Trastuzumab: updates and future issues

Antibody-conjugated pH-sensitive liposomes for HER-2 positive breast cancer: development, characterization, in vitro and in vivo assessment

The object of the current study was to develop and evaluate trastuzumab-conjugated Paclitaxel (PTX) and Elacridar (ELA)-loaded PEGylated pH-sensitive liposomes (TPPLs) for site-specific delivery of an anticancer drug. In this study, paclitaxel is used as an anticancer drug which promotes microtubules polymerization and arrest cell cycle progression at mitosis and subsequently leading to cell death. The single use of PTX causes multiple drug resistance (MDR) and results failure of the therapy. Hence, the combination of PTX and P-glycoprotein inhibitor (ELA) are used to achieve maximum therapeutic effects of PTX. Moreover, monoclonal antibody (trastuzumab) is used as ligand for the targeting the drug bearing carriers to BC. Thus, trastuzumab anchored pH-sensitive liposomes bearing PTX and ELA were developed using thin film hydration method and Box-Behnken Design (BBD) for optimizing various formulation variables. The optimized liposomes undergo characterization such as vesicle size, PDI, and zeta potential, which were observed to be 122 ± 2.14 nm, 0.224, and -15.5 mV for PEGylated pH-sensitive liposomes (PEG-Ls) and 134 ± 1.88 nm, 0.238, and -13.98 mV for TPPLs, respectively. The results of the in vitro drug release study of both formulations (PEG-Ls and TPPLs) showed enhanced percentage drug release at an acidic pH 5 as compared to drug release at a physiological pH 7.4. Further, the in vitro cytotoxicity studies were performed in the SK-BR-3 and MDA-MB-231 cell lines. The cellular uptake study of FITC-loaded TPPLs in SK-BR-3 cells showed greater uptake than FITC-loaded PEG-Ls, while in MDA-MB-231 cells there was no significant difference in cell uptake between FITC-loaded TPPLs and FITC-loaded PEG-Ls. Hence, it can be concluded that the HER-2 overexpressing cancer cell line (SK-BR-3) was showed better cytotoxicity and cell uptake of TPPLs than the cells that expressed low levels of HER2 (MDA-MB-231). The in vivo tumor regression study, TPPLs showed significantly more tumor burden reduction i.e. up ∼74% as compared to other liposomes after 28 days. Furthermore, the in vivo studies of TPPLs showed a minimal toxicity profile, minimal hemolysis, higher tumor tissue distribution, and superior antitumor efficacy as compared to other formulations. These studies confirmed that TPPLs are a safe and efficacious treatment for breast cancer.

Dendrimer nanoscaffolds for potential theranostics of prostate cancer with a focus on radiochemistry

Dendrimers are a class of structurally defined macromolecules featured with a central core, a low-density interior formed by repetitive branching units, and a high-density exterior terminated with surface functional groups. In contrast to their polymeric counterparts, dendrimers are nanosized and symmetrically shaped, which can be reproducibly synthesized on a large scale with monodispersity. These unique features have made dendrimers of increasing interest for drug delivery and other biomedical applications as nanoscaffold systems. Intended to address the potential use of dendrimers for the development of theranostic agents, which combines therapeutics and diagnostics in a single entity for personalized medicine, this review focuses on the reported methodologies of using dendrimer nanoscaffolds for targeted imaging and therapy of prostate cancer. Of particular interest, relevant chemistry strategies are discussed due to their important roles in the design and synthesis of diagnostic and therapeutic dendrimer-based nanoconjugates and potential theranostic agents, targeted or nontargeted. Given the developing status of nanoscaffolded theranostics, major challenges and potential hurdles are discussed along with the examples representing current advances.

Evidence-Based Principles in Pathology: Existing Problem Areas and the Development of “Quality” Practice Patterns

Context.—Contrary to the intuitive impressions of many pathologists, several areas exist in laboratory medicine where evidence-based medicine (EBM) principles are not applied. These include aspects of both anatomic and clinical pathology. Some non-EBM practices are perpetuated by clinical “consumers” of laboratory services because of inadequate education, habit, or overreliance on empirical factors. Other faulty procedures are driven by pathologists themselves.

