Role of proliferation in HER2 status predicted response to doxorubicin

Inhibiting HER3 Hyperphosphorylation in HER2-Overexpressing Breast Cancer through Multimodal Therapy with Branched Gold Nanoshells

Treatment failure in breast cancers overexpressing human epidermal growth factor receptor 2 (HER2) is associated mainly to the upregulation of human epidermal growth factor receptor 3 (HER3) oncoprotein linked to chemoresitence. Therefore, to increase patient survival, here a multimodal theranostic nanoplatform targeting both HER2 and HER3 is developed. This consists of doxorubicin-loaded branched gold nanoshells functionalized with the near-infrared (NIR) fluorescent dye indocyanine green, a small interfering RNA (siRNA) against HER3, and the HER2-specific antibody Transtuzumab, able to provide a combined therapeutic outcome (chemo- and photothermal activities, RNA silencing, and immune response). In vitro assays in HER2+ /HER3+ SKBR-3 breast cancer cells have shown an effective silencing of HER3 by the released siRNA and an inhibition of HER2 oncoproteins provided by Trastuzumab, along with a decrease of the serine/threonine protein kinase Akt (p-AKT) typically associated with cell survival and proliferation, which helps to overcome doxorubicin chemoresistance. Conversely, adding the NIR light therapy, an increment in p-AKT concentration is observed, although HER2/HER3 inhibitions are maintained for 72 h. Finally, in vivo studies in a tumor-bearing mice model display a significant progressively decrease of the tumor volume after nanoparticle administration and subsequent NIR light irradiation, confirming the potential efficacy of the hybrid nanocarrier.

The role of HER2 alterations in clinicopathological and molecular characteristics of breast cancer and HER2-targeted therapies: a comprehensive review

Breast cancer (BC) is the most common malignancy in women and one of the leading causes of cancer mortality, despite significant treatment advancements over the last decades. Human epidermal growth factor receptor-2 (HER2) is a member of the ERBB family of receptor tyrosine kinases which have long been known to mediate cancer cell growth and invasion through constitutive activation of oncogenic downstream signaling, such as PI3K/Akt/mTOR and MAPK. Overexpression/amplification of HER2 in various tumors, especially BC, offers the possible therapeutic potential for target therapies. HER2-targeted therapies, either with a combination of chemotherapy or through multi-anti-HER2 therapies without chemotherapy, have significantly improved the prognosis of HER2-positive tumors. In recent years, novel anti-HER2 agents and combination therapies have garnered much attention, especially for heavily treated advanced or metastatic BCs. HER2-positive BC is biologically a heterogeneous group depending on HER2 activation mechanisms, hormone receptor status, genome variations, tumor heterogeneity, and treatment resistance, which affect the treatment benefit and patients' outcomes. This review will discuss HER2 alternations (gene amplification or receptor overexpression) in BC, their correlation with clinicopathological characteristics and molecular characteristics, and HER2-based therapies in tumors with HER2 overexpression/amplification.

Cancer chemotherapy: insights into cellular and tumor microenvironmental mechanisms of action

Chemotherapy has historically been the mainstay of cancer treatment, but our understanding of what drives a successful therapeutic response remains limited. The diverse response of cancer patients to chemotherapy has been attributed principally to differences in the proliferation rate of the tumor cells, but there is actually very little experimental data supporting this hypothesis. Instead, other mechanisms at the cellular level and the composition of the tumor microenvironment appear to drive chemotherapy sensitivity. In particular, the immune system is a critical determinant of chemotherapy response with the depletion or knock-out of key immune cell populations or immunological mediators completely abrogating the benefits of chemotherapy in pre-clinical models. In this perspective, we review the literature regarding the known mechanisms of action of cytotoxic chemotherapy agents and the determinants of response to chemotherapy from the level of individual cells to the composition of the tumor microenvironment. We then summarize current work toward the development of dynamic biomarkers for response and propose a model for a chemotherapy sensitive tumor microenvironment.

Bioprinting Decellularized Breast Tissue for the Development of Three-Dimensional Breast Cancer Models

The tumor extracellular matrix (ECM) plays a vital role in tumor progression and drug resistance. Previous studies have shown that breast tissue-derived matrices could be an important biomaterial to recreate the complexity of the tumor ECM. We have developed a method for decellularizing and delipidating a porcine breast tissue (TDM) compatible with hydrogel formation. The addition of gelatin methacrylamide and alginate allows this TDM to be bioprinted by itself with good printability, shape fidelity, and cytocompatibility. Furthermore, this bioink has been tuned to more closely recreate the breast tumor by incorporating collagen type I (Col1). Breast cancer cells (BCCs) proliferate in both TDM bioinks forming cell clusters and spheroids. The addition of Col1 improves the printability of the bioink as well as increases BCC proliferation and reduces doxorubicin sensitivity due to a downregulation of HSP90. TDM bioinks also allow a precise three-dimensional printing of scaffolds containing BCCs and stromal cells and could be used to fabricate artificial tumors. Taken together, we have proven that these novel bioinks are good candidates for biofabricating breast cancer models.

Liver Cancer Cell Lines Treated with Doxorubicin under Normoxia and Hypoxia: Cell Viability and Oncologic Protein Profile

Hepatocellular carcinoma is often treated with a combination of doxorubicin and embolization, exposing it to high concentrations and hypoxia. Separation of the possible synergistic effect of this combination in vivo is difficult. Here, treatment with doxorubicin, under hypoxia or normoxia in different liver cancer cell lines, was evaluated. Liver cancer cells HepG2, Huh7, and SNU449 were exposed to doxorubicin, hypoxia, or doxorubicin + hypoxia with different duration. Treatment response was evaluated with cell viability, apoptosis, oxidative stress, and summarized with IC₅₀. The protein profile of a 92-biomarker panel was analyzed on cells treated with 0 or 0.1 µM doxorubicin during 6 or 72 h, under normoxia or hypoxia. Hypoxia decreased viability of HepG2 and SNU499. HepG2 was least and SNU449 most tolerant to doxorubicin treatment. Cytotoxicity of doxorubicin increased over time in HepG2 and Huh7. The combination of doxorubicin + hypoxia affected the cells differently. Normalized protein expression was lower for HepG2 than Huh7 and SNU449. Hierarchical clustering separated HepG2 from Huh7 and SNU449. These three commonly used cell lines have critically different responses to chemotherapy and hypoxia, which was reflected in their different protein expression profile. These different responses suggest that tumors can respond differently to the combination of local chemotherapy and embolization.

