Epithelial-mesenchymal transition and cancer stem cells: a dangerously dynamic duo in breast cancer progression

Plumbagin inhibits cancer stem-like cells, angiogenesis and suppresses cell proliferation and invasion by targeting Wnt/β-catenin pathway in endocrine resistant breast cancer

Fifty percent of advanced stage ER-positive breast cancer patients develop endocrine resistance. Aberrant activation of Wnt/β-catenin is associated with stem-like phenotypes and epithelial-mesenchymal transition (EMT) process which confers resistance to endocrine therapy. Cancer stem-like cells (CSLCs) can be a vital source of proangiogenic factors including fibroblast growth factor 2 (FGF2) which drives angiogenesis and leads to tumor growth and metastasis. Therefore, targeting Wnt and FGF2 may provide effective treatment for endocrine resistant breast cancer. Our previous in vitro study reported that plumbagin (PLB) was a potent anticancer agent and was able to inhibit EMT in endocrine-resistant cells. This study aimed to further investigate the inhibitory effects of PLB on cancer stem-like phenotypes, tumorigenicity and angiogenesis. The results demonstrated Wnt/β-catenin signaling was activated and was able to form mammospheres with increased cancer stem cell markers (ALDH1, NANOG, and OCT4) in endocrine-resistant cells. PLB significantly inhibited colony-forming, mammosphere formation and decreased cancer stem cell markers. The inhibitory effects of PLB on cell proliferation and invasion were mediated by Wnt signaling pathway. PLB also significantly reduced Wnt responsive genes and β-catenin. Moreover, PLB treatment at doses of 2 and 4 mg/kg/day inhibited tumor growth, angiogenesis and metastasis without any adverse effects on body weight and blood coagulation in orthotopic xenograft nude mice. In conclusion, PLB exerted anti-cancer activity and eliminated stem-like properties by attenuating Wnt/β-catenin signaling and FGF2 expression. These findings suggest that PLB could be a promising agent to treat endocrine resistant breast cancer.

The Epithelial to Mesenchymal Transition Promotes Glutamine Independence by Suppressing GLS2 Expression

Identifying bioenergetics that facilitate the epithelial to mesenchymal transition (EMT) in breast cancer cells may uncover targets to treat incurable metastatic disease. Metastasis is the number one cause of cancer-related deaths; therefore, it is urgent to identify new treatment strategies to prevent the initiation of metastasis. To characterize the bioenergetics of EMT, we compared metabolic activities and gene expression in cells induced to differentiate into the mesenchymal state with their epithelial counterparts. We found that levels of GLS2, which encodes a glutaminase, are inversely associated with EMT. GLS2 down-regulation was correlated with reduced mitochondrial activity and glutamine independence even in low-glucose conditions. Restoration of GLS2 expression in GLS2-negative breast cancer cells rescued mitochondrial activity, enhanced glutamine utilization, and inhibited stem-cell properties. Additionally, inhibition of expression of the transcription factor FOXC2, a critical regulator of EMT in GLS2-negative cells, restored GLS2 expression and glutamine utilization. Furthermore, in breast cancer patients, high GLS2 expression is associated with improved survival. These findings suggest that epithelial cancer cells rely on glutamine and that cells induced to undergo EMT become glutamine independent. Moreover, the inhibition of EMT leads to a GLS2-directed metabolic shift in mesenchymal cancer cells, which may make these cells susceptible to chemotherapies.

Detection of Putative Stem-cell Markers in Invasive Ductal Carcinoma of the Breast by Immunohistochemistry: Does It Improve Prognostic/Predictive Assessments?

Introduction:

Experimental evidences from the last 2 decades supports the existence of a special type of neoplastic cell with stem-like features [cancer stem cell (CSC)] and their role in the pathophysiology and therapeutic resistance of breast cancer. However, their clinical value in human breast cancer has not been fully determined.

Materials and Methods:

An immunohistochemistry panel of 10 putative CSC markers (CD34, C-KIT, CD10, SOX-2, OCT 3/4, p63, CD24, CD44, CD133, and ESA/EPCAM) was applied to 74 cases of breast cancer, followed in a Regional Cancer Center of Minas Gerais State, Brazil, from 2004 to 2006. Possible associations between CSC markers and classic variables of clinicopathologic relevance were investigated.

Results:

The most frequently positive CSC markers were CD44, CD24, CD133, and ESA (the others were present in <15% of the cases). Two CSC profiles were defined: CD24⁻/CD44⁺ (CSC-1) and CD133⁺/ESA⁺ (CSC-2). CSC-1 was significantly associated to patients older than 40 years, tumors of <2.0 cm in diameter, early clinical stages (P<0.05), and increased death risk of 4 times (P=0.03; 95% confidence interval, 1.09-14.41). CSC-2 was related to increased relapse risk of 3.75 times (P=0.04; 95% confidence interval, 1.02-13.69).

Conclusion:

The detection of the most frequently positive CSC markers by immunohistochemistry is of clinicopathologic and prognostic relevance.

Dormant disseminated tumor cells and cancer stem/progenitor-like cells: Similarities and opportunities

Distant recurrences occurring years after removal of the primary tumor arise from disseminated tumor cells (DTCs) that lie dormant (quiescent/asymptomatic) until they emerge to overt metastases. These quiescent DTCs are resistant to conventional treatments. Hence, to date there is no available treatment which targets dormant DTCs before they form overt metastases. Therefore, understanding the biology of dormant DTCs and the mechanisms of their reactivation is vital in our pursuit to develop therapies to prevent cancer from ever recurring. This review will address the striking similarities between the biology of DTCs and the biology of cancer stem cells (CSCs) or CSC-like cells including cancer progenitor-like cells. These similarities are related to intrinsic mechanisms of survival and quiescence, and their cross-talk with mediators, produced in their surrounding niches that may support either dormancy or outgrowth. Unraveling these similarities may provide us with exciting opportunities to either mitigate the survival of residing dormant DTCs/CSCs or maintain them in a dormant state. Whether the stemness properties of CSCs/cancer progenitor-like cells already comprising the recurring tumor can be exploited in order to differentiate them, and thus promote their dormancy, will be explored as well. Overall, these emerging concepts may provide us with new opportunities to prevent lethal recurrences.

Low Dose of Paclitaxel Combined with XAV939 Attenuates Metastasis, Angiogenesis and Growth in Breast Cancer by Suppressing Wnt Signaling

Triple-negative breast cancer (TNBC) accounts for 15% of overall breast cancer. A lack of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2 receptor) makes TNBC more aggressive and metastatic. Wnt signaling is one of the important pathways in the cellular process; in TNBC it is aberrantly regulated, which leads to the progression and metastasis. In this study, we designed a therapeutic strategy using a combination of a low dose of paclitaxel and a Wnt signaling inhibitor (XAV939), and examined the effect of the paclitaxel-combined XAV939 treatment on diverse breast cancer lines including TNBC cell lines (MDA-MB-231, MDA-MB-468, and BT549) and ER+ve cell lines (MCF-7 and T-47D). The combination treatment of paclitaxel (20 nM) and XAV939 (10 µM) exerted a comparable therapeutic effect on MDA-MB-231, MDA-MB-468, BT549, MCF-7, and T-47D cell lines, relative to paclitaxel with a high dose (200 nM). The paclitaxel-combined XAV939 treatment induced apoptosis by suppressing Bcl-2 and by increasing the cleavage of caspases-3 and PARP. In addition, the in vivo results of the paclitaxel-combined XAV939 treatment in a mice model with the MDA-MB-231 xenograft further confirmed its therapeutic effect. Furthermore, the paclitaxel-combined XAV939 treatment reduced the expression of β-catenin, a key molecule in the Wnt pathway, which led to suppression of the expression of epithelial-mesenchymal transition (EMT) markers and angiogenic proteins both at mRNA and protein levels. The expression level of E-cadherin was raised, which potentially indicates the inhibition of EMT. Importantly, the breast tumor induced by pristane was significantly reduced by the paclitaxel-combined XAV939 treatment. Overall, the paclitaxel-combined XAV939 regimen was found to induce apoptosis and to inhibit Wnt signaling, resulting in the suppression of EMT and angiogenesis. For the first time, we report that our combination approach using a low dose of paclitaxel and XAV939 could be conducive to treating TNBC and an external carcinogen-induced breast cancer.

