Cells have receptors on their surface to enable responses to external signals. Transduction pathways within the cell regulate how the external signals influence gene expression and hence cell function. Typically, the cellular transduction pathways involve kinase activity. Kinases are enzymes that control the biological activity of proteins in the cell by phosphorylating certain amino acids using ATP as the phosphate source. The net effect of this is the conformation change in the protein causing a shift from the inactive to the active form.

In the case presented here, we have two pathways:

1. The MAP Kinase Pathway

2. The P13K / AKT Pathway

Both routes are important in propagating cellular division, potentially leading to cancer presentation.

It is vital to note that PTEN is a tumour suppressor (i.e. see the ‘T’ inhibitory sign). This will stop the progression of the P13K / AKT pathway. However, the availability of RAS at the start of the MAPK Pathway can cause activation and propagation of cell division. Following the mutation of RAS, this protein becomes hyperactivated and as such it operates constantly irrespective of the cell signal coming in from the cell surface receptor. Hence, such a mutation can support continuous cellular proliferation and neoplasm development.