Background: Runt-related transcription factor 1 (RUNX1), an essential regulator of hematopoiesis, is overexpressed in patients with nonsmall-cell lung cancer (NSCLC) and is correlated with enhanced metastatic ability. Ras-interacting protein 1 (Rasip1 ), a potential oncogene, is required for blood vessel formation, and recently, it has been shown that Rasip1  is widely expressed in NSCLC patients. We noticed that Rasip1  promoter contains several potential RUNX1-binding sequences. However, the relationship between Rasip1  and RUNX1 in NSCLC is still unknown. In this study, the potential function of RUNX1 involving in Rasip1 expression and the potential role of Rasip1 in lung cancer cells were investigated.
Materials and methods: Rasip1 and RUNX1 expressions were analyzed by quantitative reverse transcription polymerase chain reaction (qRT-PCR) and Western blotting in NSCLC cells lines. A549 and H1299 cells were transfected with plasmids or interfering RNA (siRNA) to upregulate or downregulate the expression of Rasip1 and RUNX1. Cell motility was assessed by transwell and wound-healing assay. Location of Rasip1 and RUNX1 was detected via immunofluorescence. Meanwhile, chromatin immunoprecipitation was done using an anti-RUNX1 antibody. Rasip1  promoter was constructed, and cells were lysed for the analysis of luciferase activity.
Results: In this study, we showed that ectopic expression or knockdown of RUNX1 resulted in a significant increase or reduction in Rasip1 expression, respectively. RUNX1 bound directly to a specific DNA sequence within Rasip1  promoter and modulated its transcription. Furthermore, silencing of Rasip1 inhibited the migration of RUNX1-overexpressing NSCLC cells through inactivation of Rac1 pathway. Moreover, we found that Rasip1  was expressed ubiquitously in NSCLC cells lines and enhanced cell migration. In addition, EGFR signaling was involved both in the expression and the subcellular localization of Rasip1 .
Conclusion: Our data indicated that Rasip1  is regulated in part by the transcription factor RUNX1 and might be developed as a therapeutic target for NSCLC.
Keywords: Rasip1, RUNX1, EGF, migration, nonsmall-cell lung cancer