Interrogation of Chromosome 13q12-14 in Esophageal Squamous CellCarcinoma

摘要

Previous studies of esophageal squamous cell carcinoma (ESCC) suggested chromosome region 13q12-14harbors a familial ESCC gene. DNA sequencing of the BRCA2 gene, located on 13q12, showed evidence of both germlineand tumor specific alterations but the frequency of changes was low and did not fit the classic Knudsen two-hit geneinactivation model. To further investigate chromosome 13q12-14 in ESCC, quantitative expression measurements wereperformed on BRCA2 and 11 neighboring genes in matched normal epithelium and tumor from 17 cases. Transcriptanalysis showed normal levels of five genes, tumor down-regulation of two genes (TNFRS19 and TPT1), and tumor upregulationof five genes, including BRCA2. No evidence of BRCA2 loss-of-function was detected based on reducedmRNA in tumor cells. Between 13q12.3 (KATNAL1) and 13q12.3-q13 (CCNA1) five adjacent genes showed increasedmRNA expression raising the possibility of a DNA amplicon; however, qPCR analysis showed normal DNA amounts inthis region. CCNA1 transcript was significantly up-regulated in tumors and was thus further interrogated at the proteinlevel by immunohistochemistry. CCNA1 staining was restricted to normal basal epithelium and was not expressed inmore superficial, differentiated regions. In contrast, the CCNA1 protein was ubiquitously and highly expressed throughouttumor foci. Overall, these data from a relatively small number of cases (17) suggest that TNFRS19 and TPT1 deservefurther investigation as candidate tumor suppressor genes in esophageal cancer in a larger patient series; BRCA2 mRNA isincreased in the tumors, likely as a compensatory response to the marked DNA damage that is present in these lesions;and, CCNA1 was identified as a novel up-regulated gene in ESCC.