A phase I/II study of bortezomib and capecitabine in patients with metastatic breast cancer previously treated with taxanes and/or anthracyclines

The role of NF-κB in breast cancer initiation, growth, metastasis, and resistance to chemotherapy

Breast cancer (BC) is the second most fatal disease and is the prime cause of cancer allied female deaths. BC is caused by aberrant tumor suppressor genes and oncogenes regulated by transcription factors (TFs) like NF-κB. NF-κB is a pro-inflammatory TF that crucially alters the expressions of various genes associated with inflammation, cell progression, metastasis, and apoptosis and modulates a network of genes that underlie tumorigenesis. Herein, we focus on NF-κB signaling pathways, its regulators, and the rationale for targeting NF-κB. This review also includes TFs that maintain NF-κB crosstalk and their roles in promoting angiogenesis and metastasis. In addition, we discuss the importance of combination therapies, resistance to treatment, and potential novel therapeutic strategies including nanomedicine that targets NF-κB.

Temporal proteomics reveal specific cell cycle oncoprotein downregulation by p97/VCP inhibition

Targeting protein quality control (PQC) pathways using proteasome or p97/VCP inhibition can effectively treat blood tumors. However, in solid tumors, only p97/VCP inhibitors are effective. To probe this difference in efficacy, we tracked HCT116 colon cancer cells using temporal proteomics to define the cellular and molecular responses to proteasome and p97 inhibition. Proteins involved in general PQC pathways were similarly upregulated by both treatments, suggesting that the proteotoxic stress caused by inhibitors does not explain the differential therapeutic effectiveness. Unexpectedly, proteins specifically dysregulated by two p97 inhibitors are involved in cell cycle control. Indeed, eleven cell cycle proteins were downregulated by p97 inhibition but not by proteasome inhibition. Western blot analysis validated the degradation of cyclin D1 and Securin, which depends on proteasome but not on p97. Differing regulation of cell cycle proteins by p97 and the proteasome may, therefore, explain the therapeutic efficacy of p97 inhibitors in colon cancer.

Tradeoff between metabolic i-proteasome addiction and immune evasion in triple-negative breast cancer

In vitro studies have suggested proteasome inhibitors could be effective in triple-negative breast cancer (TNBC). We found that bortezomib and carfilzomib induce proteotoxic stress and apoptosis via the unfolded protein response (UPR) in TNBC cell lines, with sensitivity correlated with expression of immuno-(PSMB8/9/10) but not constitutive-(PSMB5/6/7) proteasome subunits. Equally, the transcriptomes of i-proteasome-high human TNBCs are enriched with UPR gene sets, and the genomic copy number landscape reflects positive selection pressure favoring i-proteasome activity, but in the setting of adjuvant treatment, this is actually associated with favorable prognosis. Tumor expression of PSMB8 protein (β5i) is associated with levels of MHC-I, interferon-γ-inducible proteasome activator PA28β, and the densities of stromal antigen-presenting cells and lymphocytes (TILs). Crucially, TILs were protective among TNBCs that maintain high β5i but did not stratify survival amongst β5i-low TNBCs. Moreover, β5i expression was lower in brain metastases than in patient-matched primary breast tumors (n = 34; P = 0.007), suggesting that suppression contributes to immune evasion and metastatic progression. Hence, inhibiting proteasome activity could be counterproductive in the adjuvant treatment setting because it potentiates anti-TNBC immunity.

Angiogenesis in cutaneous T-cell lymphoma - proteomic approaches

Neoangiogenesis plays an important role in cutaneous lymphoma pathogenesis. Cutaneous T-cell lymphoma (CTCL) is characterized by the presence of malignant T-cell clones in the skin. Vascular microenvironment of lymphomas accelerates neoangiogenesis through several factors released by tumoral cells: VEGF family, bFGF and PIGF. Tumor stroma (fibroblasts, inflammatory and immune cells) also plays a crucial role, by providing additional angiogenic factors. The angiogenic process through the VEGF-VEGFR axis can promote survival, proliferation and metastasis via autocrine mechanisms in cutaneous lymphomas. Microvascular density (MVD) measures the neo-vascularization of cutaneous lymphoma, generated by the response of tumor cells, proangiogenic stromal cells, and benign T/B lymphocytes within the tumor inflammatory infiltrate. Pro-angiogenic proteins have been found to indicate the evolution and prognosis in patients with CTCL. In conclusion, anti-angiogenic therapeutic protocols can target tumor vasculature or malignant tumor cells directly or through a large number of combinations with other drugs. The integration of proteomics into clinical practice based on high-throughput technologies leads to the development of personalized medicine, adapting the specific biomarkers to the application of cancer-type specific individual drug targets.

Targeting Proteotoxic Stress in Cancer: A Review of the Role that Protein Quality Control Pathways Play in Oncogenesis

Despite significant advances in cancer diagnostics and therapeutics the majority of cancer unfortunately remains incurable, which has led to continued research to better understand its exceptionally diverse biology. As a result of genomic instability, cancer cells typically have elevated proteotoxic stress. Recent appreciation of this functional link between the two secondary hallmarks of cancer: aneuploidy (oxidative stress) and proteotoxic stress, has therefore led to the development of new anticancer therapies targeting this emerging “Achilles heel” of malignancy. This review highlights the importance of managing proteotoxic stress for cancer cell survival and provides an overview of the integral role proteostasis pathways play in the maintenance of protein homeostasis. We further review the efforts undertaken to exploit proteotoxic stress in multiple myeloma (as an example of a hematologic malignancy) and triple negative breast cancer (as an example of a solid tumor), and give examples of: (1) FDA-approved therapies in routine clinical use; and (2) promising therapies currently in clinical trials. Finally, we provide new insights gleaned from the use of emerging technologies to disrupt the protein secretory pathway and repurpose E3 ligases to achieve targeted protein degradation.

