Methylation and regulation of expression of different retinoic acid receptor beta isoforms in human colon cancer

Tumor suppressor genes can become inactivated in cancer via hypermethylation of their promoter. The retinoic acid receptor beta (RARbeta) gene is expressed from two distinct promoters, both of which have CpG islands. RARbeta1 is expressed primarily during embryogenesis, whereas RARbeta2 is expressed in adult tissues and hypermethylated in a number of cancer cells. We used combined bisulfite restriction analysis to evaluate their methylation in colorectal mucosa and tumors. Methylation of RARbeta1 was detected, with a mean of 2% in normal colon tissues in young subjects (< 32 years), and 16% in older subjects (> 75 years) (P < 0.001). Using paired normal/tumor tissue samples, we found higher mean methylation rate in tumors than in adjacent normal tissue (mean, 46% versus 16%; P < 0.001) and hypermethylation of RARbeta1 in all eight cell lines examined. By RT-PCR, RARbeta1 was not expressed in normal adult colon tissues and its expression could not be efficiently activated in most cell lines by the DNA methyltransferase inhibitor 5-aza-2'-deoxycytidine (5-Aza-CdR). RARbeta2 methylation was also observed in normal colon tissues and was lower in young individuals than in older ones (mean, 11% versus 23%; P < 0.05). Among paired samples, RARbeta2 methylation was higher in tumor tissue than in normal tissue in 14 cases, vice versa in 7 cases, and equal in 6 cases. All eight cell lines were hypermethylated and did not express RARbeta2, but RARbeta2 expression could be reactivated easily by 5-Aza-CdR. We suggest that the embryonic RARbeta1 isoform is readily hypermethylated in aging colon mucosa and all colorectal cancers because of its lack of expression in normal tissues. The adult RARbeta2 isoform also shows age-related methylation in normal tissues but more variable methylation in colorectal cancer, perhaps because its expression offers continued protection against methylation or its silencing does not provide a selective advantage in the early stages of the disease.     

Conserved expression of hepatocyte growth factor activator inhibitor type-2/placental bikunin in human colorectal carcinomas

Hepatocyte growth factor activator inhibitor type 2 (HAI-2) was recently identified as a potent inhibitor of hepatocyte growth factor activator. It was also independently reported as placental bikunin (PB) and as a protein over-expressed in pancreatic cancer. The expression of HAI-2/PB was analyzed in human normal colon mucosa, adenomas, and carcinomas. HAI-2/PB mRNA was consistently expressed in the colorectal mucosa. The expression was conserved in the neoplastic colorectal mucosa, and no relationship was found between HAI-2/PB mRNA levels and tumor stages. Moreover, 13 out of 14 colorectal carcinoma cell lines expressed HAI-2/PB mRNA. Immunohistochemically, HAI-2/PB proteins were predominantly stained beneath the apical surface of normal enterocytes. In tumor tissues, rather disarranged intracytoplasmic granular staining was observed. The HAI-2/PB immunoreactivity was well conserved in the colonic adenoma-carcinoma sequence, and this protein may have important unknown function in the intestinal mucosa.     

Loss of KAI1 expression in the progression of colorectal cancer

The transmembrane 4 superfamily member KAI1 (CD82) has been shown to inhibit pulmonary metastases in experimental metastasis models of prostate cancer and melanoma. KAI1 expression is decreased in the progression of common solid epithelial tumors of adulthood, including lung, prostate, breast, esophageal, gastric, pancreatic, and bladder cancers. The purpose of our study was to investigate KAI1 expression in the progression of human colorectal cancer. We first analyzed 20 colorectal cancer cell lines by immunoblot techniques. KAI1 was expressed heterogeneously, with the tumor cell lines having a more complex degree of glycosylation compared with that of the normal colonic tissue. KAI1 was highly expressed in the primary SW480 colon cancer cell line but was down-regulated 15-fold in the matched metastatic SW620 cell line. We also investigated KAI1 protein expression by immunohistochemistry in tissues from 84 patients with colorectal cancer. Each tissue section was assigned a KAI1 mean score (KMS) from 0 to 300 based on the product of the percentage of cells that stained for KAI1 and the intensity of the stain (1, 2, or 3). In 84 patients with colorectal cancer, KAI1 was expressed at high levels in normal colonic mucosa (KMS 226) but was expressed at lower levels in the primary tumors (KMS 65; P < 0.0001). In a subset of 12 patients with stage IV metastatic disease, we observed a progressive down-regulation of KAI1, from the normal adjacent colonic mucosa (KMS 193) to the primary tumor (KMS 72; P = 0.0001) to the liver metastasis (KMS 25; tumor compared with metastasis, P = 0.0135). We found no correlation between loss of KAI1 expression and stage of disease. In 10 patients, we also noted loss of KAI1 expression in the transition from normal colonic mucosa (KMS 237) to adenoma (KMS 174) to carcinoma (KMS 62; P < 0.0167 for all three comparisons). We conclude that the down-regulation of KAI1 occurs early in the progression of colorectal cancer.     

