Expression of lysyl oxidase-like 2 in cholangiocarcinoma and its relations with vascular endothelial growth factor A and angiogenesis

Objective: To investigate the expression of lysyl oxidase-like 2 (LOXL2) in cholangiocarcinoma (CCA) and its association with angiogenesis in CCA.

Methods: The relevant data were downloaded from the GEO database, and then, the difference in LOXL2 mRNA expression between CCA tissue and tumor adjacent tissue was compared; the potential function of the LOXL2 in CCA was determined by gene set enrichment analysis; the relationship between the expressions of LOXL2 and vascular endothelial growth factor A (VEGFA) was analyzed in each dataset. The changes in expression and secretion level of VEGFA in CCA cells after down- or up-regulating LOXL2 expression were detected by Western blot, qRT-PCR and ELISA, respectively. The human umbilical vein endothelial cells (HUVECs) were cultured with the conditioned medium from CCA cells with LOXL2 interference or overexpression, and then, the tube formation abilities of the HUVECs were observed. 

Results: The results of GEO database analyses showed that the LOXL2 expression in CCA tissue was significantly higher than that in tumor adjacent tissue (P<0.05); LOXL2 was possibly associated with angiogenesis in CCA; there was a significant positive correlation between LOXL2 expression and VEGFA expression in each GEO dataset (r=0.320, 0.243, 0.234 and 0.665, all P<0.05). In CCA cells, the VEGFA expression and secretion level of LOXL2 were significantly decreased after LOXL2 interference, and were significantly increased after LOXL2 overexpression (all P<0.05). The number of tube formation was significantly decreased in HUVECs after culture with the conditioned medium from CCA with LOXL2 knockdown, and was significantly increased in HUVECs after culture with the conditioned medium from CCA with LOXL2 overexpression (both P<0.05).

Conclusion: LOXL2 expression is increased in CCA and it may promote angiogenesis in CCA through upregulating VEGFA expression.

Key words: Bile Duct Neoplasms; Lysyl Oxidase-Like 2; Vascular Endothelial Growth Factor A; Neovascularization, Pathologic