Monoclonal antibody-based targeted therapy in breast cancer: current status and future directions

The recent development of monoclonal antibodies targeting growth factor receptors in cancer treatment represents a milestone for both researchers and physicians. Advances in the understanding of key molecular pathways for tumour growth and survival have facilitated the development of these targeted therapies, in particular in breast cancer. This review focuses on the three most important recombinant humanised monoclonal antibodies that have shown activity in women with breast cancer: trastuzumab, pertuzumab and bevacizumab. Trastuzumab, an anti-erbB2 (human epidermal growth factor receptor) monoclonal antibody, is currently routinely used in both the metastatic and adjuvant settings for patients with erbB2-positive tumours. Pertuzumab, a monoclonal antibody binding to a different epitope on erbB2 than trastuzumab, is under early clinical evaluation. This drug has been developed for breast cancer patients, whether overexpressing erbB2 or not. Bevacizumab, a monoclonal antibody directed against vascular endothelial growth factor-A, is being evaluated in the metastatic setting for its antiangiogenic properties, and is showing promising results.     

What's so special about [symbol: see text] trastuzumab?

The growth and multiplication of cells are regulated, in part, by polypeptide growth factors that bind to high-affinity receptors typically found on the plasma membrane. One such receptor is human epidermal growth factor receptor 2 (HER2). In around a quarter of all primary breast cancers, cells possess abnormally high numbers of (overexpress) HER2. [symbol: see text] Trastuzumab (pronounced tra-stoo-zoo-mab; Herceptin-Roche), a recombinant humanised mouse monoclonal antibody directed against HER2, is available as a treatment for certain patients with metastatic breast cancer. It is licensed as a first-line treatment in combination with [symbol: see text] paclitaxel for those whose cancer cells overexpress HER2 and for whom an anthracycline is unsuitable, and as a third-line treatment used alone when treatment with (where appropriate) an anthracycline, a taxane and hormonal therapy has failed. The National Institute for Clinical Excellence (NICE) has recommended trastuzumab as a treatment option for metastatic breast cancer in accordance with the licensed indications. What does trastuzumab offer?     

Everolimus: targeted therapy on the horizon for the treatment of breast cancer

The mammalian target of rapamycin (mTOR) is a signaling kinase of the phosphatidylinositol 3-kinase/protein kinase B (also known as Akt) signaling pathway that mediates cell growth and metabolism. Dysregulation of the mTOR pathway creates a favorable environment for the development and progression of many cancers, including breast cancer, and is associated with the development of resistance to endocrine therapy and to the anti-human epidermal growth factor receptor-2 (HER2) monoclonal antibody trastuzumab. Therefore, the addition of mTOR inhibitors to conventional breast cancer therapy has the potential to enhance therapeutic efficacy and/or overcome innate or acquired resistance. Everolimus, an mTOR inhibitor with demonstrated preclinical activity against breast cancer cell lines, has been shown to reverse Akt-induced resistance to hormonal therapy and trastuzumab. Phase I-II clinical trials have demonstrated that everolimus has promising clinical activity in women with HER2-positive, HER2-negative, and estrogen receptor-positive breast cancer when combined with HER2-targeted therapy, cytotoxic chemotherapy, and hormonal therapy, respectively. Everolimus is generally well tolerated; hematologic abnormalities and stomatitis are most common adverse events when this drug is combined with cytotoxic chemotherapy. Based on these promising results, everolimus is currently under evaluation in a series of phase III Breast Cancer Trials of Oral Everolimus (BOLERO) trials of women with HER2-positive and estrogen receptor-positive breast cancer. Results of these trials will help to establish the role of everolimus in the treatment of clinically important breast cancer subtypes.     

