Core fucosylation of E-cadherin enhances cell–cell adhesion in human colon carcinoma WiDr cells

α1,6‐Fucosyltransferase (Fut8), an enzyme that catalyzes the introduction of α1,6 core fucose to the innermost N‐acetylglucosamine residue of the N‐glycan, has been implicated in the development, immune system, and tumorigenesis. We found that α1,6‐fucosyltransferase and E‐cadherin expression levels are significantly elevated in primary colorectal cancer samples. Interestingly, low molecular weight population of E‐cadherin appeared as well as normal sized E‐cadherin in cancer samples. To investigate the correlation between α1,6‐fucosyltransferase and E‐cadherin expression, we introduced α1,6‐fucosyltransferase in WiDr human colon carcinoma cells. It was revealed that the low molecular weight population of E‐cadherin was significantly increased in α1,6‐fucosyltransferase‐transfected WiDr cells in dense culture, which resulted in an enhancement in cell–cell adhesion. The transfection of mutated α1,6‐fucosyltransferase with no enzymatic activity had no effect on E‐cadherin expression, indicating that core fucosylation is involved in the phenomena. In α1,6‐fucosyltransferase knock down mouse pancreatic acinar cell carcinoma TGP49 cells, the expression of E‐cadherin and E‐cadherin dependent cell–cell adhesion was decreased. The introduction of α1,6‐fucosyltransferase into kidney epithelial cells from α1,6‐fucosyltransferase^–/– mice restored the expression of E‐cadherin and E‐cadherin‐dependent cell–cell adhesion. Based on the results of lectin blotting, peptide N‐glycosidase F treatment, and pulse‐chase studies, it was demonstrated that the low molecular weight population of E‐cadherin contains peptide N‐glycosidase F insensitive sugar chains, and the turnover rate of E‐cadherin was reduced in α1,6‐Fucosyltransferase transfectants. Thus, it was suggested that core fucosylation regulates the processing of oligosaccharides and turnover of E‐cadherin. These results suggest a possible role of core fucosylation in the regulation of cell–cell adhesion in cancer. (Cancer Sci 2009; 100: 888–896)     

Genistein抑制乳腺癌细胞生长的机制

目的 Ｇｅｎｉｓｔｅｉｎ抑制乳腺癌细胞生长的机制。方法 研究主要应用于Ｎｏｒｔｈｅｒｎ印迹杂交,Ｗｅｓｔｅｒｎ印迹杂交,质粒转染技术以及细胞凋亡检测法,探讨Ｇｅｎｉｓｔｅｉｎ抑制乳腺癌细胞生长的机制。结果 Ｇｅｎｉｓｔｅｉｎ可明显抑制不同ＥＲ状态和不同ｐ５３状态的乳腺癌细胞系的生长,同时显著诱导ｐ５３下游基因ｐ２１＾ＷＡＦ／ＣＩＰＩ蛋白和ｍＲＮＡ的表达,而导致ｐ２１＾ＷＡＦＩ／ＣＩＰＩ的表达增强主     

Expression of E-cadherin in 230 infiltrating ductal breast carcinoma

The immunohistochemical expression of E-cadherin (E-CD) was correlated to differentiation grade, tumor size, axillary lymph node metastasis, hormone receptor status and disease outcome in 230 infiltrating ductal breast carcinomas. E-CD expression was reduced in 116 tumors (50.4%). Reduced E-CD expression was more frequently found in high histological grade and progesterone receptor negative tumors. In contrast, preserved E-CD expression was more frequently observed in tumors with axillary lymph node metastasis, particularly in the group of patients with 1 to 3 positive lymph nodes. A weak association between reduced E-CD expression and shortened overall survival was found in univariate survival analysis, that was lost when the patients were adjusted for other pathological factors in multivariate analysis. These data indicate that E-CD may be considered a differentiation marker in ductal carcinomas of non special type. However, the relationship between E-CD expression and lymph node metastasis and disease outcome remains to be established.     

