Xiuling Zhi

Ecto-5′-nucleotidase promotes invasion, migration and adhesion of human breast cancer cells

PurposeAssociated with many molecules, metastasis includes cell adhesion to extracellular matrix, migration towards specific direction and invasion into local vessel of distant organs. The purpose of the present study was to evaluate the role of ecto-5′-nucleotidase (eN, ecto-5-NT, CD73) generated extracellular adenosine in biologically malignant behaviors of human breast cancer cell lines.Materials and methodsTwo human breast cancer cell lines, T-47D with lower expression of CD73 and MB-MDA-231 with higher expression of CD73, were used to investigate the functions of CD73. The effects of CD73 over-expression on invasion, migration and adhesion were observed in T-47D transfected with pcDNA-NT5E plasmid. The effects of specific CD73 inhibitor, α, ß-methylene ADP (APCP), were observed in MB-MDA-231 cells.ResultsThe results showed CD-73 overexpression increased invasion, migration and adhesion to ECM of the pcDNA-NT5E transfected T-47D cells compared to the saline and mock vector controls. The increased cell mobility of CD-73-overexpressed T-47D cells was blocked by APCP. Adenosine increased the mobility of wild type T-47D cells. APCP inhibited the mobility of the MB-MDA-231 cells.ConclusionTaken together, our results indicated that CD73 may facilitate the adhesion, migration and invasion of human breast cancer cells through its enzyme activity of generating adenosine. This study provided a possibly molecular mechanism of metastasis of breast carcinoma.

RNA interference of ecto-5′-nucleotidase (CD73) inhibits human breast cancer cell growth and invasion

Metastasis is a leading cause of mortality and morbidity in breast cancer. Recently, dramatic overexpression of ecto-5′-nucleotidase (CD73), a glycosylphosphatidylinositol-anchored cell surface protein has been found in estrogen receptor-negative [ER (−)] breast cancer cell lines and in clinical samples. In this study, CD73 small interfering RNA (siRNA) plasmid was constructed and stably transfected into breast cancer cell MB-MDA-231 to determine the role of CD73 in breast cancer metastasis and the possible mechanism. Our study demonstrates that CD73 siRNA effectively inhibits CD73 gene expression at mRNA and protein level in MB-MDA-231 cells, leading to in vivo and in vitro growth suppression, prevention of adhesion to extracellular matrix (ECM), and inhibition of invasion and migration. These properties correlate with inhibition of matrix metalloproteinase (MMP)-2 and MMP-9 expression and activity as well as reduction of epidermal growth factor receptor (EGFR) expression. Demonstration of the role of CD73 in breast cancer may lead to new targeted therapies for breast cancer.

RNAi-mediated CD73 suppression induces apoptosis and cell-cycle arrest in human breast cancer cells

Ecto‐5′‐nucleotidase (CD73), a cell surface protein that hydrolyzes extracellular AMP into adenosine and phosphate, is overexpressed in many solid tumors. In this study, we tested the hypothesis that increased CD73 may promote tumor progression by examining the effect of CD73 suppression via RNA interference and CD73 overexpression on tumor growth in vivo and in vitro. Using digitized whole‐body images, plate clone forming assay and TUNEL assay in frozen tissue sections, we found that the cell growth rate was significantly lower in vivo and in vitro after CD73 suppression and late apoptosis was much higher in xenograft tumors developed from the CD73‐siRNA transfected MB‐MDA‐231 clone (P1). By flow cytometry, the P1 cell cycle was arrested in the G0/G1 phase. Moreover, Bcl‐2 was downregulated, while Bax and caspase‐3 were upregulated with CD73 suppression. CD73 inhibitor α,β‐methylene adenosine‐5′‐disphosphate (APCP) functioned similarly with RNAi‐mediated CD73 suppression. In addition, in transfected MCF‐7 cells, we found that CD73 overexpression increased cell viability and promoted cell cycle progression, depending on its enzyme activity. More intriguingly, CD73 overexpression in MCF‐7 breast cancer cells produces a tumorigenic phenotype. We conclude that CD73 plays an important role in breast cancer growth by affecting cell cycle progression and apoptosis. (Cancer Sci 2010; 101: 2561–2569)

Ecto-5′-nucleotidase (CD73) promotes tumor angiogenesis

Angiogenesis is essential for tumor growth, progression and metastasis. Studies indicate that expression and activity of ecto-5′-nucleotidase (CD73) are elevated in metastatic carcinomas. Our previous studies found that angiogenesis of tumor xenografts was decreased when the activity of CD73 in cancer cells was inhibited, implying that this enzyme is involved in tumor angiogenesis. To elucidate the mechanism, we investigated CD73 influence on tumor angiogenesis in both in vitro assays and in tumor bearing mice. We found that capillary-like structures were formed more in CD73+/+ pulmonary microvascular endothelial cells (PMECs) than CD73−/− PMECs, and this was more pronounced when the cells were cultured in cancer-conditioned medium. Meanwhile, CD73 decreased endothelial cells adhesion to collagen IV and promoted migration. Additionally, the extent of tumor angiogenesis and the size of tumors were greater in CD73+/+ mice than in CD73−/− mice. Thus, we concluded that CD73 can promote endothelial cells forming new vessels in cancer condition, facilitating tumor growth and hematogenous metastasis.

