Can molecular markers predict when to implement treatment with aromatase inhibitors in invasive breast cancer?

Endosomal recycling inhibitors downregulate estrogen receptor-alpha and synergise with endocrine therapies

PURPOSE

Breast cancer (BC) accounts for roughly 30% of new cancers diagnosed in women each year; thus, this cancer type represents a substantial burden for people and health care systems. Despite the existence of effective therapies to treat BC, drug resistance remains a problem and is a major cause of treatment failure. Therefore, new drugs and treatment regimens are urgently required to overcome resistance. Recent research indicates that inhibition of the endosomal recycling pathway, an intracellular membrane trafficking pathway that returns endocytosed proteins back to the plasma membrane, may be a promising strategy to downregulate clinically relevant cell surface proteins such as HER2 and HER3, and to overcome drug resistance.

METHODS

To investigate the molecular mechanism of action of an endosomal recycling inhibitor (ERI) called primaquine, we performed a reverse-phase protein array (RPPA) assay using a HER2-positive breast cancer cell line. The RPPA findings were confirmed by Western blot and RT-qPCR in several BC cell lines. Novel drug combinations were tested by MTT cell viability and clonogenic assays.

RESULTS

Among the signalling molecules downregulated by ERIs were estrogen receptor-alpha (ER-α) and androgen receptor. We confirmed this finding in other breast cancer cell lines and show that downregulation occurs at the transcriptional level. We also found that ERIs synergise with tamoxifen, a standard-of-care therapy for breast cancer.

DISCUSSION

Our data suggest that combining ERIs with hormone receptor antagonists may enhance their efficacy and reduce the emergence of drug resistance.

HER3: Toward the Prognostic Significance, Therapeutic Potential, Current Challenges, and Future Therapeutics in Different Types of Cancer

Human epidermal growth factor receptor 3 (HER3) is the only family member of the EGRF/HER family of receptor tyrosine kinases that lacks an active kinase domain (KD), which makes it an obligate binding partner with other receptors for its oncogenic role. When HER3 is activated in a ligand-dependent (NRG1/HRG) or independent manner, it can bind to other receptors (the most potent binding partner is HER2) to regulate many biological functions (growth, survival, nutrient sensing, metabolic regulation, etc.) through the PI3K-AKT-mTOR pathway. HER3 has been found to promote tumorigenesis, tumor growth, and drug resistance in different cancer types, especially breast and non-small cell lung cancer. Given its ubiquitous expression across different solid tumors and role in oncogenesis and drug resistance, there has been a long effort to target HER3. As HER3 cannot be targeted through its KD with small-molecule kinase inhibitors via the conventional method, pharmaceutical companies have used various other approaches, including blocking either the ligand-binding domain or extracellular domain for dimerization with other receptors. The development of treatment options with anti-HER3 monoclonal antibodies, bispecific antibodies, and different combination therapies showed limited clinical efficiency for various reasons. Recent reports showed that the extracellular domain of HER3 is not required for its binding with other receptors, which raises doubt about the efforts and applicability of the development of the HER3-antibodies for treatment. Whereas HER3-directed antibody-drug conjugates showed potentiality for treatment, these drugs are still under clinical trial. The currently understood model for dimerization-induced signaling remains incomplete due to the absence of the crystal structure of HER3 signaling complexes, and many lines of evidence suggest that HER family signaling involves more than the interaction of two members. This review article will significantly expand our knowledge of HER3 signaling and shed light on developing a new generation of drugs that have fewer side effects than the current treatment regimen for these patients.

Hormone receptors in breast cancer: An update on the uncommon subtypes

Breast cancer is the most common cancer affecting women and is the second leading cause of cancer death among US women. Estrogen receptor (ER) signaling plays a crucial role in mammary gland development and carcinogenesis. Near 80 % of invasive breast cancers are ER-positive (ER+). Endocrine therapies targeting ER have significantly improved the prognostic outcomes in the patients with ER+ breast cancer, and the therapeutic effects are strongly correlated with the levels of the ER expression in tumor cells. Despite being an ER-dependent gene product, PR is not always overexpressed in ER+ tumors, and a small subset of breast cancers demonstrates an ER+/PR- phenotype, and a rare ER-/PR+ subtype also exists. There have been controversies on the biology of these tumor types and the predictive and prognostic power of PR status. Compelling data have shown the distinct biologic characteristics of ER+/PR- and ER-/PR+ tumors. Despite that ER-low breast cancers demonstrate more similarity to ER- tumors, at least a subset of ER-low carcinomas may have a functional ER signaling. Thus, adequate PR expression is essential as its absence indicates impaired ER pathway. Assessment of PR status may not only distinguish the ER+/PR- subset from the ER+ and ER-low tumors, but also differentiate the ER-/PR+ phenotype from the ER- carcinomas, both with therapeutic implications. This article was aimed to provide an up-to-date review focusing on the clinicopathologic characteristics of uncommon subtypes of breast cancer, including ER+/PR-, ER-/PR+, and ER-low breast cancers.

Epithelial-specific ERBB3 deletion results in a genetic background-dependent increase in intestinal and colon polyps that is mediated by EGFR

ERBB3 has gained attention as a potential therapeutic target to treat colorectal and other types of cancers. To confirm a previous study showing intestinal polyps are dependent upon ERBB3, we generated an intestinal epithelia-specific ERBB3 deletion in C57BL/6-ApcMin/+ mice. Contrary to the previous report showing a significant reduction in intestinal polyps with ablation of ERBB3 on a B6;129 mixed genetic background, we observed a significant increase in polyp number with ablation of ERBB3 on C57BL/6J compared to control littermates. We confirmed the genetic background dependency of ERBB3 by also analyzing polyp development on B6129 hybrid and B6;129 advanced intercross mixed genetic backgrounds, which showed that ERBB3 deficiency only reduced polyp number on the mixed background as previously reported. Increased polyp number with ablation of ERBB3 was also observed in C57BL/6J mice treated with azoxymethane showing the effect is model independent. Polyps forming in absence of ERBB3 were generally smaller than those forming in control mice, albeit the effect was greatest in genetic backgrounds with reduced polyp numbers. The mechanism for differential polyp number in the absence of ERBB3 was through altered proliferation. Backgrounds with increased polyp number with loss of ERBB3 showed an increase in cell proliferation even in non-tumor epithelia, while backgrounds showing reduced polyp number with loss of ERBB3 showed reduced cellular proliferation. Increase polyp number caused by loss of ERBB3 was mediated by increased epidermal growth factor receptor (EGFR) expression, which was confirmed by deletion of Egfr. Taken together, this study raises substantial implications on the use of ERBB3 inhibitors against colorectal cancer. The prediction is that some patients may have increased progression with ERBB3 inhibitor therapy, which is consistent with observations reported for ERBB3 inhibitor clinical trials.

Hormone Resistance

Hormone therapy is a major therapy for hormone receptor-positive breast cancer that improves survival. However, despite these hormone treatments, there are de novo or acquired resistance of breast cancer. Many studies revealed these resistance mechanisms, which are related to hormonal receptors including low expression or mutation of estrogen receptor alpha(ERα), co-factors and progesterone receptor, and with activation of growth signaling pathways such as PIK3A/Akt/mTOR pathway or cell cycle pathway. To overcome endocrine resistance based on these mechanisms, there have been many efforts in clinical studies of new agents which are representative of steroidal selective estrogen receptor down-regulator, cyclin-dependent kinase (CDK) 4/6 inhibitors, inhibitors of the PI3K/AKT/mTOR Pathway and histone deacetylase (HDAC) Inhibitors. Our studies at LBCB focused the endocrine resistance in young age and showed that age under 35 years is poor prognostic factor on not only single-center data but also Korean Breast Cancer Registry Data and that women with hormone receptor-positive breast cancer who were younger than 35 years of age had less response to anti-hormonal therapy. Also, a study for gene expression in hormone receptor-positive breast cancer at a very young age (<35) revealed that expression of cell cycle-related genes increased higher than that of premenopausal women in their forties. There have been a lot of studies and clinical trials to investigate the mechanisms of resistance to endocrine treatment and to overcome them with new drugs. However, many still do not know the precise mechanism of recurrence of breast cancer after endocrine treatment. In particular, the identification of the mechanism of endocrine resistance in young women, and the combination of drugs and clinical trials to overcome this require much effort.

