The invention features a method of inhibiting tumor growth and/or tumor invasiveness in a mammal by administering to a mammal a compound (e.g., an antagonistic antibody) which inhibits expression or enzymatic activity of human aspartyl (asparaginyl) beta-hydroxylase (HAAH). The invention also features a method for diagnosing the growth of a malignant neoplasm (e.g., pancreatic cancer) in a mammal by contacting a tissue or bodily fluid from the mammal with an antibody which binds to a HAAH polypeptide under conditions sufficient to form an antigen-antibody complex and/or detecting the antigen-antibody complex.