Potential prognostic biomarker CD73 regulates epidermal growth factor receptor expression in human breast cancer

CD73, an ecto‐enzyme overexpressed in breast‐cancer cells, catalyzes the dephosphorylation of adenosine monophosphates into adenosine. Anti‐CD73 slows breast cancer growth and its spread both in vivo and in vitro. In this study, we investigated the relation of CD73 to epidermal growth factor receptor (EGFR) expression using tissue array and breast cancer cell lines. We found that CD73 expression correlated positively to EGFR expression in vivo (n = 80, r = 0.425, P < 0.01) and in vitro. EGFR expression can be decreased by suppressing CD73 with an inhibitor or small shRNA, and this effect was reversed by adenosine and NECA (adenosine A2 receptor agonist), which suggested that adenosine is involved in EGFR expression regulated by CD73 (P < 0.01). We also showed that CD73 regulates EGFR phosphorylation by Src (P < 0.01). By transcription factor (TF) assay, CD73 was found to regulate some associated TFs activity such as PPARγ, which mediates EGFR expression, although whether PPARγ mediates the effect of CD73 on EGFR expression needs further study. The Kaplan–Meier recurrence‐free survival curves for CD73 were also plotted in www.kmplot.com. The curves show that CD73 expression separates the cases into significantly different prognostic groups among the estrogen receptor‐negative cancers (P < 0.01). Our results suggest that CD73 may be a potential prognostic biomarker associated with coexpression of EGFR in human breast cancer.

Tryptase promotes atherosclerotic plaque haemorrhage in ApoE-/- mice.

Tryptase, the most abundant mast cell (MC) granule protein, plays an important role in atherosclerosis plaque development. To test the hypothesis that tryptase participates directly in atherosclerosis plaque haemorrhage, the gene sequence and siRNA for tryptase were cloned into a lentivirus carrier and atherosclerosis plaque haemorrhage models in ApoE-/- mice were constructed. After a cuffing-cervical artery operation, the mice were randomly divided into 6 groups. Hematoxylin and eosin(HE) staining showed that the cervical artery plaque area was much larger in the tryptase overexpression group compared to the other groups, and there was greater artery stenosis. The artery stenosis from the cuff-side in all groups was more than 90%, except the siRNA group. Tryptase promotes plaque haemorrhage distinctively because 50% of the mice in the tryptase overexpression group had plaque haemorrhage, while only 10% in the siRNA group did. The immunohistochemistry of the cervical artery plaque showed that plasminogen activator inhibitor-1 (PAI-1) expression was the lowest while tissue plasminogen activator (tPA), CD31, CD34 and VEGF was the highest in the tryptase overexpression groups. This observation was completely contrary to what was observed in the siRNA group. Tryptase promoted bEnd.3 cell growth, migration and capillary-like tube formation, which suggests that tryptase can promote microvessel angiogenesis. PAI-1 expression was inhibited, while tPA expression was increased by tryptase in bEnd.3 cells. Our in vivo and in vitro studies suggest that trypase can promote atherosclerotic plaque haemorrhage by promoting angiogenesis and regulating the balance of PAI-1 and tPA. Thus, regulating tryptase expression in MCs may provide a potential target for atherosclerosis treatment.

Overexpression of steroidogenic acute regulatory protein in rat aortic endothelial cells attenuates palmitic acid-induced inflammation and reduction in nitric oxide bioavailability

BackgroundEndothelial dysfunction is a well documented evidence for the onset of atherosclerosis and other cardiovascular diseases. Lipids disorder is among the main risk factors for endothelial dysfunction in these diseases. Steroidogenic acute regulatory protein (StAR), one of the cholesterol transporters, plays an important role in the maintenance of intracellular lipid homeostasis. However, the effect of StAR on endothelial dysfunction is not well understood. Palmitic acid (PA) has been shown to decrease eNOS activity and induce inflammation, both are the causes of endothelial dysfunction, in an endothelial cell culture model.MethodsStAR gene was introduced into primary rat aortic endothelial cells by adenovirus infection. Real-time PCR and Western blotting were performed to determine the relative genes and proteins expression level to elucidate the underlying mechanism. The free fatty acid and cholesterol quantification kits were used to detect total cellular free fatty acid and cholesterol. The levels of inflammatory factors and nitric oxide were determined by ELISA and classic Griess reagent methods respectively.ResultsWe successfully overexpressed StAR in primary rat aortic endothelial cells. Following StAR overexpression, mRNA levels of IL-1β, TNFα, IL6 and VCAM-1 and protein levels of IL-1β, , TNFα and IL-6 in culture supernatant were significantly decreased, which duing to blocke NFκB nuclear translocation and activation. Moreover, StAR overexpression attenuated the PA-induced reduction of nitric oxide bioavailability by protecting the bioactivity of pAkt/peNOS/NO pathway. Furthermore, the key genes involved in lipid metabolism were greatly reduced following StAR overexpression. In order to investigate the underlying mechanism, cerulenin and lovastatin, the inhibitor of fatty acid and cholesterol synthase, were added prior to PA treatment. The results showed that both cerulenin and lovastatin had a similar effect as StAR overexpression. On the other hand, the role of StAR was inhibited when siRNA was introduced to reduce StAR expression.ConclusionsOur results showed that StAR attenuated lipid synthesis and uptake as well as PA-induced inflammation and reduction in NO bioavailability in aortic endothelial cells. StAR can ameliorate endothelial dysfunction induced by PA via reducing the intracellular lipid levels.

