Integrin beta1-mediated invasion of human breast cancer cells: an ex vivo assay for invasiveness

Elucidating the expression and function of Numbl during cell adhesion-mediated drug resistance (CAM-DR) in multiple myeloma (MM)

Background

Cell adhesion-mediated drug resistance (CAM-DR) is a major clinical problem that prevents successful treatment of multiple myeloma (MM). In particular, the expression levels of integrin β1 and its sub-cellular distribution (internalization and trafficking) are strongly associated with CAM-DR development.

Methods

Development of an adhesion model of established MM cell lines and detection of Numbl and Integrinβ1 expression by Western Blot analysis. The interaction between Numbl and Integrinβ1 was assessed by a co-immunoprecipitation (CO-IP) method. Calcein AM assay was performed to investigate the levels of cell adhesion. Finally, the extent of CAM-DR in myeloma cells was measured using cell viability assay and flow cytometry analysis.

Results

Our preliminary date suggest that Numbl is differentially expressed in a cell adhesion model of MM cell lines. In addition to binding to the phosphotyrosine-binding (PTB) domain, the carboxyl terminal of Numbl can also interact with integrin β1 to regulate the cell cycle by activating the pro-survival PI3K/AKT signaling pathway. This study intends to verify and elucidate the interaction between Numbl and integrin β1 and its functional outcome on CAM-DR. We have designed and developed a CAM-DR model using MM cells coated with either fibronectin or bone marrow stromal cells. We assessed whether Numbl influences cell-cycle progression and whether it, in turn, contributes to activation of PI3K/AKT signal pathway through the adjustment of its carboxyl end. Finally, we showed that the interaction of Numbl with integrin β1 promotes the formation of CAM-DR in MM cells.

Conclusions

Our findings elucidated the specific molecular mechanisms of CAM-DR induction and confirmed that Numbl is crucial for the development of CAM-DR in MM cells.

Microenvironmental networks promote tumor heterogeneity and enrich for metastatic cancer stem-like cells in Luminal-A breast tumor cells

The roles of the tumor microenvironment (TME) in generating intra-tumoral diversity within each specific breast cancer subtype are far from being fully elucidated. In this study, we exposed Luminal-A breast cancer cells in culture to combined “TME Stimulation”, representing three typical arms of the breast TME: hormonal (estrogen), inflammatory (tumor necrosis factor α) and growth-promoting (epidermal growth factor). In addition to enriching the tumor cell population with CD44+/β1+ cells (as we previously published), TME Stimulation selected for CD44+/CD24^low/− stem-like cells, that were further enriched by doxorubicin treatment and demonstrated high plasticity in vitro and in vivo. Knock-down experiments revealed that CD44 and Zeb1 regulated CD24 and β1 expression and controlled differently cell spreading and formation of cellular protrusions. TME-enriched CD44+/CD24^low/− stem-like cells promoted dissemination to bones and lymph nodes, whereas CD44+/β1+ cells had a low metastatic potential. Mixed co-injections of TME-enriched CD44+/CD24^low/− and CD44+/β1+ sub-populations generated metastases populated mostly by CD44+/CD24^low/−-derived cells. Thus, combined activities of several TME factors select for CD44+/CD24^low/− stem-like cells that dictate the metastatic phenotype of Luminal-A breast tumor cells, suggesting that therapeutic modalities targeting the TME could be introduced as a potential strategy of inhibiting the detrimental stem-like sub-population in this disease subtype.

The integrin αvβ6: a novel target for CAR T-cell immunotherapy?

Immunotherapy of cancer using chimeric antigen receptor (CAR) T-cells is a rapidly expanding field. CARs are fusion molecules that couple the binding of a tumour-associated cell surface target to the delivery of a tailored T-cell activating signal. Re-infusion of such genetically engineered T-cells to patients with haematological disease has demonstrated unprecedented response rates in Phase I clinical trials. However, such successes have not yet been observed using CAR T-cells against solid malignancies and this is, in part, due to a lack of safe tumour-specific targets. The αvβ6 integrin is strongly up-regulated in multiple solid tumours including those derived from colon, lung, breast, cervix, ovaries/fallopian tube, pancreas and head and neck. It is associated with poorer prognosis in several cancers and exerts pro-tumorigenic activities including promotion of tumour growth, migration and invasion. By contrast, physiologic expression of αvβ6 is largely restricted to wound healing. These attributes render this epithelial-specific integrin a highly attractive candidate for targeting using immunotherapeutic strategies such as CAR T-cell adoptive immunotherapy. This mini-review will discuss the role and expression of αvβ6 in cancer, as well as its potential as a therapeutic target.

