Ability Of Breast Cancer Cells Research Articles

Chemokine (C-X-C motif) receptor 4 RNA interference inhibits bone metastasis in breast cancer.

Chemokine (C-X-C motif) receptor 4 (CXCR4) has been found to closely correlate with the incidence, development, treatment and prognosis of breast cancer. The aim of the present study was to investigate the effects of CXCR4 on bone metastasis in breast cancer and to explore the mechanisms of this process. CXCR4 small interfering RNA was transfected into the breast cancer cell line, MDA-MB-231BA-rfp, and the cell proliferation and invasion abilities of the cells were measured using cell counting kit-8 cell proliferation and Transwell assays. A mouse model of breast cancer with bone metastasis was prepared and the bone metastasis was confirmed using micro-positron emission tomography. The associated proteins were detected by western blot analysis and the results showed that CXCR4 RNAi inhibited the cell proliferation and invasion ability of the MDA-MB-231BA-rfp cells. In addition, CXCR4 RNAi inhibited the duration and extent of bone metastasis in the MDA-MB-231BA-rfp cells in the mouse model, while the inhibition of CXCR4 RNAi blocked the phosphatidylinositide 3-kinase (PI3K)/protein kinase B (AKT)/matrix metalloproteinase (MMP)-9 pathway. In conclusion, the present study demonstrated that CXCR4 RNAi inhibits bone metastasis and the cell proliferation and invasion abilities of breast cancer cells. Furthermore, the CXCR4/PI3K/AKT/MMP-9 pathway may be important in the bone metastasis of breast cancer.

Effect of curcumin in inducing apoptosis of MDA-MB-213 cells by activating endoplasmic reticulum stress

To explore the possible mechanism of curcumin in inducing the apoptosis of breast cancer cell MDA-MB-231. Curcumin of different concentrations at 0, 10 25, 50, 100, 150, 200 micromol x L(-1) were used to intervene breast cancer cells MDA-MB-231 for 24 hours. MTT was used to observe its effect on the proliferation of breast cancer cells. The flow cytometry was used to detect its effect on the cell apoptosis. The real-time quantitative PCR and Western blot was used to assess the expression levels of GRP78 and CHOP in breast cancer cells. Curcumin could inhibit the proliferative ability of breast cancer cells by inducing them in a concentration-dependent manner. Curcumin could significantly increase the expression levels of GRP78 and CHOP in breast cancer cells. Curcumin could induce the apoptosis of breast cancer cells MDA-MB-231 by activating endoplasmic reticulum stress.

Experimental study on inhibitory effect of wogonin on proliferation and invasion of breast cancer cells

To study the inhibitory effect of wogonin on the growth and proliferation of breast cancer cells MDA-MB-23, and observe its effect on the adhesion, migration and invasion of MDA-MB-23 cells, in order to further study its molecular mechanism. MTT assay was used to detect the effect of wogonin on MDA-MB-23 cell growth. Ki-67 assay was adopted to test the effect of wogonin on cell proliferation. Scratch test, adherence test and invasion chamber assay were taken to detect the effect on the migration and invasion abilities of MDA-MB-231 cells. Proliferation and metastasis-related proteins and relevant signaling pathways were detected by Western blotting. Wogonin could remarkably inhibit the growth and proliferation of MDA-MB-231 cells, significantly inhibit migration, adhesion and invasion abilities of breast cancer cells at a low concentration, and effectively inhibit the expression of Survivin, Bcl-2, ICAM-1, MMP-2, MMP-9 proteins of MDA-MB-231 cells. Wogonin could notably inhibit growth and proliferation of breast cancer cells, and inhibit migration, adhesion and invasion of MDA-MB-231 cells. Its invasive and adhesive effects on MDA-MB-231 cells may be related to the decrease in ICAM-1, MMP-2, MMP-9 expressions.

