PinX1 was isolated as a Pin2/TRF1 binding protein that also binds to the telomerase catalytic subunit hTERT. The gene is a potent telomerase inhibitor and a putative tumor suppressor since it inhibits telomerase activity and affects tumorigenicity in nude mice. This study investigated aberrations of PinX1 gene in gastrointestinal tract carcinomas (GITCs). We examined mutations, mRNA expression and promoter methylation of PinX1 gene in 15 GITC cell lines, and 20 patients with primary GITC. We found a missense mutation at codon 254 (AGC/TGC) in a colon and an esophageal carcinoma cell line, and in cancerous and matching normal tissues of 2 patients with primary GITC (10%). It might be a benign polymorphism. No hyper-methylation was found in the promoter region and the treatment by 5-Aza-2'-deoxycytidine did not affect PinX1 mRNA expression level in any of the cell lines. It was concluded that the human PinX1 does not affect tumorigenesis of human GITC.