Abstract
BackgroundAccurate staging of rectal tumors is essential for making the correct treatment choice. In a previous study, we found that loss of 17p, 18q and gain of 8q, 13q and 20q could distinguish adenoma from carcinoma tissue and that gain of 1q was related to lymph node metastasis. In order to find markers for tumor staging, we searched for candidate genes on these specific chromosomes.MethodsWe performed gene expression microarray analysis on 79 rectal tumors and integrated these data with genomic data from the same sample series. We performed supervised analysis to find candidate genes on affected chromosomes and validated the results with qRT-PCR and immunohistochemistry.ResultsIntegration of gene expression and chromosomal instability data revealed similarity between these two data types. Supervised analysis identified up-regulation of EFNA1 in cases with 1q gain, and EFNA1 expression was correlated with the expression of a target gene (VEGF). The BOP1 gene, involved in ribosome biogenesis and related to chromosomal instability, was over-expressed in cases with 8q gain. SMAD2 was the most down-regulated gene on 18q, and on 20q, STMN3 and TGIF2 were highly up-regulated. Immunohistochemistry for SMAD4 correlated with SMAD2 gene expression and 18q loss.ConclusionOn basis of integrative analysis this study identified one well known CRC gene (SMAD2) and several other genes (EFNA1, BOP1, TGIF2 and STMN3) that possibly could be used for rectal cancer characterization.
Highlights
Accurate staging of rectal tumors is essential for making the correct treatment choice
The carcinoma tissue was subdivided into tumor fractions consisting of a mixture of adenoma and carcinoma tissue (AC/C), carcinomas without lymph node metastasis (C/ C) and carcinomas with lymph node metastasis (C/C (N+))
While some studies reported a direct correlation between gene expression and chromosomal aberrations [16,17,19,48], others reported that amplification does not necessarily lead to expression up-regulation[20]
Summary
Accurate staging of rectal tumors is essential for making the correct treatment choice. We found that loss of 17p, 18q and gain of 8q, 13q and 20q could distinguish adenoma from carcinoma tissue and that gain of 1q was related to lymph node metastasis. Accurate staging of rectal tumors is essential for choosing the correct treatment. Small pedunculated adenomas can be removed by snare excision, while large sessile adenomas can be cured by transanal endoscopic microsurgery [1]. Total mesorectal excision with preoperative radiotherapy is the gold standard [2]. It is of utmost importance to have parameters that can discriminate large benign adenomas from adenomas with a small invasive focus, as well as carcinomas with and without lymph node metastasis
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