Tannic acid attenuates the formation of cancer stem cells by inhibiting NF-κB-mediated phenotype transition of breast cancer cells

Cancer stem cells (CSCs) are innately resistant to standard therapies, which positions CSCs in the focus of anti-cancer research. In this study, we investigated the potential inhibitory effect of tannic acid (TA) on CSCs. Our data demonstrated that TA (10 μM), at the concentration not inhibiting the proliferation of normal mammary cells (MCF10A), inhibited the formation and growth of mammosphere in MCF7, T47D, MDA-MB-231 cells shown as a decrease in mammosphere formation efficiency (MFE), cell number, diameter of mammosphere, and ALDH1 activity. NF-κB pathway was activated in the mammosphere indicated by an up-regulation of p65, a degradation of IκBα, and an increased IL-6. The inhibition of NF-κB pathway via gene silencing of p65 (sip65), NF-κB inhibitor (PDTC), or IKK inhibitor (Bay11-7082) alleviated MFE. Other CSCs markers such as an increase in ALDH1 and CD44^high/CD24^low ratio were ameliorated by sip65. TA also alleviated TGFβ-induced EMT, increase in MFE, and NF-κB activation. In murine xenograft model, TA reduced tumor volume which was associated with a decrease in CD44^high/CD24^low expression and IKK phosphorylation. These results suggest that TA negatively regulates CSCs by inhibiting NF-κB activation and thereby prevents cancer cells from undergoing EMT and CSCs formation, and may thus be a promising therapy targeting CSCs.

Knockdown of XB130 restrains cancer stem cell-like phenotype through inhibition of Wnt/β-Catenin signaling in breast cancer

The cancer stem cells (CSCs) is a subset of cancer cells that possess stem cell properties, which plays a crucial role in the occurrence, metastasis, and recurrence of the tumor. XB130 is a novel adapter protein potentially serves as a functional factor in CSCs. To determine the role of CSCs in breast cancer, we focused on the study of XB130. In our study, we found that XB130 expression was significantly upregulated in breast cancer and was closely related to the clinicopathologic characteristics, overall survival and poor prognosis of breast cancer patients. Functionally, we found that knockdown of XB130 was not only played an important role in proliferation, epithelial-mesenchymal transition (EMT), and metastasis in breast cancer cells but also exhibited potent antitumor activity in animal tumor models. Moreover, we demonstrated that silencing endogenous XB130 regulated the cancer stem cell-like properties of breast cancer, including the formation of self-renewing spheres and the proportion of breast cancer SP⁺ cells. Mechanistically, our studies indicated that downregulation of XB130 restrained the EMT and Wnt/β-catenin signaling, so as to weaken the tumor-initiating cell-like phenotype of breast cancer cells. This study indicates that XB130 plays an important role in maintaining the EMT and stem cell-like characteristics of breast cancer cells, supporting the significance of XB130 as a new potential therapeutic target for early diagnosis and prognosis of breast cancer.

ZnAs@SiO2 nanoparticles as a potential anti-tumor drug for targeting stemness and epithelial-mesenchymal transition in hepatocellular carcinoma via SHP-1/JAK2/STAT3 signaling

Rationale: Current therapies for hepatocellular carcinoma (HCC) are hampered by treatment failure and recurrence due to the remaining treatment-resistant liver cancer stem cells (CSCs). Stemness and epithelial-mesenchymal transition (EMT) are regarded as two fundamental characteristics of liver CSCs necessary for cancer progression; thus, drugs that simultaneously target both characteristics should prove effective in eliminating HCC and impeding recurrence. In this study, we developed new arsenic trioxide (ATO)-based nanoparticles (NPs), which are expected to be more effective than the current HCC therapy, and explored their potential mechanism.

Methods: A “one-pot” reverse emulsification approach was employed to prepare the ZnAs@SiO₂ NPs. HCC cell lines, MHCC97L and Hep3b, were used to analyze the antitumor activity of ZnAs@SiO₂ NPs in vitro and in vivo by quantifying cell growth and metastasis as well as to study the effect on stemness and EMT. SHP-1 siRNA was used to validate the role of the SHP-1/JAK2/STAT3 signaling pathway in mediating inhibition of stemness and EMT by ZnAs@SiO₂.

Results: Compared with the current ATO treatment, ZnAs@SiO₂ NPs promoted apoptosis and significantly inhibited proliferation, migration, and invasion of both MHCC97L and Hep3b cells. In the in vivo assay, ZnAs@SiO₂ NPs inhibited tumor growth by 2.2-fold and metastasis by 3.5-fold as compared to ATO. The ZnAs@SiO₂ NPs also inhibited tumor spheroid formation in vitro and tumor initiation in vivo and induced significant changes in the expression of stemness markers (CD133, Sox-2, and Oct-4) and EMT markers (E-cadherin, Vimentin, and Slug) both in vitro and in vivo. These effects of ZnAs@SiO₂ that correlated with prognosis of HCC were mediated by the SHP-1/JAK2/STAT3 signaling.

Conclusions: ZnAs@SiO₂ NPs can effectively suppress tumor initiation, growth, metastasis, and inhibit stemness and EMT through regulation of SHP-1/JAK2/STAT3 signaling pathway in liver cancer cells in vitro and in vivo. Thus, ZnAs@SiO₂ NPs have immense potential for HCC treatment in the future.

Investigation of specific binding of designed oligodeoxynucleotide decoys to transcription factors in HT29 cell line undergoing epithelial-mesenchymal transition (EMT)

Expression of master transcriptional regulators of stem cells (Oct4 and Sox2) is associated with mediating tumor proliferation and tumor differentiation. The main goal of this study is the investigation of specific binding of designed Oct4-Sox2 transcription factors decoy oligodeoxynucleotides (ODNs) sequence to their nucleus-extracted proteins in HT29-ShE cells containing enriched cancer stem-like cells (SCLCs). First, gene expression of Oct4, Sox2, and E-cadherin revealed the overexpression of Oct4 and Sox2 and downregulation of E-cadherin in HT29-ShE cells compared with HT29 wild-type and HT29-ShC cells. Next, Oct4-Sox2 complex decoy ODNs were designed according to their elements in the promoter region of Sox2 gene. Then, the interactions of Oct4 and Sox2 proteins to designed ODNs were evaluated in silico. Finally, DNA-protein interactions of decoy ODNs and their corresponding proteins were examined by electrophoretic mobility shift assay (EMSA). Analysis of gel shift retardation assay admitted the specific binding of designed ODNs sequence to the nuclear extracted Oct4 and Sox2 proteins. The results will be a promising approach to target cancer stem cells for potential use in differentiation therapy before chemotherapy and radiotherapy of cancers.

Biomaterial Scaffolds Recruit an Aggressive Population of Metastatic Tumor Cells In Vivo

For most cancers, metastasis is the point at which clinical treatment shifts from curative intent to extending survival. Biomaterial implants acting as a synthetic premetastatic niche recruit metastatic cancer cells and provide a survival advantage, and their use as a diagnostic platform requires assessing their relevance to disease progression. Here, we showed that scaffold-captured tumor cells (SCAF) were 30 times more metastatic to the lung than primary tumor (PT) cells, similar to cells derived from lung micrometastases (LUNG). SCAF cells were more aggressive in vitro, demonstrated higher levels of migration, invasion, and mammosphere formation, and had a greater proportion of cancer stem cells than PT. SCAF cells were highly enriched for gene expression signatures associated with metastasis and had associated genomic structural changes, including globally enhanced entropy. Collectively, our findings demonstrate that SCAF cells are distinct from PT and more closely resemble LUNG, indicating that tumor cells retrieved from scaffolds are reflective of cells at metastatic sites. SIGNIFICANCE: These findings suggest that metastatic tumor cells captured by a biomaterial scaffold may serve as a diagnostic for molecular staging of metastasis.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/79/8/2042/F1.large.jpg.