Thirty Years of HER3: From Basic Biology to Therapeutic Interventions

HER3 is a pseudokinase member of the EGFR family having a role in both tumor progression and drug resistance. Although HER3 was discovered more than 30 years ago, no therapeutic interventions have reached clinical approval to date. Because the evidence of the importance of HER3 is accumulating, increased amounts of preclinical and clinical trials with HER3-targeting agents are emerging. In this review article, we discuss the most recent HER3 biology in tumorigenic events and drug resistance and provide an overview of the current and emerging strategies to target HER3.

Heregulin Drives Endocrine Resistance by Altering IL-8 Expression in ER-Positive Breast Cancer

Sustained HER2/HER3 signaling due to the overproduction of the HER3 ligand heregulin (HRG) is proposed as a key contributor to endocrine resistance in estrogen receptor-positive (ER+) breast cancer. The molecular mechanisms linking HER2 transactivation by HRG-bound HER3 to the acquisition of a hormone-independent phenotype in ER+ breast cancer is, however, largely unknown. Here, we explored the possibility that autocrine HRG signaling drives cytokine-related endocrine resistance in ER+ breast cancer cells. We used human cytokine antibody arrays to semi-quantitatively measure the expression level of 60 cytokines and growth factors in the extracellular milieu of MCF-7 cells engineered to overexpress full-length HRGβ2 (MCF-7/HRG cells). Interleukin-8 (IL-8), a chemokine closely linked to ER inaction, emerged as one the most differentially expressed cytokines. Cytokine profiling using structural deletion mutants lacking both the N-terminus and the cytoplasmic-transmembrane region of HRGβ2-which is not secreted and cannot transactivate HER2-or lacking a nuclear localization signal at the N-terminus-which cannot localize at the nucleus but is actively secreted and transactivates HER2-revealed that the HRG-driven activation of IL-8 expression in ER+ cells required HRG secretion and transactivation of HER2 but not HRG nuclear localization. The functional blockade of IL-8 with a specific antibody inversely regulated ERα-driven transcriptional activation in endocrine-sensitive MCF-7 cells and endocrine-resistant MCF-7/HRG cells. Overall, these findings suggest that IL-8 participates in the HRG-driven endocrine resistance program in ER+/HER2- breast cancer and might illuminate a potential clinical setting for IL8- or CXCR1/2-neutralizing antibodies.

HER family in cancer progression: From discovery to 2020 and beyond

The human epidermal growth factor receptor (HER) family of receptor tyrosine kinases (RTKs) are among the first layer of molecules that receive, interpret, and transduce signals leading to distinct cancer cell phenotypes. Since the discovery of the tooth-lid factor-later characterized as the epidermal growth factor (EGF)-and its high-affinity binding EGF receptor, HER kinases have emerged as one of the commonly upregulated or hyperactivated or mutated kinases in epithelial tumors, thus allowing HER1-3 family members to regulate several hallmarks of cancer development and progression. Each member of the HER family exhibits shared and unique structural features to engage multiple receptor activation modes, leading to a range of overlapping and distinct phenotypes. EGFR, the founding HER family member, provided the roadmap for the development of the cell surface RTK-directed targeted cancer therapy by serving as a prototype/precursor for the currently used HER-directed cancer drugs. We herein provide a brief account of the discoveries, defining moments, and historical context of the HER family and guidepost advances in basic, translational, and clinical research that solidified a prominent position of the HER family in cancer research and treatment. We also discuss the significance of HER3 pseudokinase in cancer biology; its unique structural features that drive transregulation among HER1-3, leading to a superior proximal signaling response; and potential role of HER3 as a shared effector of acquired therapeutic resistance against diverse oncology drugs. Finally, we also narrate some of the current drawbacks of HER-directed therapies and provide insights into postulated advances in HER biology with extensive implications of these therapies in cancer research and treatment.

Single hormone receptor-positive breast cancer patients experienced poor survival outcomes: a systematic review and meta-analysis

BACKGROUND

The prognostic and clinical significance of single hormone receptor expression in breast cancer has not been clearly established. The goal of this study was to conduct a meta-analysis to compare the clinical outcomes of patients with ER+PR- tumours and ER-PR+ tumours to those of patients with ER+PR+ tumours.

METHODS

A systematic review of the literature was conducted to identify studies that compared the clinical outcome of patients with ER+PR- tumours or ER-PR+ tumours with those of patients with ER+PR+ tumours. A total of 18 studies met the inclusion criteria and included 217,485 women. Standard methods for meta-analysis were used, including fixed-effect models.

RESULTS

Patients with ER+PR- tumours or ER-PR+ tumours had significantly worse DFS (HR 1.60, 95% CI 1.44-1.77 and HR 2.27, 95% CI 1.67-3.09), BCSS (HR 1.43, 95% CI 1.33-1.53 and HR 1.82, 95% CI 1.68-1.98) and OS (HR 1.38, 95% CI 1.28-1.47 and HR 1.48, 95% CI 1.17-1.89) than those of patients with ER+PR+ tumours. In subgroup analyses, patients who had ER+PR- tumours experienced a higher risk of recurrence than patients with ER+PR+ tumours in the HER2- (HR 1.57, 95% CI 1.32-1.87), LN - (HR 2.07, 95% CI 1.44-2.86) and endocrine therapy (HR 1.65, 95% CI 1.45-1.89) subgroup. Patients who had HER2- and ER-PR+ tumours had an increased risk of recurrence compared with patients who had HER2- and ER+PR+ tumours (HR 3.10, 95% CI 1.92-5.10).

CONCLUSIONS

Among patients with hormone receptor-positive breast cancer, patients with either ER+PR- tumours or ER-PR+ tumours have a higher risk of recurrence and a shorter survival time than those with ER+PR+ tumours. Patients with both types of breast cancer need additional or better treatments.

An NF-κB signature predicts low-grade glioma prognosis: a precision medicine approach based on patient-derived stem cells

Background

While recent genome-wide association studies have suggested novel low-grade glioma (LGG) stratification models based on a molecular classification, we explored the potential clinical utility of patient-derived cells. Specifically, we assayed glioma-associated stem cells (GASC) that are patient-derived and representative of the glioma microenvironment.

Methods

By next-generation sequencing, we analyzed the transcriptional profile of GASC derived from patients who underwent anaplastic transformation either within 48 months (GASC-BAD) or ≥7 years (GASC-GOOD) after surgery. Gene set enrichment and pathway enrichment analyses were applied. The prognostic role of a nuclear factor-kappaB (NF-κB) signature derived from GASC-BAD was tested in 530 newly diagnosed diffuse LGG patients comprised within The Cancer Genome Atlas (TCGA) database. The prognostic value of the GASC upstream regulator p65 NF-κB was assessed, by univariate and multivariate Cox analyses, in a single center case study, including 146 grade II LGGs.

