Golgi tethering factor golgin-97 suppresses breast cancer cell invasiveness by modulating NF-κB activity

Background: Golgin-97 is a tethering factor in the trans-Golgi network (TGN) and is crucial for vesicular trafficking and maintaining cell polarity. However, the significance of golgin-97 in human diseases such as cancer remains unclear. Methods: We searched for a potential role of golgin-97 in cancers using Kaplan-Meier Plotter (http://kmplot.com) and Oncomine (www.oncomine.org) datasets. Specific functions of golgin-97 in migration and invasion were examined in golgin-97-knockdown and golgin-97-overexpressing cells. cDNA microarray, pathway analysis and qPCR were used to identify gene profiles regulated by golgin-97. The role of golgin-97 in NF-kappa B signaling pathway was examined by using subcellular fractionation, luciferase reporter assay, western blot analysis and immunofluorescence assay (IFA). Results: We found that low expression of golgin-97 correlated with poor overall survival of cancer patients and was associated with invasiveness in breast cancer cells. Golgin-97 knockdown promoted cell migration and invasion, whereas re-expression of golgin-97 restored the above phenotypes in breast cancer cells. Microarray and pathway analyses revealed that golgin-97 knockdown induced the expression of several invasion-promoting genes that were transcriptionally regulated by NF-kappa B p65. Mechanistically, golgin-97 knockdown significantly reduced I kappa Ba protein levels and activated NF-kappa B, whereas neither I kappa Ba levels nor NF-kappa B activity was changed in TGN46- or GCC185-knockdown cells. Conversely, golgin-97 overexpression suppressed NF-kappa B activity and restored the levels of I kappa Ba in golgin-97-knockdown cells. Interestingly, the results of Golgi-disturbing agent treatment revealed that the loss of Golgi integrity was not involved in the NF-kappa B activation induced by golgin-97 knockdown. Moreover, both TGN-bound and cytosolic golgin-97 inhibited NF-kappa B activation, indicating that golgin-97 functions as an NF-kappa B suppressor regardless of its subcellular localization. Conclusion: Our results collectively demonstrate a novel and suppressive role of golgin-97 in cancer invasiveness. We also provide a new avenue for exploring the relationship between the TGN, golgin-97 and NF-kappa B signaling in tumor progression.