Objectives.—To consider (1) several selected problem areas representing non-EBM practices in laboratory medicine; such examples include ideas and techniques that concern metastatic malignancies, “targeted” oncologic therapy, general laboratory testing and data utilization, evaluation of selected coagulation defects, administration of blood products, and analysis of hepatic iron-overload syndromes; and (2) EBM principles as methods for remediation of deficiencies in hospital pathology, and implements for the construction of “quality” practices in our specialty.

Data Sources.—Current English literature relating to evidence-based principles in pathology and laboratory medicine, as well as the authors' experience.

Conclusions.—Evidence-based medicine holds the promise of optimizing laboratory services to produce “quality” practices in pathology. It will also be a key to restraining the overall cost of health care.

The small molecule TGF-β signaling inhibitor SM16 synergizes with agonistic OX40 antibody to suppress established mammary tumors and reduce spontaneous metastasis

Effective tumor immunotherapy may require not only activation of anti-tumor effector cells, but also abrogation of tumor-mediated immunosuppression. The cytokine TGF-β, is frequently elevated in the tumor microenvironment and is a potent immunosuppressive agent and promoter of tumor metastasis. OX40 (CD134) is a member of the TNF-α receptor superfamily and ligation by agonistic antibody (anti-OX40) enhances effector function, expansion, and survival of activated T cells. In this study, we examined the therapeutic efficacy and anti-tumor immune response induced by the combination of a small molecule TGF-β signaling inhibitor, SM16, plus anti-OX40 in the poorly immunogenic, highly metastatic, TGF-β-secreting 4T1 mammary tumor model. Our data show that SM16 and anti-OX40 mutually enhanced each other to elicit a potent anti-tumor effect against established primary tumors, with a 79% reduction in tumor size, a 95% reduction in the number of metastatic lung nodules, and a cure rate of 38%. This positive treatment outcome was associated with a 3.2-fold increase of tumor-infiltrating, activated CD8+ T cells, an overall accumulation of CD4+ and CD8+ T cells, and an increased tumor-specific effector T cell response. Complete abrogation of the therapeutic effect in vivo following depletion of CD4+ and CD8+ T cells suggests that the anti-tumor efficacy of SM16+ anti-OX40 therapy is T cell dependent. Mice that were cured of their tumors were able to reject tumor re-challenge and manifested a significant tumor-specific peripheral memory IFN-γ response. Taken together, these data suggest that combining a TGF-β signaling inhibitor with anti-OX40 is a viable approach for treating metastatic breast cancer.

Alterations in glycopeptides associated with herceptin treatment of human breast carcinoma mcf-7 and T-lymphoblastoid cells

The therapeutic humanized monoclonal antibody IgG1 known as Herceptin® has shown remarkable antitumor effects. Although this type of therapy has increased the cancer-free survival of patients, not all tumors respond to this treatment and cancers often develop resistance to the antibody. Despite the fact that Herceptin function has been extensively studied, the precise mechanism underlying its antitumor activity still remains incompletely defined. We previously demonstrated on human breast MCF-7 carcinoma and T-lymphoblastoid CEM cells that monoclonal antibody in combination with Lipoplex consisting of Lipofectamine mixed with plasmid DNA showed a more profound effect on cancer cell viability than antibody alone. The analyses of N-glycans isolated from cancer cells showed dramatic differences in profiles when cells were exposed to Herceptin. Moreover, the investigation of glycosylated peptides from the same cancer cell models after treatment revealed further alterations in the post-translational modifications. Tandem mass spectra obtained from the samples treated confirmed the presence of a series of glycopeptides bearing characteristic oligosaccharides as described in IgG1. However some of them differed by mass differences that corresponded to peptide backbones not described previously and more of them were detected from Herceptin treated samples than from cells transfected with Heceptin/Lipoplex. The results indicate that the presence of Lipoplex prevents antibody transformation and elongates its proper function. The better understanding of the multipart changes described in the glycoconjugates could provide new insights into the mechanism by which antibody induces regression in cancers.