Results

The key elements differentiating the transcriptome of GASC isolated from LGG with different prognoses were mostly related to hallmarks of cancer (eg, inflammatory/immune process, NF-κB activation). Consistently, the NF-κB signature extrapolated from the GASC study was prognostic in the dataset of TCGA. Finally, the nuclear expression of the NF-kB-p65 protein, assessed using an inexpensive immunohistochemical method, was an independent predictor of both overall survival and malignant progression-free survival in 146 grade II LGGs.

Conclusion

This study demonstrates for the first time the independent prognostic role of NF-kB activation in LGG and outlines the role of patient-based stem cell models as a tool for precision medicine approaches.

USP1 (ubiquitin specific peptidase 1) targets ULK1 and regulates its cellular compartmentalization and autophagy

ULK1 (unc-51 like autophagy activating kinase 1) is a core component at multiple steps of canonical macroautophagy/autophagy. The activity of ULK1 is tightly regulated by several post-translational modifications, including ubiquitination, yet the deubiquitinase (DUB) responsible for its reversible deubiquitination has not been described. Here, we identified USP1 (ubiquitin specific peptidase 1) as a key player in the modulation of ULK1 K63-linked deubiquitination. Moreover, both USP1 depletion and its chemical inhibition by pimozide are coupled to a reduction of ULK1 in Triton X-100 soluble cellular lysates, and its compartmentalization to a fraction that can be solubilized in 5 M urea. In USP1-depleted cells this fraction is also enriched in SQSTM1 (sequestosome 1), the aggresome marker HDAC6 (histone deacetylase 6), and the prototype of USP1 targets FANCD2 (FA complementation group D2). Consistently, in USP1-depleted and pimozide-treated cells, ULK1 forms protein aggregates enriched in SQSTM1, as detected by both immummunofluorescence and co-immunoprecipitation studies. Notably, depletion of USP1 inhibits canonical autophagic flux and promotes an alternative route leading to lysosomal-mediated degradation of SQSTM1. Our findings reveal a novel function of the USP1-ULK1 axis as a modulator of the switch between canonical and unconventional autophagy. Further, we provide the first evidence supporting the existence of a subset of breast tumors co-expressing ULK1 and MAP1LC3B (microtubule associated protein 1 light chain 3 beta) proteins. Because the USP1 inhibitor pimozide affects breast cancer cell growth, targeting USP1 in those tumors relying on autophagy for growth might prove to be a convenient therapeutic strategy. Abbreviations: ATG13: autophagy related 13; BECN1: beclin 1; BZ: bortezomib; CAPN1: calpain 1; DUB: deubiquitinase; FANCI: FA complementation group I; FANCD2: FA complementation group D2; FZR1: fizzy and cell division cycle 20 related 1; HDAC6: histone deacetylase 6; MAP1LC3B: microtubule associated protein 1 light chain 3 beta; PMZ: pimozide; SH3GLB1: SH3 domain containing GRB2 like, endophilin B1; SQSTM1: sequestosome 1; TRAF6: TNF receptor associated factor 6; ULK1: unc-51 like autophagy activating kinase 1; USP1: ubiquitin specific peptidase 1; WDR48: WD repeat domain 48.

Clinical development of HER3-targeting monoclonal antibodies: Perils and progress

The human epidermal growth factor receptor (HER) family consists of four transmembrane receptor tyrosine kinases: epidermal growth factor receptor (EGFR), HER2, HER3, and HER4. They are part of a complex signalling network and stimulate intracellular pathways regulating cell growth and differentiation. So far, monoclonal antibodies (mAbs) and small molecule tyrosine kinase inhibitors targeting EGFR and HER2 have been developed and approved. Recently, focus has turned to HER3 as it may play an important role in resistance to EGFR- and HER2-targeting therapies. HER3-targeting agents have been undergoing clinical evaluation for the last 10 years and currently thirteen mAbs are in phase 1 or 2 clinical studies. Single agent activity has proven to be limited, however, the tolerability was favourable. Thus, combinations of HER3-binding mAbs with other HER-targeting therapies or chemotherapies have been pursued in various solid tumor entities. Data indicate that the HER3-binding ligand heregulin may serve as a response prediction marker for HER3-targeting therapy. Within this review the current status of clinical development of HER3-targeting compounds is described.

HER3 signaling and targeted therapy in cancer

ERBB family members including epidermal growth factor receptor (EGFR) also known as HER1, ERBB2/HER2/Neu, ERBB3/HER3 and ERBB4/HER4 are aberrantly activated in multiple cancers and hence serve as drug targets and biomarkers in modern precision therapy. The therapeutic potential of HER3 has long been underappreciated, due to impaired kinase activity and relatively low expression in tumors. However, HER3 has received attention in recent years as it is a crucial heterodimeric partner for other EGFR family members and has the potential to regulate EGFR/HER2-mediated resistance. Upregulation of HER3 is associated with several malignancies where it fosters tumor progression via interaction with different receptor tyrosine kinases (RTKs). Studies also implicate HER3 contributing significantly to treatment failure, mostly through the activation of PI3K/AKT, MAPK/ERK and JAK/STAT pathways. Moreover, activating mutations in HER3 have highlighted the role of HER3 as a direct therapeutic target. Therapeutic targeting of HER3 includes abrogating its dimerization partners’ kinase activity using small molecule inhibitors (lapatinib, erlotinib, gefitinib, afatinib, neratinib) or direct targeting of its extracellular domain. In this review, we focus on HER3-mediated signaling, its role in drug resistance and discuss the latest advances to overcome resistance by targeting HER3 using mono- and bispecific antibodies and small molecule inhibitors.

Identification of tumorigenesis-related mRNAs associated with RNA-binding protein HuR in thyroid cancer cells

RNA binding proteins (RBPs) play a central role in cell physiology and pathology. Among them, HuR is a nuclear RBP, which shuttles to the cytoplasm to allow its RNA targets processing. HuR over-expression and delocalization are often associated to cell transformation. Numerous cancers display increased HuR protein levels and its high cytoplasmic levels has been associated with a worse prognosis.

In our study, we first evaluated HuR expression in normal and cancer thyroid tissues and then evaluated its function in thyroid cell lines. HuR is over-expressed in all thyroid tumor tissues; high cytoplasmic levels are detected in all thyroid carcinomas. HuR silencing decreased cell viability and determined apoptotic cell death, in a non-tumorigenic (Nthy-ori-3.1) and a tumorigenic (BCPAP) thyroid cell line. Global transcriptome analysis indicated that HuR silencing, though having similar biological effects, induces distinct gene expression modifications in the two cell lines. By using the RIP-seq approach, the HuR-bound RNA profiles of different thyroid cell lines were evaluated. We show that in distinct cell lines HuR-bound RNA profiles are different. A set of 114 HuR-bound RNAs distinguishing tumorigenic cell lines from the non-tumorigenic one was identified.

Altogether, our data indicate that HuR plays a role in thyroid tumorigenesis. Moreover, our findings are a proof of concept that RBP targets differ between cells with the same origin but with distinct biological behavior.

Factors Predictive of Response to Hormone Therapy in Breast Cancer

Aims and Background

Approximately half of metastatic breast cancers expressing estrogen and/or progesterone receptors responds to endocrine therapy, and postoperative adjuvant endocrine therapy provides about a 50% reduction in the development of recurrent disease. A number of publications have focused on the correlation of biomarkers, in particular estrogen and progesterone receptors and HER-2/neu status as well as different gene profiles, multigene assays and genetic polymorphisms with response to hormone therapy. The purpose of this article is to review the literature to identify biological markers predictive of response to tamoxifen and aromatase inhibitors.

Methods

A computerized literature search through Medline and ASCO abstract databases was performed, applying the words “endocrine therapy” and “predictive markers” and each of the following: early and metastatic breast cancer, estrogen receptors, progesterone receptors, HER2/neu, multigene assays, polymorphisms. The last search was updated in June 2007. In the examined literature, biological markers were retrospectively assayed to establish whether such variables were predictive for endocrine therapy efficacy.

