Abstract
Purpose: :
Uveal melanoma (UM) is the most common primary intraocular tumor, with most distant metastasis developing the liver. The functional role of chemo-attractive cytokines, known as chemokines, in tumor biology is well described and has been demonstrated to mediate leukocyte trafficking, inflammation, angiogenesis, and tumorigenesis. We sought to investigate the role CXCL12, CXCL8, CXCL1, and HGF may play in UM disease progression.
Methods: :
Tumor tissue was harvested from a previously established UM rabbit model. Isolated tumor samples from the intra-ocular primary site, tumor cells re-cultured from systemic circulation (CMCs) and tissue from the site of lung metastasis were biopsied, snap frozen on dry ice and stored at - 80oC. Total mRNA was later extracted from primary tumor, CMCs and lung metastasis using an RNeasy RNA extraction kit (Qiagen). Then, one step RT-qPCR was performed on all samples using appropriate primers for CXCL12, CXCL8, CXCL1, and HGF (QuantiTect® Primer Assays). Beta-actin used as a housekeeper gene for purposes of normalization in all RT-qPCRs preformed.
Results: :
Intra-ocular tumor cells demonstrated no expression of CXCL12 mRNA and just under a ten-fold increase in expression was observed for CXCL1 and HGF. Though the expression of CXCL8 in primary site was low relative to the other chemokines in this study, its expression was more pronounced than in CMCs and in lung metastasis. Similarly, captured CMCs expressed no CXCL12 mRNA and had a less than three-fold increase in CXCL1, HGF and CXCL8 expression. Lung metastasis is marked by more than a 100-fold increase in CXCL12, CXCL1 and HGF mRNA expression and demonstrated no CXCL8 expression.
Conclusions: :
The differential expression of CXCL12, CXCL8, CXCL1, and HGF in an ocular and metastatic animal model of UM displays the importance of these chemo-attractive factors during different crucial points of UM disease progression. These results suggest drastic phenotypic change occurring in the tumor cells during disease progression. To the best of our knowledge, this is the first time that differential expression of these four chosen chemo-attractive ligands, has been displayed in an ocular melanoma animal model.
Keywords: uvea • tumors • gene/expression