Mechanisms for DNA-damaging agent-induced inactivation of ErbB2 and ErbB3 via the ERK and p38 signaling pathways

Cisplatin (CDDP) and doxorubicin (DOX) are chemotherapeutic drugs that trigger apoptosis by inducing DNA-damage. A previous study using breast cancer cells demonstrated the negative feedback modulation of the epidermal growth factor receptor (EGFR) and receptor tyrosine-protein kinase erbB-2 (ErbB2) via extracellular signal-regulated kinase (ERK)-mediated phosphorylation of conserved Thr-669 and Thr-677 residues, respectively, in the juxtamembrane domain. In addition, CDDP has been identified to cause negative feedback inhibition of activated EGFR in lung cancer cells. In the present study, the role of phosphorylation in the feedback control of the ErbB2/ErbB3 heterodimer in human breast and gastric cancer cells was investigated. Phosphorylation of ErbB2 at Thr-677 was induced by CDDP and DOX, which in turn reduced tyrosine autophosphorylation of ErbB2 and ErbB3. Treatment with trametinib, a mitogen-activated protein kinase inhibitor that blocks ERK-mediated Thr-677 phosphorylation, and substitution of Thr-677 to alanine, blocked the feedback inhibition of ErbB2 and ErbB3. In addition, these agents caused the degradation of ErbB proteins through the activation of p38 mitogen-activated protein kinase (p38) and ERK. These results demonstrate that chemotherapeutic agents trigger ERK- and p38-mediated post-translational downregulation of ErbB receptors.

The Static Magnetic Field Remotely Boosts the Efficiency of Doxorubicin through Modulating ROS Behaviors

Exposure to magnetic field (MF) can affect cellular metabolism remotely. Cardio-toxic effects of Doxorubicin (DOXO) have limited clinical uses at high dose. MF due to its effect on reactive oxygen species (ROS) lifetime, may provide a suitable choice to boost the efficacy of this drug at low dose. Here, we investigated the potential effects of homogenous static magnetic field (SMF) on DOXO-induced toxicity and proliferation rate of cancer cells. The results indicated that SMF similar to DOXO decreased the cell viability as well as the proliferation rate of MCF-7 and HFF cells. Moreover, combination of 10 mT SMF and 0.1 µM DOXO decreased the viability and proliferation rate of cancer and normal cells in a synergetic manner. In spite of high a GSH level in cancer cell, SMF boosts the generation and lifetime of ROS at low dose of DOXO, and overcame to GSH mediated drug resistance. The results also confirmed that SMF exposure decreased 50% iron content of cells, which is attributed to iron homeostasis. In conclusion, these findings suggest that SMF can decrease required dose of chemotherapy drugs such as DOXO and thereby decrease their side effect.

Activation Status of Receptor Tyrosine Kinases as an Early Predictive Marker of Response to Chemotherapy in Osteosarcoma

Receptor tyrosine kinases (RTKs) are membrane receptors that play a vital role in various biological processes, in particular, cell survival, cell proliferation, and cell differentiation. These cellular processes are composed of multitiered signaling cascades of kinases starting from ligand binding to extracellular domains of RTKs that activate the entire pathways through tyrosine phosphorylation of the receptors and downstream effectors. A previous study reported that, based on proteomics data, RTKs were a major candidate target for osteosarcoma. In this study, activation profiles of six candidate RTKs, including c-Met, c-Kit, VEGFR2, HER2, FGFR1, and PDGFRα, were directly examined from chemonaive fresh frozen tissues of 32 osteosarcoma patients using a multiplex immunoassay. That examination revealed distinct patterns of tyrosine phosphorylation of RTKs in osteosarcoma cases. Unsupervised hierarchical clustering was calculated using Pearson uncentered correlation coefficient to classify RTKs into two groups-Group A (c-Met, c-Kit, VEGFR2, and HER2) and Group B (FGFR1 and PDGFRα)-based on tyrosine phosphorylation patterns. Nonactivation of all Group A RTKs was associated with shorter overall survival in stage IIB osteosarcoma patients. Percentages of tumor necrosis in patients with inactive Group A RTKs were significantly lower than those in patients with at least one active Group A RTK. Paired primary osteosarcoma cells with fresh osteosarcoma tissue were extracted and cultured for cytotoxicity testing. Primary cells with active Group A RTKs tended to be sensitive to doxorubicin and cisplatin. We also found that osteosarcoma cells with active Group A RTKs were more proliferative than cells with inactive Group A RTKs. These findings indicate that the activation pattern of Group A RTKs is a potential risk stratification and chemoresponse predictor and might be used to guide the optimum chemotherapy regimen for osteosarcoma patients.

Comparing the therapeutic potential of thermosensitive liposomes and hyperthermia in two distinct subtypes of breast cancer

Local drug delivery of Doxorubicin (Dox) with thermosensitive liposomes (TSL) and hyperthermia (HT) has shown preclinically to achieve high local drug concentrations with good therapeutic efficacy. Currently, this is clinically studied for treatment of chest wall recurrence of breast cancer, however with various outcomes. This study examines the potency of neoadjuvant TSL HT combination therapy in two orthotopic mouse models of human breast cancer, MDA-MB-231 and T-47D, which morphologically correlate to mesenchymal and epithelial phenotypes, respectively. Both cell lines showed improved in vitro chemosensitivity and Dox uptake at HT. Dox-loaded TSL (TSL_Dox) was stable in vitro in FBS, BALB/c-nu plasma and human plasma, although release of the drug at HT was incomplete for the latter two. Combination treatment with TSL_Dox and HT in vivo was significantly more effective against MDA-MB-231 tumors, whereas T-47D tumors showed no significant therapeutic response. Ex vivo investigation revealed a higher mean vessel density and poorly differentiated extracellular matrix (ECM) in MDA-MB-231 tumors relative to T-47D tumors. Although in vitro results of the TSL_Dox and HT treatment were favorable for both cell types, the therapeutic efficacy in vivo was remarkably different. The well-differentiated and slowly-growing T-47D tumors may provide a microenvironment that limits drug delivery to the target cell and therefore renders the therapy ineffective. Mesenchymal and invasive MDA-MB-231 tumors display higher vascularization and less mature ECM, significantly enhancing tumor response to TSL_Dox and HT treatment. These results yield insight into the efficacy of TSL treatment within different tumor microenvironments, and further advance our understanding of factors that contribute to heterogeneous therapeutic outcomes in clinical trials.

