The therapeutic effect of anti-HER2/neu antibody depends on both innate and adaptive immunity

The biology of personalized cancer medicine: facing individual complexities underlying hallmark capabilities

It is a time of great promise and expectation for the applications of knowledge about mechanisms of cancer toward more effective and enduring therapies for human disease. Conceptualizations such as the hallmarks of cancer are providing an organizing principle with which to distill and rationalize the abject complexities of cancer phenotypes and genotypes across the spectrum of the human disease. A countervailing reality, however, involves the variable and often transitory responses to most mechanism-based targeted therapies, returning full circle to the complexity, arguing that the unique biology and genetics of a patient's tumor will in the future necessarily need to be incorporated into the decisions about optimal treatment strategies, the frontier of personalized cancer medicine. This perspective highlights considerations, metrics, and methods that may prove instrumental in charting the landscape of evaluating individual tumors so to better inform diagnosis, prognosis, and therapy. Integral to the consideration is remarkable heterogeneity and variability, evidently embedded in cancer cells, but likely also in the cell types composing the supportive and interactive stroma of the tumor microenvironment (e.g., leukocytes and fibroblasts), whose diversity in form, regulation, function, and abundance may prove to rival that of the cancer cells themselves. By comprehensively interrogating both parenchyma and stroma of patients' cancers with a suite of parametric tools, the promise of mechanism-based therapy may truly be realized.

Intracellular Tumor-Associated Antigens Represent Effective Targets for Passive Immunotherapy

Monoclonal antibody (mAb) therapy against tumor antigens expressed on the tumor surface is associated with clinical benefit. However, many tumor antigens are intracellular molecules that generally would not be considered suitable targets for mAb therapy. In this study, we provide evidence challenging this view through an investigation of the efficacy of mAb directed against NY-ESO-1, a widely expressed immunogen in human tumors that is expressed intracellularly rather than on the surface of cells. On their own, NY-ESO-1 mAb could neither augment antigen-specific CD8+ T-cell induction nor cause tumor eradication. To facilitate mAb access to intracellular target molecules, we combined anti-NY-ESO-1 mAb with anticancer drugs to accentuate the release of intracellular NY-ESO-1 from dying tumor cells. Strikingly, combination therapy induced a strong antitumor effect that was accompanied by the development of NY-ESO-1–specific effector/memory CD8+ T cells that were not elicited by single treatments alone. The combinatorial effect was also associated with upregulation of maturation markers on dendritic cells, consistent with the organization of an effective antitumor T-cell response. Administration of Fc-depleted F(ab) mAb or combination treatment in Fcγ receptor–deficient host mice abolished the therapeutic effect. Together, our findings show that intracellular tumor antigens can be captured by mAbs and engaged in an efficient induction of CD8+ T-cell responses, greatly expanding the possible use of mAb for passive cancer immunotherapy. Cancer Res; 72(7); 1672–82. ©2012 AACR.

Combining immunotherapy and targeted therapies in cancer treatment

During the past two decades, the paradigm for cancer treatment has evolved from relatively nonspecific cytotoxic agents to selective, mechanism-based therapeutics. Cancer chemotherapies were initially identified through screens for compounds that killed rapidly dividing cells. These drugs remain the backbone of current treatment, but they are limited by a narrow therapeutic index, significant toxicities and frequently acquired resistance. More recently, an improved understanding of cancer pathogenesis has given rise to new treatment options, including targeted agents and cancer immunotherapy. Targeted approaches aim to inhibit molecular pathways that are crucial for tumour growth and maintenance; whereas, immunotherapy endeavours to stimulate a host immune response that effectuates long-lived tumour destruction. Targeted therapies and cytotoxic agents also modulate immune responses, which raises the possibility that these treatment strategies might be effectively combined with immunotherapy to improve clinical outcomes.