Ubiquitous Release of Exosomal Tumor Suppressor miR-6126 from Ovarian Cancer Cells

Cancer cells actively promote their tumorigenic behavior by reprogramming gene expression. Loading intraluminal vesicles with specific miRNAs and releasing them into the tumor microenvironment as exosomes is one mechanism of reprogramming whose regulation remains to be elucidated. Here, we report that miR-6126 is ubiquitously released in high abundance from both chemosensitive and chemoresistant ovarian cancer cells via exosomes. Overexpression of miR-6126 was confirmed in healthy ovarian tissue compared with ovarian cancer patient samples and correlated with better overall survival in patients with high-grade serous ovarian cancer. miR-6126 acted as a tumor suppressor by directly targeting integrin-β1, a key regulator of cancer cell metastasis. miR-6126 mimic treatment of cancer cells resulted in increased miR-6126 and decreased integrin-β1 mRNA levels in the exosome. Functional analysis showed that treatment of endothelial cells with miR-6126 mimic significantly reduced tube formation as well as invasion and migration capacities of ovarian cancer cells in vitro Administration of miR-6126 mimic in an orthotopic mouse model of ovarian cancer elicited a relative reduction in tumor growth, proliferating cells, and microvessel density. miR-6126 inhibition promoted oncogenic behavior by leading ovarian cancer cells to release more exosomes. Our findings provide new insights into the role of exosomal miRNA-mediated tumor progression and suggest a new therapeutic approach to disrupt oncogenic phenotypes in tumors. Cancer Res; 76(24); 7194-207. ©2016 AACR.

miR-720 is a downstream target of an ADAM8-induced ERK signaling cascade that promotes the migratory and invasive phenotype of triple-negative breast cancer cells

BACKGROUND

ADAM8 (a disintegrin and metalloproteinase 8) protein promotes the invasive and metastatic phenotype of triple-negative breast cancer (TNBC) cells. High ADAM8 expression in breast cancer patients is an independent predictor of poor prognosis. Here, we investigated whether ADAM8 regulates specific miRNAs, their roles in aggressive phenotype, and potential use as biomarkers of disease.

METHODS

Microarray analysis was performed on RNA from MDA-MB-231 cells after transient ADAM8 knockdown using TaqMan miRNA cards. Changes in miRNA levels were confirmed using two ADAM8 siRNAs in TNBC cell lines. Kinase inhibitors, β1-integrin antagonist antibody, and different forms of ADAM8 were employed to elucidate the signaling pathway required for miR-720 expression. miR-720 levels were modulated using a specific antagomiR or a mimic, and effects on aggressive phenotype of TNBC cells were determined using Boyden chamber and 3D-Matrigel outgrowth assays. Plasma was isolated from mice before and after implantation of MDA-MB-231 cells and analyzed for miR-720 levels. Serum samples of TNBC patients were evaluated for their ADAM8 and miR-720 levels.

RESULTS

We identified 68 miRNAs differentially regulated upon ADAM8 knockdown, including decreased levels of secreted miR-720. Ectopic overexpression of wild-type ADAM8 or forms that lack metalloproteinase activity similarly induced miR-720 levels. The disintegrin and cysteine-rich domains of ADAM8 were shown to induce miR-720 via activation of a β1-integrin to ERK signaling cascade. Knockdown of miR-720 led to a significant decrease in migratory and invasive abilities of TNBC cells. Conversely, miR-720 overexpression rescued these properties. A profound increase in plasma levels of miR-720 was detected 7 days after TNBC cell inoculation into mouse mammary fat pads when tumors were barely palpable. Concordantly, miR-720 levels were found to be significantly higher in serum samples of TNBC patients with high ADAM8 expression.

