Title: A New Model of Gastric Bleeding in Rats Using Co-Administration of Aspirin Plus Clopidogrel Under Stimulation of Acid Secretion: Prophylactic Effects of Antiulcer Drugs
Abstract: in the thyroid but has not been shown to have a role as a tumor suppressor gene.Hypothesis: To determine the frequency of RET methylation in colorectal adenomas and cancers and to determine if RET may be a conditional tumor suppressor gene in CRC.Methods: Genomic DNA was extracted from colon tissues and subjected to methylation specific PCR (MSP).Quantitative RT-PCR was performed using TaqMan On-Demand primers and probes.Colorectal cancer cell lines were transfected with vectors containing RET. Cell death was analyzed using the Cell Death Detection ELISA assay and the Caspase-Glo 3/7 Assay.Results: Aberrantly methylated RET was found in 7% of normal colon (N=14), 0% of early adenomas (N=8), 30% of advanced adenomas (N=10), and 69% of CRCs (N=16).RET expression was low in CRC cell lines with methylated RET and could be induced by treatment with 5-AZA.RET expression was higher in normal colon mucosa and early adenomas, compared with CRCs.GDNF was present in normal colon and adenomas but not CRCs.RET caused induction of apoptosis in cell lines with methylated RET, which was blocked by GDNF.Conclusion: RET is aberrantly methylated in colon adenomas and CRCs and is more frequently aberrantly methylated in CRCs, suggesting RET inactivation is involved in the progression of CRC.RET expression is low in CRC cell lines with methylated RET genes, and GDNF expression is absent in these cell lines, suggesting that loss of GDNF creates a selective pressure for inactivating RET.Consistent with this concept, reconstitution with RET leads to increased apoptosis, which can be suppressed by GDNF.Our results are consistent with RET behaving as a conditional tumor suppressor gene in CRC. 1137