New perspectives on anti-HER2/neu therapeutics

HER2/neu and the epidermal growth factor receptor (EGFR) are significantly overexpressed in several cancer cells. Overexpression of these two receptors accounts for progression of many types of cancer: breast, ovarian, skin, pancreas and brain. In recent years, several approaches to disable the receptor complexes have shown promise. Antibody-based therapy, kinase inhibitors and other inhibitors of signaling molecules are the major approaches. Our group developed the concept that an anti-p185HER2/neu monoclonal antibody might represent a therapeutic for cancer and this has culminated in a clinically useful therapeutic, the humanized monoclonal antibody Herceptin (trastuzumab). We have now developed a small-molecule form of an anti-HER2/neu peptidomimetic (AHNP) that exhibit functions comparable to those of the monoclonal antibody Herceptin. This approach may be considered a new paradigm in receptor-specific tumor therapeutics. A brief review of our approach in developing receptor-specific therapeutic agents for HER2/neu-related cancer is presented.     

HER2-positive breast cancer: current and future treatment strategies

In the year 2006, breast cancer was estimated to affect >200,000 American women and cause nearly 56,000 deaths. Furthermore, breast cancer is the most common cancer diagnosed and second most common cause of cancer-related deaths in women. The current treatment armamentarium for breast cancer includes chemotherapy, endocrine therapy and biological therapy. Treatment has become more individualised based on characteristics of the tumour including overexpression of the human epidermal growth factor receptor (HER)-2. Between 20 and 30% of all breast cancers overexpress HER2, which means 40,000 - 60,000 patients will have this type of cancer.Previously, overexpression of HER2 was a negative prognostic and predictive risk factor for survival; however, with the advent of trastuzumab, patients' prognosis is improving in all treatment settings. Much controversy exists in the use of trastuzumab, including (i) the sequence of adjuvant trastuzumab (concurrent with chemotherapy or sequential); (ii) the treatment duration (<1 year, 1 year or 2 years); and (iii) the treatment choice upon disease progression (whether to continue or not with trastuzumab and add another cytotoxic agent). Current trials are ongoing to help answer these questions.Furthermore, there has been interest in predicting which HER2-positive patients would require anthracycline therapy, and which could avoid anthracycline therapy and its toxicities. Novel therapeutics, such as lapatinib, an oral tyrosine kinase inhibitor, which blocks both the epidermal growth factor receptor and HER2 receptor has recently been approved by the US FDA. Whereas pertuzumab, a humanised monoclonal antibody, directed against heterodimerisation of HER2 and HER3 has entered phase II and III clinical trials.     

Revoking the privilege: targeting HER2 in the central nervous system

Pharmacologic agents developed for cancer therapy have traditionally relied on a therapeutic ratio of effects between tumors and normal tissue. Over the past decade, this concept has been refined through the development of agents that are intended to specifically target tumor cells. The epidermal growth factor receptor (EGFR) (ErbB) family of receptor tyrosine kinases is an intensely studied target in many cancer cell types, and several successful therapeutic agents have been developed to block the growth promoting functions of these receptors. However, with their success has come the evolution of novel clinical scenarios by which tumor cells can evade these targeted therapies. Trastuzumab, a monoclonal antibody to Her2/ErbB2 that is used in breast cancer, has been shown to provide a survival benefit for patients whose tumors express this receptor but it does not have activity in the central nervous system because of the blood-brain barrier. In this issue of Molecular Pharmacology, Emanuel et al. (p. 328) report on a tyrosine kinase inhibitor that targets Her2/neu and also crosses the blood-brain barrier. Efforts to improve current strategies of targeting this receptor may lead not only to benefits in the treatment of breast cancer but also to advances in the treatment of other central nervous system malignancies, such as gliomas and medulloblastoma.     

Herceptin: the future in adjuvant breast cancer therapy

New drugs for the treatment of breast cancer are generally introduced into clinical practice in the metastatic setting. However, it is well known that therapeutic response improves when drugs are used earlier in the disease. Therefore, once drugs have shown a major therapeutic impact in the metastatic setting, investigation in the adjuvant setting should be prioritized. Herceptin has shown significant efficacy and an ability to extend survival in human epidermal growth factor receptor-2 (HER2)-positive metastatic breast cancer patients and is well tolerated. Four major randomized, multicenter adjuvant clinical trials of Herceptin in patients with HER2-positive primary breast cancer have been started or are planned. The designs of these trials are described. With a total of over 12 000 patients, these studies should provide the information necessary to confirm the clinical potential of Herceptin as adjuvant therapy. The inclusion of a variety of regimens, including different durations of Herceptin therapy in the Herceptin Adjuvant (HERA) Trial, will allow the optimal therapeutic approach to be identified, and the size and generally pragmatic designs should encourage clinicians to enroll patients. The establishment of the role of Herceptin in the adjuvant setting will offer women with HER2-positive primary breast cancer the chance for improved survival. This is particularly important given that HER2-positive breast cancer patients form a high-risk group with a poor overall prognosis.     

