Fas ligand expression in colon cancer： A possible mechanism of tumor immune privilege

AIM: To detect the expression of Fas ligand (FasL) in colon cancer tissues and cell lines and analyze the function of FasL-expressing colon cancer cells in inducing Fas-sensitive T lymphocyte apoptosis. METHODS: Ninety surgically resected colon cancer tissues and 15 hepatic metastasis specimens were investigated by immunohistochemical method with normal colon mucosa and colon adenoma as control. The relationship between FasL expression and pathologic features was also analyzed. FasL expression of 4 colon cancer cell lines, SW620, Lovo, LS-174T and SW1116, were detected by Western blotting assay. The function of FasL expressed on colon cancer cells was determined by coculture assay with Jurkat T lymphocytes, the apoptotic rate of which was detected by flow cytometry assay. RESULTS: Fifty-six (62.22%) cases of all the 90 colon cancer tissues and all (100%) the liver metastasis specimens expressed FasL, significantly higher than normal colon mucosa and colonic adenoma. Higher expression of FasL was found in more advanced stage of colon cancer and in cancer tissues with lymphatic or hepatic metastasis. All the colon cancer cell lines were found to express FasL. After coculture with the SW1116 cells for 24 h with an effector: target ratio 10:1, the rate of apoptosis of Jurkat cells rose from 1.9% to 21.0%. CONCLUSION: The expression of FasL is upregulated in colon cancer and the functionally expressed FasL can induce apoptosis of Fas-expressing T lymphocytes.     

Synergistic antitumor effect of TRATL and doxorubicin on colon cancer cell line SW480

AIM: TRAIL (tumor necrosis factor-related apoptosisinducing ligand) has been reported to specifically induce apoptosis of cancer cells although only a small percentage of cell lines were sensitive to it. Cell lines not responding to TRAIL in vitro were said to be more prone to apoptosis when TRAIL was combined with another anticancer agent.Generally, factors affecting drug-sensitivity involve many apoptosis-related proteins, including p53. The expression of wild-type p53 gene was proposed as an important premise for tumor cells responding to chemotherapy. The present study was to investigate the cell killing action of TRAIL on colon cancer cell line SW480, its synergistic effect with doxorubicin, and the possible mechanisms. METHODS: SW480 cells were cultured in the regular condition and incubated with different levels of agents.Morphologic changes in these cells after treatment were observed under phase-contrast microscope and cytotoxicity by TRAIL alone and in combination with doxorubicin was quantified by a 1-day microculture tetrazolium dye (MTT)assay. In addition, flow cytometry assay (FCM) and transmission electron microscopy were used to detectapoptosis among these cells. Variation of p53 protein level among different groups according to concentrations of agents was measured by Western blot assay.RESULTS: (1) SW480 cells were not sensitive to TRAIL,with IC50＞1 mg@L1 and dose-independent cytotoxicity. (2)SW480 cells were sensitive to doxorubicin at a certain degree,with dose-dependent cytotoxicity and IC50=65.25+3.48μmol@L-1. (3) TRAIL could synergize with doxorubicin to kill SW480 cells effectively, which was represented by the boosted killing effect of doxorubicin on theses cells. IC50 of doxorubicin against SW480 cells sharply reduced when it was combined with TRAIL. (4) Subtoxic TRAIL (100 μg.L-1),combined with subtoxic doxorubicin (0.86 μmol@L1), could kill SW480 cells sufficiently. Cytotoxicity by MTT assay arrived at 80.12+2.67%, which was significantly higher than that by TRAIL or doxorubicin alone, with P=0.006 and 0.003 respectively. This killing effect was partly due to apoptosis. It was proved by large amounts of apoptotic cells under phase-contrast microscopy, cell apoptosis rate of 76.82±1.93 % by FCM assay and typical apoptotic morphology observed through transmission electron microscopy. Increase of apoptosis after combined treatment had no relation with protein level of p53 (P＞0.05). CONCLUSION: SW480 cells are not sensitive to TRAIL, but TRAIL can synergize with lower concentration of doxorubicin to induce apoptosis effectively. The status of p53 protein i snot involved in the mechanism of synergistic apoptosis. It suggests the potential therapeutic applicability of the combination of TRAIL with doxorubicin against colon cancers.     