A vaccine targeting angiomotin induces an antibody response which alters tumor vessel permeability and hampers the growth of established tumors

Angiomotin (Amot) is one of several identified angiostatin receptors expressed by the endothelia of angiogenic tissues. We have shown that a DNA vaccine targeting Amot overcome immune tolerance and induce an antibody response that hampers the progression of incipient tumors. Following our observation of increased Amot expression on tumor endothelia concomitant with the progression from pre-neoplastic lesions to full-fledged carcinoma, we evaluated the effect of anti-Amot vaccination on clinically evident tumors. Electroporation of plasmid coding for the human Amot (pAmot) significantly delayed the progression both of autochthonous tumors in cancer prone BALB-neuT and PyMT genetically engineered mice and transplantable TUBO tumor in wild-type BALB/c mice. The intensity of the inhibition directly correlated with the titer of anti-Amot antibodies induced by the vaccine. Tumor inhibition was associated with an increase of vessels diameter with the formation of lacunar spaces, increase in vessel permeability, massive tumor perivascular necrosis and an effective epitope spreading that induces an immune response against other tumor associated antigens. Greater tumor vessel permeability also markedly enhances the antitumor effect of doxorubicin. These data provide a rationale for the development of novel anticancer treatments based on anti-Amot vaccination in conjunction with chemotherapy regimens.

The immune contexture in human tumours: impact on clinical outcome

Tumours grow within an intricate network of epithelial cells, vascular and lymphatic vessels, cytokines and chemokines, and infiltrating immune cells. Different types of infiltrating immune cells have different effects on tumour progression, which can vary according to cancer type. In this Opinion article we discuss how the context-specific nature of infiltrating immune cells can affect the prognosis of patients.

Using monoclonal antibodies to stimulate antitumor cellular immunity

Monoclonal antibodies (mAbs) have an established role in current cancer therapy with seven approved for the treatment of a wide variety of tumors. The approved mAbs directly target tumor cells; however, it is becoming increasingly clear that as well as their direct effects, these mAbs can present antigens to the immune system. This stimulates long-lasting T-cell immunity, which may correlate with long-term survival. A more direct approach is to use mAbs to target antigens directly to antigen-presenting cells. One approach, ImmunoBody, which has just entered the clinic, stimulates antitumor immunity using mAbs genetically engineered to express tumor-specific T-cell epitopes. T cells not only respond via their T-cell receptors recognizing T-cell epitopes presented on MHC but are also influenced by stimulation of a wide variety of costimulatory molecules. mAbs targeting these molecules can also influence antitumor immunity. The main protagonist in this class of mAbs is ipilimumab, which has recently been shown to improve survival at 2 years in 23% of advanced melanoma patients. Combinations of mAbs targeting tumor antigens to activated antigen-presenting cells and mAbs targeting costimulatory receptors may provide effective therapy for a broad range of tumors.

HER2-overexpressing breast cancer: time for the cure with less chemotherapy?

PURPOSE OF REVIEW

There have been recent new developments in the treatment of breast cancer that over-expresses HER2 (ERRB2/HER2 positive) and the mechanistic understanding of trastuzumab response. We review these findings and reflect on how they may influence the next generation of clinical trials in this breast cancer subtype.

RECENT FINDINGS

Two recent trials in the neoadjuvant setting report that treatment with dual anti-HER2 agents was superior, in terms of rates of pathological complete response, to trastuzumab alone. Recent data also highlight that HER2 positive disease is biologically different according to estrogen receptor status and for long lasting clinical remissions, anti-HER2 therapy also seems to require an effective adaptive immune response.

SUMMARY

We are currently in a very exciting era for therapeutic approaches in HER2 positive disease. Recent data suggest that intensive chemotherapy regimens may not be required for some women if we can determine the most potent combinations of signal inhibitors. We also propose that different clinical trials may need to be designed for HER2 positive breast cancer according to estrogen receptor status and consider incorporating immunotherapeutic approaches.

Mechanisms of Trastuzumab resistance in ErbB2-driven breast cancer and newer opportunities to overcome therapy resistance

The Human Epidermal Growth Factor Receptor 2 (Her2, ErbB2 or Neu) is overexpressed in about 20 – 25% of breast cancers and is causally linked to oncogenesis, providing opportunities for targeted therapy. Trastuzumab (Herceptin^™, Genentech Inc, San Francisco, CA), a humanized monoclonal antibody against ErbB2, is a successful example of this concept and has vastly improved the response to treatment and overall survival in a majority of ErbB2+ breast cancer patients. However, lack of response in some patients as well as relapse during the course of therapy in others, continue to challenge researchers and clinicians alike towards a better understanding of the fundamental mechanisms of Trastuzumab action and resistance to treatment. The exact in vivo mechanism of action of Trastuzumab remains enigmatic, given its direct effects on the ErbB2 signaling pathway as well as indirect contributions from the immune system, by virtue of the ability of Trastuzumab to elicit Antibody-Dependent Cellular Cytotoxicity. Consequently, multiple mechanisms of resistance have been proposed. We present here a comprehensive review of our current understanding of the mechanisms, both of Trastuzumab action and clinical resistance to Trastuzumab-based therapies. We also review newer strategies (based on ErbB2 receptor biology) that are being explored to overcome resistance to Trastuzumab therapy.