Differential expression of multidrug resistance‑related proteins in adriamycin‑resistant (pumc‑91/ADM) and parental (pumc‑91) human bladder cancer cell lines

Multidrug resistance (MDR) is the major obstacle to bladder cancer chemotherapy. Several mechanisms have been implicated in the development of MDR, including extrusion of the drug by cell membrane pumps, associated with P‑glycoprotein (P‑gp) and multidrug resistance‑associated protein (MRP); increased DNA damage repair, associated with topoisomerase II (Topo II); suppression of drug‑induced apoptosis, associated with p53; and regulation of cancer cell growth, associated with vascular endothelial growth factor (VEGF). In the present study, the expression levels of these five markers were detected in an adriamycin (ADM)‑resistant human bladder cancer cell line (pumc‑91/ADM) and its parental cell line (pumc‑91), in order to determine which marker is more important, or whether all of them participate in drug resistance. The expression levels of P‑gp, MRP, Topo II, VEGF and p53 were measured in the two cell lines by reverse transcription‑quantitative polymerase chain reaction, western blotting and immunohistochemistry. A significant increase in P‑gp, MRP and VEGF, and a decrease in Topo II mRNA expression were detected in the pumc‑91/ADM drug‑resistant cell line compared with the pumc‑91 cell line; however, no difference in p53 mRNA expression was detected between the cells. In pumc‑91/ADM cells, the protein expression levels of P‑gp and MRP were upregulated, whereas Topo II was significantly decreased. However, no marked differences in p53 or VEGF expression were detected between the two cell lines at the protein level. The cytoplasmic and cell membrane localization of P‑gp and MRP, the cytoplasmic localization of VEGF, and the nuclear localization of p53 and Topo II were confirmed in the two cell lines. The present study detected increased P‑gp and MRP, and reduced Topo II expression in pumc‑91/ADM cells compared with pumc‑91 cells; however, no difference was detected in p53 and VEGF expression between the cell lines. In conclusion, a significant upregulation of MRP and downregulation of Topo II were detected in the ADM‑resistant human bladder cancer cell line (pumc‑91/ADM) compared with in the parental cell line (pumc‑91).

Human epidermal growth factor receptor 2/neu as a novel therapeutic target in sinonasal undifferentiated carcinoma

BACKGROUND

Sinonasal undifferentiated carcinoma (SNUC) is a rare and aggressive cancer. Despite multimodal therapy, the prognosis in SNUC remains poor, and new therapies are needed. Thus, the purpose of this study was to explore potential therapeutic targets in SNUC.

METHODS

Using the human-derived SNUC MDA8788-6 cell line, we performed whole genome single nucleotide polymorphism (SNP) analysis to identify copy number changes in this line. Protein expression levels were evaluated by Western blotting. Cell growth inhibition was assessed by methylthiazol tetrazolium (MTT) and clonogenic assays. The mouse flank model was used to examine the effect of growth inhibition in vivo.

RESULTS

The ERBB2 gene was highly amplified and cell extracts showed human epidermal growth factor receptor 2 (HER2) was overexpressed and phosphorylated in MDA8788-6. Lapatinib effectively inhibited the HER2 signaling pathway in our SNUC cell line. HER2 inhibition successfully suppressed the cell growth of MDA8788-6 cells both in vitro and in vivo.

CONCLUSION

Targeting HER2 may be a promising avenue for the development of novel therapies for SNUC. © 2016 Wiley Periodicals, Inc. Head Neck 38: E1926-E1934, 2016.

Neoadjuvant therapy for breast cancer: controversies in clinical trial design and standard of care

Neoadjuvant therapy for breast cancer has been increasingly used in recent years as first-line treatment for operable breast cancer-serving as both a management strategy and a research tool. In addition to the established clinical benefits of down-staging more locally advanced cancers and improving breast-conservation rates, investigators have recognized the potential advantages of this approach in developing new therapies. Preoperative systemic therapy provides the opportunity for in vivo assessment of pharmacodynamic markers to assess biologic effects and allows new compounds to be tested in a more responsive, treatment-naive population. In addition, early surrogates of response, such as pathologic complete response (pCR) and residual cancer burden, provide proximate measures that correlate with long-term outcomes, thus potentially shortening the time needed to identify effective adjuvant therapies. Despite the advantages of neoadjuvant therapy for research and clinical practice, its use is characterized by persistent controversy and healthy debate regarding how to optimally use research findings and when to integrate them into the standard of care for daily management. Among the controversies surrounding neoadjuvant therapy use are questions about defining the best endpoint for assessing treatment efficacy, deciding when results from research should be used in daily clinical practice, and how the growing use of neoadjuvant therapy affects locoregional treatments.

Triple-negative breast cancer exhibits a favorable response to neoadjuvant chemotherapy independent of the expression of topoisomerase IIα

The present study retrospectively analyzed the utility of topoisomerase IIα expression as a prognostic marker to predict the neoadjuvant chemotherapeutic response and survival among different breast cancer subtypes. The patients were subtyped and the expression of topoisomerase IIα was determined using immunohistochemistry. All patients (n=147) received an anthracycline-containing regimen preoperatively, and 139 (95%) patients also received docetaxel. Of the 147 patients, 25 (17%) were triple-negative and 20 (17%) were human epidermal growth factor receptor 2 (HER2)-positive. Among these subtypes, a significantly higher a rate (P<0.0001) and higher incidence of topoisomerase IIα expression (P=0.036) were observed compared with that in the hormone receptor-positive and HER2-negative breast cancer types. However, the expression of topoisomerase IIα revealed no correlation with the treatment response or survival in any of the subtypes. Therefore, these results indicated that the favorable response to anthracycline-containing chemotherapy among triple-negative and HER2-positive breast cancer was independent of the expression of topoisomerase IIα.

