Ligand

The term 'ligand' is a generic one. It is not specific to cancer. A ligand is something that binds to something else. Typically, the term is applied to the things that bind to cellular 'receptors' to turn the receptors on. As an example, estrogen (a lipid hormone) is the ligand for the estrogen receptor (a protein). Once the receptor has bound estrogen, it can do its job. In this case that would be to turn on and off a set of genes. Other receptor/ligand pairs do different things. They can make cells divide, make cells die, or do things less dramatic, like cause cells to take up nutrients from their environment.

As an aside, some cancer drugs work by blocking the interactions between cellular receptors and their ligands. Examples include tamoxifen, which blocks the estrogen receptor:estrogen interaction and Avastin® which blocks the VEGF:VEGF receptor interaction by binding to free VEGF. The term 'ligand' is a generic one. It is not specific to cancer. A ligand is something that binds to something else. Typically, the term is applied to the things that bind to cellular 'receptors' to turn the receptors on. As an example, estrogen (a lipid hormone) is the ligand for the estrogen receptor (a protein). Once the receptor has bound estrogen, it can do its job. In this case that would be to turn on and off a set of genes. Other receptor/ligand pairs do different things. They can make cells divide, make cells die, or do things less dramatic, like cause cells to take up nutrients from their environment.

As an aside, some cancer drugs work by blocking the interactions between cellular receptors and their ligands. Examples include tamoxifen, which blocks the estrogen receptor:estrogen interaction and Avastin® which blocks the VEGF:VEGF receptor interaction by binding to free VEGF.