progressive disease; p = 0.020). Longer time-to-progression (TTP) was observed in patients with high H2T [p = 0.018, median 5.2 months in high (>14.95) vs. 1.8 in low (<14.95)] and high H3T [p = 0.017, median 5.0 months in high (>0.605) vs. 2.2 in low (<0.605)]. Patients having both high H2T and high H3T had significantly longer TTP [adjusted hazard ratio (HR) 0.38 (95% CI 0.20-0.73), p = 0.004] and overall survival [adjusted HR 0.46 (95% CI 0.24-0.89), p = 0.020]. No significant association between p95 and response or survival was observed.

CONCLUSIONS

These data suggest a correlation between high HER2 and high HER3 expression and treatment outcome, while no significant difference was observed between clinical outcome and p95 expression level in this cohort of HER2-positive, trastuzumab-refractory metastatic breast cancer patients treated with lapatinib and capecitabine.

Prognostic biomarkers in ovarian cancer

Epithelial ovarian cancer (EOC) remains the most lethal gynecological malignancy despite several decades of progress in diagnosis and treatment. Taking advantage of the robust development of discovery and utility of prognostic biomarkers, clinicians and researchers are developing personalized and targeted treatment strategies. This review encompasses recently discovered biomarkers of ovarian cancer, the utility of published prognostic biomarkers for EOC (especially biomarkers related to angiogenesis and key signaling pathways), and their integration into clinical practice.

Polyclonal HER2-specific antibodies induced by vaccination mediate receptor internalization and degradation in tumor cells

Introduction

Sustained HER2 signaling at the cell surface is an oncogenic mechanism in a significant proportion of breast cancers. While clinically effective therapies targeting HER2 such as mAbs and tyrosine kinase inhibitors exist, tumors overexpressing HER2 eventually progress despite treatment. Thus, abrogation of persistent HER2 expression at the plasma membrane to synergize with current approaches may represent a novel therapeutic strategy.

Methods

We generated polyclonal anti-HER2 antibodies (HER2-VIA) by vaccinating mice with an adenovirus expressing human HER2, and assessed their signaling effects in vitro and anti-tumor effects in a xenograft model. In addition, we studied the signaling effects of human HER2-specific antibodies induced by vaccinating breast cancer patients with a HER2 protein vaccine.

Results

HER2-VIA bound HER2 at the plasma membrane, initially activating the downstream kinases extracellular signal-regulated protein kinase 1/2 and Akt, but subsequently inducing receptor internalization in clathrin-coated pits in a HER2 kinase-independent manner, followed by ubiquitination and degradation of HER2 into a 130 kDa fragment phosphorylated at tyrosine residues 1,221/1,222 and 1,248. Following vaccination of breast cancer patients with the HER2 protein vaccine, HER2-specific antibodies were detectable and these antibodies bound to cell surface-expressed HER2 and inhibited HER2 signaling through blocking tyrosine 877 phosphorylation of HER2. In contrast to the murine antibodies, human anti-HER2 antibodies induced by protein vaccination did not mediate receptor internalization and degradation.

Conclusion

These data provide new insight into HER2 trafficking at the plasma membrane and the changes induced by polyclonal HER2-specific antibodies. The reduction of HER2 membrane expression and HER2 signaling by polyclonal antibodies induced by adenoviral HER2 vaccines supports human clinical trials with this strategy for those breast cancer patients with HER2 therapy-resistant disease.

