Macrophage migration inhibitory factor is differentially expressed in normal and choriocarcinoma trophoblast cells.

Trophoblast cells are specific for placenta, the organ necessary for development of the fetus. Trophoblast derived choriocarcinoma is a rare cancer, with high metastatic potential, invading surrounding tissues and distant organs. Macrophage migration inhibitory factor (MIF) is a pleiotropic cytokine involved in a wide range of biological processes, which is increased in almost all human cancers. Expression of MIF in normal and choriocarcinoma trophoblast cells is investigated here, using normal extravillous trophoblast derived cell line HTR-8/SVneo, and choriocarcinoma cell lines JAR and JEG3. Expression of MIF and its receptors CD74 and CXCR2 was investigated at mRNA level using qPCR. Expression of MIF protein was studied using immunofluorescence and western blot, under reducing and native conditions, in whole cell lysates, subcellular fractions and conditioned media. The expression of MIF mRNA was similar in all three cell lines, while CD74 mRNA was more expressed in choriocarcinoma cells (14-fold for JAR, 12-fold for JEG3, p<0.01). CXCR2 mRNA was higher in JEG3 cell line compared to HTR-8/SVneo cells (6-fold, p<0.01). While the cellular level of MIF was similar, the level of secreted MIF was lower in JAR cell conditioned media compared to media of both HTR-8/SVneo (2.8-fold, p<0.01) and JEG3 cells (4.1-fold, p<0.001). Cellular distribution of MIF was similar between the studied cell types. MIF was predominantly cytoplasmic, but also detected in membrane, nuclear soluble and nuclear chromatin fraction. MIF appeared in high molecular weight complexes of >150 kDa under native conditions. A band of 140-145 kDa was consistently present in JEG3 cell lysates, while it was absent or very weak in other cell types. These results show that MIF/CD74 axis is shifted in choriocarcinoma, as previously shown for other cancers, and further justifies research towards the most effective MIF targeting therapeutics.