A. H3 cells were cultured on pre-sterilized glass cover slips and then either mock (DMSO) or curcumin (30 μM)-treated for 1 hr. Cells were fixed, stained with Ser139 phospho-H2AX antibody (red), and counterstained with DAPI (blue). Also shown is the merged red/blue image. B. H3 cells were either mock (DMSO) treated or exposed to curcumin (30 μM) in the presence or absence of NAC (5 mM) as indicated. At the indicated time point, lysates were formed and immunoblotted with phospho-H2AX (S139) (top), phospho-ATM (S1981) (middle), or tubulin (bottom) antibody. C. ShLuc, shMSH2 and shMLH1 cells were either mock-treated or exposed to 30 μM curcumin and collected 4 hr after. Lysates were formed and immunoblotted with anti-phospho H2AX (S139) (top) or anti-tubulin (bottom) antibody. D. Proposed model for curcumin-induced checkpoint/apoptotic response.