Mechanism of counterattack of colorectal cancer cell by Fas/Fas ligand system

AIM: To determine the role of Fas/Fas ligand (FasL) in the immune escape of colon cancer cells. METHODS: Immunohistochemistry was used to observe the expression of Fas and FasL in the tissues of colon cancer patients. In situ hybridization was used to detect the localization of FasL mRNA expression in cancer tissues. Terminal deoxynucleotide transferase-mediated dUTP nick end labeling (TUNEL) assay and CD45 staining were performed to detect the apoptosis of tumor-infiltrating lymphocytes (TILs). Co-culture assays of colon cancer cells (SW480) and Jurkat cells (Fas-sensitive cells) were performed to observe the counterattack of colon cancer cells to lymphocytes. RESULTS: Of 53 cases of colon carcinomas, 23 cases (43.4%) expressed Fas which was significantly lower as compared to the normal colonic mucosa (73.3%, P<0.01), and 45 cases (84.9%) of colon carcinomas expressed FasL, whereas only two cases (3.75%) in normal mucosa expressed FasL. FasL expression in the colon cancer cells was found to be associated with increased cell death of TILs. The apoptotic rate of TIL in the FasL-positive staining regions of tumor cells was significantly higher than that in the FasL-negative staining region (54.84±2.79% vs 25.73±1.98%, P<0.01). The co-culture of SW480 cells and Jurkat cells confirmed the function of FasL on the SW480 cells. The apoptotic rates of Jurkat cells were found to be related with the amount of SW480 cells. CONCLUSION: Colon cancer cells can escape the immune surveillance and killing via decreasing Fas expression, and can counterattack the immune system via increasing FasL expression. Fas/FasL can serve as potential targets for effective antitumor therapy.     

Curcumin cytotoxicity is enhanced by PTEN disruption in colorectal cancer cells

AIM:To investigate the effects of phosphatase and tensin homolog deleted on chromosome 10(PTEN) deficiency on the cytotoxicity of chemotherapeutic agents toward colorectal cancer cells.METHODS:PTEN-deficient colorectal cancer(CRC) cells were generated by human somatic cell gene targeting using the adeno-associated virus system. The cytotoxic effects of compounds including curcumin,5-fluorouracil(5-FU),dihydroartemisinin(DHA),irinotecan(CPT-11)and oxaliplatin(OXA) on cancer cells were determined using the MTT assay. Enhanced cytotoxicity of curcumin in PTEN-deficient CRC cells was observed,and this was confirmed using clonogenic assays. Apoptosis and cell cycle progression were analyzed by flow cytometry.Levels of apoptosis and cell cycle-related proteins were examined by Western blotting.RESULTS:We developed an isogenic set of CRC cell lines that differed only in their PTEN status. Using this set of cell lines,we found that disruption of the PTEN gene had no effect on the sensitivity of CRC cells to5-FU,CPT-11,DHA,or OXA,whereas PTEN disruption increased the sensitivity of CRC cells to curcumin. Loss of PTEN did not alter the curcumin-induced apoptosis in CRC cells. However,PTEN deficiency led to an altered pattern of curcumin-mediated cell cycle arrest.In HCT116 PTEN+/+cells,curcumin caused a G2/M phase arrest,whereas it caused a G0/G1 phase arrest in HCT116 PTEN-/-cells. Levels of cell cycle-related proteins were consistent with these respective patterns of cell cycle arrest.CONCLUSION:Curcumin shows enhanced cytotoxicity toward PTEN-deficient cancer cells,suggesting that it might be a potential chemotherapeutic agent for cancers harboring PTEN mutations.     

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.     

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.     