Knockdown of focal adhesion kinase reverses colon carcinoma multicellular resistance

Chemotherapy resistance in solid tumors is broad and encompasses diverse unrelated drugs. Three-dimensional multicellular spheroids (MCSs) are a good model for studying in vitro drug resistance. In the current study, we investigated the role of focal adhesion kinase (FAK) in 5-fluorouracil (5-FU) chemoresistance in colon carcinoma MCS culture cells. The expression of FAK was inhibited significantly by specific small hairpin RNA targeting FAK. The suppression of FAK expression did not affect the growth of spheroid cells. However, silencing of FAK combined with 5-FU treatment significantly decreased the 50% inhibitory concentration (IC₅₀) of 5-FU and markedly increased the population of apoptosis cells, which was associated with the reduction of the levels of Akt and nuclear factor–kappa B (NF-κB). Moreover, knockdown of FAK could inhibit tumor growth and increase the sensitivity of the tumor to 5-FU in the nude mouse xenograft. These results indicate that while not affecting cellular proliferation in the absence of 5-FU, RNA interference targeting FAK potentiated 5-FU-induced cytotoxicity in vitro and in vivo , and partially reversed multicellular resistance, which may contribute to its chemosensitizing effect through efficiently suppressing Akt/NF-κB activity. ( Cancer Sci 2009; 100: 1708–1713)     

Effects of interferon-alpha on cellular proliferation and adhesion of breast carcinoma cells

We examined the potent inhibitory effects of interferon-alpha (IFN-alpha) on both cellular adhesion and cell proliferation of MCF-7 breast carcinoma cells. When MCF-7 cells were exposed to IFN-alpha at a concentration of 5x10(3) IU/ml for 5 days, cell proliferation was markedly inhibited. Cell attachment assay demonstrated that incubation with IFN-alpha for up to 48 h reduced alpha2beta1 integrin-mediated cellular adhesion. However, fluorescence activated cell sorter (FACS) analysis revealed that incubation with IFN-alpha for 24 h had no effect upon the cell surface expressions of either alpha2 and beta1 integrin on MCF-7 cells. These antiproliferative and antiadhesive actions of IFN-alpha may be applied to treatment for patients with metastatic breast carcinoma.     

Laminin activates the p185HER2 oncoprotein and mediates growth inhibition of breast carcinoma cells.

The interaction between laminin and the oncoprotein encoded by the c-erbB-2 oncogene was studied in vitro and in vivo in human breast carcinomas. In vitro analysis of breast carcinoma cell lines overexpressing p185HER2 revealed that laminin, but not fibronectin, induced tyrosine phosphorylation and down-modulation of oncoprotein membrane expression. Laminin also specifically inhibited growth of p185HER2-positive cell lines. No direct binding between the recombinant extracellular domain of p185HER2 and laminin was found. Induction of oncoprotein down-modulation by anti-integrin antibodies and coprecipitation of the oncoprotein with the beta 4 integrin subunit indicate that the interaction between p185HER2 and laminin occurs through integrin molecules. The relevance of this in vitro observation was verified in vivo by analysing the prognostic value of p185HER2 overexpression as a function of laminin production on archival paraffin-embedded sections of 887 primary breast tumours. The results revealed an association between p185HER2 overexpression and unfavourable prognosis in tumours negative for laminin production, whereas in laminin-producing tumours, the oncoprotein overexpression was not associated with tumour aggressiveness.     

E-cadherin mediates the aggregation of breast cancer cells induced by tamoxifen and epidermal growth factor

In the present study, we evaluated the ability of 4-hydroxytamoxifen (OHT) and epidermal growth factor (EGF) to regulate homotypic adhesion in MCF7 breast cancer cells. Our results demonstrate that OHT and EGF activate the E-cadherin promoter, increase E-cadherin mRNA and protein expression and enhance homotypic aggregation of MCF7 cells. Interestingly, an ERα and EGFR cross-talk is involved in the E-cadherin expression by OHT and EGF, as demonstrated by knocking down either receptor. On the basis of our findings, the well-established cross-talk between ERα and EGFR could be extended to the modulation of E-cadherin expression by OHT and EGF. Thus, the potential ability of tamoxifen to induce cell–cell aggregation may contribute to the biologic response of pharmacologic intervention in patients with breast cancer.     