Expression of multidrug resistance proteins in invasive ductal carcinoma of the breast

Chemotherapy is commonly used for the treatment of breast cancer. However, the resistance to chemotherapeutic agents, often mediated by multidrug resistance (MDR) mechanisms, is a common occurrence. The present study examined the expression of several MDR-related proteins (MRPs) in invasive ductal carcinoma (IDC) of the breast, and assessed their association with clinicopathological variables and their prognostic significance. In addition, immunohistochemistry was used to measure the expression of MRP, p-glycoprotein (P-gp), topoisomerase 2α (Topo2α), thymidylate synthase (TS) and glutathione-S-transferase π (GST-π) in 156 resected IDCs of the breast. Pearson's χ² test and Spearman's correlation coefficient were used to analyze the association between MDR protein expression and several clinicopathological variables. The association between each of the five MDR proteins was also examined. Furthermore, Kaplan-Meier analysis and Cox regression modeling were used to assess overall survival. The expression of MRP, P-gp, Topo2α, TS and GST-π was detected in 20.5% (32/156), 25.0% (39/156), 84.0% (131/156), 41.7% (65/156) and 41.0% (64/156) of cases examined, respectively. No correlation was identified between MRP and Topo-2α and the clinicopathological variables examined. By contrast, P-gp (χ²=20.226; P<0.0001) and GST-π (χ²=35.032; P<0.0001) were found to positively correlate with tumor grade. In addition, staining for TS was associated with axillary lymph node metastasis (χ²=42.281; P<0.0001). The expression levels of P-gp and GST-π were found to be significantly correlated (r= 0.319; P<0.0001). Furthermore, GST-π expression was elevated in estrogen receptor-negative breast cancer (χ²=17.407; P<0.0001). Tumor histological grade, in addition to TS and GST-π expression, were significant predictors of a poor survival outcome. TS and GST-π are consequently useful prognostic biomarkers in IDC, therefore, when establishing a personalized chemotherapeutic plan, the expression of MDR proteins must be considered.

Human epidermal growth factor receptor 2-positive breast cancer: which cytotoxic agent best complements trastuzumab's efficacy in vitro?

INTRODUCTION

Despite trastuzumab having enhanced selectivity for human epidermal growth factor receptor 2 (HER-2) overexpressing breast cancer cells, treatment is hampered by interindividual variation and tumors with high mitogenic potential. The lack of significant clinical benefit in certain patient cohorts suggests that HER-2 expression is ineffective as a sole prognostic indicator of response to therapy. Therefore, optimizing the clinical role of trastuzumab in drug combinations remains critical for clinical success.

AIM

To investigate the effects of trastuzumab in combination with either doxorubicin or geldanamycin on in vitro cell viability, cell cycling, apoptosis and relative HER-2 expression in HER-2-positive (SK-BR-3) and estrogen receptor-positive (MCF-7) breast adenocarcinoma models.

RESULTS

HER-2-rich SK-BR-3 cells demonstrated a greater sensitivity to the effects of doxorubicin than MCF-7 cells. Concurrent trastuzumab exposure resulted in a further reduction in cell viability. This decreased cell viability induced by doxorubicin was associated with activation of executioner caspases as well as with alterations in cell-cycle kinetics, primarily promoting S-phase accumulation. Doxorubicin had no effect on surface HER-2 density expression. Geldanamycin reduced cell viability significantly greater in SK-BR-3 than MCF-7 cells, and was associated with G2 cell-cycle accumulation. The addition of trastuzumab did not augment these effects. Geldanamycin promoted substantial reductions in relative surface HER-2 density in SK-BR-3 cells.

CONCLUSION

The in vitro data supported the rationale for using doxorubicin in trastuzumab-based therapies. Therefore, despite the incidence of cardiotoxicity, doxorubicin could retain a fundamental role in treating HER-2-positive breast cancer. While geldanamycin is a potent cytotoxic agent, its concurrent use with trastuzumab requires further research into the transient or permanent nature of alterations in HER-2 status in cell progeny.

Imaging tumor-stroma interactions during chemotherapy reveals contributions of the microenvironment to resistance

Little is known about the dynamics of cancer cell death in response to therapy in the tumor microenvironment. Intravital microscopy of chemotherapy-treated mouse mammary carcinomas allowed us to follow drug distribution, cell death, and tumor-stroma interactions. We observed associations between vascular leakage and response to doxorubicin, including improved response in matrix metalloproteinase-9 null mice that had increased vascular leakage. Furthermore, we observed CCR2-dependent infiltration of myeloid cells after treatment and that Ccr2 null host mice responded better to treatment with doxorubicin or cisplatin. These data show that the microenvironment contributes critically to drug response via regulation of vascular permeability and innate immune cell infiltration. Thus, live imaging can be used to gain insights into drug responses in situ.

HER2 and TOP2A as predictive markers for anthracycline-containing chemotherapy regimens as adjuvant treatment of breast cancer: a meta-analysis of individual patient data

BACKGROUND

Prediction of response to anthracycline-based therapy for breast cancer is challenging. We aimed to assess the value of HER2 and TOP2A as predictive markers of response to anthracycline-based adjuvant therapy in patients with early breast cancer.

METHODS

We did a meta-analysis of individual patient data from five randomised adjuvant trials that compared anthracycline-based regimens with cyclophosphamide, methotrexate, and fluorouracil (CMF) regimens. We assessed the status of HER2 and TOP2A genes with fluorescent in-situ hybridisation. Tumour samples were submitted to an external laboratory for validation. We calculated hazard ratios (HR) to compare event-free survival (EFS) and overall survival in patients receiving anthracycline-based treatment with those receiving CMF in two HER2 cohorts (HER2 amplified and non-amplified tumours) and in three TOP2A cohorts (normal, amplified, and deleted tumours).

FINDINGS

We analysed data for 3452 patients for HER2 and 3102 patients for TOP2A. For EFS, HRs were 0·89 (95% CI 0·79-1·01) for HER2 non-amplified patients and 0·71 (0·58-0·86) for HER2-amplified patients (p(interaction)=0·0485); for overall survival, HRs were 0·91 (95% CI 0·79-1·05) for HER2 non-amplified patients and 0·73 (0·59-0·89) for HER2-amplified patients (p(interaction)=0·0718). In analysis of TOP2A status, HRs for EFS were 0·88 (0·78-1·00) for normal, 0·63 (0·46-0·87) for deleted, and 0·62 (0·43-0·90) for amplified (p(interaction)=0·0513); HRs for overall survival were 0·89 (0·78-1·03) for normal, 0·68 (0·49-0·95) for deleted, and 0·67 (0·46-0·98) for amplified (p(interaction)=0·1608). When patients with TOP2A-deleted and TOP2A-amplified tumours were grouped together (altered cohort) and compared with data from patients with normal TOP2A tumours, HRs for EFS were 0·64 (0·50-0·81) for altered and 0·88 (0·78-1·00) for normal (p(interaction)=0·0183); HRs for overall survival were 0·67 (0·52-0·86) for altered and 0·89 (0·78-1·03) for normal (p(interaction)=0·0455).