Results

The role of estrogen receptor content as a predictor of response to endocrine treatment was confirmed: benefit from endocrine treatment was directly proportional to estrogen receptor levels. Progesterone receptor status was only a strong time-dependent prognostic value, and it has not yet been validated as a predictive factor of tamoxifen efficacy. Retrospective clinical data from upfront and sequential studies of aromatase inhibitors were discordant regarding the degree of benefit of these drugs over tamoxifen according to progesterone receptor status. HER-2 positivity was associated with a significantly greater risk of endocrine therapy failure in metastatic and neoadjuvant settings. The current generation of genomic assays for tamoxifen sensitivity all contain a combination of prognostic information that it is difficult to integrate into clinical practice.

Conclusions

Available clinical data are inconclusive to support preferential use of aromatase inhibitors over tamoxifen in progesterone-receptor-negative and HER-2-positive tumors, but it was also clear that lower estrogen receptors, lower progesterone receptors, and positive HER-2 are associated with lower responsiveness to any type of endocrine therapy. Tumors overexpressing HER-2 are endocrine resistant and they require the blockage of the HER-2 pathway in addition to estrogen deprivation. Recent molecular studies have shown that endocrine responsiveness is to a large extent influenced by estrogen-receptor-related pathways. In the future, the key to the correct tailoring of hormone therapy will probably be the ability to subtype estrogen-receptor-positive breast cancer.

Vaccination targeting human HER3 alters the phenotype of infiltrating T cells and responses to immune checkpoint inhibition

Expression of human epidermal growth factor family member 3 (HER3), a critical heterodimerization partner with EGFR and HER2, promotes more aggressive biology in breast and other epithelial malignancies. As such, inhibiting HER3 could have broad applicability to the treatment of EGFR- and HER2-driven tumors. Although lack of a functional kinase domain limits the use of receptor tyrosine kinase inhibitors, HER3 contains antigenic targets for T cells and antibodies. Using novel human HER3 transgenic mouse models of breast cancer, we demonstrate that immunization with recombinant adenoviral vectors encoding full length human HER3 (Ad-HER3-FL) induces HER3-specific T cells and antibodies, alters the T cell infiltrate in tumors, and influences responses to immune checkpoint inhibitions. Both preventative and therapeutic Ad-HER3-FL immunization delayed tumor growth but were associated with both intratumoral PD-1 expressing CD8⁺ T cells and regulatory CD4⁺ T cell infiltrates. Immune checkpoint inhibition with either anti-PD-1 or anti-PD-L1 antibodies increased intratumoral CD8⁺ T cell infiltration and eliminated tumor following preventive vaccination with Ad-HER3-FL vaccine. The combination of dual PD-1/PD-L1 and CTLA4 blockade slowed the growth of tumor in response to Ad-HER3-FL in the therapeutic model. We conclude that HER3-targeting vaccines activate HER3-specific T cells and induce anti-HER3 specific antibodies, which alters the intratumoral T cell infiltrate and responses to immune checkpoint inhibition.

Expression of PAX8 Target Genes in Papillary Thyroid Carcinoma

PAX8 is a thyroid-specific transcription factor whose expression is dysregulated in thyroid cancer. A recent study using a conditional knock-out mouse model identified 58 putative PAX8 target genes. In the present study, we evaluated the expression of 11 of these genes in normal and tumoral thyroid tissues from patients with papillary thyroid cancer (PTC). ATP1B1, GPC3, KCNIP3, and PRLR transcript levels in tumor tissues were significantly lower in PTCs than in NT, whereas LCN2, LGALS1 and SCD1 expression was upregulated in PTC compared with NT. Principal component analysis of the expression of the most markedly dysregulated PAX8 target genes was able to discriminate between PTC and NT. Immunohistochemistry was used to assess levels of proteins encoded by the two most dyregulated PAX8 target genes, LCN2 and GPC3. Interestingly, GPC3 was detectable in all of the NT samples but none of the PTC samples. Collectively, these findings point to significant PTC-associated dysregulation of several PAX8 target genes, supporting the notion that PAX8-regulated molecular cascades play important roles during thyroid tumorigenesis.

Emerging anti-cancer antibodies and combination therapies targeting HER3/ERBB3

Cancer progression depends on stepwise accumulation of oncogenic mutations and a select group of growth factors essential for tumor growth, metastasis and angiogenesis. Agents blocking the epidermal growth factor receptor (EGFR, also called HER1 and ERBB1) and the co-receptor called HER2/ERBB2 have been approved over the last decade as anti-cancer drugs. Because the catalytically defective member of the family, HER3/ERBB3, plays critical roles in emergence of resistance of carcinomas to various drugs, current efforts focus on antibodies and other anti-HER3/ERBB3 agents, which we review herein with an emphasis on drug combinations and some unique biochemical features of HER3/ERBB3.

Nottingham Prognostic Index Plus: Validation of a clinical decision making tool in breast cancer in an independent series

The Nottingham Prognostic Index Plus (NPI+) is a clinical decision making tool in breast cancer (BC) that aims to provide improved patient outcome stratification superior to the traditional NPI. This study aimed to validate the NPI+ in an independent series of BC. Eight hundred and eighty five primary early stage BC cases from Edinburgh were semi‐quantitatively assessed for 10 biomarkers [Estrogen Receptor (ER), Progesterone Receptor (PgR), cytokeratin (CK) 5/6, CK7/8, epidermal growth factor receptor (EGFR), HER2, HER3, HER4, p53, and Mucin 1] using immunohistochemistry and classified into biological classes by fuzzy logic‐derived algorithms previously developed in the Nottingham series. Subsequently, NPI+ Prognostic Groups (PGs) were assigned for each class using bespoke NPI‐like formulae, previously developed in each NPI+ biological class of the Nottingham series, utilising clinicopathological parameters: number of positive nodes, pathological tumour size, stage, tubule formation, nuclear pleomorphism and mitotic counts. Biological classes and PGs were compared between the Edinburgh and Nottingham series using Cramer's V and their role in patient outcome prediction using Kaplan–Meier curves and tested using Log Rank. The NPI+ biomarker panel classified the Edinburgh series into seven biological classes similar to the Nottingham series (p > 0.01). The biological classes were significantly associated with patient outcome (p < 0.001). PGs were comparable in predicting patient outcome between series in Luminal A, Basal p53 altered, HER2+/ER+ tumours (p > 0.01). The good PGs were similarly validated in Luminal B, Basal p53 normal, HER2+/ER− tumours and the poor PG in the Luminal N class (p > 0.01). Due to small patient numbers assigned to the remaining PGs, Luminal N, Luminal B, Basal p53 normal and HER2+/ER− classes could not be validated. This study demonstrates the reproducibility of NPI+ and confirmed its prognostic value in an independent cohort of primary BC. Further validation in large randomised controlled trial material is warranted.

Endocrine therapy resistance in breast cancer: current status, possible mechanisms and overcoming strategies. Future Med Chem. 2015;7:1511-1519. [PMID: 26306654 DOI: 10.4155/fmc.15.93]

Endocrine therapy has become one of most effective forms of targeted adjuvant therapy for hormone-sensitive breast cancer and may be given after surgery or radiotherapy, and also prior, or subsequent to chemotherapy. Current commonly used drugs for adjuvant endocrine therapy can be divided into following three classes: selective estrogen receptor modulators, aromatase inhibitors and selective estrogen receptor downregulators. Tumor cells can develop resistance to endocrine therapy, a major obstacle limiting the success of breast cancer treatment. The complicated crosstalk, both genomic and nongenomic, between estrogen receptors and growth factors was considered to be a crucial factor contributing to endocrine resistance. However, resistance to this therapy is thought to be a progressive, step-wise process, and the underlying mechanism remains unclear. In this review, we summarize the possible biological and molecular mechanisms that underlie endocrine resistance, and discuss some novel strategies to overcoming these issues.

