APC and neoplasm: Furthermore, many tumor suppressors are singletons in the Pfam database, in the sense that their main domain can only be found in the genes themselves or in few other members (e.g., P53 Pfam, PF00870, is only shared by three genes TP53, TP63, TP73, Suppressor APC, PF11414, belongs to APC and APC2 only).