The characteristics of Hep-2 cell with multiple drug resistance induced by Taxol.

OBJECTIVE: To investigate the characteristics of Hep-2 cell with multidrug resistance (MDR) induced by Taxol. STUDY DESIGN: Hep-2 cells were exposed in stepwise escalating concentration of Taxol to develop the resistant cell line-Hep-2T. Cell cycle distribution, apoptosis, and rhodamine accumulation were studied through flow cytometry. The MDR1 and MRP1 genes were detected through real-time quantitative RT-PCR, and the corresponding proteins were detected through Western blotting. RESULTS: The drug resistance of Hep-2T cells to Taxol, doxorubicin, gemcitabine, 5-FU, and cisplatin all increased. The percentage of G0/G1 phase and the antiapoptosis ability increased significantly compared with Hep-2 cells. Both MDR1 and MRP1 also increased at gene and protein level, though MDR1 was more prominent. CONCLUSION: More emphasis should be laid on MDR1/Pgp, the non-Pgp substrate chemotherapeutic agents, and the changes of cell cycle distribution to prevent MDR induced by Taxol. SIGNIFICANCE: These findings may provide theoretical support for the reverse of MDR.     

Short interfering RNA-mediated gene silencing of vascular endothelial growth factor: effects on cellular proliferation in colon cancer cells

HYPOTHESIS: By using short interfering RNA (siRNA) to inhibit the in vitro expression of vascular endothelial growth factor (VEGF) A, we hope to further investigate the presence of an autocrine loop in colon cancer cells. We hypothesize that VEGF inhibition will result in decreased cellular proliferation. DESIGN: Human colon cancer cells were evaluated for the expression of VEGF and VEGF receptor 2 (VEGFR-2). In vitro assessments were then made of the ability of anti-VEGF siRNA to knock down expression of VEGF and the subsequent effect this decreased expression had on colon cancer cell proliferation. SETTING: Surgical oncology research laboratory. INTERVENTIONS: Human colon cancer cells from the RKO cell line were transfected with siRNA targeting the coding region of VEGF. MAIN OUTCOME MEASURES: Enzyme-linked immunosorbent assay, Northern blot analysis, and real-time quantitative polymerase chain reaction were performed to establish the ability of siRNA to decrease VEGF production. Proliferation assays were run on transfected and wild-type cells to establish concomitant decrease in VEGF expression and cellular proliferation. RESULTS: The RKO colon cancer cells expressed both VEGF and VEGFR-2. Those cells transfected with siRNA targeting VEGF showed a 94% knockdown in VEGF expression and a 67% decrease in cellular proliferation. CONCLUSION: Colon cancer cells expressing VEGF and VEGFR-2 may possess an autocrine growth pathway that can be effectively targeted using RNA interference as an antiangiogenic therapy.     

Prediction of Lymph Node Status in Superficial Esophageal Carcinoma

Background  Esophageal carcinoma is among the cancers with the worst prognosis. Real chances for cure depend on both early recognition and early treatment. The ability to predict lymph node involvement allows early curative treatment with less invasive approaches. Aims  To determine clinicohistopathological criteria correlated with lymph node involvement in patients with early esophageal cancer (T1) and to identify the best candidate patients for local endoscopic or less invasive surgical treatments. Methods  A total of 98 patients with pT1 esophageal cancer [67 with squamous cell carcinomas (SCC) and 31 with adenocarcinomas (ADK)] underwent Ivor–Lewis or McKeown esophagectomy in the period between 1980 and 2006 at our institution. Based on the depth of invasion, lesions were classified as m1, m2, or m3 if mucosal, and sm1, sm2, or sm3 if submucosal. Results  The rates of lymph node metastasis were 0% for the 27 mucosal carcinomas (T1m) and 28% for the 71 submucosal (T1sm) carcinomas (P < 0.001). Sm1 carcinomas were associated with a lower rate of lymph-node metastasis (8.3% versus 49 % sm2/3, P  = 0.003). As for histotype, the rates of lymph node metastasis for sm1 were 0% for ADK and 12.5% for SCC; for sm2/3 there were no significant differences. On multivariate analysis, depth of infiltration, lymphocytic infiltrate, angiolymphatic and neural invasion were significantly associated with lymph node involvement. Neural invasion was the single parameter with the greatest accuracy (82%); depth of infiltration and angiolymphatic invasion had 75% accuracy. Altogether these three parameters had an accuracy of 97%. Five-year survival rate was 56.7% overall: 77.7% for T1m and 53.3% for T1sm (P  = 0.048). Conclusions  The most important factors for predicting lymph node metastasis in early esophageal cancer are depth of tumor infiltration, angiolymphatic invasion, neural invasion and grade of lymphocytic infiltration. The best candidates for endoscopic therapy are tumors with high-grade lymphocytic infiltration, no angiolymphatic or neural invasion, mucosal infiltration or sm1 (only for ADK), and tumor <1 cm in size. For sm SCC and sm2/3 ADK the treatment of choice remains esophagectomy with standard lymphadenectomy.     