INTERPRETATION

Although HER2 amplification and combined TOP2A amplification and deletion may have some value in the prediction of responsiveness to anthracycline-based chemotherapy, our findings do not support the use of anthracyclines only in patients with HER2-amplified or TOP2A-aberrated tumours.

FUNDING

Associazione Italiana Ricerca Cancro, Academy of Finland, Belgian Federation Against Cancer, Cancer Research UK, Les Amis de l'Institut Bordet, Scottish Breast Cancer Trials Group, NCIC Clinical Trials Group, Canadian Cancer Society Research Institute, Danish Council for Strategic Research, Pharmacia-Upjohn (now Pfizer), and Abbott Laboratories.

Topoisomerase II alpha protein and responsiveness of breast cancer to adjuvant chemotherapy with CEF compared to CMF in the NCIC CTG randomized MA.5 adjuvant trial

Overexpression of topoisomerase II protein (topo 2α) is postulated to be more closely associated with responsiveness to anthracycline-containing chemotherapy than human epidermal growth factor receptor type 2 (HER2) gene amplification or alterations in the topoisomerase II alpha gene (TOP2A). The authors used tissue microarrays from 477 of 710 premenopausal women with node-positive breast cancer randomized to CEF or CMF adjuvant chemotherapy in the NCIC Clinical Trials Group Mammary 5 (MA.5) trial. No significant interaction was found between treatment and continuous topo 2α level in either relapse-free (RFS) or overall survival (OS). In 136 patients (28.5%) whose tumors showed topo 2α overexpression by immunohistochemistry based on a cut-off of 13%, CEF was superior to CMF for RFS (adjusted HR 0.45; 95% CI 0.25-0.82; P = 0.009) and OS (adjusted HR 0.50; 95% CI 0.26-0.96; P = 0.04). When tumors lacked topo 2α overexpression, CEF was not superior for RFS (adjusted HR 0.88; 95% CI 0.64-1.22; P = 0.46) or OS (adjusted HR 0.95; 95% CI 0.66-1.38; P = 0.80). Interaction between topo 2α and treatment was borderline significant for RFS (P = 0.04) and OS (P = 0.05) and not substantially more significant than between TOP2A gene alteration (P (interaction) = 0.09 for RFS and 0.02 for OS) or HER2 overexpression (P (interaction) = 0.002 for RFS and 0.009 for OS). Topo 2α protein overexpression based on the cut-off identified in this study, TOP2A gene alterations and HER2 protein overexpression were each associated with responsiveness to anthracycline-containing chemotherapy. The topo 2α protein analysis was exploratory and will require further validation.

[Predictive factors of response to anthracyclines neoadjuvant chemotherapy in breast cancer]

OBJECTIVES

Anthracyclines chemotherapy remains primordial and impossible to circumvent in the treatment of breast cancer, in the adjuvant, metastatic and neoadjuvant setting. But some breast invasive tumors are resistant to anthracyclines. The neoadjuvant model is ideal to test the chemosensibility by selecting the well-responder patients and identifying the predictive factors of this response.

PATIENTS AND METHODS

We report a retrospective study of 126 patients treated at our institute during 2 years (January 2003-December 2004) for a breast cancer with primary chemotherapy. All the patients received anthracyclines according to protocol AC60 (doxorubicine plus cyclophosphamide).

RESULTS

The clinical objective response rate (RO) was 67 % with a complete clinical response (RC) of 11 %. We found a pathological complete response (pCR) in seven patients (5,6 %) of the 126 cases. The statistical study identifies only two clinical factors as predictive of RC and pCR: tumoral size T2-T3 and clinical nodal status N0-N1, while the SBR grading and the hormonal receptors were not correlated.

DISCUSSION AND CONCLUSION

Some clinical and histological factors are recognized as predictive for the benefit of anthracyclines neoadjuvant chemotherapy, and correlated to the pCR; we discuss our results through those of the literature, by exposing the current data.

Tumor-initiating cells of HER2-positive carcinoma cell lines express the highest oncoprotein levels and are sensitive to trastuzumab

PURPOSE

The existence of tumor-initiating cells in breast cancer has profound implications for cancer therapy. In this study, we investigated the sensitivity of tumor-initiating cells isolated from human epidermal growth factor receptor type 2 (HER2)-overexpressing carcinoma cell lines to trastuzumab, a compound used for the targeted therapy of breast cancer.

EXPERIMENTAL DESIGN

Spheres were analyzed by indirect immunofluorescence for HER2 cell surface expression and by real-time PCR for HER2 mRNA expression in the presence or absence of the Notch1 signaling inhibitor (GSI) or Notch1 small interfering RNA. Xenografts of HER2-overexpressing breast tumor cells were treated with trastuzumab or doxorubicin. The sphere-forming efficiency (SFE) and serial transplantability of tumors were assessed.

RESULTS

In HER2-overexpressing carcinoma cell lines, cells with tumor-initiating cell properties presented increased HER2 levels compared with the bulk cell population without modification in HER2 gene amplification. HER2 levels were controlled by Notch1 signaling, as shown by the reduction of HER2 cell surface expression and lower SFE following gamma-secretase inhibition or Notch1 specific silencing. We also show that trastuzumab was able to effectively target tumor-initiating cells of HER2-positive carcinoma cell lines, as indicated by the significant decrease in SFE and the loss of serial transplantability, following treatment of HER2-overexpressing xenotransplants.

CONCLUSIONS

Here, we provide evidence for the therapeutic efficacy of trastuzumab in debulking and in targeting tumor-initiating cells of HER2-overexpressing tumors. We also propose that Notch signaling regulates HER2 expression, thereby representing a critical survival pathway of tumor-initiating cells.

Human epidermal growth factor receptor 2 status correlates with lymph node involvement in patients with estrogen receptor (ER) negative, but with grade in those with ER-positive early-stage breast cancer suitable for cytotoxic chemotherapy

PURPOSE

Human epidermal growth factor receptor 2 (HER-2) expression is associated with increased risk of high-grade disease, nodal metastasis, and absence of estrogen receptors (ERs) in early breast cancer. We tested interactions between ER and HER-2 to determine if they may modulate breast cancer nodal metastasis and proliferation.

PATIENTS AND METHODS

Tumors from the Cancer Research UK Taxotere as Adjuvant Chemotherapy phase III trial were tested for HER-2 using current diagnostic procedures. ER status, progesterone status, clinicopathologic characteristics, and patient age were included in a logistic regression analysis to identify associations with HER-2 status (positive v negative).

