Recurrent amplification in the 22q11 region in laryngeal squamous cell carcinoma results in overexpression of the CRKL but not the MAPK1 oncogene

Abstract

Thirteen laryngeal squamous cell carcinoma cell lines were recently studied by array comparative genomic hybridization (array-CGH) in order to identify recurrent DNA copy number alterations in the tumor genome. A highly amplified region 22q11.2 was found in two of the thirteen cell lines. Two established oncogenes CRKL and MAPK1 are localized in this region, but only CRKL was amplified in both cell lines. Therefore, to check if amplification of either CRKL or MAPK1 genes may be important in the pathogenesis of laryngeal squamous cell carcinoma, the DNA copy number and mRNA expression were measured in a cohort of 17 LSCC cell lines by quantitative real-time PCR (qPCR). For the CRKL gene gains of the copy number were found in 3/17 cell lines, while overexpression was found in 6/17 cell lines. Gains in the copy number for the MAPK1 gene were found in 1/17 cell lines, but overexpression was not detected in any cell line. A highly significant correlation between DNA copy number and expression for CRKL gene, but not for MAPK1 gene was established using the Pearson test. Thereafter, 46 primary samples of laryngeal cancer were tested by qPCR to check for possible gains in copy number of the CRKL gene. Gains were found in 3/46 cases. These results suggest that CRKL, but not MAPK1 is the target oncogene of the rare but recurrent amplification at 22q11.2 in laryngeal squamous cell carcinoma.