Abstract: CT9 is a recently cloned cancer-testis antigen, which is a member of the bromodomain and extraterminal family.Each member of this protein family contains two N-terminal bromodomain motifs.We investigated the distribution of CT9 in different tissues and the possibility for it to be used as a potential therapeutic target in cancer treament.By using the real-time RT-PCR method and 18SrRNA as an internal standard, we analyzed the CT9 expression in several normal human tissues and in the tissues of patients suffering from cancer.The result of this study shows that the highest level of mRNA is only present in testis tissue because the CT9 expression has not been detected in other normal tissues.In 6 of 10 cases of gastric adenocarcinoma, in 3 of 10 cases of esophageal squamous cell carcinoma, in 2 of 9 cases of endometrial carcinoma and only in 1 of 12 cases of brain cancer, the low level expression of CT9 was detected.In none of the 12 cases of cervical squamous cell carcinoma, the expression of CT9 was detected.Since the high level expression of CT9 is only found in the normal testis tissue, but the low expression in cancer tissues, for example tissues of cervical squamous cell carcinoma, brain cancer, endometrial adenocarcinoma, esophageal squamous cell carcinoma, we conclude that CT9 cannot be used as a cancer therapeutic target molecule for cervical squamous cell carcinoma, brain cancer, endometrial adenocarcinoma, esophageal squamous cell carcinoma.

Key words: CT9, Cancer-testis antigen, Real-time RT-PCR