Different mechanisms for resistance to trastuzumab versus lapatinib in HER2-positive breast cancers--role of estrogen receptor and HER2 reactivation

INTRODUCTION

The human epidermal growth factor receptor 2 (HER2)-targeted therapies trastuzumab (T) and lapatinib (L) show high efficacy in patients with HER2-positive breast cancer, but resistance is prevalent. Here we investigate resistance mechanisms to each drug alone, or to their combination using a large panel of HER2-positive cell lines made resistant to these drugs.

METHODS

Response to L + T treatment was characterized in a panel of 13 HER2-positive cell lines to identify lines that were de novo resistant. Acquired resistant lines were then established by long-term exposure to increasing drug concentrations. Levels and activity of HER2 and estrogen receptor (ER) pathways were determined by qRT-PCR, immunohistochemistry, and immunoblotting assays. Cell growth, proliferation, and apoptosis in parental cells and resistant derivatives were assessed in response to inhibition of HER or ER pathways, either pharmacologically (L, T, L + T, or fulvestrant) or by using siRNAs. Efficacy of combined endocrine and anti-HER2 therapies was studied in vivo using UACC-812 xenografts.

RESULTS

ER or its downstream products increased in four out of the five ER+/HER2+ lines, and was evident in one of the two intrinsically resistant lines. In UACC-812 and BT474 parental and resistant derivatives, HER2 inhibition by T reactivated HER network activity to promote resistance. T-resistant lines remained sensitive to HER2 inhibition by either L or HER2 siRNA. With more complete HER2 blockade, resistance to L-containing regimens required the activation of a redundant survival pathway, ER, which was up-regulated and promoted survival via various Bcl2 family members. These L- and L + T-resistant lines were responsive to fulvestrant and to ER siRNA. However, after prolonged treatment with L, but not L + T, BT474 cells switched from depending on ER as a survival pathway, to relying again on the HER network (increased HER2, HER3, and receptor ligands) to overcome L's effects. The combination of endocrine and L + T HER2-targeted therapies achieved complete tumor regression and prevented development of resistance in UACC-812 xenografts.

CONCLUSIONS

Combined L + T treatment provides a more complete and stable inhibition of the HER network. With sustained HER2 inhibition, ER functions as a key escape/survival pathway in ER-positive/HER2-positive cells. Complete blockade of the HER network, together with ER inhibition, may provide optimal therapy in selected patients.

Targeting and utilizing primary tumors as live vaccines: changing strategies

Tumor metastases and relapse are the major causes of morbidity and mortality in cancer. Although surgery, chemotherapy and/or radiation therapy can typically control primary tumor growth, metastatic and relapsing tumors are often inaccessible or resistant to these treatments. An adaptive immune response can be generated during these conventional treatments of the primary tumor, and presumably both the primary tumor and secondary metastases share many of the same or similar antigenic characteristics recognized by the immune system. Thus, when established, this response should be able to control metastatic growth and tumor relapse. This review summarizes the mechanisms by which antitumor immune responses are generated, and recent findings supporting the hypothesis that many therapies targeting primary tumors can generate antitumor adaptive immune responses to prevent metastases and tumor relapse.

Modulation of tumor immunity by therapeutic monoclonal antibodies

The surveillance of tumors by the immune system of cancer patients and its impact on disease progression and patient survival have been largely documented over the last years. In parallel, the use of therapeutic monoclonal antibodies (mAbs) in oncology has gained a widespread recognition as it has made it possible to increase patient survival and to ameliorate the quality of life in a number of cancers. However, the clinical responses observed following mAb treatment remain largely heterogeneous and their duration is still highly unpredictable. Recently, the concept that the injection of therapeutic antibodies not only triggers early anti-tumor events such as receptor blockade, cytostasis, apoptosis, complement-dependent cytotoxicity and/or antibody-dependent cytotoxicity but also allows the host immune system to fight tumor cells through the development of a long-lasting adaptive immunity has emerged. In the present review, we will examine the arguments that support this concept by detailing the cellular and molecular events likely to underlie the induction of an efficient anti-tumor adaptive immune response by mAbs. We will also discuss the consequences of this induction on the way therapeutic antibodies can be used and inserted in a more global immunotherapeutic approach aiming at strengthening the adaptive anti-tumor immune response developed by cancer patients.

