According to the current guideline (AWMF), there are few possibilities for chemotherapy for endometrial carcinoma (EC). This puts tumor markers and targeted therapy into focus. In this context, molecular signal cascades and their modulators are becoming increasingly important. The PI3 kinase / AKT signaling cascade with its regulator microRNA 21 (miR-21) is affected by mutations in many tumor entities and offers various targets. This work illustrates the signal cascade in the EC and characterizes the regulatory role of miR-21 in more detail. To make the most comprehensive statement possible with respect to the tumor entity EC, a cell line of prognostically favorable type I and unfavorable type II was selected according to the classification of Bokhman (1983). The cell lines were characterized in terms of morphology and their molecular properties. Using transfection of pmiR-21, miR 21 was overexpressed in the EC cells and the protein expression of the PI3K / AKT signal cascade was analyzed after 6-96 h by means of gel electrophoresis and subsequent western blot. In the cell line MFE-296, the expected changes in the signal cascade occurred. The expression of the phosphatase PTEN was inhibited and the cell cycle was inhibited. The cell line MFE 280 showed no changes after transfection. Causes are probably the different PTEN activity due to mutations and other regulatory mechanisms. In addition to the direct inhibition of PTEN, miR-21 indirectly influences the stability of the ...