Uncoupling of PI3K from ErbB3 impairs mammary gland development but does not impact on ErbB2-induced mammary tumorigenesis

The formation of ErbB2/ErbB3 heterodimers plays a critical role in ErbB2-mediated signaling in both normal mammary development and mammary tumor progression. Through 7 phosphoinositide 3-kinase (PI3K) phosphotyrosine-binding sites, ErbB3 is able to recruit PI3K and initiate the PI3K/AKT signaling pathway. To directly explore the importance of the ErbB3/PI3K pathway in mammary development and tumorigenesis, we generated a mouse model that carries a mutant ErbB3 allele lacking the seven known PI3K-binding sites (ErbB3(Δ85)). Mice homozygous for the ErbB3(Δ85) allele exhibited an initial early growth defect and a dramatic impairment of mammary epithelial outgrowth. Although homozygous adult mice eventually recovered from the growth defect, their mammary glands continued to manifest the mammary outgrowth and lactation defects throughout their adult life. Interestingly, despite the presence of a profound mammary gland defect, all of the female ErbB3Δ85 mice developed metastatic ErbB2-induced mammary tumors secondary to mammary epithelial expression of an activated ErbB2 oncogene capable of compensatory PI3K signaling from both EGF receptor and ErbB2. Our findings therefore indicate that, although ErbB3-associated PI3K activity is critical for mammary development, it is dispensable for ErbB2-induced mammary tumor progression.

MEK inhibition leads to PI3K/AKT activation by relieving a negative feedback on ERBB receptors

The phosphoinositide 3-kinase (PI3K)/AKT and RAF/MEK/ERK signaling pathways are activated in a wide range of human cancers. In many cases, concomitant inhibition of both pathways is necessary to block proliferation and induce cell death and tumor shrinkage. Several feedback systems have been described in which inhibition of one intracellular pathway leads to activation of a parallel signaling pathway, thereby decreasing the effectiveness of single-agent targeted therapies. In this study, we describe a feedback mechanism in which MEK inhibition leads to activation of PI3K/AKT signaling in EGFR and HER2-driven cancers. We found that MEK inhibitor-induced activation of PI3K/AKT resulted from hyperactivation of ERBB3 as a result of the loss of an inhibitory threonine phosphorylation in the conserved juxtamembrane domains of EGFR and HER2. Mutation of this amino acid led to increased ERBB receptor activation and upregulation of the ERBB3/PI3K/AKT signaling pathway, which was no longer responsive to MEK inhibition. Taken together, these results elucidate an important, dominant feedback network regulating central oncogenic pathways in human cancer.

Discovery of HDAC-Inhibiting Multi-Target Inhibitors

Several HDAC-inhibiting multiple-target inhibitors have been reported. In this chapter, the current progress in investigating HDAC-inhibiting multi-target inhibitors is briefly reviewed, with a focus on the first and only clinical candidate CUDC-101 as the case study example. CUDC-101 is a novel small molecule potently inhibiting activities of the EGFR and HER2 kinases and HDAC enzymes with IC50 values of 2.4, 15.7, and 4.4nM, respectively. CUDC-101's rational design and synthesis, superior in vitro potency, broad anti-proliferative and pro-apoptotic activities in cultured tumor cells including RTK inhibitor-resistant cell lines, effective network disruption in survival signaling pathways, high efficacy in in vivo xenograft animal models, favorable safety profile, and preliminary evidence of anti-tumor activity in phase I trials are presented in this chapter. This case study provides proof-of-principle that a single molecule with multiple targeted specificities can improve the effectiveness of current anticancer therapeutics preclinically.

The interplay of HER2/HER3/PI3K and EGFR/HER2/PLC-γ1 signalling in breast cancer cell migration and dissemination