Moving Breast Cancer Therapy up a Notch

Breast cancer is the second most common malignancy, worldwide. Treatment decisions are based on tumor stage, histological subtype, and receptor expression and include combinations of surgery, radiotherapy, and systemic treatment. These, together with earlier diagnosis, have resulted in increased survival. However, initial treatment efficacy cannot be guaranteed upfront, and these treatments may come with (long-term) serious adverse effects, negatively affecting a patient's quality of life. Gene expression-based tests can accurately estimate the risk of recurrence in early stage breast cancers. Disease recurrence correlates with treatment resistance, creating a major need to resensitize tumors to treatment. Notch signaling is frequently deregulated in cancer and is involved in treatment resistance. Preclinical research has already identified many combinatory therapeutic options where Notch involvement enhances the effectiveness of radiotherapy, chemotherapy or targeted therapies for breast cancer. However, the benefit of targeting Notch has remained clinically inconclusive. In this review, we summarize the current knowledge on targeting the Notch pathway to enhance current treatments for breast cancer and to combat treatment resistance. Furthermore, we propose mechanisms to further exploit Notch-based therapeutics in the treatment of breast cancer.

The iron chelator deferasirox synergises with chemotherapy to treat triple-negative breast cancers

To ensure their high proliferation rate, tumor cells have an iron metabolic disorder causing them to have increased iron needs, making them more susceptible to iron deprivation. This vulnerability could be a therapeutic target. In breast cancers, the development of new therapeutic approaches is urgently needed for patients with triple-negative tumors, which frequently relapse after chemotherapy and suffer from a lack of targeted therapies. In this study, we demonstrated that deferasirox (DFX) synergises with standard chemotherapeutic agents such as doxorubicin, cisplatin and carboplatin to inhibit cell proliferation and induce apoptosis and autophagy in triple-negative breast cancer (TNBC) cells. Moreover, the combination of DFX with doxorubicin and cyclophosphamide delayed recurrences in breast cancer patient-derived xenografts without increasing the side-effects of chemotherapies alone or altering the global iron storage of mice. Antitumor synergy of DFX and doxorubicin seems to involve downregulation of the phosphoinositide 3-kinase and nuclear factor-κB pathways. Iron deprivation in combination with chemotherapy could thus help to improve the effectiveness of chemotherapy in TNBC patients without increasing toxicity. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

The nuclear factor-kappa B pathway and response to treatment in breast cancer

The nuclear factor-kappa B (NF-κB) pathway is known to contribute to critical signaling in cancer biology, including breast cancer, through promotion of proliferation, angiogenesis, metastasis, tumor progression, inflammation and cell survival. In this review, in vivo and in vitro studies of the NF-κB pathway in breast cancer are discussed, focusing on DNA damage and the epithelial-mesenchymal transition associated with breast cancer stem cell properties. The relationships between NF-κB signaling and conventional cancer treatments in terms of response to chemo- and radiotherapy will also be discussed. Then contribution and involvement of immune system in the NF-κB pathway will be covered. Furthermore, the future perspective of NF-κB targeting as an innovative strategy to overcome refractory breast cancer, including recent updates on out-receptor activator of NF-κB (RANKing), will be covered.

Bioinformatics analysis of gene expression data for the identification of critical genes in breast invasive carcinoma

Gene expression data were analyzed in order to identify critical genes in breast invasive carcinoma (BRCA). Data from 1,073 BRCA samples and 99 normal samples were analyzed, which were obtained from The Cancer Genome Atlas. Differentially expressed genes (DEGs) were identified using the significance analysis of microarrays method and a functional enrichment analysis was performed using the Database for Annotation, Visualization and Integrated Discovery. Relevant microRNAs (miRNAs), transcription factors (TFs) and associated small molecule drugs were revealed by Fisher's exact test. Furthermore, protein-protein interaction (PPI) information was downloaded from the Human Protein Reference Database. Interactions with a Pearson's correlation coefficient >0.5 were identified and PPI networks were subsequently constructed. A survival analysis was also conducted according to the Kaplan-Meier method. Initially, the 1,073 BRCA samples were clustered into seven groups, and 5,394 DEGs that were identified in ≥4 groups were selected. These DEGs were involved in the cell cycle, ubiquitin-mediated proteolysis, oxidative phosphorylation and human immunodeficiency virus infection. In addition, TFs, including Sp1 transcription factor, DAN domain BMP antagonist family member 5, MYCN proto-oncogene, bHLH transcription factor and cAMP responsive element binding protein (CREB)1, were identified in the BRCA groups. Seven PPI networks were subsequently constructed and the top 10 hub genes were acquired, including RB transcriptional corepressor 1, inhibitor of nuclear factor (NF)-κB kinase subunit γ, NF-κB subunit 2, transporter 1, ATP binding cassette subfamily B member, CREB binding protein and proteasome subunit α3. A significant difference in survival was observed between the two combined groups (groups-2, −4 and −5 vs. groups-1, −3, −6 and −7). In conclusion, numerous critical genes were detected in BRCA, and relevant miRNAs, TFs and small molecule drugs were identified. These findings may advance understanding regarding the pathogenesis of BRCA.

