Here’s part 5 of our cancer biology blog series and the second section of the part-4 (Unrestrained Spread). If you haven’t read the last blog, we recommend that you go through it before proceeding with this blog. This will help you understand the complete topic better and be ready for the next parts. To read part 4 – Click Here.
So, let’s try to understand the EMT mechanics or Epithelial-Mesenchymal Transitions in brief.
As you can see in the above picture, in a primary tumour or in a particular site, the cells are having connections with each other. As well as they are having a connection with the basal matrix of the tissue and the organ. Basically, they have the following properties
- Epico Basal Polarity – It means that the cells are attached to the basal matrix with the basal region and with the apical region they are having different signal in the separation.
- Presence of Tight Junctions, Adherent Junctions and Desmosomes – This is also called as the cell to cell contact.
- They Show Epithelial Markers – These include E-cadherin, Epithelial cell molecules, Occludins, Claudins, alpha6beta4 integrins, Cytokeratins, etc.
- They Have Proteins to Interact with the Basal Membrane – These include Crumbs, PATJ, LGL, etc.
However, they can lose these properties and initiate the process of PMT. First of all, they lose the Epico Basal Polarity and cell to cell interaction. They gain mesenchymal protein molecules to go from epithelial state of the cells to Mesenchymal sate of the cells. And once they acquire the Mesenchymal properties, they can start the process of metastasis.
So once the cells have undergone the mesenchymal transitions, they gain front/back polarity and start expressing the mesenchymal molecules like N-cadherin, Vimentin – which is a cytoskeleton molecule of mesenchymal origin, Fibronectin, Beta1 & Beta3 Integrins and Mix Metallo Proteases (MMPs) – which help the cells to detach from the basal membrane.
Signals for EMT
The whole system or process of EMT which is helping metastasis is actually caused by some signals which act as inducers for Epithelial-Mesenchymal Transitions. Once the cells start getting these signals, they express the EMT transcription factors like Snail (Snail1 and Snail2/Slug), and ZEB (ZEB1 and ZEB2/SIP1), etc. and they start this procedure.
So, let’s summarise this, as the cells start getting the signals for EMT due to which the EMT transcription factors are expressed. And these transcription factors start inhibiting all the properties related to the epithelial cell system. Also, they activate all the proteins, gene expression and the properties which are related to the mesenchymal system.
We will further explore this topic in the next part of our blog series. So, stay tuned with us. To read part 6 – Click Here.