Tyrosine-kinase expression profiles in human gastric cancer cell lines and their modulations with retinoic acids

Hw, Kao; Hc, Chen; Cw, Wu; Lin, Wen-chang

doi:10.1038/sj.bjc.6600821

Cited by 18 publications

(13 citation statements)

References 34 publications

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“…cDNA was prepared from human and mouse cell lines as described previously (17). Total RNA (10 g) from cell lines was used as the template for cDNA preparation in a 20-l reaction mixture.…”

Section: Methodsmentioning

confidence: 99%

Wobble Splicing Reveals the Role of the Branch Point Sequence-to-NAGNAG Region in 3′ Tandem Splice Site Selection

Tarn

Lin

2007

Molecular and Cellular Biology

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Alternative splicing involving the 3 tandem splice site NAGNAG sequence may play a role in the structurefunction diversity of proteins. However, how 3 tandem splice site utilization is determined is not well understood. We previously demonstrated that 3 NAGNAG-based wobble splicing occurs mostly in a tissueand developmental stage-independent manner. Bioinformatic analysis reveals that the nucleotide preceding the AG dinucleotide may influence 3 splice site utilization; this is also supported by an in vivo splicing assay. Moreover, we found that the intron sequence plays an important role in 3 splice site selection for NAGNAG wobble splicing. Mutations of the region between the branch site and the NAGNAG 3 splice site, indeed, affected the ratio of the distal/proximal AG selection. Finally, we found that single nucleotide polymorphisms around the NAGNAG motif could affect the splice site choice, which may lead to a change in mRNA patterns and influence protein function. We conclude that the NAGNAG motif and its upstream region to the branch point sequence are required for 3 tandem splice site selection.Introns of precursor mRNA are removed by splicing, and exons are ligated to form mature mRNAs, which can be translated to produce proteins (15, 27). In higher eukaryotes, the essential cis elements of an intron include the 5Ј splice site (GT), the branch point sequence (BPS), the polypyrimidine tract (PPT), and the 3Ј splice site (AG) (5). The splicing reaction involves two catalytic steps, as follows: (i) the branch point attacks the 5Ј splice site to generate the splicing intermediates, and (ii) the released 5Ј exon attacks at the 3Ј splice site to generate the ligated exons and lariat intron. These two steps occur in the spliceosome complex containing five small nuclear RNAs (U1, U2, U4/U6, and U5) and more than 150 protein factors (12,28,30). Recognition of the splice sites needs to be precise and involves an interaction between the cis elements and trans-acting factors (23).Alternative splicing has recently emerged as a major mechanism of posttranscriptional regulation in the human genome and occurs in Ͼ60% of human genes (3); the high frequency of this alternative splicing in human is supported by expressed sequence tag (EST)-based database analysis (4, 16). Recently, Wen et al. (38) reported that very short alternative splicing in the human genome might alter protein structures and thus influence protein function. A subtle variation of transcripts may come from wobble splicing at the 5Ј splice site GTNGT or the 3Ј splice site NAGNAG sequence, thus creating singleamino-acid insertion and deletion (InDel) isoforms (22, 35).Recently, Hiller et al. (14) and Tadokoro et al. (34) also demonstrated genome-wide distribution of the NAGNAG sequence at the 3Ј splice site in human genes, which results in protein isoforms with one amino acid insertion or deletion. Such wobble splicing is predicted to exist in 30% of human genes and is active in at least 5% of genes, according to an EST database search. Although wobble s...