Dickkopf-1 is regulated by the mevalonate pathway in breast cancer

IntroductionAmino-bisphosphonates and statins inhibit the mevalonate pathway, and may exert anti-tumor effects. The Wnt inhibitor dickkopf-1 (DKK-1) promotes osteolytic bone lesions by inhibiting osteoblast functions and has been implicated as an adverse marker in multiple cancers. We assessed the effects of mevalonate pathway inhibition on DKK-1 expression in osteotropic breast cancer.MethodsRegulation of DKK-1 by bisphosphonates and statins was assessed in human breast cancer cell lines, and the role of the mevalonate pathway and downstream targets was analyzed. Moreover, the potential of breast cancer cells to modulate osteoblastogenesis via DKK-1 was studied in mC2C12 cells. Clinical relevance was validated by analyzing DKK-1 expression in the tissue and serum of women with breast cancer exposed to bisphosphonates.ResultsDKK-1 was highly expressed in receptor-negative breast cancer cell lines. Patients with receptor-negative tumors displayed elevated levels of DKK-1 at the tissue and serum level compared to healthy controls. Zoledronic acid and atorvastatin potently suppressed DKK-1 in vitro by inhibiting geranylgeranylation of CDC42 and Rho. Regulation of DKK-1 was strongest in osteolytic breast cancer cell lines with abundant DKK-1 expression. Suppression of DKK-1 inhibited the ability of breast cancer cells to block WNT3A-induced production of alkaline phosphates and bone-protective osteoprotegerin in preosteoblastic C2C12 cells. In line with the in vitro data, treatment of breast cancer patients with zoledronic acid decreased DKK-1 levels by a mean of 60% after 12 months of treatment.ConclusionDKK-1 is a novel target of the mevalonate pathway that is suppressed by zoledronic acid and atorvastatin in breast cancer.

Critical role of miR-10b in transforming growth factor-β1-induced epithelial–mesenchymal transition in breast cancer

Epithelial-mesenchymal transition (EMT) is a key process in the tumor metastatic cascade that is characterized by the loss of cell-cell junctions and cell polarity, resulting in the acquisition of migratory and invasive properties. Recent evidence showed that altered microRNA-10b (miR-10b) expression was implicated in the occurrence of EMT of breast cancer. However, the exact role and underlying mechanisms of miR-10b in the EMT of breast cancer still remain unknown. In this study, miR-10b was found to be upregulated in breast cancer tissues and breast cancer cell lines and the expression of miR-10b was shown to be closely correlated with aggressiveness in breast cancer. Treating breast cancer cells with the miR-10b inhibitor increased E-cadherin expression while decreasing vimentin expression. At the same time, on inhibition of miR-10b, the invasion and proliferation ability of breast cancer cells also decreased. Transforming growth factor-β (TGF-β) is a multifunctional cytokine that induces EMT in multiple cell types. Here, we identified miR-10b as a target gene of TGF-β1. The expression of miR-10b increased during TGF-β1-induced EMT of breast cancer cells. Further study showed that inhibition of miR-10b expression partially reversed the EMT, invasion and proliferation induced by TGF-β1 in breast cancer cells. Taken together, these results demonstrated a novel function for miR-10b in TGF-β1-induced EMT in breast cancer and increased their metastatic potential. MiR-10b might become a possible target for gene therapy in breast cancer.

Modulation of BAG-1 Expression Alters the Sensitivity of Breast Cancer Cells to Tamoxifen

Background: BAG-1 (bcl-2 associated athanogene) is a multifunctional protein that protects cells from a wide range of apoptotic stimuli including radiation, hypoxia and chemotherapeutic agents. Overexpression of cytoplasmic BAG-1 has been associated with the increased survival and decreased response to treatment with tamoxifen (TAM) in breast cancer. We attempted to assess the expression of BAG-1 in the human breast cancer cells that are resistant to treatment with 4-OH TAM and effect of altered BAG-1 expression on their sensitivity to 4-OH TAM. Methods: BAG-1 expression was examined in the MCF-7 cells that became resistant to 4-OH TAM. The 4-OH TAM-resistant MCF-7 cells were then transfected with the BAG-1 siRNA and the 4-OH TAM-sensitive MCF-7 cells with the plasmids carrying the human BAG-1 isoform-specific expression constructs respectively to investigate the effect of BAG-1 on the TAM-induced apoptosis. Results: Our results showed that the TAM-resistant MCF-7 (TAMR/MCF-7) cells expressed higher level of BAG-1 than that of the MCF-7 cells. Down-regulation of BAG-1 significantly enhanced the sensitivity of the TAMR/MCF-7 cells to TAM treatment. Additionally, we found that BAG-1 p50 was the only isoform that inhibited the TAM-induced apoptosis in the MCF-7 cells, while the other isoforms had little effect. Conclusion: Our study indicated that up and down regulations of the BAG-1 expression were associated with the decreased and increased sensitivity to 4-OH TAM in the estrogen receptor-positive (ER+) human breast cancer cell line MCF-7 respectively, and distinct isoforms of BAG-1 had different anti-apoptotic ability in breast cancer cells treated with the 4-OH TAM.

