Tumorigenic function of GPR39 in ESCC cells. (A) Expression of GPR39 in GPR39-transfected KYSE30 cells was confirmed by RT-PCR (left) and Western blot analysis (right). c1 and c4 are two independent GPR39-expressing clones. Vec-30 represents empty vector-transfected KYSE30 cells. (B) Representative of foci formation in monolayer culture. Quantitative analyses of foci numbers were shown in the right panel. Values were the mean ± SD of at least three independent experiments. **P < 0.01; independent Student's t-test. (C) Representative of colony formation in soft agar. Percentage of colonies formed was summarized in the right panel. Values were the mean ± SD of at least three independent experiments. **P < 0.01. (D) Growth curves of GPR39-expressing cells were compared with Vec-30 cells by cell growth assay. The results were expressed as mean ± SD of at least three independent experiments. **P < 0.01. (E) Tumor growth curves of GPR39-expressing cells in nude mice were compared with Vec-30 cells by tumor xenograft experiment. The average tumor volume of GPR39-expressing cells vs Vec-30 cells was expressed as mean ± SD in 10 inoculated sites for each group of cells. **P < 0.01. (F) Representative examples of tumors formed in nude mice following injection of GPR39-expressing KYSE30 cells (right) and Vec-30 cells (left).