Reduced expression ofβ-catenin inhibitor Chibby in colon carcinoma cell lines

AIM: To analyse the Chibby expression and its function in colon carcinoma cell lines and colorectal carcinoma (CRC). METHODS: Chibby expression levels were investigated by quantitative RT-PCR in a panel of seven different colon carcinoma cell lines. By sequencing, we analysed mutational status of Chibby. To test whether Chibby exhibited effects onβ-catenin signalling in colon carcinoma cells, we transfected SW480 cells with Chibby expression plasmid and, subsequently, analysed activity of p-catenin and tested for alterations in cellular phenotype. In addition, we examined Chibby mRNA levels in samples of colorectal carcinomas and adjacent normal tissues by using quantitative RT-PCR and hybridised gene chips with samples from CRC and normal tissues. RESULTS: Chibby mRNA expression was strongly down-regulated in colon carcinoma cell lines in comparison to normal colon epithelial cells and no mutation in any of the examined colon carcinoma cell lines was found. Further, we could show that Chibby inhibited p-catenin activity in TOPflash assays when over-expressed in SW480 cells. Proliferation and invasion assays with Chibby transfected SW480 cells did not reveal profound differences compared to control cells. In contrast to these in vitro data, quantitative RT-PCR analyses of Chibby mRNA levels in CRC tumor samples did not show significant differences to specimens in adjacent non-cancerous tissue. Consistent with these findings, gene chips analysing tissue samples of tumors and corresponding normal tissue did not show altered Chibby expression CONCLUSION: Altered Chibby expression might be observed in vitro in different colon carcinoma cell lines. However, this finding could not be confirmed in vitro in CRC tumors, indicating that Chibby is not likely to promote CRC tumor development or progression. As Chibby is an important inhibitor ofβ-catenin signalling, our data implicate that the usability of colon carcinoma cell lines for in vitro studies analysing the Wnt/β-catenin pathway in colorectal carcinoma needs extensive verification.     

Effect of indomethacin on cell cycle proteins in colon cancer cell lines

AIM: To study the effect of indomethacin (IN) on human colon cancer cell line SW480 with p53 mutant and SW480 transfected wild-type p53 (wtp53/SW480) in vitro and investigate molecular mechanism of anti-tumor effect of IN on colon cancer. METHODS: SW480 cells and wtp53/SW480 cells were treated with different concentrations of IN respectively, the expressions of CDK2, CDK4 and p21WAF1/CIP1 protein were detected by Western blotting. RESULTS: IN gradually down-regulated the expression of CDK2, CDK4 protein of wtp53/SW480 cells in a dose-dependent manner, and inhibitory effect reached the maximum level at 600 μmol/L; IN up-regulated the expression of p21WAF1/CIP1 protein in a dose-dependent manner at a certain concentration range, and the expression reached the maximum level at 400 μmol/L, and returned to the base level at 600 μmol/L. The expression of CDK2, CDK4 and P21WAF1/CIP1 protein of SW480 cells did not change. CONCLUSION: IN exerts antitumor effect partly through down regulation of the expression of CDK2, CDK4, protein and up regulation of the expression of p21WAF1/PIC1.     

New anti-proliferative agent, MK615, from Japanese apricot ＂Prunus mume＂ induces striking autophagy in colon cancer cells in vitro

AIM: To investigate the anti-neoplastic effects of MK615, an extract from the Japanese apricot (Prunus mume), against colon cancer cells. METHODS: Three colon cancer cell lines, SW480, COLO, and WiDr, were cultured with MK615. Growth inhibition was evaluated by cell proliferation assay and killing activity was determined by lactate dehydrogenase assay. Induction of apoptosis was evaluated by annexin Ⅴ flow cytometry. Morphological changes were studied by light and electron microscopy, and immunofluorescence staining with Atg8. RESULTS: MK615 inhibited growth and lysed SW480, COLO and WiDr cells in a dose-dependent manner. Annexin Ⅴ flow cytometry showed that MK615 induced apoptosis after 6 h incubation, at which point the occurrence of apoptotic cells was 68.0%, 65.7% and 64.7% for SW480, COLO, and WiDr cells, respectively. Light and electron microscopy, and immunofluorescence staining with Atg8 revealed that MK615 induced massive cytoplasmic vacuoles (autophagosomes) in all three cell lines. CONCLUSION: MK615 has an anti-neoplastic effect against colon cancer cells. The effect may be exerted by induction of apoptosis and autophagy.     