Abstract P2-09-07: Inhibition of aurora-A by MLN8237 decreases SMAD5 expression and increases effectiveness of chemotherapeutic agents in breast cancer cells

Abstract BACKGROUND: Breast cancer affects thousands of women each year. Epithelial to Mesenchymal transition (EMT) has been associated with increased metastatic potential of cancer cells as well as resistance to chemotherapy. Predicatively, presence of EMT leads to worse prognosis in patients with breast cancer. We have recently showed that Aurora-A plays a key role in development of EMT and increased ability of breast cancer cells for self renewal. Therefore we hypothesized that inhibition of Aurora-A in breast cancer cells will lead to increased sensitivity to chemotherapy. RESULTS: Increased Aurora-A expression, as assessed by IHC staining, in patients with locally advanced disease was associated with worse prognosis. We show that in ER+ cell line, MCF7, activating MAPK pathway through overexpression of Raf1 leads to increase in Aurora-A activity. These cells have decreased sensitivity to treatment with paclitaxel when compared to untransfected cells in MTT assays. This effect is even more exacerbated with over-expression of Aurora-A. The sensitivity to paclitaxel was restored with inhibition of Aurora-A by specific inhibitor, Alisertib. This was further explored in triple negative (MDA-MB-231) or Her-2/neu expressing (SUM149) cell lines. These cells express higher levels of Aurora-A. Inhibition of Aurora-A activity in combination with paclitaxel was superior when compared to either therapy alone. Similar effect was seen with use of anthracyclines. Inhibition of Aurora-A resulted in decreased SMAD5 expression as well as decreased Akt phosphorylation. Current studies are looking at a role of Aurora-A in activating SMAD5 and its role in resistance to chemotherapy. In vivo experiments evaluating combination therapies in breast cancer animal model are ongoing. CONCLUSIONS: Inhibition of Aurora-A by a specific inhibitor, MLN8237, resulted in decreased SMAD5 expression and increased effectiveness of chemotherapeutic agents in breast cancer cells. These results contribute to better understanding of signaling pathways involved in resistance of breast cancer cells to chemotherapy. This knowledge could be very useful in developing more effective treatments for breast cancer patients in neo-adjuvant, adjuvant and metastatic settings. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P2-09-07.

Infrequent Loss of Luminal Differentiation in Ductal Breast Cancer Metastasis

Lymph node involvement is a major prognostic variable in breast cancer. Whether the molecular mechanisms that drive breast cancer cells to colonize lymph nodes are shared with their capacity to form distant metastases is yet to be established. In a transcriptomic survey aimed at identifying molecular factors associated with lymph node involvement of ductal breast cancer, we found that luminal differentiation, assessed by the expression of estrogen receptor (ER) and/or progesterone receptor (PR) and GATA3, was only infrequently lost in node-positive primary tumors and in matched lymph node metastases. The transcription factor GATA3 critically determines luminal lineage specification of mammary epithelium and is widely considered a tumor and metastasis suppressor in breast cancer. Strong expression of GATA3 and ER in a majority of primary node-positive ductal breast cancer was corroborated by quantitative RT-PCR and immunohistochemistry in the initial sample set, and by immunohistochemistry in an additional set from 167 patients diagnosed of node-negative and –positive primary infiltrating ductal breast cancer, including 102 samples from loco-regional lymph node metastases matched to their primary tumors, as well as 37 distant metastases. These observations suggest that loss of luminal differentiation is not a major factor driving the ability of breast cancer cells to colonize regional lymph nodes.

