The ErbB2 signaling network as a target for breast cancer therapy

ERBB2 Targeting Reveals a Significant Suppression of Tumorigenesis in Murine Endometrial Cancer with Pten Mutation

Endometrial cancer is the most common gynecologic malignancy. PTEN is a negative regulator of PI3K signaling and is deficient in > 50% of primary human endometrial cancer. Amplification of ERBB2 promotes tumorigenesis and pathogenesis of several human cancers. However, the effect of ERBB2 targeting has not been studied in endometrial cancer with PTEN mutations. The murine model Pgrcre/+Erbb2f/fPtenf/f (Erbb2d/d Ptend/d) was developed to evaluate the effect of ERBB2 targeted therapy in endometrial cancer with PTEN deficiency. Histopathological and molecular analysis was performed for Ptend/d and Erbb2d/dPtend/d mice. Histopathological analysis revealed that Erbb2d/dPtend/d mice significantly reduced development and progression of endometrial cancer compared to Ptend/d mice. Furthermore, percentage of proliferative cells in Erbb2d/dPtend/d mice revealed anti-tumorigenic effect of Erbb2 ablation compared to Ptend/d mice. Our results demonstrate that Erbb2 ablation reveals a significant suppression of tumorigenesis on endometrial cancer of Ptend/d mice. Our results suggest that Erbb2 functions as an oncogene in endometrial cancer of Ptend/d mice implying that Erbb2 targeting can be used as an effective therapeutic approach for treatment of endometrial cancer with PTEN deficiency to hinder cancer development.

Gastrointestinal injury induced by immunomodulators: A review article

An increasing number of immunomodulators, either anti-inflammatory or immunity-enhancing, have brought about a revolutionary effect in the management of a variety of autoimmune disorders and malignancies. However, their ability to cause gastrointestinal (GI) injury and induce GI symptoms has been increasingly and unexpectedly recognized. GI injury associated with immunomodulators may demonstrate various histologic and endoscopic patterns. Optimal diagnosis and treatment require a multidisciplinary approach. This review aims to provide an overview of the literature on its pathogenesis, the clinical, endoscopic, and histologic features, and suggested approaches to manage these newly recognized immunomodulator-induced GI adverse effects (AEs). We also reviewed current biomarkers predictive of GI toxicity and potential risk factors to identify susceptible patients. In addition, these immune-mediated AEs were compared with inflammatory bowel disease, a well-documented form of inflammation-driven GI injury. We hope this review will raise awareness and vigilance among clinicians of these entities to increase early diagnosis and rapid referral to specialist care.

6-lncRNA Assessment Model for Monitoring and Prognosis of HER2-Positive Breast Cancer: Based on Transcriptome Data

Background: In view of the high malignancy and poor prognosis of human epidermal growth factor receptor 2 (HER2)-positive breast cancer, we analyzed the RNA expression profiles of HER2-positive breast cancer samples to identify the new prognostic biomarkers. Methods: The linear fitting method was used to identify the differentially expressed RNAs from the HER2-positive breast cancer RNA expression profiles in the Cancer Genome Atlas (TCGA). Then, a series of methods including univariate Cox, Kaplan-Meier, and random forests, were used to identify the core long non-coding RNAs (lncRNAs) with stable prognostic value for HER2-positive breast cancer. A clinical feature analysis was performed, and a competing endogenous RNA network was constructed to explore the role of these core lncRNAs in HER2-positive breast cancer. In addition, a functional analysis of differentially expressed messenger RNAs in HER-2 positive breast cancer also provided us with some enlightening insights. Results: The high expression of four core lncRNAs (AC010595.1, AC046168.1, AC069277.1, and AP000904.1) was associated with worse overall survival, while the low expression of LINC00528 and MIR762HG was associated with worse overall survival. The 6-lncRNA model has an especially good predictive power for overall survival (p < 0.0001) and 3-year survival (the area under the curve = 0.980) in HER2-positive breast cancer patients. Conclusion: This study provides a new efficient prognostic model and biomarkers of HER2-positive breast cancer. Meanwhile, it also provides a new perspective for elucidating the molecular mechanisms underlying HER2-positive breast cancer.

Structural and dynamic characterization of the C-terminal tail of ErbB2: Disordered but not random

ErbB2 (or HER2) is a receptor tyrosine kinase overexpressed in some breast cancers and associated with poor prognosis. Treatments targeting the receptor extracellular and kinase domains have greatly improved disease outcome in the last 20 years. In parallel, the structures of these domains have been described, enabling better mechanistic understanding of the receptor function and targeted inhibition. However, the ErbB2 disordered C-terminal cytoplasmic tail (CtErbB2) remains very poorly characterized in terms of structure, dynamics, and detailed functional mechanism. Yet, it is where signal transduction is triggered via phosphorylation of tyrosine residues and carried out via interaction with adaptor proteins. Here, we report the first description, to our knowledge, of the ErbB2 disordered tail at atomic resolution using NMR, complemented by small-angle x-ray scattering. We show that although no part of CtErbB2 has any fully populated secondary or tertiary structure, it contains several transient α-helices and numerous transient polyproline II helices, populated up to 20 and 40%, respectively, and low but significant compaction. The presence of some structural elements suggests, along the lines of the results obtained for EGFR (ErbB1), that they may have a functional role in ErbB2's autoregulation processes. In addition, the transient formation of polyproline II helices is compliant with previously suggested interactions with SH3 domains. All in all, our in-depth structural study opens perspectives in the mechanistic understanding of ErbB2.

A comprehensive review of tumor proliferative and suppressive role of semaphorins and therapeutic approaches

Semaphorins have been traditionally known as axon guidance proteins that negatively regulate axonal growth. However, in the past couple of decades, their versatile role in so many other biological processes has come to prominence as well. One such example is their role in cancer. In this review article, the focus was on the tumor proliferative and tumor suppressive role of all 20 semaphorin family members under the 7 semaphorin classes found in vertebrates and invertebrates as well as the ongoing and emerging therapeutic approaches to combat semaphorin-mediated cancers. Except sema6C, 19 of the 20 non-viral semaphorin family members have been discovered to be associated with cancer in one way or another. Eleven semaphorin family members have been discovered to be tumor proliferative and 8 to be tumor suppressive. Six therapeutic avenues and their safety profiles have been discussed which are currently at use or at the various stages of development. Finally, perspectives on which approach is the best for treating cancers associated with semaphorins have been given.

