Targeted therapies in breast cancer: Where are we now?

Safety analysis of therapeutic drugs for breast cancer patients and construction of a predictive model for serious adverse drug reactions

OBJECTIVES

To explore the characteristics of the occurrence of antineoplastic drug adverse reactions (ADRs) in breast cancer and to utilize a computerized tool to identify early warning indicators of potentially serious ADRs.

METHODS

We conducted descriptive statistical analyses of the demographic features, medication use characteristics, and clinical manifestations of suspected ADRs in ADR-exposed patients using data from the Shaanxi Provincial Adverse Drug Reaction Monitoring Center, China, from 2017 to 2021. Using disproportionality methods (reporting odds ratio, proportional reporting ratio, and comprehensive standard method), the relationship between drugs and ADRs was measured. Finally, a web-based clinical prediction model for serious ADRs based on binary logistic regression was developed to estimate individual event probabilities numerically.

RESULTS

We developed a new computer-mineable breast cancer-ADR system. In total, 1119 ADR reports were received between 2017 and 2021, with an increasing trend in the number. Antineoplastic medications of natural sources made up the greatest portion of the drug category (530, 38.10%) while targeted drugs' part increased with time. The medicine with the greatest number of ADR cases was docetaxel. Bone marrow failure was the most reported ADR. The disproportionality methods produced 19 signals of disproportionate reporting, two signals of disproportionate reporting were unknown ADRs. The occurrence of serious ADRs was shown to be substantially correlated with gender, platinum drugs, and blood and lymphatic system disorders. The clinical prediction model for serious ADRs had above-moderate discriminatory power (C-index was 0.775).

CONCLUSIONS

The number of ADRs to breast cancer antineoplastic drugs was constantly increasing, with docetaxel ranking first, with the majority of ADRs presenting as bone marrow suppression, nausea, and vomiting. Data mining identified 19 signals of disproportionate reporting.

Bayesian two-stage sequential enrichment design for biomarker-guided phase II trials for anticancer therapies

Biomarker-guided phase II trials have become increasingly important for personalized cancer treatment. In this paper, we propose a Bayesian two-stage sequential enrichment design for such biomarker-guided trials. We assumed that all patients were dichotomized as marker positive or marker negative based on their biomarker status; the positive patients were considered more likely to respond to the targeted drug. Early stopping rules and adaptive randomization methods were embedded in the design to control the number of patients receiving inferior treatment. At the same time, a Bayesian hierarchical model was used to borrow information between the positive and negative control arms to improve efficiency. Simulation results showed that the proposed design achieved higher empirical power while controlling the type I error and assigned more patients to the superior treatment arms. The operating characteristics suggested that the design has good performance and may be useful for biomarker-guided phase II trials for evaluating anticancer therapies.

Erb‑B2 Receptor Tyrosine Kinase 2 is negatively regulated by the p53‑responsive microRNA‑3184‑5p in cervical cancer cells

The oncogenic role of Erb‑B2 Receptor Tyrosine Kinase 2 (ERBB2) has been identified in several types of cancer, but less is known on its function and mechanism of action in cervical cancer cells. The present study employed a multipronged approach to investigate the role of ERBB2 in cervical cancer. ERBB2 and microRNA (miR)‑3184‑5p expression was assessed in patient‑derived cervical cancer biopsy tissues, revealing that higher levels of ERBB2 and lower levels of miR‑3184‑5p were associated with clinicopathological indicators of cervical cancer progression. Furthermore, ERBB2 stimulated proliferation, migration and sphere‑formation of cervical cancer cells in vitro. This effect was mediated by enhanced phosphatidylinositol‑4,5‑bisphosphate 3‑kinase catalytic subunit α activity. Additionally, it was revealed that miR‑3184‑5p directly suppressed ERBB2 in cervical cancer cells. The p53 activator Mithramycin A stimulated p53 and miR‑3184‑5p expression, thereby lowering the levels of ERBB2 and attenuating proliferation, migration and sphere‑formation of cervical cancer cells. In conclusion, the findings of the present study suggested ERBB2 as an oncogenic protein that may promote invasiveness in cervical cancer cells. Treatment of cervical cancer cells with the p53 activator Mithramycin A restored the levels of the endogenous ERBB2 inhibitor miR‑3184‑5p and may represent a novel treatment strategy for cervical cancer.

Single-cell-level screening method for migratory cancer cells and its potential feasibility in high-throughput manner

High-throughput screening (HTS) is a well-established approach for tumor-specific drug development because of its high efficiency and customizable selection of antineoplastic drugs. However, there is still a lack of an appropriate cell-based HTS specific for migratory cancer cells. In the study presented here, we created a novel assay (mHTS): a single-cell-level screening method targeting migratory cancer cells and can be applied in a high-throughput manner. This mHTS platform is based on microchannel devices (providing physical confinement during cell migration and limit migrating cells' proliferation rate) assembled 96-well plate (fitting to HTS manner). To determine the feasibility of this assay, we quantified the anti-migratory and anti-viability effects of several molecules (Cytochalasin D, Doxorubicin and AZD-6244) on migrating (creeping inside microchannel) glioblastoma multiforme (GBM) cells. After analyzing migration screening data that was collected on a single-cell-level, we were able to compare those drug's effects on cancer cells' migration velocity and uncovered the migration inhibiting potential of AZD (500 nM and 1000 nM). Viability data based on single-cell-level screening also allowed us to further understand the same drug's different lethality toward migrating and normal 2D cultured cancer cells. The Pre-classification of subpopulations enables us to study the heterogeneity of cancer and ensures our method's feasibility for a high-throughput manner. All these results proved our mHTS platform is suitable for single-cell-level anti-migration drug screening and has potential feasibility in promoting the development of anti-migratory-cancer-drug in a high-throughput manner.

Evaluation of the Insulin-like Growth Factor Receptor Pathway in Patients with Advanced Breast Cancer Treated with Trastuzumab

BACKGROUND

Trastuzumab is a monoclonal antibody against HER2-positive breast cancer. Despite improving the natural history of the disease, there is a number of patients who are resistant to it, whereas all patients will eventually develop resistance and disease will progress. Inconsistent preclinical data show that the IGF-R pathway may contribute to either de novo or acquired resistance to trastuzumab.

MATERIALS AND METHODS

In total, 227 trastuzumab-treated metastatic breast cancer patients were evaluated for IGF-1, IGF-1R, GLP-1R, Akt1, Akt2 Akt3 mRNA expression, and IGF-1Rα, IGF-1Rβ, IGF-2R protein expression.

RESULTS

Only 139 patients were truly HER2-positive by central assessment. Among HER2-positive patients, high Akt2 and GLP-1R mRNA expression showed a trend towards higher and lower risk of progression, respectively (HR=1.83, 95%CI=0.90-3.72, p=0.094 and HR=0.62, 95%CI=0.36-1.06, p=0.079), while high Akt1 and GLP-1R mRNA expression presented a trend towards unfavorable survival (HR=1.67, 95%CI=0.93-2.99, p=0.086 and HR=1.67, 95%CI=0.94-2.96, p=0.080). Among HER2-negative patients, high GLP-1R mRNA expression and negative stromal IGF-1Rβ protein expression showed a trend towards worse survival (HR=2.31, 95%CI=0.87-6.13, p=0.094 and HR=2.03, 95%CI=0.94-4.35, p=0.071, respectively). In the multivariate analyses, HER2-positive patients with high Akt1 and GLP-1R mRNA expression had a worse survival (HR=1.86, 95%CI=1.01-3.43, p=0.045 and HR=1.83, 95%CI=0.99-3.41, p=0.055, respectively).

