PTPN1 and lung cancer: Similarly, in nonsmall cell lung cancer and gastric cancer, the expression of PTP1B is upregulated, leading to increased proliferation and metastasis of cancer cells through the activation of the Src/Ras/ERK and PI3K/AKT signaling pathways; however, when PTP1B is knocked down, cancer cell growth is inhibited, and cell cycle arrest and apoptosis are induced (Liu et al., 2015; Wang et al., 2015).