Decreased expression of 17β-hydroxysteroid dehydrogenase type 1 is associated with DNA hypermethylation in colorectal cancer located in the proximal colon

<p>Abstract</p> <p>Background</p> <p>The importance of 17β-estradiol (E2) in the prevention of large bowel tumorigenesis has been shown in many epidemiological studies. Extragonadal E2 may form by the aromatase pathway from androstenedione or the sulfatase pathway from estrone (E1) sulfate followed by E1 reduction to E2 by 17-β-hydroxysteroid dehydrogenase (HSD17B1), so <it>HSD17B1 </it>gene expression may play an important role in the production of E2 in peripheral tissue, including the colon.</p> <p>Methods</p> <p><it>HSD17B1 </it>expression was analyzed in colorectal cancer cell lines (HT29, SW707) and primary colonic adenocarcinoma tissues collected from fifty two patients who underwent radical colon surgical resection. Histopathologically unchanged colonic mucosa located at least 10-20 cm away from the cancerous lesions was obtained from the same patients. Expression level of <it>HSD17B1 </it>using quantitative PCR and western blot were evaluated. DNA methylation level in the 5' flanking region of <it>HSD17B1 </it>CpG rich region was assessed using bisulfite DNA sequencing and HRM analysis. The influence of DNA methylation on HSD17B1 expression was further evaluated by ChIP analysis in HT29 and SW707 cell lines. The conversion of estrone (E1) in to E2 was determined by electrochemiluminescence method.</p> <p>Results</p> <p>We found a significant decrease in HSD17B1 transcript (<it>p </it>= 0.0016) and protein (<it>p </it>= 0.0028) levels in colorectal cancer (CRC) from the proximal but not distal colon and rectum. This reduced <it>HSD17B1 </it>expression was associated with significantly increased DNA methylation (<it>p </it>= 0.003) in the CpG rich region located in the 5' flanking sequence of the <it>HSD17B1 </it>gene in CRC in the proximal but not distal colon and rectum. We also showed that 5-dAzaC induced demethylation of the 5' flanking region of <it>HSD17B1</it>, leading to increased occupation of the promoter by Polymerase II, and increased transcript and protein levels in HT29 and SW707 CRC cells, which contributed to the increase in E2 formation.</p> <p>Conclusions</p> <p>Our results showed that reduced <it>HSD17B1 </it>expression can be associated with DNA methylation in the 5' flanking region of <it>HSD17B1 </it>in CRC from the proximal colon.</p

Familial polyposis coli - inducing mutations in APC gene in Poland

Screening for molecular changes within the adenomatous polyposis coli (APC) gene, exons 11-14 and the 5’ half of exon 15, encompassing the mutation cluster region within exon 15, was performed in 30 patients with Familial Polyposis Coli (FAP). All patients were studied by heteroduplex analysis (HA) and single strand conformation polymorphism (SSCP) and molecular changes were found in 7 cases. Protein truncation test (PTT) has been performed in 17 cases in which mutations have not been found earlier, and shortening of protein product was noted in 2 cases. In three cases common deletion of 5 bp at codon 1309 and in one 5 bp deletion at codon 1061 were found. In other cases the molecular changes were demonstrated as heteroduplexes in exon 14 (1 patient), in segments E and F (one patient each) of exon 15, and in two cases the heteroduplexes were within the overlapping sequences of segments E/F and F/G of exon 15, respectively. In families where the molecular changes were found by HA, 7 persons at high risk for FAP were found and advised to undergo regular endoscopic examinations. In three persons at risk the transfer of mutation was excluded