Why EGCG hits several targets at once
Epigallocatechin gallate (EGCG) is the most abundant catechin in green tea and the most studied dietary polyphenol in cancer biology. In laboratory and animal models it interacts with multiple targets rather than one: it can suppress vascular endothelial growth factor (VEGF) signalling involved in tumour blood-vessel growth, inhibit matrix metalloproteinases (MMPs) that tumours use to invade tissue, and interfere with growth-factor receptors including HER2. This multi-target profile is what keeps it interesting to researchers.
The gap between cell studies and people
The important caveat is dose and bioavailability. The concentrations that produce these effects in a dish are far higher than what normal tea drinking achieves in blood, and human EGCG absorption is low and variable. Population studies linking green tea to cancer risk are inconsistent, and EGCG is not an established cancer treatment or preventive in humans.
High-dose EGCG supplements (as opposed to brewed tea) have been associated with liver injury in some reports. This is general educational information, not medical advice; cancer prevention and treatment decisions belong with a qualified oncologist.