Structure-based Identification of Endocrine Disrupting Pesticides Targeting Breast Cancer Proteins

Endocrine disrupting pesticides (EDPs) are exogenous compounds that disrupt endocrine activity. Human exposure to EDPs can occur through occupational contact, and through the consumption of food, milk and water with trace amounts of these pollutants. Several EDPs are epidemiologically linked to breast cancer or are considered as possible carcinogens. However, current evidence is not fully conclusive and their mechanisms of action remain unknown. Thus, the potential interactions between 262 EDPs and 189 proteins associated with breast cancer were evaluated by using a virtual high-throughput screening approach, with AutoDock Vina 1.1.1. The molecular coordinates were previously downloaded from Protein Data Bank and EDCs DataBank, and used for preparation and optimization in Sybyl X-2.0. The best affinity score (-11.0 kcal/mol) was obtained for flucythrinate with the nuclear receptor for vitamin D (VDR). This synthetic pyrethroid, along with other EDPs, such as fluvalinate, bifenthrin, cyhalothrin and cypermethrin, are proposed as multi-target ligands of several proteins related to breast cancer. In addition, the validation of our protocol showed a good accuracy in terms of binding pose prediction and affinity estimation. This study provides a guide to prioritize EDPs for which further in vitro and in vivo analysis could be done to evaluate the risk and possible mechanisms of action of these contaminants and their potential association with breast cancer.

Hormonal treatment combined with targeted therapies in endocrine-responsive and HER2-positive metastatic breast cancer

Approximately 50% of HER2 positive breast cancer cases are also estrogen receptor (ER) positive. Data supports a role for close cross-talk between the ER and HER2 signaling pathways as an important contributor to the development of de novo or acquired resistance to hormone therapies. Therefore a strategy that simultaneously blocks both signaling pathways is a reasonable approach to prevent or overcome either endocrine or anti-HER2 therapy resistance. Moreover, preclinical data support the idea that PI3K inhibitors and CDK4/6 could be an attractive target that functions downstream of both ER and HER2 pathways. We conducted a literature review of the results of phase II and III studies testing targeted therapies in metastatic breast cancer with HER2-positive and hormonal-receptor-positive disease. The analyses included efficacy and toxicity data from earlier studies with a single anti-HER2 drug combined with hormonal therapy up to more recent studies testing new molecules targeting these signaling pathways. The aims of this review are to summarize current knowledge and to discuss research development including the possibility to spare chemotherapy in this subgroup of HER2-positive breast cancer patients.

Cell-Free Co-Translational Approaches for Producing Mammalian Receptors: Expanding the Cell-Free Expression Toolbox Using Nanolipoproteins

Membranes proteins make up more than 60% of current drug targets and account for approximately 30% or more of the cellular proteome. Access to this important class of proteins has been difficult due to their inherent insolubility and tendency to aggregate in aqueous solutions. Understanding membrane protein structure and function demands novel means of membrane protein production that preserve both their native conformational state as well as function. Over the last decade, cell-free expression systems have emerged as an important complement to cell-based expression of membrane proteins due to their simple and customizable experimental parameters. One approach to overcome the solubility and stability limitations of purified membrane proteins is to support them in stable, native-like states within nanolipoprotein particles (NLPs), aka nanodiscs. This has become common practice to facilitate biochemical and biophysical characterization of proteins of interest. NLP technology can be easily coupled with cell-free systems to achieve functional membrane protein production for this purpose. Our approach involves utilizing cell-free expression systems in the presence of NLPs or using co-translation techniques to perform one-pot expression and self-assembly of membrane protein/NLP complexes. We describe how cell-free reactions can be modified to render control over nanoparticle size and monodispersity in support of membrane protein production. These modifications have been exploited to facilitate co-expression of full-length functional membrane proteins such as G-protein-coupled receptors (GPCRs) and receptor tyrosine kinases (RTKs). In particular, we summarize the state of the art in NLP-assisted cell-free coexpression of these important classes of membrane proteins as well as evaluate the advances in and prospects for this technology that will drive drug discovery against these targets. We conclude with a prospective on the use of NLPs to produce as well as deliver functional mammalian membrane-bound proteins for a range of applications.

1H, 13C and 15N assignments of the C-terminal intrinsically disordered cytosolic fragment of the receptor tyrosine kinase ErbB2

ErbB2 (or HER2) is a receptor tyrosine kinase that is involved in signaling pathways controlling cell division, motility and apoptosis. Though important in development and cell growth homeostasis, this protein, when overexpressed, participates in triggering aggressive HER2+ breast cancers. It is composed of an extracellular part and a transmembrane domain, both important for activation by dimerization, and a cytosolic tyrosine kinase, which activates its intrinsically disordered C-terminal end (CtErbB2). Little is known about this C-terminal part of 268 residues, despite its crucial role in interacting with adaptor proteins involved in signaling. Understanding its structural and dynamic characteristics could eventually lead to the design of new interaction inhibitors, and treatments complementary to those already targeting other parts of ErbB2. Here we report backbone and side-chain assignment of CtErbB2, which, together with structural predictions, confirms its intrinsically disordered nature.

An integrated approach to infer cross-talks between intracellular protein transport and signaling pathways

Background

The endomembrane system, known as secretory pathway, is responsible for the synthesis and transport of protein molecules in cells. Therefore, genes involved in the secretory pathway are essential for the cellular development and function. Recent scientific investigations show that ER and Golgi apparatus may provide a convenient drug target for cancer therapy. On the other hand, it is known that abundantly expressed genes in different cellular organelles share interconnected pathways and co-regulate each other activities. The cross-talks among these genes play an important role in signaling pathways, associated to the regulation of intracellular protein transport.

Results

In the present study, we device an integrated approach to understand these complex interactions. We analyze gene perturbation expression profiles, reconstruct a directed gene interaction network and decipher the regulatory interactions among genes involved in protein transport signaling. In particular, we focus on expression signatures of genes involved in the secretory pathway of MCF7 breast cancer cell line. Furthermore, network biology analysis delineates these gene-centric cross-talks at the level of specific modules/sub-networks, corresponding to different signaling pathways.

Conclusions

We elucidate the regulatory connections between genes constituting signaling pathways such as PI3K-Akt, Ras, Rap1, calcium, JAK-STAT, EFGR and FGFR signaling. Interestingly, we determine some key regulatory cross-talks between signaling pathways (PI3K-Akt signaling and Ras signaling pathway) and intracellular protein transport.

