Phosphatidic Acid Phosphatase Type 2 Domain Containing Protein 1B (PPAPDC1B)

The 175-amino acid protein contains an N-terminal transmembrane domain, an acid phosphatase homology region, 2 PKC phosphorylation sites, and a tyrosine kinase phosphorylation site. RT-PCR analysis of 16 metastatic HCC tissues paired with 16 primary HCC tissues showed downregulation of PPAPDC1B expression in 11 of 16 metastatic lesions compared to primary HCC tissues, with 9 of 16 metastatic lesions showing significant downregulation of PPAPDC1B (P less than 0.05).

PPAPDC1B-transfected metastatic HCC cells showed significantly lower invasion activity. Transfection and expression of PPAPDC1B in nude mice bearing human HCC significantly decreased the incidence and degree of pulmonary metastasis of HCC.