Promising molecular targeted therapies in breast cancer

In recent years, there has been a significant improvement in the understanding of molecular events and critical pathways involved in breast cancer. This has led to the identification of novel targets and development of anticancer therapies referred to as targeted therapy. Targeted therapy has high specificity for the molecules involved in key molecular events that are responsible for cancer phenotype such as cell growth, survival, migration, invasion, metastasis, apoptosis, cell-cycle progression, and angiogenesis. Targeted agents that have been approved for breast cancer include trastuzumab and lapatinib, directed against human epidermal growth factor receptor 2 (HER2) and bevacizumab, directed against vascular endothelial growth factor (VEGF). Several other targeted agents currently under evaluation in preclinical and clinical trials include inhibitors of epidermal growth factor receptor (EGFR), dual EGFR and HER2 inhibitors, VEGF/VEGFR inhibitors, and agents that interfere with crucial signaling pathways such as PI3K/AKT/mTOR and RAS/MEK/ERK; agents against other tyrosine kinases such as Src, insulin-like growth factor (IGF)/IGF-receptor (IGFR); agents that promote apoptosis such as Poly ADP ribose polymerase inhibitors; agents that target invasion and metastasis such as matrix metalloproteinases inhibitors and others. In this review, we highlight the most promising targeted agents and their combination with mainstream chemotherapeutic drugs in clinical trials.     

Growth factor deprivation therapy of hormone insensitive prostate and breast cancers utilizing antisense oligonucleotides

Antisense oligonucleotides (oligos) are artificial sequences of nucleotide bases which may be synthesized complementary to known regions within specific mRNAs. When these constructed oligos interact with protein encoding mRNA they may regulate expression of various growth factors and/or their receptors. Oligos directed against transforming growth factor-alpha (TGF-alpha) and its binding site, the epidermal growth factor receptor (EGFR), were employed: A) in vitro to affect the growth of hormone insensitive human derived PC-3 prostate cancer cells as well as the human derived UACC-893 breast cancer cell line; and B) in vivo to treat tumors established by these cell lines in athymic nude mice. The in vitro results for each oligo, and their combination, produced significant inhibition of both prostate and breast cell lines. In addition, the combination of oligos most efficiently diminished the immunohistochemical expression of both TGF-alpha and EGFR in PC-3 cells. Direct in vivo inoculation of oligos into established PC-3 or UACC-893 tumors in nude mice produced hemorrhagic necrosis within 2-3 days. Such therapy could represent a new tier of therapy for recurrent, hormone insensitive, tumors based upon the concept of growth factor deprivation.     

Efficacy and safety of trastuzumab

The human epidermal growth factor receptor (HER) 2 is overexpressed in ～ 20 – 25% of human breast cancers and is an independent adverse prognostic factor. Targeted therapy directed against this receptor has been developed in the form of a humanised monoclonal antibody, trastuzumab. This antibody has shown activity as a single agent in metastatic breast cancer both prior to chemotherapy and in heavily pretreated patients. A pivotal Phase III trial has demonstrated that its use in combination with an anthracycline or paclitaxel results in a significant improvement in survival, time to progression, and response. This has recently been reinforced by another trial with docetaxel. The HER2 status of a tumour is a critical determinant of response to trastuzumab-based treatment. Those that express HER2 at the highest level on immunohistochemistry (IHC), 3+, derive more benefit from treatment with trastuzumab than those with overexpression at the 2+ level. Benefit correlates best with tumours that are positive on fluorescence in situ hybridisation for HER2, regardless of IHC status. Treatment with trastuzumab is generally well tolerated with a low incidence of adverse events. Some patients may experience fever, chills, dyspnoea and pain, particularly with the first administration. Unexpectedly, cardiac toxicity has developed in some patients treated with trastuzumab, and this has a higher incidence in those treated in combination with an anthracycline. ‘Cross-talk’ between the oestrogen receptor and HER2 pathway has stimulated interest in using trastuzumab in combination with endocrine therapy. Current clinical trials are investigating the role of this agent in the adjuvant setting.     