Heterogeneity in Circulating Tumor Cells: The Relevance of the Stem-Cell Subset

The release of circulating tumor cells (CTCs) into vasculature is an early event in the metastatic process. The analysis of CTCs in patients has recently received widespread attention because of its clinical implications, particularly for precision medicine. Accumulated evidence documents a large heterogeneity in CTCs across patients. Currently, the most accepted view is that tumor cells with an intermediate phenotype between epithelial and mesenchymal have the highest plasticity. Indeed, the existence of a meta-stable or partial epithelial–mesenchymal transition (EMT) cell state, with both epithelial and mesenchymal features, can be easily reconciled with the concept of a highly plastic stem-like state. A close connection between EMT and cancer stem cells (CSC) traits, with enhanced metastatic competence and drug resistance, has also been described. Accordingly, a subset of CTCs consisting of CSC, present a stemness profile, are able to survive chemotherapy, and generate metastases after xenotransplantation in immunodeficient mice. In the present review, we discuss the current evidence connecting CTCs, EMT, and stemness. An improved understanding of the CTC/EMT/CSC connections may uncover novel therapeutic targets, irrespective of the tumor type, since most cancers seem to harbor a pool of CSCs, and disclose important mechanisms underlying tumorigenicity.

MicroRNA-4417 is a tumor suppressor and prognostic biomarker for triple-negative breast cancer

Triple-negative breast cancer (TNBC) is the most aggressive form of breast cancer with poor prognosis due to lack of druggable targets such as hormone and growth factor receptors. Therefore, identification of targetable regulators such as miRNAs could provide new avenues for therapeutic applications. Here, we report that the expression of miR-4417 is suppressed during the progression of TNBC cells from non-malignant to the malignant stage. MiR-4417 is localized to chromosome 1p36, a region with high frequency of loss of heterozygosity in multiple cancers, and its biogenesis is DICER-dependent. Low expression of miR-4417 is significantly associated with worse prognosis in TNBC patients, while overexpression of miR-4417 is sufficient to inhibit migration and mammosphere formation of TNBC cells in vitro. Overall, our findings suggest miR-4417 exerts a tumor suppressive effect and thereby could serve as a prognostic biomarker and therapeutic tool against TNBC.

Utilization of NGS technologies to investigate transcriptomic and epigenomic mechanisms in trastuzumab resistance

NGS (Next Generation Sequencing) technologies allows us to determine key gene expression signatures that correlate with resistance (and responsiveness) to anti-cancer therapeutics. We have undertaken a transcriptomic and chromatin immunoprecipitation followed by sequencing (ChIP-seq) approach to describe differences in gene expression and the underlying chromatin landscape between two representative HER2+ cell lines, one of which is sensitive (SKBR3) and the other which is resistant (JIMT1) to trastuzumab. We identified differentially expressed genes (DEGs) and differentially expressed transcripts (DETs) between SKBR3 and JIMT1 cells. Several of the DEGs are components of the Polycomb Repressing Complex 2 (PRC2), and they are expressed higher in JIMT1 cells. In addition, we utilized ChIP-seq to identify H3K18ac, H3K27ac and H3K27me3 histone modifications genome-wide. We identified key differences of H3K18ac and H3K27ac enrichment in regulatory regions, found a correlation between these modifications and differential gene expression and identified a transcription factor binding motif for LRF near these modifications in both cell lines. Lastly, we found a small subset of genes that contain repressive H3K27me3 marks near the gene body in SKBR3 cells but are absent in JIMT1. Taken together, our data suggests that differential gene expression and trastuzumab responsiveness in JIMT1 and SKBR3 is determined by epigenetic mechanisms.

Circulating Tumor Cells: Strategies for Capture, Analyses, and Propagation

Circulating tumor cells (CTCs) play a central role in tumor dissemination and metastases, which are ultimately responsible for most cancer deaths. Technologies that allow for identification and enumeration of rare CTC from cancer patients' blood have already established CTC as an important clinical biomarker for cancer diagnosis and prognosis. Indeed, current efforts to robustly characterize CTC as well as the associated cells of the tumor microenvironment such as circulating cancer associated fibroblasts (cCAF), are poised to unmask key insights into the metastatic process. Ultimately, the clinical utility of CTC will be fully realized once CTC can be reliably cultured and proliferated as a biospecimen for precision management of cancer patients, and for discovery of novel therapeutics. In this review, we highlight the latest CTC capture and analyses technologies, and discuss in vitro strategies for culturing and propagating CTC.

Transcriptomic and ChIP-sequence interrogation of EGFR signaling in HER2+ breast cancer cells reveals a dynamic chromatin landscape and S100 genes as targets

BACKGROUND

The Human Epidermal Growth Factor Receptor (EGFR/HER1) can be activated by several ligands including Transforming Growth Factor alpha (TGF-α) and Epidermal Growth Factor (EGF). Following ligand binding, EGFR heterodimerizes with other HER family members, such as HER2 (human epidermal growth factor receptor-2). Previously, we showed that the EGFR is upregulated in trastuzumab resistant HER2 positive (HER2+) breast cancer cells. This study is aimed to determine the downstream effects on transcription following EGFR upregulation in HER2+ breast cancer cells.

METHODS

RNA-sequence and ChIP-sequence for H3K18ac and H3K27ac (Histone H3 lysine K18 and K27 acetylation) were conducted following an Epidermal Growth Factor (EGF) treatment time course in HER2+ breast cancer cells, SKBR3. The levels of several proteins of interest were confirmed by western blot analysis. The cellular localization of proteins of interest was examined using biochemically fractionated lysates followed by western blot analysis.

RESULTS

Over the course of 24 h, EGFR stimulation resulted in the modulation of over 4000 transcripts. Moreover, our data demonstrates that EGFR/HER2 signaling regulates the epigenome, with global H3K18ac and H3K27ac oscillating as a function of time following EGF treatment. RNA-sequence data demonstrates the activation of immediate early genes (IEGs) and delayed early genes (DEGs) within 1 h of EGF treatment. More importantly, we have identified members of the S100 (S100 Calcium Binding Protein) gene family as likely direct targets of EGFR signaling as H3K18ac, H3K27ac and pol2 (RNA polymerase II) increase near the transcription start sites of some of these genes.

CONCLUSIONS

Our data suggests that S100 proteins, which act as Ca2+ sensors, could play a role in EGF induced tumor cell growth and metastasis, contribute to trastuzumab resistance and cell migration and that they are likely drug targets in HER2+ breast cancer.

Autophagy, cancer stem cells and drug resistance

Autophagy is a cellular survival mechanism that is induced by cancer therapy, among other stresses, and frequently contributes to cancer cell survival during long periods of dormancy and the eventual outgrowth of metastatic disease. Autophagy degrades large cellular structures that, once broken down, contribute to cellular survival through the recycling of their constituent metabolites. However, the extent to which this fuel function of autophagy is key to its role in promoting stemness, dormancy and drug resistance remains to be determined. Other roles for autophagy in determining cell fate more directly through targeted degradation of key transcription factors, such as p53 and FoxO3A, or by enforcing a reversible quiescent growth arrest, are discussed in this review. This review also highlights the need to parse out the roles of different forms of selective autophagy in stemness, CD44 expression and dormancy that, for example, are increasingly being attributed explicitly to mitophagy. The clinical relevance of this work and how an increased understanding of functions of autophagy in stemness, dormancy and drug resistance could be manipulated for increased therapeutic benefit, including eliminating minimal residual disease and preventing metastasis, are discussed. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Toward understanding cancer stem cell heterogeneity in the tumor microenvironment

The epithelial-mesenchymal transition (EMT) and cancer stem cell (CSC) formation are two paramount processes driving tumor progression, therapy resistance, and cancer metastasis. Recent experiments show that cells with varying EMT and CSC phenotypes are spatially segregated in the primary tumor. The underlying mechanisms generating such spatiotemporal dynamics in the tumor microenvironment, however, remain largely unexplored. Here, we show through a mechanism-based dynamical model that the diffusion of EMT-inducing signals such as TGF-β, together with noncell autonomous control of EMT and CSC decision making via the Notch signaling pathway, can explain experimentally observed disparate localization of subsets of CSCs with varying EMT phenotypes in the tumor. Our simulations show that the more mesenchymal CSCs lie at the invasive edge, while the hybrid epithelial/mesenchymal (E/M) CSCs reside in the tumor interior. Further, motivated by the role of Notch-Jagged signaling in mediating EMT and stemness, we investigated the microenvironmental factors that promote Notch-Jagged signaling. We show that many inflammatory cytokines such as IL-6 that can promote Notch-Jagged signaling can (i) stabilize a hybrid E/M phenotype, (ii) increase the likelihood of spatial proximity of hybrid E/M cells, and (iii) expand the fraction of CSCs. To validate the predicted connection between Notch-Jagged signaling and stemness, we knocked down JAG1 in hybrid E/M SUM149 human breast cancer cells in vitro. JAG1 knockdown significantly restricted tumor organoid formation, confirming the key role that Notch-Jagged signaling can play in tumor progression. Together, our integrated computational-experimental framework reveals the underlying principles of spatiotemporal dynamics of EMT and CSCs.

