The Presence of EpCAM(-)/CD49f(+) Cells in Breast Cancer Is Associated with a Poor Clinical Outcome

Breast cancer patient-derived organoids for the investigation of patient-specific tumour evolution

BACKGROUND

A reliable preclinical model of patient-derived organoids (PDOs) was developed in a case study of a 69-year-old woman diagnosed with breast cancer (BC) to investigate the tumour evolution before and after neoadjuvant chemotherapy and surgery. The results were achieved due to the development of PDOs from tissues collected before (O-PRE) and after (O-POST) treatment.

METHODS

PDO cultures were characterized by histology, immunohistochemistry (IHC), transmission electron microscopy (TEM), scanning electron microscopy (SEM), confocal microscopy, flow cytometry, real-time PCR, bulk RNA-seq, single-cell RNA sequencing (scRNA-seq) and drug screening.

RESULTS

Both PDO cultures recapitulated the histological and molecular profiles of the original tissues, and they showed typical mammary gland organization, confirming their reliability as a personalized in vitro model. Compared with O-PRE, O-POST had a greater proliferation rate with a significant increase in the Ki67 proliferation index. Moreover O-POST exhibited a more stem-like and aggressive phenotype, with increases in the CD24low/CD44low and EPCAMlow/CD49fhigh cell populations characterized by increased tumour initiation potential and multipotency and metastatic potential in invasive lobular carcinoma. Analysis of ErbB receptor expression indicated a decrease in HER-2 expression coupled with an increase in EGFR expression in O-POST. In this context, deregulation of the PI3K/Akt signalling pathway was assessed by transcriptomic analysis, confirming the altered transcriptional profile. Finally, transcriptomic single-cell analysis identified 11 cell type clusters, highlighting the selection of the luminal component and the decrease in the number of Epithelial-mesenchymal transition cell types in O-POST.

CONCLUSION

Neoadjuvant treatment contributed to the enrichment of cell populations with luminal phenotypes that were more resistant to chemotherapy in O-POST. PDOs represent an excellent 3D cell model for assessing disease evolution.

Immunotherapy: Constructive Approach for Breast Cancer Treatment

A novel and rapid therapeutic approach is the treatment of human breast cancer by enhancing the host's immune system. In initial findings, program death one (PD-1) and program cell death ligand one (PD-L1) showed positive results towards solid tumors, but tumor relapse and drug resistance are the major concerns. Breast cancer therapy has been transformed by the advent of immune checkpoint blockades (ICBs). Triple-negative breast cancers (TNBCs) have exhibited enduring responses to clinical usage of immune checkpoint inhibitors (ICBs) like atezolizumab and pembrolizumab. Nonetheless, a notable proportion of individuals with TNBC do not experience advantages from these treatments, and there is limited comprehension of the resistance mechanisms. Another approach to overcome resistance is cancer stem cells (CSCs), as these cells are crucial for the initiation and growth of tumors in the body. Various cancer vaccines are created using stem cells (dendritic, whole cell, bacterial) and focus primarily on targeting tumor-related antigens. The ultimate objective of cancer vaccines is to immunize the patients by active artificial immunity against cancer, though. In this review, we primarily focused on existing immunotherapeutic options, immune checkpoint blockers, the latest progress in understanding the molecular mechanisms underlying resistance to immune checkpoint inhibitors (ICBs), advanced strategies to overcome resistance to ICBs, cancer stem cell antigens and molecular markers, ongoing clinical trials for BCs and cancer vaccines for breast cancer.