Efficacy and safety of trastuzumab

The human epidermal growth factor receptor (HER) 2 is overexpressed in approximately 20-25% of human breast cancers and is an independent adverse prognostic factor. Targeted therapy directed against this receptor has been developed in the form of a humanised monoclonal antibody, trastuzumab. This antibody has shown activity as a single agent in metastatic breast cancer both prior to chemotherapy and in heavily pretreated patients. A pivotal Phase III trial has demonstrated that its use in combination with an anthracycline or paclitaxel results in a significant improvement in survival, time to progression, and response. This has recently been reinforced by another trial with docetaxel. The HER2 status of a tumour is a critical determinant of response to trastuzumab-based treatment. Those that express HER2 at the highest level on immunohistochemistry (IHC), 3+, derive more benefit from treatment with trastuzumab than those with overexpression at the 2+ level. Benefit correlates best with tumours that are positive on fluorescence in situ hybridisation for HER2, regardless of IHC status. Treatment with trastuzumab is generally well tolerated with a low incidence of adverse events. Some patients may experience fever, chills, dyspnoea and pain, particularly with the first administration. Unexpectedly, cardiac toxicity has developed in some patients treated with trastuzumab, and this has a higher incidence in those treated in combination with an anthracycline. 'Cross-talk' between the oestrogen receptor and HER2 pathway has stimulated interest in using trastuzumab in combination with endocrine therapy. Current clinical trials are investigating the role of this agent in the adjuvant setting.     

Trastuzumab: a review of its use in the management of HER2-positive metastatic and early-stage breast cancer

Trastuzumab (Herceptin) is a humanised monoclonal antibody used in the treatment of breast cancer that overexpresses human epidermal growth factor receptor 2 (HER2), which is associated with clinically aggressive disease and a poor prognosis. The addition of intravenous trastuzumab to first-line chemotherapy improved the time to disease progression, objective response rate, duration of response, and overall survival in randomised, multicentre trials in women with HER2-positive metastatic breast cancer. As such, trastuzumab has become the standard of care in this setting, despite its high acquisition cost and potential for cardiac events, and is licensed for use in combination with paclitaxel (Europe and the US) or docetaxel (Europe). In addition, trastuzumab monotherapy is approved for use in patients with HER2-positive metastatic breast cancer who have previously received chemotherapy for their metastatic disease. Recent data from large phase III trials with trastuzumab in the adjuvant setting revealed significant improvements in disease-free and overall survival. Thus, trastuzumab is also rapidly becoming a standard component of adjuvant therapy for patients with HER2-positive early-stage breast cancer.     

Simultaneous amplification of HER-2 (ERBB2) and topoisomerase IIalpha (TOP2A) genes--molecular basis for combination chemotherapy in cancer

The HER-2 (also known as ERBB2/ErbB2/c-erbB2/HER-2/neu) oncogene is the most frequently amplified oncogene in breast cancer and is also amplified in other forms of cancer. Beside its important role in tumor induction, growth and progression, HER-2 is also a target for new therapeutic approaches such as Herceptin (trastuzumab), a recombinant antibody designed to block signaling through the HER-2 receptor. In addition to Herceptin, which is in a wide clinical use for HER-2 amplified breast cancer, a number of various HER-2 directed immunological and genetic strategies, either targeting the HER-2 receptor, its signaling pathways or both HER-2 and epidermal growth factor receptor (EGFR) simultaneously, have demonstrated promising pre-clinical activity in HER-2 amplified carcinomas. Moreover, the HER-2 amplicon is known to contain more than 30 genes with altered copy numbers that could be therapeutic targets for chemotherapy. The topoisomerase IIalpha gene, TOP2A, is located adjacent to the HER-2 oncogene at the chromosome location 17q12-q21 and is either amplified or deleted (with equal frequency) in a great majority of HER-2 amplified primary breast tumors and also in tumors without HER-2 amplification. Recent experimental as well as numerous, large, multi-center trials suggest that amplification (and/or deletion) of TOP2A may account for both sensitivity or resistance to commonly used cytotoxic drugs, i.e. topoII-inhibitors (anthracyclines etc.), depending on the specific genetic defect at the TOP2A locus. The understanding of HER-2 amplification and its role in the pathogenesis of cancer is expanding, and a number of therapeutic strategies targeting either the HER-2 or its signaling pathways in cancer therapy are being investigated. Combining HER-2 targeting therapies with conventional forms of cytotoxic chemotherapy, where additional diagnostic tests such as those ascertaining TOP2A status, may be helpful for the ideal selection of patients for the combination therapy of an HER-2 targeting drug together with a cytotoxic drug such as topoII-inhibitor especially in the case of TOP2A amplification.     

