Involvement of epidermal growth factor receptor overexpression in the promotion of breast cancer brain metastasis

Brain endothelial cells promote breast cancer cell extravasation to the brain via EGFR-DOCK4-RAC1 signalling

The role of endothelial cells in promoting cancer cell extravasation to the brain during the interaction of cancer cells with the vasculature is not well characterised. We show that brain endothelial cells activate EGFR signalling in triple-negative breast cancer cells with propensity to metastasise to the brain. This activation is dependent on soluble factors secreted by brain endothelial cells, and occurs via the RAC1 GEF DOCK4, which is required for breast cancer cell extravasation to the brain in vivo. Knockdown of DOCK4 inhibits breast cancer cell entrance to the brain without affecting cancer cell survival or growth. Defective extravasation is associated with loss of elongated morphology preceding intercalation into brain endothelium. We also show that brain endothelial cells promote paracrine stimulation of mesenchymal-like morphology of breast cancer cells via DOCK4, DOCK9, RAC1 and CDC42. This stimulation is accompanied by EGFR activation necessary for brain metastatic breast cancer cell elongation which can be reversed by the EGFR inhibitor Afatinib. Our findings suggest that brain endothelial cells promote metastasis through activation of cell signalling that renders breast cancer cells competent for extravasation. This represents a paradigm of brain endothelial cells influencing the signalling and metastatic competency of breast cancer cells.

Genomics of Breast Cancer Brain Metastases: A Meta-Analysis and Therapeutic Implications

Breast cancer brain metastases are a challenging daily practice, and the biological link between gene mutations and metastatic spread to the brain remains to be determined. Here, we performed a meta-analysis on genomic data obtained from primary tumors, extracerebral metastases and brain metastases, to identify gene alterations associated with metastatic processes in the brain. Articles with relevant findings were selected using Medline via PubMed, from January 1999 up to February 2022. A critical review was conducted according to the Preferred Reporting Items for Systematic Review and Meta-analysis statement (PRISMA). Fifty-seven publications were selected for this meta-analysis, including 37,218 patients in all, 11,906 primary tumor samples, 5541 extracerebral metastasis samples, and 1485 brain metastasis samples. We report the overall and sub-group prevalence of gene mutations, including comparisons between primary tumors, extracerebral metastases and brain metastases. In particular, we identified six genes with a higher mutation prevalence in brain metastases than in extracerebral metastases, with a potential role in metastatic processes in the brain: ESR1, ERBB2, EGFR, PTEN, BRCA2 and NOTCH1. We discuss here the therapeutic implications. Our results underline the added value of obtaining biopsies from brain metastases to fully explore their biology, in order to develop personalized treatments.

Epidermal growth factor receptor mutations and brain metastases in non-small cell lung cancer

Studies have revealed that non-small cell lung cancer (NSCLC) with epidermal growth factor receptor (EGFR) mutations has a high incidence of brain metastases (BMs). However, the association between EGFR mutations and BMs remains unknown. This review summarizes detailed information about the incidence of BMs, clinical and imaging characteristics of BMs, brain surveillance strategies, influence of treatments on BMs, prognosis after BMs, and differences in EGFR mutations between paired primary tumors and BMs in EGFR-mutated NSCLC. The prognostic results demonstrate that patients with mutated EGFR have a higher incidence of BMs, EGFR tyrosine kinase inhibitors (EGFR-TKIs) (afatinib and osimertinib) delay the development of BMs, and patients with mutated EGFR with synchronous or early BMs have better overall survival after BMs than those with wild-type EGFR. The EGFR mutation status of BM sites is not always in accordance with the primary tumors, which indicates that there is heterogeneity in EGFR gene status between paired primary tumors and BMs. However, the EGFR gene status of the primary site can largely represent that of BM sites. Among patients developing synchronous BMs, patients with mutated EGFR are less likely to have central nervous system (CNS) symptoms than patients with wild-type EGFR. However, the possibility of neuro-symptoms is high in patients with metachronous BMs. Patients with mutated EGFR tend to have multiple BMs as compared to patients with wild-type EGFR. Regarding very early-stage NSCLC patients without neuro-symptoms, regular neuroimaging follow-up is not recommended. Among advanced NSCLC patients with EGFR mutation, liberal brain imaging follow-up in the first several years showed more advantages in terms of cost.

Anti-Hormonal Therapy in Breast Cancer and Its Effect on the Blood-Brain Barrier

The molecular receptor status of breast cancer has implications for prognosis and long-term metastasis. Although metastatic luminal B-like, hormone-receptor-positive, HER2−negative, breast cancer causes brain metastases less frequently than other subtypes, though tumor metastases in the brain are increasingly being detected of this patient group. Despite the many years of tried and tested use of a wide variety of anti-hormonal therapeutic agents, there is insufficient data on their intracerebral effectiveness and their ability to cross the blood-brain barrier. In this review, we therefore summarize the current state of knowledge on anti-hormonal therapy and its intracerebral impact and effects on the blood-brain barrier in breast cancer.

Recent advances in understanding the molecular role of phosphoinositide-specific phospholipase C gamma 1 as an emerging onco-driver and novel therapeutic target in human carcinogenesis

Phosphoinositide metabolism is crucial intracellular signaling system that regulates a plethora of biological functions including mitogenesis, cell proliferation and division. Phospholipase C gamma 1 (PLCγ1) which belongs to phosphoinositide-specific phospholipase C (PLC) family, is activated by many extracellular stimuli including hormones, neurotransmitters, growth factors and modulates several cellular and physiological functions necessary for tumorigenesis such as cell survival, migration, invasion and angiogenesis by generating inositol 1,4,5-triphosphate (IP3) and diacylglycerol (DAG) via hydrolysis of phosphatidylinositol 4,5-biphosphate (PIP2). Cancer remains as a leading cause of global mortality and aberrant expression and regulation of PLCγ1 is linked to a plethora of deadly human cancers including carcinomas of the breast, lung, pancreas, stomach, prostate and ovary. Although PLCγ1 cross-talks with many onco-drivers and signaling circuits including PI3K, AKT, HIF1-α and RAF/MEK/ERK cascade, its precise role in carcinogenesis is not completely understood. This review comprehensively discussed the status quo of this ubiquitously expressed phospholipase as a tumor driver and highlighted its significance as a novel therapeutic target in cancer. Furthermore, we have highlighted the significance of somatic driver mutations in PLCG1 gene and molecular roles of PLCγ1 in several major human cancers, a knowledgebase that can be utilized to develop novel, isoform-specific small molecule inhibitors of PLCγ1.

Factors affecting time to brain metastases for stage 2 and 3 breast cancer patients: A large single-institutional analysis with potential screening implications

Background

Breast cancer is the second most common cancer associated with brain metastases. The purpose of this study was to identify factors that impact the time to brain metastases in breast cancer patients at a single institution.

Methods

Single institution retrospective study that captured all consecutive stage 2 and stage 3 breast cancer patients from 2003 to 2010. Patient characteristics analyzed included age, hormone status, HER2 receptor status, grade, stage, and time from breast cancer diagnosis to brain metastasis.

Results

A total of 1218 patients were eligible for the final analysis. 849 (69.7%) patients were ER+/HER2−, 90 (7.4%) were HER2+, and 279 (22.9%) were triple-negative (TN). Overall, 74 patients (6.1%) developed brain metastases over a median follow up time of 92 months. Median times to brain metastases for HER2+, TN, and ER+/HER2− patients were 20, 26, and 57 months, respectively. Multivariate analysis demonstrated that TN disease (HR = 2.043, P = .015), grade (HR = 1.667, P = .024) and stage (HR = 3.851, P < .001) were independent risk factors for earlier brain metastases. Median times to brain metastases were 34 and 52 months for stage 3 and 2 patients, and 30, 49, and 71 months for grade 3, 2, and 1 tumors, respectively.