ISCOMATRIX vaccines mediate CD8+ T-cell cross-priming by a MyD88-dependent signaling pathway

Generating a cytotoxic CD8⁺ T-cell response that can eradicate malignant cells is the primary objective of cancer vaccine strategies. In this study we have characterized the innate and adaptive immune response to the ISCOMATRIX adjuvant, and the ability of vaccine antigens formulated with this adjuvant to promote antitumor immunity. ISCOMATRIX adjuvant led to a rapid innate immune cell response at the injection site, followed by the activation of natural killer and dendritic cells (DC) in regional draining lymph nodes. Strikingly, major histocompatibility complex (MHC) class I cross-presentation by CD8α⁺ and CD8α⁻ DCs was enhanced by up to 100-fold when antigen was formulated with ISCOMATRIX adjuvant. These coordinated features enabled efficient CD8⁺ T-cell cross-priming, which exhibited prophylactic and therapeutic tumoricidal activity. The therapeutic efficacy of an ISCOMATRIX vaccine was further improved when co-administered with an anti-CD40 agonist antibody, suggesting that ISCOMATRIX-based vaccines may combine favorably with other immune modifiers in clinical development to treat cancer. Finally, we identified a requirement for the myeloid differentiation primary response gene 88 (MyD88) adapter protein for both innate and adaptive immune responses to ISCOMATRIX vaccines in vivo. Taken together, our findings support the utility of the ISCOMATRIX adjuvant for use in the development of novel vaccines, particularly those requiring strong CD8⁺ T-cell immune responses, such as therapeutic cancer vaccines.

Effective antibody therapy induces host-protective antitumor immunity that is augmented by TLR4 agonist treatment

Toll-like receptors are potent activators of the innate immune system and generate signals leading to the initiation of the adaptive immune response that can be utilized for therapeutic purposes. We tested the hypothesis that combined treatment with a Toll-like receptor agonist and an antitumor monoclonal antibody is effective and induces host-protective antitumor immunity. C57BL/6 human mutated HER2 (hmHER2) transgenic mice that constitutively express kinase-deficient human HER2 under control of the CMV promoter were established. These mice demonstrate immunological tolerance to D5-HER2, a syngeneic human HER2-expressing melanoma cell line. This human HER2-tolerant model offers the potential to serve as a preclinical model to test both antibody therapy and the immunization potential of human HER2-targeted therapeutics. Here, we show that E6020, a Toll-like receptor-4 (TLR4) agonist effectively boosted the antitumor efficacy of the monoclonal antibody trastuzumab in immunodeficient C57BL/6 SCID mice as well as in C57BL/6 hmHER2 transgenic mice. E6020 and trastuzumab co-treatment resulted in significantly greater inhibition of tumor growth than was observed with either agent individually. Furthermore, mice treated with the combination of trastuzumab and the TLR4 agonist were protected against rechallenge with human HER2-transfected tumor cells in hmHER2 transgenic mouse strains. These findings suggest that combined treatment with trastuzumab and a TLR4 agonist not only promotes direct antitumor effects but also induces a host-protective human HER2-directed adaptive immune response, indicative of a memory response. These data provide an immunological rationale for testing TLR4 agonists in combination with antibody therapy in patients with cancer.

Camouflage and sabotage: tumor escape from the immune system

The field of tumor immunology has made great progress in understanding tumor immune interactions. As a consequence a number of immuno-therapeutic approaches have been successfully introduced into the clinic and a large number of promising therapeutic strategies are investigated in ongoing clinical trials. Evaluation of anti-tumor immunity in such trials as well as in animal models has shown that tumor escape from immune recognition and tumor-mediated suppression of anti-tumor immunity can pose a significant obstacle to successful cancer therapy. Here, we review mechanisms of tumor immune escape and immune-subversion with a focus on the research interests in our laboratory: loss of MHC class I on tumor cells, increased oxidative stress, recruitment of myeloid-derived suppressor cells, and regulatory T cells.

