Characterization of mouse embryonic fibroblasts derived from Rassf6 knockout mice reveals the implication of Rassf6 in the regulation of NF-κB signaling

RASSF6 is a member of the tumor suppressor Ras-association domain family (RASSF) proteins. We have reported using human cancer cell lines that RASSF6 induces apoptosis and cell cycle arrest via p53 and plays tumor-suppressive roles. In this study, we generated Rassf6 knockout mice by CRISPR/Cas technology. Contrary to our expectation, Rassf6 knockout mice were apparently healthy. However, Rassf6-null mouse embryonic fibroblasts (MEF) were resistant against ultraviolet (UV)-induced apoptosis/cell cycle arrest and senescence. UV-induced p53-target gene expression was compromised and DNA repair was delayed in Rassf6-null MEF. More importantly, KRAS active mutant promoted the colony formation of Rassf6-null MEF but not the wild-type MEF. RNA sequencing analysis revealed that NF-κB signaling was enhanced in Rassf6-null MEF. Consistently, 7,12-Dimethylbenz(a)anthracene (DMBA) induced skin inflammation in Rassf6 knockout mice more remarkably than in the wild-type mice. Hence, Rassf6 deficiency not only compromises p53 function but also enhances NF-κB signaling to lead to oncogenesis.