DDIT4 and cancer: Additional novel genes that are involved in stress response, and the response to DNA damage, not previously identified following termination of HH signaling in human cancer cells, include the early response genes DDIT2 (GADD45G), DDIT3 (GADD153), DDIT4 (REDD1), PPP1R15A (GADD34) and ATF3 that were significantly up-regulated.