Cancer cells can reactivate a cellular process that is an essential part of embryonic development. This allows them to leave the primary tumor, penetrate the surrounding tissue and form metastases in peripheral organs. In the journal Nature Communications, researchers from the University of Basel’s Department of Biomedicine provide an insight into the molecular networks that regulate this process.

In a study published in the latest edition of Nature Communications, the researchers focused specifically on microRNAs (miRNAs), a class of very short non-coding RNAs with a considerable effect on gene regulation. They identified a hitherto unknown microRNA, miR-1199-5p, that induces epithelial cell behavior and impedes the malignancy of tumor cells, as well as their potential to form secondary tumors.

In concrete terms, the newly discovered microRNA prevents the synthesis of a specific protein, the transcription factor Zeb1, which activates EMT/MET — but if it is missing, the EMT process is prevented. Zeb1 also suppresses the expression of miR1199-5p in what is known as a negative feedback loop, whereby the two molecules regulate one another reciprocally.

During an embryo’s development, epithelial cells can break away from the cell cluster, modify their cell type-specific properties, and migrate into other regions to form the desired structures there. This process, which is known as an epithelial-mesenchymal transition (EMT), is reversible and can also proceed in the direction from mesenchymal cells to epithelial cells (MET). It is repeated multiple times during embryonic development and ultimately paves the way for the formation of organs in the human body.