EGF
Meaning of EGF: The signal telling skin and lining cells to divide, and a pathway where treatment targets the receiver rather than the signal.
Definition of EGF
EGF stands for epidermal growth factor, a small protein released by many tissues that instructs nearby cells to survive, move and divide. It docks onto a receptor threaded through the cell membrane, switching on a chain of internal messages ending at the genes that control division. It is plentiful in saliva, milk and urine, and it drives the repair of skin and of the linings of the gut.
Why is the receptor the interesting part?
Because that is where things go wrong and where drugs act. When the growth factor lands, two receptor molecules pair up and switch each other on by adding phosphate to their inner ends, starting the cascade. In several cancers that switch is jammed in the on position, either because the receptor gene is mutated or because the cell has built far too many copies of the receptor. Treatment therefore aims at the receptor, not at EGF itself: antibodies cap the outer end so nothing can dock, and small molecules slip inside the cell and block the switch directly.
How does it relate to HER2?
| Family member | Also called | Distinguishing feature |
|---|---|---|
| EGFR | HER1, ErbB1 | The receiver for EGF; mutated in a subset of lung cancers |
| HER2 | ErbB2 | No signal of its own; amplified in some breast cancers |
| HER3 | ErbB3 | Weak internal switch, so it depends on a partner |
| HER4 | ErbB4 | The least studied of the four |
All four are versions of the same receiver, which is why HER2 carries a name referring to a growth factor it does not bind. It works instead by pairing with its relatives and amplifying whatever signal they pick up.
Is it a cytokine?
It is usually classed as a growth factor rather than a cytokine, and the older reference entries that list it as both blur a useful line. Cytokine normally describes a protein that immune cells use to coordinate a response, while growth factors instruct ordinary tissue cells about division and survival. The boundary is genuinely fuzzy and some molecules sit on it, but EGF belongs on the tissue side. One further correction is worth making: EGF pushes cells to multiply and to migrate, and in several tissues it holds off specialization rather than encouraging it, so describing it as making cells differentiate reverses part of its effect.
Also known as
Used in a sentence
The tumor was tested for mutations affecting the EGF receptor.
Good to know
Treatment directed at this pathway blocks the receptor rather than the growth factor, and because the same receptor maintains normal skin, an acne-like rash is the characteristic accompanying effect.
Word origin
Where “EGF” comes from
Epidermal joins the Greek epi, meaning upon, with derma, skin, so the word describes the outer layer of the skin.