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Medical AI Inquiry: You was designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.  Labels: OBJECTIVE, METHODS, RESULTS. Meshes: Cell Line, Tumor, Colorectal Neoplasms, DNA Methylation, Gene Expression, Gene Expression Regulation, Neoplastic, Genes, Tumor Suppressor, Humans, Immunohistochemistry, Insulin-Like Growth Factor Binding Proteins, Oligonucleotide Array Sequence Analysis, RNA, Messenger, Reverse Transcriptase Polymerase Chain Reaction, Sequence Deletion.
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Is decreased expression of insulin-like growth factor binding protein 7 in human colorectal carcinoma related to DNA methylation? Context: Insulin-like growth factor binding protein 7 (IGFBP-7) is considered a tumor suppressor in various cancers, but its role in colorectal cancer (CRC) is still uncertain. The aims of this study were to analyze the IGFBP-7 expression, and explore the mechanism responsible for the inactivation of IGFBP-7 in CRC. mRNA expression was studied by RT-PCR and Northern blot analysis of cultured cells. Methylation status was analyzed by treatment with 5-aza-2'-deoxycytidine followed by sequencing of PCR products of sodium bisulfite-treated genomic DNA. IGFBP-7 protein expression was evaluated by immunohistochemistry (IHC) on tissue microarrays. mRNA expression was lost in six out of eight CRC cell lines as compared to normal colon cells. DNA methylation was found in the region of exon 1 and intron 1 of IGFBP-7. In tumor tissue, 107 out of 279 samples showed a negative expression of IGFBP-7 by IHC, which was significantly associated with poor prognosis. The analysis of 37 paired cancerous and normal mucosa samples confirmed the downregulation in the tumors, but revealed variable basal expression levels of IGFBP-7 in normal mucosal samples.
assistant
DNA methylation is a mechanism responsible for IGFBP-7 gene silencing providing a target for therapeutic intervention of this tumor suppressor gene. Final Decision: yes