VEGF-A/VEGFR-2 Signaling Plays an Important Role for the Motility of Pancreas Cancer Cells

Background

Pancreatic cancer is one of the most lethal solid tumors. Vascular endothelial growth factor receptors (VEGFRs) are expressed not only by endothelial cells but also by pancreatic cancer cells. VEGFRs might play an important role for the development of pancreatic cancer cells. The purpose of this study was to evaluate the efficacy of VEGF/VEGFR-2??targeted therapy in pancreatic carcinoma.

Methods

Five pancreatic carcinoma cell lines were used. The expression level of VEGFR-2 of cancer cells was examined by RT-PCR and Western blot. The effects of VEGFs, bevacizumab as an anti-VEGF antibody, sunitinib as a tyrosine kinase inhibitor against VEGFRs, and VEGF-R2 siRNA on the motility activity of pancreatic cancer cells were examined by invasion assay and wound healing assay. The effect of VEGF, bevacizumab, and sunitinib on the phosphorylation of VEGFR-2 and downstream effecter molecules, MAPK and PI3K, was examined by western blot.

Results

Pancreatic cancer cell lines expressed VEGFR-2. VEGF-A significantly increased the motility of pancreas cancer cells, which was inhibited by VEGFR-2 siRNA. Conditioned medium from pancreas cancer cells significantly stimulated the motility of pancreas cancer cells. VEGF/VEGFR inhibitors, bevacizumab and sunitinib, significantly decreased the motility of pancreas cancer cells. VEGFR-2 phosphorylation level of pancreas cancer cells was increased by VEGF-A. Bevacizumab and sunitinib decreased the level of VEGFR-2 phosphorylation, p-ERK, and p-Akt expression. VEGF-A decreased zonula occludens (ZO-1) or ZO-2 expression in pancreas cancer cells.

Conclusions

VEGF-A/VEGFR-2 signaling plays an important role in inducing invasion and migration of pancreatic cancer cells.     

Epidermal growth factor modulates the expression of vascular endothelial growth factor in the human prostate

The growth and dissemination of tumors in the body has been associated with angiogenesis. Vascular endothelial growth factor (VEGF) is an angiogenic factor that stimulates endothelial cell growth and enhances vascular permeability. VEGF exerts its action by binding to specific cell surface receptors. Three receptors, VEGFR-1 (flt-1), VEGFR-2 (flk-1), and VEGFR-3 (flt-4) have been identified. Very little information on the coordinated expression of VEGF and its receptors in normal prostate, benign prostatic hyperplasia (BPH), and prostate carcinoma is available. Therefore, we examined the immunohistochemical localization of VEGF and its receptors in tissues derived from normal human prostate, BPH, and prostatic carcinoma. Immunostaining for VEGF was absent in the normal prostate. Epithelium lining the glands of prostate derived from patients with BPH exhibited strong immunostaining. The intensity of staining was relatively less in prostate carcinoma. It is interesting that VEGFR-1 and VEGFR-3 were strongly expressed in both stromal and epithelial tissues in normal prostate, BPH, and carcinoma. In comparison, VEGFR-2 was not localized to normal prostate and its expression in the stroma of BPH and epithelium of carcinoma was very weak. Because progression of prostate cancer is accompanied by altered expression of epidermal growth factor (EGF) and its receptor (EGFR) in malignant cells, we investigated the effect of EGF on VEGF gene expression by Northern blot analysis in 2 human prostate cancer cell lines that express EGFR. EGF greatly enhanced the expression of VEGF messenger RNA in DU145 and PC3 cell lines in a dose-dependent manner. The EGF induction of VEGF gene expression suggests a mechanism by which angiogenesis could be accelerated in BPH and prostate carcinoma.     

