Human beings are not very fertile and the main reason seems to be dysregulation during the blastocyst implantation. This process is controlled by several molecules and their dysregulation can result in miscarries, pre-eclampsia or choriocarcinoma. One of those molecules is LIF. In this thesis, two review articles summarized LIF production, LIF-induced effects in trophoblastic cells, and the information about the potential clinical applications of LIF. The second part includes original articles focused on the activation and cross-talk of the JAK/STAT and MAPK cascades. It was demonstrated that ERK1/2 plays an important role in the proliferation of trophoblast cells. Likewise, a cross-talk between ERK1/2 and STAT3 was defined: ERK1/2 is not responsible for the STAT3 ser727 phosphorylation, but it has a negative effect on the translocation of STAT3 into the nucleus, which results in a decrease of trophoblast invasiveness.