herg1 gene and HERG1 protein are overexpressed in colorectal cancers and regulate cell invasion of tumor cells

The acquisition of the capacity to invade surrounding tissues confers a more malignant phenotype to tumor cells and is necessary for the establishment of metastases. The understanding of the molecular mechanisms underlying cell invasion in human solid tumors such as colorectal cancers could provide not only more sensitive prognostic analyses but also novel molecular targets for cancer therapy. We report in this article that K(+) ion channels belonging to the HERG family are important determinants for the acquisition of an invasive phenotype in colorectal cancers. The herg1 gene and HERG1 protein are expressed in many colon cancer cell lines, and the activity of HERG channels modulates colon cancer cell invasiveness. Moreover, the amount of HERG1 protein expressed on the plasma membrane is directly related to the invasive phenotype of colon cancer cells. Finally, both the herg1 gene and HERG1 protein were expressed in a high percentage of primary human colorectal cancers, with the highest incidence occurring in metastatic cancers, whereas no expression could be detected either in normal colonic mucosa or in adenomas.     

人mcl1不同亚型在结肠癌组织中表达变化的临床意义

目的 探讨人mcl1基因不同亚型在结肠癌组织中差异表达的临床意义。方法 采用RT-PCR和Western blot分别检测正常结肠组织、结肠腺瘤、结肠腺癌组织以及相应的癌旁组织各20例中mcl1基因三种mRNA剪接异构体和三种蛋白亚型的表达水平,进而分析这些亚型表达差异与肿瘤临床病理特征之间的相关性。结果 mcl1基因亚型1在结肠肿瘤组织及相应旁组织中的mRNA和蛋白质水平表达均高于正常组（P=0.009, P=0.022）,且腺癌组中的mRNA和蛋白质水平表达亦高于腺瘤组（P=0.004, P=0.034）。亚型2在结肠肿瘤组织及对应旁组织中的mRNA和蛋白质水平表达均高于正常组（P=0.002, P=0.011）,且腺癌组中的mRNA和蛋白质水平表达亦高于腺瘤组（P<0.001, P=0.007）。亚型3在结肠肿瘤组织及对应旁组织中的mRNA和蛋白质水平表达均高于正常组（P=0.027, P=0.045）,但肿瘤组与相应旁组织之间以及腺癌组与腺瘤组之间的比较差异均无统计学意义。结论 研究表明mcl1亚型1和亚型2对结肠癌肿瘤恶性程度呈正相关,可以作为临床评估结肠癌恶性程度有效的诊断指标之一。而亚型3可以作为肿瘤早期诊断的标志物,但其表达水平与恶性程度无明显相关性。     

HER-2 receptor expression, localization, and activation in colorectal cancer cell lines and human tumors

The HER-2/neu oncogene encodes a 185 kD protein that is phosphorylated upon ligand binding to other HER/erbB members and regulates cell growth and differentiation. Given that HER-2 receptor blockade can inhibit the growth of colon cancer cell lines and tumor xenografts, we investigated the frequency, localization and phosphorylation status of HER-2 in colon cancer cell lines and in human tumors. Protein expression was analyzed in relation to mRNA levels, HER-2 amplification, and clinicopathological variables. Colon cancer cell lines constitutively expressed HER-2 proteins and none showed HER-2 amplification by fluorescence in situ hybridization. Cell fractionation and immunoblotting showed HER-2 in both the membrane and cytosolic compartments. Primary colorectal carcinomas (n = 96) and their metastases (n = 25) were examined by immunohistochemistry. Strong membrane HER-2 staining was detected in 5 (5%) of primaries and in 3 (12%) metastases (p = 0.36). Membrane but not cytoplasmic localization was strongly associated with HER-2 gene amplification (p = 0.007). Cytoplasmic HER-2 staining was found in 61 (63.5%) of primary tumors and localization was confirmed by immunoelectron microscopy that also showed plasma membrane HER-2. Using real-time quantitative RT-PCR, HER-2 mRNA was increased in tumors with membrane compared to cytoplasmic staining (r = 0.66, p = 0.001). Cytoplasmic HER-2 was associated with tumor differentiation (p = 0.018), but not other clinicopathological variables. By immunoblotting, heterogeneity was seen in HER-2 levels with downregulation in 4 of 7 tumors relative to normal epithelia that uniformly expressed HER-2. Phosphorylated HER-2 was detected in approximately 50% of tumors and in normal mucosa. In conclusion, HER-2 is expressed constitutively in colon cancer cell lines and demonstrates relatively distinct localization patterns in human tumors. Strong membrane immunoreactivity is associated with high levels of HER-2 mRNA and gene amplification whereas cytoplasmic HER-2 is detected frequently and seems to be a marker of tumor differentiation.     