Vascular endothelial growth factor in chronic rat allograft nephropathy

BACKGROUND: Chronic allograft nephropathy (CAN) is a complex process of alloimmune responses and chronic inflammation leading to fibrosis and vasculopathy. We examined the biological role of proinflammatory vascular endothelial growth factor (VEGF) in a rat renal transplantation model of CAN. METHODS: Syngraft and allograft recipients were treated with a suboptimal dose of cyclosporine A which allows acute rejection and CAN to develop. Intragraft VEGF, VEGFR-1 and VEGFR-2 expressions were determined at 5, 14, 30 and 60 days. Protein tyrosine kinase inhibitor PTK787 was used to inhibit VEGFR activity. RESULTS: In nontransplanted kidneys and syngrafts, mild VEGF expression was observed in the glomeruli and tubuli. VEGFR-1 was detected in vascular structures and VEGFR-2 in glomeruli as well. In allografts, total intragraft VEGF expression and interstitial inflammatory cell VEGF expression were induced and correlated with the chronic allograft damage index (CADI) score. Total intragraft and interstitial inflammatory cell VEGFR-1 expression was induced and interstitial cell VEGFR-1 expression correlated with the CADI score. Blocking VEGF receptor signaling with PTK787 significantly reduced fibrosis and the CADI score, but did not affect early inflammation or VEGF, VEGFR-1, VEGFR-2 expressions compared to vehicle treated group. CONCLUSIONS: Interstitial inflammatory cell VEGF and VEGFR-1 expressions are induced during the development of CAN. Increased VEGF activity may enhance the alloimmune induced inflammatory responses leading to fibrosis and CAN.     

Inhibition of VEGFR-2 Reverses Type 1 Diabetes in NOD Mice by Abrogating Insulitis and Restoring Islet Function

The dysregulation of receptor tyrosine kinases (RTKs) in multiple cell types during chronic inflammation is indicative of their pathogenic role in autoimmune diseases. Among the many RTKs, vascular endothelial growth factor receptor (VEGFR) stands out for its multiple effects on immunity, vascularization, and cell migration. Herein, we examined whether VEGFR participated in the pathogenesis of type 1 diabetes (T1D) in nonobese diabetic (NOD) mice. We found that RTK inhibitors (RTKIs) and VEGF or VEGFR-2 antibodies reversed diabetes when administered at the onset of hyperglycemia. Increased VEGF expression promoted islet vascular remodeling in NOD mice, and inhibition of VEGFR activity with RTKIs abrogated the increase in islet vascularity, impairing T-cell migration into the islet and improving glucose control. Metabolic studies confirmed that RTKIs worked by preserving islet function, as treated mice had improved glucose tolerance without affecting insulin sensitivity. Finally, examination of human pancreata from patients with T1D revealed that VEGFR-2 was confined to the islet vascularity, which was increased in inflamed islets. Collectively, this work reveals a previously unappreciated role for VEGFR-2 signaling in the pathogenesis of T1D by controlling T-cell accessibility to the pancreatic islets and highlights a novel application of VEGFR-2 antagonists for the therapeutic treatment of T1D.In type 1 diabetes (T1D), genetic and environmental risk factors lead to immune dysregulation, provoking an autoimmune response directed toward insulin-producing β-cells of the islets of Langerhans. Previous investigations have estimated that β-cells or islets in nonobese diabetic (NOD) mice and humans are diminished to 10–30% of their initial mass (1,2), and the residual islets are largely dysfunctional when hyperglycemia is first detected (1,2). However, low levels of C-peptide can be detected in T1D patients as far out as 1–2 years postdiagnosis, indicating a window of opportunity for therapies that can restore or preserve islet mass and function (3).Multitarget receptor tyrosine kinase inhibitors (RTKIs), such as sunitinib, were originally designed to target malignant tumors that express dysregulated tyrosine kinases, including platelet-derived growth factor (PDGF)-R, c-FMS, or c-Kit. However, these inhibitors also target vascular endothelial growth factor (VEGF) receptors (VEGFRs), which are elevated in the parenchyma and tissue vasculature in many tumor microenvironments and during chronic inflammation. VEGF regulates vasculogenesis and angiogenesis largely through activation of VEGFR-2 (4). In addition to stimulating endothelial cell mitogenesis and cell migration, VEGF also has effects on a limited number of other cell types, including stimulation of monocyte/macrophage migration. Studies of transgenic mice lacking VEGFR-1 (5) or that express VEGFR-1 with a “dead” kinase domain (6) reveal that VEGFR-1 functions as a negative regulator of vasculogenesis and angiogenesis. Similarly, VEGFR-2 deficiency is embryonically lethal in mice but is attributed to a nonfunctional and underdeveloped vascular system (7). The phenotypes of VEGFR-1 and VEGFR-2–null mice indicate that, although VEGF-A has limited function through VEGFR-1, the vascular remodeling functions of VEGF-A are largely mediated through the activation of VEGFR-2.Tyrosine kinase inhibitors (TKIs) have shown efficacy in mouse models of muscular dystrophy (8), multiple sclerosis (9), rheumatoid arthritis (10–12), and psoriasis (13). TKI can prevent and reverse diabetes in NOD mice (14–16). Imatinib, which predominantly targets c-abl and PDGF, reversed diabetes in NOD mice (14), but other RTKIs with distinct inhibitory profiles (e.g., sunitinib) were even more effective, suggesting that the precise constellations of TK targets were critical for maximum efficacy. In this regard, the VEGF-A/VEGFR-2 pathway, a key target of sunitinib, stands out as a key kinase regulating the pathogenesis of several of these inflammatory disorders (17–19). Intriguingly, VEGF serum levels are elevated in T1D patients compared with healthy controls and positively correlate with increased HbA_1c levels (20).In this study, we determined whether VEGFR-2 might be involved in the pathogenesis of T1D and tested the therapeutic efficacy of VEGFR-2 inhibition in the NOD mouse model of T1D. We report that inhibition of VEGFR-2 by RTKIs or blocking antibodies rapidly reversed diabetes and maintains euglycemia with continued drug administration. Reversal of diabetes was attributed to an abrogation of vascular remodeling in the pancreatic islets, which impairs T-cell trafficking and the severity of insulitis, ultimately improving glucose tolerance. Histological analysis of human and mouse pancreata revealed a positive correlation between the severity of insulitis and islet vascularity, implicating inflammation as a major driving force in the vascular remodeling observed in the islets. Collectively, our findings suggest that VEGF/VEGFR-2 signaling serves a critical gatekeeper function by controlling essential remodeling of the vasculature that is necessary for T cells to gain access to tissues.     