A novel SRC-2-dependent regulation of epithelial-mesenchymal transition in breast cancer cells

Steroid receptor coactivator 2 (SRC-2) is a nuclear receptor coactivator, important for the regulation of estrogen receptor alpha (ERα)-mediated transcriptional activity in breast cancer cells. However, the transcriptional role of SRC-2 in breast cancer is still ambiguous. Here we aimed to unravel a more precise transcriptional role of SRC-2 and uncover unique target genes in MCF-7 breast cancer cells, as opposed to the known oncogene SRC-3. Gene expression analyses of cells depleted of either SRC-2 or SRC-3 showed that they transcriptionally regulate mostly separate gene sets. However, individual unique gene sets were implicated in some of the same major gene ontology biological processes, such as cellular structure and development. This finding was supported by three-dimensional cell cultures, demonstrating that depletion of SRC-2 and SRC-3 changed the morphology of the cells into epithelial-like hollow acinar structures, indicating that both SRC proteins are involved in maintaining the hybrid E/M phenotype. In clinical ER-positive, HER2-negative breast cancer samples the expression of SRC-2 was negatively correlated with the expression of MCF-7-related luminal, cell cycle and cellular morphogenesis genes. Finally, elucidating SRC-2 unique transcriptional effects, we identified Lyn kinase (an EMT biomarker) to be upregulated exclusively after SRC-2 depletion. In conclusion, we show that both SRC-2 and SRC-3 are essential for the EMT in breast cancer cells, controlling different transcriptional niches.

A New Patient-Derived Metastatic Glioblastoma Cell Line: Characterisation and Response to Sodium Selenite Anticancer Agent

Glioblastoma multiform (GBM) tumors are very heterogeneous, organized in a hierarchical pattern, including cancer stem cells (CSC), and are responsible for development, maintenance, and cancer relapse. Therefore, it is relevant to establish new GBM cell lines with CSC characteristics to develop new treatments. A new human GBM cell line, named R2J, was established from the cerebro-spinal fluid (CSF) of a patient affected by GBM with leptomeningeal metastasis. R2J cells exhibits an abnormal karyotype and form self-renewable spheres in a serum-free medium. Original tumor, R2J, cultured in monolayer (2D) and in spheres showed a persistence expression of CD44, CD56 (except in monolayer), EGFR, Ki67, Nestin, and vimentin. The R2J cell line is tumorigenic and possesses CSC properties. We tested in vitro the anticancer effects of sodium selenite (SS) compared to temozolomide TMZ. SS was absorbed by R2J cells, was cytotoxic, induced an oxidative stress, and arrested cell growth in G2M before inducing both necrosis and apoptosis via caspase-3. SS also modified dimethyl-histone-3-lysine-9 (H3K9m2) levels and decreased histone deacetylase (HDAC) activity, suggesting anti-invasiveness potential. This study highlights the value of this new GBM cell line for preclinical modeling of clinically relevant, patient specific GBM and opens a therapeutic window to test SS to target resistant and recurrent GBM.

Epigenetic reprogramming of epithelial mesenchymal transition in triple negative breast cancer cells with DNA methyltransferase and histone deacetylase inhibitors

Background

Triple negative breast cancer (TNBC) is an aggressive neoplasia with no effective therapy. Our laboratory has developed a unique TNBC cell model presenting epithelial mesenchymal transition (EMT) a process known to be important for tumor progression and metastasis. There is increasing evidence showing that epigenetic mechanisms are involved in the activation of EMT. The objective of this study is to epigenetically reverse the process of EMT in TNBC by using DNA methyltransferase inhibitors (DNMTi) and histone deacetylase inhibitors (HDACi).

Methods

We evaluated the antitumor effect of three DNMTi and six HDACi using our TNBC cell model by MTT assay, migration and invasion assay, three dimensional culture, and colony formation assay. We then performed the combined treatment both in vitro and in vivo using the most potent DNMTi and HDACi, and tested the combined treatment in a panel of breast cancer cell lines. We investigated changes of EMT markers and potential signaling pathways associated with the antitumor effects.

Results

We showed that DNMTi and HDACi can reprogram highly aggressive TNBC cells that have undergone EMT to a less aggressive phenotype. SGI-110 and MS275 are superior to other seven compounds being tested. The combination of SGI with MS275 exerts a greater effect than single agent alone in inhibiting cell proliferation, motility, colony formation, and stemness of cancer cells. We also demonstrated that MS275 and the combination of SGI with MS275 exert in vivo antitumor effect. We revealed that the combined treatment synergistically reverses EMT through inhibiting EpCAM cleavage and WNT signaling, suppressing mutant p53, ZEB1, and EZH2, and inducing E-cadherin, apoptosis, as well as histone H3 tri-methylation.

Conclusions

Our study showed that DNMTi and HDACi exert antitumor activity in TNBC cells partially by epigenetically reprograming EMT. Our findings strongly suggest that TNBC is sensitive to epigenetic therapies. Therefore, we propose a new strategy to treat TNBC by using the combination of SGI-110 with MS275, which exerts superior antitumor effects by simultaneously targeting multiple pathways.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-0988-8) contains supplementary material, which is available to authorized users.

Clinicopathological characteristics of metaplastic breast cancer - analysis of the basic immunohistochemical profile and comparison with other invasive breast cancer types

INTRODUCTION

Metaplastic breast cancer (MpBC) is a rare but aggressive type of breast cancer accounting for 0.25-1% of all diagnosed invasive breast cancers. Morphologically, it is characterized by differentiation of the neoplastic epithelium into squamous cells and/or mesenchymal-looking tissue.

MATERIAL AND METHODS

We analyzed 13 MpBCs selected from the group of 1122 invasive breast cancers. Histopathological examination and analysis of estrogen (ER), progesterone (PR) and HER2 receptors expression in MpBC patients and their comparison to other types of invasive breast cancer has been performed.

RESULTS

13 MpBC cases represented 1.16% of the 1122 invasive breast cancers. The MpBC group presented with a significantly larger tumor size (≥T2, 69% versus 49%, p < 0.001) and with higher grade of histological malignancy (G1-G3) (p < 0.001). MpBC group had significantly more cases with no hormone receptors (ER, PR) and HER2 overexpression/gene amplification compared with the other invasive breast cancer types group (ER-, 69% versus 23%, p < 0.001; PR-, 69% versus 28%, p < 0.001; HER2 0/1+, 93% versus 82%, p = 0.019). Most MpBCs (62%) were triple-negative. We found a correlation between hormone receptors expression and lymph node metastasis (p < 0.001). The analysis of the HER2 expression allowed us to find correlation between its expression and tumor histological grade (G1-G3) (p < 0.001), tumor size (T1a-T4) (p < 0.001) and lymph node metastasis (pN0-pN4) (p < 0.001) in MpBCs.

DISCUSSION

MpBCs are usually larger at primary diagnosis and most of MpBCs present with other poor prognostic indicators and show lack of steroid hormone receptors expression as well as HER2. Hormone receptor status and HER2 expression seems to correlate with histological grade of malignancy (G1-G3), tumor size (T1a-T4) and regional lymph node involvement (pN0-pN4) and these features are directly related to MpBC malignancy.

CD24 expression and stem-associated features define tumor cell heterogeneity and tumorigenic capacities in a model of carcinogenesis

Background

Most carcinomas are composed of heterogeneous populations of tumor cells with distinct and apparently stable phenotypic characteristics.

Methods

Using an in vitro model of carcinogenesis we aimed at experimentally elucidating the significance of heterogeneity in the expression of CD24, a marker frequently overexpressed in various cancers and correlated with poor prognosis.

