Breast cancer is clinically subdivided into receptor positive or negative tumors, (also known as triple negative breast cancer). Receptor positivity indicates a better prognosis as several specific agents to treat these tumors are available. Such agents, however, have been lacking for receptor negative tumors. To try to identify new agents that would specifically kill triple negative breast cancer cells, a team led by CeMM Principal Investigator Sebastian Nijman conducted a large chemical screen. They used carefully engineered breast cell lines that mimic triple negative breast cancer cells and systematically tested over 20 thousand chemicals. Several chemicals were identified but unraveling the molecular targets proved a challenging task. The interdisciplinary team of CeMM scientists and collaborators at the Moffitt Cancer Centre in the USA and the Val d’Hebron hospital in Barcelona nonetheless succeeded and identified the principal target of the compounds. The new breast cancer target called “Spleen Tyrosine Kinase” is well known for its role in cells of the immune system but an important role in breast cancer came as a complete surprise. Therefore, the discovery provides an opportunity for a new therapeutic strategy in this difficult to treat subset of breast cancer. The study was published in the scientific journal Molecular Systems Biology on 19 February 2015.