TP53 and neoplasm: A homozygous deletion was detected in cell line RS0 involving two neighboring tumor suppressor genes Cdkn2a and Cdkn2b. This event is predicted to cause complete loss of function of the protein p19ARF, which is encoded by an alternative reading frame of Cdkn2a. p19ARF is a negative regulator of MDM2 and loss of p19ARF is known to cause indirect suppression of p53 through the ARF-MDM2-p53 tumor-suppressor axis (Eischen et al. 1999).