Electronic supplementary material

The online version of this article (10.1186/s12859-018-2036-2) contains supplementary material, which is available to authorized users.

Controlling Directed Protein Interaction Networks in Cancer

Control theory is a well-established approach in network science, with applications in bio-medicine and cancer research. We build on recent results for structural controllability of directed networks, which identifies a set of driver nodes able to control an a-priori defined part of the network. We develop a novel and efficient approach for the (targeted) structural controllability of cancer networks and demonstrate it for the analysis of breast, pancreatic, and ovarian cancer. We build in each case a protein-protein interaction network and focus on the survivability-essential proteins specific to each cancer type. We show that these essential proteins are efficiently controllable from a relatively small computable set of driver nodes. Moreover, we adjust the method to find the driver nodes among FDA-approved drug-target nodes. We find that, while many of the drugs acting on the driver nodes are part of known cancer therapies, some of them are not used for the cancer types analyzed here; some drug-target driver nodes identified by our algorithms are not known to be used in any cancer therapy. Overall we show that a better understanding of the control dynamics of cancer through computational modelling can pave the way for new efficient therapeutic approaches and personalized medicine.

Safety and efficacy evaluation of pertuzumab in patients with solid tumors

BACKGROUND

The development of targeted therapies benefits patients with certain markers in the treatment of breast cancer. Pertuzumab is a novel humanized monoclonal antibody that blocks human epidermal growth factor receptor 2 (HER2) dimerization. The Food and Drug Administration has approved pertuzumab in combination with trastuzumab and docetaxel for the treatment of patients with HER2-positive metastatic breast cancer.

METHODS

To assess the safety and efficacy profile of pertuzumab, we searched PubMed and Embase (articles from January 1966 to January 2015) using the keyword "pertuzumab".

RESULTS

Fourteen eligible studies were included in our final analysis. From the results of our analysis, diarrhea (56.9%, 95% confidence interval [CI] 49.6%-63.9%), nausea (34.0%, 95% CI 27.7%-40.8%), and rash (25.6%, 95% CI 20.8%-31.0%) were the most common adverse effects in pertuzumab alone and pertuzumab-based therapies. Based on randomized controlled clinical trials, diarrhea (odds ratio [OR] 2.310, 95% CI 1.818-2.936), rash (OR 1.848, 95% CI 1.094-3.122), and febrile neutropenia (OR 1.672, 95% CI 1.130-2.474) were of statistical significance, which meant that pertuzumab played a prominent role in the incidence of diarrhea. Meanwhile, pertuzumab showed its effective role in cancer control and lifetime prolongation.

CONCLUSION

In conclusion, considering that the common adverse effects for pertuzumab are gastrointestinal and skin toxicities, which are easier to handle than other toxicities, pertuzumab is a safe and effective drug for patients with solid tumors.

Neoadjuvant therapy for early-stage breast cancer: the clinical utility of pertuzumab

Approximately 20% of breast cancer patients harbor tumors that overexpress human epidermal growth factor receptor 2 (HER2; also known as ErbB2), a receptor tyrosine kinase that belongs to the epidermal growth factor receptor family of receptor tyrosine kinases. HER2 amplification and hyperactivation drive the growth and survival of breast cancers through the aberrant activation of proto-oncogenic signaling systems, particularly the Ras/MAP kinase and PI3K/AKT pathways. Although HER2-positive (HER2(+)) breast cancer was originally considered to be a highly aggressive form of the disease, the clinical landscape of HER2(+) breast cancers has literally been transformed by the approval of anti-HER2 agents for adjuvant and neoadjuvant settings. Indeed, pertuzumab is a novel monoclonal antibody that functions as an anti-HER2 agent by targeting the extracellular dimerization domain of the HER2 receptor; it is also the first drug to receive an accelerated approval by the US Food and Drug Administration for use in neoadjuvant settings in early-stage HER2(+) breast cancer. Here, we review the molecular and cellular factors that contribute to the pathophysiology of HER2 in breast cancer, as well as summarize the landmark preclinical and clinical findings underlying the approval and use of pertuzumab in the neoadjuvant setting. Finally, the molecular mechanisms operant in mediating resistance to anti-HER2 agents, and perhaps to pertuzumab as well, will be discussed, as will the anticipated clinical impact and future directions of pertuzumab in breast cancer patients.

Computational polypharmacology analysis of the heat shock protein 90 interactome

The design of a single drug molecule that is able to simultaneously and specifically interact with multiple biological targets is gaining major consideration in drug discovery. However, the rational design of drugs with a desired polypharmacology profile is still a challenging task, especially when these targets are distantly related or unrelated. In this work, we present a computational approach aimed at the identification of suitable target combinations for multitarget drug design within an ensemble of biologically relevant proteins. The target selection relies on the analysis of activity annotations present in molecular databases and on ligand-based virtual screening. A few target combinations were also inspected with structure-based methods to demonstrate that the identified dual-activity compounds are able to bind target combinations characterized by remote binding site similarities. Our approach was applied to the heat shock protein 90 (Hsp90) interactome, which contains several targets of key importance in cancer. Promising target combinations were identified, providing a basis for the computational design of compounds with dual activity. The approach may be used on any ensemble of proteins of interest for which known inhibitors are available.

Loss of periostin/OSF-2 in ErbB2/Neu-driven tumors results in androgen receptor-positive molecular apocrine-like tumors with reduced Notch1 activity

INTRODUCTION

Periostin (Postn) is a secreted cell adhesion protein that activates signaling pathways to promote cancer cell survival, angiogenesis, invasion, and metastasis. Interestingly, Postn is frequently overexpressed in numerous human cancers, including breast, lung, colon, pancreatic, and ovarian cancer.

METHODS

Using transgenic mice expressing the Neu oncogene in the mammary epithelium crossed into Postn-deficient animals, we have assessed the effect of Postn gene deletion on Neu-driven mammary tumorigenesis.

