AIM2-responsive genes in colorectal tumor cells

Absent in Melanoma 2 (AIM2) is a member of the HIN-200 family of hematopoietic, IFN-inducible nuclear proteins associated with infection defense and tumor pathology. Recently, AIM2 was found to act as a DNA sensor in innate immunity. In addition, a high frequency of AIM2-alterations was observed in microsatellite unstable tumors. To elucidate AIM2 function in colorectal tumors, we here addressed AIM2-responsive genes by microarray. Among genes up-regulated by AIM2, there were a number of interferon-stimulated genes (ISGs: IFIT1, IFIT2, IFIT3, IFI6, IRF7, ISG15, HLA-DRA, HLA-DRB, TLR3 and CIITA) as well as genes involved in intercellular adhesion and matrix remodeling. Expression of ISGs correlated with expression of AIM2 in ten different IFN-γ treated colorectal cancer cell lines. Moreover, knock-down of AIM2 resulted in reduced expression of HLA-DRA, HLA-DRB, and CIITA in IFN-γ treated cells. IFN-γ independent induction of HLA-DR genes and their encoded proteins was also demonstrated upon transient induction of AIM2. STAT-signaling was not involved in IFN-γ independent induction of ISGs, arguing against participation of cytokines released in an autocrine manner. Our data indicate that AIM2 mediates IFN-γ dependent and independent induction of several Interferon stimulated genes (ISGs) including genes encoding the MHC II antigens HLA-DRα and β. we used microarray techniques to define genes responsive to AIM2 expression in colorectal tumor cells. HCT116 is a colorectal tumour cell line with no evidence for AIM2 expression which served as background for gene transfection. B8 and D1 were transfected subclones with persisting expression of AIM2. Gene expression of B8 and D1 was compared with that of mock transfected control cells.