CONCLUSION

This study revealed a crosstalk between the IGF-R pathway and HER2. There was evidence that high Akt1 and GLP-1R mRNA expression might affect survival among HER2-positive metastatic breast cancer patients treated with trastuzumab.

Protein arginine methyltransferase 7 promotes breast cancer cell invasion through the induction of MMP9 expression

Recent evidence points to the protein arginine methyltransferase (PRMT) family of enzymes playing critical roles in cancer. PRMT7 has been identified in several gene expression studies to be associated with increased metastasis and decreased survival in breast cancer patients. However, this has not been extensively studied. Here we report that PRMT7 expression is significantly upregulated in both primary breast tumour tissues and in breast cancer lymph node metastases. We have demonstrated that reducing PRMT7 levels in invasive breast cancer cells using RNA interference significantly decreased cell invasion in vitro and metastasis in vivo. Conversely, overexpression of PRMT7 in non-aggressive MCF7 cells enhanced their invasiveness. Furthermore, we show that PRMT7 induces the expression of matrix metalloproteinase 9 (MMP9), a well-known mediator of breast cancer metastasis. Importantly, we significantly rescued invasion of aggressive breast cancer cells depleted of PRMT7 by the exogenous expression of MMP9. Our results demonstrate that upregulation of PRMT7 in breast cancer may have a significant role in promoting cell invasion through the regulation of MMP9. This identifies PRMT7 as a novel and potentially significant biomarker and therapeutic target for breast cancer.

Crosstalk with insulin and dependence on PI3K/Akt/mTOR rather than MAPK pathways in upregulation of basal growth following long-term oestrogen deprivation in three human breast cancer cell lines

BACKGROUND

MCF-7, T-47-D, ZR-75-1 human breast cancer cell lines are dependent on oestrogen for growth but can adapt to grow during long-term oestrogen deprivation. This serves as a model for identification of therapeutic targets in endocrine-resistant breast cancer.

METHODS

An overlooked complication of this model is that it involves more than non-addition of oestrogen, and inadequate attention has been given to separating molecular events associated with each of the culture manipulations.

RESULTS

Insulin and oestradiol were shown to protect MCF-7 cells against upregulation of basal growth, demonstrating a crosstalk in the growth adaptation process. Increased phosphorylation of p44/42MAPK and c-Raf reflected removal of insulin from the medium and proliferation of all three cell lines was inhibited to a lesser extent by PD98059 and U0126 following long-term oestrogen/insulin withdrawal, demonstrating a reduced dependence on the MAPK pathway. By contrast, long-term oestrogen/insulin deprivation did not alter levels of phosphorylated Akt and did not alter the dose-response of growth inhibition with LY294002 in any of the three cell lines. The IGF1R inhibitor picropodophyllin inhibited growth of all MCF-7 cells but only in the long-term oestrogen/insulin-deprived cells was this paralleled by reduction in phosphorylated p70S6K, a downstream target of mTOR. Long-term oestrogen/insulin-deprived MCF-7 cells had higher levels of phosphorylated p70S6K and developed increased sensitivity to growth inhibition by rapamycin.

CONCLUSIONS

The greater sensitivity to growth inhibition by rapamycin in all three cell lines following long-term oestrogen/insulin deprivation suggests rapamycin-based therapies might be more effective in breast cancers with acquired oestrogen resistance.

Curcumin in VIP-targeted sterically stabilized phospholipid nanomicelles: a novel therapeutic approach for breast cancer and breast cancer stem cells

Breast cancer is a leading cause of cancer deaths among women in the US, with 40 % chance of relapse after treatment. Recent studies outline the role of cancer stem cells (CSCs) in tumor initiation, propagation, and regeneration of cancer. Moreover, it has been established that breast CSCs reside in a quiescent state that makes them more resistant to conventional cancer therapies than bulk cancer cells resulting in tumor relapse. In this study, we establish that CSCs are associated with the overexpression of vasoactive intestinal peptide (VIP) receptors which can be used to actively target these cells. We investigated the potential of using a novel curcumin nanomedicine (C-SSM) surface conjugated with VIP to target and hinder breast cancer with CSCs. Here, we formulated, characterized, and evaluated the feasibility of C-SSM nanomedicine in vitro. We investigated the cytotoxicity of C-SSM on breast cancer cells and CSCs by tumorsphere formation assay. Our results suggest that curcumin can be encapsulated in SSM up to 200 μg/ml with 1 mM lipid concentration. C-SSM nanomedicine is easy to prepare and maintains its original physicochemical properties after lyophilization, with an IC50 that is significantly improved from that of free curcumin (14.2±1.2 vs. 26.1±3.0 μM). Furthermore, C-SSM-VIP resulted in up to 20 % inhibition of tumorsphere formation at a dose of 5 μM. To this end, our findings demonstrate the feasibility of employing our actively targeted nanomedicine as a potential therapy for CSCs-enriched breast cancer.

Recent advances in the field of anti-cancer immunotherapy

Background

The main goal of anti-cancer therapy is to specifically inhibit the malignant activity of cancer cells, while leaving healthy cells unaffected. As such, for every proposed therapy, it is important to keep in mind the therapeutic index — the ratio of the toxic dose over the therapeutic dose. The use of immunotherapy has allowed a means to both specifically block protein–protein interaction and deliver cytotoxic events to a tumor-specific antigen.

Review scope

It is the objective of this review to give an overview on current immunotherapy treatment for cancers using monoclonal antibodies. We demonstrate three exciting targets for immunotherapy, TNF-α Converting Enzyme (TACE), Cathepsin S and Urokinase Plasmogen Activator and go over the advances made with one of the most used monoclonal antibodies in cancer therapy, Rituximab; as well as Herceptin, which is used for breast cancer therapy. Furthermore, we touch on other venues of immunotherapy, such as adaptive cell transfer, the use of nucleic acids and the use of dendritic cells. Finally, we summarize some ongoing studies that spell tentative advancements for anti-cancer immunotherapy.

General significance

Immunotherapy is at the forefront of anti-cancer therapies, allying both a high degree of specificity to general high effectiveness and fewer side-effects.

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Current monoclonal antibodies for cancer immunotherapy have a bright future.

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Immunotherapy presents opportunity to eliminate tumor growth that chemotherapy can't achieve.

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Therapeutic antibodies for cancer immunotherapy show better results without undesirable side-effects.

PET probes beyond (18)F-FDG

During the past several decades, positron emission tomography (PET) has been one of the rapidly growing areas of medical imaging; particularly, its applications in routine oncological practice have been widely recognized. At present, (18)F-fluorodeoxyglucose ((18)F-FDG) is the most broadly used PET probe. However, (18)F-FDG also suffers many limitations. Thus, scientists and clinicians are greatly interested in exploring and developing new PET imaging probes with high affinity and specificity. In this review, we briefly summarize the representative PET probes beyond (18)F-FDG that are available for patients imaging in three major clinical areas (oncology, neurology and cardiology), and we also discuss the feasibility and trends in developing new PET probes for personalized medicine.

