Epigenetic drug combination induces genome-wide demethylation and altered gene expression in neuro-ectodermal tumor-derived cell lines

Background

Epigenetic alterations are inherent to cancer cells, and epigenetic drugs are currently primarily used to treat hematological malignancies. Pediatric neuro-ectodermal tumors originate from neural crest cells and also exhibit epigenetic alterations involving e.g. apoptotic pathways, which suggests that these tumors may also be sensitive to epigenetic drugs. This notion prompted us to assess molecular and functional effects of low dosage epigenetic drugs in neuro-ectodermal tumor-derived cell lines of pediatric origin.

Results

In 17 neuroblastoma (NBL) and 5 peripheral primitive neuro-ectodermal tumor (PNET) cell lines a combination treatment of 5-aza-2′-deoxycytidine (DAC) and Trichostatin A (TSA) at nanomolar dosages was found to reduce proliferation and to induce wide-spread DNA demethylation, accompanied by major changes in gene expression profiles. Approximately half of the genes that were significantly up-regulated upon treatment exhibited a significant demethylation in their promoter regions. In the NBL cell lines, almost every cellular pathway (193/200) investigated showed expression alterations after treatment, especially a marked up-regulation of genes in the p53 pathway. The combination treatment also resulted in up-regulation of known epigenetically regulated genes such as X-chromosomal genes, tissue-specific genes and a limited number of imprinted genes, as well as known tumor suppressor genes and oncogenes.

Conclusions

Nanomolar dosages of epigenetic drugs have a dramatic impact on the genomes of neuro-ectodermal tumor-derived cell lines, including alterations in DNA methylation and concomitant alterations in gene expression.     

Nitric oxide induces cyclooxygenase expression and inhibits cell growth in colon cancer cell lines

The role of nitric oxide (NO) in colon cancer remains controversial. Inducible nitric oxide synthase (iNOS) has been reported to be up regulated and down regulated in colorectal cancer in both animal models and patient tissue samples. Cyclooxygenase-2 (COX-2) is important in colorectal carcinogenesis but its relationship with NO has never been studied in colon cancer. Three colon cancer cell lines (HCA7, HT29 and HCT116) with different COX-2 expression and activities were used to study the effect of the NO donor, S-nitrosoglutathione (GSNO). The effects of GSNO (10-500 micro M) on cell growth, PGE(2) production, COX-1/COX-2 protein expression and cell-cycle distribution were evaluated. GSNO increased PGE(2) production and induced COX-1 and COX-2 protein expression in a dose- and time-dependent manner. Higher concentrations of GSNO also inhibited cell growth and induced apoptosis in all three cell lines, regardless of their COX-2 expression/activities. Inhibition of PGE(2) production did not further improve the inhibitory effect of GSNO.     

Mechanisms of confluence-dependent expression of CD26 in colon cancer cell lines

Background  

CD26 (dipeptidyl peptidase IV, DPPIV) is a 110 kDa surface glycoprotein expressed in most normal tissues, and is a potential novel therapeutic target for selected cancers. Our work evaluates the mechanism involved in confluence-dependent CD26 expression in colon cancer.     

EID3基因在大肠癌传代细胞mRNA的表达及其克隆

目的研究新的大肠癌相关性抗原EID3基因的克隆及其诊断价值。方法用SEREX技术筛选睾丸组织cDNA噬菌体表达文库,发现了一类似于肿瘤抑制基因（E1A基因）的EID3基因（NM_001008394.1）,构建原核表达载体pET32k-EID3,IPTG诱导重组EID3蛋白质的表达,并利用Ni NTA His Bind树脂纯化该重组蛋白质。用RT-PCR技术研究EID3mRNA在正常组织和大肠癌传代细胞的表达。结果经PCR扩增成功获得1002bp的人EID3基因,测序正确。在大肠杆菌中目的蛋白质的表达量占菌体总蛋白质的10%,SDS-PAGE及Western blot分析显示,其相对分子质量为39000KD,纯化后的6xHisEID3纯度可达92%。通过RT-PCR分析发现,EID3基因在43例大肠癌传代细胞株中有39例阳性,阳性率为90.7%。在正常组织中,除睾丸组织不表达或有极低水平转录外,余均不表达。结论 EID3基因克隆、表达及纯化的成功,为其今后的肿瘤诊断和肿瘤多肽疫苗治疗研究奠定了基础。EID3m RNA表达检测用于诊断大肠癌,可能具有高特异性和高敏感性的特点。EID3蛋白在大肠癌患者中能够诱导机体的抗体免疫应答,可能成为一个新的大肠癌相关性抗原分子,其用于诊断大肠癌的可行性,有待进一步深入研究。     