Antibody-dependent cell cytotoxicity synapses form in mice during tumor-specific antibody immunotherapy

Antibody-dependent cell cytotoxicity (ADCC) plays a critical role in monoclonal antibody (mAb)-mediated cancer therapy. ADCC, however, has not been directly shown in vivo but inferred from the requirement for IgG Fc receptors (FcγR) in tumor rejection in mice. Here, we investigated the mechanism of action of a Tn antigen-specific chimeric mAb (Chi-Tn), which binds selectively to a wide variety of carcinomas, but not to normal tissues, in both humans and mice. Chi-Tn mAb showed no direct toxicity against carcinomas cell lines in vitro but induced the rejection of a murine breast tumor in 80% to 100% of immunocompetent mice, when associated with cyclophosphamide. Tumor rejection was abolished in Fc receptors-associated γ chain (FcR-γ)-deficient mice, suggesting a role for ADCC. Indeed, tumor cells formed stable conjugates in vivo with FcR-γ chain-expressing macrophages and neutrophils in Chi-Tn mAb-treated but not in control mAb-treated mice. The contact zone between tumor cells and ADCC effectors accumulated actin, FcγR and phospho-tyrosines. The in vivo formed ADCC synapses were organized in multifocal supra-molecular activation clusters. These results show that in vivo ADCC mediated by macrophages and neutrophils during tumor rejection by Chi-Tn mAb involves a novel type of multifocal immune synapse between effectors of innate immunity and tumor cells.

Novel method for differentiation between Trastuzumab and host adaptive response

Humoral immune response to human epidermal growth factor receptor 2 (HER-2/neu or ErbB-2) has been detected in sera of breast cancer patients and shown to be an appropriate prognostic marker (Taylor et al., 2007). However, since Trastuzumab (Herceptin) is a widely used monoclonal antibody as cancer therapy agent for tumors over-expressing HER-2, there is a need for an efficient way to detect host-generated antibodies against HER-2 without the confounding effect of Herceptin. Here we describe a screening method developed to decipher between host antibodies against HER-2 and that of Herceptin. By producing a series of truncation mutants within the epitope of Herceptin, we were able to inhibit this binding. We demonstrated also that by a three amino acid substitution (PPF→SSS) we were able to abrogate Herceptin binding while generating a highly conserved HER-2 extracellular domain (ECD). By producing a stable cell line that expresses this mutated form of the human HER-2 ECD, we have a source of this protein to probe patient sera. Our method represents a proof of principle that mutated HER-2 which we constructed could be used to distinguish between a host response against HER-2 and the monoclonal antibody Herceptin targeting the same protein.

Resistance to HER2-directed antibodies and tyrosine kinase inhibitors: mechanisms and clinical implications

The antibody trastuzumab and the tyrosine kinase inhibitor lapatinib are approved by the FDA for the treatment of HER2-overexpressing breast cancer. These anti-HER2 drugs are changing the natural history of HER2-overexpressing breast cancer. However, therapeutic resistance to trastuzumab or lapatinib, as either single-agents or in combination with chemotherapy in the metastatic setting, typically occurs within months of starting therapy. Several mechanisms of trastuzumab-resistance have been reported that include signaling from other HER receptors, signaling from receptor tyrosine kinases (RTKs) outside of the HER (ErbB) family, increased phosphatidylinositol 3-kinase signaling, and the presence of truncated forms of HER2. Mechanisms of resistance to lapatinib also point to increased phosphatidylinositol 3-kinase signaling as well as derepression/activation of compensatory survival pathways. In this review, we discuss how these models and mechanisms enhance our understanding of the clinical resistance to HER2-directed therapies.

Anti-ErbB-2 mAb therapy requires type I and II interferons and synergizes with anti-PD-1 or anti-CD137 mAb therapy