Hypoxia-Induced Secretion of TGF-β1 in Mesenchymal Stem Cell Promotes Breast Cancer Cell Progression

In solid tumors, a decreased oxygen and nutrient supply creates a hypoxic microenvironment in the central region. This hypoxic condition induces molecular responses of normal and cancer cells in the local area, including angiogenesis, metabolic changes, and metastasis. In addition, other cells including mesenchymal stem cells (MSCs) have been reported to be recruited into the hypoxic area of solid tumors. In our previous study, we found that hypoxic condition induces the secretion of growth factors and cytokines in MSCs, and here we demonstrate that elevated secretion of transforming growth factor-β1 (TGF-β1) by MSCs under hypoxia promotes the growth, motility, and invasive ability of breast cancer cells. It was found that TGF-β1 promoter activity was regulated by hypoxia, and the major hypoxia-regulated element was located between bp -1030 to -666 in front of the TGF-β1 promoter region. In ChIP assay, the results revealed that HIF-1 was bound to the hypoxia response element (HRE) of TGF-β1 promoter. Collectively, the results indicate that hypoxia microenvironment can enhance cancer cell growth through the paracrine effects of the MSCs by driving their TGF-β1 gene expression and secretion. Therefore, extra caution has to be exercised when considering hypoxia pretreatment of MSCs before cell transplantation into patients for therapeutic purposes, particularly in patients susceptible to tumor growth.

Cytokines in osteoblast-conditioned medium promote the migration of breast cancer cells

Bone is one of the most common metastatic sites for breast cancer. In this study, we observed a promoting effect of osteoblast-conditioned medium (OCM) on the migration of MCF-7, a noninvasive cell line of breast cancer cells. Cytokine antibody array was used to compare the cytokines of OCM with the conditioned medium of non-differentiated osteoblast cells, which consequently revealed factors related to migration, such as IL8, IL6, CSF2 (G-CSF), CSF3 (GM-CSF), and TNFRSF11B (osteoprotegerin). The expression of genes related to migration was also estimated with a PCR array, which showed that 9 genes were upregulated and 26 genes downregulated. Moreover, activated p38, ERK, and AKT pathways were found in the OCM treatment group. This finding indicated the migration ability of breast cancer cells, which move toward the bone depending on the presence of specific cytokines in its surrounding microenvironment.

Mesenchymal Stem Cells Develop Tumor Tropism but Do Not Accelerate Breast Cancer Tumorigenesis in a Somatic Mouse Breast Cancer Model

The role of mesenchymal stem cells (MSCs) on breast cancer progression, growth and tumorigenesis remains controversial or unknown. In the present study, we investigated the role of MSCs on breast tumor induction and growth in a clinically relevant somatic breast cancer model. We first conducted in vitro studies and found that conditioned media (CM) of RCAS-Neu and RCAS-PyMT breast cancer cell lines and tumor cells themselves dramatically increased the proliferation and motility of MSCs and induced morphological changes of MSCs and differentiation into fibroblast-like cells. In contrast, the CM of MSCs inhibited the proliferation of two breast cancer cell lines by arresting the cell cycle at the G0/G1 phase. In vivo studies revealed that fluorescence dye-labeled MSCs migrated into tumor tissues. Unexpectedly, single or multiple intravenous injections of MSCs did not affect the latency of breast cancer in TVA- transgenic mice induced by intraductal injection of the RCAS vector encoding polyoma middle-T antigen (PyMT) or Neu oncogenes. Moreover, MSCs had no effect on RCAS-Neu tumor growth in a syngeneic ectopic breast cancer model. While our studies consistently demonstrated the ability of breast cancer cells to profoundly induce MSCs migration, differentiation, and proliferation, the anti-proliferative effect of MSCs on breast tumor cells observed in vitro could not be translated into an antitumor activity in vivo, probably reflecting the antagonizing or complex effects of MSCs on tumor environment and tumor cells themselves.

