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Sana Yokoi

Publications and source records attributed to Sana Yokoi.

11 recordsLinked to original sources
PubMed2006

Frequent silencing of the candidate tumor suppressor PCDH20 by epigenetic mechanism in non-small-cell lung cancers.

Protocadherins are a major subfamily of the cadherin superfamily, but little is known about their functions and intracellular signal transduction. We identified a homozygous loss of protocadherin 20 (PCDH20, 13q21.2) in the course of a program to screen a panel of non-small-cell lung cancer (NSCLC) cell lines (1 of 20 lines) for genomic copy number aberrations using an in-house array-based comparative genomic hybridization. PCDH20 mRNA was expressed in normal lung tissue but was not expressed in the majority of NSCLC cell lines without a homozygous deletion of this gene (10 of 19 lines, 52.6%). Expression of PCDH20 mRNA was restored in gene-silenced NSCLC cells after treatment with 5-aza 2'-deoxycytidine. The DNA methylation status of the PCDH20 CpG-rich region correlated inversely with the expression of the gene and a putative target region for methylation showed clear promoter activity in vitro. Methylation of this PCDH20 promoter was frequently observed in primary NSCLC tissues (32 of 59 tumors, 54.2%). Among our primary NSCLC cases, the methylated PCDH20 seemed to be associated with a shorter overall survival (P = 0.0140 and 0.0211 in all and stage I tumors, respectively; log-rank test), and a multivariate analysis showed that the PCDH20 methylation status was an independent prognosticator. Moreover, restoration of PCDH20 expression in NSCLC cells reduced cell numbers in colony formation and anchorage-independent assays. These results suggest that epigenetic silencing by hypermethylation of the CpG-rich promoter region of PCDH20 leads to loss of PCDH20 function, which may be a factor in the carcinogenesis of NSCLC.

Aged↗
PubMed2005

Frequent silencing of DBC1 is by genetic or epigenetic mechanisms in non-small cell lung cancers.

Genome-wide screening of DNA copy number aberrations in 27 cell lines derived from non-small cell lung cancers (NSCLCs), using a custom-made comparative genomic hybridization (CGH)-array, identified a homozygous deletion of the deleted in bladder cancer 1 gene (DBC1) in one cell line. Homozygous deletion of DBC1, located at 9q33.1, was also observed in two of 53 primary NSCLC tumors examined. Moreover, 21 of the other 26 cell lines showed complete loss of DBC1 expression, although normal lung tissues express this gene, and treatment with 5-aza-2'-deoxycytidine restored expression of DBC1. Hypermethylation in part of a CpG island around the exon 1 of DBC1 has been reported in urothelial cancers, but the potential association between methylation and expression status was never clarified in that disease. In our experiments, a different part of the same CpG island showed promoter activity in vitro and was frequently methylated in our cell lines and primary tumors of NSCLC, where methylation status correlated inversely with gene expression. Among our primary NSCLC cases, methylation of the DBC1 promoter occurred more frequently in men, elderly patients and smokers than in women, younger patients and nonsmokers respectively, but it was not correlated with tumor stage or histology. Exogenous overexpression of DBC1 in NSCLC cell lines lacking its expression inhibited cell growth. Our results provide the first evidence that DBC1 is a likely tumor suppressor for NSCLC; silencing of the gene through homozygous deletion or methylation of its promoter region may be associated with progression of this disease.

Aged↗
PubMed2005

Overexpressed Skp2 within 5p amplification detected by array-based comparative genomic hybridization is associated with poor prognosis of glioblastomas.

To better understand the pathogenesis of glioblastoma multiforme (GBM) and to increase the accuracy of predicting outcomes for patients with this disease, we performed genome-wide screening for DNA copy-number aberrations in 22 glioma-derived cell lines using a custom-made comparative genomic hybridization-array. Copy-number gains were frequently detected at 3q, 7p, 7q, 20q, Xp and Xq, and losses at 4q, 9p, 10p, 10q, 11q, 13q, 14q, 18q, and 22q. Among several non-random chromosomal aberrations, the gain/amplification of DNA at 5p, which has never been reported before in GBM, was detected with a relatively high ratio (log2 ratio = 0.41-1.19) in four cell lines. Amplification and subsequent overexpression of SKP2, a possible target of amplification within 5p, were detected in four of the 22 cell lines. We also investigated the expression of the gene product in primary GBM by immunohistochemistry, which revealed increased levels of Skp2 in 11 of the 35 tumors examined (31.4%). Heightened expression of Skp2 was associated with shorter overall survival (P = 0.001, logrank test), especially in patients younger than 65 years. These results suggest that overexpression of Skp2 through gene amplification may contribute to the pathogenesis of GBM, and that overabundance of the protein might be a useful prognostic tool in patients with this disease.

