The aim of this study was to characterize the oncogenic function and mechanism of
Cathepsin Z (CTSZ) at 20q13.3, a frequently amplified region in
hepatocellular carcinoma (HCC). Real-time PCR were used to compare CTSZ expression between paired HCC
tumor and non-
tumor specimens. CTSZ gene was stably transfected into HCC line QGY-7703 cells and its role in tumorigenicity and cell motility was characterized by soft
agar, wound-healing, transwell invasion and cell adhesion assay, and
tumor xenograft mouse model. Western blot analysis was used to study expression of
proteins associated with epithelial-mesenchymal transition (EMT).Upregulation of CTSZ was detected in 59/137 (43%) of primary HCCs, which was significantly associated with advanced clinical stage (P = 0.000). Functional study found that CTSZ could increase colony formation in soft
agar and promote cell motility. Further study found that the metastatic effect of CTSZ was associated with its role in inducing epithelial-mesenchymal transition (EMT) by upregulating mesenchymal markers (
fibronectin and
vimentin) and downregulating epithelial markers (
E-cadherin and α-
catenin). In addition, CTSZ could also upregulate
proteins associated with extracellular matrix remodeling such as MMP2, MMP3 and MMP9. Taken together, our data suggested that CTSZ was a candidate oncogene within the 20q13 amplicon and it played an important role in HCC
metastasis.