Extracellular calcium increases bisphosphonate-induced growth inhibition of breast cancer cells

Introduction

Bisphosphonates have become standard therapy for the treatment of skeletal complications related to breast cancer. Although their therapeutic effects mainly result from an inhibition of osteoclastic bone resorption, in vitro data indicate that they also act directly on breast cancer cells, inhibiting proliferation and inducing apoptosis.

Methods

The present study examined the effects of calcium (from 0.6 to 2.0 mmol/l) on the antitumour activity of the bisphosphonate ibandronate (1 to 1,000 nmol/l) on MDA-MB-231 and MCF-7 breast cancer cells. Cell culture densities were determined using crystal violet staining assay. Apoptotic cell death was assessed by annexin V-phycoerythrin and 7-amino-actinomycin double staining.

Results

At low calcium concentration, 30 μmol/l ibandronate had no effect on MDA-MB-231 cells growth and only slightly inhibited MCF-7 cells growth. Higher calcium levels significantly increased growth inhibition as well as cell apoptosis induced by ibandronate. We observed similar effects with zoledronic acid. Of note, enhancement of ibandronate-induced growth inhibition was also observed in other breast cancer cell lines (T-47D, ZR-75, Hs-578T and BT-549 cells). The growth inhibitory effect of ibandronate in the presence of high concentrations of calcium was partly suppressed by the calcium chelator EGTA (ethylene glycol tetra-acetic acid). In addition, in the presence of calcium at high concentrations, cells accumulated more [¹⁴C]ibandronate than at low calcium concentrations. We obtained further evidence of enhancement of cellular ibandronate accumulation by calcium by demonstrating that high calcium levels increased the inhibition of protein prenylation induced by the bisphosphonate.

Conclusion

Altogether, our data suggest that extracellular calcium, probably through its binding to ibandronate, markedly increased its cellular accumulation and its inhibitory activity on breast tumour cells. Thus, calcium released during the process of tumour-induced osteolysis might enhance the antitumour effects of bisphosphonates and contribute to their therapeutic efficacy.     

Cell surface heparan sulfate proteoglycans control adhesion and invasion of breast carcinoma cells

Background

Cell surface proteoglycans interact with numerous regulators of cell behavior through their glycosaminoglycan chains. The syndecan family of transmembrane proteoglycans are virtually ubiquitous cell surface receptors that are implicated in the progression of some tumors, including breast carcinoma. This may derive from their regulation of cell adhesion, but roles for specific syndecans are unresolved.

Methods

The MDA-MB231 human breast carcinoma cell line was exposed to exogenous glycosaminoglycans and changes in cell behavior monitored by western blotting, immunocytochemistry, invasion and collagen degradation assays. Selected receptors including PAR-1 and syndecans were depleted by siRNA treatments to assess cell morphology and behavior. Immunohistochemistry for syndecan-2 and its interacting partner, caveolin-2 was performed on human breast tumor tissue arrays. Two-tailed paired t-test and one-way ANOVA with Tukey’s post-hoc test were used in the analysis of data.

Results

MDA-MB231 cells were shown to be highly sensitive to exogenous heparan sulfate or heparin, promoting increased spreading, focal adhesion and adherens junction formation with concomitantly reduced invasion and matrix degradation. The molecular basis for this effect was revealed to have two components. First, thrombin inhibition contributed to enhanced cell adhesion and reduced invasion. Second, a specific loss of cell surface syndecan-2 was noted. The ensuing junction formation was dependent on syndecan-4, whose role in promoting actin cytoskeletal organization is known. Syndecan-2 interacts with, and may regulate, caveolin-2. Depletion of either molecule had the same adhesion-promoting influence, along with reduced invasion, confirming a role for this complex in maintaining the invasive phenotype of mammary carcinoma cells. Finally, both syndecan-2 and caveolin-2 were upregulated in tissue arrays from breast cancer patients compared to normal mammary tissue. Moreover their expression levels were correlated in triple negative breast cancers.

