TM4SF1 and liver cancer: Upregulation of MMP-2 and MMP-9 expression induced by TM4SF1 increases ECM degradation, leading to the invasion and metastasis of pancreatic and liver cancer cells (Huang et al., 2016; Yang et al., 2017), and dysregulated expression of discoidin domain receptor 1 (DDR1) can inhibit the expression of MMP-2 and MMP-9 when TM4SF1 is silenced in pancreatic cancer (Cao et al., 2016; Yang et al., 2017).