Synergistic antitumor effect of TRAIL and doxorubicin on colon cancer cell line SW480

AIM: TRAIL (tumor necrosis factor-related apoptosis-inducing ligand) has been reported to specifically induce apoptosis of cancer cells although only a small percentage of cell lines were sensitive to it. Cell lines not responding to TRAIL in vitro were said to be more prone to apoptosis when TRAIL was combined with another anticancer agent.Generally, factors affecting drug-sensitivity involve many apoptosis-related proteins, including p53. The expression of wild-type p53 gene was proposed as an important premise for tumor cells responding to chemotherapy. The present study was to investigate the cell killing action of TRAIL on colon cancer cell line SW480, its synergistic effect with doxorubicin, and the possible mechanisms.METHODS: SW480 cells were cultured in the regular condition and incubated with different levels of agents.Morphologic changes in these cells after treatment were observed under phase-contrast microscope and cytotoxicity by TRAIL alone and in combination with doxorubicin was quantified by a 1-day microculture tetrazolium dye (MTT) assay. In addition, flow cytometry assay (FCM) and transmission electron microscopy were used to detect apoptosis among these cells. Variation of p53 protein level among different groups according to concentrations of agents was measured by Western blot assay.RESULTS: (1) SW480 cells were not sensitive to TRAIL,with IC50>l mg·L^1 and dose-independent cytotoxicity. (2)SW480 cells were sensitive to doxorubicin at a certain degree,with dose-dependent cytotoxicity and IC50=65.25±3.48μmol·L^-1. (3) TRAIL could synergize with doxorubicin to kill SW480 cells effectively, which was represented by the boosted killing effect of doxorubicin on theses cells. IC50 of doxorubicin against SW480 cells sharply reduced when it was combined with TRAIL. (4) Subtoxic TRAIL (100 μg·L^-1),combined with subtoxic doxorubicin (0.86 μmol·L^-1), could kill SW480 cells sufficiently. Cytotoxicity by MTT assay arrived at 80.12±2.67 %, which was significantly higher than that by TRAIL or doxorubicin alone, with P=0.006 and 0.003 respectively. This killing effect was partly due to apoptosis. It was proved by large amounts of apoptotic cells under phase-contrast microscopy, cell apoptosis rate of 76.82±1.93 % by FCM assay and typical apoptotic morphology observed through transmission electron microscopy. Increase of apoptosis after combined treatment had no relation with protein level of p53 (p>0.05).CONCLUSION: SW480 cells are not sensitive to TRAIL, but TRAIL can synergize with lower concentra~on of doxorubidn to induce apoptosis effectively. The status of p53 protein is not involved in the mechanism of synergistic apoptosis. It suggests the potential therapeutic applicability of the combination of TRAIL with doxorubidn against colon cancers.     

Apoptosis induction with polo-like kinase-1 antisense phosphorothioate oligodeoxynucleotide of colon cancer cell line SW480

AIM:To investigate the effects of polo-like kinase-1 (PLKl) antisense phosphorothioate oligodeoxynudeotide (ASODN) on apoptosis and cell cycle of human colon cancer cell line SW480. METHODS:After SW480 colon cancer cells were transfected with PLKl ASODN, Northern and Western blot analyses were used to examine PLKl gene expression in cancer cells. We studied apoptosis using terminal uridine deoxynudeotidyl nick end labeling. Apoptosis and cell cycle of SW480 cells were examined by fluorescence-activated cell sorter scan. RESULTS:The levels of PLKl mRNA and protein were greatly inhibited by PLKl ASODN in SW480 cancer cells transfected with PLKl ASODN. Apoptosis index (AI) induced PLKl ASODN in a time-and dose-dependent manner. Results from FLM showed that sub-2N DNA content of transfected cancer cells was significantly increased and arrested at G_2/M compared with control groups. CONCLUSION:PLKl ASODN can induce apoptosis of human colon cancer cell line SW480.     