Conclusions

This single-institutional case series demonstrates that TN breast cancer, higher stage, and higher histologic grade are associated with earlier brain metastases in multivariate analysis. Additional prospective studies are warranted to investigate the impact of brain metastases screening on survival outcome in this high-risk defined group.

Knockdown of AKT3 Activates HER2 and DDR Kinases in Bone-Seeking Breast Cancer Cells, Promotes Metastasis In Vivo and Attenuates the TGFβ/CTGF Axis

Bone metastases frequently occur in breast cancer patients and lack appropriate treatment options. Hence, understanding the molecular mechanisms involved in the multistep process of breast cancer bone metastasis and tumor-induced osteolysis is of paramount interest. The serine/threonine kinase AKT plays a crucial role in breast cancer bone metastasis but the effect of individual AKT isoforms remains unclear. Therefore, AKT isoform-specific knockdowns were generated on the bone-seeking MDA-MB-231 BO subline and the effect on proliferation, migration, invasion, and chemotaxis was analyzed by live-cell imaging. Kinome profiling and Western blot analysis of the TGFβ/CTGF axis were conducted and metastasis was evaluated by intracardiac inoculation of tumor cells into NOD scid gamma (NSG) mice. MDA-MB-231 BO cells exhibited an elevated AKT3 kinase activity in vitro and responded to combined treatment with AKT- and mTOR-inhibitors. Knockdown of AKT3 significantly increased migration, invasion, and chemotaxis in vitro and metastasis to bone but did not significantly enhance osteolysis. Furthermore, knockdown of AKT3 increased the activity and phosphorylation of pro-metastatic HER2 and DDR1/2 but lowered protein levels of CTGF after TGFβ-stimulation, an axis involved in tumor-induced osteolysis. We demonstrated that AKT3 plays a crucial role in bone-seeking breast cancer cells by promoting metastatic potential without facilitating tumor-induced osteolysis.

GANT61 and curcumin-loaded PLGA nanoparticles for GLI1 and PI3K/Akt-mediated inhibition in breast adenocarcinoma

Current conventional mono and combination therapeutic strategies often fail to target breast cancer tissue effectively due to tumor heterogeneity comprising cancer stem cells (CSCs) and bulk tumor cells. This is further associated with drug toxicity and resistivity in the long run. A nanomedicine platform incorporating combination anti-cancer treatment might overcome these challenges and generate synergistic anti-cancer effects and also reduce drug toxicity. GANT61 and curcumin were co-delivered via polymeric nanoparticles (NPs) for the first time to elicit enhanced anti-tumor activity against heterogeneous breast cancer cell line MCF-7. We adopted the single-emulsion-solvent evaporation method for the preparation of the therapeutic NPs. The GANT61-curcumin PLGA NPs were characterized for their size, shape and chemical properties, and anti-cancer cell studies were undertaken for the plausible explanation of our hypothesis. The synthesized GANT61-curcumin PLGA NPs had a spherical, smooth surface morphology, and an average size of 347.4 d. nm. The NPs induced cytotoxic effects in breast cancer cells at a mid-minimal dosage followed by cell death via autophagy and apoptosis, reduction in their target protein expression along with compromising the self-renewal property of CSCs as revealed by their in vitro cell studies. The dual-drug NPs thus provide a novel perspective on aiding existing anti-cancer nanomedicine therapies to target a heterogeneous tumor mass effectively.

Cytoplasmic Chaperones Enhance Soluble Expression of Anti-EGFR huscFv in Escherichia coli

Background:

Overexpression of EGFR is associated with carcinogenesis in more than 70% of head and neck cancers. Anti-EGFR monoclonal antibodies bind to the extracellular domain of EGFR and block the EGFR downstream signaling pathway, which results in the suppression of the growth of the tumor cells. Escherichia coli is the preferred system for expressing various recombinant proteins, including single chain antibodies, but the formation of inclusion bodies negatively affects the efficacy of this system. Several strategies have been suggested to solve this problem, notably the utilization of molecular chaperones.

Objectives:

In this study, we attempted to increase the soluble expression of huscfv antibody via co-expression with the cytoplasmic chaperones.

Materials and Methods:

To achieve this purpose, chaperones plasmids pG-KJE8, pGro7, pKjE7, pTf16 and pG-Tf2 encoding cytoplasmic chaperones were co-expressed with the humanized anti-EGFR scFv construct in E. coli. Different temperatures, incubations times, and concentrations of IPTG were used to produce an active antibody with the highest solubility. Results were analyzed by SDS-PAGE. Soluble huscFv was purified by Ni-NTA column and the biologic activity of the recombinant protein was determined by ELISA.

Result:

The results indicated that the highest concentrations of humanized anti-EGFR scFv were obtained by co-expression of huscFv via chaperone plasmid pG-KJE8 with 0.2 mM concentration of inducer (IPTG), culture temperature of 25 °C, and 4 h incubation time after induction.

Conclusion:

In conclusion, co-expression with chaperones could be used as an efficient strategy to produce soluble active ScFvs in E. coli.

Impact of breast cancer cells´ secretome on the brain metastatic niche remodeling

Brain metastases occur in approximately 10-20% of patients with metastatic breast cancer showing a very poor overall survival. Curiously, different molecular subtypes (that show specific gene expression signatures and differential prognostic significance) are associated with different risks for brain metastases development, suggesting that cancer cells harbor specific molecular programs that award them intrinsic advantages to survive in this specific foreign tissue. Emerging data has been revealing that biophysical and/or mechanical properties of the brain extracellular matrix (ECM), along with those of the brain resident cells, play a crucial role in creating the best conditions for survival, colonization and outgrowth of breast cancer cells in this distinct microenvironment. Although several reports show that cancer cells modulate metastatic niches way before they reach the target organ, few data exist for the brain metastatic niche. Indeed, little is known concerning how factors secreted by cancer cells activate brain resident cells and/or modify brain ECM biomechanical properties and how these modifications impact cells´ ability to metastasize the brain. The brain is a particular organ, protected by the blood brain barrier (BBB), and containing exclusive functional units and very special cell types. Additionally, it is the organ with the most singular ECM and biomechanical properties. Thus, this cancer cell-brain metastatic niche interaction must present distinct properties. Consequently, the search for putative molecular markers that modulate the brain pre-metastatic niche, thus promoting the successful metastatic homing of cancer cells, is urgently needed. In this review, we will discuss key aspects regarding breast cancer cells and the brain pre-metastatic niche paracrine communication that is crucial to initiate the metastatic cascade. We will focus on cancer cell`s secretome influence into the brain microenvironment, specifically on its impact on tissue mechanics and on brain resident cells as regulators of the pre-metastatic niche formation, ultimately promoting metastatic colonization.

Multi-Omics Characterization of the Spontaneous Mesenchymal-Epithelial Transition in the PMC42 Breast Cancer Cell Lines

Epithelial-mesenchymal plasticity (EMP), encompassing epithelial-mesenchymal transition (EMT) and mesenchymal-epithelial transition (MET), are considered critical events for cancer metastasis. We investigated chromosomal heterogeneity and chromosomal instability (CIN) profiles of two sister PMC42 breast cancer (BC) cell lines to assess the relationship between their karyotypes and EMP phenotypic plasticity. Karyotyping by GTG banding and exome sequencing were aligned with SWATH quantitative proteomics and existing RNA-sequencing data from the two PMC42 cell lines; the mesenchymal, parental PMC42-ET cell line and the spontaneously epithelially shifted PMC42-LA daughter cell line. These morphologically distinct PMC42 cell lines were also compared with five other BC cell lines (MDA-MB-231, SUM-159, T47D, MCF-7 and MDA-MB-468) for their expression of EMP and cell surface markers, and stemness and metabolic profiles. The findings suggest that the epithelially shifted cell line has a significantly altered ploidy of chromosomes 3 and 13, which is reflected in their transcriptomic and proteomic expression profiles. Loss of the TGFβR2 gene from chromosome 3 in the epithelial daughter cell line inhibits its EMT induction by TGF-β stimulus. Thus, integrative 'omics' characterization established that the PMC42 system is a relevant MET model and provides insights into the regulation of phenotypic plasticity in breast cancer.