Cannabidiol, a non-psychoactive cannabinoid compound, inhibits proliferation and invasion in U87-MG and T98G glioma cells through a multitarget effect

In the present study, we found that CBD inhibited U87-MG and T98G cell proliferation and invasiveness in vitro and caused a decrease in the expression of a set of proteins specifically involved in growth, invasion and angiogenesis. In addition, CBD treatment caused a dose-related down-regulation of ERK and Akt prosurvival signaling pathways in U87-MG and T98G cells and decreased hypoxia inducible factor HIF-1α expression in U87-MG cells. Taken together, these results provide new insights into the antitumor action of CBD, showing that this cannabinoid affects multiple tumoral features and molecular pathways. As CBD is a non-psychoactive phytocannabinoid that appears to be devoid of side effects, our results support its exploitation as an effective anti-cancer drug in the management of gliomas.

Receptor-mediated endocytosis for drug delivery in African trypanosomes: fulfilling Paul Ehrlich's vision of chemotherapy

Bloodstream-form cells of Trypanosoma brucei exhibit massively increased endocytic activity relative to the insect midgut stage, enabling rapid recycling of variant surface glycoprotein and antibody clearance from the surface. In addition, recent advances have identified a role for receptor-mediated endocytosis in the uptake of the antitrypanosomal drug, suramin, via invariant surface glycoprotein 75, and in the uptake of trypanosome lytic factor 1 via haptoglobin-haemoglobin receptor. Here, we argue that receptor-mediated endocytosis represents both a validated drug target and a promising route for the delivery of novel therapeutics into trypanosomes.

Combining mTOR Inhibitors with Chemotherapy and Other Targeted Therapies in Advanced Breast Cancer: Rationale, Clinical Experience, and Future Directions

Improvements in survival of patients with breast cancer have been attributed to the development of agents that target key components of dysregulated pathways involved in oncogenesis and progression of breast cancer. Aberrant mammalian target of rapamycin (mTOR) activation has been implicated in oncogenesis, angiogenesis, and the development of estrogen independence and resistance to chemotherapy in breast tumors. Several mTOR inhibitors (sirolimus, everolimus, temsirolimus, and ridaforolimus) have demonstrated antitumor activity in breast cancer cells. Combining mTOR inhibitors with endocrine therapies has demonstrated clinical antitumor activity in patients with metastatic breast cancer. In addition, mTOR inhibitor combinations with various targeted biologic agents or cytotoxic chemotherapeutic agents are being examined in more than 40 clinical trials with some early promising results. Combination therapies targeting multiple components of these central signaling pathways may be an optimal treatment strategy for patients with advanced breast cancer.

Plant cyclopeptide RA-V kills human breast cancer cells by inducing mitochondria-mediated apoptosis through blocking PDK1-AKT interaction

In the present paper, we examined the effects of a natural cyclopeptide RA-V on human breast cancer cells and the underlying mechanisms. RA-V significantly inhibited the growth of human breast cancer MCF-7, MDA-MB-231 cells and murine breast cancer 4T1 cells. In addition, RA-V triggered mitochondrial apoptotic pathway which was indicated by the loss of mitochondrial membrane potential, the release of cytochrome c, and the activation of caspase cascade. Further study showed that RA-V dramatically inhibited phosphorylation of AKT and 3-phosphoinositide dependent protein kinase 1 (PDK1) in MCF-7 cells. Moreover, RA-V disrupted the interaction between PDK1 and AKT in MCF-7 cells. Furthermore, RA-V-induced apoptosis could be enhanced by phosphatidylinositol 3-kinase inhibitor or attenuated by over-expression of AKT in all the three kinds of breast cancer cells. Taken together, this study shows that RA-V, which can induce mitochondria-mediated apoptosis, exerts strong anti-tumor activity against human breast cancer. The underlying anti-cancer mechanism of RA-V is related to the blockage of the interaction between PDK1 and AKT.

HER2/neu expression correlates with vasculogenic mimicry in invasive breast carcinoma

Vasculogenic mimicry (VM) refers to the condition in which tumour cells mimic endothelial cells to form extracellular matrix-rich tubular channels. VM is more extensive in more aggressive tumours. The human epidermal growth factor receptor 2 (HER2) gene is amplified in 20–30% of human breast cancers and has been implicated in mediating aggressive tumour growth and metastasis. However, thus far, there have been no data on the role of HER2 in VM formation. Immunohistochemical and histochemical double-staining methods were performed to display VM in breast cancer specimens. Transfection in MCF7 cells was performed and clones were selected by G418. The three-dimensional Matrigel culture was used to evaluate VM formation in the breast cancer cell line. According to statistical analysis, VM was related to the presence of a positive nodal status and advanced clinical stage. The positive rate of VM increased with increased HER2 expression. In addition, cases with HER2 3+ expression showed significantly greater VM channel count than those in other cases. The exogenous HER2 overexpression in MCF-7 cells induced vessel-like VM structures on the Matrigel and increased the VM mediator vascular endothelial (VE) cadherin. Our data provide evidence for a clinically relevant association between HER2 and VM in human invasive breast cancer. HER2 overexpression possibly induces VM through the up-regulation of VE cadherin. Understanding the key molecular events may provide therapeutic intervention strategies for HER2+ breast cancer.

Halogenated flavanones as potential apoptosis-inducing agents: synthesis and biological activity evaluation

A series of halogenated flavanones were synthesized from 2-hydroxychalcones and tested for their cytotoxicity against a panel of human cancer cell lines. Among the synthesized compounds, 3',7-dichloroflavanone (2d) showed the highest activity against MCF-7, LNCaP, PC3, Hep-G2, KB and SK-N-MC cells. However, 3',6-dichloroflavanone (2g) with IC(50) value of 2.9 ± 0.9 μM was the most potent compound against MDA-MB-231 cells, being approximately 12 times more active than etoposide as reference drug. According to the flow-cytometric analysis, compound 2g can induce apoptosis by 66.19 and 21.37% in PC3 and MDA-MB-231 cells, respectively. The results of acridine orange/ethidium bromide staining and TUNEL assay suggested that the cytotoxic activity of this compound in PC3 and MDA-MB-231 cells occurs via apoptosis.

Ligand-free estrogen receptor activity complements IGF1R to induce the proliferation of the MCF-7 breast cancer cells

Background

Ligand-dependent activation of the estrogen receptor (ER) as well as of the insulin-like growth factor type 1 (IGF1R) induces the proliferation of luminal breast cancer cells. These two pathways cooperate and are interdependent. We addressed the question of the mechanisms of crosstalk between the ER and IGF1R.

Methods

We evaluated the mitogenic effects of estradiol (E2; agonist ligand of ER) and of insulin (a ligand of IGF1R) in the MCF-7 cells by flow cytometry and by analyzing the cell levels of cell cycle-related proteins (immunoblotting) and mRNA (RT-QPCR). To verify the requirement for the kinase activity of Akt (a downstream target of IGF1R) in the mitogenic action of estradiol, we used shRNA strategy and shRNA-resistant expression vectors.