片仔癀对人结肠癌SW480细胞株的抑制作用研究

目的探究片仔癀对人结肠癌SW480细胞株的抑制效果。 方法通过对人结肠癌SW480细胞株常规体外培养,随机设定空白组、5-氟尿嘧啶（5-FU）组和不同浓度片仔癀组,分别采用对应药物干预24 h、48 h、72 h,并通过细胞增殖活力检测法（MTT法）和荧光显微镜观察其抑制效果。采用人结肠癌SW480细胞株建立结肠癌小鼠模型,把造模成功的150只小鼠随机分为模型组,5-FU组和片仔癀低、中、高剂量组,每组30只;分别以不同剂量药物外敷3 d,通过抑瘤率和原位凋亡检测（TUNEL法）解释抑制效果。 结果1 mg/mL、2 mg/mL、3 mg/mL浓度片仔癀对人结肠癌SW480细胞体外抑制率最高,为70.05%、71.39%、70.12%,与5-FU组比较差异具有统计学意义（χ²=4.49,4.97,4.52;均P<0.05）。4 mg/mL片仔癀抑制率为67.39%,与5-FU组比较差异无统计学意义（χ²=3.57,P>0.05）;荧光显微镜显示5-FU组与片仔癀各组人结肠癌SW480细胞株数量均显示不同程度的减少、体积变小、折光性差、细胞悬浮及脱落死亡。片仔癀高、中、低剂量组对人结肠癌SW480细胞的体内抑瘤率分别为51%、39%、23%,其中高、中剂量组与5-FU组比较差异无统计学意义（χ²=0.05,0.49;均P>0.05）,低剂量组与之比较差异有统计学意义（χ²=4.09,P<0.05）;荧光显微镜显示片仔癀各剂量组和5-FU组对人结肠癌SW480细胞均有不同程度的凋亡反应。 结论片仔癀外用对人结肠癌SW480细胞生长有明显的抑制作用,高、中剂量体内抑制作用与5-Fu相近,优于低剂量,临床可考虑采用高剂量可能取得更佳效果,体外抑制作用上显示则优于5-Fu,但剂量差异影响不大。     

Pyrrolidinedithiocarbamate increases the therapeutic index of 5-fluorouracil in a mouse model

BACKGROUND & AIMS: The thiol-containing antioxidant pyrrolidinedithiocarbamate (PDTC) enhances the cytotoxic efficacy of 5-fluorouracil (5-FU) against human colorectal cancer cell lines in vitro and in vivo. This process appears to be mediated by a sustained increase in p21 expression, independent of p53 function, resulting in growth arrest and apoptosis. We determined whether PDTC augmented 5-FU intestinal toxicity in non-tumor-bearing mice. METHODS: Apoptotic and mitotic indices were measured in the small and large intestine on a cell positional basis at intervals throughout the 72-hour period after administration of 5-FU (40 mg/kg) and PDTC (250 mg/kg). The proportion of crypts regenerating after 5-FU (600-1200 mg/kg) and PDTC (500 mg/kg) was also measured. RESULTS: 5-FU therapy induces substantial apoptotic cell death with simultaneous inhibition of mitotic activity within the small and large intestinal epithelium. PDTC reduces 5-FU-induced apoptotic events in the colon by 49%, predominantly among clonogenic stem and transit cells while promoting the early recovery of mitotic activity. As a consequence, PDTC increased the proportion of regenerating colonic crypts after 5-FU therapy. PDTC did not, however, significantly modulate 5-FU toxicity in the small intestine. CONCLUSIONS: PDTC does not augment the intestinal toxicity of 5-FU and actually protects the colonic mucosa. These results support further investigation of PDTC and related compounds as treatments for colorectal cancer.     