Molecular mechanisms of denbinobin-induced anti-tumorigenesis effect in colon cancer cells

AIM: To explore both the in vitro and in vivo effects of denbinobin against colon cancer cells and clarify its underlying signal pathways. METHODS: We used COLO 205 cancer cell lines and nude mice xenograft model to study the in vitro and in vivo anti-cancer effects of denbinobin. RESULTS: Denbinobin at concentration of 10-20 μmol/L dose-dependently suppressed COLO 205 cell proliferation by MTT test. Flow cytometry analysis and DNA fragmentation assay revealed that 10-20 μmol/L denbinobin treatment induced COLO 205 cells apoptosis. Western blot analysis showed that caspases 3,8,9 and Bid protein were activated by denbinobin treatment to COLO 205 cells accompanied with cytochrome c and apoptosis-inducing factor (AIF) translocation. Pretreatment of MEK 1 inhibitor (U10126), but not p38 inhibitor (SB203580) and JNK inhibitor (SP600125), reversed denbinobin-induced caspase 8, 9 and Bid activation in COLO 205 cells suggesting that extracellular signal-regulated kinase were involved in the denbinobin-induced apoptosis in COLO 205 cells. Significant regression of tumor up to 68% was further demonstrated in vivo by treating nude mice bearing COLO 205 tumor xenografts with denbinobin 50 mg/kg intraperitoneally. CONCLUSION: Our findings suggest that denbinobin could inhibit colon cancer growth both in vitro and in vivo. Activation of extrinsic and intrinsic apoptotic pathways and AIF were involved in the denbinobin-induced COLO 205 cell apoptosis.     

Less cytotoxicity to combination therapy of 5—fluorouracil and cisplatin than5—fluorouracil alone in human colon cancer cell lines

AIM：Our previous studies showed increased sensitivity to 5-FU in colon cancer cell lines with microsatellite instability,and considered that mutations of TGFβ-RⅡ,IGFⅡR,RIZgene might enhance the potentials of cell growth and proliferation,which increased the sensitivity to 5-FU.Here we compared the distribution of cell cycle and P53 status between two human colon cancer cell lines with P53status between two human colon cancer cell lines with different sensitivity to5-FU.Because mechanistic differences exist between 5-FUand CDDP,we also analyzed the efficacy of CDDPand combination therapy on two human colon cancer cell lines.METHODS:We compared the sensitivity to CDDP of these two cell lines by MTT assay,Distributon of cell cycle under treatment of5-FU,cddp alone or both was analyzed by Flow Cytometry,and expression of P53was detected by immunocytochemical staining.RESULTS:SW480 cells were more sensitive to CDDP than LoVo cells at the concentrations above 16μmol/l(Ratio of absorption is 0.64and0.79at16μmol/l.respectively;P<0.010,Efficacy of combination therapy was conversely lower than that of single-therapy of 5-FU(Ratio of absorption in LoVo+5-FU,SW480+5-FU,LoVo+5-FU+CDDPand SW480+5-FU+CDDPis0.53,0.54,0.72,0.78,respectively;P<0.01).LoVo cells were negative whereas wsw480 cells positive inP53expression,5-FU induced G1-phase arrest in both cell lines,butLoVo cells peaked 24hours earlier than SW480cells,and 48hours earlier for an apparent hypodiploidDNA.However,CDDP showedthe contrary,inducingS-phase arrest,andSW480cells peaking 36hours earlier,Both cell lines showed hypodipliod nuclei 48hours after CDDP treatment.Percentage of cells in G1-phase and 5-phase dominated alternatively under conbination therapy in both cell lines.CONCLUSION:There results suggest that colon cancer cells with microsatellite instability are mor sensitive to 5-FU,whereas more resistant to CDDP.Combination therapy of5-FU and CDDPshows fewer efficacies than5-FU single-therapy,although it can render a cell cycle arrest.P53may be involoved in the shift of G1-phase to S-phase,but inessentially.     