苦参碱对喉鳞癌细胞株Hep-2侵袭转移的影响

目的:研究不同浓度苦参碱对喉鳞癌细胞株Hep-2侵袭和转移的影响及其作用机制。方法:Hep-2细胞体外培养,经0g/L、0.1g/L、0.2g/L和0.3g/L苦参碱分别处理1h、8h及48h,细胞黏附实验检测细胞黏附力,细胞迁移实验检测细胞运动力,细胞侵袭实验检测细胞侵袭力,RT-PCR法检测Hep-2细胞MMP-2和MMP-9mRNA的表达。结果:不同浓度苦参碱与对照组比较,苦参碱能有效抑制Hep-2细胞的黏附力、运动力和侵袭力(P<0.01),且能下调Hep-2细胞MMP-2和MMP-9mRNA的表达(P<0.01)。结论:苦参碱能抑制Hep-2细胞的浸润转移能力,其机制可能与下调MMP-2和MMP-9mRNA的表达使Hep-2细胞的黏附力、运动力和侵袭力下降有关。     

Minimally invasive colon resection for malignant colonic conditions is associated with a transient early increase in plasma sVEGFR1 and a decrease in sVEGFR2 levels after surgery

Introduction  

Plasma VEGF levels increase after minimally invasive colorectal resection (MICR) and remain elevated for 2–4 weeks. VEGF induces physiologic and pathologic angiogenesis by binding to endothelial cell (EC) bound VEGF-Receptor-1 (VEGFR1) and VEGFR2. Soluble forms of these receptors sequester plasma VEGF, decreasing the amount available to bind to EC-bound receptors. Ramifications of surgery-related plasma VEGF changes partially depend on plasma levels of sVEGFR1 and sVEGFR2. This study assessed perioperative sVEGFR1 and sVEGFR2 levels after MICR in patients with colorectal cancer.     