Cigarette smoke induces epithelial to mesenchymal transition and increases the metastatic ability of breast cancer cells

BackgroundRecent epidemiological studies demonstrate that both active and involuntary exposure to tobacco smoke increase the risk of breast cancer. Little is known, however, about the molecular mechanisms by which continuous, long term exposure to tobacco smoke contributes to breast carcinogenesis because most previous studies have focused on short term treatment models. In this work we have set out to investigate the progressive transforming effects of tobacco smoke on non-tumorigenic mammary epithelial cells and breast cancer cells using in vitro and in vivo models of chronic cigarette smoke exposure.ResultsWe show that both non-tumorigenic (MCF 10A, MCF-12A) and tumorigenic (MCF7) breast epithelial cells exposed to cigarette smoke acquire mesenchymal properties such as fibroblastoid morphology, increased anchorage-independent growth, and increased motility and invasiveness. Moreover, transplantation experiments in mice demonstrate that treatment with cigarette smoke extract renders MCF 10A cells more capable to survive and colonize the mammary ducts and MCF7 cells more prone to metastasize from a subcutaneous injection site, independent of cigarette smoke effects on the host and stromal environment. The extent of transformation and the resulting phenotype thus appear to be associated with the differentiation state of the cells at the time of exposure. Analysis by flow cytometry showed that treatment with CSE leads to the emergence of a CD44hi/CD24low population in MCF 10A cells and of CD44+ and CD49f + MCF7 cells, indicating that cigarette smoke causes the emergence of cell populations bearing markers of self-renewing stem-like cells. The phenotypical alterations induced by cigarette smoke are accompanied by numerous changes in gene expression that are associated with epithelial to mesenchymal transition and tumorigenesis.ConclusionsOur results indicate that exposure to cigarette smoke leads to a more aggressive and transformed phenotype in human mammary epithelial cells and that the differentiation state of the cell at the time of exposure may be an important determinant in the phenotype of the final transformed state.

SMAD5 expression and inhibition of the mitotic kinase aurora-A on sensitivity of breast cancer cells to chemotherapy.

e13516 Background: Breast cancer affects thousands of women each year. Epithelial to Mesenchymal transition (EMT) has been associated with increased metastatic potential of cancer cells as well as resistance to chemotherapy. Predicatively, presence of EMT leads to worse prognosis. We have recently showed that Aurora-A plays a key role in development of EMT and increased ability of breast cancer cells for self renewal. Therefore we hypothesized that inhibition of Aurora-A will lead to increased sensitivity to chemotherapy. Methods: The hypothesis was tested in vitro. Cellular proliferation was tested using MTT assay and protein levels were determined on Western blots. Results: In ER+ cell line, MCF7, constitutive activation of Raf-1/MAPK signaling pathway leads to aberrant activation of Aurora-A kinase activity. These cells have decreased sensitivity to treatment with paclitaxel when compared to parental MCF7 cells. This effect is even more pronounced with over-expression of Aurora-A. The sensitivity to paclitaxel was restored with inhibition of Aurora-A by novel inhibitor, Alisertib. This was further explored in triple negative cells (MDA-MB-231) and cells expressing Her-2/neu (BT474) which express higher levels of Aurora-A. Combination of Alisertib and paclitaxel was superior when compared to either therapy alone. Similar effect was seen with use of anthracyclines. Inhibition of Aurora-A resulted in decreased SMAD5 expression as well as decreased Akt phosphorylation. Current studies are investigating a role of Aurora-A in developing chemoresistance through activating SMAD5. In vivo experiments evaluating combination therapies in breast cancer animal model are ongoing. Conclusions: Inhibition of Aurora-A by Alisertib resulted in decreased SMAD5 nuclear phosphorylation and increased effectiveness of chemotherapeutic agents in breast cancer cells. These results contribute to better understanding of signaling pathways involved in resistance of breast cancer cells to chemotherapy. This knowledge could be extremely useful in developing more effective treatments for breast cancer patients both in neo-adjuvant, adjuvant and metastatic settings.

Abstract 1678: Metastatic breast cancer cell phenotype is regulated by autophagy.