Gallic acid induced apoptotic events in HCT-15 colon cancer cells

AIM: To investigate the inhibitory action of diet-derived phenolic compound gallic acid(GA) against HCT-15 colon cancer cells.METHODS: The antiproliferative effect of GA against colon cancer cells was determined by performing thiazolyl blue tetrazolium bromide(MTT) assay. The colony forming ability of GA treated colon cancer cells was evaluated using the colony forming assay. The cell cycle changes induced by GA in HCT-15 cells were analyzed by propidium iodide staining. Levels of reactive oxygen species(ROS) and mitochondrial membrane potential of HCT-15 exposed to GA was assessed using 2',7'-dichlorfluorescein-diacetate and rhodamine-123 respectively, with the help of flow cytometry. Morphological changes caused by GA treatment in the colon cancer cells were identified by scanning electron microscope and photomicrograph examination. Apoptosis was confirmed using flow cytometric analysis of GA treated HCT-15 cells after staining with Yo-Pro-1.RESULTS: MTT assay results illustrated that GA has an inhibitory effect on HCT-15 cells with IC50 value of 740 μmol/L. A time-dependent inhibition of colony formation was evident with GA treatment. Cell cycle arrest was evident from the accumulation of GA treated HCT-15 cells at sub-G1 phase(0.98 ± 1.03 vs 58.01 ± 2.05)with increasing exposure time. Flow cytometric analysis of GA treated HCT-15 cells depicted early events associated with apoptosis like lipid layer breakage and fall in mitochondrial membrane potential apart from an increase in the generation of ROS which were in a time dependent manner. SEM and photomicrograph images of the GA-treated cells displayed membrane blebbing and cell shrinking characteristics of apoptosis. Further apoptosis confirmation by Yo-Pro-1 staining also showed the time-dependent increase of apoptotic cells after treatment.CONCLUSION: These results show that GA induced ROS dependent apoptosis and inhibited the growth of colon cancer cells.     

Effect of antisense oligodeoxynucleotide of telomerase RNA on telomerase activity and cell apoptosis in human colon cancer

AIM:To explore the effect of antisense oligodeoxynucleotide(As-ODN) of telomerase RNA on telomerase activity and cellapoptosis in human colon cancer.METHODS:As-ODN was transfected into SW480 cells byliposomal trdnsfection reagent,Telomerase activity of SW480cells was examined by telomeric repeat amplification protocol(TRAP) and enzyme-linked immunosorbent assay (ELISA),Apoptosis was analyzed by morphology and flow cytometry,RESULTS:The telornerase activity in SW480 cells transfectedwith 1,0 μmol/L of As-ODN for 2-5 days,was significantlydecreased in a time-dependent manner,and the cellsunderwent apoptosis.The missense ODN (Ms-ODN) andthe control group transfected with SW480 cells did not showthese changes.CONCLUSION:As-ODN can spedfically inhibit the telomeraseactivity of SW480 cells and induce apoptosis.     

Inhibitory effect of caffeic acid phenethyl ester on the growth of SW480 colorectal tumor cells involvesβ-catenin associated signaling pathway down-regulation

AIM: To study the anti-tumor effect of caffeic acid phenethyl ester (CAPE) and the influence of CAPE onβ-catenin associated signaling pathway in SW480 colorectal cancer (CRC) cells. METHODS: SW480 cells were treated with CAPE at serial concentrations. The proliferative status of cells was measured by methabenzthiazuron (MTT) assay. Cell cycle and cell apoptosis were analyzed using flow cytometry (FCM). Western blotting assay was used to evaluate the protein level ofβ-catenin, c-myc and cyclinDl. p-catenin localization was determined by indirect immunofluorescence. RESULTS: CAPE displayed a strong inhibitory effect in a significant dose- and time-dependent manner on SW480 cell growth. FCM analysis showed that the ratio of G0 /G1 phase cells increased, S phase ratio decreased and apoptosis rate increased after SW480 cells were exposed to CAPE for 24 h. Pretreatment of SW480 cells with CAPE significantly suppressed p-catenin, c-myc and cyclinD1 protein expression. CAPE treatment was associated with decreased accumulation ofβ-catenin protein in nucleus and cytoplasm, and concurrently increased its accumulation on the surface of cell membrane. CONCLUSION: CAPE can inhibit SW480 cell proliferation by inducing cell cycle arrest and apoptosis. Decreased p-catenin and the associated signaling pathway target gene expression may mediate the anti-tumor effects of CAPE.     