Synergistic anticancer effect of exogenous wild-type p53 gene combined with 5-FU in human colon cancer resistant to 5-FU in vivo

AIM To investigate the anticancer effect of a recombinant adenovirus-mediated p53(r Ad-p53) combined with 5-fluorouracil(5-FU) in human colon cancer resistant to 5-FU in vivo and the mechanism of r Ad-p53 in reversal of 5-FU resistance.METHODS nude mice bearing human colon cancer SW480/5-FU(5-FU resistant) were randomly assigned to four groups(n = 25 each): control group, 5-FU group, r Ad-p53 group, and r Ad-p53 + 5-FU group. At 24 h, 48 h, 72 h, 120 h and 168 h after treatment, 5 mice were randomly selected from each group and sacrificed using an overdose of anesthetics. The tumors were removed and the protein expressions of p53, protein kinase C(PKC), permeability-glycoprotein(P-gp) and multidrug resistance-associated protein 1(MRP1)(Western blot) and apoptosis(TUNEL) were determined.RESULTS The area ratios of tumor cell apoptosis were larger in the r Ad/p53 + 5-FU group than that in the control, 5-FU and r Ad/p53 groups(P 0.05), and were larger in the r Ad/p53 group than that of the control group(P 0.05) and the 5-FU group at more than 48 h(P 0.05). The p53 expression was higher in the r Ad/p53 and the r Ad/p53 + 5-FU groups than that of the control and 5-FU groups(P 0.05), and were higher in the r Ad/p53 + 5-FU group than that of the r Ad/p53 group(P 0.05). Overexpression of PKC, P-gp and MRP1 was observed in the 5-FU and control groups. In the r Ad/p53 + 5-FU group, the expression of P-gp and MRP1 was lower that of the control and 5-FU groups(P 0.05), and the expression of PKC was lower than that of the control, 5-FU and r Ad/p53 groups at more than 48 h(P 0.05). In the r Ad/p53 group, the expression of P-gp and MRP1 was lower that of the control and 5-FU groups at more than 48 h(P 0.05), and the expression of PKC was lower than that of the control and 5-FU groups at more than 120 h(P 0.05).CONCLUSION5-FU combined with r Ad-p53 has a synergistic anticancer effect in SW480/5-FU(5-FU resistance), which contributes to reversal of 5-FU resistance.     

Fas相关死亡结构域蛋白增强5-氟尿嘧啶抑制结肠癌细胞生长作用的研究

目的 通过体外和体内实验研究结肠癌细胞在稳定转染Fas相关死亡结构域蛋白(FADD)基因后对5-氟尿嘧啶的敏感性,探讨FADD基因与5-氟尿嘧啶联合治疗结肠癌的可行性.方法 ①RT-PCR和Western印迹法检测稳定转染FADD基因的结肠癌细胞SW480/FADD、稳定转染空载体的结肠癌细胞SW480/neo和正常结肠癌细胞SW480中FADD基因的mRNA和蛋白表达水平.②MTT法检测3种细胞对5-氟尿嘧啶的敏感性.TUNEL法和流式双染法检测细胞凋亡率.Western印迹法检测caspase-8和caspase-3的表达.③裸鼠成瘤实验观察瘤体生长曲线,病理学和TUNEL法检测肿瘤细胞凋亡.结果 ①SW480/FADD细胞FADD基因mRNA和蛋白表达水平明显较SW480和SW480/neo增高(P＜0.05).②5-氟尿嘧啶对SW480/FADD的抑制率明显高于SW480和SW480/neo,差异有统计学意义(P＜0.05).③5-氟尿嘧啶(10 mg/L)干预48 h后,SW480/FADD凋亡率达(33.3±4.5)%,与SW480[(13.9±3.2)%]和SW480/neo[(14.1±3.4)%]间差异有统计学意义(P＜0.05).④5-氟尿嘧啶(10 mg/L)干预48 h后,SW480、SW480/neo的procaspase-8和procaspase-3表达比SW480/FADD增高,而cleaved easpase-8和cleaved caspase-3的表达比SW480/FADD降低(P＜0.05).⑤SW480/FADD对5-氟尿嘧啶更加敏感,瘤体体积增加幅度明显小于SW480和SW480/neo,差异有统计学意义(P＜0.05).结论 稳定转染FADD基因可明显增加结肠癌细胞对5-氟尿嘧啶的敏感性,二者联合应用在结肠癌治疗中有潜在的价值.     

