Once in the nucleus, the dimers bind to STAT5 response elements, inducing transcription of specific sets of genes.

[6] STAT5 has been found to be constitutively phosphorylated in cancer cells,[4] implying that the protein is always present in its active form.

For example, mutations may lead to increased expression of anti-apoptotic genes, the products of which actively prevent cell death.

Attempts at treatment for cancer cells with constitutively phosphorylated STAT5 have included both indirect and direct inhibition of STAT5 activity.

[11] The inhibition of proper dimerization, on the other hand, is brought about by the use of small molecules that target the SH2 domain.