Cancer stem cells: an insight into the development of metastatic tumors and therapy resistance

The term "cancer stem cells" (CSCs) refers to cancer cells that exhibit traits parallel to normal stem cells, namely the potential to give rise to every type of cell identified in a tumor microenvironment. It has been found that CSCs usually develops from other neoplastic cells or non-cancerous somatic cells by acquiring stemness and malignant characteristics through particular genetic modifications. A trivial number of CSCs, identified in solid and liquid cancer, can give rise to an entire tumor population with aggressive anticancer drug resistance, metastasis, and invasiveness. Besides, cancer stem cells manipulate their intrinsic and extrinsic features, regulate the metabolic pattern of the cell, adjust efflux-influx efficiency, modulate different signaling pathways, block apoptotic signals, and cause genetic and epigenetic alterations to retain their pluripotency and ability of self-renewal. Notably, to keep the cancer stem cells' ability to become malignant cells, mesenchymal stem cells, tumor-associated fibroblasts, immune cells, etc., interact with one another. Furthermore, CSCs are characterized by the expression of particular molecular markers that carry significant diagnostic and prognostic significance. Because of this, scientific research on CSCs is becoming increasingly imperative, intending to understand the traits and behavior of cancer stem cells and create more potent anticancer therapeutics to fight cancer at the CSC level. In this review, we aimed to elucidate the critical role of CSCs in the onset and spread of cancer and the characteristics of CSCs that promote severe resistance to targeted therapy.

Tumour Stem Cells in Breast Cancer

Tumour stem cells (CSCs) are a self-renewing population that plays important roles in tumour initiation, recurrence, and metastasis. Although the medical literature is extensive, problems with CSC identification and cancer therapy remain. This review provides the main mechanisms of CSC action in breast cancer (BC): CSC markers and signalling pathways, heterogeneity, plasticity, and ecological behaviour. The dynamic heterogeneity of CSCs and the dynamic transitions of CSC⁻ non-CSCs and their significance for metastasis are considered.

Terminal differentiation and anti-tumorigenic effects of prolactin in breast cancer

Breast cancer is a major disease affecting women worldwide. A woman has 1 in 8 lifetime risk of developing breast cancer, and morbidity and mortality due to this disease are expected to continue to rise globally. Breast cancer remains a challenging disease due to its heterogeneity, propensity for recurrence and metastasis to distant vital organs including bones, lungs, liver and brain ultimately leading to patient death. Despite the development of various therapeutic strategies to treat breast cancer, still there are no effective treatments once metastasis has occurred. Loss of differentiation and increased cellular plasticity and stemness are being recognized molecularly and clinically as major derivers of heterogeneity, tumor evolution, relapse, metastasis, and therapeutic failure. In solid tumors, breast cancer is one of the leading cancer types in which tumor differentiation state has long been known to influence cancer behavior. Reprograming and/or restoring differentiation of cancer cells has been proposed to provide a viable approach to reverse the cancer through differentiation and terminal maturation. The hormone prolactin (PRL) is known to play a critical role in mammary gland lobuloalveolar development/remodeling and the terminal differentiation of the mammary epithelial cells promoting milk proteins gene expression and lactation. Here, we will highlight recent discoveries supporting an anti-tumorigenic role for PRL in breast cancer as a "pro/forward-differentiation" pathway restricting plasticity, stemness and tumorigenesis.

Microfluidic chip for rapid and selective isolation of tumor-derived extracellular vesicles for early diagnosis and metastatic risk evaluation of breast cancer

The epithelial-to-mesenchymal transition (EMT) index in cancer is a complementary approach for estimating metastatic risk. Considering the demand for evaluating metastatic risk based on liquid biopsies, tumor-derived extracellular vesicles (EVs) can be exploited to generate the EMT index. For the generation of EVs-based EMT index, it is essential to selectively isolate each epithelial cell and mesenchymal cell-derived EVs. This study proposes a novel microfluidic chip for selectively separating two types of EVs in an efficient and timely manner. The microfluidic chip is fully integrated with a micromixer for the creation of efficient collision between EVs and specific antibody-coated microbeads (7 and 15 μm in diameter) and a hydrodynamic particle separator for the stratification of EVs bound microbeads according to the sizes of microbeads. Using this chip, over 90% of EVs expressing the epithelial marker (epithelial cell adhesion molecule, EpCAM) and the mesenchymal marker (CD49f) can be selectively isolated within 6.7 min per 100 μL of sample volume. The clinical relevance of EMT is investigated using plasma samples from 20 breast cancer patients and 10 age-matched controls. The EMT index produced from the microfluidic chip is in a good agreement with the conventional tissue-based EMT index and is significantly high in patients with aggressive breast cancer subtypes, compared with healthy controls. In addition, the patients with high scores on the EMT index (≥5) shows recurrence within 5 years after adjuvant treatment. Predicting EMT-index-based metastatic risk using our microfluidic chip can be beneficial for cancer diagnosis and prognosis.

