PPP1R15A and colon carcinoma: In GANT61-treated human colon carcinoma cells, novel DNA damage-inducible transcripts DDIT3 (GADD153), DDIT4 (REDD1), DDIT2 (GADD45G), PPP1R15A (GADD34) and ATF3 were significantly up-regulated concomitant with the arrest of cells at G1/S.