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“…cDNA was prepared from human and mouse cell lines as described previously (17). Total RNA (10 g) from cell lines was used as the template for cDNA preparation in a 20-l reaction mixture.…”

Section: Methodsmentioning

confidence: 99%

Wobble Splicing Reveals the Role of the Branch Point Sequence-to-NAGNAG Region in 3′ Tandem Splice Site Selection

Tarn

Lin

2007

Molecular and Cellular Biology

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“…Although many reports (Hirai et al, 1987;Maru et al, 1990;Robinson et al, 1996;Kao et al, 2003) have shown upregulation of EphA1 in CRCs, and more recently downregulation, mechanisms of downregulation have not been examined (Hafner et al, 2006). In seeking a mechanism for EphA1 downregulation, epigenetic silencing due to methylation analysis of a CpG island in the EphA1 gene was investigated.…”

Section: Epha1 Promoter Methylation Inversely Correlates With Epha1 Ementioning

confidence: 99%

“…In mice, EphA1 is expressed in many epithelial tissues including skin, kidney, liver and thymus (Coulthard et al, 2001). Over-expression of human EphA1 has been observed in prostate, gastric and colon carcinomas (Hirai et al, 1987;Maru et al, 1990;Robinson et al, 1996;Kao et al, 2003). More recently, significant downregulation of EphA1 was reported in non-melanoma skin cancers (Hafner et al, 2006).…”

mentioning

confidence: 99%

Epigenetic silencing of EphA1 expression in colorectal cancer is correlated with poor survival

et al. 2009

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Aberrant expression of Eph and ephrin proteins has well-established functions in oncogenesis and tumour progression. We describe EphA1 expression in 6 colorectal cancer (CRC) cell lines, 18 controls and 125 CRC specimens. In addition, a well-characterised cohort of 53 paired normal colon and CRCs was also assessed. Expression of EphA1 mRNA was assessed by quantitative real-time PCR and correlated with protein expression by flow cytometry, immunoprecipitation, western blotting and immunohistochemistry. Significant upregulation (2-to 10-fold) of EphA1 was seen in over 50% of cases (P ¼ 0.005) whereas many of the remainder showed downregulation of EphA1. Intriguingly, EphA1 over-expression was more prevalent in stage II compared to stage III CRCs (P ¼ 0.02). Low EphA1 expression significantly correlated with poor survival (P ¼ 0.02). Epigenetic silencing appeared to explain the loss of EphA1 expression as methylation of the EphA1 CpG island strongly correlated with low EphA1 expression (Po0.01). Furthermore, EphA1 re-expression could be induced by treatment with demethylating agents. Our findings identify EphA1 as a potential prognostic marker in CRC. Although therapies targeting high EphA1 expression seem plausible in CRC, the loss of expression in advanced disease suggests a potential risk that targeted therapy, by selecting for loss of expression, might contribute to disease progression.

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“…Genetic and epigenetic alterations play important roles in the development and progression of gastric cancer [1,2] . Considerable attention has been given to the potential role of tyrosine kinases in gastric cancer [3][4][5][6] . The Ephrin (Eph) receptors constitute the largest family of tyrosine kinase receptors [7][8][9][10] .…”

Section: Introductionmentioning

confidence: 99%

Overexpression of the receptor tyrosine kinase EphA4 in human gastric cancers

Oki¹,

Yamamoto²,

Taniguchi³

et al. 2008

WJG

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recurrence. EphA4 overexpression was also correlated with FGFR1 overexpression. Patients with EphA4-positive cancer had significantly shorter overall survival periods than did those with EphA4-negative cancer (P = 0.0008). The mRNAs for ephrin ligands were coexpressed in various combinations in gastric cancer cell lines and cancer tissues. Downregulation of EphA4 expression by siRNA in EphA4-overexpressing gastric cancer cell lines resulted in a significant decrease in cell growth. CONCLUSION: Our results suggest that overexpression of EphA4 plays a role in gastric cancer.

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Tyrosine-kinase expression profiles in human gastric cancer cell lines and their modulations with retinoic acids

Cited by 18 publications

References 34 publications

Wobble Splicing Reveals the Role of the Branch Point Sequence-to-NAGNAG Region in 3′ Tandem Splice Site Selection

Wobble Splicing Reveals the Role of the Branch Point Sequence-to-NAGNAG Region in 3′ Tandem Splice Site Selection

Epigenetic silencing of EphA1 expression in colorectal cancer is correlated with poor survival

Overexpression of the receptor tyrosine kinase EphA4 in human gastric cancers

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