RESULTS

A total of 841 (23.6%) of 3,565 samples were HER-2 positive (3+ by immunohistochemistry or positive by fluorescent in situ hybridization). ER-negative tumors were more likely to be HER-2 positive than were ER-positive tumors (odds ratio [OR] = 1.87, ER negative v ER positive; P < .001). For ER-positive tumors, risk of HER-2 positivity increased by grade (OR = 7.6, grade 3 v grade 1; P < .001) but not nodal status (OR = 1.3, four or more positive nodes v node negative; P = .08). Conversely, ER negative node-positive tumors were markedly more frequently HER-2 positive than node-negative cases (OR = 3.05, four or more positive nodes v node negative; P < .001) but independent of grade (OR = 0.82, grade 3 v grade 1; P = .76).

CONCLUSION

In early breast cancer patients selected for cytotoxic chemotherapy, we identified significant interactions between HER-2 and ER expression that correlate with tumor pathology. In ER-positive breast cancers, HER-2 expression correlates with grade, not nodal metastasis. In ER-negative breast cancers, HER-2 expression correlates with increased nodal positivity, not grade. ER and HER-2 expression may modify tumor pathology via ER/HER-2-mediated cross talk.

Solamargine upregulation of Fas, downregulation of HER2, and enhancement of cytotoxicity using epirubicin in NSCLC cells

Nonsmall-cell lung cancer (NSCLC) is not generally a chemosensitive tumor, and the mechanism of resistance to the relevant anticancer drugs has not been fully elucidated. Solamargine (SM), the major steroidal glycoalkaloids extracted from the Chinese herb Solanum, inhibits the growth of human tumor cells. We have previously demonstrated that SM regulates tumor necrosis factor receptors (TNFRs)- and mitochondria-mediated pathways and sensitizes NSCLC cells to initiate apoptosis. Interestingly, this investigation reveals that SM up-regulated Fas expression and down-regulated the expression of HER2, whose overexpression is associated with resistance to drugs, and promotes chemotherapy-induced apoptosis in NSCLC A549 and H441 cells. After treatment with SM, the expression of HER2 mRNA was correlated with the expression of topoisomerase IIalpha (TOP2A) mRNA. The combinatory use of low concentrations of SM with low-toxic topoisomerase II inhibitor epirubicin accelerated apoptotic cell death. Therefore, the downregulation of the HER2 and TOP2A expression by SM with epirubicin may partially explain the SM and epirubicin cytotoxicity synergy effect in NSCLC. Results of this study suggest that SM induces Fas and TNFR-induced NSCLC cell apoptosis and reduces HER2 expression. These findings provide the synergistic therapeutic interaction between SM and epirubicin, suggesting that such combinations may be effectively exploited in future human cancer clinical trials.

Regulation of breast cancer response to chemotherapy by fibulin-1

Doxorubicin treatment was found to augment the expression of the extracellular matrix (ECM) protein fibulin-1 in cultured human breast cancer cell lines and in MDA-MB-361 tumors grown in athymic mice. Doxorubicin was also found to augment tumor expression of the fibulin-1-binding proteins fibronectin and laminin-1. Growth of breast cancer cell lines on Matrigel, an ECM extract containing fibulin-1 and laminin-1, resulted in lower levels of doxorubicin-induced apoptosis as compared with controls. Moreover, tumors formed by injection of athymic mice with MDA-MB-361 cells mixed with Matrigel were significantly more doxorubicin resistant and displayed lower levels of apoptosis compared with those that formed in the absence of Matrigel. Monoclonal antibodies against fibulin-1 reversed Matrigel-dependent doxorubicin resistance. Furthermore, small interfering RNA-mediated suppression of fibulin-1 expression in breast cancer cells resulted in a 10-fold increase in doxorubicin sensitivity as compared with control cells. Together, these findings point to a role for fibulin-1 in breast cancer chemoresistance.

Different criteria for HER2 positivity by IHC can be applied in post-chemotherapy specimens in determining HER2 as a prognosticator in locally advanced breast cancer

PURPOSE

We evaluated the clinical significance of HER2 in post-chemotherapy specimens after surgery in locally advanced breast cancer (LABC).

METHODS

Thirty-four patients with LABC were treated with neoadjuvant chemotherapy, surgery, adjuvant chemotherapy, and radiotherapy. The HER2 status was determined using both immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) in the paraffin-embedded surgical specimens after neoadjuvant chemotherapy.

RESULTS

The positive rate of HER2 was 41.2% and 32.4% by IHC and FISH, respectively. As the gene copy number of HER2 detected by FISH increased, the staining intensity by IHC increased with positive correlation (adjusted r (2) = 0.743; P < 0.001). According to the cutoff values of IHC score 2+ and 3+ as the positivity criteria, the concordance rates of IHC and FISH were 91.2% (31/34) and 88.2% (30/34), respectively. With the positivity criteria of IHC score > or =2+, the locoregional recurrence-free survival was better in the HER2-negative patients (P = 0.04). Trends were also found for the prolonged distant recurrence-free, disease-free, and overall survivals in the HER2-negative patients by IHC (2+). Trends for poor clinical response (P = 0.06) and more axillary nodes involvement (P = 0.08) were noted in the HER2-positive group by IHC (2+). In post-chemotherapy specimens, the positive HER2 status by IHC staining score > or = 2+ predicted higher recurrence in LABC.

CONCLUSION

This suggests that different criteria for the HER2 positivity by IHC can be applied in post-chemotherapy specimens compared with that from pre-chemotherapy biopsies.

[Primary systemic therapy in breast cancer: clinical and molecular factors predictors of outcome and response]

PST (primary systemic therapy) represents the standard treatment of care for patients with LABC (locally advanced breast cancer). There is also an emerging role of PST in the treatment of operable breast cancer. In both situations, clinical and pathological responses, in particular when complete, are good predictors of outcome. Identifying the factors predicting response to PST would help clinicians of selecting the most appropriate treatment. There is thus a need for clinical and molecular factors predictive of response. Unfortunately, none of the molecular markers identified in breast tumors is recommended for a use in routine, with the exception of ER and HER2 respectively predictors of response to hormone therapy and Herceptin. New technologies like DNA microarrays are likely to provide in a next future surrogate markers of response to PST in Breast Cancer.

Evaluation of HER-2/Neu Amplification and Other Biological Markers as Predictors of Response to Neoadjuvant Anthracycline-Based Chemotherapy in Primary Breast Cancer

OBJECTIVES

The value of HER-2/neu status as a predictor of response to anthracycline-based chemotherapy is still a matter of debate. We evaluated the contribution of HER-2/neu gene amplification and other biologic markers in predicting response to different doses of neoadjuvant anthracycline-based chemotherapy.

