SIPA1L3 via its PDZ domain inhibits the tight junction-associated AMOT-Patj to promote a malignant phenotype in NSCLC.

BACKGROUND: Signal-induced proliferation-associated 1 like 3 (SIPA1L3) is a member of the protein family. Very limited data are currently available regarding the role of SIPA1L3 in human carcinoma. Therefore, in this study, we investigated the expression pattern and function of SIPA1L3 in non-small cell lung cancer (NSCLC). METHODS: We analyzed the distribution of SIPA1L3 in NSCLC specimens by immunohistochemistry, the relationship between SIPA1L3 expression and patient clinicopathological features, and investigated the effect of SIPA1L3 on cell growth and invasion in vivo and in vitro using small interfering RNA. Western blotting and immunoprecipitation were performed to demonstrate the interaction between SIPA1L3 and tight junction-associated angiomotin (AMOT) and Pals1-associtated tight junction protein. RESULTS: We found that SIPA1L3 was overexpressed in NSCLC clinical tissue samples and was associated with several clinicopathological factors. SIPA1L3 affects the proliferation and invasion of cancer cells both in vivo and in vitro. Using a SIPA1L3 mutant, we found that SIPA1L3 interacts with AMOT through its PDZ domain, which inhibits the binding of AMOT to Pals1-associtated tight junction protein and further decreases AMOT anchoring to tight junctions. CONCLUSION: Our findings suggested that SIPA1L3 promotes tumorigenesis in lung cancer cells through its PDZ domain-mediated interaction with AMOT, suggesting that SIPA1L3 is a novel candidate gene that contributes to the malignant phenotype of lung cancer.