SIAH1 and cancer: Siah3 mRNA transcript expression in several human cancer cell lines as shown in Fig. 7, raised the interesting possibility that nonfunctional SIAH3 may function as an endogenous SIAH inhibitor that regulates and antagonizes SIAH1 and SIAH2 biological activity through its DIMER domain to suppress and inhibit SIAH1 and SIAH2 biological activities to control cell proliferation, tissue growth, pattern formation, and homeostasis.