小干扰RNA沉默血管内皮生长因子对ACHN肾癌细胞黏附、侵袭及迁移的影响

目的 观察小干扰RNA (siRNA)沉默血管内皮生长因子(VEGF)对ACHN肾细胞癌细胞生物学行为的影响.方法 化学合成针对VEGF的小干扰RNA,实验分4组,转染后收集细胞,通过蛋白印迹方法检测VEGF的表达,噻唑蓝(MTT)比色法、细胞黏附实验、划痕实验及Transwell法测定细胞的增殖、黏附、迁移及侵袭能力.结果 siRNA 1～2组VEGF表达水平明显低于空白对照组及阴性对照组;在24、48、72 h,siRNA 1～2的增殖抑制率均高于空白对照组及阴性对照组(P＜0.05),其中以siRNA2组最为显著;与空白对照组比较,siRNA 1～2组的细胞黏附数量明显下降[(81.5±3.1)％比(40.5±2.6)％、P＜0.05,(81.5±3.1)％比(22.5±2.4)％、P＜0.05],其中以siRNA2组最为明显;siRNA1～2组的细胞迁移数量明显下降(162±9比81±5,P＜0.05;162±9比38±4,P＜0.05);siRNA1～2组细胞侵袭能力明显下降(P＜0.05),且siRNA 2组的细胞侵袭能力明显低于siRNA 1组(P＜0.05).结论 VEGF基因在肾细胞癌细胞黏附、迁移和侵袭中发挥着重要作用;以靶向VEGF的siRNA转染肾细胞癌细胞,可抑制肾细胞癌细胞黏附、迁移和侵袭能力.     

Function of the vascular endothelial growth factor receptors Flt-1 and Flk-1/KDR in the alloimmune response in vivo

BACKGROUND: We have recently reported that vascular endothelial growth factor (VEGF) functions as a proinflammatory cytokine to regulate the trafficking of leukocytes into allografts in the early posttransplant period. VEGF binds two major VEGF receptors: VEGFR-1 (flt-1) and VEGFR-2 (flk-1/KDR). Here, we wished to investigate the expression and function of VEGF receptors in the process of acute allograft rejection in vivo. METHODS: We performed fully MHC-mismatched C57BL/6 (H-2b) into BALB/c (H-2d) vascularized heterotopic murine cardiac transplants and we examined the expression of VEGF and VEGF receptors by immunohistochemistry during acute allograft rejection. Next, we treated mice with specific neutralizing monoclonal antibodies against murine VEGFR-1 and VEGFR-2 and examined their effect on the development of acute allograft rejection by histology and by analysis of graft survival. The intragraft expression of cytokines and chemokines were also evaluated by quantitative real-time PCR analysis. RESULTS: The expression of VEGF, VEGFR-1 and VEGFR-2 were significantly up-regulated during allograft rejection as compared to isografts. Administration of either anti-VEGFR-1 or anti-VEGFR-2 alone failed to inhibit allograft rejection. However, coadministration of both antibodies together inhibited leukocyte infiltration of allografts and prolonged allograft survival. Furthermore, the effect of VEGFR blockade was associated with the downregulation of intragraft cytokine and chemokine expression. CONCLUSIONS: Our data suggest that VEGF-VEGFR interactions function in the alloimmune response in vivo. Targeting VEGFRs may represent a novel therapy to protect allografts following clinical transplantation.     

Minimally invasive colon resection is associated with a transient increase in plasma sVEGFR1 levels and a decrease in sVEGFR2 levels during the early postoperative period

Introduction  Plasma vascular endothelial growth factor (VEGF) levels are elevated for 2–4 weeks after minimally invasive colorectal resection (MICR). VEGF induces wound and tumor angiogenesis by binding to endothelial cell (EC)-bound VEGF-receptor 1 (VEGFR1) and VEGFR2. Soluble receptors (sVEGFR1, sVEGFR2) sequester VEGF in the blood and decrease VEGF’s proangiogenic effect. The importance of the MICR-related VEGF changes depends on the effect of surgical procedures on sVEGFR1 and sVEGFR2; this study assessed levels of these proteins after MICR for benign indications. Methods  Blood samples were taken (n = 39) preoperatively (preop) and on postoperative days (POD) 1 and 3; in most cases a fourth sample was drawn between POD 7 and 30. sVEGFR1 and sVEGFR2 levels were measured via enzyme-linked immunosorbent assay (ELISA), which detects free and VEGF bound soluble receptor. Late samples were bundled into POD 7–13 and POD 14–30 time points. Results are reported as mean and standard deviation. The data was assessed with paired-samples t-test. Results  Preop, mean plasma sVEGFR2 level (9,203.7 ± 1,934.3 pg/ml) was significantly higher than the sVEGFR1 value (132.5 ± 126.2 pg/ml). sVEGFR2 levels were significantly lower on POD 1 (6,957.8 ± 1,947.7 pg/ml,) and POD 3 (7,085.6 ± 2,000.2 pg/ml), whereas sVEGFR1 levels were significantly higher on POD 1 (220.0 ± 132.8 pg/ml) and POD 3 (182.7 ± 102.1 pg/ml) versus preop results. No differences were found on POD 7–13 or 14–30. Conclusions  sVEGFR2 values decreased and sVEGFR1 levels increased early after MICR; due to its much higher baseline, the sVEGFR2 changes dominate. The net result is less VEGF bound to soluble receptor and more free plasma VEGF.     