Circular RNA profile of breast cancer brain metastasis: identification of potential biomarkers and therapeutic targets

AIM

To explore the circular RNA (circRNA) profile of breast cancer brain metastasis (BCBM).

MATERIALS & METHODS

RNA-seq was performed to identify the circRNA expression profile of brain metastatic breast cancer cell line 231-BR, in comparison with its parental nonspecific metastatic cell line MDA-MB-231.

RESULTS

A total of 215 upregulated and 191 downregulated circRNAs were identified. The expression levels of ten randomly selected majorly altered circRNAs were re-examined by real-time quantitative PCR and agarose gel electrophoresis, and the following alterations were verified: upregulation of hsa_circ_0001944, hsa_circ_0001481, hsa_circ_0000646, hsa_circ_0001006 and hsa_circ_0000732, and downregulation of hsa_circ_0001910, hsa_circ_0008285 and hsa_circ_0000002. CircRNA/miRNA analysis revealed that hsa_circ_0001944 may be involved in BCBM through sponging up miR-509 and interfering with its binding to the downstream targets.

CONCLUSION

This study provides a leading and fundamental circRNA profile of BCBM.

Real-world data on EGFR/ALK gene status and first-line targeted therapy rate in newly diagnosed advanced non-small cell lung cancer patients in Northern China: A prospective observational study

BACKGROUND

Tyrosine kinase inhibitors (TKIs) can significantly prolong overall survival for patients with advanced non-small cell lung cancer (NSCLC) harboring epidermal growth factor receptor (EGFR)-mutation or anaplastic lymphoma kinase (ALK)-rearrangement. However, the real-world evaluation status of ALK/EGFR in China remains unclear.

METHODS

We conducted a prospective study including 1134 patients with cytologically or histologically confirmed advanced NSCLC (stage IIIb-IV) at 12 Chinese hospitals.

RESULTS

The most common evaluation methods were amplification-refractory mutation system for EGFR status and immunohistochemistry targeting D5F3 for ALK status. Among patients with non-squamous, the EGFR mutation rate was 44.1% and the ALK rearrangement rate was 10.0%. Among patients with squamous cell carcinoma, the EGFR mutation rate was 8.3% and the ALK rearrangement rate was 3.7%. Among all patients, gender (HR = 1.7, 95%CI = 1.2-2.4, P = 0.006), smoking history (HR = 1.8, 95%CI = 1.3-2.7, P = 0.001), histology (HR = 5.0, 95%CI = 2.4-10.1, P < 0.001), and brain metastases (HR = 1.5, 95%CI = 1.1-2.2, P = 0.017) were independent predictors of EGFR mutation, while age (HR = 2.6, 95%CI = 1.7-4.1, P < 0.001) was an independent predictor of ALK rearrangement. The median time from tumor diagnosis to EGFR or ALK status confirmation was 7 and 5 days, respectively. Targeted therapy rate was 73.8% in EGFR-positive patients and 51.4% in ALK-positive patients. There was a negative correlation between the first-line targeted therapy rate and the EGFR mutation detection period (r = -0.152, P = 0.02), while no significant correlation among patients with ALK rearrangement (r = -0.179, P = 0.076).

CONCLUSION

Squamous NSCLC patients should also be routinely tested to determine their EGFR/ALK statuses. The first-line targeted therapy rate remains low in Chinese patients with NSCLC.

A Comprehensive Meta-Analysis of Association between EGFR Mutation Status and Brain Metastases in NSCLC

Non-small cell lung cancer (NSCLC) with epidermal growth factor receptor (EGFR) mutation have different clinicopathological characteristics compared with EGFR wild type NSCLC. A growing number of studies focused on the relevance between EGFR mutation status and brain metastases (BM) in NSCLC, but it remains controversial. Therefore, this study performed a comprehensive meta-analysis to untangle this issue. Several electronic databases including Pubmed, Embase, Web of science and Cochrane database were thoroughly searched. The odds ratio (OR) with 95% confidence interval (95%CI) was pooled to evaluate the relevance. Meta-regression analysis and subgroup analysis were conducted according to the heterogeneity. A total of 26 studies were identified finally in this meta-analysis. The overall OR was 1.58 (95%CI: 1.36-1.84), which indicated that EGFR mutation had a positive association with BM of NSCLC. The subgroup analysis resulted from eleven studies with lung adenocarcinoma revealed a higher possibility of BM in NSCLC with EGFR mutation compared with EGFR wild (p < 0.05). There was no significant difference in the risk of BM between NSCLC EGFR exon 19 mutation and exon 21 point mutation (p = 0.23). This meta-analysis suggests that EGFR mutation can be a risk factor for BM in NSCLC.

The Impact of Oncogenic EGFRvIII on the Proteome of Extracellular Vesicles Released from Glioblastoma Cells

Glioblastoma multiforme (GBM) is a highly aggressive and heterogeneous form of primary brain tumors, driven by a complex repertoire of oncogenic alterations, including the constitutively active epidermal growth factor receptor (EGFRvIII). EGFRvIII impacts both cell-intrinsic and non-cell autonomous aspects of GBM progression, including cell invasion, angiogenesis and modulation of the tumor microenvironment. This is, at least in part, attributable to the release and intercellular trafficking of extracellular vesicles (EVs), heterogeneous membrane structures containing multiple bioactive macromolecules. Here we analyzed the impact of EGFRvIII on the profile of glioma EVs using isogenic tumor cell lines, in which this oncogene exhibits a strong transforming activity. We observed that EGFRvIII expression alters the expression of EV-regulating genes (vesiculome) and EV properties, including their protein composition. Using mass spectrometry, quantitative proteomic analysis and Gene Ontology terms filters, we observed that EVs released by EGFRvIII-transformed cells were enriched for extracellular exosome and focal adhesion related proteins. Among them, we validated the association of pro-invasive proteins (CD44, BSG, CD151) with EVs of EGFRvIII expressing glioma cells, and downregulation of exosomal markers (CD81 and CD82) relative to EVs of EGFRvIII-negative cells. Nano-flow cytometry revealed that the EV output from individual glioma cell lines was highly heterogeneous, such that only a fraction of vesicles contained specific proteins (including EGFRvIII). Notably, cells expressing EGFRvIII released EVs double positive for CD44/BSG, and these proteins also colocalized in cellular filopodia. We also detected the expression of homophilic adhesion molecules and increased homologous EV uptake by EGFRvIII-positive glioma cells. These results suggest that oncogenic EGFRvIII reprograms the proteome and uptake of GBM-related EVs, a notion with considerable implications for their biological activity and properties relevant for the development of EV-based cancer biomarkers.

