PFN1 and neoplasm: Despite being an essential actin-binding protein, Pfn1 simultaneously functions as a non-classical tumor suppressor across different malignancies including breast (Roy and Jacobson, 2004; Wittenmayer et al., 2004; Zou et al., 2007, 2009, 2010; Bae et al., 2009, 2010; Das et al., 2009; Diamond et al., 2015), pancreatic (Yao et al., 2014), and liver (Wu et al., 2006) cancers.