Abstract
Purpose: :
It has been shown that macrophage migration inhibitory factor (MIF) is present in the anterior chamber and contributes to ocular immune privilege. Solid tumors have been described as immune privileged sites, and commonly overexpress MIF. We have discovered that the B16–F10 mouse model of melanoma overexpresses MIF compared to the syngeneic, non–tumorigenic Melan–a cell line; therefore, we wanted to reduce MIF’s expression in the B16–F10 cell line to determine if MIF plays a role in tumorigenesis.
Methods: :
An interfering MIF (iMIF) RNA, and a control interfering RNA were stably introduced into B16–F10 mouse melanoma cells. Tumor challenge experiments in C57BL/6 mice were performed in the anterior chamber and subcutaneously with the transfected cell lines. Additionally, high resolution 2D gel electrophoresis was performed on cell lysates to determine quantitative differential protein expression between the cell lines.
Results: :
The iMIF tumor cells proliferate 50% slower than RNAi control cells in vitro. On day 7 the iMIF anterior chamber challenged mice had trace amounts of tumor cells, and the control mice had well established tumors by histological analysis. The iMIF subcutaneously challenged mice had delayed tumor establishment by 1 week compared to the RNAi controls, and inoculating twice as many iMIF cells did not restore tumor establishment kinetics to control levels. Differential protein expression revealed that glycolytic proteins were down regulated more than 2 fold in the iMIF cell line.
Conclusions: :
Interfering with MIF expression in the B16–F10 cells delays tumor cell proliferation in vitro and tumor establishment in vivo. These results demonstrate a potent target for solid tumor therapy.
Keywords: tumors • melanoma • immune tolerance/privilege