Apoptosis Induction and Gene Expression Profile Alterations of Cutaneous T-Cell Lymphoma Cells following Their Exposure to Bortezomib and Methotrexate

Mycosis fungoides (MF) and its leukemic variant Sézary syndrome (SS) comprise the majority of CTCL, a heterogenous group of non-Hodgkins lymphomas involving the skin. The CTCL’s resistance to chemotherapy and the lack of full understanding of their pathogenesis request further investigation. With the view of a more targeted therapy, we evaluated in vitro the effectiveness of bortezomib and methotrexate, as well as their combination in CTCL cell lines, regarding apoptosis induction. Our data are of clinical value and indicate that the bortezomib/methotrexate combinational therapy has an inferior impact on the apoptosis of CTCL compared to monotherapy, with bortezomib presenting as the most efficient treatment option for SS and methotrexate for MF. Using PCR arrays technology, we also investigated the alterations in the expression profile of genes related to DNA repair pathways in CTCL cell lines after treatment with bortezomib or methotrexate. We found that both agents, but mostly bortezomib, significantly deregulate a large number of genes in SS and MF cell lines, suggesting another pathway through which these agents could induce apoptosis in CTCL. Finally, we show that SS and MF respond differently to treatment, verifying their distinct nature and further emphasizing the need for discrete treatment approaches.

Sense-antisense gene-pairs in breast cancer and associated pathological pathways

More than 30% of human protein-coding genes form hereditary complex genome architectures composed of sense-antisense (SA) gene pairs (SAGPs) transcribing their RNAs from both strands of a given locus. Such architectures represent important novel components of genome complexity contributing to gene expression deregulation in cancer cells. Therefore, the architectures might be involved in cancer pathways and, in turn, be used for novel drug targets discovery. However, the global roles of SAGPs in cancer pathways has not been studied. Here we investigated SAGPs associated with breast cancer (BC)-related pathways using systems biology, prognostic survival and experimental methods. Gene expression analysis identified 73 BC-relevant SAGPs that are highly correlated in BC. Survival modelling and metadata analysis of the 1161 BC patients allowed us to develop a novel patient prognostic grouping method selecting the 12 survival-significant SAGPs. The qRT-PCR-validated 12-SAGP prognostic signature reproducibly stratified BC patients into low- and high-risk prognostic subgroups. The 1381 SAGP-defined differentially expressed genes common across three studied cohorts were identified. The functional enrichment analysis of these genes revealed the GABPA gene network, including BC-relevant SAGPs, specific gene sets involved in cell cycle, spliceosomal and proteasomal pathways. The co-regulatory function of GABPA in BC cells was supported using siRNA knockdown studies. Thus, we demonstrated SAGPs as the synergistically functional genome architectures interconnected with cancer-related pathways and associated with BC patient clinical outcomes. Taken together, SAGPs represent an important component of genome complexity which can be used to identify novel aspects of coordinated pathological gene networks in cancers.

The relationship between nuclear factor (NF)-κB family gene expression and prognosis in triple-negative breast cancer (TNBC) patients receiving adjuvant doxorubicin treatment

We investigated gene expression profiles of the NF-κB pathway in patients with triple-negative breast cancer (TNBC) receiving adjuvant chemotherapy to determine the prognostic value of NF-κB pathway genes according to chemotherapeutic regimen. We used the nCounter expression assay to measure expression of 11 genes (NFKB1, NFKB2, RELA, RELB, REL, TP53, FOXC1, TBP, SP1, STAT3 and IRF1 genes) belonging to the NF-κB pathway using mRNA extracted from paraffin-embedded tumor tissues from 203 patients diagnosed with TNBC. Of the 203 patients, 116 were treated with a chemotherapeutic regimen containing doxorubicin. As revealed by the expression profiles of the 11 genes, increased expression of SP1 was associated with poor prognosis in TNBC patients treated with adjuvant doxorubicin chemotherapy (5-year distant recurrence-free survival [5Y DRFS], low vs. high expression [cut-off: median]: 92.3% vs. 71.6%, P = 0.001). In a multivariate Cox regression model, SP1 expression was a useful marker for predicting long-term prognosis in TNBC patients receiving doxorubicin treatment, and we thus suggest that SP1 expression could serve as a prognostic marker in these patients.

Targeting Notch degradation system provides promise for breast cancer therapeutics

Notch receptor signaling pathways play an important role, not only in normal breast development but also in breast cancer development and progression. As a group of ligand-induced proteins, different subtypes of mammalian Notch (Notch1-4) are sensitive to subtle changes in protein levels. Thus, a clear understanding of mechanisms of Notch protein turnover is essential for understanding normal and pathological mechanisms of Notch functions. It has been suggested that there is a close relationship between the carcinogenesis and the dysregulation of Notch degradation. However, this relationship remains mostly undefined in the context of breast cancer, as protein degradation is mediated by numerous signaling pathways as well as certain molecule modulators (activators/inhibitors). In this review, we summarize the published data regarding the regulation of Notch family member degradation in breast cancer, while emphasizing areas that are likely to provide new therapeutic modalities for mechanism-based anti-cancer drugs.

Next-generation proteasome inhibitor MLN9708 sensitizes breast cancer cells to doxorubicin-induced apoptosis

Doxorubicin (Dox), one of the most effective chemotherapy drug for cancer treatment, is limited by its severe side effects and chemoresistance. Dox induces DNA damage and leads to significant proteomic changes in the cancer cells, which makes the ubiquitin-proteasome system a potential target to enhance the efficacy of Dox therapy. The unsuccessful clinical trials of proteasome inhibitor PS-341 (bortezomib) in solid tumors led to the invention of MLN9708 (ixazomib), an orally bioavailable next-generation proteasome inhibitor with improved pharmacokinetic and pharmacodynamic features. In this preclinical study, we used eight human breast cancer cell lines, which represent the major molecular subtypes of breast cancer, to validate the cytotoxic effects of MLN9708, alone and in combination with Dox. We found that MLN9708 had cytotoxic effects, induced autophagy and MKP-1 expression, and enhanced Dox-induced apoptosis in these cell lines. MLN9708 also enhanced Dox-induced JNK and p38 phosphorylation and inhibited Dox-induced IκBα degradation. Our in vitro results suggest that MLN9708 has antitumor effects in breast cancer and can sensitize breast cancer cells to Dox treatment. This promising combination may be an effective and feasible therapeutic option for treating breast cancer and warrants clinical validation.

