Abstract
BackgroundIt is known that alpha-defensin expression is enhanced in colon cancer. However, the expression of human alpha defensin 6 (DEFA 6) in earlier stages, such as adenoma, has so far not yet been studied in a patient resolved manner.MethodsBy using quantitative Real Time-PCR, the gene expression pattern of DEFA 1-3 and DEFA 6 was analyzed in tissue of different stages of carcinogenesis, derived from colorectal cancer patients. In addition to paired normal and tumor tissue, matched normal near tumor and adenoma tissue samples were examined.ResultsThe median gene expression of human defensin alpha 6 (DEFA 6) has been found to be moderately increased (~ 5 fold) in tumor samples derived from individuals with colorectal cancer (CRC) when compared to their normal counterparts. However, when the data were analyzed in a patient-wise manner, a large expression variation among individual patients is found, making the use of DEFA 6 for individual diagnosis of fully blown colon carcinoma difficult. Surprisingly, in adenoma the gene expression analysis revealed a 100 fold increased median expression of DEFA 6 relative to normal colon tissue. 13/18 samples had an individual overexpression of more than 60 fold in adenoma but only 3/17 in carcinoma. In each of the individual patients, at least either the adenoma or the carcinoma showed strong DEFA 6 overexpression.ConclusionsWe suggest that the expression of DEFA 6 preferably can be used as a potential diagnostic marker for adenoma and not as a marker for fully blown carcinoma. This is supported by the fact that DEFA 6 is a downstream target of the Wnt pathway, which is mutational active during the earliest stage of cancer development.
Highlights
It is known that alpha-defensin expression is enhanced in colon cancer
Since the gene expression analysis of fully blown carcinoma does not account for the expression alterations that are critical for the initiation and the development of cancer, in addition to the classical combination of paired normal and tumor tissue, matched normal near tumor and adenoma tissue samples were examined by qRT-polymerase chain reaction (PCR)
Low abundance of DEFA 1-3 expression in colon tissues The expression of DEFA 1-3 genes was investigated in normal and the related normal near tumor, benign adenoma and tumor tissue samples derived from 17 patients in total
Summary
It is known that alpha-defensin expression is enhanced in colon cancer. The expression of human alpha defensin 6 (DEFA 6) in earlier stages, such as adenoma, has so far not yet been studied in a patient resolved manner. Human neutrophilic (DEFA 1-3) and enteric (DEFA 6) alpha defensins are cationic short peptides of 29 to 42 amino acids in length with known functional activities in innate antimicrobial immunity [1,2,3]. As. This study attempts to test whether DEFA 6 can be used as marker of the adenoma stage of colon cancer and not solely, as already described in literature, as a marker of fully blown colorectal cancer. CDNA synthesis was performed as described earlier [13]. Due to the variability of the quantity of the extracted total RNA, the amount used as an initial material for the performance of the cDNA synthesis varied (ranged from 10 ng to 300 ng total RNA)
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