CONCLUSIONS

We have shown for the first time that miR-720 is induced by ADAM8 signaling via ERK and plays an essential role in promoting the aggressive phenotype of TNBCs. miR-720 is elevated in serum of patients with ADAM8-high TNBC and, in a group with other miRNAs downstream of ADAM8, holds promise as a biomarker for early detection of or treatment response of ADAM8-positive TNBCs.

Downregulation of Integrins in Cancer Cells and Anti-Platelet Properties Are Involved in Holothurian Glycosaminoglycan-Mediated Disruption of the Interaction of Cancer Cells and Platelets in Hematogenous Metastasis

Activated platelets have been recognized as an accessory character in the cascade of tumor hematogenous metastasis, and intervention of tumor cell attachment to the activated platelets or microemboli formation might be a leading strategy to prevent tumor cells surviving in the blood vessels and sequential metastasis. Recently, we have demonstrated that holothurian glycosaminoglycan (hGAG), a sulfated polysaccharide with potent anticoagulant activity extracted from the sea cucumber Holothuria leucospilota Brandt, was highly efficacious against tumor metastasis. In this study, we identified the potential effects of hGAG on the disruption of interactions of cancer cells and platelets and the underlying mechanisms, which were supported by the following evidence: hGAG (1) inhibited thrombin-induced platelet activation and aggregation, (2) reduced adhesion between platelet and breast cancer cells, and abrogated platelets/cancer cells adhering to fibrinogen, (3) attenuated platelet-cancer cell complex formation (the number and size of aggregates) and (4) suppressed both mRNA and protein levels of β1 and β3 integrins, matrix metalloproteinase (MMP)-2 and MMP-9, while increasing the expression of the MMP inhibitor, tissue inhibitor of metalloproteinase (TIMP)-1 in MDA-MB-231 cells. These results suggested that both the antiplatelet properties and mitigation of the levels of cellular adhesion molecules contributed to the anticancer effects of hGAG, and might thus be exploited for clinical adjuvant therapy to attenuate tumor hematogenous metastasis.

Prolactin-induced protein in breast cancer

Prolactin-induced protein (PIP) is a 17-kDa single polypeptide chain that is secreted by a number of normal apocrine cells, such as milk, saliva, and seminal fluid. PIP is widely expressed in breast cancer and is commonly used as a diagnostic biomarker for the histopathological diagnosis of this disease. Expression of PIP in breast cancer is regulated by androgen and prolactin through a number of transcription factors and signaling cross-talks, including STAT5, Runx2, and CREB1. Notably, PIP is induced by a positive feedback loop between androgen receptor (AR) and extracellular signal-regulated kinase (ERK). The available data indicate that PIP has an aspartyl protease activity that can degrade fibronectin. Importantly, PIP is necessary for outside-in activation of integrin-β1 signaling pathway and regulation of key downstream signaling targets of this pathway such as interaction of integrin-β1 with integrin-linked kinase 1 (ILK1) and ErbB2. Furthermore, the importance of PIP in cell proliferation has been demonstrated by the fact that purified PIP promotes growth of breast cancer cells and PIP expression is necessary for the proliferation of T-47D and MDA-MB-453 cell lines. In addition to cell proliferation, PIP mediates invasion of breast cancer cells in a process that partially depends on the degradation of fibronectin by this protein. Therefore, PIP is a breast cancer-related protein that is expressed in a majority of breast tumors and has a significant function in the biology of this disease.

Angiotensin modulates human mammary epithelial cell motility

INTRODUCTION

Angiotensin II is an effector peptide showing multiple physiological effects, such as regulation of vascular tone, tissue growth and remodelling. Postlactational involution of mammary gland involves changes such as high matrix metalloproteinase activity and release of bioactive fragments of fibronectin and laminin, which may be directly regulated by angiotensin II. The aim of the present study was to evaluate the influence of angiotensin II on proliferation, viability and motility of normal human mammary epithelial cells (184A1 cell line) and to determine the role of angiotensin II receptors in these processes.

MATERIALS AND METHODS

Real-time reverse transcription-PCR, western blot and gelatin zymography were used to study the effect of angiotensin II on the expression of angiotensin receptors and matrix metalloproteinases in 184A1 cells. WST-1, AlamarBlue and BrdU assays were used as indicators of cell viability and proliferation after angiotensin II stimulation. Boyden chamber assays and monolayer wound migration assay were used to evaluate in vitro the changes in cell adhesion, migration and invasion.

