Functional studies of the genes composing the APA machinery have highlighted their relevance to tumor growth; for example, in glioblastoma, overexpression of the APA factor NUDT21 (a repressor of proximal 3′-UTR PAS usage) reduces tumor cell proliferation and inhibits tumor growth in vivo (Masamha et al. 2014). This evidence concerns the gene NUDT21 and neoplasm.