Prognostic Significance of Vascular Endothelial Growth Factor D in Gastric Carcinoma

The angiogenic factor called vascular endothelial growth factor (VEGF)-D is a ligand for VEGF receptor-2 (VEGFR-2/KDR) and receptor-3 (VEGFR-3/Flt-4). It is implicated in the development of lymphatic vessels and promotion of lymphatic metastasis. The purpose of this study was to investigate the prognostic significance of VEGF-D expression in patients with gastric carcinoma. We assessed the expression of VEGF-D in gastric carcinoma by immunohistochemistry on 143 consecutive patients’ stored sections and evaluated the lymphatic vessel count (LVC) in tumors using the novel selective lymphatic endothelium marker D2-40. VEGF-D expression was observed in 55 (39%) tumor sections. The expression of VEGF-D correlated significantly with tumor size, T of the TNM classification, lymphatic and venous system invasion, LVC, lymph node metastasis, M of TNM, and pTNM stage. Multivariate analysis indicated that VEGF-D expression was an independent prognostic factor for both relapse-free survival (RFS) and overall survival (OS). Our data indicate the involvement of VEGF-D in tumor progression via lymphoangiogenic pathways. Practically, VEGF-D expression can be useful for predicting RFS and OS in patients with gastric carcinoma.     

Bilaterally increased VEGF-levels in muscles during experimental unilateral callus distraction.

Angiogenesis is essential for wound healing and proliferative processes such as bone formation and repair. Since increased expression of the vascular endothelial growth factor (VEGF) stimulates bone formation, it can be hypothesized that surgical procedures leading to a systemic increase of VEGF for instance during wound healing, influence enchondral ossification processes and might be responsible for observed growth phenomena during callus distraction. To study the mechanisms of angiogenesis in soft tissue during unilateral callus distraction, lengthening of the right tibia was performed in 12 beagles. After osteotomy, application of a ring fixator and after five latency days, distraction was started for 25 days. A control group of four additional beagles underwent no surgical procedure. Subsequent to the distraction period (Group A), muscle samples from six beagles were taken from the distracted side (ds) and the contralateral non-distracted side (n-ds), six beagles underwent an additional consolidation period of 25 days (Group B). Samples were analyzed for VEGF, VEGFR-1 and VEGFR-2 mRNA expression using real-time PCR and protein expression using Western Blot analysis. Muscles from both extremities showed significantly increased expression of VEGF and its cognate receptors VEGFR-1/2. Expression decreased significantly after the consolidation period, whereby the level at the non-distracted side decreased more than the level at the distracted side. Interestingly VEGF and VEGFR-1 levels at the non-distracted side were significantly higher than at the distracted side. In contrast VEGFR-2, the receptor that mediates endothelial cell proliferation, showed higher levels at the distracted than at the non-distracted side. These findings indicate that callus distraction results not only in locally increased expression of VEGF and its receptors, but leads also to increased VEGF and VEGFR-1/2 levels at distant sides and might therefore be responsible for the observed growth phenomena during callus distraction.     