Vimentin Promotes the Aggressiveness of Triple Negative Breast Cancer Cells Surviving Chemotherapeutic Treatment

Tremendous data have been accumulated in the effort to understand chemoresistance of triple negative breast cancer (TNBC). However, modifications in cancer cells surviving combined and sequential treatment still remain poorly described. In order to mimic clinical neoadjuvant treatment, we first treated MDA-MB-231 and SUM159-PT TNBC cell lines with epirubicin and cyclophosphamide for 2 days, and then with paclitaxel for another 2 days. After 4 days of recovery, persistent cells surviving the treatment were characterized at both cellular and molecular level. Persistent cells exhibited increased growth and were more invasive in vitro and in zebrafish model. Persistent cells were enriched for vimentin^high sub-population, vimentin knockdown using siRNA approach decreased the invasive and sphere forming capacities as well as Akt phosphorylation in persistent cells, indicating that vimentin is involved in chemotherapeutic treatment-induced enhancement of TNBC aggressiveness. Interestingly, ectopic vimentin overexpression in native cells increased cell invasion and sphere formation as well as Akt phosphorylation. Furthermore, vimentin overexpression alone rendered the native cells resistant to the drugs, while vimentin knockdown rendered them more sensitive to the drugs. Together, our data suggest that vimentin could be considered as a new targetable player in the ever-elusive status of drug resistance and recurrence of TNBC.

Comparative stemness and differentiation of luminal and basal breast cancer stem cell type under glutamine-deprivation

Glutamine (gln) metabolism has emerged as a cancer therapeutic target in past few years, however, the effect of gln-deprivation of bCSCs remains elusive in breast cancer. In this study, effect of glutamine on stemness and differentiation potential of bCSCs isolated from MCF-7 and MDAMB-231 were studied. We have shown that bCSCs differentiate into CD24+ epithelial population under gln-deprivation and demonstrated increased expression of epithelial markers such as e-cadherin, claudin-1 and decreased expression of mesenchymal protein n-cadherin. MCF-7-bCSCs showed a decrease in EpCAMhigh population whereas MDAMB-231-bCSCs increased CD44high population in response to gln-deprivation. The expression of intracellular stem cell markers such sox-2, oct-4 and nanog showed a drastic decrease in gene expression under gln-deprived MDAMB-231-bCSCs. Finally, localization of β-catenin in MCF-7 and MDAMB-231 cells showed its accumulation in cytosol or perinuclear space reducing its efficiency to transcribe downstream genes. Conclusively, our study demonstrated that gln-deprivation induces differentiation of bCSCs into epithelial subtypes and also reduces stemness of bCSCs mediated by reduced nuclear localization of β-catenin. It also suggests that basal and luminal bCSCs respond differentially towards changes in extracellular and intracellular gln. This study could significantly affect the gln targeting regimen of breast cancer therapeutics.

Human-derived osteoblast-like cells and pericyte-like cells induce distinct metastatic phenotypes in primary breast cancer cells