Results

We show that CD24^Neg and CD24^Pos cells issued from the same tumorigenic cell line display striking differences in stem-related properties, expression of epithelial-mesenchymal transition/mesenchymal-epithelial transition markers, and tumorigenic capacity. Indeed, while CD24^Neg cells were as tumorigenic as the parental cell line, CD24^Pos cells, although unable to form tumors, were unexpectedly more mesenchymal, displayed enhanced stemness-related properties, and expressed a proinflammatory signature.

Conclusion

Our findings support the view that acquisition of stem-like cell, CD24-associated, attributes like migration, invasion, and plasticity by a tumor subpopulation is not necessarily related to local tumor growth but may be required for escaping the niche and colonizing distant sites.

Role of autophagy in tumorigenesis, metastasis, targeted therapy and drug resistance of hepatocellular carcinoma

Autophagy is a “self-degradative” process and is involved in the maintenance of cellular homeostasis and the control of cellular components by facilitating the clearance or turnover of long-lived or misfolded proteins, protein aggregates, and damaged organelles. Autophagy plays a dual role in cancer, including in tumor progression and tumor promotion, suggesting that autophagy acts as a double-edged sword in cancer cells. Liver cancer is one of the greatest leading causes of cancer death worldwide due to its high recurrence rate and poor prognosis. Especially in China, liver cancer has become one of the most common cancers due to the high infection rate of hepatitis virus. In primary liver cancer, hepatocellular carcinoma (HCC) is the most common type. Considering the perniciousness and complexity of HCC, it is essential to elucidate the function of autophagy in HCC. In this review, we summarize the physiological function of autophagy in cancer, analyze the role of autophagy in tumorigenesis and metastasis, discuss the therapeutic strategies targeting autophagy and the mechanisms of drug-resistance in HCC, and provide potential methods to circumvent resistance and combined anticancer strategies for HCC patients.

Circulating Tumor Cells with Stemness and Epithelial-to-Mesenchymal Transition Features Are Chemoresistant and Predictive of Poor Outcome in Metastatic Breast Cancer

Circulating tumor cells (CTCs) bearing phenotypes related to cancer stem cells (CSCs) and epithelial-to-mesenchymal transition (EMT) have been identified in breast cancer; however, their clinical significance is not clear. In the current study, we investigated the prognostic relevance of single CSC⁺/partial-EMT⁺ CTCs in patients with metastatic breast cancer and the effect of first-line chemotherapy on their incidence. For this purpose, triple immunofluorescence against cytokeratin, ALDH1, and TWIST1 was performed in peripheral blood mononuclear cell (PBMC) cytospins from 130 patients before and after first-line chemotherapy. CSC⁺/partial-EMT⁺ CTCs were characterized as cells co-expressing cytokeratin, high levels of ALDH1, and nuclear TWIST1. CSC⁺/partial-EMT⁺ CTCs were evident in 27.7% of patients at baseline and were correlated to lung metastases (P = 0.010) and decreased progression-free survival [PFS; median 10.2 (8.9-11.6) vs. 13.5 (11.3-15.7) months; P = 0.024]. Their detection was an independent factor predicting for increased risk of relapse [multivariate analysis; HR (95% confidence interval (CI)): 1.785 (1.171-2.720); P = 0.007]. In HER-2-negative patients, CSC⁺/partial-EMT⁺ CTCs were additionally associated with reduced overall survival (OS) [median 39 (26.2-51.9) vs. 51 (15.7-86.4) months; P = 0.020] and increased risk of death [multivariate analysis; HR (95% CI): 2.228 (1.066-4.655); P = 0.033]. Chemotherapy resulted in a significant increase in the incidence of CSC⁺/partial-EMT⁺ CTCs (mean CTC% per patient: 59.4% post vs. 39.5% pre; P = 0.018), which was subsequently confirmed only in HER2-negative patients (P = 0.040) and in non-responders at the end of treatment (P = 0.020). In conclusion, CSC⁺/partial-EMT⁺ CTCs represent a chemoresistant subpopulation, which independently predicts for unfavorable outcome in metastatic breast cancer. Efficient targeting of these CTCs could potentially increase patient survival.

Resistance of primary breast cancer cells with enhanced pluripotency and stem cell activity to sex hormonal stimulation and suppression

Female sex steroid hormones have a fundamental role in breast cancer. Meanwhile, current evidence supports the contribution of breast cancer stem cells in carcinogenesis, metastasis, and resistance to cytotoxic chemotherapy. Nevertheless, the interaction between breast cancer stem cells with sex hormones or key hormonal antagonists remains elusive.

OBJECTIVE

To investigate the effect of diverse sex hormonal stimulation and suppression regimens on the proliferation of a primary human breast cancer cells with stem cell activity.

METHODS

Cells were exposed to estradiol, progesterone, letrozole, ulipristal acetate, or a combination of ulipristal acetate-letrozole, continually for 6 months. Additionally, nanoparticle-linked letrozole and ulipristal acetate formulations were included in a subsequent short-term exposure study. Phenotypic, pathologic, and functional characteristics of unexposed cells were investigated.

RESULTS

The proliferation of breast cancer cells was comparable among all hormonal stimulation and suppression groups (P= 0.8). In addition, the nanoparticle encapsulated hormonal antagonists were not able to overcome the observed resistance of cells. Cell characterization showed a mesenchymal-like phenotype overexpressing three master pluripotency markers (Oct 4, SOX2, and Nanog), and 92% of cells were expressing ALDH1A1. Notably, the CD44 ^high/CD24 ^low cell population presented only 0.97%-5.4% over repeat analyses. Most cells lacked the expression of mesenchymal markers; however, they showed differentiation into osteogenic and adipogenic lineages. Upon transfer to serum-free culture, the long-term maintained mesenchymal-like cancer cells showed remarkable morphologic plasticity as they switched promptly into an epithelial-like phenotype with significant mammosphere formation capacity (P= 0.008).

CONCLUSION

Breast cancer cells can develop a pluripotent program with enhanced stemness activity that may together contribute to universal resistance to sex hormonal stimulation or deprivation. Isolation and characterization of patient-derived breast cancer stem cells in large clinical studies is therefore crucial to identify new targets for endocrine therapies, potentially directed towards stemness and pluripotency markers. Such direction may help overcoming endocrine resistance and draw attention to breast cancer stem cells' behaviour under endogenous and exogenous sex hormones throughout a woman's reproductive life.

EMT and Stemness in Tumor Dormancy and Outgrowth: Are They Intertwined Processes?

Metastases are the major cause of cancer patients' mortality and can occur years and even decades following apparently successful treatment of the primary tumor. Early dissemination of cancer cells, followed by a protracted period of dormancy at distant sites, has been recently recognized as the clinical explanation for this very-long latency. The mechanisms that govern tumor dormancy at distant sites and their reactivation to proliferating metastases are just beginning to be unraveled. Tumor cells, that survive the immune surveillance and hemodynamic forces along their journey in the circulation and successfully colonize and adopt to the new and "hostile" microenvironment and survive in a quiescent dormant state for years before emerging to proliferative state, must display high plasticity. Here we will discuss whether the plasticity of dormant tumor cells is required for their long-term survival and outgrowth. Specifically, we will focus on whether epithelial mesenchymal transition and acquisition of stem-like properties can dictate their quiescent and or their proliferative fate. Deeper understanding of these intertwining processes may facilitate in the future the development of novel therapies.