Results

The activation of the ER by E2 is unable to induce the cell cycle progression when the phosphatidyl inositol-3 kinase (PI3K)/Akt signaling is blocked by a chemical inhibitor (LY 294002) or by shRNA targeting Akt1 and Akt2. shRNA-resistant Akt wild-type constructs efficiently complemented the mitogenic signaling activity of E2 whereas constructs with inactivated kinase function did not. In growth factor-starved cells, the residual PI3K/Akt activity is sufficient to complement the mitogenic action of E2. Conversely, when ER function is blocked by the antiestrogen ICI 182780, IGF1R signaling is intact but does not lead to efficient reinitiation of the cell cycle in quiescent, growth factor-starved MCF-7 cells. The basal transcription-promoting activity of ligand-free ER in growth factor-starved cells is sufficient to complement the mitogenic action of the IGF1R-dependent signaling.

Conclusions

The basal ER activity in the absence of ligand is sufficient to allow efficient mitogenic action of IGF1R agonists and needs to be blocked to prevent the cell cycle progression.

Binding of trastuzumab to ErbB2 is inhibited by a high pericellular density of hyaluronan

Although trastuzumab is an efficient drug, primary and acquired resistance is a challenging problem. The authors have previously shown in mouse xenograft experiments that masking ErbB2 by hyaluronan leads to diminished binding of the antibody and consequent resistance. In the current work, they correlated trastuzumab binding with the pericellular density of hyaluronan in ErbB2-overexpressing human breast cancer samples. A method for quantifying the relative binding of trastuzumab was developed involving constant and low-frequency background subtraction, segmenting the image to membrane and background pixels followed by evaluation of trastuzumab fluorescence, normalized with the expression level of ErbB2, only in the membrane. The normalized binding of trastuzumab showed a negative correlation with the pericellular density of hyaluronan (r = -0.52) with the effect being the most pronounced in the extreme cases (i.e., low and high hyaluronan densities predicted strong and weak binding of trastuzumab, respectively). Removal of hyaluronan by hyaluronidase digestion unmasked the trastuzumab binding epitope of ErbB2 demonstrated by a significantly increased normalized binding of the antibody. The results show that the accumulation of pericellular hyaluronan plays a crucial role in masking ErbB2.

Schizophyllan inhibits the development of mammary and hepatic carcinomas induced by 7,12 dimethylbenz(α)anthracene and decreases cell proliferation: comparison with tamoxifen

BACKGROUND

Breast cancer is one of the leading causes of cancer mortality among women. Some anticancer compounds have been isolated from mushrooms. The aim of the present work was to study the anticancer effects of schizophyllan (SCH), a β-D: -glucan extracted from the mushroom Schizophyllum commune alone or in combination with tamoxifen (TAM) on 7, 12 Dimethylbenz(α)anthracene (DMBA)-induced carcinomas in mice.

METHODS

We isolated SCH from S. commune. Female mice received DMBA, SCH, DMBA+SCH, DMBA+TAM or DMBA+TAM+SCH or vehicles. We studied mice survival, tumour incidence, histopathology, oestrogen receptor (ER) expression, cell proliferation by immunohistochemical detection of proliferating cell nuclear antigen (PCNA), apoptosis by TUNEL assay, as well as caspase-3 expression.

RESULTS

DMBA treatment resulted in mammary and hepatocellular carcinomas (HCC). Both SCH and TAM reduced the incidence of DMBA-induced mammary tumours by 85 and 75 %, respectively, and equally decreased the PCNA labelling index relative to DMBA. TAM treatment increased the incidence of- and PCNA index in HCCs relative to DMBA, while SCH suppressed these effects. TAM was more effective than SCH in the induction of apoptosis in both mammary and hepatic carcinomas. Caspase-3 levels correlated with the apoptotic index in most experimental groups.

CONCLUSIONS

Only one dose of SCH had similar therapeutic effects against DMBA-induced mammary carcinomas as 4 weeks of TAM treatment. This coupled with the ability of SCH to suppress hepatic lesions associated with TAM treatment provides the rationale for further investigating the combined therapeutic effects of TAM+SCH in preclinical models of ER-positive breast cancer, as well as in liver cancer.

mTOR inhibitors in the management of hormone receptor-positive breast cancer: the latest evidence and future directions

BACKGROUND

There is an unmet therapeutic need in endocrine-resistant, hormone receptor (HR)-positive, human epidermal growth factor receptor 2-negative advanced breast cancer (BC). Preclinical studies support the hypothesis that the mammalian target of rapamycin (mTOR) inhibition could potentially overcome resistance to endocrine therapy.

MATERIALS AND METHODS

A literature review regarding BC and mTOR inhibitors was undertaken. The reference lists from retrieved manuscripts were reviewed to identify further studies.

RESULTS

Phase II studies have reported that the combination of mTOR inhibitors with endocrine therapy shows efficacy in patients with advanced disease that progressed after treatment with aromatase inhibitors. The recent findings of the phase III BOLERO-2 confirmed that everolimus in combination with exemestane significantly improved progression-free survival and response rate, with a manageable safety profile.

CONCLUSIONS

The addition of everolimus to exemestane for women with HR-positive metastatic BC is now considered a new therapeutic strategy. However, a word of caution should be added regarding toxic effects, which might limit practical use and compliance. It is essential that clinicians are educated about key recommendations for toxicity management and specific guideline dose modifications. Additional research efforts with the addition of these compounds in the early-stage setting is greatly needed to improve the survival of patients with HR-positive BC.

Phosphoproteomic analysis of leukemia cells under basal and drug-treated conditions identifies markers of kinase pathway activation and mechanisms of resistance

Protein kinase signaling is fundamental to cell homeostasis and is deregulated in all cancers but varies between patients. Understanding the mechanisms underlying this heterogeneity is critical for personalized targeted therapies. Here, we used a recently established LC-MS/MS platform to profile protein phosphorylation in acute myeloid leukemia cell lines with different sensitivities to kinase inhibitors. The compounds used in this study were originally developed to target Janus kinase, phosphatidylinositol 3-kinase, and MEK. After further validation of the technique, we identified several phosphorylation sites that were inhibited by these compounds but whose intensities did not always correlate with growth inhibition sensitivity. In contrast, several hundred phosphorylation sites that correlated with sensitivity/resistance were not in general inhibited by the compounds. These results indicate that markers of pathway activity may not always be reliable indicators of sensitivity of cancer cells to inhibitors that target such pathways, because the activity of parallel kinases can contribute to resistance. By mining our data we identified protein kinase C isoforms as one of such parallel pathways being more active in resistant cells. Consistent with the view that several parallel kinase pathways were contributing to resistance, inhibitors that target protein kinase C, MEK, and Janus kinase potentiated each other in arresting the proliferation of multidrug-resistant cells. Untargeted/unbiased approaches, such as the one described here, to quantify the activity of the intended target kinase pathway in concert with the activities of parallel kinase pathways will be invaluable to personalize therapies based on kinase inhibitors.

