The distribution and expression profiles of human Aspartyl/Asparaginyl beta-hydroxylase in tumor cell lines and human tissues

Human aspartyl beta-hydroxylase (HAAH) is a highly conserved enzyme that hydroxylates epidermal growth factor-like domains in transformation-associated proteins. Previous studies showed that the HAAH gene was overexpressed in many human malignancies. The present study investigates the distribution and expression profiles of HAAH in a variety of tumor cell lines and human tissues. One hundred and four cases of carcinomas were retrieved from the pathology archives of Department of Pathology, First Affiliated Hospital of Medical College of Xi'an Jiaotong University. Paraffin-embedded tissue specimens were immunostained with the HAAH monoclonal antibodies (MAb) generated to naked plasmid DNA containing N-terminal domain of the encoding HAAH gene and recombinant HAAH. Immunoreactivity was detected in 90.4% (94 positive cases) of carcinomas, including 88.5% of strong positive cases. In addition, HAAH mRNA levels were measured in seven tumor cell lines and in normal tissue. The results demonstrated that HAAH was highly expressed in the tumor cell lines in contrast to its low level of expression in normal tissue. The protein expression level of HAAH in the tumor cell lines by Western bolt analysis was comparable to the mRNA expression level. HAAH distribution in seven tumor cell lines was analyzed by immunofluorescence cell staining. The antigen was primarily localized in cytoplasm and plasmalemma. HAAH mAb exhibited high level binding to the four tumor cell lines (breast carcinoma MCF-7, hepatic carcinoma SMMC-7721, cervix cancer Hela and ovary cancer SKOV) and lower degrees of binding were observed with the other three (renal adenocarcinoma ACHN, bladder cancer BIU-87 and laryngeal cancer Hep-2). In contrast, normal mouse embryonic osteoblasts MC3T3 exhibited no staining. In conclusion, HAAH is overexpressed frequently a variety of carcinomas, indicating that overexpression of the enzyme correlates with the development and progression of carcinomas and it could serve as a prognostic biomarker to predict the clinical course of some carcinomas.