3rd Annual BMRP Investigator Meeting - Abstract
HLA Typing and Expression: Marker for Identifying Dysplasia and Stratifying the Risk for IBD-Cancer
Megan Garrity, S. Breanndan Moore, William Sandborn, Vernon Pankratz, Edward Loftus and Thomas Smyrka
Department of Lab Medicine and Pathology, Mayo Clinic Rochester (Rochester, Minnesota, U.S.A.)
Background: Linkage analysis/twin studies of chronic ulcerative colitis (CUC) show linkage to chromosome 6, which contains both the HLA Class I/Class II genes (T-cell mediators) and the tumor necrosis factor-alpha (TNF-α) gene (inflammatory response). CUC is characterized by chronic mucosal inflammation as well as an increased risk for colon cancer (CRC). Therefore, these genes are attractive targets to investigate CUC/CRC pathogenesis in a highly selected patient population.
Experimental Design: Identify Patients and Create Database Infrastructure: We will do an extensive chart review of patients to extract, among other things, age, race, gender and duration/extent of disease. Control groups will be carefully matched to avoid the issues involved in associative studies of heterogeneous disease states. Only patients with confirmed diagnostic details (³10 years CUC, previously documented biopsy data, etc.) will be selected for histological confirmation and testing. We will also extract patient social/family history details to highlight additional gene targets and environmental contributory factors.
Molecular and Immunohistochemical (IHC) Testing: DNA extracted from the archived formalin-fixed, paraffin embedded blocks of 125 CUC/CRC cases and controls will be used for HLA A, B, DR and DQ genotyping and TNF- α gene amplification for single nucleotide polymorphism (SNP) analysis. Sections (from normal, dysplasia, CRC blocks) will be cut to investigate T-cell patterns (CD4, CD8, naïve and memory) and HLA/TNF-α expression by IHC.
Future Direction: All experimental results on this highly selected group of patients will be correlated with patient information to investigate whether: a) certain HLA types/TNF-α SNPs are predictive of CRC risk, b) alterations in HLA/TNF-α expression in situ are indicative of early changes from normal to dysplasia/cancer; and c) there is a pro-inflammatory genetic profile that stratifies patients at greatest risk for CRC. In addition, the database created will serve as an invaluable tool to explore the epidemiological components of CUC and will facilitate the rapid investigation of other as yet unidentified markers.
aPrincipal Investigator