RESULTS

Although Postn is exclusively expressed in the stromal fibroblasts of the mammary gland, Postn deletion does not affect mammary gland outgrowth during development or pregnancy. Furthermore, we find that loss of Postn in the mammary epithelium does not alter breast tumor initiation or growth in mouse mammary tumor virus (MMTV)-Neu expressing mice but results in an apocrine-like tumor phenotype. Surprisingly, we find that tumors derived from Postn-null animals express low levels of Notch protein and Hey1 mRNA but increased expression of androgen receptor (AR) and AR target genes. We show that tumor cells derived from wild-type animals do not proliferate when transplanted in a Postn-null environment but that this growth defect is rescued by the overexpression of active Notch or the AR target gene prolactin-induced protein (PIP/GCDFP-15).

CONCLUSIONS

Together our data suggest that loss of Postn in an ErbB2/Neu/HER2 overexpression model results in apocrine-like tumors that activate an AR-dependent pathway. This may have important implications for the treatment of breast cancers involving the therapeutic targeting of periostin or Notch signaling.

Purification and immunodetection of the complete recombinant HER-2[neu] receptor produced in yeast

For the first time, the full length recombinant HER-2[neu] receptor has been produced in a yeast (Arxula adeninivorans). It is one of the most studied membrane receptors in oncology and is involved in aggressive tumor formation. A yeast integration rDNA cassette containing the human gene coding for the HER-2[neu] protein was constructed and a screening procedure was performed to select the most productive transformant. Different detergents were tested for efficient solubilization of the membrane bound protein, with CHAPS giving the best results. To increase the yield of the recombinant protein from HER-2[neu] producing A. adeninivorans, optimal culture parameters were established for cultivation in bioreactor. The recombinant protein was subsequently assayed using ELISA and SPR immunoassays systems with antibodies raised against two different epitopes of the human receptor. In both cases, elution fractions containing the recombinant HER-2[neu] receptor successfully reacted with the immunoassays with limits of quantification below 100ngml(-1). These results demonstrate that the full length recombinant HER-2[neu] reported here has the potential to be a new standard for the detection of HER-2 type cancer.

[Pertuzumab (Perjeta®) approval in HER2-positive metastatic breast cancers]

Fifteen to 20% of breast cancers display HER2 amplification. Many therapeutic successes have been obtained for this subtype in the last decade since trastuzumab approval for metastatic and localized diseases. Pertuzumab, a new anti-HER2 antibody, has been approved in 2013 by the European Medicine Agency. This drug can be used in combination with trastuzumab and docetaxel for the first line treatment of metastatic or locally recurrent non resecable HER2-positive breast cancers not previously treated by chemotherapy or HER2-inhibitors in the metastatic setting. This approval has been done after the CLEOPATRA trial results. This was a randomized, double-blind, multicentre, phase III trial evaluating the standard treatment (trastuzumab plus docetaxel) associated to pertuzumab or placebo. The authors have reported a statistically significant and clinically relevant benefit for the pertuzumab-based treatment. Median progression-free survival was 18.4 for the pertuzumab arm versus 12.5 months for the control group (p<0.001). They also observed benefits concerning the secondary endpoints: overall response rate and overall survival. Patients receiving pertuzumab presented more frequent diarrhea and febrile neutropenia but no increase in cardiac events. This drug has already been evaluated in the neoadjuvant setting with a FDA approval recently obtained. Its use in the adjuvant setting is under evaluation.

Identification of a Src kinase SH3 binding site in the C-terminal domain of the human ErbB2 receptor tyrosine kinase

Overexpression of the ErbB2 receptor tyrosine kinase is associated with most aggressive tumors in breast cancer patients and is thus one of the main investigated therapeutic targets. Human ErbB2 C-terminal domain is an unstructured anchor that recruits specific adaptors for signaling cascades resulting in cell growth, differentiation and migration. Herein, we report the presence of a SH3 binding motif in the proline rich unfolded ErbB2 C-terminal region. NMR analysis of this motif supports a PPII helix conformation and the binding to Fyn-SH3 domain. The interaction of a kinase of the Src family with ErbB2 C-terminal domain could contribute to synergistic intracellular signaling and enhanced oncogenesis.

PPAPDC1B and WHSC1L1 are common drivers of the 8p11-12 amplicon, not only in breast tumors but also in pancreatic adenocarcinomas and lung tumors

Amplification of the 8p11-12 chromosomal region is a common genetic event in many epithelial cancers. In breast cancer, several genes within this region have been shown to display oncogenic activity. Among these genes, the enzyme-encoding genes, PPAPDC1B and WHSC1L1, have been identified as potential therapeutic targets. We investigated whether PPAPDC1B and WHSC1L1 acted as general driver genes, thereby serving as therapeutic targets in other tumors with 8p11-12 amplification. By using publicly available genomic data from a panel of 883 cell lines derived from different cancers, we identified the cell lines presenting amplification of both WHSC1L1 and PPAPDC1B. In particular, we focused on cell lines derived from lung cancer and pancreatic adenocarcinoma and found a correlation between the amplification of PPAPDC1B and WHSC1L1 with their overexpression. Loss-of-function studies based on the use of siRNA and shRNA demonstrated that PPAPDC1B and WHSC1L1 played a major role in regulating the survival of pancreatic adenocarcinoma and small-cell lung cancer-derived cell lines, both in anchorage-dependent and anchorage-independent conditions, displaying amplification and overexpression of these genes. We also demonstrated that PPAPDC1B and WHSC1L1 regulated xenograft growth in these cell lines. Finally, quantitative RT-PCR experiments after PPAPDC1B and WHSC1L1 knockdown revealed exclusive PPAPDC1B and WHSC1L1 gene targets in small-cell lung cancer and pancreatic adenocarcinoma-derived cell lines compared with breast cancer.

Lapatinib in combination with paclitaxel for the treatment of patients with metastatic breast cancer whose tumors overexpress HER2

SUMMARY Metastatic breast cancer (MBC) is the leading cause of cancer death for women worldwide. Amplification of the HER2 gene has been observed in approximately 20–25% of human breast cancers, and is associated with aggressive disease and a poor prognosis, and reduced progression-free survival and overall survival. Inhibition of HER2 activity has been an effective strategy against HER2-positive breast cancers. In the first-line metastatic setting, the combination of trastuzumab with paclitaxel is well-tolerated, offering significant clinical benefit to patients with HER2-positive MBC. It has also been shown that lapatinib combined with paclitaxel offers a significant survival benefit over paclitaxel alone in first-line treatment of HER2-positive MBC, especially when trastuzumab is not available.