Imaging cellular receptors in breast cancers: an overview

Breast cancer, a leading cause of cancer death in women, is strongly correlated with the up- and down-regulation of hormone and growth factor receptors. Therefore, improving our understanding of such receptor status in different stages of breast cancer will help in the development of novel diagnostic and therapeutic solutions. In particular, molecular imaging technology in association with advanced molecular and cell biology techniques could reveal in detail dynamic molecular events in cells, allowing the study of crucial molecular pathological changes occurring in cancer and other diseases. Molecular imaging techniques such as PET, SPECT, MRI, and the combinatorial techniques have made tremendous strides in elucidating the role of cellular receptors, helping to monitor the course of breast cancer development and the therapeutic efficacy of novel drugs. Optical imaging of cellular receptors is emerging as a powerful tool given the advancement of fluorescent and bioluminescent proteins. Estrogen receptor, progesterone receptor, and HER2/neu have been adopted clinically to detect different types of breast cancer and to test novel treatment strategies; however, other cellular receptors may also be involved in breast cancer subtyping and could emerge as treatment prospects. This review will focus on the recent developments of imaging various cellular receptors pertaining to the growth and development of breast cancer.     

Role of trastuzumab in adjuvant therapy for locally invasive breast cancer.

PURPOSE: The role of trastuzumab in adjuvant therapy for locally invasive breast cancer is discussed. SUMMARY: Trastuzumab is a humanized monoclonal antibody that binds to the extracellular domain of human epidermal growth factor receptor-2 (HER2). Currently, trastuzumab is indicated for use in HER2-positive patients with metastatic breast cancer. Because trastuzumab specifically targets a receptor that is overexpressed in tumor cells, it is less likely to cause the cytotoxic adverse effects of traditional chemotherapy. Cardiotoxicity has been a major concern, however. Several trials were started to evaluate trastuzumab in the adjuvant setting in patients diagnosed with early-stage breast cancer. The interim results of these trials have shown a promising effect of adjuvant therapy with trastuzumab in improving overall survival, disease-free survival, relapse-free survival, and distant-disease-free survival. CONCLUSION: The use of trastuzumab as adjuvant therapy in patients with HER2-positive breast cancer can lead to increased survival. The appropriateness of trastuzumab therapy should be considered based on HER2 status, cost, and risk of toxicity.     

Opinion on the use of the antitumor drug trastuzumab (Herceptin) in patients with metastatic breast cancer in the county Mecklenburg-Vorpommern.

The recombinant humanized anti-HER-2 monoclonal antibody trastuzumab (Herceptin) is directed against the human epidermal growth factor receptor on the surface of breast cancer cells. Herceptin was approved in Germany in September 2000 after evaluation in clinical trials involving women with metastatic breast cancer who had tumors overexpressing HER-2/neu. A prerequisite for its use is the diagnosis of the HER-2/neu receptor status in individual patients because trastuzumab is only effective in patients with a high (score +3) overexpression of the HER-2/neu receptor. The only approved diagnostic method is the immunohistochemical DAKO-Hercep test. Clinical experience with this novel biological agent has been obtained in 2 Phase III trials involving 469 and 222 patients, where trastuzumab was used as first- or second-line therapy. The addition of trastuzumab to chemotherapy regimens was associated with longer time to progression, a higher rate and duration of response and longer survival. When used as a single agent in metastatic breast cancer that had progressed after chemotherapy, there was an overall response rate of 15%. The median duration of response was 9.1 months and median survival was 13 months. Unwanted effects included potentially severe cardiotoxicity and in 40% of patients infusion-associated fever and/or shivering that usually occurred only during the first infusion. In patients with moderate HER-2/neu expression, unwanted drug effects outweigh a relatively weak therapeutic effect. In cases of high overexpression, the cancer may go into regression and survival may be prolonged with a relatively small impairment in the life quality. The costs of trastuzumab-therapy are high amounting to an additional 48,000 DM per patient per year. Recommendations for diagnosis and therapy in Mecklenburg-Vorpommern have been formulated in discussions between oncologists, practitioners, scientists and regulatory authorities.     