Abstract Autophagy is a catabolic process that is tightly regulated during normal cell growth, development, and homeostasis. Although it may be death inducing, it is also an important survival mechanism for cells in stressful environments, including hypoxia, nutrient deprivation, chemical or physical pressure, or detachment from colonies. Considering the stress associated with the process of metastasis, we hypothesized that autophagy may play a role in the ability of breast cancer cells to survive and metastasize. To test this, we first compared cell proliferation after autophagic induction between metastatic breast cancer cell lines (MDA-MB-231 and -435), a non-metastatic breast cancer cell line (MDA-MB-436), and a ‘normal’ breast epithelial cell line (MCF10A). Both metastatic cell lines continued to proliferate following induction of autophagy; however, the non-metastatic and normal cell lines were growth-inhibited. Autophagy was also more rapidly induced by rapamycin in the metastatic cell lines as demonstrated by an increase in LC3II expression. To test the different survival capabilities between metastatic and normal cells, we selected cells through five rounds of starvation with Earle's balanced salt solution (EBSS) and compared their ability to induce autophagy. Although both the normal and metastatic cells maintained their ability to proliferate under normal conditions, the MDA-MB-231 cells that survived starvation (231-EB5) proliferated more rapidly than the parental population following induction of autophagy. In contrast, both MCF10A and MCF10A-EB5 cells were growth-inhibited. The 231-EB5 cells induced autophagy more rapidly than the parental population as demonstrated by increased expression of LC3II (analyzed by immunoblot) and increased LC3 puncta (analyzed by immunofluorescence). Migration of parental 231 cells was inhibited by rapamycin; however, there was no change in the ability of 231-EB5 cells to migrate after treatment with rapamycin. Growth in three dimensions also was significantly altered. MCF10A-EB5 cells were more extended compared to the spherical growth of the parental MCF10A cells. Protrusions emitted from the 231-EB5 cells were more rounded compared to the extended spikes of the parental 231 cells. Altogether, these results demonstrate that select populations derived from metastatic breast cancer cells have different abilities to survive, proliferate, and migrate following induction of autophagy, suggesting that autophagy may be a key mechanism for tumor progression and metastasis. Citation Format: Yi Li, Monica J. Lewis, Jianzhong Liu, James J. Cody, Douglas R. Hurst. Metastatic breast cancer cell phenotype is regulated by autophagy. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1678. doi:10.1158/1538-7445.AM2013-1678

Abstract 230: Connectivity-map analyses identify FDA-approved drugs targeting breast cancer stem cells.

Abstract Recently developed genomics-based tools are allowing repositioning of established drugs as cancer treatments. This approach has not been employed extensively to identify drugs that may target cancer stem cells (CSCs) of solid tumors. CD44+/CD24- cancer cells are the first described CSCs for breast cancer, which are enriched in mesenchymal stem-like (MSL) and mesenchymal-like (ML) subtypes of triple negative (TNBCs) and in anti-estrogen resistant breast cancers. We subjected gene expression array datasets containing list of genes differentially expressed in CD44+/CD24- CSCs compared to non-CSCs as well as in cells enriched for other markers of CSCs including CD271 and GD3S (six datasets in total) to connectivity map (CMAP) to identify drugs that may reverse gene expression patterns unique to CSCs. All trans retinoic acid (ATRA) was negatively connected with gene expression in CD44+/CD24-, CD271+, and GD3S+ CSCs as well as in ML and MSL subtypes of TNBCs. Independently, ATRA was found to modulate the expression of several genes in the recently described CSC-enriched Yes-Associated Protein (YAP) signature. ATRA-inducible genes of the YAP signature were associated with good prognosis, whereas ATRA-repressible genes were associated with poor prognosis, depending on the subtype of breast cancer. ATRA reduced mammosphere forming ability of breast cancer cells including acquired anti-estrogen resistant cells, which correlated with ATRA-mediated reduction of the critical stemness-associated gene SOX2 and induction of SOX21, which functions as a differentiation factor depending on the cell type. CD44+/CD24- breast cancer cell line with K-ras mutation was resistant to ATRA, which was reversed by MAP kinase inhibitors. From these results, we propose ATRA as a potential therapy for specific subtypes of breast cancers enriched for CSCs. A biomarker-driven patient selection may help to identify patients who may benefit from ATRA therapy. Citation Format: Poornima Bhat-Nakshatri, Chirayu Goswami, Sunil Badve, George W. Sledge, Harikrishna Nakshatri. Connectivity-map analyses identify FDA-approved drugs targeting breast cancer stem cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 230. doi:10.1158/1538-7445.AM2013-230

