The RB1 Deletion probe consists of a 318kb red probe spanning the RB1 gene region. The 13qter probe in green acts as a control for chromosome 13.
Retinoblastoma (Rb) is a cancer of immature retina cells that occurs in inf ants and small children1. The protein encoded by the 180kb Retinoblastoma 1 (R B1) tumour suppressor gene, located on 13q14.2, may form complexes with oncoproteins and block their tumourigenic activity2. Deletion of this gene, particularly homozygous deletion, is therefore a causal event in the development of retinoblastoma. The RB1 gene also plays a role in secondary tumours aris ing in retinoblastoma patients, such as osteosarcoma and some soft tissue sarcomas3. The RB1 gene may also be deleted as a result of a progressional tumourigenic event in some leukaemias4, as well as in some breast, lung, bladder, oesophagus and prostate cancers5.