PTP-PEST Regulated Membranous/Cytoplasmic Translocation of p120ctn in the Lung Cancer Resistance to Tyrosine Kinase Inhibitor

Our previous studies indicate that resistance induction using first-generation tyrosine kinase inhibitors (TKIs) in lung cancer is accompanied with p120-catenin (p120ctn) cytoplasmic translocation from the membrane. However, the molecular mechanism underlying p120ctn intracytoplasmic translocation has not yet been reported. We performed immunohistochemistry to detect the correlation of p120ctn distribution with protein tyrosine phosphatase non-receptor type 12 (PTP-PEST) and p120ctn Y335 phosphorylation levels in non-small cell lung cancer (NSCLC) patients. After resistance induction using first-generation TKIs in lung cancer cells, Western blotting and substrate trapping were used to assess PTP-PEST expression and its influence on p120ctn Y335 phosphorylation, as well as the role of p120ctn Y335 phosphorylation on the association of p120ctn with E-cadherin and p120ctn membrane/cytoplasm translocation. In 197 samples collected from NSCLC patients, cytoplasmic p120ctn and enhanced p120ctn Y335 phosphorylation were associated with decreased PTP-PEST. After resistance induction using gefitinib, decreased PTP-PEST expression was accompanied by enhanced phosphorylation of p120ctn Y335 and p120ctn translocated to the cytoplasm. In gefitinib-resistant cells, PTP-PEST overexpression restrained p120ctn Y335 phosphorylation and restored membrane p120ctn expression. PTP-PEST enhanced the interaction of p120ctn with E-cadherin and elevated p120ctn membrane expression. However, increased p120ctn-Y335F mutant had no effect on p120ctn interaction with E-cadherin and membrane/cytoplasm translocation compared with the control group. In conclusion, resistance to first-generation TKIs inhibited PTP-PEST expression, which promoted p120ctn-Y335 phosphorylation and reduced the interaction of p120ctn with E-cadherin, resulting in p120ctn cytoplasmic translocation.