Biotin-Tagged Polysaccharide Vesicular Nanocarriers for Receptor-Mediated Anticancer Drug Delivery in Cancer Cells

Biotin-conjugated multistimuli-responsive polysaccharide vesicular nanocarriers are designed and developed, for the first time, to accomplish receptor-mediated endocytosis in cancer cells and to deliver anticancer drugs to intracellular compartments. For this purpose, a new renewable hydrophobic unit was custom designed with redox-degradable disulfide and enzyme-biodegradable aliphatic ester chemical linkages, and it was conjugated along with biotin on the dextran backbone. The dextran derivative self-assembled into nanovesicles of <200 nm in size, which were characterized by dynamic and static light scattering, electron, and atomic force microscopes. Avidin-HABA assay established the high affinity of biotin-tagged dextran vesicles toward membrane-receptors up to 25 nM concentration. Doxorubicin-hydrochloride (DOX.HCl)-loaded dextran vesicles exhibited stable formulation in phosphate-buffered saline (PBS) and fetal bovine serum (FBS). Redox-degradation by glutathione (GSH) showed 60% drug release, whereas lysosomal esterase enzyme enabled >98% drug release in 12 h. Confocal microscope and flow cytometry-assisted time-dependent cellular uptake studies revealed that the biotin-receptors overexpressed in cervical cancer cells (HeLa) exhibited larger drug accumulation through the receptor-assisted endocytosis process. This process enabled the delivery of higher amount of DOX and significantly enhanced the killing in cancer cells (HeLa) compared to wild-type mouse embryonic fibroblast cells (WT-MEF, normal cells). Control experiments such as biotin pretreatment in cancer cells and energy-suppressed cellular uptake at 4 °C further supported the occurrence of receptor-mediated endocytosis by the biotin-tagged polymer vesicles. This report provides first insights into the targeted polysaccharide vesicle platform, and the proof-of-concept is successfully demonstrated in biotin receptor-overexpressed cervical cancer cells.

Foe or friend? Janus-faces of the neurovascular unit in the formation of brain metastases

Despite the potential obstacle represented by the blood-brain barrier for extravasating malignant cells, metastases are more frequent than primary tumors in the central nervous system. Not only tightly interconnected endothelial cells can hinder metastasis formation, other cells of the brain microenvironment (like astrocytes and microglia) can also be very hostile, destroying the large majority of metastatic cells. However, malignant cells that are able to overcome these harmful mechanisms may benefit from the shielding and even support provided by cerebral endothelial cells, astrocytes and microglia, rendering the brain a sanctuary site against anti-tumor strategies. Thus, cells of the neurovascular unit have a Janus-faced attitude towards brain metastatic cells, being both destructive and protective. In this review, we present the main mechanisms of brain metastasis formation, including those involved in extravasation through the brain vasculature and survival in the cerebral environment.

Targeting Brain-Adaptive Cancer Stem Cells Prohibits Brain Metastatic Colonization of Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) exhibits more traits possessed by cancer stem cells (CSC) than other breast cancer subtypes and is more likely to develop brain metastases. TNBC patients usually have shorter survival time after diagnosis of brain metastasis, suggesting an innate ability of TNBC tumor cells in adapting to the brain. In this study, we establish novel animal models to investigate early tumor adaptation in brain metastases by introducing both patient-derived and cell line-derived CSC-enriched brain metastasis tumorsphere cells into mice. We discovered astrocyte-involved tumor activation of protocadherin 7 (PCDH7)-PLCβ-Ca2+-CaMKII/S100A4 signaling as a mediator of brain metastatic tumor outgrowth. We further identified and evaluated the efficacy of a known drug, the selective PLC inhibitor edelfosine, in suppressing the PCDH7 signaling pathway to prohibit brain metastases in the animal models. The results of this study reveal a novel signaling pathway for brain metastases in TNBC and indicate a promising strategy of metastatic breast cancer prevention and treatment by targeting organ-adaptive cancer stem cells.Significance: These findings identify a compound to block adaptive signaling between cancer stem cells and brain astrocytes. Cancer Res; 78(8); 2052-64. ©2018 AACR.

A retrospective analysis in patients with EGFR-mutant lung adenocarcinoma: is EGFR mutation associated with a higher incidence of brain metastasis?

Lung adenocarcinomas are more commonly associated with brain metastases (BM). Epidermal growth factor receptor (EGFR) mutations have been demonstrated to be both predictive and prognostic for patients with lung adenocarcinoma. We aimed to explore the potential association between EGFR mutation and the risk of BM in pulmonary adenocarcinoma patients. Data of 234 patients from 2007 to 2014 were retrospectively reviewed. A total of 108 patients had EGFR mutations in the entire cohort. Among them, 76 patients developed BM during their disease course. The incidence of BM was statistically higher in patients with EGFR mutations both at initial diagnosis (P=0.014) and at last follow-up (P<0.001). Multivariate logistic regression analysis revealed that EGFR mutation significantly increased the risk of BM at initial diagnosis (OR=2.515, P=0.022). In patients without BM at initial diagnosis, the accumulative rate of subsequent BM was significantly higher with EGFR mutations (P=0.001). Multivariate Cox regression analysis identified EGFR mutation as the only independent risk factor for subsequent BM (HR=3.036, P=0.001). Patients with EGFR mutations demonstrated longer overall survival (OS) after BM diagnosis than patients with wild-type EGFR (P=0.028). Our data suggest that EGFR mutation is an independent predictive and prognostic risk factor for BM and a positive predictive factor for OS in patients with BM.

The impact of EGFR mutations on the incidence and survival of stages I to III NSCLC patients with subsequent brain metastasis

Previous studies have demonstrated the association between EGFR mutations and distant metastasis. However, the association for subsequent brain metastasis (BM) in stages I-III non-small cell lung cancer (NSCLC) patients remains inconclusive. We conducted a retrospective analysis to clarify the impact of EGFR mutations on the incidence of BM and associated survival in patients with stage I-III NSCLC. A total of 491 patients screened for EGFR mutations were retrospectively enrolled. Brain MRI or CT was used to detect the BM. Cumulative incidence of subsequent BM and overall survival (OS) after diagnosis of BM were estimated by the Kaplan-Meier method and compared using log-rank test. We performed Cox proportional hazard regression for predictors of subsequent BM and determinants of OS after BM. The cumulative incidence of BM seemed higher in patients harboring EGFR mutations than those without EGFR mutations although it did not reach statistical significance (hazard ratio [HR] = 1.75, 95% confidence interval [CI] = 0.73~1.81). After adjusting possible confounders, including age, smoking, stage, and tumor size, EGFR mutation became one of the predictors for subsequent BM (HR = 1.89, 95% CI = 1.12~3.17, p = 0.017). Though there was no statistical difference in survival after BM between patients with EGFR mutations and wild-type EGFR (median survival: 17.8 vs. 12.2 months, HR = 0.79, 95% CI = 0.45–1.40), patients with EGFR 19 deletion (Del) tended to have a longer survival after BM than the non-EGFR 19 Del group (median survival: 29.4 vs. 14.3 months, HR 0.58, 95% CI = 0.32–1.09, p = 0.089). In conclusion, our data suggested EGFR mutation to be one of the predictors for subsequent BM in stage I-III patients. Given the small sample size, more studies are warranted to corroborate our results.

Epidermal growth factor receptor mutation and pattern of brain metastasis in patients with non-small cell lung cancer

BACKGROUND/AIMS

We investigated the time taken for patients with metastatic non-small cell lung cancer (NSCLC) to develop brain metastases (BM), as well as their subsequent overall median survival following diagnosis, considering the epidermal growth factor receptor (EGFR) mutational status.

METHODS

We retrospectively investigated the medical records of 259 patients diagnosed with advanced NSCLC from January 2010 to August 2013, who were tested for EGFR mutations. The time from the diagnosis of advanced NSCLC to the development of BM and the overall median survival after BM development (BM-OS) were evaluated and compared by EGFR mutational status.

RESULTS

Sixty-seven patients (25.9%) developed BM. Synchronous BM occurred more often in patients with EGFR mutation type (MT) (n = 20, 27.4%) compared with EGFR wild type (WT) (n = 27, 14.5%, p < 0.009). The median BM-OS was significantly longer in patients with EGFR MT than in those with EGFR WT (25.7 months vs. 3.8 months, p < 0.001), and a similar trend was noticed for patients with synchronous BM (25.7 months for EGFR MT vs. 6.8 months for EGFR WT, p < 0.001). However, in patients with metachronous BM development, the difference in BM-OS between patients with EGFR MT (14.6 months) and EGFR WT (2.5 months) did not reach statistical significance (p = 0.230).