Decreased LRIG1 in fulvestrant-treated luminal breast cancer cells permits ErbB3 upregulation and increased growth

ErbB3, a member of the ErbB family of receptor tyrosine kinases, is a potent activator of phosphatidyl inositol-3 kinase (PI3K) and mTOR signaling, driving tumor cell survival and therapeutic resistance in breast cancers. In luminal breast cancers, ErbB3 upregulation following treatment with the anti-estrogen fulvestrant enhances PI3K/mTOR-mediated cell survival. However, the mechanism by which ErbB3 is upregulated in fulvestrant-treated cells is unknown. We found that ErbB3 protein levels and cell surface presentation were increased following fulvestrant treatment, focusing our attention on proteins that regulate ErbB3 at the cell surface, including Nrdp1, NEDD4, and LRIG1. Among these, only LRIG1 correlated positively with ERα, but inversely with ErbB3 in clinical breast cancer datasets. LRIG1, an estrogen-inducible ErbB down-regulator, was decreased in a panel of fulvestrant-treated luminal breast cancer cells. Ectopic LRIG1 expression from an estrogen-independent promoter uncoupled LRIG1 from estrogen regulation, thus sustaining LRIG1 and maintaining low ErbB3 levels in fulvestrant-treated cells. An LRIG1 mutant lacking the ErbB3 interaction motif was insufficient to down-regulate ErbB3. Importantly, LRIG1 overexpression improved fulvestrant-mediated growth inhibition, while cells expressing the LRIG1 mutant were poorly sensitive to fulvestrant, despite effective ERα down-regulation. Consistent with these results, LRIG1 expression correlated positively with increased disease-free survival in anti-estrogen-treated breast cancer patients. These data suggest that ERα-dependent expression of LRIG1 dampens ErbB3 signaling in luminal breast cancer cells, and by blocking ERα activity with fulvestrant, LRIG1 is decreased thus permitting ErbB3 accumulation, enhanced ErbB3 signaling to cell survival pathways, and blunting therapeutic response to fulvestrant.

Perhexiline promotes HER3 ablation through receptor internalization and inhibits tumor growth

INTRODUCTION

Human epidermal growth factor receptor HER3 has been implicated in promoting the aggressiveness and metastatic potential of breast cancer. Upregulation of HER3 has been found to be a major mechanism underlying drug resistance to EGFR and HER2 tyrosine kinase inhibitors and to endocrine therapy in the treatment of breast cancer. Thus, agents that reduce HER3 expression at the plasma membrane may synergize with current therapies and offer a novel therapeutic strategy to improve treatment.

METHODS

We devised an image-based screening platform using membrane localized HER3-YFP to identify small molecules that promote HER3 internalization and degradation. In vitro and in vivo tumor models were used to characterize the signaling effects of perhexiline, an anti-anginal drug, identified by the screening platform.

RESULTS

We found perhexiline, an anti-anginal drug, selectively internalized HER3, decreased HER3 expression, and subsequently inhibited signaling downstream of HER3. Consistent with these results, perhexiline inhibited breast cancer cell proliferation in vitro and tumor growth in vivo.

CONCLUSIONS

This is the first demonstration that HER3 can be targeted with small molecules by eliminating it from the cell membrane. The novel approach used here led to the discovery that perhexiline ablates HER3 expression, and offers an opportunity to identify HER3 ablation modulators as innovative therapeutics to improve survival in breast cancer patients.

The broad-spectrum metalloproteinase inhibitor BB-94 inhibits growth, HER3 and Erk activation in fulvestrant-resistant breast cancer cell lines

Breast cancer cells can switch from estrogen receptor α (ER)- to human epidermal growth factor receptor (HER)-driven cell growth upon acquiring antiestrogen resistance. HER ligands are cleaved by metalloproteinases leading to release of active HER ligands, activation of HER receptors and consequently increased cell growth. In this study, we investigated the importance of HER receptors, in particular HER3, and HER ligand shedding for growth and signaling in human MCF-7 breast cancer cells and MCF-7-derived sublines resistant to the antiestrogen fulvestrant. The HER3/HER4 ligand heregulin 1β induced phosphorylation of HER3, Akt and Erk, and partly rescued fulvestrant-inhibited growth of MCF-7 cells. HER3 ligands were found to be produced and shed from the fulvestrant-resistant cells as conditioned medium from fulvestrant-resistant MCF-7 cells induced phosphorylation of HER3 and Akt in MCF-7 cells. This was prevented by treatment of resistant cells with the metalloproteinase inhibitor TAPI-2. Only the broad-spectrum metalloproteinase inhibitor BB-94, and not the more selective inhibitors GM6001 or TAPI-2, which inhibited shedding of the HER ligands produced by the fulvestrant-resistant cells, was able to inhibit growth and activation of HER3 and Erk in resistant cells. Compared to MCF-7, fulvestrant-resistant cells have increased HER3 phosphorylation, but knockdown of HER3 had no inhibitory effect on resistant cell growth. The EGFR inhibitor gefitinib exhibited only a minor growth inhibition, whereas the pan-HER inhibitor CI-1033 exerted growth arrest. Thus, neither HER3 nor EGFR alone are the main driver of fulvestrant-resistant cell growth and treatment should target both receptors. Ligand shedding is not a treatment target, as receptor activation occurred, independent of release of ligands. Only the broad-spectrum metalloproteinase inhibitor BB-94 could abrogate HER3 and Erk activation in the resistant cells, which stresses the complexity of the resistance mechanisms and the requirement of targeting signaling from HER receptors by multiple strategies.

Targeting of erbB3 receptor to overcome resistance in cancer treatment

The erbB receptors, including the epidermal growth factor receptor (EGFR), erbB2 (also known as HER2/neu), erbB3 (or HER3), and erbB4 (or HER4), are often aberrantly activated in a wide variety of human cancers. They are excellent targets for selective anti-cancer therapies because of their transmembrane location and pro-oncogenic activity. While several therapeutic agents against erbB2 and/or EGFR have been used in the treatment of human cancers with efficacy, there has been relatively less emphasis on erbB3 as a molecular target. Elevated expression of erbB3 is frequently observed in various malignancies, where it promotes tumor progression via interactions with other receptor tyrosine kinases (RTKs) due to its lack of or weak intrinsic kinase activity. Studies on the underlying mechanisms implicate erbB3 as a major cause of treatment failure in cancer therapy, mainly through activation of the PI-3 K/Akt, MEK/MAPK, and Jak/Stat signaling pathways as well as Src kinase. It is believed that inhibition of erbB3 signaling may be required to overcome therapeutic resistance and effectively treat cancers. To date, no erbB3-targeted therapy has been approved for cancer treatment. Targeting of erbB3 receptor with a monoclonal antibody (Ab) is the only strategy currently under preclinical study and clinical evaluation. In this review, we focus on the role of erbB3-initiated signaling in the development of cancer drug resistance and discuss the latest advances in identifying therapeutic strategies inactivating erbB3 to overcome the resistance and enhance efficacy of cancer therapeutics.