RBM8A在人结肠癌细胞株中的表达及其意义

目的 检测RBM8A在不同结肠癌细胞株中的表达,为进一步体外实验筛选靶细胞。方法 采用实时定量反转录聚合酶连锁反应（qRT-PCR）法以及蛋白免疫印迹（Western-blot）法检测RBM8A在结肠癌细胞株SW480、SW620、HT29、LOVO、COLO320DM、T84及人正常结肠上皮细胞株NCM460中的表达。结果 RBM8A在7株细胞株中均有表达,其中在结肠癌细胞株SW620和COLO320DM中的表达高于正常细胞株,差异有统计学意义（P＜0.05）,而其余细胞株中RBM8A的表达与正常细胞株差异无统计学意义（P＞0.05）。结论 RBM8A在结肠癌细胞株SW620和COLO320DM中高表达,SW620和COLO320DM细胞株或可作为靶细胞。     

Differences in the expression of mucus-associated antigens between proximal and distal human colon adenocarcinomas

An immunohistological study showed differences in the expression of mucus-associated gastric M1 and intestinal M3 antigens between the proximal (100 cases) and distal (200 cases) colonic adenocarcinomas. Such a regional difference was not observed in the normal colon. A total of 55% and 78% of proximal tumours produced M1 and M3 antigens, respectively (versus 13% and 47% in the distal tumours). The high percentage of M1 positive proximal cancers could be explained by the higher percentage (i) of mucus-producing tumours, such as signet ring cell (6% vs 1%) or mucinous adenocarcinomas (29% vs 11%); and (ii) of M1(+) well-differentiated adenocarcinomas (45% vs 8.5%) and the presence of undifferentiated carcinoma producing M1 antigens (12% vs 0%). These latter carcinomas were found in older patients (mean age 78 years vs 66 years). These results suggest that, on the proximal side, the stem cells were more often engaged in a differentiation process involving the expression of M antigens than were those of the distal side. Moreover, the proximal stem cells more frequently produce a foetal differentiation program showing simultaneous expression of M3 and M1 antigens (in 48% of proximal tumours, vs 11.5% for the distal side). Around 12% of proximal adenocarcinomas (vs 2% of distal tumours) contained stem cells engaged in a cell differentiation program not observed in the normal adult or foetal colon, involving the predominant expression of M1 antigens associated with an undifferential histological pattern.     

结肠腺癌细胞株Fas／FasL的表达与凋亡的关系

目的研究结肠腺癌细胞株经不同化疗药物诱导后Fas/FasL表达与癌细胞凋亡的关系,探索敏感化疗药物的筛选.方法将顺铂、丝裂霉素、氟尿嘧啶、表阿霉素按PPC(血浆峰浓度)、1/10PPC、1/5PPC、5PPC、10PPC加入结肠腺癌LS174T细胞、LoVo细胞共孵,用流式细胞术(FACScan)检测癌细胞Fas、FasL表达率及细胞凋亡率,并提取DNA进行琼脂糖凝胶电泳.结果FACScan检测显示LS174T细胞顺铂组、丝裂霉素组、表阿霉素组Fas表达率、细胞凋亡率在1/5PPC或PPC时最高,Fas表达率与细胞凋亡率呈正相关(P＜0.05).LoVo细胞经化疗药物诱导后Fas表达率与细胞凋亡率无显著相关(P＜0.05).结论FACScan检测的癌细胞凋亡率可用于敏感化疗药物及其合适剂量的筛选,Fas表达率可能仅适用于部分癌症病人化疗药物的筛选;LS174T细胞与LoVo细胞凋亡途径的不同说明化疗药物的个体化选择研究的重要性.     

P-glycoprotein expression and schedule dependence of adriamycin cytotoxicity in human colon carcinoma cell lines.