Disulfide cross-linked micelles of novel HDAC inhibitor thailandepsin A for the treatment of breast cancer

Histone deacetylase (HDAC) inhibitors are an emerging class of targeted therapy against cancers. Thailandepsin A (TDP-A) is a recently discovered class I HDAC inhibitor with broad anti-proliferative activities. In the present study, we aimed to investigate the potential of TDP-A in the treatment of breast cancer. We demonstrated that TDP-A inhibited cell proliferation and induced apoptosis in breast cancer cells at low nanomolar concentrations. TDP-A activated the intrinsic apoptotic pathway through increase of pro-apoptotic protein Bax, decrease of anti-apoptotic Bcl-2, and cleavage of caspase-3 and poly (ADP-ribose) polymerase (PARP). TDP-A also induced cell cycle arrest at the G2/M phase, and promoted the production of reactive oxygen species (ROS). We have successfully encapsulated TDP-A into our recently developed disulfide cross-linked micelles (DCMs), improving its water solubility and targeted delivery. TDP-A loaded DCMs (TDP-A/DCMs) possess the characteristics of high loading capacity (>20%, w/w), optimal and monodisperse particle size (16 ± 4 nm), outstanding stability with redox stimuli-responsive disintegration, sustained drug release, and preferential uptake in breast tumors. In the MDA-MB-231 breast cancer xenograft model, TDP-A/DCMs were more efficacious than the FDA-approved FK228 at well-tolerated doses. Furthermore, TDP-A/DCMs exhibited synergistic anticancer effects when combined with the proteasome inhibitor bortezomib (BTZ) loaded DCMs (BTZ/DCMs). Our results indicate that TDP-A nanoformulation alone or in combination with BTZ nanoformulation are efficacious against breast cancer.

IKKβ inhibitor in combination with bortezomib induces cytotoxicity in breast cancer cells

Bortezomib is a proteasome inhibitor with remarkable clinical antitumor activity in multiple myeloma (MM) and is under evaluation in clinical trials in various types of cancer including breast cancer. Although the initial rationale for its use in cancer treatment was the inhibition of NF-κB activity by blocking proteasomal degradation of IκBα, direct evidence indicating inhibition of constitutive NF-κB activity by bortezomib in tumor cells in patients has not yet been reported. Moreover, recent studies have shown that bortezomib activates constitutive NF-κB activity via stimulating the canonical pathway in MM cells. In this study, we first examined protein expression of IκBα after bortezomib treatment. We observed that bortezomib upregulated the phosphorylation and downregulated IκBα protein expression in a dose- and time-dependent manner in MCF7 and T47D cells, associated with phosphorylation of IKKβ. Since IκBα is an inhibitor of nuclear translocation of NF-κB, we further examined alteration of NF-κB activity by bortezomib. Importantly, bortezomib significantly upregulates NF-κB activity in both MCF7 and T47D in a dose-dependent fashion, demonstrated by electrophoretic mobility shift analysis (EMSA). Furthermore, immunocytochemical analysis confirmed enhanced nuclear translocation of p65 NF-κB (RelA) by bortezomib treatment. Supershift assay showed supershifted bands by anti-p65 and -p50 antibodies. Taken together, these results indicate that bortezomib activates the canonical NF-κB pathway in both cell lines. Finally, we demonstrated that IKKβ inhibitor enhanced cytotoxicity, associated with inhibition of NF-κB activity induced by bortezomib in MCF7 and T47D breast cancer cells.

Boron chemicals in diagnosis and therapeutics

Advances in the field of boron chemistry have expanded the application of boron from material use to medicine. Boron-based drugs represent a new class of molecules that possess several biomedical applications including use as imaging agents for both optical and nuclear imaging as well as therapeutic agents with anticancer, antiviral, antibacterial, antifungal and other disease-specific activities. For example, bortezomib (Velcade(®)), the only drug in clinical use with boron as an active element, was approved in 2003 as a proteasome inhibitor for the treatment of multiple myeloma and non-Hodgkin's lymphoma. Several other boron-based compounds are in various phases of clinical trials, which illustrates the promise of this approach for medicinal chemists working in the area of boron chemistry. It is expected that in the near future, several boron-containing drugs should become available in the market with better efficacy and potency than existing drugs. This article discusses the current status of the development of boron-based compounds as diagnostic and therapeutic agents in humans.

Bortezomib suppresses the growth of leukemia cells with Notch1 overexpression in vivo and in vitro

Bortezomib has been widely used in the treatment of various cancers; however, its exact mechanisms of action are not fully understood, particularly in acute T lymphoblast leukemia (T-ALL). Here, we visualize the anti-leukemia effect of bortezomib in both human T-ALL cell line and animal models. In vitro study, a human T-ALL cell line bearing Notch1 mutations, MOLT-4, was treated with bortezomib. At clinically achievable concentrations, bortezomib inhibited cell growth by inducing G1 phase arrest and apoptosis with a dose-dependent manner. A murine tumor xenograft model was achieved by subcutaneous injection of MOLT-4 cells for in vivo study. Administration of bortezomib significantly reduced tumor mass volume when compared with controls. Of note, bortezomib inhibited growth of leukemia cells in a Notch1-induced murine T-ALL model, and the life span of leukemia-bearing mice was markedly increased. Further studies revealed that bortezomib led to inhibited expression of Notch1 target genes. Taken together, our results demonstrate that bortezomib shows significant anti-leukemia effect in T-ALL bearing Notch1 mutations in vitro and in vivo. The present study provides evidence that bortezomib might be a candidate therapeutic reagent in the treatment of T-ALL.