Conclusion

Cell surface proteoglycans, notably syndecan-2, may be important regulators of breast carcinoma progression through regulation of cytoskeleton, cell adhesion and invasion.     

HGF induces FAK activation and integrin-mediated adhesion in MTLn3 breast carcinoma cells.

Expression of hepatocyte growth factor (HGF) and its tyrosine kinase receptor, c-Met, is positively correlated with breast carcinoma progression. We found that in invasive and metastatic MTLn3 breast carcinoma cells, HGF stimulated both initial adhesion to and motility on the extracellular matrix (ECM) ligands laminin 1, type I collagen, and fibronectin. Next, analysis with function-perturbing antibodies showed that adhesion to the different ECM proteins was mediated through specific beta1 integrins. In MTLn3 cells, HGF induced rapid tyrosine phosphorylation and activation of both c-Met and focal adhesion kinase (FAK). Cell anchorage and adhesion to the ECM substrates was required for HGF-induced FAK activation, since HGF failed to trigger tyrosine phosphorylation of FAK in suspended cells. Our results provide evidence that the 2 signaling pathways, integrin/ECM and c-Met/HGF, cooperate synergistically to induce FAK activation in an adhesion-dependent manner, leading to enhanced cell adhesion and motility. Moreover, we found that a FRNK (the FAK-related non-kinase)-like molecule is expressed in MTLn3 cells. Since FRNK acts as a competitive inhibitor of FAK function, our results suggest that a FRNK-like protein could facilitate disassembly of focal adhesions and likely be responsible for the HGF-induced scattering and motility of MTLn3 cells.     

红景天对乳腺癌抑制作用的研究

目的:通过体外和体内实验研究红景天对乳腺癌的增殖抑制作用和浸润转移相关因子表达的影响。方法:采用不同浓度红景天提取物处理乳腺癌MDA-MB-435细胞,制作细胞增殖曲线,观察药物对肿瘤细胞增殖活性的影响;应用流式细胞仪检测红景天提取物对乳腺癌细胞的细胞周期阻滞作用;选择裸鼠乳腺癌MDA-MB-435细胞移植瘤模型,以免疫组织化学染色方法研究红景天提取物对裸鼠移植瘤内MMP-2和组织蛋白酶D(CathD)表达的影响。结果:红景天提取物可显著抑制MDA-MB-435细胞的增殖活性,该抑制作用随着作用时间的延长、药物浓度的增高更为明显。红景天提取物具有阻滞MDA-MB-435细胞增殖周期的作用,主要阻滞于S期,该阻滞作用呈浓度依赖性。在红景天提取物治疗组裸鼠乳腺癌移植瘤中,CathD蛋白表达明显低于生理盐水对照组(免疫组化H-评分均数治疗组为72±50.70,而对照组为168±64.19,P=0.03);治疗组移植瘤MMP-2蛋白表达明显低于生理盐水对照组(免疫组化H-评分均数治疗组为90±29.15,而对照组为176±65.80,P=0.04)。结论:红景天可能通过抑制细胞增殖、浸润能力等多途径对乳腺癌细胞产生一定的抑制作用,其在乳腺癌的防治中具有一定的临床意义。     

Dominant-negative inhibition of breast cancer resistance protein as drug efflux pump through the inhibition of S-S dependent homodimerization.