Four human colon cancer cell lines (SW620, LS 180, DLD-I, and HCT-15) and Adriamycin-resistant sub-lines with varying degrees of P-glycoprotein expression were studied to evaluate the reversibility of Adriamycin resistance in human colon cancer. Two groups of cell lines were studied. In the first, including a series of Adriamycin-resistant SW620 and DLD-I sub-lines, and in parental HCT-15 cells, P-glycoprotein has a major role in Adriamycin resistance, as evidenced by a correlation between Adriamycin resistance, expression of the multidrug-resistance gene mdr-I and its product, P-glycoprotein (Pgp), decreased drug accumulation and reversibility by verapamil. In these cell lines, increasing doses of verapamil are required to fully reverse increasing levels of resistance. In the second group, including parental SW620, DLD-I and LS 180 cells and Adriamycin-selected LS 180 sub-lines, P-glycoprotein does not have a major role in Adriamycin resistance. There was correlation between the schedule dependence of Adriamycin cytotoxicity and the role of P-glycoprotein in modulating resistance. In the cell lines in which P-glycoprotein was a major determinant of Adriamycin resistance, the drug exposure (defined as the product of the concentration and the time of treatment) needed to achieve a given percent cell kill was reduced as much as 9-fold when cells were treated for 7 days as compared with 3 hr. By comparison, in cell lines in which P-glycoprotein played a lesser role, the drug exposure necessary to achieve a given percent kill increased under conditions of continuous treatment. In some human colon carcinoma cell lines Pgp appears to play a significant role in resistance to Adriamycin, and this can be overcome by the use of competitive inhibitors of Pgp. The increased sensitivity with continuous treatment observed in cell lines with P-glycoprotein-mediated resistance suggests that administration of drugs by continuous infusion may be valuable in reversing clinical drug resistance mediated predominantly by P-glycoprotein.     

Heparanase表达下调对结肠癌细胞增殖和侵袭的影响

目的 探讨乙酰肝素酶（Heparanase）对结肠癌细胞生物学功能的影响。方法 采用荧光定量PCR检测人结肠癌细胞株SW620、SW480、LoVo和CACO 2中Heparanase的表达水平;设计并合成3条Heparanase特异性的小分子干扰RNA（siRNA1、siRNA2、siRNA3）,用于转染4株结肠癌细胞中Heparanase表达水平最高者;荧光定量PCR和Western blotting检验3条siRNA的干扰效果;MTT法检测结肠癌细胞的增殖能力;Transwell小室法检测结肠癌细胞的侵袭能力。结果 SW480细胞中Heparanase的表达水平高于其他3株结肠癌细胞;3条特异性siRNA转染SW480细胞后,均能在蛋白和mRNA水平抑制Heparanase的表达,以siRNA3的效果最佳,且呈剂量依赖性。siRNA3介导的Heparanase基因沉默可呈剂量依赖地降低SW480细胞的增殖能力并减弱侵袭能力（P＜0.05）。结论 Heparanase表达下调可导致结肠癌细胞生物学恶性程度降低,提示Heparanase可作为结肠癌靶向治疗的一个重要靶点。     

Serial analysis of gene expression identifies putative metastasis-associated transcripts in colon tumour cell lines

We have used serial analysis of gene expression (SAGE) to identify gene expression differences between a primary colon tumour cell line (SW480) and an isogenic lymph-node metastasis cell line (SW620). Differential expression was confirmed for the following genes: keratin K5, cystatin S, serum amyloid A, the human homologue of yeast ribosomal S28 and the p32 subunit of human pre-mRNA splicing factor SF2. Expression of confirmed differences were also analysed in other metastatic cell lines.     

Modulation of EGF receptor expression by differentiating agents in human colon carcinoma cell lines

The existence of an autocrine loop for self-stimulation of growth in malignant cells has been proposed for transforming growth factor-alpha (TGF alpha) and its receptor, the epidermal growth factor (EGF) receptor, in a variety of malignant cell types. Expression of both has been described in colon carcinoma. In order to investigate whether there is a correlation between TGF alpha and EGF receptor mRNA expression and differentiation, we studied the effects of differentiating agents on seven human colon carcinoma cell lines. All of the lines responded to the differentiating agents. In four of the seven lines there was increased EGF receptor mRNA two to five days after treatment with 2 mM sodium butyrate. In three of these lines TGF alpha mRNA and protein were also increased. In the one cell line treated with the differentiating agents DMF and DMSO, EGF receptor mRNA was also increased. [125I]-EGF binding to the cells was measured before and after treatment with butyrate. In two of three cell lines, increased EGF receptor mRNA was accompanied by a 2.4-fold increase in the number of binding sites per cell. In SW620 cells, no EGF receptor binding was detected before or after butyrate treatment. In the two cell lines in which butyrate increased EGF receptor binding, simultaneous treatment with EGF did not enhance growth. These data demonstrate increased expression of the TGF alpha/EGF receptor system after differentiation of colon carcinoma cell lines and suggest that their expression may be characteristic of a differentiated phenotype.     