CIP2A is a target of bortezomib in human triple negative breast cancer cells

Introduction

Triple negative breast cancer (TNBC) is very aggressive and currently has no specific therapeutic targets, such as hormone receptors or human epidermal growth factor receptor type 2 (HER2); therefore, prognosis is poor. Bortezomib, a proteasome inhibitor, may exert efficacy in TNBC through its multiple cellular effects. Here, we tested the efficacy of bortezomib and examined the drug mechanism in breast cancer cells.

Methods

Five breast cancer cell lines: TNBC HCC-1937, MDA-MB-231, and MDA-MB-468; HER2-overexpressing MDA-MB-453; and estrogen receptor positive MCF-7 were used for in vitro studies. Apoptosis was examined by both flow cytometry and Western Blot. Signal transduction pathways in cells were assessed by Western Blot. Gene silencing was done by small interfering RNA (siRNA). In vivo efficacy of bortezomib was tested in nude mice with breast cancer xenografts. Immunohistochemical study was performed on tumor tissues from patients with TNBC.

Results

Bortezomib induced significant apoptosis, which was independent of its proteasome inhibition, in the three TNBC cell lines, but not in MDA-MB-453 or MCF-7 cells. Furthermore, cancerous inhibitor of protein phosphatase 2A (CIP2A), a cellular inhibitor of protein phosphatase 2A (PP2A), mediated the apoptotic effect of bortezomib. We showed that bortezomib inhibited CIP2A in association with p-Akt downregulation in a dose- and time-dependent manner in all sensitive TNBC cells, whereas no alterations in CIP2A expression and p-Akt were noted in bortezomib-resistant cells. Overexpression of CIP2A upregulated p-Akt and protected MDA-MB-231 and MDA-MB-468 cells from bortezomib-induced apoptosis, whereas silencing CIP2A by siRNA overcame the resistance to bortezomib-induced apoptosis in MCF-7 cells. In addition, bortezomib downregulated CIP2A mRNA but did not affect the degradation of CIP2A protein. Furthermore, bortezomib exerted in vivo antitumor activity in HCC-1937 xenografted tumors, but not in MCF-7 tumors. Bortezomib downregulated CIP2A expression in the HCC-1937 tumors but not in the MCF-7 tumors. Importantly, CIP2A expression is readily detectable in tumor samples from TNBC patients.

Conclusions

CIP2A is a major determinant mediating bortezomib-induced apoptosis in TNBC cells. CIP2A may thus be a potential therapeutic target in TNBC.

Emerging drugs in metastatic breast cancer: an update

INTRODUCTION

The incidence of breast cancer at an advanced stage has decreased in the modern world due to screening programs and usage of novel chemotherapy agents at an adjuvant setting. Recurrence is the major problem seen in > 50% of breast cancer patients diagnosed at an early stage. Developing new drugs for metastatic breast cancer is a huge and challenging research area.

AREAS COVERED

Emerging drugs showed positive results in clinical studies and agents in routine clinical usage are updated. Current treatment strategies as a combination of biologic agents and overcoming drug resistance are discussed. Literature search is made from PubMed, ASCO and San Antonio Breast Cancer Symposium Meeting abstracts.

EXPERT OPINION

A number of drugs caused survival benefit for advanced breast cancer. Hundreds of new studies with tens of agents are conducted for treatment of metastatic breast cancer. Tumor resistance and treatment related toxicities are unavoidable which are two main search areas for improving metastatic breast cancer management. Understanding the pathways of genesis and progression yielded many targets for treatment. However, cure in metastatic breast cancer is still a far aim and new agents and treatment strategies are needed.

Phase II study of bortezomib and pegylated liposomal doxorubicin in the treatment of metastatic breast cancer

BACKGROUND

Based on preclinical studies and a phase I trial of the combination of bortezomib and pegylated liposomal doxorubicin (PLD), which both showed activity in breast cancer, we conducted a phase II study of this regimen in patients with metastatic breast cancer.

PATIENTS AND METHODS

Patients received bortezomib 1.3 mg/m2 on days 1, 4, 8, and 11 of an every-21-day cycle, along with PLD 30 mg/m2 on day 4. The primary objective was to evaluate the response rate of this combination, while secondary objectives were to obtain further safety data about this combination, to evaluate the time to disease progression (TTP), and to evaluate response by the breast cancer subtype.

RESULTS

One of 12 evaluable patients had a partial response (8%), while 3 (25%) had stable disease. At 26 months follow-up, the median overall survival was 4.3 months (95% CI, 1.2-26.2) and the median TTP was 1.3 months (95% CI, 0.8-14.0 months). The combination was well tolerated, with the most common events including low-grade nausea and vomiting, neutropenia, and neuropathy, and no cardiac toxicity was seen. Of the 7 tumors subtyped, no association was seen between intrinsic subtype or receptor status and response.

CONCLUSION

The combination of PLD and bortezomib was well tolerated but has minimal activity in heavily pretreated unselected metastatic breast cancer.