CONCLUSIONS

Synchronous BM was more common in NSCLC patients with EGFR MT than in those with EGFR WT. However, EGFR mutations were associated with significantly longer median BM-OS, especially when the brain was the first metastatic site.

Defining the endpoints: how to measure the efficacy of drugs that are active against central nervous system metastases

Brain metastases (BMs) are the most common cause of malignant central nervous system (CNS) tumors in adults. In the recent past, patients with BMs were excluded from clinical trials, but now, with the advent of new biological and immunological drugs, their inclusion is more common. In the last era response and progression criteria used across clinical trials have defined the importance to consider not only measurement changes of brain lesions but also the modification of parameters related to the metastases such as metabolism of tissue and its pathological features. Magnetic resonance imaging (MRI) represents the first choice in the evaluation of BMs; the computed tomography (CT) scan will be made only in case of MRI's contraindication. CT, MRI and positron emission tomography (PET-CT), may be used to monitor response to treatment as part of clinical and radiological follow up. In the evaluation of response to treatment, MRI shows superior accuracy in comparison to CT; PET-CT is useful in particularly in cases of BMs underwent to locoregional therapies in the differential diagnosis between recurrence or radionecrosis. Now is possible to use functional imaging as CT-perfusion, dynamic susceptibility contrast (DSC) MR imaging, dynamic contrast-enhanced (DCE) MR imaging, diffusion-weighted MR imaging and MR-Spectroscopy in the evaluation of treatment response; these imaging techniques can provide qualitative and quantitative imaging parameters that allow pathophysiologic correlation. In the evaluation of the response to immunotherapy treatments, the immune-related response criteria (irRC) are considered as the gold standard. The irRC utilizes bidimensional measurements, quantifying the tumor dimension using a product of the longest diameter and the longest perpendicular diameter. We analyze clinical and radiological criteria to better define outcome of drugs for BMs from solid tumors in the new era of biological and immunological therapies.

Changing molecular profile of brain metastases compared with matched breast primary cancers and impact on clinical outcomes

Background:

Breast cancer commonly metastasises to the brain, but little is known about changes in the molecular profile of the brain secondaries and impact on clinical outcomes.

Methods:

Patients with samples from brain metastases and matched breast cancers were included. Immunohistochemical analysis for oestrogen receptor, progesterone receptor, p27kip1, cyclin D1, epidermal growth factor receptor, insulin like growth factor 1, insulin like growth factor 1 receptor, vascular endothelial growth factor A, transforming growth factor-β and HER2 receptor was performed. Borderline HER2 results were analysed by fluorescent in situ hybridisation. Levels of expression were compared, with review of effect on clinical outcomes.

Results:

A total of 41 patients were included. Of the patients, 20% had a change in oestrogen receptor or HER2 in their brain metastasis that could affect therapeutic decisions. There were statistically significant rises in brain metastases for p27kip1 (P=0.023) and cyclin D1 (P=0.030) and a fall in vascular endothelial growth factor A (P=0.012). Overall survival from the time of metastasis increased significantly with oestrogen receptor-positive (P=0.005) and progesterone receptor-positive (P=0.013) brain lesions and with a longer duration from diagnosis of the breast primary (P<0.001).

Conclusions:

In this cohort there were phenotypic differences in metastatic brain tumours compared with matched primary breast tumours. These could be relevant for aetiology, and have an impact on prognostication, current and future therapies.

Breast cancer brain metastases: biology and new clinical perspectives

Because of improvements in the treatment of patients with metastatic breast cancer, the development of brain metastases (BM) has become a major limitation of life expectancy and quality of life for many breast cancer patients. The improvement of management strategies for BM is thus an important clinical challenge, especially among high-risk patients such as human epidermal growth factor receptor 2-positive and triple-negative patients. However, the formation of BM as a multistep process is thus far poorly understood. To grow in the brain, single tumor cells must pass through the tight blood–brain barrier (BBB). The BBB represents an obstacle for circulating tumor cells entering the brain, but it also plays a protective role against immune cell and toxic agents once metastatic cells have colonized the cerebral compartment. Furthermore, animal studies have shown that, after passing the BBB, the tumor cells not only require close contact with endothelial cells but also interact closely with many different brain residential cells. Thus, in addition to a genetic predisposition of the tumor cells, cellular adaptation processes within the new microenvironment may also determine the ability of a tumor cell to metastasize. In this review, we summarize the biology of breast cancer that has spread into the brain and discuss the implications for current and potential future treatment strategies.

Stimulus-dependent differences in signalling regulate epithelial-mesenchymal plasticity and change the effects of drugs in breast cancer cell lines

Introduction

The normal process of epithelial mesenchymal transition (EMT) is subverted by carcinoma cells to facilitate metastatic spread. Cancer cells rarely undergo a full conversion to the mesenchymal phenotype, and instead adopt positions along the epithelial-mesenchymal axis, a propensity we refer to as epithelial mesenchymal plasticity (EMP). EMP is associated with increased risk of metastasis in breast cancer and consequent poor prognosis. Drivers towards the mesenchymal state in malignant cells include growth factor stimulation or exposure to hypoxic conditions.

Methods

We have examined EMP in two cell line models of breast cancer: the PMC42 system (PMC42-ET and PMC42-LA sublines) and MDA-MB-468 cells. Transition to a mesenchymal phenotype was induced across all three cell lines using epidermal growth factor (EGF) stimulation, and in MDA-MB-468 cells by hypoxia. We used RNA sequencing to identify gene expression changes that occur as cells transition to a more-mesenchymal phenotype, and identified the cell signalling pathways regulated across these experimental systems. We then used inhibitors to modulate signalling through these pathways, verifying the conclusions of our transcriptomic analysis.

Results

We found that EGF and hypoxia both drive MDA-MB-468 cells to phenotypically similar mesenchymal states. Comparing the transcriptional response to EGF and hypoxia, we have identified differences in the cellular signalling pathways that mediate, and are influenced by, EMT. Significant differences were observed for a number of important cellular signalling components previously implicated in EMT, such as HBEGF and VEGFA.

We have shown that EGF- and hypoxia-induced transitions respond differently to treatment with chemical inhibitors (presented individually and in combinations) in these breast cancer cells. Unexpectedly, MDA-MB-468 cells grown under hypoxic growth conditions became even more mesenchymal following exposure to certain kinase inhibitors that prevent growth-factor induced EMT, including the mTOR inhibitor everolimus and the AKT1/2/3 inhibitor AZD5363.

Conclusions

While resulting in a common phenotype, EGF and hypoxia induced subtly different signalling systems in breast cancer cells. Our findings have important implications for the use of kinase inhibitor-based therapeutic interventions in breast cancers, where these heterogeneous signalling landscapes will influence the therapeutic response.

Electronic supplementary material

The online version of this article (doi:10.1186/s12964-015-0106-x) contains supplementary material, which is available to authorized users.

Kindlin-2 interacts with and stabilizes EGFR and is required for EGF-induced breast cancer cell migration

Epidermal growth factor receptor (EGFR) mediates multiple signaling pathways that regulate cell proliferation, migration and tumor invasion. Kindlin-2 has been known as a focal adhesion molecule that binds to integrin to control cell migration and invasion. However, molecular mechanisms underlying the role of Kindlin-2 in breast cancer progression remain elusive. Here we report that Kindlin-2 interacts with EGFR and mediates EGF-induced breast cancer cell migration. We found that EGF treatment dramatically increases Kindlin-2 expression at both mRNA and protein levels in a variety of cancer cells. Inhibitors specific for EGFR or PI3K blocked Kindlin-2 induction by EGF. Importantly, Kindlin-2 interacted with EGFR kinase domain, which was independent of Kindlin-2 binding to integrin cytoplasmic domain. Intriguingly, Kindlin-2 stabilized EGFR protein by blocking its ubiquitination and degradation. Depletion of Kindlin-2 impaired EGF-induced cell migration. Our results demonstrated that Kindlin-2 participates in EGFR signaling and regulates breast cancer progression.