Characterization of six cell lines established from human pancreatic adenocarcinomas

BACKGROUND: Six human pancreatic carcinoma cell lines, designated as KMP-1 to KMP-6, were established and maintained in vitro for > 3 years. All were derived from pancreatic ductal adenocarcinomas. The six cell lines originated from either primary pancreatic tumors, metastatic liver tumors, or metastases to lymph nodes. METHODS: Each cell line was characterized by its morphology, doubling time, colony forming efficiency (CFE) on plastic dishes, tumorigenicity in nude mice, chromosomal analysis, and the amount of tumor markers secreted into the culture medium. Furthermore, mutations in the K-ras, p53, and p16/INK4a genes were analyzed. RESULTS: All cell lines grew as an adhering monolayer and were cultured in medium supplemented with 2% fetal bovine serum. The doubling time ranged from 16-70 hours, and the CFE ranged from 0.1-11%. Subcutaneous transplantation of these carcinoma cells into nude mice resulted in the formation of tumors. Chromosomal analysis showed that the modal numbers ranged from 43-124, and each karyotype was unique. Each cell line secreted detectable amounts of squamous cell carcinoma antigen, carcinoembryonic antigen, carbohydrate antigen 19-9, Dupan-II, and cytokeratin 19 fragment, respectively. Genetic alterations of the K-ras, p53, and p16 genes were detected in six, three, and five, respectively, of the six cell lines. CONCLUSIONS: The authors believe that these newly established pancreatic carcinoma cell lines will contribute to wide ranging studies regarding pancreatic carcinoma progression.     

Caveolin-1 levels are down-regulated in human colon tumors, and ectopic expression of caveolin-1 in colon carcinoma cell lines reduces cell tumorigenicity

Caveolin-1 expression and function were investigated in human colon cancer. Low levels of caveolin-1 mRNA and protein were detected in several colon carcinoma cell lines. Moreover, caveolin-1 protein levels were significantly reduced in human tumor epithelial mucosa (3.6 +/- 1.4-fold) when compared with normal colon mucosa for a majority (10 of 15) of the patients characterized. To directly assess the role of caveolin-1 in tumor development, caveolin-1 was reexpressed in the HT29 and DLD1 colon carcinoma cells, and the resulting HT29-cav-1 or DLD1-cav-1 cells were tested for tumorigenicity in nude mice. In most experiments, tumor formation was either blocked or retarded for HT29-cav-1 cells (10 of 13 mice) and DLD1-cav-1 cells (5 of 7 mice), as compared with both mock-transfected and parental HT29 or DLD1 cells. Interestingly, basal caveolin-1 levels were significantly reduced in HT29-cav-1 and DLD1-cav-1 cells isolated from tumors. Likewise, endogenous caveolin-1 mRNA and protein levels were found to be reduced in NIH-3T3 cells recovered from tumors after injection into nude mice. Thus, reexpression of caveolin-1 in colon carcinoma lines reduced the probability of tumor formation in vivo, and when tumors did develop from either HT29-cav-1, DLD1-cav-1, or NIH-3T3 cells, lower basal levels of caveolin-1 were detected. Finally, evidence was obtained indicating that initial caveolin-1 down-regulation in colon cancer cells need not be an entirely irreversible process because cell survival on selection for either drug resistance or increased metastatic potential correlated with increased caveolin-1 expression levels.     

Oncogene expression in small-cell lung cancer cell lines and a testicular germ-cell tumor: activation of the N-myc gene and decreased RB mRNA

N-myc and L-myc proto-oncogenes are expressed in many developing embryonic tissues. In contrast to expression of the closely related c-myc gene, N-myc and L-myc expression is very restricted in adult tissues. We show that small amounts of the L-myc RNA can be detected in normal adult testicular tissue. A high level of N-myc expression from a single-copy N-myc gene was found in a malignant tumor of the testis, histopathologically defined as a seminoma. This tumor also showed a decrease of mRNA from the retinoblastoma gene (RB), which is ubiquitously expressed in all normal tissues. Strikingly similar results on elevated expression of the L-myc and N-myc genes and a lack of RB mRNA have been reported in small-cell lung cancer cell lines, and are confirmed in our study.