Biomarkers, Tumor↗
PubMed2004

Overexpression of collagen XVIII is associated with poor outcome and elevated levels of circulating serum endostatin in non-small cell lung cancer.

PURPOSE: The aim of this study was to determine whether collagen XVIII expression is correlated with circulating serum endostatin and whether this has any prognostic value in patients with non-small cell lung cancer (NSCLC). EXPERIMENTAL DESIGN: Serum endostatin levels were measured quantitatively by a competitive enzyme immunoassay, and collagen XVIII expression in tumor tissue was investigated with an immunohistochemical method in a series of 94 patients who underwent surgery for NSCLC. RESULTS: Sixty cases (63.8%) had positive immunohistochemical staining with anticollagen XVIII polyclonal antibodies, including strongly positive staining in 11 (11.7%) cases. The mean (+/- SD) serum endostatin level was 41.6 +/- 34.4 ng/ml in the patient group and 16.3 +/- 10.3 ng/ml in the control group (P < 0.0001). The 11 cases who were strongly collagen XVIII-positive had significantly higher serum endostatin levels than the cases who were negative or weakly positive (P = 0.0297). The 5-year survival rates of negative, weakly positive, and strongly positive patients were 77.8%, 56.9%, and 43.8%, respectively. The cases with strongly positive collagen XVIII expression had a significantly poorer outcome than cases with negative expression (P = 0.0027). A multivariate analysis with Cox proportional hazards model for disease-specific survival revealed that expression of collagen XVIII (strongly positive versus negative; weakly positive versus negative), tumor classification, and regional lymph node classification were independent prognostic factors. CONCLUSIONS: Our results suggest that expression of collagen XVIII in tumor tissue is strongly associated with a poorer outcome in NSCLC and correlates with elevated levels of circulating serum endostatin.

Aged↗
PubMed2004

Correlation between interleukin 6 production and tumor proliferation in non-small cell lung cancer.

UNLABELLED: Interleukin 6 (IL-6) facilitates the differentiation of B cells to immunoglobulin-secreting cells and is reported to be a proliferative factor in some tumors. In this study, we examined IL-6 production in non-small cell lung carcinoma (NSCLC) and the proliferation of tumor cells following IL-6 treatment in vitro and in vivo. We analyzed the expression of IL-6 mRNA and protein in a series of 15 human lung cancer cell lines (four adenocarcinomas, five squamous cell carcinomas, two large cell carcinomas, and four small cell carcinomas) by reverse transcriptase polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA). We established an IL-6-producing cell line (ABC-1#IL-6) by transfecting a human IL-6 cDNA into a human non-IL-6-producing NSCLC cell line (ABC-1). These two cell lines were used to determine tumor cell proliferation both in vivo and in vitro in order to clarify the effect of IL-6 on tumor growth and metastasis. Athymic nude mice, SCID mice, and BALB/c mice were subcutaneously inoculated with these two cell lines, and body weight, tumor growth, and tumor doubling time were measured. The presence of IL-6 and tumor-infiltrating lymphocytes (TILs) within tumor tissues was examined by immunohistochemical staining. RESULTS: Eight of 15 (53%) lung cancer cell lines expressed both IL-6 mRNA and protein. Tumor lesions of both cell lines developed in nude and SCID mice, although no such lesions of either cell lines developed in BALB/c mice. The tumor doubling time in nude and SCID mice was 2.97+/-1.22 days and 2.45+/-1.32 days, respectively, in mice inoculated with the cell line ABC-1#IL-6. These doubling times were statistically significantly shorter than those evident in mice inoculated with the control original ABC-1 cell line (nude, p=0.0337; SCID, p=0.0119; unpaired t-test). The rates of cell proliferation in vitro of the ABC-1#IL-6 and original ABC-1 cells lines were comparable ( p=0.1441, unpaired t-test). Immunohistochemical staining revealed strong IL-6 expression in tumors derived from the IL-6-producing cell line but not in tumors derived from the original ABC-1 cell line (both in nude and SCID mice). CONCLUSION: 53% of lung cancer cell lines produce IL-6 mRNA and protein. Although IL-6 itself does not influence tumor cell proliferation in vitro, an association between IL-6 expression and tumor proliferation was found in vivo in nude and SCID mice. An anti-IL-6 reagent could provide a novel therapeutic strategy in patients with IL-6-producing lung tumors.

