MACROD2 Haploinsufficiency Impairs Catalytic Activity of PARP1 and Promotes Chromosome Instability and Growth of Intestinal Tumors

ADP-ribosylation is an important post-translational protein modification that regulates diverse biological processes, controlled by dedicated transferases and hydrolases. Here we show that frequent deletions (~30%) of the MACROD2 mono-ADP-ribosylhydrolase locus in human colorectal cancer (CRC) cause impaired PARP1 transferase activity in a gene dosage-dependent manner. MACROD2 haploinsufficiency alters DNA repair and sensitivity to DNA damage, and results in chromosome instability. Heterozygous and homozygous depletion of Macrod2 enhances intestinal tumorigenesis in ApcMin/+ mice and the growth of human CRC xenografts. MACROD2 deletion in sporadic CRC is associated with the extent of chromosome instability, independent of clinical parameters and other known genetic drivers. We conclude that MACROD2 acts as a haploinsufficient tumor suppressor, with loss of function promoting chromosome instability thereby driving cancer evolution. 651 colorectal cancer primary tumors were analyzed for DNA copy number profiles using Illumina Human610-Quad v1.0 BeadChip.