TiHo-0906: a new feline mammary cancer cell line with molecular, morphological, and immunocytological characteristics of epithelial to mesenchymal transition

Feline mammary carcinomas (FMCs) with anaplastic and malignant spindle cells histologically resemble the human metaplastic breast carcinoma (hMBC), spindle-cell subtype. hMBCs display epithelial-to-mesenchymal transition (EMT) characteristics. Herein we report the establishment and characterization of a cell line (TiHoCMglAdcar0906; TiHo-0906) exhibiting EMT-like properties derived from an FMC with anaplastic and malignant spindle cells. Copy-number variations (CNVs) by next-generation sequencing and immunohistochemical characteristics of the cell line and the tumour were compared. The absolute qPCR expression of EMT-related markers HMGA2 and CD44 was determined. The growth, migration, and sensitivity to doxorubicin were assessed. TiHo-0906 CNVs affect several genomic regions harbouring known EMT-, breast cancer-, and hMBCs-associated genes as AKT1, GATA3, CCND2, CDK4, ZEB1, KRAS, HMGA2, ESRP1, MTDH, YWHAZ, and MYC. Most of them were located in amplified regions of feline chromosomes (FCAs) B4 and F2. TiHo-0906 cells displayed an epithelial/mesenchymal phenotype, and high HMGA2 and CD44 expression. Growth and migration remained comparable during subculturing. Low-passaged cells were two-fold more resistant to doxorubicin than high-passaged cells (IC50: 99.97 nM, and 41.22 nM, respectively). The TiHo-0906 cell line was derived from a poorly differentiated cellular subpopulation of the tumour consistently displaying EMT traits. The cell line presents excellent opportunities for studying EMT on FMCs.

Novel Insights into Adult and Cancer Stem Cell Biology

Adult tissues are thought to harbor two populations of "dormant" and "actively dividing" stem cells. Quiescent stem cells undergo rare asymmetric cell divisions (ACDs) through which they self-renew and give rise to tissue-committed "progenitors" of distinct fate and "progenitors" in turn undergo symmetric cell divisions (SCDs) and clonal expansion. However, quiescent stem cells have not been demonstrated in adult tissues such as skin, testis, liver, and brain. After surgical removal of part of liver and pancreas-adult differentiated cells divide and regenerate and a possible role of stem cells remains doubtful. Long-term repopulating hematopoietic stem cells are quiescent in nature but ACD has not been convincingly demonstrated even among them. Attempts by various groups to identify a common stemness program that ensures self-renewal among different kinds of stem cells have also remained futile. Uncontrolled self-renewal and compromised differentiation of stem cells possibly initiate leukemia/cancer, but the identity of leukemic stem cells and whether cancer stem cells arise by epithelial-mesenchymal transition (EMT) in solid tumors are all open-ended questions that need greater clarity. Acceptance of the presence of very small embryonic-like stem cells (VSELs) in adult tissues could clarify several of these existing dilemmas in the field. Data are compiled showing that VSELs undergo ACD in the hematopoietic system, testis, ovary, uterus, and pancreas, whereas tissue-committed progenitors undergo SCD and clonal expansion. VSELs possess similar overlapping stemness program as in embryonic stem cells, embryonic carcinoma cells, embryonic germ cells, induced pluripotent stem cells, and primordial germ cells. VSELs and leukemic and cancer cells express overlapping embryonic markers. Uncontrolled proliferation of VSELs and compromised differentiation possibly initiate leukemia. Process of EMT and initiation of solid tumor from VSELs (located among the epithelial cells) are indeed two distinct and parallel events. To conclude, VSELs provide explanation to several confounding aspects of adult stem cell biology.

Inhibition of smoothened in breast cancer cells reduces CAXII expression and cell migration

Breast cancer (BC) relapse and metastasis are the leading cause of death and, together with drug resistance, keep mortality still high. The Hedgehog (Hh) pathway is expressed during embryogenesis, organogenesis and in adult tissue homeostasis and its aberrant activation is often associated with cancer. Carbonic anhydrase (CA) enzymes are important during development; they play a key role in controlling several cellular mechanisms, such as pH regulation, survival, and migration, and they are aberrantly expressed in cancer. The goal of this study was to investigate the interplay between the Hh pathway and CAXII in terms of BC cell migration. We here demonstrated that smoothened (SMO) silencing resulted in a reduction of CAXII expression at mRNA and protein level. This led to a decrease in cell migration, which was restored when cells were treated with an SMO agonist, Sag dihydrochloride (SAG), but not when cells were cotreated with SAG and the CAs inhibitor Acetazolamide. This suggested that the ability of SAG to promote cell migration was impaired when CAXII was inhibited. The reduction was also confirmed within hypoxic and inflammatory microenvironment, typical of BC, indicating a key role of the Hh pathway in controlling CAXII expression. Our results may contribute to further understand the physiology of BC cells and indicate that the Hh pathway controls BC cell migration and cell invasion also through CAXII, with important implications in identifying novel therapeutic targets.

Inflammatory cytokine profile of co‑cultivated primary cells from the endometrium of women with and without endometriosis

Endometriosis is a chronic gynecological disorder defined as the presence of endometrial tissue within extra-uterine sites. The primary symptoms are infertility and chronic pain. The inflammatory environment and aberrant immune responses in women with endometriosis may be directly associated with the initiation and progression of endometriotic lesions. In the present study, the secretion of inflammatory cytokines was evaluated in cultures of primary endometrial cells (ECs) isolated from the endometrium of women with and without endometriosis. The presence of endometriotic cells leads to alterations in the secretory profile of healthy ECs. The expression of the inflammatory cytokines interleukin (IL)‑6 and IL‑8 was significantly increased in endometriotic and co‑cultured cells compared with healthy ECs. IL‑6 expression was strongly correlated with IL‑8 expression in endometriotic cells. IL‑1β expression was increased on day 10 of co‑culture to 48.30 pg/ml and may be associated with the long‑term co‑culture, rather than IL‑6 and IL‑8 expression. IL‑6 expression was strongly correlated with cell number, whereas IL‑8 expression was moderately correlated with cell number. Additionally, it was observed that co‑cultured cells exhibited a different population of cells, with expression of the mesenchymal stem cell marker cell surface glycoprotein MUC18, indicating a putative role of endometrial mesenchymal stem cells in the secretion of cytokines and disease development. These results indicate a predominant role of primary endometriotic cells in the secretion of cytokines, which contributes to the disrupted peritoneal and endometrial environment observed in the women with endometriosis.

Breast cancer stem cells: Features, key drivers and treatment options

The current view is that breast cancer is a stem cell disease characterized by the existence of cancer cells with stem-like features and tumor-initiating potential. These cells are made responsible for tumor dissemination and metastasis. Common therapies by chemotherapeutic drugs fail to eradicate these cells and rather increase the pool of cancer stem cells in tumors, an effect that may increase the likelyhood of recurrence. Fifteen years after the first evidence for a small stem-like subpopulation playing a major role in breast cancer initiation has been published a large body of knowledge has been accumulated regarding the signaling cascades and proteins involved in maintaining stemness in breast cancer. Differences in the stem cell pool size and in mechanisms regulating stemness in the different breast cancer subtypes have emerged. Overall, this knowledge offers new approaches to intervene with breast cancer stem cell activity. New options are particularly needed for the treatment of triple-negative breast cancer subtype, which is particularly rich in cancer stem cells and is also the subtype for which specific therapies are still not available.

Telomerase reverse transcriptase coordinates with the epithelial-to-mesenchymal transition through a feedback loop to define properties of breast cancer stem cells

Telomerase and its core component, telomerase reverse transcriptase (hTERT), are critical for stem cell compartment integrity. Normal adult stem cells have the longest telomeres in a given tissue, a property mediated by high hTERT expression and high telomerase enzymatic activity. In contrast, cancer stem cells (CSCs) have short telomeres despite high expression of hTERT, indicating that the role of hTERT in CSCs is not limited to telomere elongation and/or maintenance. The function of hTERT in CSCs remains poorly understood. Here, we knocked down hTERT expression in CSCs and observed a morphological shift to a more epithelial phenotype, suggesting a role for hTERT in the epithelial-to-mesenchymal transition (EMT) of CSCs. Therefore, in this study, we systematically explored the relationship between hTERT and EMT and identified a reciprocal, bi-directional feedback loop between hTERT and EMT in CSCs. We found that hTERT expression is mutually exclusive to the mesenchymal phenotype and that, reciprocally, loss of the mesenchymal phenotype represses hTERT expression. We also showed that hTERT plays a critical role in the expression of key CSC markers and nuclear β-catenin localization, increases the percentage of cells with side-population properties, and upregulates the CD133 expression. hTERT also promotes chemoresistance properties, tumorsphere formation and other important functional CSC properties. Subsequently, hTERT knockdown leads to the loss of the above advantages, indicating a loss of CSC properties. Our findings suggest that targeting hTERT might improve CSCs elimination by transitioning them from the aggressive mesenchymal state to a more steady epithelial state, thereby preventing cancer progression.