Adenocarcinoma↗
PubMed2004

Amplification and overexpression of SKP2 are associated with metastasis of non-small-cell lung cancers to lymph nodes.

SKP2, an F-box protein constituting the substrate recognition subunit of the SCF(SKP2) ubiquitin ligase complex, is implicated in ubiquitin-mediated degradation of the cyclin-dependent kinase inhibitor p27(KIP1). Our earlier studies revealed SKP2 as a target gene within the 5p13 amplicon that is often seen in small-cell lung cancers. In the present study we examined amplification status and expression levels of SKP2 in non-small-cell lung cancer (NSCLC) and investigated its clinicopathological significance in this type of tumor because amplification of DNA at 5p13 is observed frequently in NSCLCs as well as in small-cell lung cancers. SKP2 exhibited amplification in 5 (20%) of 25 cell lines derived from NSCLC, and the transcript was overexpressed in 11 (44%) of the 25 lines. Moreover, expression of SKP2 was up-regulated significantly in 60 primary NSCLC tumors as compared to nontumorous lung tissues (P < 0.0001). Elevated expression of SKP2 correlated significantly with positive lymph node metastasis (P = 0.007), with stage II or higher of the international TNM classification (P = 0.014), with poor or moderate differentiation (P < 0.001), and with the presence of squamous cell carcinoma (P = 0.037). Reduction of SKP2 expression by transfection of an anti-sense oligonucleotide inhibited invasion and migration of NSCLC cells in culture. Our results suggest that SKP2 may be involved in progression of NSCLC, and that targeting this molecule could represent a promising therapeutic option.

Blotting, Western↗
PubMed2004

Skp2 overexpression is a p27Kip1-independent predictor of poor prognosis in patients with biliary tract cancers.

To better understand the pathogenesis of biliary tract carcinoma (BTC) and to increase the accuracy of predicting outcomes for patients with this disease, we performed molecular cytogenetic analyses of BTC cell lines and tumors to identify non-random amplification(s) and target gene(s) within the amplicons. Among several non random chromosomal aberrations detected in BTC cell lines by comparative genomic hybridization, gain/ampli-fication of DNA at 5p was the most frequently observed alteration. We assessed the copy number and expression status of the possible target gene SKP2 for 5p amplification in cell lines and 33 primary stage II or III tumors of BTC. SKP2 was amplified, and subsequently overexpressed in both cell lines and primary tumors of BTC. However, levels of Skp2 and p27Kip1 proteins were not correlated inversely. Heightened expression of Skp2 and reduced expression of p27Kip1 were both associated with a shorter disease-free and/or overall survival in univariate analyses. In multivariate regression analyses, Skp2 and p27Kip1 were independent predictive factors. Those results suggest that (a) overexpression of Skp2 through an amplification mechanism may contribute to the progression of BTC, (b) not only each molecule, but also the combination of Skp2 and p27Kip1, might be a useful predictor of the prognosis of BTC, and (c) molecular targets of Skp2 other than p27Kip1 may also be important factors in the pathogenesis of this disease.

Aged↗
PubMed2003

TERC identified as a probable target within the 3q26 amplicon that is detected frequently in non-small cell lung cancers.