HER2-targeted therapy in breast cancer. Monoclonal antibodies and tyrosine kinase inhibitors

There is strong clinical evidence that trastuzumab, a monoclonal antibody targeting the human epidermal growth factor receptor (HER) two tyrosine kinase receptor, is an important component of first-line treatment of patients with HER2-positive metastatic breast cancer. In particular the combination with taxanes and vinorelbine has been established. In the preoperative setting inclusion of trastuzumab has significantly increased the pathological complete response rate. Results from large phase III trials evaluating adjuvant therapy in HER2-positive early breast cancer indicate that the addition of trastuzumab to chemotherapy improves disease-free and overall survival. The use of lapatinib, a dual tyrosine kinase inhibitor of both HER1 and HER2, in combination with capecitabine in the second-line treatment of HER2-positive patients with metastatic breast cancer previously treated with trastuzumab has been established. There is modest, but still insufficient, support that the compound passes the blood-brain barrier. Several trials are ongoing both in the adjuvant and metastatic settings and we have to await the results of these to clarify the role of trastuzumab and lapatinib. The clinical problem of tumours developing resistance to HER2-directed therapy is becoming increasingly important. Several issues about optimal selection of patients, prevention of resistance and use of different treatment options are still unresolved. In this article, we summarise the current knowledge on clinical evidence of HER2-directed therapy and the potential mechanisms of underlying resistance, including the possible clinical implications and review new therapeutic options.

Targeting the type 1 insulin-like growth factor receptor as a treatment for cancer

BACKGROUND

The type 1 insulin-like growth factor receptor (IGF1R) plays a critical role in transformation, invasion and apoptosis protection, and is an attractive cancer treatment target.

OBJECTIVE

To review IGF1R antibodies and kinase inhibitors that are in preclinical and clinical development, and to discuss questions that will influence the success of this approach in clinical practice.

METHODS

This review is drawn from published literature, meeting abstracts and online resources.

RESULTS/CONCLUSION

IGF1R blockade is generally well tolerated although it can induce hyperglycaemia. Single-agent activity has been documented in Ewing's sarcoma but not thus far in common solid tumours. Key issues include identification of factors that influence sensitivity to IGF1R blockade, and how most effectively to combine IGF1R inhibitors with other treatments.

Antitumor effect of paclitaxel-loaded PEGylated immunoliposomes against human breast cancer cells

PURPOSE

The antitumor effect of paclitaxel-loaded PEGylated immunoliposome (PILs) was investigated in breast cancer cell lines and the xenograft model.

METHODS

Herceptin was conjugated to paclitaxel-loaded PEGylated liposomes (PLs). In vitro cellular uptake and cytotoxicity of PILs were determined in breast cancer cell lines while in vivo antitumor efficacy was evaluated in the xenograft nude mouse model.

RESULTS

The PILs formulation was able to significantly increase the HER2 mediated cellular uptake of paclitaxel compared to the PLs in cell lines overexpressing HER2 (BT-474 and SK-BR-3 cells). However, in the MDA-MB-231 cells, which express low levels of HER2, the difference between the PILs and PLs formulation was not significant. The biological activity of Herceptin was maintained throughout the conjugation process as exhibited by the antitumor dose-response curves determined for Herceptin itself, for the thiolated Herceptin alone and subsequently for the immunoliposome-coupled Herceptin. In BT-474 and SK-BR-3 cells, the cytotoxicity of the PILs was more potent than that of Taxol. Moreover, in in vivo studies, PILs showed significantly higher tumor tissue distribution of paclitaxel in the BT-474 xenograft model and more superior antitumor efficacy compared to Taxol and PLs. However, in the MDA-MB-231 xenograft model, PILs and PLs showed similar tumor tissue distribution as well as antitumor activity.

CONCLUSIONS

These results suggest that HER2-mediated endocytosis is involved in the PILs formulation. The ability of the PILs formulation to efficiently and specifically deliver paclitaxel to the HER2-overexpressing cancer cells implies that it is a promising strategy for tumor-specific therapy for HER2-overexpressing breast cancers.

