Prof. Joseph Schlessinger is one of the pioneers of the sub-field of Signal Transduction, which is paramount for cancer research, and many other fields as well.
Signal transduction describes processes by which a cell converts one kind of signal. Most signal transduction processes either involve sequences which are ordered of biochemical reactions within the cell. These are then carried out by enzymes, activated by second messengers. The overall result is a signal transduction pathway. This usually happens extremely quickly, normally in milliseconds (such as the case of ion flux). Other times this can take minutes for the activation of lipid-mediated and protein kinase cascades. That being said, some such reactions can take many hours, days and even more. This is determined by necessity of the gene expression completion.
The amount of molecules and proteins involved in the events regarding to signal transduction expands as the process emanates from the primary stimulus, and the result is a “signal cascade,” beginning with a relatively tiny stimulus that causes a greater response. This is referred to as amplification of the signal.
In single-cell organisms as well as bacteria, the variety of process of signal transduction of which the cell is capable of influences the number of ways it can respond to its environment. In multi-cellular organisms, a variety multitude of different signal transduction processes are necessary for the coordination of the behavior and function of the comprising individual cells. This is both understandable and necessary so the whole organism can properly function. As you could expect, more complex organisms have a vast number of signal transduction processes. Consequentially, getting any stimulus from the outside environment at the cellular level depends on signal transduction.
This is why countless diseases including cancer, diabetes, heart disease and many more are involved with signal transduction and are a result of a flaw of the signal transduction pathways. This work is still far from being finished and additional grants are needed for the better of us all.