Role of erbB3 receptors in cancer therapeutic resistance

ErbB3 receptors are unique members of the erbB receptor tyrosine kinases (RTKs), which are often aberrantly expressed and/or activated in human cancers. Unlike other members in the family, erbB3 lacks or has impaired kinase activity. To transduce cell signaling, erbB3 has to interact with other RTKs and to be phosphorylated by its interactive partners, of those, erbB2 is the most important one. ErbB3 is frequently co-expressed with other RTKs in cancer cells to activate oncogenic signaling, such as phosphoinositide-3-kinase/protein kinase B (Akt) pathway, mitogen-activated protein kinase kinase (MEK)/mitogen-activated protein kinase (MAPK) pathway, Janus kinase (Jak)/signal transducer and activator of transcription (Stat) pathway, etc. and thereby promote tumorigenesis. Numerous studies have demonstrated that activation of erbB3 signaling plays an important role in the progression of a variety of tumor types, such as erbB2-overexpressing breast cancer, castration-resistant prostate cancer, platinum refractory/resistant ovarian cancer, epidermal growth factor receptor TKI-resistant non-small-cell lung cancer, and others. Basic research on the underlying mechanisms implicated the functions of erbB3 as a major cause of treatment failure in cancer therapy. Thus, concomitant inhibition of erbB3 is thought to be required to overcome the resistance and to effectively treat human cancers. This review focuses on the latest advances in our understanding of erbB3-initiated signaling in the development of resistance to cancer treatments.

Do type 1 receptor tyrosine kinases inform treatment choice? A prospectively planned analysis of the TEAM trial

BACKGROUND

Epidermal growth factor receptors contribute to breast cancer relapse during endocrine therapy. Substitution of aromatase inhibitors (AIs) may improve outcomes in HER-positive cancers.

METHODS

Tissue microarrays were constructed. Quantitative analysis of HER1, HER2, and HER3 was performed. Data were analysed relative to disease-free survival and treatment using outcomes at 2.75 and 6.5 years.

RESULTS

Among 4541 eligible samples, 4225 (93%) had complete HER1-3 data. Overall, 5% were HER1-positive, 13% HER2-positive, and 21% HER3-positive; 32% (n=1351) overexpressed at least one HER receptor. In the HER1-3-negative subgroup, the hazard ratio (HR) for upfront exemestane vs tamoxifen at 2.75 years was 0.67 (95% confidence interval (CI), 0.52-0.87), in the HER1-3-positive subgroup, the HR was 1.15 (95% CI, 0.85-1.56). A prospectively planned treatment-by-marker analysis demonstrated a significant interaction between HER1-3 and treatment at 2.75 years (HR=0.58; 95% CI, 0.39-0.87; P=0.008), as confirmed by multivariate regression analysis adjusting for prognostic factors (HR=0.55; 95% CI, 0.36-0.85; P=0.005). This effect was time dependent.

CONCLUSION

In the 2.75 years prior to switching patients initially treated with tamoxifen to exemestane, a significant treatment-by-marker effect exists between AI/tamoxifen treatment and HER1-3 expression, suggesting HER expression could be used to select appropriate endocrine treatment at diagnosis to prevent or delay early relapses.

SIRT2: tumour suppressor or tumour promoter in operable breast cancer?

PURPOSE

Sirtuins comprise a family of genes involved in cellular stress, survival and damage responses. They have been implicated in a range of diseases including cancer, with most information pertaining to their function in tumourigenesis being derived from in vitro studies, or model organisms. Their putative roles as tumour suppressors or tumour promoters remain to be validated in vivo. Little is known about their role in breast tumourigenesis. We sought to evaluate the seven sirtuin family members (SIRT1-7) in a human breast cancer cohort, in relation to clinico-pathological features and outcome of the disease.

MATERIALS AND METHODS

Immunohistochemical analysis of SIRT1-7 protein levels was undertaken in 392 oestrogen receptor (ER+ve) and 153 ER-ve breast tumour samples. SIRT1-7 transcriptional levels were assessed in normal (n=25), non-malignant (n=73) and malignant (n=70) breast tissue using Relative Quantitative Real Time PCR. Statistical analyses determined if SIRT1-7 transcription or protein expression was associated with clinical parameters or outcome.

RESULTS

In ER-ve tumours, high protein levels of nuclear SIRT2 were associated with reduced time to recurrence and disease-specific death. This association was only observed in Grade 3 tumours. In the ER+ve cohort, high SIRT2 nuclear levels were associated with shorter disease-free survival and time to recurrence whilst on Tamoxifen, in patients with Grade 3 tumours. Conversely, in Grade 2 tumours, high SIRT2 levels were associated with increased time to recurrence.

CONCLUSIONS

Our data suggest that SIRT2 is the sirtuin predominantly involved in breast tumourigenesis and prognosis. It indicates that SIRT2 acts as a tumour suppressor or tumour promoter dependent upon breast tumour grade.

The in situ local immune response, tumour senescence and proliferation in colorectal cancer

BACKGROUND

Immune cell infiltrates are important determinants of colorectal cancer (CRC) outcome. Their presence may be driven by tumour or host-specific factors. From previous studies in mice, senescence, a state of cell cycle arrest, may moderate tumour progression through upregulation of antitumour immune responses. The relationships between senescence and immune infiltrates have not previously been studied in humans. We explore whether a marker of senescence (p16(ink4a)) in combination with low level expression of a proliferation marker (ki-67) relate to T cell infiltrates in CRC, and whether p16(ink4a), Ki-67 and immune infiltrates have similar prognostic value.

METHODS

Immunostaining of p16(inka) and Ki-67 was performed within a CRC tissue microarray. Nuclear p16(inka) and Ki-67 were categorised as high/low. T-cell markers, CD3, CD45RO, CD8 and FOXP3 were scored separately as high/low grade in three areas of the tumour: the invasive margin (IM), tumour stroma and cancer cell nests (CCNs). results: Two hundred and thirty stage I-III cancers were studied. High nuclear p16(ink4a) was expressed in 63% and high proliferation (Ki-67 >15%) in 61%. p16(ink4a) expression was associated with reduced CD45RO+ cells at the IM (P<0.05) and within the stroma (P<0.05) and reduced CD8+ cells at the IM (P<0.01). A low Ki-67 proliferative index was associated with reduced density of CD3+ cells in CCNs (P<0.01), reduced CD45RO+ cells at the IM (P<0.05) and within the CCNs (P<0.001), reduced FOXP3+ cells at the IM (P<0.001), within the stroma (P=0.001) and within CCNs (P<0.001) and reduced CD8+ cells at the IM (P<0.05) and within the CCNs (P<0.05). Tumours with both a low proliferative index and expression of p16(ink4a) demonstrated similar consistent relationships with reduced densities of T-cell infiltrates. On multivariate analysis, TNM stage (P<0.001), low CD3 cells at the IM (P=0.014), low CD8 cells at the IM (P=0.037), low proliferation (Ki-67; P=0.013) and low senescence (p16(ink4a); P=0.002) were independently associated with poorer cancer survival.

CONCLUSION

Senescence, proliferation and immune cell infiltrates are independent prognostic factors in CRC. Although related to survival, p16(ink4a)-associated senescence is not associated with an upregulation of antitumour T-cell responses.

