Study of transforming capacity of two novel genes JS-1 and JS-2 in chromosome 5p and their overexpression in human esophageal squamous cell carcinoma

Abstract

Esophageal squamous cell carcinoma (ESCC) is an aggressive cancer that is characterized by a high mortality rate and geographic differences in incidence. Previous studies of comparative genomic hybridization (CGH) showed that chromosomal 5p is frequently amplified in cell lines and patient cases of ESCC. According to the recent CGH study on ESCC cases of Hong Kong Chinese origin and the information available in Human Genome Resources, National Center for Biotechnology Information (NCBI), attempt was made to identify novel genes within a minimum overlapping region in chromosome 5p15 which may be relevant to the molecular carcinogenesis of ESCC. In this part of study, we analyzed the expression levels of two novel genes located in 5p15.2, named as JS-1 and JS-2, in cell lines and surgical specimens of ESCC and also studied their transforming capacity in normal cells. The coding sequences of JS-1 and JS-2 cDNAs were confirmed by 3’ and 5’ rapid amplification of cDNA ends (RACE). Twelve ESCC cell lines and 13 ESCC cases with their corresponding non-tumor epithelial tissues were analyzed by semi-quantitative multiplex reverse transcriptase-polymerase chain reaction (RT-PCR) for their expression levels with β-actin expression acting as the internal control. The transforming capacity of JS-1 and JS-2 was investigated by transfecting the NIH-3T3 cells with JS-1 and JS-2 cloned into pcDNA3.1(+) expression vector followed by soft agar assay for studying their anchorage independent growth property. The results show that 6/12 (50%) and 2/12 (12.5%) of the ESCC cell lines showed overexpression of JS-1 and JS-2 respectively. Five (38.5%) and 1 (7.7%) out of 13 ESCC specimens showed overexpression of JS-1 and JS-2 genes respectively. Overexpression of JS-1 in NIH-3T3 cells caused colony formation in soft agar but not for JS-2. Sarcoma was formed when NIH-3T3 cells with overexpression of JS-1 were injected subcutaneously into athymic nude mice. Our results thus indicate that the overexpression of JS-1 and its transforming capacity in normal cells may play a critical role in the molecular pathogenesis of ESCC.