Increased signalling of EGFR and IGF1R, and deregulation of PTEN/PI3K/Akt pathway are related with trastuzumab resistance in HER2 breast carcinomas

Background:

Trastuzumab resistance hampers its well-known efficacy to control HER2-positive breast cancer. The involvement of PI3K/Akt pathway in this mechanism is still not definitively confirmed.

Methods:

We selected 155 patients treated with trastuzumab after development of metastasis or as adjuvant/neoadjuvant therapy. We performed immunohistochemistry for HER2, ER/PR, epidermal growth factor 1-receptor (EGFR), α-insulin-like growth factor 1-receptor (IGF1R), phosphatase and tensin homologue (PTEN), p110α, pAkt, pBad, pmTOR, pMAPK, MUC1, Ki67, p53 and p27; mutational analysis of PIK3CA and PTEN, and PTEN promoter hypermethylation.

Results:

We found 46% ER/PR-positive tumours, overexpression of EGFR (15%), α-IGF1R (25%), p110α (19%), pAkt (28%), pBad (22%), pmTOR (23%), pMAPK (24%), MUC1 (80%), PTEN loss (20%), and PTEN promoter hypermethylation (20%). PIK3CA and PTEN mutations were detected in 17% and 26% tumours, respectively. Patients receiving adjuvant trastuzumab with α-IGF1R or pBad overexpressing tumours presented shorter progression-free survival (PFS) (all P⩽0.043). Also, p110α and mTOR overexpression, liver and brain relapses implied poor overall survival (OS) (all P⩽0.041). In patients with metastatic disease, decreased PFS correlated with p110α expression (P=0.024), whereas for OS were the presence of vascular invasion and EGFR expression (P⩽0.019; Cox analysis).

Conclusion:

Our results support that trastuzumab resistance mechanisms are related with deregulation of PTEN/PI3K/Akt/mTOR pathway, and/or EGFR and IGF1R overexpression in a subset of HER2-positive breast carcinomas.

Array-based pharmacogenomics of molecular-targeted therapies in oncology

The advent of microarrays over the past decade has transformed the way genome-wide studies are designed and conducted, leading to an unprecedented speed of acquisition and amount of new knowledge. Microarray data have led to the identification of molecular subclasses of solid tumors characterized by distinct oncogenic pathways, as well as the development of multigene prognostic or predictive models equivalent or superior to those of established clinical parameters. In the field of molecular-targeted therapy for cancer, in particular, the application of array-based methodologies has enabled the identification of molecular targets with 'key' roles in neoplastic transformation or tumor progression and the subsequent development of targeted agents, which are most likely to be active in the specific molecular setting. Herein, we present a summary of the main applications of whole-genome expression microarrays in the field of molecular-targeted therapies for solid tumors and we discuss their potential in the clinical setting. An emphasis is given on deciphering the molecular mechanisms of drug action, identifying novel therapeutic targets and suitable agents to target them with, and discovering molecular markers/signatures that predict response to therapy or optimal drug dose for each patient.

The network interaction of the human cytosolic 90 kDa heat shock protein Hsp90: A target for cancer therapeutics

In the cell, proteins interact within a network in which a small number of proteins are highly connected nodes or hubs. A disturbance in the hub proteins usually has a higher impact on the cell physiology than a disturbance in poorly connected nodes. In eukaryotes, the cytosolic Hsp90 is considered to be a hub protein as it interacts with molecular chaperones and co-chaperones, and has key regulatory proteins as clients, such as transcriptional factors, protein kinases and hormone receptors. The large number of Hsp90 partners suggests that Hsp90 is involved in very important functions, such as signaling, proteostasis and epigenetics. Some of these functions are dysregulated in cancer, making Hsp90 a potential target for therapeutics. The number of Hsp90 interactors appears to be so large that a precise answer to the question of how many proteins interact with this chaperone has no definitive answer yet, not even if the question refers to specific Hsp90s as one of the human cytosolic forms. Here we review the major chaperones and co-chaperones that interact with cytosolic Hsp90s, highlighting the latest findings regarding client proteins and the role that posttranslational modifications have on the function and interactions of these molecular chaperones. This article is part of a Special Issue entitled: Proteomics: The clinical link.

PI3K/AKT pathway regulates phosphorylation of steroid receptors, hormone independence and tumor differentiation in breast cancer

Using a model of medroxyprogesterone acetate (MPA)-induced mouse mammary tumors that transit through different stages of hormone dependence, we previously reported that the activation of the phosphatidylinositol 3-kinase (PI3K)/AKT (protein kinase B) pathway is critical for the growth of hormone-independent (HI) mammary carcinomas but not for the growth of hormone-dependent (HD) mammary carcinomas. The objective of this work was to explore whether the activation of the PI3K/AKT pathway is responsible for the changes in tumor phenotype and for the transition to autonomous growth. We found that the inhibition of the PI3K/AKT/mTOR (mammalian target of rapamycin) pathway suppresses HI tumor growth. In addition, we were able to induce mammary tumors in mice in the absence of MPA by inoculating HD tumor cells expressing a constitutively active form of AKT1, myristoylated AKT1 (myrAKT1). These tumors were highly differentiated and displayed a ductal phenotype with laminin-1 and cytokeratin 8 expression patterns typical of HI tumors. Furthermore, myrAKT1 increased the tumor growth of IBH-6 and IBH-7 human breast cancer cell lines. In the estrogen-dependent IBH-7 cell line, myrAKT1 induced estrogen-independent growth accompanied by the expression of the adhesion markers focal adhesion kinase and E-cadherin. Finally, we found that cells expressing myrAKT1 exhibited increased phosphorylation of the progesterone receptor at Ser190 and Ser294 and of the estrogen receptor α at Ser118 and Ser167, independently of exogenous MPA or estrogen supply. Our results indicate that the activation of the PI3K/AKT/mTOR pathway promotes tissue architecture remodeling and the activation of steroid receptors.

Continuous requirement of ErbB2 kinase activity for loss of cell polarity and lumen formation in a novel ErbB2/Neu-driven murine cell line model of metastatic breast cancer

Background:

Well over a quarter of human breast cancers are ErbB2-driven and constitute a distinct subtype with substantially poorer prognosis. Yet, there are substantial gaps in our understanding of how ErbB2 tyrosine kinase activity unleashes a coordinated program of cellular and extracellular alterations that culminate in aggressive breast cancers. Cellular models that exhibit ErbB2 kinase dependency and can induce metastatic breast cancer in immune competent hosts are likely to help bridge this gap.

Materials and Methods:

Here, we derived and characterized a cell line model obtained from a transgenic ErbB2/Neu-driven mouse mammary adenocarcinoma.

Results:

The MPPS1 cell line produces metastatic breast cancers when implanted in the mammary fat pads of immune-compromised as well as syngeneic immune-competent hosts. MPPS1 cells maintain high ErbB2 overexpression when propagated in DFCI-1 or related media, and their growth is ErbB2-dependent, as demonstrated by concentration-dependent inhibition of proliferation with the ErbB kinase inhibitor Lapatinib. When grown in 3-dimensional (3-D) culture on Matrigel, MPPS1 cells predominantly form large irregular cystic and solid structures. Remarkably, low concentrations of Lapatinib led to a switch to regular acinar growth on Matrigel. Immunofluorescence staining of control vs. Lapatinib-treated acini for markers of epithelial polarity revealed that inhibition of ErbB2 signaling led to rapid resumption of normal mammary epithelium-like cell polarity.