Trastuzumab, a monoclonal antibody targeting human epidermal growth factor receptor-2 (HER2/ErbB-2), has become the mainstay of treatment for HER2-positive breast cancer. Nevertheless, its exact mechanism of action has not been fully elucidated. Although several studies suggest that Fc receptor-expressing immune cells are involved in trastuzumab therapy, the relative contribution of lymphocyte-mediated cellular cytotoxicity and antitumor cytokines remains unknown. We report here that anti-ErbB-2 mAb therapy is dependent on the release of type I and type II IFNs but is independent of perforin or FasL. Our study thus challenges the notion that classical antibody-dependent, lymphocyte-mediated cellular cytotoxicity is important for trastuzumab. We demonstrate that anti-ErbB-2 mAb therapy of experimental tumors derived from MMTV-ErbB-2 transgenic mice triggers MyD88-dependent signaling and primes IFN-γ-producing CD8+ T cells. Adoptive cell transfer of purified T cell subsets confirmed the essential role of IFN-γ-producing CD8+ T cells. Notably, anti-ErbB-2 mAb therapy was independent of IL-1R or IL-17Ra signaling. Finally, we investigated whether immunostimulatory approaches with antibodies against programmed death-1 (PD-1) or 41BB (CD137) could be used to capitalize on the immune-mediated effects of trastuzumab. We demonstrate that anti-PD-1 or anti-CD137 mAb can significantly improve the therapeutic activity of anti-ErbB-2 mAb in immunocompetent mice.

Combination of epitope-optimized DNA vaccination and passive infusion of monoclonal antibody against HER2/neu leads to breast tumor regression in mice

HER2/neu is an oncogene amplified and over-expressed in 20-30% of breast adenocarcinomas. Treatment with the humanized monoclonal antibody trastuzumab has shown efficacy in combination with cytotoxic agents, although resistance occurs over time. Novel approaches are needed to further increase antibody efficacy. In this study, we provide evidence in a mouse breast cancer therapeutic tumor model that the combination of active immunization with a modified HER2/neu DNA vaccine and passive infusion of an anti-HER2/neu monoclonal antibody leads to significant regression of established tumors. Our data indicate that combination therapy with a HER2/neu DNA vaccine and trastuzumab may have clinical activity in breast cancer patients.

Low dosages: new chemotherapeutic weapons on the battlefield of immune-related disease

Chemotherapeutic drugs eliminate tumor cells at relatively high doses and are considered weapons against tumors in clinics and hospitals. However, despite their ability to induce cellular apoptosis, chemotherapeutic drugs should probably be regarded more as a class of cell regulators than cell killers, if the dosage used and the fact that their targets are involved in basic molecular events are considered. Unfortunately, the regulatory properties of chemotherapeutic drugs are usually hidden or masked by the massive cell death induced by high doses. Recent evidence has begun to suggest that low dosages of chemotherapeutic drugs might profoundly regulate various intracellular aspects of normal cells, especially immune cells. Here, we discuss the immune regulatory roles of three kinds of chemotherapeutic drugs under low-dose conditions and propose low dosages as potential new chemotherapeutic weapons on the battlefield of immune-related disease.

Anti-IL-23 monoclonal antibody synergizes in combination with targeted therapies or IL-2 to suppress tumor growth and metastases

Immunosuppressive barricades erected by tumors during the evolution of immune escape represent a major obstacle to many potentially effective cancer therapies and vaccines. We have shown that host interleukin (IL)-23 suppresses the innate immune response during carcinogenesis and metastasis, independently of effects on the proinflammatory cytokine IL-17A. Based on these findings, we envisioned that IL-23 neutralization might offer a promising strategy to modulate immunosuppression, particularly in combination with immunostimulatory agents. Here we show that by itself a neutralizing monoclonal antibody (mAb) to IL-23 suppressed early experimental lung metastases in the B16F10 mouse model of melanoma and also modestly inhibited the subcutaneous growth of primary tumors. These antitumor effects were respectively mediated by natural killer cells or CD8(+) T cells. More notably, combinatorial treatments of anti-IL-23 mAb with IL-2 or anti-erbB2 mAb significantly inhibited subcutaneous growth of established mammary carcinomas and suppressed established experimental and spontaneous lung metastases. Overall, our results suggest the potential of anti-human IL-23 mAbs to improve the immunostimulatory effects of IL-2 and trastuzumab in the current management of some advanced human cancers.