PURPOSE: Cell lines derived from non-small cell lung cancers (NSCLCs) revealed frequent high-level gains of chromosomal DNA at 3q23-q29 when examined by comparative genomic hybridization (CGH). Within this amplicon, a minimal common region of amplification in lung tumors had been mapped to 3q26 by earlier studies. The aim of the present work was to identify specific targets of the 3q26 amplification in NSCLCs. EXPERIMENTAL DESIGN: We examined genomic alterations in 19 NSCLC cell lines (10 derived from squamous cell carcinomas and 9 from adenocarcinomas) by using CGH and fluorescence in situ hybridization. We determined amplification and expression levels of four candidates (EVI1, TERC, SNO, and PIK3CA) in those cell lines and also in 25 primary NSCLC tumors. Because the TERC gene encodes the RNA component of human telomerase, we examined telomerase activity by the telomeric repeat amplification protocol (TRAP) assay. RESULTS: Copy numbers of EVI1 and TERC increased more than those of SNO and PIK3CA in our panel of NSCLC cell lines. Significant correlation between amplification and expression levels was observed only for TERC (P = 0.006), however, among these four candidate genes. Expression of TERC was also up-regulated in 24 (96%) of 25 primary NSCLC tumors compared with their nontumorous counterparts (P = 0.0001), and elevated expression of TERC was associated with high levels of telomerase activity (P = 0.048). CONCLUSIONS: TERC is a likely target of the 3q26 amplification, and, therefore, may be a useful biomarker for diagnosis and an attractive, novel target for molecular therapy of NSCLC.

Blotting, Northern↗
PubMed2003

Down-regulation of SKP2 induces apoptosis in lung-cancer cells.

S-Phase kinase associated protein 2 (SKP2), an F-box protein constituting the substrate-recognition subunit of the SCF(SKP2) ubiquitin ligase complex, targets cell-cycle regulators, such as the cyclin-dependent kinase inhibitor p27(KIP1), for ubiquitin-mediated degradation. Our earlier studies indicated frequent amplification and over-expression of the SKP2 gene in primary small-cell lung cancers (SCLCs) and cell lines derived from this type of tumor, and showed that down-regulation of SKP2 expression by means of an antisense oligonucleotide inhibited the growth of SCLC cells in culture (Yokoi et al., Am J Pathol, 161, 207-216, 2002). The antisense effect was confirmed in two cell lines of non-small cell lung cancer (NSCLC) that also exhibited over-expression of the gene. In the work reported here, we examined the mechanism(s) responsible for antisense-mediated growth inhibition of SCLC- and NSCLC-derived cultures. SKP2-antisense treatment not only suppressed DNA synthesis, as determined by [(3)H]thymidine incorporation, but also induced spontaneous apoptosis characterized by an increase in the sub-G1 population, fragmentation of nuclei, and activation of caspase-3. Our results suggest that since down-regulation of SKP2 appears to induce apoptosis in lung-cancer cells directly, targeting this molecule could represent a promising new therapeutic approach for this type of cancer, and possibly other tumors that over-express SKP2.

Apoptosis↗
PubMed2002

A novel target gene, SKP2, within the 5p13 amplicon that is frequently detected in small cell lung cancers.

We investigated DNA copy-number aberrations in 22 cell lines derived from small cell lung cancers (SCLCs) using comparative genomic hybridization. A minimal common region at 5p13, within the 5p11-p13 amplicon that was most frequently involved, harbored the CDH6, PC4, and SKP2 genes. These three genes showed amplification and consequent overexpression in the SCLC cell lines. SKP2 positively regulates progression of cell cycle by targeting several regulators, such as the cell-cycle inhibitor p27(KIP1), for ubiquitin-mediated degradation. SKP2 was amplified in 7 (44%) of 16 primary SCLC tumors, and consequently overexpressed in 10 (83%) of the 12 of those tumors we examined. Expression levels of SKP2 protein were cell cycle-dependent in SCLC cells as well as in normal cells, and were correlated with the DNA copy-number of the gene. There was an inverse correlation between the expression of SKP2 and p27(KIP1) proteins. Down-regulation of SKP2 using an anti-sense oligonucleotide remarkably suppressed the growth of SCLC cells. Our results indicate that SKP2 is likely to be a target of the 5p13 amplification and to play an important role in the growth of SCLC cells.

Carcinoma, Small Cell↗