Summary: This study describe a reciprocal, bi-directional feedback loop between hTERT and EMT to regulate properties of CSCs, suggesting that targeting hTERT may eliminate CSCs, thereby preventing cancer progression.

A mechanism-based computational model to capture the interconnections among epithelial-mesenchymal transition, cancer stem cells and Notch-Jagged signaling

Epithelial-mesenchymal transition (EMT) and cancer stem cell (CSCs) formation are two fundamental and well-studied processes contributing to cancer metastasis and tumor relapse. Cells can undergo a partial EMT to attain a hybrid epithelial/mesenchymal (E/M) phenotype or a complete EMT to attain a mesenchymal one. Similarly, cells can reversibly gain or lose 'stemness'. This plasticity in cell states is modulated by signaling pathways such as Notch. However, the interconnections among the cell states enabled by EMT, CSCs and Notch signaling remain elusive. Here, we devise a computational model to investigate the coupling among the core decision-making circuits for EMT, CSCs and Notch. Our model predicts that hybrid E/M cells are most likely to associate with stem-like traits and enhanced Notch-Jagged signaling – a pathway implicated in therapeutic resistance. Further, we show that the position of the 'stemness window' on the 'EMT axis' is varied by altering the coupling strength between EMT and CSC circuits, and/or modulating Notch signaling. Finally, we analyze the gene expression profile of CSCs from several cancer types and observe a heterogeneous distribution along the 'EMT axis', suggesting that different subsets of CSCs may exist with varying phenotypes along the epithelial-mesenchymal axis. We further investigate therapeutic perturbations such as treatment with metformin, a drug associated with decreased cancer incidence and increased lifespan of patients. Our mechanism-based model explains how metformin can both inhibit EMT and blunt the aggressive potential of CSCs simultaneously, by driving the cells out of a hybrid E/M stem-like state with enhanced Notch-Jagged signaling.

Hyaluronan, Cancer-Associated Fibroblasts and the Tumor Microenvironment in Malignant Progression

This review summarizes the roles of CAFs in forming a “cancerized” fibrotic stroma favorable to tumor initiation and dissemination, in particular highlighting the functions of the extracellular matrix component hyaluronan (HA) in these processes. The structural complexity of the tumor and its host microenvironment is now well appreciated to be an important contributing factor to malignant progression and resistance-to-therapy. There are multiple components of this complexity, which include an extensive remodeling of the extracellular matrix (ECM) and associated biomechanical changes in tumor stroma. Tumor stroma is often fibrotic and rich in fibrillar type I collagen and hyaluronan (HA). Cancer-associated fibroblasts (CAFs) are a major source of this fibrotic ECM. CAFs organize collagen fibrils and these biomechanical alterations provide highways for invading carcinoma cells either under the guidance of CAFs or following their epithelial to mesenchymal transition (EMT). The increased HA metabolism of a tumor microenvironment instructs carcinoma initiation and dissemination by performing multiple functions. The key effects of HA reviewed here are its role in activating CAFs in pre-malignant and malignant stroma, and facilitating invasion by promoting motility of both CAFs and tumor cells, thus facilitating their invasion. Circulating CAFs (cCAFs) also form heterotypic clusters with circulating tumor cells (CTC), which are considered to be pre-cursors of metastatic colonies. cCAFs are likely required for extravasation of tumors cells and to form a metastatic niche suitable for new tumor colony growth. Therapeutic interventions designed to target both HA and CAFs in order to limit tumor spread and increase response to current therapies are discussed.

PGE2 /EP4 antagonism enhances tumor chemosensitivity by inducing extracellular vesicle-mediated clearance of cancer stem cells

Cells expressing mesenchymal/basal phenotypes in tumors have been associated with stem cell properties. Cancer stem cells (CSCs) are often resistant to conventional chemotherapy. We explored overcoming mesenchymal CSC resistance to chemotherapeutic agents. Our goal was to reduce CSC numbers in vivo, in conjunction with chemotherapy, to reduce tumor burden. Analysis of clinical samples demonstrated that COX-2/PGE₂ /EP₄ signaling is elevated in basal-like and chemoresistant breast carcinoma and is correlated with survival and relapse of breast cancer. EP₄ antagonism elicts a striking shift of breast cancer cells from a mesenchymal/CSC state to a more epithelial non-CSC state. The transition was mediated by EP₄ antagonist-induced extracellular vesicles [(EVs)/exosomes] which removed CSC markers, mesenchymal markers, integrins, and drug efflux transporters from the CSCs. In addition, EP₄ antagonism-induced CSC EVs/exosomes can convert tumor epithelial/non-CSCs to mesenchymal/CSCs able to give rise to tumors and to promote tumor cell dissemination. Because of its ability to induce a CSC-to-non-CSC transition, EP₄ antagonist treatment in vivo reduced the numbers of CSCs within tumors and increased tumor chemosensitivity. EP₄ antagonist treatment enhances tumor response to chemotherapy by reducing the numbers of chemotherapy-resistant CSCs available to repopulate the tumor. EP₄ antagonism can collaborate with conventional chemotherapy to reduce tumor burden.

Aggressive Phenotype of Cells Disseminated via Hematogenous and Lymphatic Route in Breast Cancer Patients

Intratumoral heterogeneity of breast cancer remains a major challenge in successful treatment. Failure of cancer therapies can also be accredited to inability to systemically eradicate cancer stem cells (CSCs). Recent evidence points to the role of epithelial-mesenchymal transition (EMT) in expanding the pool of tumor cells with CSCs features. Thus, we assessed expression level as well as heterogeneity of CSCs markers in primary tumors (PT), lymph node metastasis (LNM), and circulating tumor cells (CTCs)-enriched blood fractions in order to correlate them with signs of EMT activation as well as clinicopathological data of breast cancer patients. Level of CSCs markers (ALDH1, CD44, CD133, OCT-4, NANOG) and EMT markers was quantified in PT (N=107), LNM (N=56), and CTCs-enriched blood fractions (N=85). Heterogeneity of CSCs markers expression within each PT and LNM was assessed by calculating Gini Index. Percentage of ALDH1-positive cells was elevated in PT in comparison to LNM (P = .005). However, heterogeneity of the four CSCs markers: ALDH1 (P = .019), CD133 (P = .009), OCT-4 (P = .027), and CD44 (P < .001) was decreased in LNM. Samples classified as mesenchymal (post-EMT) showed elevated expression of CSCs markers (OCT-4 and CD44 in PT; OCT-4 in LNM; ALDH1, OCT-4, NANOG, CD44 in CTCs). Patients with mesenchymal-like CTCs had worse prognosis than patients with epithelial-like or no CTCs (P = .0025). CSCs markers are enriched in PT, LNM, and CTCs with mesenchymal features, but their heterogeneity is decreased in metastatic lymph nodes. Mesenchymal CTCs phenotype correlates with poor prognosis of the patients.

GD2 expression in breast cancer

Breast cancer (BC) is a heterogeneous disease, including different subtypes having diverse incidence, drug-sensitivity and survival rates. In particular, claudin-low and basal-like BC have mesenchymal features with a dismal prognosis. Disialoganglioside GD2 is a typical neuroectodermal antigen expressed in a variety of cancers. Despite its potential relevance in cancer diagnostics and therapeutics, the presence and role of GD2 require further investigation, especially in BC. Therefore, we evaluated GD2 expression in a cohort of BC patients and its correlation with clinical-pathological features.

Sixty-three patients with BC who underwent surgery without prior chemo- and/or radiotherapy between 2001 and 2014 were considered. Cancer specimens were analyzed by immunohistochemistry and GD2-staining was expressed according to the percentage of positive cells and by a semi-quantitative scoring system.

Patient characteristics were heterogeneous by age at diagnosis, histotype, grading, tumor size, Ki-67 and receptor-status. GD2 staining revealed positive cancer cells in 59% of patients. Among them, 26 cases (41%) were labeled with score 1+ and 11 (18%) with score 2+. Notably, the majority of metaplastic carcinoma specimens stained positive for GD2. The univariate regression logistic analysis revealed a significant association of GD2 with triple-receptor negative phenotype and older age (> 78) at diagnosis.

We demonstrate for the first time that GD2 is highly prevalent in a cohort of BC patients clustering on very aggressive BC subtypes, such as triple-negative and metaplastic variants.

