Novel targets for the 18p11.3 amplification frequently observed in esophageal squamous cell carcinomas

Amplification of DNA in certain chromosomal regions, with consequent over-expression of specific genes within these amplicons, plays a crucial role in the development and progression of human cancer. Since our previous comparative genomic hybridization (CGH) study revealed frequent amplifications at 18p in esophageal squamous cell carcinomas (ESC) cell lines, we focused on the identification of genetic target(s) within the 18p amplicon. In four cell lines having remarkable copy-number amplification with homogeneously staining region (HSR) pattern by fluorescence in situ hybridization (FISH), the smallest common region of overlapping covered approximately 3.5 Mb at 18p11.3. We screened 29 ESC cell lines to discern amplifications and expression levels of 14 known genes and 21 uncharacterized transcripts within the amplicon. Only four known genes, YES1, TYMS, HEC and TGIF showed amplification and consequent over-expression. These genes were amplified in several of primary ESCs. Moreover, resistance to transforming growth factor beta (TGFbeta)-induced growth inhibition was enhanced in four cell lines with amplification and expression of TGIF, which encodes the repressor for TGFbeta-activated transcription, appears to be involved in the progression of ESC. Taken together, these results suggest that YES1, TYMS, HEC and TGIF are likely to be candidate targets for 18p11.3 amplification and be associated with esophageal tumorigenesis.