A subpopulation of CD24⁺ cells in colon cancer cell lines possess stem cell characteristics

Cancer stem cells (CSCs) have been shown to contribute to the resistance and relapse in a range of cancer types such as breast cancer and glioma. However, colon cancer stem cells remain poorly characterized. Here we reported that CD24+ subpopulation in colon cancer cell lines HCT116 and SW480 exhibited cancer stem cell-like characteristics. Using flow cytometry candidate CSCs markers were selected after initial screening of known CSCs markers from other types of cancer on colon cancer cell lines HCT116, SW480 and HT29. CD24 was expressed in the minority of bulk cell population of HCT116 and SW480 cell lines. Moreover, functional tests demonstrated that CD24+ cells exhibited enhanced chemotherapy-resistance, self-renewal and tumorigenic capacity both in vitro and in vivo, compared to CD24- subpopulations. These results suggest that CD24+ subpopulation in colon cancer cell lines HCT116 and SW480 exhibits CSCs like characteristics, and represents a nice model to study and develop effective strategies to overcome chemo-resistance and relapse of colon cancer.     

Hsp70 response to 5-fluorouracil treatment in human colon cancer cell lines

Background and aims Colorectal cancer is a common disease with high rate of mortality. Although there is evidence of some benefits of 5-fluorouracil (5-FU), the most commonly used drug in colon cancer therapy, it still remains unsatisfactory because of intrinsic or acquired drug resistance. Heat shock proteins (Hsps) synthesis can be increased by cellular insults, such as chemotherapy-induced damage. Inducible Hsp70 has been suggested to be involved in cytoprotection against apoptosis. In the present study, we investigated whether the content of Hsp70 is associated to 5-FU resistance. Methods HT-29 and SNU-C4 human colon cancer cell lines were treated with 5-FU and their relative chemoresistance, and Hsp70 were determined. Results Comparison of IC₅₀ values showed that the HT-29 cells were relatively resistant to 5-FU, whereas the SNU-C4 cells presented greater sensitivity to this drug. Further, 5-FU treatment leads to a hypodiploid population in HT-29 cells significantly lower compared to SNU-C4 cells. In the HT-29 cell line, 5-FU treatment promoted an increase of 5.5 times in Hsp70 concentration after 12 h. Then, within 24 h, the increase in Hsp70 levels was still about two times. In contrast, in the SNU-C4 cell line, 5-FU induced an increase of about two times in the Hsp70 content after 12 h and, after 24 h, did not significantly affect Hsp70 content. Conclusions These data suggest that 5-FU induced Hsp70 synthesis in the HT-29 resistant cell line and that this Hsp70 accumulation could protect against 5-FU-induced apoptosis. Thus, Hsp70 protection against 5-FU-induced apoptosis might underlie colon cancer chemoresistance.     

结肠癌耐药细胞株LoVo/5-FU的建立及其差异表达基因的筛选

目的:建立结肠癌细胞耐药模型LoVo/5-FU并初步筛选可能的耐药相关基因.方法:采用5-FU浓度递增法建立人结肠癌细胞耐药模型LoVo/5-FU,观察其生长规律并绘制细胞生长曲线:用MTT法鉴定耐药细胞株耐药性并计算耐药指数(RI);用基因芯片技术检测耐药细胞株LoVo/5-FU与其亲本细胞株LoVo中的差异表达基因,从中筛选出可能的耐药相关基因;用半定量RT-PCR方法对筛选出的部分耐药相关基因在耐药细胞及其亲本细胞中的表达情况进行验证.结果:LoVo/5-FU细胞与LoVo细胞相比,生长缓慢,细胞体积增大.LoVo/5-FU对5-FU、ADM、MMC耐药,而对CDDP无耐药性(RI:7.69,2.78,1.43和0.96).通过基因芯片筛选出差异表达基因425个,可能的耐药相关基因包括CYP1B1,NAT2,RNF20,SNAI2,MAP3K2,其中CYP1B1在LoVo/5-FU与LoVo中的表达有明显差异(Cy5/Cv3=5.877).结论:LoVo/5-FU细胞株耐药性稳定,耐药机制可能与CYP1B1,NAT2等耐药相关基因有关.