As an example, among the prostate cancer samples, LOH at the NKX3.1 locus is more prevalent among real tumors and xenografts than among cell lines, LOH at the p53 locus is more prevalent among xenografts than among real tumors or cell lines, and LOH at the Rb locus is equally prevalent in all three groups (Figure 6). The gene discussed is RB1; the disease is prostate cancer.