A proteasome inhibitor, bortezomib, inhibits breast cancer growth and reduces osteolysis by downregulating metastatic genes

PURPOSE

The incidence of bone metastasis in advanced breast cancer (BrCa) exceeds 70%. Bortezomib, a proteasome inhibitor used for the treatment of multiple myeloma, also promotes bone formation. We tested the hypothesis that proteasome inhibitors can ameliorate BrCa osteolytic disease.

EXPERIMENTAL DESIGN

To address the potentially beneficial effect of bortezomib in reducing tumor growth in the skeleton and counteracting bone osteolysis, human MDA-MB-231 BrCa cells were injected into the tibia of mice to model bone tumor growth for in vivo assessment of treatment regimens before and after tumor growth.

RESULTS

Controls exhibited tumor growth, destroying trabecular and cortical bone and invading muscle. Bortezomib treatment initiated following inoculation of tumor cells strikingly reduced tumor growth, restricted tumor cells mainly to the marrow cavity, and almost completely inhibited osteolysis in the bone microenvironment over a 3- to 4-week period as shown by [(18)F]fluorodeoxyglucose positron emission tomography, micro-computed tomography scanning, radiography, and histology. Thus, proteasome inhibition is effective in killing tumor cells within the bone. Pretreatment with bortezomib for 3 weeks before inoculation of tumor cells was also effective in reducing osteolysis. Our in vitro and in vivo studies indicate that mechanisms by which bortezomib inhibits tumor growth and reduces osteolysis result from inhibited cell proliferation, necrosis, and decreased expression of factors that promote BrCa tumor progression in bone.

CONCLUSION

These findings provide a basis for a novel strategy to treat patients with BrCa osteolytic lesions, and represent an approach for protecting the entire skeleton from metastatic bone disease.

Notch versus the proteasome: what is the target of gamma-secretase inhibitor-I?

gamma-Secretase inhibitors are new anti-cancer agents targeting Notch signaling. Their specificity for Notch is as yet unclear. Han and colleagues investigated the effects of Z-LeuLeuNleu-CHO on growth of breast cancer cells. The results demonstrated a reduction in cell viability primarily via proteasome inhibition independent of Notch activity. Currently, gamma-secretase inhibitors in clinical trials are structurally distinct from Z-LeuLeuNleu-CHO. Their effects on the proteasome are yet to be determined. However, findings from Han and colleagues pose two critical questions: Is the level of proteasomal activity in breast tumors the driving force for growth? What does the Notch pathway contribute to this growth?

Cancer cell sensitivity to bortezomib is associated with survivin expression and p53 status but not cancer cell types

Background

Survivin is known playing a role in drug resistance. However, its role in bortezomib-mediated inhibition of growth and induction of apoptosis is unclear. There are conflicting reports for the effect of bortezomib on survivin expression, which lacks of a plausible explanation. Methods: In this study, we tested cancer cells with both p53 wild type and mutant/null background for the relationship of bortezomib resistance with survivin expression and p53 status using MTT assay, flow cytometry, DNA fragmentation, caspase activation, western blots and RNAi technology.

Results

We found that cancer cells with wild type p53 show a low level expression of survivin and are sensitive to treatment with bortezomib, while cancer cells with a mutant or null p53 show a high level expression of survivin and are resistant to bortezomib-mediated apoptosis induction. However, silencing of survivin expression utilizing survivin mRNA-specific siRNA/shRNA in p53 mutant or null cells sensitized cancer cells to bortezomib mediated apoptosis induction, suggesting a role for survivin in bortezomib resistance. We further noted that modulation of survivin expression by bortezomib is dependent on p53 status but independent of cancer cell types. In cancer cells with mutated p53 or p53 null, bortezomib appears to induce survivin expression, while in cancer cells with wild type p53, bortezomib downregulates or shows no significant effect on survivin expression, which is dependent on the drug concentration, cell line and exposure time.

Conclusions

Our findings, for the first time, unify the current inconsistent findings for bortezomib treatment and survivin expression, and linked the effect of bortezomib on survivin expression, apoptosis induction and bortezomib resistance in the relationship with p53 status, which is independent of cancer cell types. Further mechanistic studies along with this line may impact the optimal clinical application of bortezomib in solid cancer therapeutics.

The development and pharmacology of proteasome inhibitors for the management and treatment of cancer

The ubiquitin-proteasome complex is an important molecular target for the design of novel chemotherapeutics. This complex plays a critical role in signal transduction pathways important for tumor cell growth and survival, cell-cycle control, transcriptional regulation, and the modulation of cellular stress responses to endogenous and exogenous stimuli. The sensitivity of transformed cells to proteasome inhibitors and the successful design of treatment protocols with tolerable, albeit narrow, therapeutic indices have made proteasome inhibition a viable strategy for cancer treatment. Clinical validation of the proteasome as a molecular target was achieved with the approval of bortezomib, a boronic acid proteasome inhibitor, for the treatment of multiple myeloma and mantle cell lymphoma. Several "next-generation" proteasome inhibitors (carfilzomib and PR-047, NPI-0052, and CEP-18770) representing distinct structural classes (peptidyl epoxyketones, beta-lactones, and peptidyl boronic acids, respectively), mechanisms of action, pharmacological and pharmacodynamic activity profiles, and therapeutic indices have now entered clinical development. These agents may expand the clinical utility of proteasome inhibitors for the treatment of solid tumors and for specific non-oncological, i.e., inflammatory disease, indications as well. This chapter addresses the biology of the proteasome, the medicinal chemistry and mechanisms of action of proteasome inhibitors currently in clinical development, the preclinical and clinical pharmacological and safety profiles of bortezomib and the newer compounds against hematological and solid tumors. Future directions for research and other applications for this novel class of therapeutics agents are considered in this chapter.