RESULTS

Angiotensin II increased motility of the 184A1 cells and the ability of wound closure. Modifications in cell-substrate adhesion systems and increased secretion and activity of matrix metalloproteinases were also observed. The effect of angiotensin II was abolished by blocking angiotensin type 1 receptor with specific inhibitors candesartan and losartan.

CONCLUSIONS

The results indicate that angiotensin II modulates cell behaviour via AT1-R and stimulates secretion of MMP-2 by human mammary epithelial cells.

Prolactin-induced protein mediates cell invasion and regulates integrin signaling in estrogen receptor-negative breast cancer

Introduction

Molecular apocrine is a subtype of estrogen receptor (ER)-negative breast cancer that is characterized by a steroid-response gene signature. We have recently identified a positive feedback loop between androgen receptor (AR) and extracellular signal-regulated kinase (ERK) signaling in this subtype. In this study, we investigated the transcriptional regulation of molecular apocrine genes by the AR-ERK feedback loop.

Methods

The transcriptional effects of AR and ERK inhibition on molecular apocrine genes were assessed in cell lines. The most regulated gene in this process, prolactin-induced protein (PIP), was further studied using immunohistochemistry of breast tumors and xenograft models. The transcriptional regulation of PIP was assessed by luciferase reporter assay and chromatin immunoprecipitation. The functional significance of PIP in cell invasion and viability was assessed using siRNA knockdown experiments and the mechanism of PIP effect on integrin-β1 signaling was studied using immunoblotting and immunoprecipitation.

Results

We found that PIP is the most regulated molecular apocrine gene by the AR-ERK feedback loop and is overexpressed in ER-/AR+ breast tumors. In addition, PIP expression is regulated by AR-ERK signaling in xenograft models. These observations are explained by the fact that PIP is a target gene of the ERK-CREB1 pathway and is also induced by AR activation. Furthermore, we demonstrated that PIP has a significant functional role in maintaining cell invasion and viability of molecular apocrine cells because of a positive regulatory effect on the Integrin-ERK and Integrin-Akt signaling pathways. In fact, PIP-knockdown markedly decreases the phosphorylation of ERK, Akt, and CREB1. Importantly, PIP knockdown leads to a marked reduction of integrin-β1 binding to ILK1 and ErbB2 that can be reversed by the addition of fibronectin fragments.

Conclusions

We have identified a novel feedback loop between PIP and CREB1 mediated through the Integrin signaling pathway. In this process, PIP cleaves fibronectin to release fragments that activate integrin signaling, which in turn increases PIP expression through the ERK-CREB1 pathway. In addition, we demonstrated that PIP expression has a profound effect on cell invasion and the viability of molecular apocrine cells. Therefore, PIP signaling may be a potential therapeutic target in molecular apocrine breast cancer.

β1-integrins signaling and mammary tumor progression in transgenic mouse models: implications for human breast cancer

Consistent with their essential role in cell adhesion to the extracellular matrix, integrins and their associated signaling pathways have been shown to be involved in cell proliferation, migration, invasion and survival, processes required in both tumorigenesis and metastasis. β1-integrins represent the predominantly expressed integrins in mammary epithelial cells and have been proven crucial for mammary gland development and differentiation. Here we provide an overview of the studies that have used transgenic mouse models of mammary tumorigenesis to establish β1-integrin as a critical mediator of breast cancer progression and thereby as a potential therapeutic target for the development of new anticancer strategies.

Unraveling the microenvironmental influences on the normal mammary gland and breast cancer

The normal mammary gland and invasive breast tumors are both complex 'organs' composed of multiple cell types as well as extracellular matrix in three-dimensional (3D) space. Conventionally, both normal and malignant breast cells are studied in vitro as two-dimensional monolayers of epithelial cells, which results in the loss of structure and tissue function. Many laboratories are now investigating regulation of signaling function in the normal mammary gland using 3D cultures. However, it is also important to assay malignant breast cells ex vivo in a physiologically relevant environment to more closely mimic tumor architecture, signal transduction regulation and tumor behavior in vivo. Here we present the potential of these 3D models for drug testing, target validation and guidance of patient selection for clinical trials. We also argue that in order to get full insight into the biology of the normal and malignant breast, and to create in vivo-like models for therapeutic approaches in humans, we need to continue to create more complex heterotypic models to approach the full context the cells encounter in the human body.

