Effect of NF-kappaB RelB subunit expression on the biology of prostate cancer cells.

Abstract

e21052 Background: Our group previously observed the nuclear localization of the alternative NF-kB subunits RelB and p52 in tumor cells of prostate cancer (PCa) patients. These observations, based on immunohistochemistry analyses, suggest a constitutive activation of the alternative NF-kB pathway and a potential implication in PCa progression. The current study aims to define the role of the alternative NF-kB signaling in PCa by focusing on RelB, the alternative NF-kB subunit with a gene expression promoting transactivation domain. We used an over-expression system to assess its effects on the biology of a PCa cell line. Methods: PCa cell lines (LNCaP, 22Rv1, DU145 and PC3) express RelB differentially. Indeed, Western blot analyses clearly show a higher expression of RelB in DU145 and PC3 cells, while LNCaP and 22Rv1 cells do not express it. Using a lentivirus-based expression system, we introduced the cDNA of RelB into the 22Rv1 cells. We then assessed RelB’s effects on different cellular processes such as cell proliferation, migration, adhesion and 3D anchorage-independent cell growth (soft agar assay). Results: By introducing RelB into 22Rv1 cells using lentiviral infection, we induced the expression of RelB at a level comparable to those observed in DU145 and PC3 cell lines. Our results indicate that the expression of RelB doubles the cellular proliferation rate in 22Rv1 cells after 5 days of culture (p<0.05). However, RelB expression decreases the ability of the 22Rv1 cells to grow in 3D (p=0.002). Moreover, RelB over-expression halves the migration rate of 22Rv1 cells (p=0.017), but did not affect their adhesion on a matrix coated with type I collagen (p=0.183). Conclusions: This study reveals that in 22Rv1 cells, over-expression of RelB distinctly modifies proliferation, migration and 3D anchorage-independent growth. Ongoing in vivo experiments will determine how RelB expression affects the tumorigenic potential of 22Rv1 cells, thereby providing clues to its possible role in PCa.