Approximately 70% of advanced breast cancer patients will develop bone metastases, which accounts for ∼90% of cancer-related mortality. Breast cancer circulating tumor cells (CTCs) establish metastatic tumors in the bone after a close interaction with local bone marrow cells including pericytes and osteoblasts, both related to resident mesenchymal stem/stromal cells (BM-MSCs) progenitors. In vitro recapitulation of the critical cellular players of the bone microenvironment and infiltrating CTCs could provide new insights into their cross-talk during the metastatic cascade, helping in the development of novel therapeutic strategies. Human BM-MSCs were isolated and fractionated according to CD146 presence. CD146+ cells were utilized as pericyte-like cells (PLCs) given the high expression of the marker in perivascular cells, while CD146- cells were induced into an osteogenic phenotype generating osteoblast-like cells (OLCs). Transwell migration assays were performed to establish whether primary breast cancer cells (3384T) were attracted to OLC. Furthermore, proliferation of 3384T breast cancer cells was assessed in the presence of PLC- and OLC-derived conditioned media. Additionally, conditioned media cultures as well as transwell co-cultures of each OLCs and PLCs were performed with 3384T breast cancer cells for gene expression interrogation assessing their induced transcriptional changes with an emphasis on metastatic potential. PLC as well as their conditioned media increased motility and invasion potential of 3384T breast cancer cells, while OLC induced a dormant phenotype, downregulating invasiveness markers related with migration and proliferation. Altogether, these results indicate that PLC distinctively drive 3384T cancer cells to an invasive and migratory phenotype, while OLC induce a quiescence state, thus recapitulating the different phases of the in vivo bone metastatic process. These data show that phenotypic responses from metastasizing cancer cells are influenced by neighboring cells at the bone metastatic niche during the establishment of secondary metastatic tumors.

Cancer Stem Cells-Origins and Biomarkers: Perspectives for Targeted Personalized Therapies

The use of biomarkers in diagnosis, therapy and prognosis has gained increasing interest over the last decades. In particular, the analysis of biomarkers in cancer patients within the pre- and post-therapeutic period is required to identify several types of cells, which carry a risk for a disease progression and subsequent post-therapeutic relapse. Cancer stem cells (CSCs) are a subpopulation of tumor cells that can drive tumor initiation and can cause relapses. At the time point of tumor initiation, CSCs originate from either differentiated cells or adult tissue resident stem cells. Due to their importance, several biomarkers that characterize CSCs have been identified and correlated to diagnosis, therapy and prognosis. However, CSCs have been shown to display a high plasticity, which changes their phenotypic and functional appearance. Such changes are induced by chemo- and radiotherapeutics as well as senescent tumor cells, which cause alterations in the tumor microenvironment. Induction of senescence causes tumor shrinkage by modulating an anti-tumorigenic environment in which tumor cells undergo growth arrest and immune cells are attracted. Besides these positive effects after therapy, senescence can also have negative effects displayed post-therapeutically. These unfavorable effects can directly promote cancer stemness by increasing CSC plasticity phenotypes, by activating stemness pathways in non-CSCs, as well as by promoting senescence escape and subsequent activation of stemness pathways. At the end, all these effects can lead to tumor relapse and metastasis. This review provides an overview of the most frequently used CSC markers and their implementation as biomarkers by focussing on deadliest solid (lung, stomach, liver, breast and colorectal cancers) and hematological (acute myeloid leukemia, chronic myeloid leukemia) cancers. Furthermore, it gives examples on how the CSC markers might be influenced by therapeutics, such as chemo- and radiotherapy, and the tumor microenvironment. It points out, that it is crucial to identify and monitor residual CSCs, senescent tumor cells, and the pro-tumorigenic senescence-associated secretory phenotype in a therapy follow-up using specific biomarkers. As a future perspective, a targeted immune-mediated strategy using chimeric antigen receptor based approaches for the removal of remaining chemotherapy-resistant cells as well as CSCs in a personalized therapeutic approach are discussed.

