SMAD2 and neoplasm: Interestingly, three of the genes targeted by NUMTs with insertion polymorphism in humans are MADH2, a tumor-suppressor gene, mutated in colorectal carcinoma (Eppert et al. 1996; NUMT 18-192); a gene coding for a homologue of the thrombospondin gene (an angiogenesis inhibitor that retards tumor growth; Bogdanov et al. 1999; NUMT 1-74); and a mt ribosomal precursor (NUMT 13-75; Table 3).