βIII-Tubulin Regulates Breast Cancer Metastases to the Brain

Brain metastases occur in about 10% to 30% of breast cancer patients, which culminates in a poor prognosis. It is, therefore, critical to understand the molecular mechanisms underlying brain metastatic processes to identify relevant targets. We hypothesized that breast cancer cells must express brain-associated markers that would enable their invasion and survival in the brain microenvironment. We assessed a panel of brain-predominant markers and found an elevation of several neuronal markers (βIII-tubulin, Nestin, and AchE) in brain metastatic breast cancer cells. Among these neuronal predominant markers, in silico analysis revealed overexpression of βIII-tubulin (TUBB3) in breast cancer brain metastases (BCBM) and its expression was significantly associated with distant metastases. TUBB3 knockdown studies were conducted in breast cancer models (MDA-Br, GLIM2, and MDA-MB-468), which revealed significant reduction in their invasive capabilities. MDA-Br cells with suppressed TUBB3 also demonstrated loss of key signaling molecules such as β3 integrin, pFAK, and pSrc in vitro. Furthermore, TUBB3 knockdown in a brain metastatic breast cancer cell line compromised its metastatic ability in vivo, and significantly improved survival in a brain metastasis model. These results implicate a critical role of TUBB3 in conferring brain metastatic potential to breast cancer cells.

Enhanced antitumor effects of the BRBP1 compound peptide BRBP1-TAT-KLA on human brain metastatic breast cancer

Novel molecularly targeted agents that block the development and metastasis of human brain metastatic breast cancer hold great promise for their translational value. In this study, we constructed a novel targeting composite peptide BRBP1-TAT-KLA comprising of three elements: a brain metastatic breast carcinoma cell (231-BR)-binding peptide BRBP1, a cell penetrating peptide TAT, and a proapoptotic peptide KLA. This composite peptide efficiently internalized in 231-BR cells and consequently induced mitochondrial damage and cellular apoptosis. Exposure of 231-BR cells to BRBP1-TAT-KLA significantly decreased cell viability and increased apoptosis compared with the cells treated with the control peptides. In vivo relevance of these findings was further corroborated in the 231-BR tumor-bearing mice that demonstrated significantly delayed tumor development and metastasis following administration of BRBP1-TAT-KLA compared with those treated with TAT-KLA alone. Interestingly, BRBP1-TAT-KLA inhibited the formation of both large and micro-metastases, while TAT-KLA alone failed to significantly reduce micro-metastases in the breast cancer brain metastasis mice. BRBP1-TAT-KLA selectively homed to the tumors in vivo where it induced cellular apoptosis without significant toxicity on non-tumor tissues. Our findings therefore demonstrated the enhanced antitumor effects of the BRBP1 compound peptide BRBP1-TAT-KLA, providing insights toward development of a potential therapeutic strategy for brain metastatic breast cancer.

Value of oncogenes for the prediction of brain metastases at initial diagnosis: a review of published data

Identifying cancer patients who are at high risk of developing brain metastases at initial diagnosis and applying effective intervention or monitoring strategies is of vital importance. Recent advances in the biology of brain metastases revealed that some oncogenes from primary tumors may be potential markers for identifying cancer patients likely to metastasize to the brain. We here summarize data on the mechanisms of brain metastases supporting the involvement of oncogene changes in the brain metastatic evolution. We also review the available evidence on clinical studies of oncogenes in the prediction of cancer patients with high incidence of brain metastases.

EGFR mutation and brain metastasis in pulmonary adenocarcinomas

BACKGROUND

This study aimed to explore the potential association of mutation in the epidermal growth factor receptor (EGFR) with brain metastases in patients with pulmonary adenocarcinoma.

METHODS

We analyzed clinical data on 314 patients who were tested for EGFR mutation and underwent brain magnetic resonance imaging at diagnosis. The relationship between EGFR mutation status and brain metastases at the initial presentation was analyzed. In addition, prognostic significance of EGFR mutational status on the risk of brain metastasis was evaluated in subgroups of surgically treated patients.

RESULTS

Of the 314 patients, 138 patients (43.9%) had EGFR mutations. The frequency of EGFR mutation was statistically higher for patients with brain metastases (64.7%, brain metastases; 39.8%, no metastases; 40.2%, extracranial metastases; p = 0.005). A strong association between EGFR mutation status and brain metastasis was observed (adjusted odds ratio = 3.83, p = 0.001), whereas no association was observed between EGFR mutation status and extracranial metastases (adjusted odds ratio = 1.73, p = 0.079). In addition, the number of brain metastases was significantly correlated with the EGFR mutation status (p = 0.029). Further analysis of 133 patients treated with surgical resection showed that EGFR mutation status was a poor prognostic factor for the risk of brain metastasis (hazard ratio = 4.49, p = 0.026) after adjustment for pathologic N stage.

CONCLUSIONS

We found a significant association between EGFR mutation and risk of brain metastases at the time of diagnosis and follow-up after curative resection for pulmonary adenocarcinoma. This result indicates the distinct clinical features of EGFR-mutated tumors in terms of brain metastases.

ErbB targeting inhibitors repress cell migration of esophageal squamous cell carcinoma and adenocarcinoma cells by distinct signaling pathways

ErbB family receptor tyrosine kinases (ErbBs) play a role in cell adhesion and migration and are frequently overexpressed in esophageal squamous cell carcinomas (ESCCs) or esophageal adenocarcinomas (EACs). Targeting ErbBs by tyrosine kinase inhibitors (TKIs) may therefore limit esophageal cancer cell migration. Here, we studied the impact of TKIs on ErbB dimerization, cell signaling pathways, and cell migration in three esophageal cell lines: OE21 (ESCC), OE33 (EAC), and Het-1A (non-neoplastic esophageal epithelium). In OE21 cells, the TKIs erlotinib, gefitinib, and lapatinib slightly affected epidermal growth factor receptor EGFR/EGFR, but not EGFR/HER2 dimerization as detected by in situ proximity ligation assay (in situ PLA). Still, TKIs inhibited ERK1/2, Akt, STAT3, and RhoA activity in OE21 cells, as assessed by Western blot, antibody arrays, and Rho GTPase effector pull-down assays. This was accompanied by reduced OE21 cell migration, induction of focal adhesions, and actin cytoskeleton reorganization, as shown by Oris™ migration assay and focal adhesion kinase (FAK)/phalloidin staining. In contrast, in OE33 cells, only lapatinib decreased STAT5, Src family kinase (SFK), and FAK activity as well as β-catenin expression. This impeded cell migration and induced morphological changes in OE33 cells. No alterations were seen for the non-neoplastic Het-1A cells. Thus, we identified the ErbB signaling network as regulator of esophageal cancer cell's actin cytoskeleton, focal adhesions, and cell migration. ErbB targeted TKIs therefore also limit ESCC and EAC cell motility and migration.

KEY MESSAGE

Clinical tyrosine kinase inhibitors (TKIs) reduce esophageal cancer cell migration. Loss of cell migration is linked to reduced Akt, ERK1/2, STAT (3 or 5), FAK, SFKs, and RhoA activity. Clinical TKIs act via distinct signaling in the two main histotypes of esophageal cancer.

