1. ¹Department of Surgery, Medical Institute of Bioregulation, Kyushu University, Beppu, Japan
2. ²Division of Stem Cell Regulation/Molecular Hematopoiesis, Jichi Medical School, Center for Molecular Medicine, Tochigi, Japan

Correspondence: Dr M Mori, Department of Surgery, Medical Institute of Bioregulation, Kyushu University, 4546 Tsurumihara, Beppu 874-0838, Japan; E-mail: mmori@beppu.kyushu-u.ac.jp

Received 7 August 2007; Revised 6 November 2007; Accepted 6 November 2007; Published online 22 January 2008.

Abstract

We previously cloned human G protein gamma 7 (GNG7) and demonstrated that it was downregulated in gastrointestinal cancer. The significance of GNG7 expression in oesophageal cancer is unknown. TaqMan quantitative real-time PCR was performed to determine the clinical significance of GNG7 expression in 55 cases of oesophageal cancer. Furthermore, GNG7-transfected oesophageal cancer cells were analysed in laboratory studies at genomic and epigenetic levels. Twenty-seven patients with low GNG7 expression showed significantly poorer survival than did 28 patients with high expression (P<0.05). Tumours with low GNG7 expression invaded deeper than those with high GNG7 expression (P<0.05), both in vivo and in vitro. Eight tumours retained GNG7 expression, and they did not show either promoter hypermethylation or loss of heterozygosity (LOH). In 38 tumours with GNG7 suppression, 22 (57%) showed either LOH or promoter hypermethylation. In addition, GNG7 expression was significantly associated with the presence of miR328 in oesophageal cancer cell lines, which suggests that this microRNA might be a regulator of GNG7 expression. GNG7 suppression represents a new prognostic indicator in cases of oesophageal cancer. GNG7 might be suppressed by LOH and promoter hypermethylation or by microRNA.