Randomized trial of lapatinib versus placebo added to paclitaxel in the treatment of human epidermal growth factor receptor 2-overexpressing metastatic breast cancer

PURPOSE

Lapatinib is an oral small-molecule tyrosine kinase inhibitor of both epidermal growth factor receptor and human epidermal growth factor receptor 2 (HER2). This study is designed to test whether the addition of lapatinib to paclitaxel improves overall survival (OS) compared with placebo plus paclitaxel in patients with HER2-overexpressing metastatic breast cancer (MBC).

PATIENTS AND METHODS

This phase III, randomized, double-blind study assessed the efficacy and safety of lapatinib plus paclitaxel compared with placebo plus paclitaxel in patients with newly diagnosed HER2-positive MBC. The primary end point was OS. Secondary end points included progression-free survival (PFS), overall response rate (ORR), clinical benefit rate, and safety.

RESULTS

The addition of lapatinib to paclitaxel significantly improved OS versus paclitaxel (treatment hazard ratio [HR], 0.74; 95% CI, 0.58 to 0.94; P = .0124); median OS was 27.8 versus 20.5 months, respectively. Median PFS was prolonged by 3.2 months, from 6.5 months with placebo plus paclitaxel to 9.7 months with lapatinib plus paclitaxel (HR, 0.52; 95% CI, 0.42 to 0.64; stratified log-rank P < .001). ORR was significantly higher with lapatinib plus paclitaxel compared with placebo plus paclitaxel (69% v 50%, respectively; P < .001). The incidence of grades 3 and 4 diarrhea and neutropenia was higher in the lapatinib plus paclitaxel arm. Only 4% of patients in this group reported febrile neutropenia. Cardiac events were low grade, asymptomatic, and mostly reversible. The incidence of hepatic events was similar in both arms. There were no fatal adverse events in the lapatinib plus paclitaxel arm.

CONCLUSION

This trial demonstrated that lapatinib combined with paclitaxel offers a significant and clinically meaningful survival advantage over paclitaxel alone in patients with HER2-positive MBC.

ErbB2-dependent chemotaxis requires microtubule capture and stabilization coordinated by distinct signaling pathways

Activation of the ErbB2 receptor tyrosine kinase stimulates breast cancer cell migration. Cell migration is a complex process that requires the synchronized reorganization of numerous subcellular structures including cell-to-matrix adhesions, the actin cytoskeleton and microtubules. How the multiple signaling pathways triggered by ErbB2 coordinate, in time and space, the various processes involved in cell motility, is poorly defined. We investigated the mechanism whereby ErbB2 controls microtubules and chemotaxis. We report that activation of ErbB2 increased both cell velocity and directed migration. Impairment of the Cdc42 and RhoA GTPases, but not of Rac1, prevented the chemotactic response. RhoA is a key component of the Memo/ACF7 pathway whereby ErbB2 controls microtubule capture at the leading edge. Upon Memo or ACF7 depletion, microtubules failed to reach the leading edge and cells lost their ability to follow the chemotactic gradient. Constitutive ACF7 targeting to the membrane in Memo-depleted cells reestablished directed migration. ErbB2-mediated activation of phospholipase C gamma (PLCγ) also contributed to cell guidance. We further showed that PLCγ signaling, via classical protein kinases C, and Memo signaling converged towards a single pathway controlling the microtubule capture complex. Finally, inhibiting the PI3K/Akt pathway did not affect microtubule capture, but disturbed microtubule stability, which also resulted in defective chemotaxis. PI3K/Akt-dependent stabilization of microtubules involved repression of GSK3 activity on the one hand and inhibition of the microtubule destabilizing protein, Stathmin, on the other hand. Thus, ErbB2 triggers distinct and complementary pathways that tightly coordinate microtubule capture and microtubule stability to control chemotaxis.

ErbB2, FoxM1 and 14-3-3ζ prime breast cancer cells for invasion in response to ionizing radiation

ErbB2 is frequently highly expressed in premalignant breast cancers, including ductal carcinoma in situ (DCIS); however, little is known about the signals or pathways it contributes to progression into the invasive/malignant state. Radiotherapy is often used to treat early premalignant lesions regardless of ErbB2 status. Here, we show that clinically relevant doses of ionizing radiation (IR)-induce cellular invasion of ErbB2-expressing breast cancer cells, as well as MCF10A cells overexpressing ErbB2. ErbB2-negative breast cancer cells, such as MCF7 and T47D, do not invade following treatment with IR nor do MCF10A cells overexpressing epidermal growth factor receptor. ErbB2 becomes phosphorylated at tyrosine 877 in a dose- and time- dependent manner following exposure to X-rays, and activates downstream signaling cascades including PI3K/Akt. Inhibition of these pathways, as well as inhibition of reactive oxygen species (ROS) with antioxidants, prevents IR-induced invasion. Activation of ErbB2-dependent signaling results in upregulation of the forkhead family transcription factor, FoxM1, and its transcriptional targets, including matrix metalloproteinase 2 (MMP2). Inhibition of FoxM1 by RNA interference prevented induction of invasion by IR, and overexpression of FoxM1 in MCF10A cells was sufficient to promote IR-induced invasion. Moreover, we found that 14-3-3ζ is also upregulated by IR in cancer cells in a ROS-dependent manner, is required for IR-induced invasion in ErbB2-positive breast cancer cells and together with FoxM1 is sufficient for invasion in ErbB2-negative breast cancer cells. Thus, our data show that IR-mediated activation of ErbB2 and induction of 14-3-3ζ collaborate to regulate FoxM1 and promote invasion of breast cancer cells and furthermore, may serve as therapeutic targets to enhance radiosensitivity of breast cancers.