A Novel TGFβ Trap Blocks Chemotherapeutics-Induced TGFβ1 Signaling and Enhances Their Anticancer Activity in Gynecologic Cancers

Purpose: We investigated the mechanisms of how TGFβ pathway is activated by chemotherapeutics and whether a novel TGFβ trap called RER can block chemotherapeutics-induced TGFβ pathway activation and enhance their antitumor activity in gynecologic cancer.Patients and Methods: An unbiased bioinformatic analysis of differentially expressed genes in 31 ovarian cases due to chemotherapy was used to identify altered master regulators. Phosphorylated Smad2 was determined in 30 paired cervical cancer using IHC. Furthermore, the effects of chemotherapeutics on TGFβ signaling and function, and the effects of RER on chemotherapy-induced TGFβ signaling were determined in gynecologic cancer cells.Results: Chemotherapy-induced transcriptome alteration in ovarian cancer was significantly associated with TGFβ signaling activation. Chemotherapy was found to activate TGFβ signaling as indicated by phosphorylated Smad2 in paired cervical tumor samples (pre- and post-chemotherapy). Similar to TGFβ1, chemotherapeutics were found to stimulate Smad2/3 phosphorylation, cell migration, and markers related to epithelial-mesenchymal transition (EMT) and cancer stem cells (CSC). These TGFβ-like effects were due to the stimulation of TGFβ1 expression and secretion, and could all be abrogated by TGFβ inhibitors including a novel TGFβ trap protein called RER both in vitro and in vivo Importantly, combination treatment with RER and cisplatin showed a higher tumor inhibitory activity than either agent alone in a xenograft model of ovarian cancer.Conclusions: Chemotherapeutics can stimulate TGFβ1 production and consequently enhance TGFβ signaling, EMT, and CSC features resulting in reduced chemo-sensitivity. Combination therapy with a TGFβ inhibitor should alleviate this unintended side effect of chemotherapeutics and enhance their therapeutic efficacy. Clin Cancer Res; 24(12); 2780-93. ©2018 AACR.

BRCA1 haploinsufficiency cell-autonomously activates RANKL expression and generates denosumab-responsive breast cancer-initiating cells

Denosumab, a monoclonal antibody to the receptor activator of nuclear factor-κB ligand (RANKL), might be a novel preventative therapy for BRCA1-mutation carriers at high risk of developing breast cancer. Beyond its well-recognized bone-targeted activity impeding osteoclastogenesis, denosumab has been proposed to interfere with the cross-talk between RANKL-producing sensor cells and cancer-initiating RANK+ responder cells that reside within premalignant tissues of BRCA1-mutation carriers. We herein tested the alternative but not mutually exclusive hypothesis that BRCA1 deficiency might cell-autonomously activate RANKL expression to generate cellular states with cancer stem cell (CSC)-like properties. Using isogenic pairs of normal-like human breast epithelial cells in which the inactivation of a single BRCA1 allele results in genomic instability, we assessed the impact of BRCA1 haploinsufficiency on the expression status of RANK and RANKL. RANK expression remained unaltered but RANKL was dramatically up-regulated in BRCA1mut/+ haploinsufficient cells relative to isogenic BRCA1+/+ parental cells. Neutralizing RANKL with denosumab significantly abrogated the ability of BRCA1 haploinsufficient cells to survive and proliferate as floating microtumors or "mammospheres" under non-adherent/non-differentiating conditions, an accepted surrogate of the relative proportion and survival of CSCs. Intriguingly, CSC-like states driven by epithelial-to-mesenchymal transition or HER2 overexpression traits responded to some extent to denosumab. We propose that breast epithelium-specific mono-allelic inactivation of BRCA1 might suffice to cell-autonomously generate RANKL-addicted, denosumab-responsive CSC-like states. The convergent addiction to a hyperactive RANKL/RANK axis of CSC-like states from genetically diverse breast cancer subtypes might inaugurate a new era of cancer prevention and treatment based on denosumab as a CSC-targeted agent.

TRIM28 multi-domain protein regulates cancer stem cell population in breast tumor development

The expression of Tripartite motif-containing protein 28 (TRIM28)/Krüppel-associated box (KRAB)-associated protein 1 (KAP1), is elevated in at least 14 tumor types, including solid and hematopoietic tumors. High level of TRIM28 is associated with triple-negative subtype of breast cancer (TNBC), which shows higher aggressiveness and lower survival rates. Interestingly, TRIM28 is essential for maintaining the pluripotent phenotype in embryonic stem cells. Following on that finding, we evaluated the role of TRIM28 protein in the regulation of breast cancer stem cells (CSC) populations and tumorigenesis in vitro and in vivo. Downregulation of TRIM28 expression in xenografts led to deceased expression of pluripotency and mesenchymal markers, as well as inhibition of signaling pathways involved in the complex mechanism of CSC maintenance. Moreover, TRIM28 depletion reduced the ability of cancer cells to induce tumor growth when subcutaneously injected in limiting dilutions. Our data demonstrate that the downregulation of TRIM28 gene expression reduced the ability of CSCs to self-renew that resulted in significant reduction of tumor growth. Loss of function of TRIM28 leads to dysregulation of cell cycle, cellular response to stress, cancer cell metabolism, and inhibition of oxidative phosphorylation. All these mechanisms directly regulate maintenance of CSC population. Our original results revealed the role of the TRIM28 in regulating the CSC population in breast cancer. These findings may pave the way to novel and more effective therapies targeting cancer stem cells in breast tumors.

Dormant tumor cells expressing LOXL2 acquire a stem-like phenotype mediating their transition to proliferative growth

Recurrence of breast cancer disease years after treatment appears to arise from disseminated dormant tumor cells (DTC). The mechanisms underlying the outgrowth of DTC remain largely unknown. Here we demonstrate that dormant MCF-7 cells expressing LOXL2 acquire a cancer stem cell (CSC)-like phenotype, mediating their outgrowth in the 3D BME system that models tumor dormancy and outgrowth. Similarly, MCF-7-LOXL2 cells colonizing the lung transitioned from dormancy to metastatic outgrowth whereas MCF-7 cells remained dormant. Notably, epithelial to mesenchymal transition (EMT) of MCF-7-LOXL2 cells was required for their CSC-like properties and their transition to metastatic outgrowth. These findings were further supported by clinical data demonstrating that increase in LOXL2 mRNA levels correlates with increase in the mRNA levels of EMT and stem cells markers, and is also associated with decrease in relapse free survival of breast cancer patients. Notably, conditional hypoxia induced expression of endogenous LOXL2 in MCF-7 cells promoted EMT and the acquisition of a CSC-like phenotype, while knockdown of LOXL2 inhibited this transition. Overall, our results demonstrate that expression of LOXL2 endowed DTC with CSC-like phenotype driving their transition to metastatic outgrowth and this stem-like phenotype is dependent on EMT that can be driven by the tumor microenvironment.

Multifaceted Roles of Interleukin-6 in Adipocyte-Breast Cancer Cell Interaction

Breast cancer is the most common malignancy in women worldwide, with a developmental process spanning decades. The malignant cells recruit a variety of cells including fibroblasts, endothelial cells, immune cells, and adipocytes, creating the tumor microenvironment. The tumor microenvironment has emerged as active participants in breast cancer progression and response to treatment through autocrine and paracrine interaction with the malignant cells. Adipose tissue is abundant in the breast cancer microenvironment; interactions with cancer cells create cancer-associated adipocytes which produce a variety of adipokines that influence breast cancer initiation, metastasis, angiogenesis, and cachexia. Interleukin (IL)-6 has emerged as key compound significantly produced by breast cancer cells and adipocytes, with the potential of inducing proliferation, epithelial-mesenchymal phenotype, stem cell phenotype, angiogenesis, cachexia, and therapeutic resistance in breast cancer cells. Our aim is to present a brief knowledge of IL-6’s role in breast cancer. This review summarizes our current understanding of the breast microenvironment, with emphasis on adipocytes as key players in breast cancer tumorigenesis. The effects of key adipocytes such as leptin, adipokines, TGF-b, and IL-6 are discussed. Finally, we discuss the role of IL-6 in various aspects of cancer progression.