Hyaluronic acid induction on breast cancer stem cells unfolds subtype specific variations in stemness and epithelial-to-mesenchymal transition

The reoccurrence of breast cancer is a major concern due to presence of cancer stem cells (CSCs). Considering the key role of hyaluronic acid (HA) in modulating the inflammation and cellular migration in cancer, the response of high molecular weight (HMW) and low molecular weight (LMW) HA towards various subtypes of breast cancer and breast cancer stem cells remain elusive. The aim of this study is to determine the effect of exogenous HMW-HA and LMW-HA on stemness of CSCs and epithelial-to-mesenchymal transition which may help in designing HA based therapeutic strategies. LMW-HA induces EMT in MCF-7 more prominently as compared to MDA-MB-231. However, HMW-HA did not show significant changes in the expression of EMT genes. Surprisingly, both HMW-HA and LMW-HA have shown to decrease the expression of EpCAM in MCF-7 cells and decrease the expression of CD44 in MDAMB-231 cells. HA has maintained the native stem cells phenotype of bCSCs isolated from MCF-7 only. The bCSCs isolated form MDAMB-231 showed a decrease in CD44. Luminal subtype has shown to follow Wnt/β-catenin whereas in the basal subtype localization of CD44 from surface to cytosol was observed in response to HA. Our study has demonstrated that bCSCs in luminal and basal cells follow differential intracellular signaling mechanisms in response to HA. This study could significantly influence the therapeutics involving HA in breast cancer.

Sorafenib Inhibits Proliferation, Migration and Invasion of Breast Cancer Cells

INTRODUCTION

Metastatic breast cancer has poor prognosis due to limited therapeutic options. Protein kinase dysregulations have a major role in breast cancer progression and metastasis. In this study, we investigated the anti-cancer activity of sorafenib, a multikinase inhibitor, which targets receptor tyrosine kinases in breast cancer. Although treatment with sorafenib has increased the patient survival and inhibited metastatic migration in hepatocellular carcinoma, its role in breast cancer migration, metastasis, and intracellular signaling modulation is unknown.

METHODS

Breast cancer cell lines MCF7 and MDA-MB-231 were treated with sorafenib and its effect on proliferation, migration, invasion and gene expression was analyzed.

RESULTS

We found that sorafenib has an anti-proliferative and cytotoxic effect on breast cancer cells. Importantly, sorafenib inhibited the migration and invasion of breast cancer cells in vitro. Mechanistically, sorafenib increased mitochondrial superoxide production, suppressed breast cancer stem cell self-renewal, inhibited epithelial mesenchymal transition and ERK signaling.

CONCLUSION

Thus, sorafenib has anti-cancer activity against breast cancer cells and could improve the survival of breast cancer patients by inhibiting their invasive and metastatic properties.

Peptide-Targeted Polyplexes for Aerosol-Mediated Gene Delivery to CD49f-Overexpressing Tumor Lesions in Lung

Peptide ligands can enhance delivery of nucleic acid-loaded nanoparticles to tumors by promoting their cell binding and internalization. Lung tumor lesions accessible from the alveolar side can be transfected, in principle, using gene vectors delivered as an aerosol. The cell surface marker CD49f (Integrin α6) is frequently upregulated in metastasizing, highly aggressive tumors. In this study, we utilize a CD49f binding peptide coupled to linear polyethylenimine (LPEI) promoting gene delivery into CD49f-overexpressing tumor cells in vitro and into lung lesions in vivo. We have synthesized a molecular conjugate based on LPEI covalently attached to the CD49f binding peptide CYESIKVAVS via a polyethylene glycol (PEG) spacer. Particles formed with plasmid DNA were small (<200 nm) and could be aerosolized without causing major aggregation or particle loss. In vitro, CD49f targeting significantly improved plasmid uptake and reporter gene expression on both human and murine tumor cell lines. For evaluation in vivo, localization and morphology of 4T1 murine triple-negative breast cancer tumor lesions in the lung of syngeneic BALB/c mice were identified by MRI. Polyplexes applied via intratracheal aerosolization were well tolerated and resulted in measurable transgene activity of the reporter gene firefly luciferase in tumor areas by bioluminescence imaging (BLI). Transfectability of tumors correlated with their accessibility for the aerosol. With CD49f-targeted polyplexes, luciferase activity was considerably increased and was restricted to the tumor area.

A multiple breast cancer stem cell model to predict recurrence of T1-3, N0 breast cancer

Background

Local or distant relapse is the key event for the overall survival of early-stage breast cancer after initial surgery. A small subset of breast cancer cells, which share similar properties with normal stem cells, has been proven to resist to clinical therapy contributing to recurrence.

