CIId7, A Candidate Tumor Suppressor on Chromosome 13q14, Regulates Pathways of DNA Damage/Repair and Apoptosis

Chronic lymphocytic leukemia deletion gene 7 (CIId7) is a candidate tumor suppressor on chromosome 13q14. CIId7 encodes an evolutionarily conserved protein that contains an RCC1 domain plus broad complex, tramtrack, bric-a-brac (BTB), and POZ domains. In this study, we investigated the biological functions of CIId7 protein in inducible osteosarcoma cell lines. CIId7 induction inhibited cell growth, decreased cell viability, and increased gamma-H2AX staining under conditions of caspase inhibition, indicating activation of the DNA damage/repair pathway. Real-time PCR analysis in tumor cells and normal human epithelial cells revealed CIId7 target genes that regulate DNA repair responses. Furthermore, depletion of CIId7 in normal human epithelial cells conferred resistance to apoptosis triggered by DNA damage. Taken together, the biological actions of CIId7 are consistent with those of a tumor suppressor. Cancer Res; 70(22); 9434-43. (C) 2010 AACR.