METHODS

Clinical and pathologic records of 115 primary breast cancer patients were reviewed. Forty-eight and 67 patients received high (doxorubicin > or =20 mg/m2/wk; epirubicin > or =30 mg/m2/wk) and moderate-low anthracycline dose intensity regimens, respectively. Pathologic diagnosis, hormonal receptor status (HR), Ki67, and HER-2/neu status were assessed on tumor samples before neoadjuvant chemotherapy. HER-2/neu was determined by fluorescence in situ hybridization (FISH).

RESULTS

HER-2/neu amplification was observed in 29/115 (25%) tumors, 18 from moderate-low-dose and 11 from high-dose group. In the univariate analysis, a high Ki67 index (> or =20%) and positive clinical axillary nodes were predictive of an objective tumor response (P = 0.033 and 0.001, respectively). In the multivariate analysis, Ki67 was the only factor predictive of response (OR = 3.08, 95% CI = 1.1-8.5, P = 0.03). HER-2/neu status was not a factor in predicting objective response to different anthracycline dose intensities. The same finding was observed with regards to HR and Ki67.

CONCLUSIONS

In our series, no significant dose-response relationship was found according to HER-2/neu status.

Proliferative markers as prognostic and predictive tools in early breast cancer: where are we now?

In the last few decades, proliferative markers have been broadly evaluated as prognostic and predictive factors for early stage breast cancer patients. Several papers evaluating one or more markers have been published, often with contradictory results. As a consequence, there is still uncertainty about the role of these proliferative markers. The present paper critically reviews the current knowledge about the following markers: thymidine labeling index, S phase fraction/flow cytometry, Ki 67, thymidine kinase (TK), cyclins E, cyclin D, the cyclin inhibitors p27 and p21, and topoisomerase IIalpha. For each marker, the prognostic and predictive role was separately analyzed. Only papers published in English in peer-reviewed journals before June 2004 that include at least 100 evaluable patients were selected. In addition, the prognostic and predictive role of the proliferative markers had to be assessed through multivariate analyses. One hundred and thirty-two papers fulfilled these criteria and 159 516 patients were analyzed. Unfortunately, several methodological problems in the research to date prevent us from including any one of these proliferative markers among the standard prognostic and predictive factors. Early incorporation of translational research and new technologies with clinical trials are needed to prospectively validate biological markers and allow their use in clinical practice.

HER-2/neu expression as a predictor of response to neoadjuvant docetaxel in patients with operable breast carcinoma

BACKGROUND

The use of biologic markers to predict response to neoadjuvant chemotherapy may permit tailoring regimens to achieve maximal tumor response. Taxanes have demonstrated excellent activity in breast carcinoma; however, tumor-specific factors that predict clinical response have not been characterized thoroughly.

METHODS

The authors performed a historic review evaluating the association of tumor prognostic factors and response to neoadjuvant cyclophosphamide and doxorubicin (AC) with or without docetaxel (D) (AC vs. AC+D) in 121 women who previously were enrolled in a Phase III, randomized, clinical trial. Using pretreatment biopsy materials, immunohistochemical studies were performed for estrogen receptor (ER), progesterone receptor (PR), HER-2/neu, p53, and Ki-67. Outcome variables were pathologic complete response (pCR) and positive clinical response (cPOS), which was defined as a >/= 50% regression in clinical tumor size prior to surgery.

RESULTS

In a multivariate analysis that controlled for tumor size and lymph node status, improved cPOS rates were observed with the addition of docetaxel in women with HER-2/neu-negative tumors (81% vs. 51%; P < 0.05), yielding an adjusted odds ratio of 3.5 (95% confidence interval, 1.2-13.0) in favor of docetaxel. Women who had HER-2/neu-negative tumors appeared to have a lower response rate with AC alone compared with women who had HER-2/neu-positive tumors (51% vs. 75%; P = 0.06), but response rates were matched when docetaxel was added (81% vs. 78%; P = 0.99). ER, PR, p53, and Ki-67 results were not associated significantly with response rates.

CONCLUSIONS

HER-2/neu status may predict improved clinical response rates from the addition of docetaxel to anthracycline-based neoadjuvant chemotherapy. Docetaxel may "rescue" the response in women who have HER-2/neu-negative tumors to match that observed in women who have HER-2/neu-positive tumors treated with AC alone.

Randomized phase II trial of the anti-angiogenic potential of doxorubicin and docetaxel; primary chemotherapy as Biomarker Discovery Laboratory

PURPOSE

Primary chemotherapy provides an ideal opportunity to correlate potential non-invasive surrogate markers of angiogenesis with tumor microvessel density (MVD) and response.

PATIENTS AND METHODS

Patients with newly diagnosed stages II or III breast cancer were treated with sequential doxorubicin 75 mg/M2 q2 wks x 3 and docetaxel 40 mg/M2 weekly x 6; treatment order was randomly assigned. Potential serologic and imaging markers of angiogenesis were obtained pre-treatment, at crossover and completion of chemotherapy. Non-invasive biomarkers were correlated with MVD and pathologic response.

RESULTS

From June 1999 to October 2002, 70 patients were entered. Median pretreatment tumor diameter was 6.0 cm with clinically involved axillary nodes in 33 (47%) patients; 20% had inflammatory disease. Clinical response rate was 91%, including 46% clinical complete responses. Pathologic complete response (pCR) was confirmed in 9 (12.8%) patients. Baseline MVD did not correlate with clinical or pathologic response. Serologic markers were obtained in all patients; basic fibroblast growth factor (bFGF) was lower at baseline and increased during treatment in patients with a pCR but did not correlate with MVD. Color Doppler ultrasound (CDUS) was completed in 47 patients; no parameter reliably correlated with MVD or response. Positron emission tomography (PET) with [F-18]-fluoro-deoxyglucose, [O-15]-water and [C-11]-carbon monoxide were completed in 19 patients; uptake of all tracers decreased during treatment in virtually all patients.

CONCLUSION

Sequential doxorubicin and docetaxel is generally well tolerated and highly active. Serum angiogenic factors and imaging parameters frequently varied throughout treatment but did not correlate with MVD or consistently predict response.