Anti-proliferative effect of interferon-gamma is enhanced by iron chelation in colon cancer cell lines in vitro

BACKGROUND/AIMS: The receptor of interferon-gamma (IFN-gammaR) consists of IFN-gammaR1 and R2. Resistance to the anti-proliferative effect of IFN-gamma is due to downregulation of IFN-gammaR2. The aim of this study was to investigate whether iron chelation could upregulate IFN-gammaR2 and enhance the anti-proliferative effect of IFN-gamma in colon cancer cell lines. METHODOLOGY: The colon cancer cell lines, SW480, COLO, and WiDr were treated with the iron chelating agent DFO, and the expression of IFN-gammaR1 and IFN-gammaR2 was evaluated by FACS. The anti-proliferative effect of IFN-gamma was investigated by MTT assay, and the proapoptotic effect was investigated by FACS with Annexin-V. RESULTS: FACS demonstrated that DFO increased the expression of IFN-gammaR2, whereas the effect on IFN-gammaR1 expression was less marked. MTT assay showed that cell growth was inhibited by DFO. Addition of DFO and IFN-gamma inhibited further, but inhibition was not observed with IFN-gamma alone. Apoptotic cells were increased by DFO, and further increased with DFO + IFN-gamma together. CONCLUSIONS: Expression of IFN-gammaR2 is restored by iron chelation, and the increased expression of IFN-gammaR2 enhances the anti-proliferative effect of IFN-gamma through induction of apoptosis in colon cancer cells.     

PRL-3基因对结直肠癌细胞增殖能力的影响

目的:探讨PRL-3的过表达或敲低对结直肠癌细胞增殖能力的影响.方法:利用MTT法、平板克隆形成实验检测PRL-3对细胞体外增殖的影响;应用流式细胞术检测PRL-3对细胞周期的影响.结果:应用MTT法,检测PRL-3对SW480/EGFP、SW480-EGFP-PRL-3、SW480/EGFP/Mock及SW480-PRL-3-KD1细胞体外增殖能力的影响,经析因方差分析,4组差异具有显著性(F=23.463,P=0.000);不同时间点对细胞体外增殖的影响差异具有显著性(F=71.515,P=0.000);各组细胞与各时间组两因素交互效应显著(F=2.128,P=0.008);除第1天外,其他各时间点细胞组间的细胞增殖差异具有显著性.经LSD法多重比较,结果表明,与SW480/EGFP/Mock和SW480/EGFP细胞相比,SW480-EGFP-PRL-3细胞的增殖速度加快,而SW480-PRL-3-KD1细胞的增殖速度减慢.平板克隆形成实验显示SW480-EGFP-PRL-3细胞克隆形成能力明显增强,而SW480-PRL-3-KD1细胞克隆形成能力显著下降,差异具有显著的统计学意义(F=44.411,P=0.000).结论:PRL-3基因可促进结直肠癌细胞的增殖.     

MK615 inhibits pancreatic cancer cell growth by dual inhibition of Aurora A and B kinases