Novel therapeutic strategies combining antihormonal and biological targeted therapies in breast cancer: focus on clinical trials and perspectives

Several models have been proposed to explain the mechanisms of endocrine resistance including aberrant growth-signaling pathways, and have led to the rational design of studies combining hormonotherapy with signal transduction inhibitors (STI) in advanced breast cancer. This article reviews the current status of these clinical trials. Preliminary results from the randomized controlled trials are rather disappointing. The mTOR inhibitor temsirolimus and the farnesyl transferase inhibitor tipifarnib combined with letrozole did not show any benefit compared to letrozole alone. As neoadjuvant therapy, gefinitib did not enhance the response rate induced by anastrozole. Interesting results were obtained with exemestane combined to celecoxib but should be further explored with adequate cardiac monitoring. Trastuzumab combined with anastrozole was more effective than anastrozole in terms of response rate and progression-free survival but not survival. Several controlled trials as first- or second-line therapy have started recently and over the next few years we should learn whether this approach will provide significant gains in efficacy.

Novel targeted therapies in epithelial ovarian cancer: from basic research to the clinic

The development of new molecularly targeted therapies represents a high priority for the treatment of epithelial ovarian cancer. P-glycoprotein overexpression has been associated with multidrug resistance, and the use of multidrug resistance modulators, such as valspodar, is being explored in combination with chemotherapy. Human epidermal receptor (HER) family members are attractive targets for biological therapies. The addition of erlotinib or cetuximab to first-line paclitaxel- plus carboplatin-based chemotherapy is feasible and well tolerated. Gefitinib is able to inhibit the proliferation of ovarian clear-cell carcinoma in in vitro and in vivo experimental models. Single-agent trastuzumab has a limited value for recurrent epithelial ovarian cancer owing to the low frequency of HER2 overexpression and the low rate of objective responses among HER2-overexpressing patients. A Gynecologic Oncology Group Phase II trial of the proteasome inhibitor bortezomib in recurrent epithelial ovarian cancer is currently ongoing, and the combination of bortezomib and chemotherapeutic agents should be assessed. The mammalian target of rapamycin (mTOR) plays an important role in stimulating the translation of mRNAs encoding key proteins for cell growth and angiogenesis, and mTOR inhibitors, such as AP-23573 (ARIAD), deserve to be tested in selected epithelial ovarian cancer patients. The addition of intraperitoneal treatment with adenovirus containing human wild-type p53 to standard paclitaxel- plus carboplatin-based chemotherapy failed to improve the clinical outcome of patients with mutated p53 epithelial ovarian cancer. The Gynecologic Oncology Group is conducting a Phase II trial of single-agent bevacizumab (antivascular endothelial growth factor monoclonal antibody) in platinum-resistant disease. In conclusion, emerging drugs for epithelial ovarian cancer include agents designed to overcome chemoresistance, HER-targeting agents, proteasome inhibitors, mTOR inhibitors and angiogenesis inhibitors. A new paradigm of treatment could consist of chemotherapy combined with a biological agent for six cycles, and followed by chronic maintenance therapy with the biological agent alone. Advances in genomics and proteomics will elucidate the molecular mechanisms of ovarian carcinogenesis, which will hopefully lead to individualized molecular medicine in the next years.

