Sperm protein 17 and AKAP-associated sperm protein cancer/testis antigens are expressed in ciliated hepatic foregut cysts

Aims: Ciliated hepatic foregut cysts (CHFCs) are retained benign lesions of the liver. However, a case of squamous cell metaplasia and five cases of squamous cell carcinoma arising from a CHFC have been described. The potential of malignant transformation makes the identification of new biomarkers necessary. As the cancer/testis antigen sperm protein 17 (Sp17) has been detected in oral and oesophageal squamous cell carcinomas, the aim of this study was to investigate the expression of Sp17 and AKAP-associated sperm protein (ASP), which has a shared N-terminal sequence with Sp17, in four surgically resected CHFCs. Methods and results: CHFC specimens were taken from two patients who attended the Medical College of Wisconsin, Milwaukee, USA and two patients who attended the Fundación Jiménez Díaz, Madrid, Spain. CHFCs were found to be immunopositive for Sp17 and ASP. Both proteins were localized to the cytoplasm of ciliated cells lining the cysts, and their cilia. Confocal microscopy demonstrated that Sp17 and ASP overlapped in the same region of the cell. Conclusion: Sp17 and ASP cancer/testis antigens were found in ciliated cells of four CHFCs. Further characterization of Sp17 and ASP in patients with CHFCs may provide significant clues for understanding the molecular mechanisms underlying their predisposition to develop squamous cell carcinomas.