Aberrations of A Putative Tumor Suppressor Gene Sel1L In Pancreatic Ductal Adenocarcinoma

<p><strong>Introduction:</strong> Pancreatic cancer is the fourth leading cause of cancer-related death among males and females in the United States. <em>Sel-1-like </em>(<em>SEL1L</em>) is a putative tumor suppressor gene that is downregulated in a significant proportion of human pancreatic ductal adenocarcinoma (PDAC). It was hypothesized that <em>SEL1L</em> expression could be down-modulated by somatic mutation, loss of heterozygosity (LOH), CpG island hypermethylation and/or aberrantly expressed microRNAs (miRNAs).</p> <p><strong>Material and methods: </strong>In 42 PDAC tumors, the <em>SEL1L</em> coding region was amplified using reverse transcription polymerase chain reaction (RT-PCR), and analyzed by agarose gel electrophoresis and sequenced to search for mutations. Using fluorescent fragment analysis, two intragenic microsatellites in the <em>SEL1L</em> gene region were examined to detect LOH in a total of 73 pairs of PDAC tumors and normal-appearing adjacent tissues. Bisulfite DNA sequencing was performed to determine the methylation status of the <em>SEL1L</em> promoter in 41 PDAC tumors and 6 PDAC cell lines. Using real-time quantitative PCR, the expression levels of <em>SEL1L</em> mRNA and 7 aberrantly upregulated miRNAs that potentially target <em>SEL1L</em> were assessed in 42 PDAC tumor and normal pairs. Statistical methods were applied to evaluate the correlation between <em>SEL1L</em> mRNA and the miRNAs. Further the interaction was determined by functional analysis using a molecular biological approach.</p> <p><strong>Results:</strong> No mutations were detected in the <em>SEL1L</em> coding region. More than 50% of the samples displayed abnormally alternate or aberrant spliced transcripts of <em>SEL1L</em>. About 14.5% of the tumors displayed LOH at the CAR/CAL microsatellite locus and 10.7% at the RepIN20 microsatellite locus. However, the presence of LOH did not show significant association with <em>SEL1L</em> downregulation. No methylation was observed in the <em>SEL1L</em> promoter. Statistical analysis showed that <em>SEL1L</em> mRNA expression levels significantly and inversely correlated with the expression of hsa-mir-143, hsa-mir-155, and hsa-mir-223. Functional analysis indicated that hsa-mir-155 acted as a suppressor of <em>SEL1L</em> in PL18 and MDAPanc3 PDAC cell lines.</p> <p><strong>Discussion:</strong> Evidence from these studies suggested that <em>SEL1L </em>was possibly downregulated by aberrantly upregulated miRNAs in PDAC. Future studies should be directed towards developing a better understanding of the mechanisms for generation of aberrant <em>SEL1L</em> transcripts, and further analysis of miRNAs that may downregulate <em>SEL1L</em>.</p>

Name thesis:degree_name

Doctor of Philosophy (PhD)

Level thesis:degree_level

Dissertation (PhD)

Year dc:date.available

2011

Author dc:creator

• Liu, Qian

Contributors dc:contributor

• Marsha L. Frazier
• Ann M. Killary
• Christopher Amos

• pancreatic cancer
• tumor suppressor gene
• SEL1L
• pancreatic ductal adenocarcinoma
• loss of heterozygosity
• methylation
• mutation
• aberrant splicing
• microRNA
• Medical Cell Biology
• Medical Genetics
• Medicine and Health Sciences

Repository record dc:identifier

https://digitalcommons.library.tmc.edu/utgsbs_dissertations/178

OAI identifier oai:identifier

oai:digitalcommons.library.tmc.edu:utgsbs_dissertations-1209