AIM：To investigate the anti-neoplastic effect of MK615, an anti-neoplastic compound isolated from Japanese apricot, against human pancreatic cancer cells in vitro.
METHODS： Three human pancreatic cancer cell lines PANC-1, PK-1, and PK45H were cultured with MK615 at concentrations of 600, 300, 150, and 0 μg/mL. Growth inhibition was evaluated by cell proliferation assay, and killing activity was determined by lactate dehydrogenase （LDH） assay. Expression of Aurora A and B kinases was detected by real-time polymerase chain reaction （PCR） and Western blotting. Cell cycle stages were evaluated by flow cytometry.
RESULTS： The growth inhibitory rates of MK615 at 150, 300, and 600 μg/mL were 2.3% ± 0.9%, 8.9% ± 3.2% and 67.1% ± 8.1% on PANC1 cells, 1.3% ± 0.3%, 8.7% ± 4.1% and 45.7 ± 7.6% on PK1 cells, and 1.2 ± 0.8%, 9.1% ± 2.1% and 52.1% ± 5.5% on PK45H cells, respectively （P 〈0.05）. The percentage cytotoxicities of MK615 at 0, 150, 300, and 600 μg/mL were 19.6% ± 1.3%, 26.7% ± 1.8%, 25.5% ± 0.9% and 26.4% ± 0.9% in PANC1 cells, 19.7% ± 1.3%, 24.7% ± 0.8%, 25.9% ± 0.9% and 29.9% ± 1.1% in PK1 cells, and 28.0% ± 0.9%, 31.2% ± 0.9%, 30.4% ± 1.1% and 35.3 ± 1.0% in PK45H cells, respectively （P 〈 0.05）. Real-time PCR and Western blotting showed that MK615 dually inhibited the expression of Aurora A and B kinases. Cell cycle analysis revealed that MK615 increased the population of cells in G2/M phase.
CONCLUSION： MK615 exerts an anti-neoplastic effect on human pancreatic cancer cells in vitro by dual inhibition of Aurora A and B kinases.     

Effect of antisense oligodeoxynucleotide of telomerase RNA on telomerase activity and cell apoptosis in human colon cancer

AIM:To explore the effect of antisense oligocleoxynucletide (As-ODN) of telomerase RNA on telomerase activity and cell apoptosis in human colon cancer.RESULTS:The telomerase activity in SW480 cells transfected with 1.0μmol/L of As-ODN for 2-5days, was significantly decreased in a time-dependent manner, and the cells underwent apoptosis.The missense ODN (Ms-ODN) and the control group transfected with SW480 cells did not show these changes.CONCLUSION:As-ODN can specifically inhibit the telomerase activity of SW480 cells and induce apoptosis.     

A novel anti-cancer substance, MK615, from ume, a variety of Japanese apricot, inhibits growth of hepatocellular carcinoma cells by suppressing Aurora A kinase activity

BACKGROUND/AIMS: MK615 is an anti-cancer substance extracted from the Japanese apricot. In the present study, the anti-neoplastic effect of MK615 against hepatocellular carcinoma (HCC) was evaluated in vitro, and its mechanism was elucidated. METHODOLOGY: Two HCC lines, HuH7 and Hep3B, were cultured with MK615 at concentrations of 600, 300, 150, and 0 microg/mL. Growth inhibition was evaluated by MTT assay, and killing activity was determined by LDH assay. Cell cycle stages were evaluated by flow cytometry. Expression of Aurora A kinase (Aurora A) was evaluated by real-time PCR and Western blotting, and inhibition of Aurora A activity was determined by HTscan. RESULTS: MK615 inhibited the growth of, and lysed, HuH7 and Hep3B cells in a dose-dependent manner. Cell cycle analysis revealed that MK615 increased the population of cells in G2/M phase. Real-time PCR and Western blotting showed that MK615 suppressed the expression of Aurora A. HTscan assay demonstrated that Aurora A activity was specifically inhibited by 34.3%, 32.9%, and 54.3% at 150, 300, and 600 microg/mL MK615, respectively. CONCLUSIONS: MK615 has an anti-cancer effect against HCC lines in vitro, and the effect is exerted through inhibition of Aurora A activity.     

EGCG对LoVo和SW480结肠癌细胞株的作用及对Notch1与Notch2基因表达的影响

目的:探讨绿茶提取物表没食子儿茶素没食子酸酯(EGCG)对结肠癌细胞株LoVo细胞和SW480细胞增殖的抑制作用,研究其对Notch1与Notch2的基因表达的影响,方法:体外培养LoVo细胞和SW480细胞,采用不同浓度的EGCG(10、20、35 mg/L)对其进行干预,MTT法检测EGCG对LoVo细胞和SW48...