HER2 stabilizes EGFR and itself by altering autophosphorylation patterns in a manner that overcomes regulatory mechanisms and promotes proliferative and transformation signaling

One of the causes of breast cancer is overexpression of the human epidermal growth factor receptor 2 (HER2). Enhanced receptor autophosphorylation and resistance to activation-induced down regulation have been suggested as mechanisms for HER2-induced sustained signaling and cell transformation. However, the molecular mechanisms underlying these possibilities remain incompletely understood. In the current report, we present evidence that show that HER2 overexpression does not lead to receptor hyper-autophosphorylation, but alters patterns in a manner that favors receptor stability and sustained signaling. Specifically, HER2 overexpression blocks EGFR tyrosine phosphorylation on Y1045 and Y1068, the known docking sites of c-Cbl and Grb2, respectively, while promoting phosphorylation on Y1173, the known docking site of the Gab adaptor proteins and phospholipase C gamma (PLCγ). Under these conditions, HER2 itself is phosphorylated on Y1221/1222, with no known role, and on Y1248 that corresponds to Y1173 of EGFR. Interestingly, suppressed EGFR autophosphorylation on the Grb2 and c-Cbl binding sites correlated with receptor stability and sustained signaling, suggesting that HER2 accomplishes these tasks by altering autophosphorylation patterns. In conformity with these findings, mutation of the Grb2 binding site on EGFR (Y1068F-EGFR) conferred resistance to ligand-induced degradation which in turn induced sustained signaling, and increased cell proliferation and transformation. These findings suggest that the Grb2 binding site on EGFR is redundant for signaling, but critical for receptor regulation. On the other hand, mutation of the putative Grb2 binding site in HER2 (Y1139) did not affect stability, signaling or transformation, suggesting that Y1139 in HER2 may not serve as a Grb2 binding site. In agreement with the role of EGFR in HER2 signaling, inhibition of EGFR expression reduced HER2-induced anchorage-independent growth and tumorigenesis. These results imply that complementing HER2-targeted therapies with anti-EGFR drugs may be beneficial in HER2-positive breast cancer.

Overall survival benefit with lapatinib in combination with trastuzumab for patients with human epidermal growth factor receptor 2-positive metastatic breast cancer: final results from the EGF104900 Study

PURPOSE

Phase III EGF104900 data demonstrated that lapatinib plus trastuzumab significantly improved progression-free survival (PFS) and clinical benefit rate versus lapatinib monotherapy, offering a chemotherapy-free option for patients with heavily pretreated human epidermal growth factor receptor 2 (HER2) -positive metastatic breast cancer (MBC). Final planned overall survival (OS) analysis from EGF104900 is reported here.

PATIENTS AND METHODS

Patients with HER2-positive MBC whose disease progressed during prior trastuzumab-based therapies were randomly assigned to receive lapatinib monotherapy or lapatinib in combination with trastuzumab. OS and updated PFS data are presented using Kaplan-Meier curves and log-rank tests stratified for hormone receptor and visceral disease status. Subgroup analyses were conducted to identify characteristics of patients deriving the greatest clinical benefit.

RESULTS

In this updated final analysis of all patients randomly assigned with strata (n = 291), lapatinib plus trastuzumab continued to show superiority to lapatinib monotherapy in PFS (hazard ratio [HR], 0.74; 95% CI, 0.58 to 0.94; P = .011) and offered significant OS benefit (HR, 0.74; 95% CI, 0.57 to 0.97; P = .026). Improvements in absolute OS rates were 10% at 6 months and 15% at 12 months in the combination arm compared with the monotherapy arm. Multiple baseline factors, including Eastern Cooperative Oncology Group performance status of 0, nonvisceral disease, < three metastatic sites, and less time from initial diagnosis until random assignment, were associated with improved OS. Incidence of adverse events was consistent with previously reported rates.

CONCLUSION

These data demonstrated a significant 4.5-month median OS advantage with the lapatinib and trastuzumab combination and support dual HER2 blockade in patients with heavily pretreated HER2-positive MBC.

The signaling and transformation potency of the overexpressed HER2 protein is dependent on the normally-expressed EGFR

Human epidermal growth factor receptor 2 (HER2) belongs to the EGFR family of receptor tyrosine kinases that comprises four members. As opposed to the other family members, HER2 does not require ligand binding for activation. Hence, HER2 molecules can undergo spontaneous dimerization, autophosphorylation and activation of downstream signaling pathways especially under conditions of overexpression, a commonly encountered phenomenon in breast cancer. In this study, we sought to investigate the mechanism by which HER2 musters signaling and transformation potency. We show that HER2 overexpression per se induces a significant increase in basal mitogenic and cell survival signaling, which was augmented by EGF stimulation. Inhibition of the normally expressed EGFR significantly suppressed the ability of overexpressed HER2 to induce enhanced signaling and cell transformation, suggesting that HER2 requires the EGFR and potentially other members to maximize its signaling and transformation potency. The novel observation revealed by prolonged EGF stimulation studies was the biphasic signaling pattern in the presence of HER2 overexpression that suggested the induction of a short-circuited mechanism, permitting sustained signaling. Our results further show that the short-circuited signaling was due to the re-shuttling of internalized receptor molecules to the Rab11-positive recycling endosomes, while suppressing channeling to the LAMP1-positive lysosome-targeting endosomes. Therefore, HER2's oncogenicity is dependent, not only on its constitutively active nature, but also on its ability to muster collaborative signaling from family members through modulation of ligand-induced receptor regulation.

MEMO associated with an ErbB2 receptor phosphopeptide reveals a new phosphotyrosine motif

Tyrosine phosphorylations are essential in signal transduction. Recently, a new type of phosphotyrosine binding protein, MEMO (Mediator of ErbB2-driven cell motility), has been reported to bind specifically to an ErbB2-derived phosphorylated peptide encompassing Tyr-1227 (PYD). Structural and functional analyses of variants of this peptide revealed the minimum sequence required for MEMO recognition. Using a docking approach we have generated a structural model for MEMO/PYD complex and compare this new phosphotyrosine motif to SH2 and PTB phosphotyrosine motives.

Optimizing chemotherapy-free survival for the ER/HER2-positive metastatic breast cancer patient

The recent incremental advances made in the treatment of metastatic breast cancer have elicited potential for survival extension in this treatable, yet incurable, population of breast cancer patients. Clinicians have focused on targeted therapies, which aim at signaling receptors such as the human epidermal receptor superfamily, the estrogen receptor, VEGF, the insulin-like growth factor receptor, the hepatocyte growth factor receptor (cMET), phosphoinositide 3-kinase, mTOR, and many others.