Beta3 integrin and Src facilitate transforming growth factor-beta mediated induction of epithelial-mesenchymal transition in mammary epithelial cells

Introduction

Transforming growth factor (TGF)-β suppresses breast cancer formation by preventing cell cycle progression in mammary epithelial cells (MECs). During the course of mammary tumorigenesis, genetic and epigenetic changes negate the cytostatic actions of TGF-β, thus enabling TGF-β to promote the acquisition and development of metastatic phenotypes. The molecular mechanisms underlying this conversion of TGF-β function remain poorly understood but may involve signaling inputs from integrins.

Methods

β₃ Integrin expression or function in MECs was manipulated by retroviral transduction of active or inactive β₃ integrins, or by transient transfection of small interfering RNA (siRNA) against β₃ integrin. Altered proliferation, invasion, and epithelial-mesenchymal transition (EMT) stimulated by TGF-β in control and β₃ integrin manipulated MECs was determined. Src involvement in β₃ integrin mediated alterations in TGF-β signaling was assessed by performing Src protein kinase assays, and by interdicting Src function pharmacologically and genetically.

Results

TGF-β stimulation induced α_vβ₃ integrin expression in a manner that coincided with EMT in MECs. Introduction of siRNA against β₃ integrin blocked its induction by TGF-β and prevented TGF-β stimulation of EMT in MECs. β₃ integrin interacted physically with the TGF-β receptor (TβR) type II, thereby enhancing TGF-β stimulation of mitogen-activated protein kinases (MAPKs), and of Smad2/3-mediated gene transcription in MECs. Formation of β₃ integrin:TβR-II complexes blocked TGF-β mediated growth arrest and increased TGF-β mediated invasion and EMT. Dual β₃ integrin:TβR-II activation induced tyrosine phosphorylation of TβR-II, a phosphotransferase reaction mediated by Src in vitro. Inhibiting Src activity in MECs prevented the ability of β₃ integrin to induce TβR-II tyrosine phosphorylation, MAPK activation, and EMT stimulated by TGF-β. Lastly, wild-type and D119A β₃ integrin expression enhanced and abolished, respectively, TGF-β stimulation of invasion in human breast cancer cells.

Conclusion

We show that β₃ integrin alters TGF-β signaling in MECs via Src-mediated TβR-II tyrosine phosphorylation, which significantly enhanced the ability of TGF-β to induce EMT and invasion. Our findings suggest that β₃ integrin interdiction strategies may represent an innovative approach to re-establishing TGF-β mediated tumor suppression in progressing human breast cancers.

Expression of integrin beta1 and its roles on adhesion between different cell cycle hepatocellular carcinoma cells (SMMC-7721) and human umbilical vein endothelial cells

To investigate expression of integrin beta1 and its roles on adhesion between different cell cycle hepatocellular carcinoma cell (HCC) and human umbilical vein endothelial cells (HUVEC), the synchronous G1 and S phase HCC were achieved through thymine-2-deoxyriboside and colchicines sequential blockage method and double thymine-2-deoxyriboside blockage method, respectively. Expression of integrin beta1 on hepatocellular carcinoma cells was detected with flow cytometer. Further, the adhesive force of HCC to HUVEC and the role of integrin beta1 in this adhesive course were studied by micropipette aspiration technique. The results showed that percentage of each cyclic phases of the controlled HCC (non-synchronous) are: G2 + M phase, 11%; G1 phase, 54%; S phase, 36%; the synchronous rates of G1 and S phase HCC amount to 74 and 98%, respectively. The expressive fluorescent intensity of integrin beta1 in G1 phase HCC is depressed significantly than the values of S phase and controlled HCC. Accordingly, the adhesive forces of G1 phase HCC to HUVEC was significantly lower than the value of S phase cells (P < 0.01), but it has no remarkable difference when compared the adhesive force values of S phase HCC with control; the contribution of integrin beta1 was about 50% in the adhesion of HCC to HUVEC. It suggested that HCC would be synchronized preferably in G1 and S phase with thymine-2-deoxyriboside and colchicines, the adhesive molecule integrin beta1 expressed in a high lever in HCC and presented differences in vary cell cycle, and integrin beta1 played an important roles in adhesion of HCC to HUVEC. Possibly, S phase HCC take a great action in this adhesive course.