Conclusions:

The strict dependence of the MPPS1 cell system on ErbB2 signals for proliferation and alterations in cell polarity should allow its use to dissect ErbB2 kinase-dependent signaling pathways that promote loss of cell polarity, a key component of the epithelial mesenchymal transition and aggressiveness of ErbB2-driven breast cancers.

Human epidermal growth factor receptor bispecific ligand trap RB200: abrogation of collagen-induced arthritis in combination with tumour necrosis factor blockade

Introduction

Rheumatoid arthritis (RA) is a chronic disease associated with inflammation and destruction of bone and cartilage. Although inhibition of TNFα is widely used to treat RA, a significant number of patients do not respond to TNFα blockade, and therefore there is a compelling need to continue to identify alternative therapeutic strategies for treating chronic inflammatory diseases such as RA. The anti-epidermal growth factor (anti-EGF) receptor antibody trastuzumab has revolutionised the treatment of patients with EGF receptor-positive breast cancer. Expression of EGF ligands and receptors (known as HER) has also been documented in RA. The highly unique compound RB200 is a bispecific ligand trap that is composed of full-length extracellular domains of HER1 and HER3 EGF receptors. Because of its pan-HER specificity, RB200 inhibits responses mediated by HER1, HER2 and HER3 in vitro and in vivo. The objective of this study was to assess the effect of RB200 combined with TNF blockade in a murine collagen-induced arthritis (CIA) model of RA.

Methods

Arthritic mice were treated with RB200 alone or in combination with the TNF receptor fusion protein etanercept. We performed immunohistochemistry to assess CD31 and in vivo fluorescent imaging using anti-E-selectin antibody labelled with fluorescent dye to elucidate the effect of RB200 on the vasculature in CIA.

Results

RB200 significantly abrogated CIA by reducing paw swelling and clinical scores. Importantly, low-dose RB200 combined with a suboptimal dose of etanercept led to complete abrogation of arthritis. Moreover, the combination of RB200 with etanercept abrogated the intensity of the E-selectin-targeted signal to the level seen in control animals not immunised to CIA.

Conclusions

The human pan-EGF receptor bispecific ligand trap RB200, when combined with low-dose etanercept, abrogates CIA, suggesting that inhibition of events downstream of EGF receptor activation, in combination with TNFα inhibitors, may hold promise as a future therapy for patients with RA.

The mTOR protein as a target in thyroid cancer

INTRODUCTION

The mammalian target of rapamycin (mTOR) protein is a downstream effector of the phosphatidilinositol-3 kinase (PI3K)/Akt pathway, which regulates not only cell proliferation and viability, but also iodide uptake in thyroid cells. Genetic alterations in the PI3K/Akt/mTOR pathway are common during thyroid cancer progression, and thus, these proteins are attractive targets for cancer therapy. So far, specific mTOR inhibitors, such as rapamycin analogs, have been developed and studied as anti-cancer agents.

AREAS COVERED

This review discusses evidence that justifies the potential use of mTOR signaling pathway inhibitors as therapeutic agents for thyroid cancer.

EXPERT OPINION

In the near future, mTOR-targeted drugs might represent a new approach for the therapy of thyroid cancer patients; rapamycin analogs have already been developed and are currently being clinically tested. Besides the antiproliferative action of mTOR inhibition, the stimulatory effect on thyroid iodide uptake can also be useful in the treatment of recurrent thyroid cancer. Therefore, if rapamycin analogs are able to increase iodide uptake in thyroid cancer, either alone or in combination with other agents, this will represent a new approach for the treatment of thyroid cancer, which may possibly improve the treatment of patients in which radioiodine therapy is not effective.

Optimal management of bone metastases in breast cancer patients

Bone metastasis in breast cancer is a significant clinical problem. It not only indicates incurable disease with a guarded prognosis, but is also associated with skeletal-related morbidities including bone pain, pathological fractures, spinal cord compression, and hypercalcemia. In recent years, the mechanism of bone metastasis has been further elucidated. Bone metastasis involves a vicious cycle of close interaction between the tumor and the bone microenvironment. In patients with bone metastases, the goal of management is to prevent further skeletal-related events, manage complications, reduce bone pain, and improve quality of life. Bisphosphonates are a proven therapy for the above indications. Recently, a drug of a different class, the RANK ligand antibody, denosumab, has been shown to reduce skeletal-related events more than the bisphosphonate, zoledronic acid. Other strategies of clinical value may include surgery, radiotherapy, radiopharmaceuticals, and, of course, effective systemic therapy. In early breast cancer, bisphosphonates may have an antitumor effect and prevent both bone and non-bone metastases. Whilst two important Phase III trials with conflicting results have led to controversy in this topic, final results from these and other key Phase III trials must still be awaited before a firm conclusion can be drawn about the use of bisphosphonates in this setting. Advances in bone markers, predictive biomarkers, multi-imaging modalities, and the introduction of novel agents have ushered in a new era of proactive management for bone metastases in breast cancer.

Akt, FoxO and regulation of apoptosis

Forkhead box O (FoxO) transcription factors are downstream targets of the serine/threonine protein kinase B (PKB)/Akt. The Akt kinase regulates processes of cellular proliferation and survival. Phosphorylation of FoxOs by Akt inhibits transcriptional functions of FoxOs and contributes to cell survival, growth and proliferation. Emerging evidence suggests involvement of FoxOs in diverse intracellular signaling pathways with critical roles in a number of physiological as well as pathological conditions including cancer. The FoxO signaling is regulated by their interactions with other intracellular proteins as well as their post-translational modifications such as phosphorylation. FoxOs promote cell growth inhibitory and/or apoptosis signaling by either inducing expression of multiple pro-apoptotic members of the Bcl2-family of mitochondria-targeting proteins, stimulating expression of death receptor ligands such as Fas ligand and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), or enhancing levels of various cyclin-dependent kinase inhibitors (CDKIs). Coupled with their ability to cross-talk with p53, FoxOs represent an important class of tumor suppressors in a variety of cancers. This review summarizes our current understanding of mechanisms by which Akt and FoxOs regulate cell growth and survival that in turn offers opportunities for development of novel strategies to combat cancer. This article is part of a Special Issue entitled: P13K-AKT-FOxO axis in cancer and aging.

PET/CT in cancer research: from preclinical to clinical applications

The identification of genetic and biochemical mechanisms underlying tumor growth and progression along with the unraveling of human genoma provided a plethora of new targets for cancer detection, treatment and monitoring. Simultaneously, the extraordinary development of a number of imaging technologies, including hybrid systems, allowed the visualization of biochemical, molecular and physiological aberrations linked to underlying mutations in a given tumor. In vivo evaluation of complex biological processes such as proliferation, apoptosis, angiogenesis, metastasis, gene expression, receptor-ligand interactions, transport of substrates and metabolism of nutrients in human cancers is feasible using PET/CT and radiolabeled molecular probes. Some of these compounds are in preclinical phases of evaluation whereas others have been already applied in clinical settings. Here we provide prominent examples on how some biological processes and target expression can be visualized by PET/CT in animal tumor models and cancer patients for the noninvasive detection of well-known markers of tumor aggressiveness, invasiveness and resistance to treatment and for the evaluation of tumor response to therapy.