Methods

In this study, we aimed to develop a prognostic model to predict recurrence based on the prevalence of breast cancer stem cells (BCSCs) in breast cancer. Immunohistochemistry and dual-immunohistochemistry were performed to quantify the stem cells of the breast cancer patients. The performance of Cox proportional hazard regression model was assessed using the holdout methods, where the dataset was randomly split into two exclusive sets (70% training and 30% testing sets). Additionally, we performed bootstrapping to overcome a possible biased error estimate and obtain confidence intervals (CI).

Results

Four groups of BCSCs (ALDH1A3, CD44⁺/CD24⁻, integrin alpha 6 (ITGA6), and protein C receptor (PROCR)) were identified as associated with relapse-free survival (RFS). The correlated biomarkers were integrated as a prognostic panel to calculate a relapse risk score (RRS) and to classify the patients into different risk groups (high-risk or low-risk). According to RRS, 67.81 and 32.19% of patients were categorized into low-risk and high-risk groups respectively. The relapse rate at 5 years in the low-risk group (2.67, 95% CI: 0.72–4.63%) by Kaplan-Meier method was significantly lower than that of the high-risk group (19.30, 95% CI: 12.34–26.27%) (p <  0.001). In the multiple Cox model, the RRS was proven to be a powerful classifier independent of age at diagnosis or tumour size (p <  0.001). In addition, we found that high RRS score ER-positive patients do not benefit from hormonal therapy treatment (RFS, p = 0.860).

Conclusion

The RRS model can be applied to predict the relapse risk in early stage breast cancer. As such, high RRS score ER-positive patients do not benefit from hormonal therapy treatment.

Electronic supplementary material

The online version of this article (10.1186/s12885-019-5941-5) contains supplementary material, which is available to authorized users.

Prolactin modulates TNBC aggressive phenotype limiting tumorigenesis

Triple-negative breast cancer (TNBC) accounts for ~20% of all breast cancer cases. The management of TNBC represents a challenge due to its aggressive phenotype, heterogeneity and lack of targeted therapy. Loss of cell differentiation and enrichment with breast cancer stem-like cells (BCSC) are features of TNBC contributing to its aggressive nature. Here, we found that treatment of TNBC cells with PRL significantly depletes the highly tumorigenic BCSC subpopulations CD44+/CD24- and ALDH+ and differentiates them to the least tumorigenic CD44-/CD24- and ALDH- phenotype with limited tumorsphere formation and self-renewal capacities. Importantly, we found PRL to induce a heterochromatin phenotype marked by histone H3 lysine 9 trimethylation (H3K9me3) and accompanied by ultra-structural cellular architecture associated with differentiation and senescence rendering the cells refractory to growth signals. Crucially, we found PRL to mediate these effects in vivo in a pre-clinical animal xenograft of TNBC controlling tumor growth. These results reveal that the lactogenic hormone PRL may exert its anti-tumorigenic effects on TNBC through cellular reprogramming indicative of differentiation resulting in the depletion of BCSCs and restricting tumorigenesis.

Cancer stem cell in breast cancer therapeutic resistance

Development of therapeutic resistance and metastasis is a major challenge with current breast cancer (BC) therapy. Mounting evidence suggests that a subpopulation of cancer stem cells (CSCs) contribute to the cancer therapeutic resistance and metastasis, leading to the recurrence and death in patients. Breast cancer stem cells (BCSCs) are not only a consequence of mutations that overactivate the self-renewal ability of normal stem cells or committed progenitors but also a result of the de-differentiation of cancer cells induced by somatic mutations or microenvironmental components under treatment. Eradication of BCSCs may bring hope and relief to patients whose lives are threatened by recurrent BCs. Therefore, a better understanding of the generation, regulatory mechanisms, and identification of CSCs in BC therapeutic resistance and metastasis will be imperative for developing BCSC-targeted strategies. Here we summarize the latest studies about cell surface markers and signalling pathways that sustain the stemness of BCSC and discuss the associations of mechanisms behind these traits with phenotype and behavior changes in BCSCs. More importantly, their implications for future study are also evaluated and potential BCSC-targeted strategies are proposed to break through the limitation of current therapies.