Overview of monoclonal antibodies in cancer therapy: present and promise

After 30 years of development, therapy with monoclonal antibodies has started to realize its promise. Clinical use is most widespread in the field of oncology, where half of the agents approved for routine clinical use are employed and a large number of molecules are currently undergoing clinical trials. In the past 2 years alone, three new compounds-the radiolabeled antibody (131)I-tositumomab and two antibodies targeting growth factor receptors (bevacizumab and cetuximab)-have received FDA approval for indications in oncology. This review summarizes the development of this exciting treatment modality over the last three decades, examines the outcome of treatment with these new antibodies and others available for routine clinical use (i.e. rituximab, trastuzumab, alemtuzumab, gemtuzumab ozogamicin, (90)Y-ibritumomab tiuxetan) in standard indications and in experimental settings, and gives a brief outlook on possible future developments.

The anthracycline antibiotics: antitumor drugs that alter chromatin structure

Anthracycline antibiotics are an important group of antitumor drugs widely used in cancer chemotherapy. However, despite the increasing interest in these chemotherapeutic agents, their mechanism of action is not yet completely understood. Here, we review what is currently known about the molecular mechanisms involved with special emphasis on the interaction of these drugs with chromatin and its constitutive components: DNA and histones. The evidence suggests that one very important component of the activity of these drugs is the result of these manifold interactions that lead to a chromatin unfolding and aggregation. This chromatin structural disruption is likely to interfere with the metabolic processes of DNA (replication and transcription) and it may play an important role in the apoptosis undergone by the cells upon treatment with these drugs.

Topoisomerase-IIα expression as a predictive marker in a population of advanced breast cancer patients randomly treated either with single-agent doxorubicin or single-agent docetaxel

Purpose: The predictive value of topoisomerase-IIα (topo-II) has been evaluated in advanced breast cancer patients randomly treated with single-agent doxorubicin or docetaxel. Experimental design: Primary tumor samples from patients enrolled in a randomized, phase III clinical trial comparing single-agent doxorubicin (75 mg/m2 q3wks) with docetaxel (100 mg/m2 q3wks) were collected and topo-II status was evaluated by immunohistochemistry (clone KiS1). Results: Topo-II status was evaluated in 108 samples, 55 (51%) in the doxorubicin arm and 53 (49%) in the docetaxel arm. An increment of 10% in cells expressing topo-II is associated with a statistically significant odds ratio (OR; 95% confidence interval) of 1.09 (1.03–1.15; P = 0.002) for overall response to doxorubicin versus 1.002 (0.94–1.07; P = 0.95) in the docetaxel arm. With increasing topo-II, the favorable OR for overall response to docetaxel compared with doxorubicin decreases to become not significant in patients with topo-II tumor content &gt;10%. In a multivariate analysis, (a) HER-2 status seems positively correlated with overall response to chemotherapy (OR, 2.34; 95% confidence interval, 0.87–6.27; P = 0.09). (b) Overall response to doxorubicin is significantly lower than overall response to docetaxel (OR, 0.17; 95% confidence interval, 0.04–0.64; P = 0.009) but with a significant interaction term for doxorubicin-treated patients with topo-II tumor content &gt;10% (OR, 8.31; 95% confidence interval, 1.86–37.03; P = 0.05). Conclusions: (a) Topo-II overexpression confers a higher probability of response in the doxorubicin arm only. (b) Despite being a small retrospective study, this study is in line with previously reported studies and the hypotheses raised are now being tested in a prospective neoadjuvant trial.

Power Doppler vascularity index for predicting the response of neoadjuvant chemotherapy in cervical carcinoma

BACKGROUND

To evaluate whether the power Doppler vascularity index (PDVI) can predict the response to neoadjuvant chemotherapy (NACT) in cervical carcinoma.

METHODS

Twenty-five women with bulky early stage cervical carcinoma treated by NACT followed by surgery were enrolled. Their response to NACT was evaluated. Clinical characteristics and pathologic data were recorded. Transvaginal power Doppler was performed before, during and after NACT. PDVI was detected using power Doppler and a quantitative image processing system. Factors that can potentially correlate with the response to NACT were analyzed.

RESULTS

Twelve (48%) patients showed a response (responders) to NACT and 13 (52%) were unchanged or had progressive disease (nonresponders) after NACT. Higher PDVI values were noted in tumors with lymphovascular emboli and pelvic lymph node metastasis both before and after NACT. The mean values of the PDVI of the nonresponders before (19.27 +/- 6.01 vs. 12.28 +/- 7.06, p = 0.014), during (20.2 +/- 1.5 vs. 12.9 +/- 2.1, p = 0.009) and after NACT (18.1 +/- 6.0 vs. 9.3 +/- 5.4, p = 0.001) were significantly higher than those of the responders. When the cutoff point for predicting nonresponders to NACT was set at a PDVI value of 15%, the sensitivity was 92.3% and the specificity 66.7%.

CONCLUSIONS

The power Doppler vascularity index can predict the response to neoadjuvant chemotherapy in cervical cancer, and might be useful for the evaluation of response to chemotherapy in cancer patients in the future.

Biologic and therapeutic role of HER2 in cancer

Overexpression of the human epidermal growth factor-2 (HER2) oncogene in human breast carcinomas has been associated with a more aggressive course of disease. The reason for this association is still unclear, although it has been suggested to rest in increased proliferation, vessel formation, and/or invasiveness. Alternatively, prognosis may not be directly related to the presence of the oncoprotein on the cell membrane, but instead to the breast carcinoma subset identified by HER2 overexpression and characterized by a peculiar gene expression profile. HER2 has also been associated with sensitivity to anthracyclins and resistance to endocrine therapy, suggesting that tyrosine kinase receptor and hormone receptor pathways represent two major proliferation pathways exclusively active in breast carcinomas, one sensitive to chemotherapeutic drugs and the other to antiestrogens. HER2 currently represents one of the most appropriate targets for specific therapy. Indeed, trastuzumab, a monoclonal antibody directed against the extracellular domain of HER2, is therapeutically active in HER2-positive breast carcinomas. However, a consistent number of HER2-positive tumors is not responsive to HER2-driven therapy, indicating the need for a better understanding of the mechanism of action of this new biological drug in vivo. While preclinical studies suggest antibody-dependent cell cytotoxicity as the major mechanism, determination of NK activity at the time of treatment remains mandatory, especially in patients treated with immunosuppressive drugs. The efficacy of prophylactic vaccination has been fully demonstrated in preclinical models, whereas ongoing studies of active immunotherapy using a variety of vaccination regimens against HER2 in tumor-bearing mice and patients have met with only moderate success.