A meta-analysis of gene expression-based biomarkers predicting outcome after tamoxifen treatment in breast cancer

To date, three molecular markers (ER, PR, and CYP2D6) have been used in clinical setting to predict the benefit of the anti-estrogen tamoxifen therapy. Our aim was to validate new biomarker candidates predicting response to tamoxifen treatment in breast cancer by evaluating these in a meta-analysis of available transcriptomic datasets with known treatment and follow-up. Biomarker candidates were identified in Pubmed and in the 2007-2012 ASCO and 2011-2012 SABCS abstracts. Breast cancer microarray datasets of endocrine therapy-treated patients were downloaded from GEO and EGA and RNAseq datasets from TCGA. Of the biomarker candidates, only those identified or already validated in a clinical cohort were included. Relapse-free survival (RFS) up to 5 years was used as endpoint in a ROC analysis in the GEO and RNAseq datasets. In the EGA dataset, Kaplan-Meier analysis was performed for overall survival. Statistical significance was set at p < 0.005. The transcriptomic datasets included 665 GEO-based and 1,208 EGA-based patient samples. All together 68 biomarker candidates were identified. Of these, the best performing genes were PGR (AUC = 0.64, p = 2.3E-07), MAPT (AUC = 0.62, p = 7.8E-05), and SLC7A5 (AUC = 0.62, p = 9.2E-05). Further genes significantly correlated to RFS include FOS, TP53, BTG2, HOXB7, DRG1, CXCL10, and TPM4. In the RNAseq dataset, only ERBB2, EDF1, and MAPK1 reached statistical significance. We evaluated tamoxifen-resistance genes in three independent platforms and identified PGR, MAPT, and SLC7A5 as the most promising prognostic biomarkers in tamoxifen treated patients.

Learning the local Bayesian network structure around the ZNF217 oncogene in breast tumours

In this study, we discuss and apply a novel and efficient algorithm for learning a local Bayesian network model in the vicinity of the ZNF217 oncogene from breast cancer microarray data without having to decide in advance which genes have to be included in the learning process. ZNF217 is a candidate oncogene located at 20q13, a chromosomal region frequently amplified in breast and ovarian cancer, and correlated with shorter patient survival in these cancers. To properly address the difficulties in managing complex gene interactions given our limited sample, statistical significance of edge strengths was evaluated using bootstrapping and the less reliable edges were pruned to increase the network robustness. We found that 13 out of the 35 genes associated with deregulated ZNF217 expression in breast tumours have been previously associated with survival and/or prognosis in cancers. Identifying genes involved in lipid metabolism opens new fields of investigation to decipher the molecular mechanisms driven by the ZNF217 oncogene. Moreover, nine of the 13 genes have already been identified as putative ZNF217 targets by independent biological studies. We therefore suggest that the algorithms for inferring local BNs are valuable data mining tools for unraveling complex mechanisms of biological pathways from expression data. The source code is available at http://www710.univ-lyon1.fr/∼aaussem/Software.html.

Interactions between MAP kinase and oestrogen receptor in human breast cancer

PURPOSE

The oestrogen receptor (ERα) may be activated in a ligand-dependent manner, via oestrogen, or in a ligand-independent manner, via signal transduction pathways. Mitogen Activated Protein Kinase (MAPK) is known to directly phosphorylate ERα at serine 118 in a ligand-independent manner. This study investigated the interaction between MAPK and ERα in breast cancer.

MATERIALS & METHODS

Immunohistochemical experiments were undertaken to determine the expression of MAPK, pMAPK and pER(ser118) in breast tumours to determine their clinical relevance. Immunofluorescent experiments were performed, on MCF-7 breast cancer cells, to monitor the phosphorylation and localisation of MAPK and ERα in response to oestrogen, heregulin and a MAPK inhibitor.

RESULTS

Oestrogen and Heregulin stimulated phosphorylation of ERα and its nuclear translocation, but heregulin induced this at levels much lower than those observed with oestrogen. Following stimulation with heregulin, but not oestrogen, treatment with MAPK inhibitor reduced the levels of nuclear pER(ser118). In cells treated with both oestrogen and heregulin, nuclear pER(ser118) was visible; but at levels comparable with heregulin treatment alone.

CONCLUSION

This study confirms that ligand-mediated phosphorylation is associated with rapid nuclear localisation of ERα, due to oestrogen binding. ERα is phosphorylated at serine 118 in a ligand-independent manner. Preventing nuclear translocation of pMAPK reduced the levels of ligand-independent, but not ligand-dependent phosphorylation of ERα. Co-stimulation with both oestrogen and heregulin suggested that heregulin mediated signalling determines the subcellular localisation of ERα. Activation of ERα by direct phosphorylation may result in its rapid deactivation due to degradation or nuclear export.

Biological mechanisms and clinical implications of endocrine resistance in breast cancer

Endocrine therapy represents the first and most efficacious targeted treatment for women with estrogen receptor-positive (ER+) breast cancer. In the last four decades several hormonal agents have been successfully introduced in clinical practice as both palliative therapy for advanced disease and adjuvant treatment for prevention of tumor relapse. Nevertheless, the intrinsic and acquired resistance occurs in a significant proportion of patients, limiting the efficacy of endocrine treatments. Several molecular mechanisms have been proposed to be responsible for endocrine resistance. Loss of ER expression, altered activity of ER coregulators, deregulation of apoptosis and cell cycle signaling, and hyperactive receptor tyrosine kinase (RTK) and stress/cell kinase pathways can collectively orchestrate the development and sustenance of pharmacologic resistance to endocrine therapy. Preclinical and clinical evidence documents the plasticity in ER expression levels and signaling. As such, ER can either drive gene transcription and tumor progression directly or crosstalk with alternate RTK and cellular kinase signaling pathways, resulting in modulation of its own expression levels and transcriptional program. For this reason a therapeutic approach based on the combination of agents targeting both ER and RTK signaling represents a promising strategy to be tested. Among many RTKs, EGFR, HER2, and PI3K have been found to be viable targets for the combination therapy strategy, at least in the preclinical setting. However, early results from clinical trials testing combination strategies have been discordant, suggesting the need for better approaches to simultaneously inhibit multiple escape pathways and to select the patients who may benefit the most from these strategies.

Activated HER-receptors in predicting outcome of ER-positive breast cancer patients treated with adjuvant endocrine therapy

The four human epidermal growth factor receptors (HER1-4) are involved in growth stimulation and may play a role in endocrine resistance. The receptors form dimers, leading to activation by mutual phosphorylation. Our purpose was to explore the role of the activated receptors (pHER1, pHER2, pHER3) in endocrine treated breast cancer in terms of co-expression and association with disease-free survival (DFS) in 1062 patients with ER-positive tumors. Furthermore, HER2 amplification was evaluated. We found positive associations between the phosphorylated receptors. pHER1 and pHER3 were co-expressed with one or two of the other activated receptors in 85% and 89% of tumors, respectively, whereas pHER2 was co-expressed with the other activated receptors in 54% of tumors. Except for HER2, which was associated with poor prognosis, none of the remaining markers were associated with DFS. However, frequent co-expression indicates a role of the other HER-family members in activation of HER2.

Expression of activated type I receptor tyrosine kinases in early breast cancer

Overexpression of EGFR, HER2 and HER3 are known to be associated with poor outcome in breast cancer. Few studies have examined the clinical impact of activation of these proteins. In the present study, we evaluated EGFR, HER2 and HER3 and the activated (phosphorylated) forms of these proteins in patients with early breast cancer. EGFR, HER2, HER3, pEGFR, pHER2 and pHER3 expression was determined by immunohistochemical analysis of tissue microarrays constructed from tumours within the Edinburgh Breast Conservation Series (BCS). The BCS represents a fully-documented consecutive cohort of 1,812 patients treated by breast conservation surgery in a single institution. Our results demonstrate overexpression of HER2 and pHER2 to be associated with a significant reduction in overall survival (OS) (HR: 1.66, 95 % CI 1.22-2.26, p = 0.001 and HR: 1.57, 95 % CI 1.22-2.03, p = 0.001, respectively) and distant relapse-free survival (DRFS) (HR: 1.63, 95 % CI 1.23-2.18, p = 0.001 and HR: 1.55, 95 % CI 1.23-1.97, p = 0.0002, respectively). Paradoxically, expression of pEGFR was associated with a significantly improved OS (HR: 0.67 95 % CI 0.50-0.91, p = 0.01) and DRFS (HR: 0.73, 95 % CI 0.56-0.96, p = 0.025). Expression of activated EGFR/HER2 provides additional information on ER positive breast cancer patients and suggests alternative treatment for those in this subgroup.