Mammary Stem Cells and Breast Cancer Stem Cells: Molecular Connections and Clinical Implications

Cancer arises from subpopulations of transformed cells with high tumor initiation and repopulation ability, known as cancer stem cells (CSCs), which share many similarities with their normal counterparts. In the mammary gland, several studies have shown common molecular regulators between adult mammary stem cells (MaSCs) and breast cancer stem cells (bCSCs). Cell plasticity and self-renewal are essential abilities for MaSCs to maintain tissue homeostasis and regenerate the gland after pregnancy. Intriguingly, these properties are similarly executed in breast cancer stem cells to drive tumor initiation, tumor heterogeneity and recurrence after chemotherapy. In addition, both stem cell phenotypes are strongly influenced by external signals from the microenvironment, immune cells and supportive specific niches. This review focuses on the intrinsic and extrinsic connections of MaSC and bCSCs with clinical implications for breast cancer progression and their possible therapeutic applications.

CD49f Can Act as a Biomarker for Local or Distant Recurrence in Breast Cancer

Purpose

Metastasis and local recurrence are the primary causes of treatment failure and patient death in breast cancer. The aim of this study was to validate a metastasis- and local recurrenceassociated biomarker for prognostic evaluation and planning treatment strategies.

Methods

Formalin-fixed, paraffin-embedded tissues from a cohort of 312 patients (all stage II and III) were used. The prevalence of CD49f⁺ cells in the patients' tumors was analyzed and correlated with clinical characteristics to determine its prognostic and clinical implications.

Results

CD49f⁺ tumor cells were found in a minority of tumors, with 62.8% of the samples showing not a single cell of this subtype. In the clinical characteristics analysis, which were performed with t-tests, CD49f⁺ tumors were not associated with age, tumor size, World Health Organization grade, nodal status, human epidermal growth factor receptor 2 status, progesterone receptor status, or estrogen receptor status, although they were significantly associated with disease recurrence (distant metastasis or/and local recurrence). Univariate survival analysis using the Kaplan-Meier method showed that CD49f⁺ tumors were associated with markedly decreased disease-free survival (DFS); the same result was found using multivariate Cox analysis, even when only chemotherapy-treated patients were analyzed.

Conclusion

Our results indicated that breast tumors with CD49f⁺ cancer cells are associated with an increased risk for disease recurrence after initial surgery with poor clinical outcomes (decreased DFS). Therefore, as it requires testing for only one additional protein, adding CD49f testing to conventional surgical pathology is a strategy that has great potential for prognostic and treatment-guidance purposes.

Resistance to Taxanes in Triple-Negative Breast Cancer Associates with the Dynamics of a CD49f+ Tumor-Initiating Population

Taxanes are a mainstay of treatment for breast cancer, but resistance often develops followed by metastatic disease and mortality. Aiming to reveal the mechanisms underlying taxane resistance, we used breast cancer patient-derived orthoxenografts (PDX). Mimicking clinical behavior, triple-negative breast tumors (TNBCs) from PDX models were more sensitive to docetaxel than luminal tumors, but they progressively acquired resistance upon continuous drug administration. Mechanistically, we found that a CD49f+ chemoresistant population with tumor-initiating ability is present in sensitive tumors and expands during the acquisition of drug resistance. In the absence of the drug, the resistant CD49f+ population shrinks and taxane sensitivity is restored. We describe a transcriptional signature of resistance, predictive of recurrent disease after chemotherapy in TNBC. Together, these findings identify a CD49f+ population enriched in tumor-initiating ability and chemoresistance properties and evidence a drug holiday effect on the acquired resistance to docetaxel in triple-negative breast cancer.