Vascular endothelial growth factor stimulates a novel calcium-signaling pathway in vascular smooth muscle cells

BACKGROUND: Vascular endothelial growth factor (VEGF) is a potent vascular mitogen that selectively stimulates vascular smooth muscle cell (VSMC) migration through an unknown mechanism while having no effect on VSMC proliferation. It is known that VSMC migration and proliferation are dependent on the second messenger Ca2+ and, in particular, mitogen-stimulated Ca2+ influx. We hypothesized that the selective effect of VEGF on VSMC migration versus proliferation was a result of differential VEGF-stimulated Ca2+ signaling pathways. METHODS: Primary cultured human aortic smooth muscle cells (VSMCs) were grown to subconfluency and assigned to the following experimental groups: no stimulation, stimulation with platelet-derived growth factor-BB (PDGF-BB) (20 ng/mL) as positive control, and stimulation with VEGF165 (40 ng/mL). Total increase in [Ca2+]cyt and intracellular calcium release was quantified with the use of a fura-2 fluorescence assay. Assays for the following receptors VEGFR-1 (Flt-1), VEGFR-2 (KDR/Flk-1) and PDGFR-beta were performed by immunoprecipitation, while PLCgamma1, Akt 1/2, and phospholamban B phosphorylation were assessed with Western immunoblotting. RESULTS: VSMCs stimulated with VEGF165 exhibited no intracellular Ca2+ release, compared with a 75 +/- 30 nmol/L intracellular calcium release after PDGF-BB stimulation, (P < .02) VEGF165-stimulated VSMCs in Ca2+-containing media exhibited 192 +/- 26 nmol/L increase in [Ca2+]cyt, compared with 354 +/- 54 nmol/L increase after PDGF-BB stimulation (P < .02). VEGF165 did not phosphorylate PLCgamma1 after 1, 5, or 10 minutes of treatment. VEGF165 treatment did not result in PI3-K/Akt activation at 1-, 5-, or 10-minute time points. Calmodulin-dependent kinase II (CaMKII) was activated by both VEGF165 and PDGF-BB after 1 and 5 minutes of stimulation. The presence of the receptors VEGFR-1, VEGFR-2, and PDGFR-beta was confirmed in all experimental groups. CONCLUSIONS: VEGF induces extracellular calcium influx but no intracellular calcium release in VSMCs. This lack of intracellular Ca2+ release stems from the inability of VEGF165 to activate the PLCgamma1 cascade and IP3 receptor-mediated Ca2+ release. The lack of PI3-K/Akt activation at these time points indicates a novel extracellular Ca2+ influx pathway sufficient to activate CaMKII. A paradigm relating extracellular Ca2+ influx to CaMKII activation and migration is suggested and may account for the selective effects of VEGF on VSMC migration.     

MDR1 siRNA对胰腺癌细胞株BxPC-3耐药性影响的实验研究

目的：观察阻断多药耐药基因1（MDR1）表达后胰腺癌细胞对化疗药物敏感性的变化,探索提高胰腺癌化疗疗效的新方法。方法：采用RNA干扰技术．构建MDR1 siRNA重组质粒．脂质体介导转染人胰腺癌细胞株BxPC-3,并筛选稳定转染细胞克隆,RT-PCR和Western印迹法检测MDR1 mRNA和蛋白的表达变化。将细胞接种于裸鼠,观察移植瘤对化疗药物吉西他滨敏感性的变化。结果：转染MDR1 siRNA质粒后胰腺癌细胞株BxPC-3 MDR1 mRNA与蛋白表达水平明显降低。体内实验结果显示,将转染前后的细胞接种于裸鼠,转染组移植瘤对化疗药物吉西他滨更为敏感（P〈0．05）。结论：通过RNA干扰技术,可在转录和翻译水平降低MDR1在胰腺癌细胞株BxPC-3中的表达,并能提高细胞对化疗药物的敏感性。     

siRNA沉默HYAL1基因表达对人乳腺癌细胞侵袭力的影响

目的研究RNA干扰对透明质酸酶基因HYAL1的表达以及对人乳腺癌细胞侵袭力的影响。方法体外化学合成HYAL1序列特异性双链RNA（dsRNA），在脂质体（SiPORT Lipid）的介导下转染人人乳腺癌细胞株MDA-MB-231、MDA—MB-453S、ZR-75和ZR-75-30。荧光共聚焦显微镜下观察转染效率，RT—PCR分析HYAL1 mRNA的表达，体外实验测定肿瘤细胞穿透matrigel的能力。结果4种乳腺癌细胞株的HYAL1基因的表达均被HYAL1-siRNA有效封闭，HYAL1 mRNA相对水平明显降低（P〈0．05）。转染48h后4种人乳腺癌细胞的侵袭力均明显降低（P〈0．01）。结论HYAL1-siRNA能有效抑制人乳腺癌细胞株HYAL1基因的表达，降低人乳腺癌细胞的侵袭力。