Importantly, a fragment of the intracellular domain of HER2, termed 611-CTF (carboxy terminal fragment), can constitutively homodimerize and regulate MET, EPHA2, matrix metalloproteinase 1, interleukin 11, angiopoietin-like 4, and different integrins, promoting mammary tumor growth and metastasis. The gene discussed is ERBB2; the disease is breast cancer.