| Budget Amount *help |
¥2,900,000 (Direct Cost: ¥2,900,000)
Fiscal Year 2006: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 2005: ¥1,500,000 (Direct Cost: ¥1,500,000)
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| Research Abstract |
How gene expression is regulated by tissue environment remains largely unknown. The aims of this study are to demonstrate the feasibility of chromosome-level analysis of gene expression and to clarify how the mode of gene expression regulation alters during tumor progression, using gastroesophageal carcinomas. We detected chromosomal regions of differential gene expression and altered genomic dosage by comparative expressed sequence hybridization (CESH) and comparative genomic hybridization(CGH), respectively, in esophageal squamous cell carcinoma (ESCC) cell lines and in multiple frozen samples from individual early and advanced ESCC and from undifferentiated-type gastric carcinomas. We firstly optimised RNA preparation, labelling and amplification in CESH. Using KYSE410 cells, we then showed that the regions of negative induction (downregulation without genomic loss) and negative compensation (of genomic gain to the normal expression level) partly showed upregulation after treatments
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with 5-Aza-2'-deoxycytidine and trichostatin A, respectively. Hypoxia and elevated FBS concentration in culture medium induced upregulation of specified chromosomal regions. In primary tumors, induction of gene expression and compensation of altered gene dosage were common at chromosome level in early cancer and the superficial part of advanced cancers, respectively. In the deep part, these changes reduced and dosage-dependent (CESH/CGH concordant) gene expression increased. At gene level, CDH1 genomic loss was compensated in superficial part and this compensation was lost in deep part in some advanced ESCCs. Promoter methylation accumulated during tumor progression and may cause loss of compensation. These findings suggest that there are gene clusters spanning large regions in chromosome under common epigenetic and/or environmental regulations and have demonstrated stepwise acquisition of autonomy of growth through stage-related inactivation of CDH1 and large-scale, genomic dosage-dependent gene expression during progression of primary ESCCs. The CESH/CGH approach is suitable for direct overview of large-scale changes in gene expression regulation and can be complementary to the microarray-based approach. Less
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