Identifying PAX2 as a natural barrier against invasion (and possibly, metastasis) in ERα+/luminal breast cancer cells, and showing that overexpression of PAX2, when it is followed by its activation, is sufficient to reduce cellular invasiveness of luminal breast cancer cells, is of clinical relevance considering that the majority of patients with breast cancer present with a luminal tumour and that metastasis is the main cause of death in breast cancer patients. The gene discussed is ESR1; the disease is breast cancer.