Receptor-mediated DNA-targeted photoimmunotherapy

We show the efficacy of a therapeutic strategy that combines the potency of a DNA-binding photosensitizer, UV(A)Sens, with the tumor-targeting potential of receptor-mediated endocytosis. The photosensitizer is an iodinated bibenzimidazole, which, when bound in the minor groove of DNA and excited by UV(A) irradiation, induces cytotoxic lesions attributed to a radical species resulting from photodehalogenation. Although reminiscent of photochemotherapy using psoralens and UV(A) irradiation, an established treatment modality in dermatology particularly for the treatment of psoriasis and cutaneous T-cell lymphoma, a critical difference is the extreme photopotency of the iodinated bibenzimidazole, approximately 1,000-fold that of psoralens. This feature prompted consideration of combination with the specificity of receptor-mediated targeting. Using two in vitro model systems, we show the UV(A) cytotoxicity of iodo ligand/protein conjugates, implying binding of the conjugate to cell receptors, internalization, and degradation of the conjugate-receptor complex, with release and translocation of the ligand to nuclear DNA. For ligand-transferrin conjugates, phototoxicity was inhibited by coincubation with excess native transferrin. Receptor-mediated UV(A)-induced cytotoxicity was also shown with the iodo ligand conjugate of an anti-human epidermal growth factor receptor monoclonal antibody, exemplifying the potential application of the strategy to other cancer-specific targets to thus improve the specificity of phototherapy of superficial lesions and for extracorporeal treatments.

Gene Expression Profiling and Clinical Outcome in Breast Cancer

Pathologic and clinical heterogeneity of breast cancer reflects the poorly documented, complex, and combinatory molecular basis of the disease and is in part responsible for therapeutic failures. The DNA microarray technique allows the analysis of RNA expression of several thousands of genes simultaneously in a sample. There are multiple potential applications of the technique in cancer research. A number of recent studies have shown the promising role of gene expression profiling in breast cancer by identifying new prognostic subclasses unidentifiable by conventional parameters and new prognostic and/or predictive gene signatures, whose predictive impact is superior to conventional histoclinical prognostic factors. In this review we describe current use of DNA microarrays in the prognosis of breast cancer. We also discuss issues that need to be addressed in the near future to allow the method to reach its full potential.

CD45negbut Not CD45posHuman Myeloma Cells Are Sensitive to the Inhibition of IGF-1 Signaling by a Murine Anti-IGF-1R Monoclonal Antibody, mAVE1642

Insulin-like growth factor 1 (IGF-1) is a well-known growth factor for myeloma cells. Thus, therapeutic strategies targeting IGF-1R have been proposed for multiple myeloma treatment. In this study, we investigated the effect of the antagonistic anti-IGF-1R murineAVE1642 Ab (mAVE1642). We show that mAVE1642 selectively inhibits IGF-1R but not insulin signaling in human myeloma cell lines. Since we have previously shown the functional relevance of CD45 expression in the growth of myeloma cells and the association of CD45-negative (CD45neg) status with a less favorable clinical outcome, both CD45-positive (CD45pos) and CD45neg myeloma cell lines were selected for our study. We found that mAVE1642 strongly inhibits the growth of CD45neg myeloma cell lines, leading to a G1 growth arrest, whereas it has almost no effect on the growth of CD45pos myeloma cell lines. Furthermore, mAVE1642 binding induced a significant reduction of IGF-1R expression. We next demonstrated that the overexpression of IGF-1R in the CD45pos myeloma cell line increased Akt phosphorylation but was not sufficient to sensitize these cells to mAVE1642. In contrast, we generated a stable CD45-silencing XG-1 cell line and showed that it became sensitive to mAVE1642. Thus, for the first time, we provided direct evidence that the expression of CD45 renders cells resistant to mAVE1642. Taken together, these results support that therapy directed against IGF-1R can be beneficial in treating CD45neg patients.

Evidence-based principles and practices in pathology: selected problem areas

Contrary to the intuitive impression of most pathologists, there are still many areas in laboratory medicine where evidence-based medicine (EBM) principles are not applied. These include aspects of both anatomic and clinical pathology. Some non-EBM practices are perpetuated by clinical "consumers" of laboratory services, because of inadequate education, habit, or over-reliance on empirical factors. Other faulty procedures are pathologist-driven, with similar underpinnings. This overview considers several exemplary problem areas representing non-EBM practices in the hospital laboratory. Such examples include ideas and techniques centering on metastatic malignancies, "targeted" oncological therapy, analysis of surgical margins in the excision of neoplasms, general laboratory testing and data utilization, evaluation of selected coagulation defects, administration of blood products, and analysis of hepatic iron-overload syndromes. The concepts illustrating departures from EBM are discussed for each of those topics.