Biological signalling activity measurements using mass spectrometry

MS (mass spectrometry) techniques are rapidly evolving to high levels of performance and robustness. This is allowing the application of these methods to the interrogation of signalling networks with unprecedented depth and accuracy. In the present review we discuss how MS-based multiplex quantification of kinase activities and phosphoproteomics provide complementary means to assess biological signalling activity. In addition, we discuss how a wider application of these analytical concepts to quantify kinase signalling will result in a more comprehensive understanding of normal and disease biology at the system level.

High incidence and frequency of LOH are associated with aggressive features of high-grade HER2 and triple-negative breast cancers

BACKGROUND

Basal-like and HER2-overexpressing breast carcinomas are histologically undifferentiated, high-grade tumors with a high proliferation rate and associated with a poor outcome. Most basal-like tumors lack the expression of ER, PR, and HER2 (triple-negative; TN). Loss of heterozygosity (LOH) is thought to reflect random chromosomal instability, and recent studies have shown that DNA-copy number alterations or LOH occur with a high frequency in basal-like and HER2-amplified tumors.

METHODS

The levels and patterns of LOH were analyzed by the microsatellite alteration analysis using fluorescence-labeled primers and an automated DNA sequencer at 5 randomly selected loci in 246 Japanese primary breast cancers. Associations between the level of LOH and breast cancer subtypes and tumor aggressiveness were investigated.

RESULTS

The incidence and frequency of LOH was significantly higher in HER2 (56.3, 26.7%) and TN groups (44.4, 27.1%) than in luminal A (ER-positive and/or PR-positive and HER2-negative) groups (32.0, 12.2%). The incidence and frequency of LOH increased as nuclear grade was elevated. There were significantly more grade 3 tumors in the HER2 (80.0%) and TN (68.2%) subgroups (p < 0.0001). Even in HER2 and TN cases, the incidence and frequency of LOH was significantly higher in nuclear grade 3 cases than in grade 1 or 2 cases. Relapse-free survival of patients with LOH was significantly shorter than for those without LOH. In addition, the survival time was shorter as the frequency of LOH elevated. The incidence of LOH was an independent prognostic factor for relapse-free survival by multivariate analysis.

CONCLUSION

High incidence and frequency of LOH, which indicate increased genetic instability, were found to be associated with the aggressive features of high-grade HER2 and TN breast cancers.

"Overcoming breast cancer drug resistance with mTOR inhibitors". Could it be a myth or a real possibility in the short-term future?

The mTOR pathway is pivotal not only in tumorigenesis but also in chemotherapy and hormonal drug sensitivity. It is clear that improvements in using new targeted therapies are required to improve breast cancer (BC) outcome. Nevertheless, to achieve this, new molecular biomarkers are required to define the potential sensitivity or resistance of cancer cells. By targeting the mTOR pathway, several critical central transduction pathways that sustain BC are abrogated (HER-2/Neu and the estrogen receptor pathway). Thus, the compounds that inhibit mTOR have a double mechanism of toxicity on BC cells when used in combination with a currently used drug: (1) overcoming primary drug resistance and (2) restoring sensitivity when resistance arises after long-term exposure. This review covers the utility of inhibitors of the mTOR pathway in BC and emphasizes the new paradigm of close symbiosis between oncology and molecular biology to better profiling and treating BC with a targeted approach. In particular, we focused on the new drug RAD001 (Everolimus) due to the great results from preclinical and clinical trials make it the most hopeful compound among mTOR inhibitors for the treatment of BC.

Targeting DNA replication before it starts: Cdc7 as a therapeutic target in p53-mutant breast cancers

Treatment options for triple-receptor negative (ER-/PR-/Her2-) and Her2-overexpressing (ER-/PR-/Her2+) breast cancers with acquired or de novo resistance are limited, and metastatic disease remains incurable. Targeting of growth signaling networks is often constrained by pathway redundancy or growth-independent cancer cell cycles. The cell-cycle protein Cdc7 regulates S phase by promoting DNA replication. This essential kinase acts as a convergence point for upstream growth signaling pathways and is therefore an attractive therapeutic target. We show that increased Cdc7 expression during mammary tumorigenesis is linked to Her2-overexpressing and triple-negative subtypes, accelerated cell cycle progression (P < 0.001), arrested tumor differentiation (P < 0.001), genomic instability (P = 0.019), increasing NPI score (P < 0.001), and reduced disease-free survival (HR = 1.98 [95% CI: 1.27-3.10]; P = 0.003), thus implicating its deregulation in the development of aggressive disease. Targeting Cdc7 with RNAi, we demonstrate that p53-mutant Her2-overexpressing and triple-negative breast cancer cell lines undergo an abortive S phase and apoptotic cell death due to loss of a p53-dependent Cdc7-inhibition checkpoint. In contrast, untransformed breast epithelial cells arrest in G1, remain viable, and are able to resume cell proliferation on recovery of Cdc7 kinase activity. Thus, Cdc7 appears to represent a potent and highly specific anticancer target in Her2-overexpressing and triple-negative breast cancers. Emerging Cdc7 kinase inhibitors may therefore significantly broaden the therapeutic armamentarium for treatment of the aggressive p53-mutant breast cancer subtypes identified in this study.

The prevalence and assessment of ErbB2-positive breast cancer in Asia: a literature survey

Overexpression of the epidermal growth factor receptor-related gene ErbB2 occurs in 18% to 25% of patients with breast cancer in Western countries and is associated with a poor prognosis. The prevalence of ErbB2-positive tumors in Asia is unclear, partly because data are limited. The objective of this review was to summarize the reported prevalence of ErbB2-positive tumors from a large sample of Asian patients and to examine ErbB2 assessment methods in Asia. From searches of MEDLINE, local language journals, and local and international conference proceedings as well as locoregional breast cancer experts' recommendations, the authors selected up to 5 studies each from India, Korea, Malaysia, the Philippines, Singapore, Taiwan, and Thailand that reported ErbB2 results based on assessment with immunohistochemistry (IHC) and/or fluorescence in situ hybridization (FISH). The reported prevalence of ErbB2-positive tumors in 22 studies on 24,671 patients, of whom 14,398 patients were assessed for ErbB2 status, varied widely (range, 6%-65%) as did the assessment methods used. Most studies (n = 21) used IHC to assess ErbB2 status, but definitions for positivity varied. When robust assessment methods were used, the median prevalence was 19% based on strong IHC staining (IHC3+; n = 9812 patients) and 25% based on FISH (n = 681 patients). Data on the prevalence of ErbB2-positive breast cancer in Asia are limited. The current survey indicated that the prevalence in Asia may be similar to that in Western countries; thus, up to 1 in 4 Asian patients with breast cancer potentially could benefit from ErbB2-targeted treatment. A standard, reliable ErbB2 assessment method available to patients across Asia is urgently required. Cancer 2010;116:5348–57. © 2010 American Cancer Society.