Lapatinib plus capecitabine in treating HER2-positive advanced breast cancer: efficacy, safety, and biomarker results from Chinese patients

Overexpression of human epidermal growth factor receptor-2 (HER2) in metastatic breast cancer (MBC) is associated with poor prognosis. This single-arm open-label trial (EGF109491; NCT00508274) was designed to confirm the efficacy and safety of lapatinib in combination with capecitabine in 52 heavily pretreated Chinese patients with HER2-positive MBC. The primary endpoint was clinical benefit rate (CBR). Secondary endpoints included progression-free survival (PFS), time to response (TTR), duration of response (DoR), central nervous system (CNS) as first site of relapse, and safety. The results showed that there were 23 patients with partial responses and 7 patients with stable disease, resulting in a CBR of 57.7%. The median PFS was 6.34 months (95% confidence interval, 4.93-9.82 months). The median TTR and DoR were 4.07 months (range, 0.03-14.78 months) and 6.93 months (range, 1.45-9.72 months), respectively. Thirteen (25.0%) patients had new lesions as disease progression. Among them, 2 (3.8%) patients had CNS disease reported as the first relapse. The most common toxicities were palmar-plantar erythrodysesthesia (59.6%), diarrhea (48.1%), rash (48.1%), hyperbilirubinemia (34.6%), and fatigue (30.8%). Exploratory analyses of oncogenic mutations of PIK3CA suggested that of 38 patients providing a tumor sample, baseline PIK3CA mutation status was not associated with CBR (P = 0.639) or PFS (P = 0.989). These data confirm that the lapatinib plus capecitabine combination is an effective and well-tolerated treatment option for Chinese women with heavily pretreated MBC, irrespective of PIK3CA status.

ERBB2 gene amplification in oral squamous cell malignancies: a correlation with tumor progression and gene expression

OBJECTIVES

Chromosomal instability is hallmark of carcinoma. Amplification of chromosome 17q11-q12 is present in some oral squamous cell cancer (OSCC) cases. In this study, we investigated the copy number variations of ERBB2 gene, which is located at this locus in collected OSCC samples and their correlation with tumor progression and gene expression.

STUDY DESIGN

Quantitative real-time polymerase chain reaction was performed to detect the copy number of ERBB2 gene and the mRNA expression in 92 OSCC samples with matched adjacent normal tissues (ANTs). Proportional odds regression and 2-way repeated measurement analysis of variance were used to analyze the association between copy number variations and mRNA expression of the targeted gene.

RESULTS

Copy number gains of ERBB2 were detected in some of the OSCCs (19.6%, 18/92) and correlated with tumor stage (P < .001). Copy number gains of ERBB2 also showed a positive correlation with mRNA overexpression in OSCCs (P < .001). However, enhanced ERBB2 mRNA expression was also detected in a group of OSCC samples with unaltered copy number of ERBB2 gene (P < .05).

CONCLUSIONS

Copy number increase of ERBB2 is observed in OSCCs and correlates with gene overexpression in these tumors. In addition, overexpression of ERBB2 is also observed in some OSCCs that lack copy number changes, indicating involvement of another mechanism.

Transforming properties of 8p11-12 amplified genes in human breast cancer

Amplification of the 8p11-12 region has been found in about 15% of human breast cancers and is associated with poor prognosis. Earlier, we used genomic analysis of copy number and gene expression to perform a detailed analysis of the 8p11-12 amplicon to identify candidate oncogenes in breast cancer. We identified 21 candidate genes and provided evidence that three genes, namely, LSM-1, TC-1, and BAG4, have transforming properties when overexpressed. In the present study, we systematically investigated the transforming properties of 13 newly identified 8p11-12 candidate oncogenes in vitro. WHSC1L1, DDHD2, and ERLIN2 were most potently transforming oncogenes based on the number of altered phenotypes expressed by the cells. WHSC1L1 contains a PWWP-domain that is a methyl-lysine recognition motif involved in histone code modification and epigenetic regulation of gene expression. Knockdown of WHSC1L1 in 8p11-12-amplified breast cancer cells resulted in profound loss of growth and survival of these cells. Further, we identified several WHSC1L1 target genes, one of which is iroquois homeobox 3 gene (IRX3), a member of the Iroquois homeobox transcription factor family.

Combined effects of lapatinib and bortezomib in human epidermal receptor 2 (HER2)-overexpressing breast cancer cells and activity of bortezomib against lapatinib-resistant breast cancer cells

Lapatinib and bortezomib are highly active against breast cancer cells. Breast cancer patients who initially respond to lapatinib may eventually manifest acquired resistance to this treatment. Thus, the identification of novel agents that may prevent or delay the development of acquired resistance to lapatinib is critical. In the current study, we show that the combination of lapatinib and bortezomib results in a synergistic growth inhibition in human epidermal receptor 2 (HER2)-overexpressing breast cancer cells and that the combination enhances apoptosis of SK-BR-3 cells. Importantly, we found that the combination of lapatinib plus bortezomib more effectively blocked activation of the HER2 pathway in SK-BR-3 cells, compared with monotherapy. In addition, we established a model of acquired resistance to lapatinib by chronically challenging SK-BR-3 breast cancer cells with increasing concentrations of lapatinib. Here, we showed that bortezomib notably induced apoptosis of lapatinib-resistant SK-BR-3 pools and further inhibited HER2 signaling in the resistant cells. Taken together, the current data indicate a synergistic interaction between lapatinib and bortezomib in HER2-overexpressing breast cancer cells and provide the rationale for the clinical evaluation of these two noncross-resistant targeted therapies. The combination of lapatinib and bortezomib may be a potentially novel approach to prevent or delay the onset of acquired resistance to lapatinib in HER2-overxpressing/estrogen receptor (ER)-negative breast cancers.

An open-label expanded access study of lapatinib and capecitabine in patients with HER2-overexpressing locally advanced or metastatic breast cancer

BACKGROUND

The Lapatinib Expanded Access Program (LEAP) was designed to provide access to lapatinib plus capecitabine for HER2-positive metastatic breast cancer patients who previously received an anthracycline, a taxane, and a trastuzumab and had no other treatment options.

PATIENTS AND METHODS

LEAP opened globally and enrollment continued until lapatinib received regulatory approval in each participating country. Patients were assessed for progression-free survival (PFS) and overall survival (OS) and monitored for serious adverse events (SAEs).

RESULTS

As of 30 September 2008, 4283 patients from 45 countries enrolled in LEAP. The median treatment duration was 24.7 weeks. The most common drug-related SAEs were diarrhea (9.7%), vomiting (4.3%), and nausea (2.4%) and were mainly grade 3 or higher. The incidences of special interest SAEs were decreased left ventricle ejection fraction (0.5%), interstitial lung disease/pneumonitis (0.2%), and serious hepatobiliary events (0.4%). This safety profile is consistent with the overall lapatinib program. The median PFS and OS were 21.1 [95% confidence interval (CI) = 20.1-22.3] and 39.6 (95% CI = 37.7-40.7) weeks, respectively (n = 4006). Subgroup analysis showed longer PFS and OS in patients who had not received prior capecitabine.