HER2 signalling by heterodimerisation with EGFR and HER3 in breast cancer is associated with worst outcome of the afflicted patients, which is attributed not only to the aggressiveness of such tumours but also to therapy resistance. Thus, in the present study we investigated the role of EGFR, HER2 and HER3 lateral signalling in cell migration by applying the MDA-MB-468-HER2 (MDA-HER2) breast cancer cell line, representing a valid model system. Knockdown of HER3 expression by siRNA resulted in decreased phosphorylated AKT (pAKT) levels, abrogated epidermal growth factor (EGF)-mediated PLC-γ1 activation and a diminished EGF-induced migratory activity, depicting the interplay of EGF receptor (EGFR)/HER2/PLC-γ1 and HER2/HER3/PI3K signalling in mediating the migration of EGFR/HER2/HER3-expressing breast cancer cells. Since therapy failure usually arises from metastatic cells, we further investigated whether HER3 signalling was active in established breast cancer disseminated tumour cell (DTC) lines as well as in primary DTCs derived from breast cancer patients. EGF treatment of DTC lines resulted solely in increased pAKT S473 levels, whereas in MDA-HER2 cells both pAKT S473 and pAKT T308 levels were increased upon EGF stimulation. Moreover, despite active HER3 molecules, as indicated by pTyr1222 staining, about 90% of analysed breast cancer patient DTCs exhibited very low or even no detectable pAKT S473 levels, suggesting that these cells might have fallen into dormancy. In summary, our data indicate the important role in EGFR, HER2 and HER3 lateral signalling in breast cancer cell migration. Moreover, our data further show that primary tumour cells and DTCs can vary in their HER activation status, which is important to know in the context of cancer therapy.

New developments in mammalian target of rapamycin inhibitors for the treatment of sarcoma

Although sarcomas account for a small portion of solid malignancies, currently, there are few treatment options for sarcomas, particularly for advanced disease. The mammalian target of rapamycin (mTOR), a serine-threonine protein kinase in the phosphatidylinositol 3-kinase/serine/threonine protein kinase Akt signaling pathway, has an important role in the regulation of protein synthesis, cell proliferation, angiogenesis, and metabolism. Alterations of the mTOR signaling pathway are common in malignancies, including several types of sarcoma. Therefore, mTOR is a potentially important therapeutic target in these diseases. Rapamycin and its analogs (rapalogs) are effective anticancer agents in a broad range of preclinical models. Clinical trials with these agents alone and in combination with other anticancer agents, including chemotherapy and targeted therapies, have demonstrated potential clinical benefit in several types of sarcoma. The evidence from both preclinical and clinical studies supports further study of mTOR-targeting rapalogs in the treatment of various subtypes of sarcoma.

A water-based mechanism of specificity and resistance for lapatinib with ErbB family kinases

The dual kinase inhibitor lapatinib has a high affinity for EGFR and HER2 but a weak affinity for ErbB4, although the factors driving specificity for these highly homologous members of the ErbB family of receptor tyrosine kinases are not well understood. In this report, homology modeling, molecular dynamics simulations, and free energy calculations are employed with the goal of uncovering the energetic and structural molecular basis of lapatinib specificity and resistance. The results reveal a distinct network of three binding site water molecules that yield strikingly similar hydration patterns for EGFR and HER2 in contrast to that of ErbB4, which shows a different pattern with a reduced occupancy at one of the positions. The primary cause was traced to a single amino acid change in the binding site (EGFR position 775), involving a swap from C or S (EGFR and HER2) to V (ErbB4), for which the side chain is bulkier, is hydrophobic, and lacks the ability to form a H-bond with water. Notably, excellent quantitative agreement with experimental activities is obtained across the series (EGFR > HER2 > ErbB4) when key waters are included in the calculations. Quantitatively, Coulombic interactions and H-bond counts between network waters and species involved in the network are less favorable in ErbB4 by ~40% relative to those in EGFR or HER2. Additional simulations with clinically relevant EGFR (C775F, T854A, and T790M) and HER2 (T790I) mutants demonstrate that resistance can also be understood in terms of changes that occur in the binding site water network. Overall, the results of this study have yielded a physically reasonable water-based mechanism for describing lapatinib specificity and resistance.

Antibody validation by combining immunohistochemistry and protein extraction from formalin-fixed paraffin-embedded tissues

AIMS

  Personalized cancer treatment strategies depend on comprehensive and detailed characterization of individual human malignancies. Clinical pathology, particularly immunohistochemical evaluation of biomarkers in tissues, is considered to be the approved standard for diagnostic and therapeutic decisions, having a direct influence on patient management and therapy. Although antibody-based approaches are established and integrated successfully into both clinical and research applications, for personalized treatment regimens new demands have been placed on the quality, reproducibility and accuracy of antibody-based assays. To ensure the accuracy of specific antigen detection in immunohistochemistry, we introduce a novel approach for antibody validation.