Identification and characterization of a novel phage display-derived peptide with affinity for human brain metastatic breast cancer

A novel peptide, BRBP1 (MYPWTEPSYLSN), was identified using an in vitro phage biopanning strategy against human brain-seeking breast carcinoma cells (231-BR cells).The peptide-phage clone, BRBP1-M13 displaying BRBP1 sequence, specifically bound to 231-BR cells and the binding could be competitively abolished by BRBP1. In vivo distribution studies showed that BRBP1-M13 preferentially homed to the 231-BR tumors. Fluorescently-labeled BRBP1, BRBP1-K(5-TAMRA), preferentially bound to 231-BR cells in a dose-dependent and energy-dependent manner and it was efficiently internalized into the cells after 2 h incubation. Near-infrared fluorophores imaging demonstrated the accumulation of Cy5.5-conjugated BRBP1 peptide in the tumors in vivo. Thus, BRBP1 is a promising peptide binding to human brain metastatic breast cancer and it may be applied to targeted delivery of cytotoxic agents to the intended tumor.

Current approaches to the treatment of metastatic brain tumours

Metastatic tumours involving the brain overshadow primary brain neoplasms in frequency and are an important complication in the overall management of many cancers. Importantly, advances are being made in understanding the molecular biology underlying the initial development and eventual proliferation of brain metastases. Surgery and radiation remain the cornerstones of the therapy for symptomatic lesions; however, image-based guidance is improving surgical technique to maximize the preservation of normal tissue, while more sophisticated approaches to radiation therapy are being used to minimize the long-standing concerns over the toxicity of whole-brain radiation protocols used in the past. Furthermore, the burgeoning knowledge of tumour biology has facilitated the entry of systemically administered therapies into the clinic. Responses to these targeted interventions have ranged from substantial toxicity with no control of disease to periods of useful tumour control with no decrement in performance status of the treated individual. This experience enables recognition of the limits of targeted therapy, but has also informed methods to optimize this approach. This Review focuses on the clinically relevant molecular biology of brain metastases, and summarizes the current applications of these data to imaging, surgery, radiation therapy, cytotoxic chemotherapy and targeted therapy.

Breaking and entering into the CNS: clues from solid tumor and nonmalignant models with relevance to hematopoietic malignancies

Various malignancies invade the CNS sanctuary site, accounting for the vast majority of CNS neoplastic foci and contributing to significant morbidity as well as mortality. The blood-brain barrier (BBB) exhibits considerable impermeability to chemotherapeutic agents, severely limiting therapeutic options available for patients developing metastatic CNS involvement, accounting for poor outcomes. The mechanisms by which malignant cells breach the highly exclusive BBB and subsequently survive in this unique anatomical site remain poorly understood, with most of the current knowledge stemming from nonmalignant and solid malignancy models. While solid and hematologic malignancies may face different challenges once within the CNS (e.g., solid tumor parenchymal metastasis compared to masses/nodules/leptomeningeal disease in hematologic malignancies), commonality exists in the process of migrating across the BBB from the circulation. Specifically considering this last point, this review aims to survey the current mechanistic knowledge regarding malignant migration across the BBB, necessarily emphasizing the better studied solid tumor and nonmalignant models with the intention of highlighting both the current knowledge gap and additional work required to effectively consider how hematopoietic malignancies breach the CNS.

SMURF1 plays a role in EGF-induced breast cancer cell migration and invasion

Epidermal growth factor (EGF) is a well-known growth factor that induces cancer cell migration and invasion. Previous studies have shown that SMAD ubiquitination regulatory factor 1 (SMURF1), an E3 ubiquitin ligase, regulates cell motility by inducing RhoA degradation. Therefore, we examined the role of SMURF1 in EGF-induced cell migration and invasion using MDA-MB-231 cells, a human breast cancer cell line. EGF increased SMURF1 expression at both the mRNA and protein levels. All ErbB family members were expressed in MDA-MB-231 cells and receptor tyrosine kinase inhibitors specific for the EGF receptor (EGFR) or ErbB2 blocked the EGF-mediated induction of SMURF1 expression. Within the signaling pathways examined, ERK1/2 and protein kinase C activity were required for EGF-induced SMURF1 expression. The overexpression of constitutively active MEK1 increased the SMURF1 to levels similar to those induced by EGF. SMURF1 induction by EGF treatment or by the overexpression of MEK1 or SMURF1 resulted in enhanced cell migration and invasion, whereas SMURF1 knockdown suppressed EGF- or MEK1-induced cell migration and invasion. EGF treatment or SMURF1 overexpression decreased the endogenous RhoA protein levels. The overexpression of constitutively active RhoA prevented EGF- or SMURF1-induced cell migration and invasion. These results suggest that EGFinduced SMURF1 plays a role in breast cancer cell migration and invasion through the downregulation of RhoA.

Novel modeling of cancer cell signaling pathways enables systematic drug repositioning for distinct breast cancer metastases

A new type of signaling network element, called cancer signaling bridges (CSB), has been shown to have the potential for systematic and fast-tracked drug repositioning. On the basis of CSBs, we developed a computational model to derive specific downstream signaling pathways that reveal previously unknown target-disease connections and new mechanisms for specific cancer subtypes. The model enables us to reposition drugs based on available patient gene expression data. We applied this model to repurpose known or shelved drugs for brain, lung, and bone metastases of breast cancer with the hypothesis that cancer subtypes have their own specific signaling mechanisms. To test the hypothesis, we addressed specific CSBs for each metastasis that satisfy (i) CSB proteins are activated by the maximal number of enriched signaling pathways specific to a given metastasis, and (ii) CSB proteins are involved in the most differential expressed coding genes specific to each breast cancer metastasis. The identified signaling networks for the three types of breast cancer metastases contain 31, 15, and 18 proteins and are used to reposition 15, 9, and 2 drug candidates for the brain, lung, and bone metastases. We conducted both in vitro and in vivo preclinical experiments as well as analysis on patient tumor specimens to evaluate the targets and repositioned drugs. Of special note, we found that the Food and Drug Administration-approved drugs, sunitinib and dasatinib, prohibit brain metastases derived from breast cancer, addressing one particularly challenging aspect of this disease.

CD95L cell surface cleavage triggers a prometastatic signaling pathway in triple-negative breast cancer

Triple-negative breast cancers (TNBC) lacking estrogen and progesterone receptors and HER2 amplification have a relatively high risk of metastatic dissemination, but the mechanistic basis for this risk is not understood. Here, we report that serum levels of CD95 ligand (CD95L) are higher in patients with TNBC than in other patients with breast cancer. Metalloprotease-mediated cleavage of CD95L expressed by endothelial cells surrounding tumors generates a gradient that promotes cell motility due to the formation of an unconventional CD95-containing receptosome called the motility-inducing signaling complex. The formation of this complex was instrumental for Nox3-driven reactive oxygen species generation. Mechanistic investigations revealed a Yes-Orai1-EGFR-PI3K pathway that triggered migration of TNBC cells exposed to CD95L. Our findings establish a prometastatic function for metalloprotease-cleaved CD95L in TNBCs, revisiting its role in carcinogenesis.

