P-0024 - Expression and function of metastasis-associated C4.4A in hepatocellular carcinoma
|Date||28 June 2014|
|Event||World GI 2014|
|Topics|| Hepatobiliary Cancers
|Citation||Annals of Oncology (2014) 25 (suppl_2): ii14-ii104. 10.1093/annonc/mdu165|
M. Görtz1, U. Galli2, P. Schemmer1
The expression of the glycoprotein C4.4A is highly restricted in non-transformed tissues and its physiological function is largely unknown. Nonetheless, C4.4A is upregulated during tumor growth and was detected in several types of malignancies like mammary, esophageal and colorectal carcinoma. This study was designed to investigate C4.4A protein expression in liver tumor and to explore its function in tumor progression.
Human tissue of normal liver, hepatocellular carcinoma (HCC) and lung metastasis of HCC was subjected to immunohistochemical staining. C4.4A expression in the human HCC cell lines HepG2 and Huh7 and possible colocalization with the extracellular matrix receptor Integrin α6 were investigated by confocal microscopy. Possible roles of C4.4A in liver tumor were analyzed by C4.4A inhibition via siRNA transfection of HCC cells, followed by cell migration measurement using scratch and Laminin-1 invasion assays. Tests were carried out under normoxic and hypoxic conditions.
While normal liver tissue doesn't express C4.4A, immunohistochemistry showed strong C4.4A staining in 57% of HCC and in 80% of HCC metastasis. Double immunofluorescence staining displayed C4.4A expression and partial C4.4A-Integrin α6 colocalization in HCC cells. Colocalization was strengthened under hypoxia. C4.4A-targeted siRNA treatment led to reduced migration, in particular under hypoxia. C4.4A knockdown revealed that C4.4A facilitates extracellular matrix degradation and that the C4.4A level is associated with the migratory ability of HCC cells.
This study demonstrates that C4.4A is absent from normal liver, but expressed in human HCC and HCC metastasis. C4.4A might well contribute to tumor progression and metastasis formation of HCC, since we observed that C4.4A is involved in migration and invasion. The importance of C4.4A for the migration of HCC cells was particularly observed under hypoxia, which might be due to the increased association with the membranous cell adhesion molecule Integrin α6 under hypoxia.