METHODS AND RESULTS

  In a tandem approach we used the same archival tissue of interest for antibody validation by combining extraction of immunoreactive proteins from formalin-fixed, paraffin-embedded tissue with Western blot analysis and immunohistochemistry. This procedure allows for specification of the antigen detected and for localization of the protein in the tissue. Of the 32 antibodies tested used in research and routine diagnostics, 19 showed reliable specificity in both assays.

CONCLUSION

  This study emphasizes the advantage of combining suitable methods to ensure reproducibility and specific antigen detection. Based on our results, we propose a novel step-by-step strategy to validate antibody specificity and reduce variability of immunohistochemical results.

Pertuzumab plus trastuzumab plus docetaxel for metastatic breast cancer

BACKGROUND

The anti-human epidermal growth factor receptor 2 (HER2) humanized monoclonal antibody trastuzumab improves the outcome in patients with HER2-positive metastatic breast cancer. However, most cases of advanced disease eventually progress. Pertuzumab, an anti-HER2 humanized monoclonal antibody that inhibits receptor dimerization, has a mechanism of action that is complementary to that of trastuzumab, and combination therapy with the two antibodies has shown promising activity and an acceptable safety profile in phase 2 studies involving patients with HER2-positive breast cancer.

METHODS

We randomly assigned 808 patients with HER2-positive metastatic breast cancer to receive placebo plus trastuzumab plus docetaxel (control group) or pertuzumab plus trastuzumab plus docetaxel (pertuzumab group) as first-line treatment until the time of disease progression or the development of toxic effects that could not be effectively managed. The primary end point was independently assessed progression-free survival. Secondary end points included overall survival, progression-free survival as assessed by the investigator, the objective response rate, and safety.

RESULTS

The median progression-free survival was 12.4 months in the control group, as compared with 18.5 months in the pertuzumab group (hazard ratio for progression or death, 0.62; 95% confidence interval, 0.51 to 0.75; P<0.001). The interim analysis of overall survival showed a strong trend in favor of pertuzumab plus trastuzumab plus docetaxel. The safety profile was generally similar in the two groups, with no increase in left ventricular systolic dysfunction; the rates of febrile neutropenia and diarrhea of grade 3 or above were higher in the pertuzumab group than in the control group.

CONCLUSIONS

The combination of pertuzumab plus trastuzumab plus docetaxel, as compared with placebo plus trastuzumab plus docetaxel, when used as first-line treatment for HER2-positive metastatic breast cancer, significantly prolonged progression-free survival, with no increase in cardiac toxic effects. (Funded by F. Hoffmann-La Roche/Genentech; ClinicalTrials.gov number, NCT00567190.).

Managing stomatitis in patients treated with Mammalian target of rapamycin inhibitors

Mammalian target of rapamycin (mTOR) inhibitors are a class of targeted cancer therapeutic agents with clinical benefit for multiple tumor types. Oral ulcerations are a common side effect of mTOR inhibitors; however, the clinical findings resemble aphthous stomatitis rather than the mucositis seen with chemotherapy. Consequently, the appearance of aphthous-like oral ulcerations has been referred to as mTOR inhibitor-associated stomatitis (mIAS). The severity of mIAS can be minimized by following common preventive steps and initiating treatment at the first sign of mouth discomfort, thereby reducing the likelihood of treatment discontinuation. mIAS can be managed through prophylactic measures, such as patient education in oral hygiene and avoidance of triggers. Patients who develop mIAS may be treated topically using rinses or other local therapies, including corticosteroids. In severe cases, dose modifications may be required. Oncology nurses have an important role in the management of patients with cancer and are well positioned to offer strategies for minimizing the occurrence and impact of mIAS.