Metastasis of Breast Tumor Cells to Brain Is Suppressed by Phenethyl Isothiocyanate in a Novel In Vivo Metastasis Model

Breast tumor metastasis is a leading cause of cancer-related deaths worldwide. Breast tumor cells frequently metastasize to brain and initiate severe therapeutic complications. The chances of brain metastasis are further elevated in patients with HER2 overexpression. In the current study, we evaluated the anti-metastatic effects of phenethyl isothiocyanate (PEITC) in a novel murine model of breast tumor metastasis. The MDA-MB-231-BR (BR-brain seeking) breast tumor cells stably transfected with luciferase were injected into the left ventricle of mouse heart and the migration of cells to brain was monitored using a non-invasive IVIS bio-luminescent imaging system. In order to study the efficacy of PEITC in preventing the number of tumor cells migrating to brain, mice were given 10 µmol PEITC by oral gavage for ten days prior to intra-cardiac injection of tumor cells labeled with quantum dots. To evaluate the tumor growth suppressive effects, 10 µmol PEITC was given to mice every day starting 14^th day after intra-cardiac cell injection. Based on the presence of quantum dots in the brain section of control and treated mice, our results reveal that PEITC significantly prevented the metastasis of breast cancer cells to brain. Our results demonstrate that the growth of metastatic brain tumors in PEITC treated mice was about 50% less than that of control. According to Kaplan Meir’s curve, median survival of tumor bearing mice treated with PEITC was prolonged by 20.5%. Furthermore as compared to controls, we observed reduced HER2, EGFR and VEGF expression in the brain sections of PEITC treated mice. To the best of our knowledge, our study for the first time demonstrates the anti-metastatic effects of PEITC in vivo in a novel breast tumor metastasis model and provides the rationale for further clinical investigation.

Frequent overexpression of ErbB--receptor family members in brain metastases of non-small cell lung cancer patients

The ErbB receptor family has been implicated in brain metastases (BM) formation in various cancer types and specific targeted therapies are available. We investigated the overexpression of EGFR, HER2 and HER3 in BM of non-small cell lung cancer (NSCLC) patients to get a better insight on pathobiology of BM and potential drugable targets. We performed immunohistochemical analysis of EGFR, HER2 and HER3 on tissue microarrays of 131 NSCLC-BM. Fifty-one of 131 (38.9%) specimens were considered as positive for EGFR overexpression, 12/131 (9.2%) for HER2 and 27/131 (20.6%) for HER3 respectively. Sixty-nine of 131 (52.7%) of the cases showed overexpression of at least one marker. Four of 131 (3.1%) were positive for all three markers. Strong correlation was observed between HER2 and HER3 overexpression (p = 0.009; Chi-square test after Bonferroni-Holmes correction). No statistically significant correlation of EGFR, HER2 or HER3 overexpression with clinico-pathological parameters including overall survival times was observed. We observed overexpression of ErbB receptor family members, which represent established therapeutic targets in various primary tumours, in approximately half of NSCLC-BM. Further studies should investigate the role of the ErbB pathway in development of and as a therapeutic target in BM of NSCLC patients.

Real-time motion analysis reveals cell directionality as an indicator of breast cancer progression

Cancer cells alter their migratory properties during tumor progression to invade surrounding tissues and metastasize to distant sites. However, it remains unclear how migratory behaviors differ between tumor cells of different malignancy and whether these migratory behaviors can be utilized to assess the malignant potential of tumor cells. Here, we analyzed the migratory behaviors of cell lines representing different stages of breast cancer progression using conventional migration assays or time-lapse imaging and particle image velocimetry (PIV) to capture migration dynamics. We find that the number of migrating cells in transwell assays, and the distance and speed of migration in unconstrained 2D assays, show no correlation with malignant potential. However, the directionality of cell motion during 2D migration nicely distinguishes benign and tumorigenic cell lines, with tumorigenic cell lines harboring less directed, more random motion. Furthermore, the migratory behaviors of epithelial sheets observed under basal conditions and in response to stimulation with epidermal growth factor (EGF) or lysophosphatitic acid (LPA) are distinct for each cell line with regard to cell speed, directionality, and spatiotemporal motion patterns. Surprisingly, treatment with LPA promotes a more cohesive, directional sheet movement in lung colony forming MCF10CA1a cells compared to basal conditions or EGF stimulation, implying that the LPA signaling pathway may alter the invasive potential of MCF10CA1a cells. Together, our findings identify cell directionality as a promising indicator for assessing the tumorigenic potential of breast cancer cell lines and show that LPA induces more cohesive motility in a subset of metastatic breast cancer cells.

PTP1B expression is an independent positive prognostic factor in human breast cancer

Protein tyrosine phosphatase 1B (PTP1B) is a non-transmembrane protein tyrosine phosphatase that has come into focus as a critical regulator of multiple signaling pathways. The role of PTP1B in breast cancer remains unclear with evidence suggesting that PTP1B can exert both tumor-suppressing and tumor-promoting effects. To better define the role of PTP1B in human breast cancer, and its relationship with HER2, we performed immunohistochemical studies on a large cohort of functionally annotated primary breast cancer specimens. 683 of 1,402 (49 %) evaluable primary breast cancers are positive for PTP1B. There is no statistically significant association between PTP1B expression and age, tumor size, T stage, histologic grade, lymph node status, or histological subtype. Of note, there is no significant association between PTP1B expression and HER2 expression (PTP1B expression 53.1 % in HER2(+) cancers vs. 47.5 % in HER2(-) cancers, p = 0.0985). However, PTP1B expression is significantly associated with estrogen receptor expression (PTP1B expression 50.7 % in ER(+) cancers vs. 43.1 % in ER(-) cancers, p = 0.0137) and intrinsic molecular subtype (PTP1B expression 53.9 % in the luminal B HER2(+) subtype and 37.9 % in the basal-like subtype). Of note, multivariate analyses demonstrate that PTP1B is an independent predictor of improved survival in breast cancer (HR 0.779, p = 0.006). Taken together, we demonstrate in the largest study to date that (1) PTP1B is commonly expressed in breast cancer, (2) there is no association or functional impact of PTP1B expression in HER2(+) breast cancer, and (3) PTP1B expression in breast cancer is associated with significantly improved clinical outcome. Until additional studies are performed, caution should be exercised in using PTP1B inhibitors in human breast cancer.

An essential role of metalloprotease-disintegrin ADAM12 in triple-negative breast cancer

In the absence of HER2 overexpression, triple-negative breast cancers (TNBCs) rely on signaling by epidermal growth factor receptor (EGFR/ErbB1/HER1) to convey growth signals and stimulate cell proliferation. Soluble EGF-like ligands are derived from their transmembrane precursors by ADAM proteases, but the identity of the ADAM that is primarily responsible for ligand release and activation of EGFR in TNBCs is not clear. Using publicly available gene expression data for patients with lymph node-negative breast tumors who did not receive systemic treatment, we show that ADAM12L is the only ADAM with an expression level significantly associated with decreased distant metastasis-free survival times. Similar effect was not observed for patients with ER-negative non-TNBCs. There was a positive correlation between ADAM12L and HB-EGF and EGFR in TNBCs, but not in ER-negative non-TNBCs. We further demonstrate that ectopic expression of ADAM12L increased EGFR phosphorylation in a mouse intraductal xenograft model of early breast cancer. Finally, we detect strong correlation between the level of anti-ADAM12L and anti-phospho-EGFR immunostaining in human breast tumors using tissue microarrays. These studies suggest that ADAM12L is the primary protease responsible for the activation of EGFR in early stage, lymph node-negative TNBCs. Thus, our results may provide novel insight into the biology of TNBC.

A comparison of epithelial-to-mesenchymal transition and re-epithelialization

Wound healing and cancer metastasis share a common starting point, namely, a change in the phenotype of some cells from stationary to motile. The term, epithelial-to-mesenchymal transition (EMT) describes the changes in molecular biology and cellular physiology that allow a cell to transition from a sedentary cell to a motile cell, a process that is relevant not only for cancer and regeneration, but also for normal development of multicellular organisms. The present review compares the similarities and differences in cellular response at the molecular level as tumor cells enter EMT or as keratinocytes begin the process of re-epithelialization of a wound. Looking toward clinical interventions that might modulate these processes, the mechanisms and outcomes of current and potential therapies are reviewed for both anti-cancer and pro-wound healing treatments related to the pathways that are central to EMT. Taken together, the comparison of re-epithelialization and tumor EMT serves as a starting point for the development of therapies that can selectively modulate different forms of EMT.