Folate-bearing doxorubicin-loaded magnetic poly(N-isopropylacrylamide) microspheres as a new strategy for cancer therapy.

Doxorubicin is a classic anticancer agent. Recently, numerous strategies have been used to enhance efficacy of drug delivery for cancer treatment. For example, by modifying poly(N-isopropylacrylamide) microspheres, a nanocarrier, makes it more effective. Conjugation with folic acid increases specific targeted drug delivery towards folate receptor-bearing cancer cells to improve anticancer effectiveness by increasing the tissues local concentration of drugs. In the current studies, we synthesized folate-bearing, doxorubicin-loaded, magnetic, poly(N-isopropylacrylamide) microspheres (FDMPM) to treat breast cancer cells (human SKBR-3). We found efficiency of drug encapsulation very high (95%) at pH above 7.4. Reverse transcription-PCR showed that cancer cells highly expressed folate receptors. Confocal laser scanning microscopy and flow cytometry revealed internalization of the carrier by SKBR-3 in treatments with FDMPM, which was not the case with any other combination for drug delivery (MPM, FMPM, and DMPM). Similarly, SKBR-3 cell growth was inhibited more (assessed by methylthiazolyldiphenyl-tetrazolium bromide and trypan blue exclusion assays) when treated with FDMPM than with any other combinations. Current results confirm our predication and demonstrate that FDMPM has potential as a new targeting strategy in cancer therapy.

Extracellular 5'-nucleotidase (CD73) promotes human breast cancer cells growth through AKT/GSK-3β/β-catenin/cyclinD1 signaling pathway

To identify the role and to explore the mechanism of extracellular 5′‐nucleotidase (CD73) in human breast cancer growth, CD73 expression was measured firstly in breast cancer tissues and cell lines, and then interfered with or over‐expressed by recombinant lentivirus in cell lines. Impacts of CD73 on breast cancer cell proliferation and cell cycle were investigated with colony formation assay, CCK‐8 and flow cytometry. The relationship between CD73 and AKT/GSK‐3β/β‐catenin pathway was assessed with adenosine, adenosine 2A receptor antagonist (SCH‐58261), adenosine 2A receptor agonist (NECA), CD73 enzyme inhibitor (APCP) and Akt inhibitor (MK‐2206). Moreover, the effect of CD73 on breast cancer growth in vivo was examined with human breast cancer transplanting model of nude mice. The results showed that the expression of CD73 was high in breast cancer tissues and increased with advanced tumor grades and lympho‐node status. CD73 expression was higher in more malignant cells, and CD73 overexpression promoted breast cancer cell proliferation in both in vivo and in vitro. It activated AKT/GSK‐3β/β‐catenin/cyclinD1 signaling pathway through CD73 enzyme activity and other mechanism.

Effects of RNA interference-induced tryptase down-regulation in P815 cells on IL-6 and TNF-α release of endothelial cells

ObjectiveTo explore the effects of down-regulated tryptase expression in mast cells on the synthesis and release of interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) of vascular endothelial cells.MethodsTryptase-siRNA (small-interfering RNA) vector was constructed to inhibit tryptase expression in P815 cells. The medium of P815 cells treated by the tryptase-siRNA (RNAi-P815 group) or pure vector (P815 group) was collected and used to culture bEnd.3 cells. The messenger RNAs (mRNAs) of IL-6 and TNF-α in bEnd.3 cells and their protein levels in the medium were measured by reverse transcription polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA), respectively.ResultsIL-6 and TNF-α mRNAs in bEnd.3 cells cultured in RNAi-P815-conditioned medium decreased significantly compared to those in P815-conditioned medium. Consistently, IL-6 and TNF-α protein levels in the medium of bEnd.3 of RNAi-P815 group were lower than those of P815 group.ConclusionReduced tryptase expression significantly inhibited the synthesis and release of IL-6 and TNF-α in vascular endothelial cells. RNA interference targeting tryptase expression may be a new anti-inflammatory strategy for vascular diseases.