The LIM protein AJUBA promotes colorectal cancer cell survival through suppression of JAK1/STAT1/IFIT2 network. Homo sapiens

Background and Aims: The LIM protein AJUBA participates in the regulation of cell adhesion, mitosis, DNA damage, cell differentiation, proliferation, migration and gene transcription, yet its roles in tumor development and progression are poorly defined. The aim is to determine the role of AJUBA in colorectal tumorigenesis. Methods: We performed data mining in Oncomine databases and immunohistochemistry (IHC) assays on 67 paired colorectal cancer (CRC) samples; we manipulated the AJUBA expression in SW-1116 and Caco-2 cells using specific shRNA and overexpression plasmids and performed assays for cell viability, cell cycle and apoptosis; we performed RNA-seq and qRT-PCR assays to identify genes regulated by AJUBA; we performed western blot, co-immunoprecipitation assays to study the interaction of AJUBA and JAK/STAT; Results: We discovered that AJUBA is highly expressed in CRC and promotes CRC cell growth in culture and in xenograted mice via an inhibition of apoptosis by repression of the IFIT2 gene. AJUBA specifically binds the FERM domain of JAK1 to dissociate JAK1 from the IFNγ recepter, resulted in inhibition of STAT1 phosporylation and concomitantly its nuclear translocation. Clinically, the level of AJUBA in CRC specimens is negatively correlated with the levels of IFIT2 and pSTAT1. Conclusion: Ajuba functions as a specific suppressor of the Interferon-activated JAK1/STAT1 signaling to promote colorectal cancer development via an inhibition of Interferon induced apoptosis. Overall design: RNA-seq assays to identify genes regulated by AJUBA in SW-1116 cancer cell lines. SW-1116-AJUBA OE and SW-1116-Vector cells were used for sequencing.