set基因在人结直肠腺癌中表达的研究

目的探究set基因在人类结直肠腺癌组织中的表达情况及其表达水平与临床病理特征之间的关系。方法 通过半定量PCR检测set基因在39例结直肠腺癌组织与自身对照的正常结直肠组织中的mRNA表达,免疫组织化学检测SET蛋白在9例结直肠腺癌患者癌组织及其自身对照的正常结直肠组织中的表达。结果 (1)set基因在26例结直肠腺癌组织中的mRNA表达水平高于其自身对照正常结直肠组织,占总数的66.7%的,其中6例患者set基因在结直肠腺癌组织中的表达水平是其在正常癌旁组织中表达水平的2倍以上,最高达22倍(P<0.05)。(2)免疫组织化学显示,SET蛋白在结肠腺癌和癌旁组织细胞核中均表达,其中8例患者的癌组织SET蛋白表达水平明显高于癌旁组织(P<0.05)。结论 set基因在结肠癌中的表达上调,可能与结直肠腺癌发病有关。     

Expression of carcinoembryonic antigen (CEA) and nonspecific crossreacting antigen (NCA) in gastrointestinal cancer; the correlation with degree of differentiation.

In spite of its reputation as a tumour marker, little is known about the function of carcinoembryonic antigen (CEA). We examined the mRNA expression of CEA and NCA in 26 gastric and 14 colorectal cancers together with adjacent morphologically normal mucosae. There was no significant difference between the CEA mRNA levels of colorectal cancer and adjacent mucosa, whereas the CEA mRNA levels were significantly elevated in gastric cancer compared with normal gastric mucosa. The expression of NCA, on the other hand, was more cancer-specific and was significantly up-regulated in both gastric and colorectal cancers compared with the corresponding normal mucosae. No correlation was found between the mRNA level and plasma CEA value. No significant up-regulation was recognised in the node positive cancer, cancer with distant metastasis, or the metastatic tissues themselves. Marked diversity in the degree of differentiation in gastric cancer tissues, however, resulted in varied expression of the CEA gene family, compared with the constantly high expression found in colorectal cancer. Further analysis revealed significant up-regulation of NCA in well and moderately differentiated gastric cancers over poorly differentiated cancers, suggesting that NCA might have roles in differentiation.     

WT1 is a tumor-associated antigen in colon cancer that can be recognized by in vitro stimulated cytotoxic T cells

The Wilms' tumor suppressor gene (WT1) has been shown to be overexpressed in acute and chronic leukemias and in a variety of solid human malignancies, including cancers of the breast and lung. In our present study, we investigated the potential role of WT1 gene in human colon cancer. WT1 mRNA and protein expression was analyzed in a panel of human colon cancer cell lines and primary colon carcinomas by RT-PCR and Western blot analysis, respectively. A mutational screen of WT1' zinc-finger region was carried out by sequence analysis. Finally, using peptide-stimulated cytotoxic T cells it was investigated whether WT1-expressing colon tumor cells are a potential target for antigen-specific immunotherapy. Medium to high abundant levels of WT1 mRNA were detected by RT-PCR in 10 of 12 (83%) colon cell lines and by quantitative, real-time RT-PCR in 13 of 15 (87%) primary tumors, whereas only very low levels of expression were found in 2 primary tumors. Interestingly, however, low levels of WT1 mRNA were also detected in all samples derived from normal colon mucosa. When RT-PCR products were examined by sequence analysis, both +KTS and -KTS splice isoforms but no zinc-finger mutations were found, suggesting that the wild-type form of the WT1 gene is expressed. To determine whether the WT1 protein can serve as a target antigen for immunotherapy, 2 HLA-A2.1-restricted WT1 peptides (Db126 and WH187) were used for the in vitro induction of WT1-specific cytotoxic T lymphocytes (CTLs). The WH187-specific CTLs not only lysed target cells pulsed exogenously with cognate peptide but also WT1-expressing colon tumor cells in a HLA-restricted manner. These findings identify the WT1 protein as an attractive target for the development of antigen-specific immunotherapy in human colon cancer.     