Hypoxia Regulation of Phosphokinases and the Prognostic Value of pAKT in Breast Cancer

Tumor hypoxia results in poor treatment response and is an indicator of poor outcome in cancer patients. TRIB3 is a hypoxia-upregulated protein involved in the ability of breast cancer cells to survive in hypoxic conditions. It is also involved in the prognosis of cancer patients, possibly by affecting several kinase-signaling pathways. We set out to establish which kinase-signaling pathways are regulated by hypoxia and whether these kinases are relevant for breast cancer prognosis. Using a phosphokinase antibody array comparing cells cultured under hypoxic conditions with those cultured during normoxia, we found that the phosphorylation status of ERK1/2, AKT, p70 S6 kinase, Lck and STAT3 was altered in both MCF7 and MDA-MB-231 breast cancer cells. Using Western blotting, we found that phosphorylated AKT (pAKT) increased in hypoxic conditions. Knockdown of TRIB3 attenuated this effect of hypoxia on AKT activation. Both pAKT and TRIB3 were expressed in pimonidazole-positive, hypoxic areas of human breast cancer tumors. In breast cancer patients significantly lower 5-year disease-free survival was observed for the pAKT-positive compared to the pAKT-negative group (64.6% vs 86.1%, p=0.03). In conclusion, the phosphorylation status of AKT is increased in hypoxic conditions and TRIB3 knockdown attenuates this response. Furthermore, pAKT expression denotes a worse prognosis in breast cancer patients. The hypoxia-related activation of AKT could explain the resistance to various treatments including chemotherapy and radiotherapy.

Suppression of endoplasmic reticulum stress-induced invasion and migration of breast cancer cells through the downregulation of heparanase

Tumor metastasis is the ultimate stage of cancer, and the primary cause of mortality in patients. Tumor cells breaking through the natural barrier consisting of the basement membrane (BM) and extracellular matrix (ECM) is the a crucial step in tumor invasion and metastasis. Thus, protecting this barrier is the key to reducing mortality. Heparanase is a mammalian endo-β-glucuronidase which has been found to promote the cleavage of heparan sulfate (HS), and plays a significant role in tumor cell invasion and metastasis. Although chemotherapeutic reagents have a strong antitumor activity, they may promote the invasion and migration of cancer cells, as has been observed during clinical treatment. Chemotherapeutic reagents can induce endoplasmic reticulum (ER) stress; in this study, we used adriamycin (ADM) and a classical ER stress inducer, tunicamycin (TM). We report that the activation of ER stress is involved in the enhanced invasion and migration ability of breast cancer cells and we hypothesized that this effect is associated with the activation of heparanase. In support of this, we used the heparanase inhibitor, OGT2115, and low molecular weight heparin (LMWH) to inhibit the expression and activity of heparanase, and we found that the invasion and migration ability of the cells was suppressed. Our findings demonstrate that heparanase inhibitors suppress breast cancer cell invasion and migration induced by ER stress, and provide a strong rationale for the development of heparanase-based therapeutics for the prevention of metastasis induced by chemotherapeutic reagents.

The Exposure of Breast Cancer Cells to Fulvestrant and Tamoxifen Modulates Cell Migration Differently

There is no doubt that there are increased benefits of hormonal therapy to breast cancer patients; however, current evidence suggests that estrogen receptor (ER) blockage using antiestrogens is associated with a small induction of invasiveness in vitro. The mechanism by which epithelial tumor cells escape from the primary tumor and colonize to a distant site is not entirely understood. This study investigates the effect of two selective antagonists of the ER, Fulvestrant (Fulv) and Tamoxifen (Tam), on the invasive ability of breast cancer cells. We found that 17β-estradiol (E2) demonstrated a protective role regarding cell migration and invasion. Fulv did not alter this effect while Tam stimulated active cell migration according to an increase in Snail and a decrease in E-cadherin protein expression. Furthermore, both tested agents increased expression of matrix metalloproteinases (MMPs) and enhanced invasive potential of breast cancer cells. These changes were in line with focal adhesion kinase (FAK) rearrangement. Our data indicate that the anti-estrogens counteracted the protective role of E2 concerning migration and invasion since their effect was not limited to antiproliferative events. Although Fulv caused a less aggressive result compared to Tam, the benefits of hormonal therapy concerning invasion and metastasis yet remain to be investigated.