Time-resolved fluorescence resonance energy transfer (TR-FRET) to analyze the disruption of EGFR/HER2 dimers: a new method to evaluate the efficiency of targeted therapy using monoclonal antibodies

In oncology, simultaneous inhibition of epidermal growth factor receptor (EGFR) and HER2 by monoclonal antibodies (mAbs) is an efficient therapeutic strategy but the underlying mechanisms are not fully understood. Here, we describe a time-resolved fluorescence resonance energy transfer (TR-FRET) method to quantify EGFR/HER2 heterodimers on cell surface to shed some light on the mechanism of such therapies. First, we tested this antibody-based TR-FRET assay in NIH/3T3 cell lines that express EGFR and/or HER2 and in various tumor cell lines. Then, we used the antibody-based TR-FRET assay to evaluate in vitro the effect of different targeted therapies on EGFR/HER2 heterodimers in the ovarian carcinoma cell line SKOV-3. A simultaneous incubation with Cetuximab (anti-EGFR) and Trastuzumab (anti-HER2) disturbed EGFR/HER2 heterodimers resulting in a 72% reduction. Cetuximab, Trastuzumab or Pertuzumab (anti-HER2) alone induced a 48, 44, or 24% reduction, respectively. In contrast, the tyrosine kinase inhibitors Erlotinib and Lapatinib had very little effect on EGFR/HER2 dimers concentration. In vivo, the combination of Cetuximab and Trastuzumab showed a better therapeutic effect (median survival and percentage of tumor-free mice) than the single mAbs. These results suggest a correlation between the extent of the mAb-induced EGFR/HER2 heterodimer reduction and the efficacy of such mAbs in targeted therapies. In conclusion, quantifying EGFR/HER2 heterodimers using our antibody-based TR-FRET assay may represent a useful method to predict the efficacy and explain the mechanisms of action of therapeutic mAbs, in addition to other commonly used techniques that focus on antibody-dependent cellular cytotoxicity, phosphorylation, and cell proliferation.

2011: the immune hallmarks of cancer

Ten years after the publication of the position paper “The hallmarks of cancer” (Hanahan and Weinberg Cell 100:57–70, 2000), it has become increasingly clear that mutated cells on their way to giving rise to a tumor have also to learn how to thrive in a chronically inflamed microenvironment, evade immune recognition, and suppress immune reactivity. Genetic and molecular definition of these three immune hallmarks of cancer offers the opportunity to learn how to deploy specific countermeasures to reverse the situation in favor of the immune system and, eventually, the patient. This new information could be channeled to address what seem to be the three major hallmarks for the immune control of cancer progression: effective procedures to activate immune reactivity; characterization of not-disposable oncoantigens; and counteraction of immune suppression.

New strategies in HER2-overexpressing breast cancer: many combinations of targeted drugs available

The anti-HER2 drugs trastuzumab and lapatinib are increasingly changing the natural history of early and metastatic HER2-overexpressing breast cancer. Many other agents targeted against the HER2 signaling network are in clinical development, and these are or will soon be combined with the currently approved anti-HER2 therapies. We review herein recent data in support of the early use of combinations of agents targeted to the HER2 network as the most rational approach against this subtype of breast cancer. We propose that the optimal combination or combinations of anti-HER2 agents delivered early in the natural history of HER2+ breast cancer should close to eliminate acquired drug resistance, shorten the duration of therapy, and potentially dispense with the need of concurrent chemotherapy.

Development of metastatic HER2(+) breast cancer is independent of the adaptive immune system

The tumour-modulating effects of the endogenous adaptive immune system are rather paradoxical. Whereas some clinical and experimental observations offer compelling evidence for the existence of immunosurveillance, other studies have revealed promoting effects of the adaptive immune system on primary cancer development and metastatic disease. We examined the functional significance of the adaptive immune system as a regulator of spontaneous HER2(+) breast tumourigenesis and pulmonary metastasis formation, using the MMTV-NeuT mouse model in which mammary carcinogenesis is induced by transgenic expression of the activated HER2/neu oncogene. Although T and B lymphocytes infiltrate human and experimental HER2(+) breast tumours, genetic elimination of the adaptive immune system does not affect development of premalignant hyperplasias or primary breast cancers. In addition, we demonstrate that pulmonary metastasis formation in MMTV-NeuT mice is not dependent on the adaptive immune system. Thus, our findings reveal that spontaneous HER2-driven mammary tumourigenesis and metastasis formation are neither suppressed, nor altered by immunosurveillance mechanisms, nor promoted by the adaptive immune system.

Her 2 in 1

In this issue of Cancer Cell, Park et al. demonstrate that anti-erbB2 antibody primes adaptive immunity for increased tumor clearance and suggest that chemotherapy may in fact interfere with this process.