Abstract
Background: The most commonly altered tumor suppressor gene in human cancers is TP53, which is inactivated by mutations and/or allelic loss (loss of heterozygosity, LOH). Inactivation of TP53 is highly predictive of cancer development in the pre-malignant condition Barett's Esophagus, the model system for assay construction in this thesis. Current methods for detecting both of these genetic alterations in any given sample are not clinically compatible because they require highly trained technicians capable of carrying out multi-step, time-consuming protocols on several pieces of expensive equipment Linear-After-The-Exponential (LATE)-PCR provides a practical means to combine boa) LOH detection and mutational sequence analysis in a single-tube assay. Results: The TP53 gene inactivation assay described here combines the rs4233018b SNP assay for 17p{TP53} LOH detection with amplification of TP53 exons 7/8 in a single LATE-PCR reaction. This duplex reaction successfully detects 17p LOH in a cell line derived from Barrett’s Esophagus biopsy at PCR end-point. The TP53 amplicon generated in the same reaction was subjected to Dilute’N’Go dideoxy-sequencing, a protocol for sequencing that can be performed directly on LATE-PCR amplification. Dilute’N’Go dideoxy-sequencing confirmed the presence of a single point mutation in TP53 exon 7 known to present in this particular Barrett’s esophagus cell line. Conclusion: This thesis provides proof-of-principle for the construction of a clinically compatible diagnostic method for the detection of TP53 tumor suppressor gene inactivation based on LATE-PCR. This assay should have broad applicability since TP53 gene inactivation is a key event in the progression of many pre-malignant conditions towards cancer. The first application of the LATE-PCR TP53 inactivation assay will be to Barrett’s Esophagus, a pre-malignant condition where genetic alterations of TP53 are known predictors of future cancer risk.