Synergy between RA and TLR3 promotes type I IFN-dependent apoptosis through upregulation of TRAIL pathway in breast cancer cells

Due to its ability to regulate the growth, differentiation and apoptosis of cancer cells, retinoic acid (RA) is considered a signaling molecule with promising therapeutic potential in oncology. In this study, we show that RA is able to induce the intrinsic ability of breast cancer cells to recognize double-stranded RNA (dsRNA) through the upregulation of Toll-like receptor 3 (TLR3) expression. RA, co-administered with the dsRNA mimicker polyinosinic–polycytidylic acid (poly(I:C)), synergizes to mount a specific response program able to sense dsRNA through the concurrent upregulation of TLR3, the dsRNA helicases melanoma differentiation-associated antigen-5 (MDA-5) and RA-inducible gene-1 (RIG-1), and the dsRNA-activated protein kinase (PKR) expression, leading breast cancer cells to specifically express downstream transcriptional targets of dsRNA sensors, such as interferon-β (IFNβ), interleukin-8 (IL-8), chemokine (C-C motif) ligand 5 (CCL5), and C-X-C motif Chemokine 10 (CXCL10). A TLR3-dependent apoptotic program is also induced by RA and poly(I:C) co-treatment that correlates with the induction of the tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) and contributes to block breast cancer cell proliferation. The mechanisms of apoptosis induced by RA/poly(I:C) in breast cancer cells involve type I IFN autocrine signaling, caspase-8 and caspase-3 activation, as well as TRAIL signaling. Our results reveal important links among RA, TLR3 and TRAIL and highlight the combined use of RA and poly(I:C) as a potential effective tumor therapy by improving the apoptotic response of cancer cells with low sensitivity to the action of synthetic dsRNA.

Mitochondrial dynamics regulates migration and invasion of breast cancer cells

Mitochondria are highly dynamic and undergo constant fusion and fission that are essential for maintaining physiological functions of cells. Although dysfunction of mitochondria has been implicated in tumorigenesis, little is known about the roles of mitochondrial dynamics in metastasis, the major cause of cancer death. In the present study, we found a marked upregulation of mitochondrial fission protein dynamin-related protein 1 (Drp1) expression in human invasive breast carcinoma and metastases to lymph nodes. Compared to non-metastatic breast cancer cells, mitochondria also were more fragmented in metastatic breast cancer cells that express higher levels of total and active Drp1 and less mitochondrial fusion protein 1 (Mfn1). Silencing Drp1 or overexpression of Mfn1 resulted in mitochondria elongation or clusters, respectively, and significantly suppressed metastatic abilities of breast cancer cells. In contrast, silencing Mfn proteins led to mitochondrial fragmentation and enhanced metastatic abilities of breast cancer cells. Interestingly, these manipulations of mitochondrial dynamics altered the subcellular distribution of mitochondria in breast cancer cells. For example, silencing Drp1 or overexpression of Mfn1 inhibited lamellipodia formation, a key step for cancer metastasis, and suppressed chemoattractant-induced recruitment of mitochondria to lamellipodial regions. Conversely, silencing Mfn proteins resulted in more cell spreading and lamellipodia formation, causing accumulation of more mitochondria in lamollipodia regions. More importantly, treatment with a mitochondrial uncoupling agent or ATP synthesis inhibitor reduced lamellipodia formation and decreased breast cancer cell migration and invasion, suggesting a functional importance of mitochondria in breast cancer metastasis. Together, our findings show a new role and mechanism for regulation of cancer cell migration and invasion by mitochondrial dynamics. Thus targeting dysregulated Drp1-dependent mitochondrial fission may provide a novel strategy for suppressing breast cancer metastasis.