Proximity ligation assays for isoform-specific Akt activation in breast cancer identify activated Akt1 as a driver of progression

The PI3K/Akt signal transduction pathway plays an important role in cancer progression and cell survival. Akt activation is associated with poor outcome in endocrine-treated breast cancer, whereas high levels of cytoplasmic Akt2 are associated with an improved overall survival. Proximity ligation assays (PLAs) were used to determine quantitative expression levels of isoform-specific activation (phosphorylation) of Akt1 and Akt2 in formalin-fixed, paraffin-embedded cell lines and breast cancer tumour tissues in situ. PLAs demonstrated a range of expression in breast cancer samples for total pAkt1 and pAkt2. High levels of pAkt1 were associated with reduced DRFS (HR: 1.45, 95% CI 1.14-1.83, p = 0.002) and OS (HR: 1.42, 95% CI 1.10-1.83, p = 0.007). When PLA results were combined, patients that had high levels of pAkt1 only had a significantly decreased DRFS (HR: 1.92, 95% CI 1.34-2.76, p = 0.005) and OS (HR: 1.94, 95% CI 1.32-2.86, p = 0.008) compared to other patients. Using PLAs to discriminate activation of Akt1 versus Akt2 suggests that Akt1 drives progression in early breast cancers. In cases where both Akt1/Akt2 are activated, Akt2 may act to reverse this effect. Using PLAs, we have measured activation of Akt1 and Akt2 proteins separately in situ in FFPE breast cancer samples.

Exemestane in the adjuvant treatment of breast cancer in postmenopausal women

Exemestane is an irreversible inhibitor of the aromatase enzyme, which is a key component in the production of estrogen. The majority of breast cancers are sensitive to the proliferative effects of estrogen. Exemestane is approved for the adjuvant treatment of postmenopausal women with breast cancer after 2 to 3 years of tamoxifen therapy, based on a 32% improvement in disease-free survival compared with 5 years of tamoxifen alone (P < 0.001). Exemestane has also shown clinical benefits as an upfront therapy. The safety profile of exemestane shares some side effects with tamoxifen (hot flashes and arthralgia), but is not associated with an increased risk of endometrial cancer or thromboembolic events. This review will discuss in detail the efficacy and safety of exemestane in early breast cancer.

Estrogen receptor and progesterone receptor as predictive biomarkers of response to endocrine therapy: a prospectively powered pathology study in the Tamoxifen and Exemestane Adjuvant Multinational trial

PURPOSE

The Tamoxifen and Exemestane Adjuvant Multinational (TEAM) trial included a prospectively planned pathology substudy testing the predictive value of progesterone receptor (PgR) expression for outcome of estrogen receptor-positive (ER-positive) early breast cancer treated with exemestane versus tamoxifen.

PATIENTS AND METHODS

Pathology blocks from 4,781 TEAM patients randomly assigned to exemestane versus tamoxifen followed by exemestane for 5 years of total therapy were collected centrally, and tissue microarrays were constructed from samples from 4,598 patients. Quantitative analysis of hormone receptors (ER and PgR) was performed by using image analysis and immunohistochemistry, and the results were linked to outcome data from the main TEAM trial and analyzed relative to disease-free survival and treatment.

RESULTS

Of 4,325 eligible ER-positive patients, 23% were PgR-poor (Allred < 4) and 77% were PgR- rich (Allred ≥ 5). No treatment-by-marker effect for PgR was observed for exemestane versus tamoxifen (PgR-rich hazard ratio [HR], 0.83; 95% CI, 0.65 to 1.05; PgR-poor HR, 0.85; 95% CI, 0.61 to 1.19; P = .88 for interaction). Both PgR and ER expression were associated with patient prognosis in univariate (PgR HR, 0.53; 95% CI, 0.43 to 0.65; P < .001; ER HR, 0.66; 95% CI, 0.51 to 0.86; P = .002), and multivariate analyses (P < .001 and P = .001, respectively). A trend toward a treatment-by-marker effect for ER-rich patients was observed.

CONCLUSION

Preferential exemestane versus tamoxifen treatment benefit was not predicted by PgR expression; conversely, patients with ER-rich tumors may derive additional benefit from exemestane. Quantitative analysis of ER and PgR expression provides highly significant information on risk of early relapse (within 1 to 3 years) during treatment.

Estrogen receptor β represses Akt signaling in breast cancer cells via downregulation of HER2/HER3 and upregulation of PTEN: implications for tamoxifen sensitivity

Introduction

The inhibition of estrogen receptor (ER) α action with the ER antagonist tamoxifen is an established treatment in the majority of breast cancers. De novo or acquired resistance to this therapy is common. Expression of ERβ in breast tumors has been implicated as an indicator of tamoxifen sensitivity. The mechanisms behind this observation remain largely uncharacterized. In the present study, we investigated whether ERβ can modulate pathways implicated in endocrine resistance development.

Methods

T47-D and MCF-7 ERα-expressing breast cancer cells with tetracycline-regulated expression of ERβ were used as a model system. Expression levels and activity of known regulators of endocrine resistance were analyzed by performing quantitative polymerase chain reaction assays, Western blot analysis and immunostaining, and sensitivity to tamoxifen was investigated by using a cell proliferation kit.

Results

Expression of ERβ in ERα-positive T47-D and MCF-7 human breast cancer cells resulted in a decrease in Akt signaling. The active form of an upstream regulator of Akt, proto-oncogene c-ErbB-2/receptor tyrosine kinase erbB-3 (HER2/HER3) receptor dimer, was also downregulated by ERβ. Furthermore, ERβ increased expression of the important inhibitor of Akt, phosphatase and tensin homologue deleted on chromosome 10 (PTEN). Importantly, ERβ expression increased the sensitivity of these breast cancer cells to tamoxifen.

Conclusions

Our results suggest a link between expression of ERβ and endocrine sensitivity by increasing PTEN levels and decreasing HER2/HER3 signaling, thereby reducing Akt signaling with subsequent effects on proliferation, survival and tamoxifen sensitivity of breast cancer cells. This study supports initiatives to further investigate whether ERβ presence in breast cancer samples is an indicator for endocrine response. Current therapies in ERα-positive breast cancers aim to impair ERα activity with antagonists or by removal of endogenous estrogens with aromatase inhibitors. Data from this study could be taken as indicative for also using ERβ as a target in selected groups of breast cancer.

The p160 ER co-regulators predict outcome in ER negative breast cancer

The SRC family of ER co-regulators are frequently overexpressed in breast cancer. Overexpression of AIB1 appears to be linked to hormone resistance in HER2 positive breast cancer. However, the role of these co-regulators in ER negative disease is poorly understood. SRC1, SRC2 and AIB1 expression was determined by immunohistochemical analysis of tissue microarrays constructed from tumours within the Edinburgh Breast Conservation Series (BCS). The BCS represents a fully documented consecutive cohort of 1,812 patients treated by breast conservation surgery in a single institution. Our results demonstrate tumours that overexpress both HER2 and AIB1 were associated with markedly reduced relapse free, distant relapse free and overall survival compared to HER2 and AIB1 only overexpressing tumours irrespective of ER status. In ER negative disease both SRC1 and AIB1 were linked to early relapse and death. The SRC family of ER co-regulators is involved in early relapse and resistance in both ER negative and ER positive breast cancer challenging the conventional concept that this effect is mediated solely via the ER.