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PDX models mimic the clinical response to docetaxel in breast cancer patients

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Sensitivity to docetaxel can be regained in metastatic resistant TNBC

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A tumor-initiating CD49f chemoresistant population is present in TNBC

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Docetaxel resistance associates with the expansion of a CD49f+ population in TNBC

The role of epithelial cell adhesion molecule N-glycosylation on apoptosis in breast cancer cells

Glycosylation of cell surface proteins plays an important role in the regulation of apoptosis. It has been demonstrated that knockdown of epithelial cell adhesion molecule promoted apoptosis, inhibited cell proliferation, and caused cell-cycle arrest. In this study, we investigated whether and how N-glycosylation of epithelial cell adhesion molecule influenced the apoptosis in breast cancer cells. We applied the N-glycosylation mutation epithelial cell adhesion molecule plasmid to express deglycosylation of epithelial cell adhesion molecule and then to study its function. Our results showed that deglycosylation of epithelial cell adhesion molecule promoted apoptosis and inhibited cell proliferation. Deglycosylation of epithelial cell adhesion molecule enhanced the cytotoxic effect of 5-fluorouracil, promoting apoptosis by downregulating the expression of the anti-apoptotic protein Bcl-2 and upregulating the expression of the pro-apoptotic proteins Bax and Caspase 3 via the extracellular-signal-regulated kinase 1/2 and c-Jun N-terminal kinase mitogen-activated protein kinase signaling pathways in MCF-7 and MDA-MB-231 cells. These findings are important for a better understanding of epithelial cell adhesion molecule apoptosis regulation and suggest epithelial cell adhesion molecule as a potential target for the treatment of breast cancer.

ITGA6 is directly regulated by hypoxia-inducible factors and enriches for cancer stem cell activity and invasion in metastatic breast cancer models

Background

Hypoxia-inducible factors (HIFs) are well-established mediators of tumor growth, the epithelial to mesenchymal transition (EMT) and metastasis. In several types of solid tumors, including breast cancers, the HIFs play a critical role in maintaining cancer stem cell (CSC) activity. Thus, we hypothesized that HIFs may also regulate transcription of markers of breast CSC activity. One approach to enrich for breast cells with stem-like phenotypes is FACS sorting, in which sub-populations of live cells are gated based on the expression of cell surface antigens, including various integrin subunits. Integrin alpha 6 (ITGA6; CD49f) is routinely used in combination with other integrin subunits to enrich for breast stem cells by FACS. Integrins not only mediate interactions with the extracellular matrix (ECM), but also drive intracellular signaling events that communicate from the tumor microenvironment to inside of the tumor cell to alter phenotypes including migration and invasion.

Methods

We used two models of metastatic breast cancer (MBC), polyoma middle T (MMTV-PyMT) and MDA-MB-231 cells, to compare the expression of ITGA6 in wild type and knockout (KO) or knockdown cells. Chromatin immunoprecipitation (ChIP) and luciferase reporter assays verified that ITGA6 is a direct HIF transcriptional target. We also used FACS sorting to enrich for CD49f ⁺ cells to compare tumorsphere formation, tumor initiating cell activity, invasion and HIF activity relative to CD49f^{neg or low} cells. Knockdown of ITGA6 significantly reduced invasion, whereas re-expression of ITGA6 in the context of HIF knockdown partially rescued invasion. A search of public databases also revealed that ITGA6 expression is an independent prognostic factor of survival in breast cancer patients.

Results

We report that ITGA6 is a HIF-dependent target gene and that high ITGA6 expression enhances invasion and tumor-initiating cell activities in models of MBC. Moreover, cells that express high levels of ITGA6 are enriched for HIF-1α expression and the expression of HIF-dependent target genes.

Conclusions

Our data suggest that HIF-dependent regulation of ITGA6 is one mechanism by which sorting for CD49f ⁺ cells enhances CSC and metastatic phenotypes in breast cancers. Our results are particularly relevant to basal-like breast cancers which express higher levels of the HIFα subunits, core HIF-dependent target genes and ITGA6 relative to other molecular subtypes.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-016-0510-x) contains supplementary material, which is available to authorized users.