Novel therapeutic approaches to the treatment of metastatic breast cancer

Metastatic breast cancer is ultimately an incurable disease, although recent data have shown that its incidence is decreasing and that patients with metastatic breast cancer live longer. This improvement in survival seems to be linked with the introduction of new therapeutic agents, novel combinations of existing therapies and targeted therapies. Our increasing understanding of the molecular biology of metastatic disease has allowed the development of therapies aimed at specific molecular targets. Some of these have already been approved for the treatment of metastatic breast cancer in combination with cytotoxics, and others have shown promising results regarding disease-free survival, overall response rates and time to disease progression. Given the enormous amount of information about drug discovery in cancer, it is important to be familiar with the present state of the treatment of metastatic breast cancer. The purpose of this review is to provide an update on the development of some of the most promising novel agents and treatment strategies in metastatic breast cancer.

Molecular targets for treatment of inflammatory breast cancer

Despite progress in combined-modality treatment with chemotherapy, surgery, and radiation therapy, the long-term outcome for patients with inflammatory breast cancer (IBC) remains poor. Therapies that target vasculolymphatic processes--angiogenesis, lymphangiogenesis, and vasculogenesis--have shown potential in the treatment for IBC, as represented by bevacizumab. Although the therapeutic effect of targeting lymphangiogenesis and vasculogenesis requires further investigation, targeting of angiogenesis has potential, not only through true antiangiogenic effects, but also through antitumor effects in concert with other pathways. Therapies that target cell proliferation pathways are the most promising targeted therapies for IBC. In particular, therapies that target human epidermal growth factor receptor 2 (for example, trastuzumab and lapatinib) have performed well in the clinical setting, leading to improved outcomes for patients with IBC. Metastatic pathways could have a unique, key role in the aggressiveness of the IBC phenotype. Further extensive work on the unique molecular characteristics of IBC is essential to ensure improved outcomes for patients with this disease. In this Review we discuss three pathways--vasculolymphatic, cell proliferation and metastatic--that could represent important targets in the treatment of IBC.

Clinical development of novel proteasome inhibitors for cancer treatment

BACKGROUND

Emerging evidence demonstrates that targeting the tumor proteasome is a promising strategy for cancer therapy.

OBJECTIVE

This review summarizes recent results from cancer clinical trials using specific proteasome inhibitors or some natural compounds that have proteasome-inhibitory effects.

METHODS

A literature search was carried out using PubMed. Results about the clinical application of specific proteasome inhibitors and natural products with proteasome-inhibitory activity for cancer prevention or therapy were reviewed.

RESULTS/CONCLUSION

Bortezomib, the reversible proteasome inhibitor that first entered clinical trials, has been studied extensively as a single agent and in combination with glucocorticoids, cytotoxic agents, immunomodulatory drugs and radiation as treatment for multiple myeloma and other hematological malignancies. The results in some cases have been impressive. There is less evidence of bortezomib's efficacy in solid tumors. Novel irreversible proteasome inhibitors, NPI-0052 and carfilzomib, have also been developed and clinical trials are underway. Natural products with proteasome-inhibitory effects, such as green tea polyphenol (-)-epigallocatechin-3-gallate (EGCG), soy isoflavone genistein, and the spice turmeric compound curcumin, have been studied alone and in combination with traditional chemotherapy and radiotherapy against various cancers. There is also interest in developing these natural compounds as potential chemopreventive agents.

Perturbation of DNA repair pathways by proteasome inhibitors corresponds to enhanced chemosensitivity of cells to DNA damage-inducing agents

Purpose

Breast cancer treatment often employs DNA double-strand breaks (DSBs), such as that induced by irradiation or anticancer agents. Ubiquitination is required at the site of DNA damage and plays a crucial role in the DSB repair pathway. We investigated the effect of proteasome inhibitors on the pathway after exposure to chemotherapeutic agents and examined its correlation with cytotoxicity.

Methods

Cells were exposed for 1 h to DNA damage-inducing chemotherapeutic agents. After DNA damage, nuclear foci formation of conjugated ubiquitin (Ub-foci) and cell viability were examined in the absence or presence of proteasome inhibitors MG132 and epoxomicin.

Results

Proteasome inhibitors trapped conjugated ubiquitin in the cytosol and blocked irinotecan (CPT-11)- and epirubicin-induced Ub-foci formation in MCF10A cells and HeLa cells, but not in MCF7 cells. MG132 sensitized MCF10A cells to CPT-11 and epirubicin treatment, demonstrating a synergistic effect. This synergistic effect is likely due to the failure to repair DNA, because a significant rise in unrepaired DNA damage was observed in the cells treated with MG132. On the other hand, no synergy was observed in MCF7 cells or when MG132 was combined with docetaxel.

Conclusions

The synergistic effect of proteasome inhibitors in combination with DNA damage-inducing agents warrants further investigating into its effectiveness in the treatment of breast cancer.

The tumor proteasome as a novel target for gold(III) complexes: implications for breast cancer therapy

Although cisplatin plays a vital role in the treatment of several types of human cancer, its wide use is limited by the development of drug resistance and associated toxic side effects. Gold and gold complexes have been used to treat a wide range of ailments for many centuries. In recent years, the use of gold(III) complexes as an alternative to cisplatin treatment was proposed due to the similarities of gold and platinum. Gold(III) is isoelectronic with platinum(II) and gold(III) complexes have the same square-planar geometries as platinum(II) complexes, such as cisplatin. Although it was originally thought that gold(III) complexes might have the same molecular target as cisplatin, several lines of data indicated that proteins, rather than DNA, are targeted by gold complexes. We have recently evaluated cytotoxic and anti-cancer effects of several gold(III) dithiocarbamates against human breast cancer cells in vitro and in vivo. We have identified the tumor proteasome as an important target for gold(III) complexes and have shown that proteasome inhibition by gold(III) complexes is associated with apoptosis induction in breast cancer cells in vitro and in vivo. Furthermore, treatment of human breast tumor-bearing nude mice with a gold(III) dithiocarbamate complex was associated with tumor growth inhibition, supporting the significance of its potential development for breast cancer treatment.