人表皮生长因子受体2与肿瘤靶向治疗

人表皮生长因子受体2（human epidermal growth factor receptor 2,Her2）是表皮生长因子受体家族成员之一,在乳腺癌等多种人类肿瘤中过表达,是肿瘤治疗的重要靶点,也是肿瘤诊断和预后检测的重要指标。此文阐述了Her2的结构特征、Her2与肿瘤发生发展的关系、抗Her2单克隆抗体在肿瘤治疗中的应用以及针对Her2靶点的其他治疗策略。     

Toward Checkmate: Biology and Breast Cancer Therapy for the New Millennium

A better understanding of the biology of breast cancer should leadto the rational development of new treatments and the ability tocustomize therapy for individual patients. Though promising intheory, translating advances in biological knowledge to the clinichas been difficult. Recently several areas of research haveproduced treatments which have entered clinical trials; three willbe reviewed here. The growth of breast cancer is regulated bygrowth factors and their receptors; amplification or overexpressionis associated with poor prognosis. As such inhibition of growthfactors and/or growth factor receptors may provide an idealtherapeutic target. Herceptin binds to c-erbB-2, a member of theepidermal growth factor receptor family. Significant responses wereseen in patients with c-erbB-2 overexpressing breast cancer withHerceptin administered as a single agent or in combination withchemotherapy. Herceptin was approved by the Food and DrugAdministration in late 1998. Breast cancer invasion and metastasisrequires degradation of the surrounding basement membrane by matrixmetalloproteinases and other proteolytic enzymes. Syntheticinhibitors of these enzymes are now in clinical trials. Breastcancers must stimulate angiogenesis, the growth of new bloodvessels, in order to grow beyond a few millimeters in diameter.This nascent vascular network provides another opportunity fortherapy. Preclinical models support the critical role ofangiogenesis and the therapeutic benefit of angiogenesisinhibition; clinical trials are underway.     

Anticancer activity of bisphosphonates in breast cancer

Despite progress in surgical and adjuvant therapy, a subset of patients with early stage breast cancer experience disease recurrence and/or distant metastases. Disseminated tumor cells (DTCs) in the bone marrow are believed to be the source of late relapses in bone and other tissues. Bone is the most common site of breast cancer metastasis, and agents that modify the bone microenvironment could therefore affect the disease course. Bisphosphonates are an effective bone-targeted therapeutic option for preventing cancer treatment- induced bone loss (CTIBL) in pre- and postmenopausal women with breast cancer. Bisphosphonates inhibit osteoclast-mediated bone resorption, thereby inhibiting the release of growth factors necessary to promote cancer cell growth, differentiation, and tumor formation in bone. Preclinical and clinical data also suggest anticancer synergy between cytotoxic chemotherapy agents and bisphosphonates. Recent trials of zoledronic acid in the adjuvant setting in breast cancer have demonstrated reduced disease recurrence in bone and other sites. Currently, several ongoing clinical trials are evaluating whether antiresorptives can inhibit disease recurrence and the development of bone metastases from breast cancer. Based on recent data, the role of bisphosphonates in the breast cancer setting is expected to expand in the future. With recent changes to treatment guidelines, routine use of bisphosphonates to prevent bone loss during adjuvant therapy is likely to become standard practice, especially for patients receiving endocrine therapy. Furthermore, the use of zoledronic acid to reduce the risk of recurrence is emerging based on ongoing clinical research.