Basement membrane proteins play an active role in the invasive process of human hepatocellular carcinoma cells with high metastasis potential

PURPOSE

Cell-matrix adhesive interaction has an important role in the invasive process of tumor cells, and integrins are the major receptors mediating cell-matrix adhesion. The current study is to investigate the modulation of basement membrane (BM) proteins, especially collagen IV (C IV), laminin (LN), and fibronectin (FN) in the invasive processes of human hepatocellular carcinoma (HCC) cells in vitro, and to reveal the roles of beta1 integrins and RGD-containing oligopeptide in the cell-matrix interaction.

METHODS

Static adhesion assay was performed to study the rates of adhesion of MHCC97-H cells, treated or untreated with anti-beta1 (2 microg ml(-1)) and GRGDS, to C IV (50 microg ml(-1)), LN (50 microg ml(-1)) or FN (50 microg ml(-1)). Gelatin zymography was used to detect the secretion of MMPs in the conditioned medium of MHCC97-H cells incubated 24 h by C IV, LN or FN, and interactions with anti-beta1 and GRGDS. Transwell chamber assay was used to investigate the influence of C IV, LN or FN, interacting with anti-beta1 and GRGDS, on the cellular mobility of MHCC97-H cells.

RESULTS

Compared with blank control group, MHCC97-H cells showed significantly higher rates of adhesion to C IV, LN, and FN. Pretreatment with anti-beta1 could suppress adhesion to C IV, LN or FN, but GRGDS inhibited adhesion to FN (P<0.05) only. LN and FN could stimulate the secretion of MMPs by MHCC97-H cells cultured in vitro, especially MMP-9 and its activated type. Treatment with anti-beta1 could partly counteract the effects of LN and FN. GRGDS could prominently induce the secretion of MMPs, but the effect could be inhibited by pretreatment of anti-beta1. The results of Transwell chamber assay showed that LN, FN, and GRGDS could increase the number of tumor cells penetrating the microporous membrane, but the data of C IV did not reach significance. The effects were partly counteracted by anti-beta1.

CONCLUSION

BM proteins play an active role in the invasive process of human hepatocellular carcinoma cells. Integrin beta1 is an important molecule which mediates the cell-matrix adhesive interaction of tumor cells. RGD-containing peptides competitively combine with the binding site of integrin beta1, and the effects of FN are RGD sequence-dependent.

Protein kinase C alpha/beta inhibitor Go6976 promotes formation of cell junctions and inhibits invasion of urinary bladder carcinoma cells

Changes in activation balance of different protein kinase C (PKC) isoenzymes have been linked to cancer development. The current study investigated the effect of different PKC inhibitors on cellular contacts in cultured high-grade urinary bladder carcinoma cells (5637 and T24). Exposure of the cells to isoenzyme-specific PKC inhibitors yielded variable results: Go6976, an inhibitor of PKCalpha and PKCbeta isoenzymes, induced rapid clustering of cultured carcinoma cells and formation of an increased number of desmosomes and adherens junctions. Safingol, a PKCalpha inhibitor, had similar but less pronounced effects. In contrast, a PKCdelta inhibitor, rottlerin, had an opposite effect on cell clustering and caused dissociation of cell junctions. A broad-spectrum PKC inhibitor bisindolylmaleimide I did not have any apparent effect on the morphology of the cultures or on the number of cell junctions. Additional studies with Go6976 demonstrated that inhibition of PKCalpha and beta isoenzymes induced translocation of beta1-integrin from the cell-matrix junctions and that beta4-integrin was translocated to face the culture substratum. Go6976 was also highly effective in inhibiting migration of carcinoma cells and inhibited invasion through artificial basement membrane. Our results on urinary bladder carcinoma cells emphasize that Go6976 is a potential anticancer drug due to its effects on cell-cell and cell-matrix junctions, migration, and invasion. Furthermore, the results may be explained by changes in PKC activation balance promoted by inhibition of PKCalpha/beta.