Breast cancer resistance protein (BCRP) is a half-molecule ABC transporter highly expressed in mitoxantrone-resistant cells. In our study we established PA317 transfectants expressing Myc-tagged BCRP (MycBCRP) or HA-tagged BCRP (HABCRP). The exogenous BCRP protein migrated as a 70-kDa protein in SDS-PAGE under reducing condition, but migrated as a 140-kDa complex in the absence of reducing agents. The 140-kDa BCRP complex was heat-stable but dissociated into 70-kDa BCRP with the addition of 2-mercaptoethanol. The 140-kDa BCRP complex was immunoprecipitated with anti-Myc antibody from the lysates of PA317 cells double-transfected with MycBCRP and HABCRP. The 140-kDa complex reacted with anti-HA and anti-BCRP antibodies and after the addition of reducing agents, a 70-kDa protein reacting with anti-Myc, anti-HA and anti-BCRP antibodies was detected. These results clearly indicate that BCRP forms a homodimer bridged by disulfide bonds. To assess the possible dominant-negative inhibition of BCRP drug efflux pump, various mutant BCRP cDNAs were isolated by PCR mutagenesis. First, mutant BCRP cDNAs were introduced to parental PA317 cells and tested for their function as drug-resistance genes. Next, inactive BCRP cDNA clones were introduced to MycBCRP-transfected cells and tested for the ability to lower drug resistance. Among the 8 inactive mutant cDNA clones tested, HABCRP cDNA clone 15 with an amino acid change from Leu to Pro at residue 554 in the fifth transmembrane domain of BCRP partially reversed the drug resistance of MycBCRP-transfected cells. These results suggest that homodimer formation is essential for BCRP drug resistance, implicating this dominant-negative inhibition as a new strategy to circumvent drug resistance.     

Nanofiber-mediated inhibition of focal adhesion kinase sensitizes glioma stemlike cells to epidermal growth factor receptor inhibition

Background

Glioblastoma multiforme is the most common glioma in adults and carries a poor prognosis, due to tumor recurrence despite aggressive treatment. Such relapse has been attributed to the persistence of glioma stemlike cells (GSCs), a subpopulation of glioma cells with stem cell properties. Thus, targeting these cells will be critical to achieving meaningful improvement in glioblastoma multiforme survival. We investigated the role of β1-integrin signaling as one such potential target.

Methods

We used GSCs isolated from primary human gliomas and maintained in stem cell conditions. We manipulated β1-integrin signaling using a self-assembling peptide amphiphile (PA) displaying the IKVAV (isoleucine-lysine-valine-alanine-valine) epitope as well as lentiviral overexpression, and we assayed the effects on downstream effectors and apoptosis using immunofluorescence.

Results

We show that β1-integrin expression correlates with decreased survival in glioma patients and that β1-integrin is highly expressed by GSCs. The IKVAV PA potently increases immobilized β1-integrin at the GSC membrane, activating integrin-linked kinase while inhibiting focal adhesion kinase (FAK). The IKVAV PA induces striking apoptosis in GSCs via this FAK inhibition, which is enhanced in combination with inhibition of epidermal growth factor receptor (EGFR). Conversely, lentiviral overexpression of β1-integrin renders GSCs resistant to EGFR inhibition, which was overcome by FAK inhibition.

Conclusions

These observations reveal a role for β1-integrin signaling through FAK in GSC treatment resistance and introduce self-assembling PAs as a novel new therapeutic approach for overcoming this resistance.     

Addition of 2-deoxyglucose enhances growth inhibition but reverses acidification in colon cancer cells treated with phenformin

A report that effects of butyrate on some cells may be mediated by activation of AMP-activated protein kinase (AMPK) prompted this study which examines if other AMPK activators can induce differentiation and inhibit proliferation of colon cancer cells in a manner similar to butyrate. Using induction of alkaline phosphatase as a marker, it was observed that compound C, an AMPK inhibitor, is able to reduce the differentiating effect of butyrate on SW1116 and Caco-2 colon cancer cells. Metformin was observed to be less effective than butyrate in the induction of alkaline phosphatase but was more effective as a growth inhibitor. Phenformin was found to be a more potent growth inhibitor than metformin and both compounds cause acidification of the medium when incubated with colon cancer cells. Combined incubation of 2-deoxyglucose with either of the biguanides prevented the acidification of the medium but enhanced the growth inhibitory effects.