VRK2 inhibits mitogen-activated protein kinase signaling and inversely correlates with ErbB2 in human breast cancer

The epidermal growth factor (EGF)-ErbB-mitogen-activated protein kinase (MAPK) transcription signaling pathway is altered in many types of carcinomas, and this pathway can be regulated by new protein-protein interactions. Vaccinia-related kinase (VRK) proteins are Ser-Thr kinases that regulate several signal transduction pathways. In this work, we study the effect of VRK2 on MAPK signaling using breast cancer as a model. High levels of VRK2 inhibit EGF and ErbB2 activation of transcription by the serum response element (SRE). This effect is also detected in response to H-Ras(G12V) or B-Raf(V600E) oncogenes and is accompanied by a reduction in phosphorylated extracellular signal-regulated kinase (ERK) levels, p90RSK levels, and SRE-dependent transcription. Furthermore, VRK2 knockdown has the opposite effect, increasing the transcriptional response to stimulation with EGF and leading to increased levels of ERK phosphorylation. The molecular mechanism lies between MAPK/ERK kinase (MEK) and ERK, since MEK remains phosphorylated while ERK phosphorylation is blocked by VRK2A. This inhibition of the ERK signaling pathway is a consequence of a direct protein-protein interaction between VRK2A, MEK, and kinase suppressor of Ras 1 (KSR1). Identification of new correlations in human cancer can lead to a better understanding of the biology of individual tumors. ErbB2 and VRK2 protein levels were inversely correlated in 136 cases of human breast carcinoma. In ErbB2(+) tumors, there is a significant reduction in the VRK2 level, suggesting a role for VRK2A in ErbB2-MAPK signaling. Thus, VRK2 downregulation in carcinomas permits signal transmission through the MEK-ERK pathway without affecting AKT signaling, causing a signal imbalance among pathways that contributes to the phenotype of breast cancer.

Cannabinoids reduce ErbB2-driven breast cancer progression through Akt inhibition

Background

ErbB2-positive breast cancer is characterized by highly aggressive phenotypes and reduced responsiveness to standard therapies. Although specific ErbB2-targeted therapies have been designed, only a small percentage of patients respond to these treatments and most of them eventually relapse. The existence of this population of particularly aggressive and non-responding or relapsing patients urges the search for novel therapies. The purpose of this study was to determine whether cannabinoids might constitute a new therapeutic tool for the treatment of ErbB2-positive breast tumors. We analyzed their antitumor potential in a well established and clinically relevant model of ErbB2-driven metastatic breast cancer: the MMTV-neu mouse. We also analyzed the expression of cannabinoid targets in a series of 87 human breast tumors.

Results

Our results show that both Δ⁹-tetrahydrocannabinol, the most abundant and potent cannabinoid in marijuana, and JWH-133, a non-psychotropic CB₂ receptor-selective agonist, reduce tumor growth, tumor number, and the amount/severity of lung metastases in MMTV-neu mice. Histological analyses of the tumors revealed that cannabinoids inhibit cancer cell proliferation, induce cancer cell apoptosis, and impair tumor angiogenesis. Cannabinoid antitumoral action relies, at least partially, on the inhibition of the pro-tumorigenic Akt pathway. We also found that 91% of ErbB2-positive tumors express the non-psychotropic cannabinoid receptor CB₂.

Conclusions

Taken together, these results provide a strong preclinical evidence for the use of cannabinoid-based therapies for the management of ErbB2-positive breast cancer.

Post-transcriptional mechanisms contribute to the suppression of the ErbB3 negative regulator protein Nrdp1 in mammary tumors

The ErbB2 and ErbB3 receptor tyrosine kinases act synergistically to promote cellular properties associated with tumor development. Previous studies indicate that endogenous ErbB3 protein is markedly elevated in mouse mammary tumors induced by transgenic ErbB2 overexpression. However, this occurs in the absence of elevated ErbB3 transcript, indicating that post-transcriptional regulatory mechanisms play crucial roles in suppressing ErbB3 protein in normal tissue. Our previous studies also demonstrate that protein levels of Nrdp1, an E3 ubiquitin ligase that targets ErbB3 for degradation, are markedly suppressed in tumors from ErbB2 transgenic animals relative to normal tissue. Here we demonstrate that transgenic expression of Nrdp1 cDNA in the mouse mammary gland is not sufficient to suppress elevated ErbB3 levels or tumor initiation and growth in ErbB2 transgenic mice. Unexpectedly, Nrdp1 protein is absent in tumors from Nrdp1/ErbB2 bigenic mice, and real time PCR analysis indicates that Nrdp1 protein levels are suppressed post-transcriptionally. Nrdp1 protein is more resistant to proteasome-dependent degradation when exogenously expressed in cultured MCF10A nontransformed human breast epithelial cells than in breast tumor cells. These observations indicate that mammary tumors use potent post-transcriptional mechanisms to suppress Nrdp1 protein levels and that protein destabilization may play a central role in Nrdp1 loss in tumors.

Opportunities for PET to deliver clinical benefit in cancer: breast cancer as a paradigm

The glucose analogue fluorodeoxyglucose (FDG) has demonstrated enhanced uptake in the majority of tumours as a result of increased uptake and fixation by phosphorylation. It is the most widely used radiotracer in positron emission tomography (PET), being used in >90% of scans, and is useful for diagnosis, staging and detection of residual/recurrent cancer. However, there are limits to the utility of FDG, particularly in certain tumour types. The development of new radiotracers to study molecular processes such as proliferation, apoptosis, angiogenesis and hypoxia will complement FDG by providing additional information on the cell biology of tumours. The aim of this paper is to consider how the availability of new tracers, or new applications for existing PET/CT technologies, could deliver clinical benefit in cancer, using breast cancer as a paradigm.

Gene expression profiling of response to mTOR inhibitor everolimus in pre-operatively treated post-menopausal women with oestrogen receptor-positive breast cancer

There is growing evidence that uncontrolled activation of the PI3K/Akt/mTOR pathway contributes to the development and progression of breast cancer. Inhibition of this pathway has antitumour effects in preclinical studies and efficacy in combination with other agents in breast cancer patients. The aim of this study is to characterise the effects of pre-operative everolimus treatment in primary breast cancer patients and to identify potential molecular predictors of response. Twenty-seven patients with oestrogen receptor (ER)-positive breast cancer completed 11-14 days of neoadjuvant treatment with 5-mg everolimus. Core biopsies were taken before and after treatment and analysed using Illumina HumanRef-8 v2 Expression BeadChips. Changes in proliferation (Ki67) and phospho-AKT were measured on diagnostic core biopsies/resection samples embedded in paraffin by immunohistochemistry to determine response to treatment. Patients that responded to everolimus treatment with significant reductions in proliferation (fall in % Ki67 positive cells) also had significant decreases in the expression of genes involved in cell cycle (P = 8.70E-09) and p53 signalling (P = 0.01) pathways. Highly proliferating tumours that have a poor prognosis exhibited dramatic reductions in the expression of cell cycle genes following everolimus treatment. The genes that most clearly separated responding from non-responding pre-treatment tumours were those involved with protein modification and dephosphorylation, including DYNLRB2, ERBB4, PTPN13, ULK2 and DUSP16. The majority of ER-positive breast tumours treated with everolimus showed a significant reduction in genes involved with proliferation, these may serve as markers of response and predict which patients will derive most benefit from mTOR inhibition.