CONCLUSIONS

These results demonstrate the safety and efficacy of lapatinib in a broader patient population compared with a clinical trial.

Molecular mechanism for SHP2 in promoting HER2-induced signaling and transformation

The Src homology phosphotyrosyl phosphatase 2 (SHP2) plays a positive role in HER2-induced signaling and transformation, but its mechanism of action is poorly understood. Given the significance of HER2 in breast cancer, defining a mechanism for SHP2 in the HER2 signaling pathway is of paramount importance. In the current report we show that SHP2 positively modulates the Ras-extracellular signal-regulated kinase 1 and 2 and the phospoinositide-3-kinase-Akt pathways downstream of HER2 by increasing the half-life the activated form of Ras. This is accomplished by dephosphorylating an autophosphorylation site on HER2 that serves as a docking platform for the SH2 domains of the Ras GTPase-activating protein (RasGAP). The net effect is an increase in the intensity and duration of GTP-Ras levels with the overall impact of enhanced HER2 signaling and cell transformation. In conformity to these findings, the HER2 mutant that lacks the SHP2 target site exhibits an enhanced signaling and cell transformation potential. Therefore, SHP2 promotes HER2-induced signaling and transformation at least in part by dephosphorylating a negative regulatory autophosphorylation site. These results suggest that SHP2 might serve as a therapeutic target against breast cancer and other cancers characterized by HER2 overexpression.

Blockade of protein geranylgeranylation inhibits Cdk2-dependent p27Kip1 phosphorylation on Thr187 and accumulates p27Kip1 in the nucleus: implications for breast cancer therapy

We describe the design of a potent and selective peptidomimetic inhibitor of geranylgeranyltransferase I (GGTI), GGTI-2418, and its methyl ester GGTI-2417, which increases the levels of the cyclin-dependent kinase (Cdk) inhibitor p27(Kip1) and induces breast tumor regression in vivo. Experiments with p27(Kip1) small interfering RNA in breast cancer cells and p27(Kip1) null murine embryonic fibroblasts demonstrate that the ability of GGTI-2417 to induce cell death requires p27(Kip1). GGTI-2417 inhibits the Cdk2-mediated phosphorylation of p27(Kip1) at Thr187 and accumulates p27(Kip1) in the nucleus. In nude mouse xenografts, GGTI-2418 suppresses the growth of human breast tumors. Furthermore, in ErbB2 transgenic mice, GGTI-2418 increases p27(Kip1) and induces significant regression of breast tumors. We conclude that GGTIs' antitumor activity is, at least in part, due to inhibiting Cdk2-dependent p27(Kip1) phosphorylation at Thr187 and accumulating nuclear p27(Kip1). Thus, GGTI treatment might improve the poor prognosis of breast cancer patients with low nuclear p27(Kip1) levels.

SHP2 is up-regulated in breast cancer cells and in infiltrating ductal carcinoma of the breast, implying its involvement in breast oncogenesis

AIMS

To determine whether Src homology phosphotyrosyl phosphatase 2 (SHP2) is up-regulated in breast cancer and, if so, to determine whether its up-regulation has any relationship with clinical variables of breast cancer.

METHODS AND RESULTS

Immunoblotting, immunohistochemistry and immunofluorescence microscopy were used to assess the state of SHP2 expression in breast cancer cells and in infiltrating ductal carcinoma (IDC) of breast. The possible role of SHP2 in breast cancer cell transformation was determined by dominant-negative expression and anchorage-independent growth assays. All of the breast cancer cell lines tested and 72% of IDC breast tumours analysed had increased amounts of the SHP2 protein. In support of its positive role, dominant-negative SHP2 blocked anchorage-independent growth of breast cancer cells. Furthermore, overexpression of SHP2 seemed to have a positive relationship to HER2 overexpression, nuclear accumulation of hormone receptors, higher tumour grade and lymph node metastasis, but not to age of breast cancer patients.

CONCLUSION

SHP2 is a widely overexpressed signalling protein in IDC breast tumours. Given SHP2's positive role in cell growth, transformation and stem cell survival, the positive relationship of its overexpression to lymph node metastasis, nuclear accumulation of hormone receptors and higher tumour grade suggests that SHP2 promotes breast oncogenesis.

Trastuzumab induces gastrointestinal side effects in HER2-overexpressing breast cancer patients

PURPOSE

To characterise the gastrointestinal toxicities associated with Trastuzumab administration in HER2-overexpressing breast cancer patients.

METHODS

All patients (n = 46) who received Trastuzumab as a single agent or in conjunction with conventional anti-cancer treatment within the Royal Adelaide Hospital Cancer Centre from 2002-2007 were included in this study. A retrospective analysis of case-notes was conducted to investigate the toxicities associated with Trastuzumab.

RESULTS

Trastuzumab as a single agent induced toxicities following 22% of administrations. Gastrointestinal toxicities were observed following 12% of administrations and included nausea and vomiting, diarrhoea, abdominal pain and bloating. However, other prominent toxicities that were not related to the gastrointestinal tract were also observed including fatigue and lung symptoms (10.4%). Elderly patients (> or =60 years) and those with metastatic disease experienced the highest frequency of toxicity.

CONCLUSION

Trastuzumab induces a range of gastrointestinal toxicities in HER2-overexpressing breast cancer patients. These toxicities are separate to those caused by concurrent chemotherapy and/or radiotherapy.

Multiplexed cell signaling analysis of human breast cancer applications for personalized therapy

Phosphoprotein driven cellular signaling events represent most of the new molecular targets for cancer treatment. Application of reverse-phase protein microarray technology for the study of ongoing signaling activity within breast tumor specimens holds great potential for elucidating and profiling signaling activity in real-time for patient-tailored therapy. Analysis of laser capture microdissection primary human breast tumors and metastatic lesions reveals pathway specific profiles and a new way to classify cancer based on functional signaling portraits. Moreover, the data demonstrate the requirement of laser capture microdissection for analysis and reveal the metastasis-specific changes that occur within a new microenvironment. Analysis of biopsy material from clinical trials for targeted therapeutics demonstrates the feasibility and utility of comprehensive signal pathway activation profiling for molecular analysis.