Improved marker combination for detection of de novo genetic variation and aberrant DNA in colorectal neoplasia.

Author(s): Kann L,  Han J,  Ahlquist D,  Levin T,  Rex D,  Whitney D,  Markowitz S,  Shuber A

Journal: Clin Chem

Date: 2006 Dec

Major Program(s) or Research Group(s): GOCRG

PubMed ID: 17082247

PMC ID: not available

Abstract: BACKGROUND: The genetic heterogeneity of sporadic colorectal cancer (CRC) makes the choice of genetic markers and sequence variation-detection technologies critical to the performance of screening assays. We have previously described the effectiveness of a CRC assay composed of 22 known variants in KRAS, APC, TP53, and BAT-26 (V1). We introduce a new marker formulation (V2) that includes detection of de novo variation in APC, PIK3CA, and CTNNB1, hypermethylated sequences within SMARCA3 and VIM, and a single-base variation within BRAF. We compared the abilities of the V1 and V2 markers to detect aberrant DNA in colorectal neoplasias. METHODS: V1 and V2 marker formulations were used to analyze 144 colorectal tissue samples comprising 50 precancerous adenomas, 94 carcinomas, and 11 nonpathologic tissues. V1 analysis consisted of single-base extension analysis of the 22 V1 variants. V2 analysis consisted of DNA scanning of the APC mutation cluster region, PIK3CA exons 9 and 20, CTNNB1 exon 3, analysis for the BRAF Val600Glu substitution, and methylation-specific PCR analysis of VIM and SMARCA3. RESULTS: The V2 marker formulation had significantly higher sensitivity than the V1 markers for carcinomas (93.6% and 72.3%, respectively; P = 0.0002) and adenomas (92.0% and 62.0%, respectively; P = 0.0006). None of the nonpathologic samples were positive for any marker. CONCLUSIONS: We demonstrate improved sensitivity of a new marker formulation (V2) to detect aberrant DNA in CRC and precancerous adenoma tumor tissues.