Bortezomib treatment of ovarian cancer cells mediates endoplasmic reticulum stress, cell cycle arrest, and apoptosis

Bortezomib, an approved drug for the treatment of certain haematological neoplasms, is currently being tested in clinical trials as a potential therapeutic agent against several types of solid cancer, including ovarian cancer. We have analyzed the effect of bortezomib on ovarian cancer cells and tissue explants either as a single agent or in combination with carboplatin, taxol, or TRAIL (tumor necrosis factor-related apoptosis-inducing ligand). Bortezomib alone efficiently induced apoptosis in ovarian cancer cells. Apoptosis was preceded by an upregulation of the endoplasmic reticulum stress sensor ATF3, and increased the expression of cytoplasmic heat shock proteins. Bortezomib enhanced the sensitivity of ovarian cancer cells and tissue explants to an apoptosis-inducing TRAIL receptor antibody by upregulating the TRAIL receptor DR5. In contrast to the synergistic effect observed for TRAIL, the efficacy of the taxol treatment was reduced by bortezomib, and bortezomib inhibited the G2/M phase accumulation of ovarian cancer cells treated with taxol. Bortezomib alone or in combination with taxol induced a cell cycle arrest within the S phase, and downregulation of cdk1, a cyclin-dependent kinase that is necessary for the entry into the M phase. Thus, bortezomib can be regarded as a promising agent for the treatment of ovarian cancer and could either be administered as a single agent or in combination with TRAIL. However, a combination treatment with taxanes may not be beneficial and may even be less effective.

Molecular targeted therapies for breast cancer treatment

Targeting the oestrogen receptor, HER2 (human epidermal growth factor receptor 2) and vascular endothelial growth factor has markedly improved breast cancer therapy. New targeted therapeutic approaches to induction of apoptosis or inhibition of anti-apoptosis, cell cycle progression, signal transduction and angiogenesis are described. The molecular pathways and their inhibitory or repair mechanisms are discussed in the preclinical and clinical settings.

Treatment with proteasome inhibitor bortezomib enhances antigen-specific CD8+ T-cell-mediated antitumor immunity induced by DNA vaccination

There is an urgent need to develop new innovative therapies for the control of cancer. Antigen-specific immunotherapy and the employment of proteasome inhibitors have emerged as two potentially plausible approaches for the control of cancer. In the current study, we explored the combination of the DNA vaccine encoding calreticulin (CRT) linked to human papillomavirus type 16 E7 antigen (CRT/E7) with the proteasome inhibitor, bortezomib, for their ability to generate E7-specific immune responses and antitumor effects in vaccinated mice. We found that the combination of treatment with bortezomib and CRT/E7(detox) DNA generated more potent E7-specific CD8+ T cell immune responses and better therapeutic effects against TC-1 tumors in tumor-bearing mice compared to monotherapy. Furthermore, we found that treatment with bortezomib led to increased apoptosis of TC-1 tumor cells and could render the TC-1 tumor cells more susceptible to lysis by E7-specific CD8+ T cells. Our data have significant implications for future clinical translation.

Differential radiation sensitization of human cervical cancer cell lines by the proteasome inhibitor velcade (bortezomib, PS-341)

PURPOSE/OBJECTIVE(S)

Cervical cancer is one of the deadliest cancers in women with a death toll of 230,000 worldwide each year, nearly 80% in developing countries. Radiotherapy (RT) is a major treatment modality for advanced cervical cancer but the local relapse rate is 30-44% in patients treated with RT alone and 19-25% in patients treated with concurrent chemoradiotherapy. Previous studies have shown that the transcription factor NF-kappaB is constitutively expressed in human cervical squamous cell carcinomas. NF-kappaB activation also contributes to the resistance of cervical cancer cells to apoptosis induced by chemotherapeutic agents and radiation. Therefore, inhibition of NF-kappaB in tumor cells may render them more sensitive to chemo/radiation therapies. The objective of this study is to investigate the potential of radiosensitization of NF-kappaB inhibition by Velcade in human cervical cancer cell lines.

MATERIALS AND METHODS

We used the human cervical cancer cell lines HeLa and SiHa. Both are highly radioresistant and chemoresistant as compared to other cervical cancer cell lines. These cells had been treated with Velcade before they were irradiated with different doses of ionizing radiation. MTT metabolic assays and clonogenic cell survival assays were performed to evaluate the effects of Velcade on radiation resistance.

RESULTS

Inhibition of NF-kappaB by Velcade alone decreased metabolic potential (MTT) and clonogenic survival in SiHa, but not in HeLa cells. Furthermore, pre-treatment of SiHa, but not HeLa cells with Velcade enhanced radiation sensitivity.

CONCLUSIONS

Inhibition of NF-kappaB by the proteasome inhibitor Velcade enhances radiosensitivity of certain human cervical carcinoma cancer cells in vitro. These results raise the possibility that inhibition of NF-kappaB will result in radiosensitization only in those tumor cells which are more dependent on NF-kappaB for their metabolism and survival, however, the radiosensitivity of "NF-kappaB independent" cells are not likely influenced by it.