Identification of CRASH, a gene deregulated in gynecological tumors

We have identified CRASH, a human asparaginase-like protein which is composed of 308 amino acids and exhibits 32% homology to human aspartylglucosaminadase at the amino acid level. Database analysis revealed that the gene corresponding to CRASH is composed of 7 exons and 6 introns. Steady-state level of CRASH mRNA was found to be increased in 5 cell lines derived from metastatic lesions compared with 2 cell lines derived from primary mammary carcinoma and HMEC (human mammary epithelial cells). We found that the mRNA level of CRASH correlates with the metastatic propensity of several isogenic human colon cancer and pancreatic carcinoma cell lines. CRASH corresponds to a recently identified sperm autoantigen and furthermore we have demonstrated inducibility of CRASH mRNA by androgen and progesterone. Investigation of several types of human cancers and their corresponding normal tissues revealed high levels of CRASH mRNA in uterine, mammary and ovarian tumors compared with the corresponding normal tissues. CRASH mRNA expression was analysed in breast cancer samples with disclosed clinico-pathological features and corresponding normal tissues. The levels of CRASH mRNA were significantly up-regulated in tumors compared with normal breast tissues and correlate with lack of estrogen receptor expression of the tumors.     

结直肠肿瘤中sFRP基因的甲基化及表达调控

目的探讨分泌型卷曲相关蛋白(sFRP)家族基因启动子CpG岛甲基化在结直肠肿瘤发生、发展中的作用。方法应用5-氮杂-2’-脱氧胞苷(DAC)和曲古菌素A(TSA)对结直肠癌细胞系RKO、HCT116和SW480进行去甲基化处理。甲基特异性PCR和逆转录PCR分别检测结直肠肿瘤组织及细胞系中sFRP基因甲基化和mRNA表达。结果正常大肠黏膜不存在sFRP基因甲基化。sFRP1、sFRP2和sFRP5在结直肠腺癌、腺瘤和异常隐窝灶(ACF)中均存在高频率甲基化,sFRP1甲基化率>85%,sFRP2甲基化率>75%,sFRP5甲基化率>50%,腺癌、腺瘤和ACF间sFRP基因甲基化率差异无统计学意义(P>0.05),但均高于正常黏膜及瘤旁正常组织(P<0.05)。3种结直肠癌细胞系RKO、HCT116和SW480均存在sFRP基因甲基化,甲基化的sFRP基因mRNA失表达。联合使用DAC和TSA能有效恢复结直肠癌细胞系的sFRP基因表达。结论在ACF中,sFRP基因家族已出现高频率甲基化,是结直肠肿瘤发生常见的早期事件,sFRP1、sFRP2和sFRP5甲基化可能成为早期发现结直肠肿瘤的生物学标志。去甲基化能有效恢复基因表达,可能成为治疗肿瘤的有效手段。     

Increased expression of interleukin-1alpha and cyclooxygenase-2 in human gastric cancer: a possible role in tumor progression

BACKGROUND: Cyclooxygenase (COX)-2 mRNA and protein expression have been found to be frequently up-regulated in human gastric cancers and cell lines. COX-2 is the inducible form of COX, and interleukin (IL)-1alpha may be one of the stimulators of COX-2. MATERIALS AND METHODS: The relationship between IL-1alpha and COX-2 expression was examined in human gastric cancer tissues and cell lines. RESULTS: IL-1alpha mRNA was expressed in 19 out of 32 human gastric cancer specimens (60%), while it was not expressed in any of the paired normal gastric mucosa specimens. The incidence of IL-1alpha mRNA expression was significantly higher in patients with pT2-pT4 tumors than in those with pT1 tumors (86% vs. 39%, p<0.05). IL-1alpha mRNA was expressed in 94% of COX-2-positive tumors, while it was expressed in only 25% of COX-2-negative tumors (p<0.0001). When IL-1alpha was added to the medium of gastric cancer cell lines (MKN28 and MKN45), it enhanced the expression of IL-1alpha itself and COX-2 mRNA in both cell lines. Exogenous IL-1alpha stimulated cancer cell growth in both cell lines, while such growth stimulation was suppressed by anti-IL-1alpha antibody or IL-1 receptor antagonist. IL-1alpha-stimulated cell growth was also suppressed by anti-COX-2 antibody. CONCLUSION: Our data demonstrated that IL-1alpha and COX-2 mRNA were frequently co-expressed in human gastric cancer tissues, and suggested that the IL-1alpha-COX-2 pathway might be involved in tumor progression by regulating cancer cell proliferation.     

膀胱癌中nm23-H1基因突变及表达的意义

目的：探讨ｎｍ２３－Ｈ１基因在膀胱癌中突变及表达的意义。方法：应用半定量逆转录聚合酶链反应（ＲＴ－ＰＣＲ）和银染单链构象多态性（ＳＳＣＰ）方法检测ｎｍ２３－Ｈ１基因在２５例膀胱癌组织及１５例对照组织中突变和表达情况。结果：对照粘膜中未检测出ｎｍ２３－Ｈ１基因突变,而在２５例膀胱癌组织中发现６例出现ＰＣＲ产物单链泳动状态异常,异常率为２４％。癌组织和对照组织均有ｎｍ２３－Ｈ１基因ｍＲＮＡ的表达,８８