No abstract

Deletion of the long arm of one chromosome 20 (del(20q)) is a well-recognized abnormality in acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS) and is presumed to cause loss of a tumor suppressor gene at 20q12. In a previously published series of MDS and AML cases, which had lost this region via unbalanced translocation, around 40% of cases were shown to have additional copies of the chromosome 20 abnormalities, with resulting gain or amplification of the retained parts of chromosome 20, most often 20q11.2. We have used FISH and array comparative genomic hybridization, to define further the retained and amplified regions. We now report targeted amplification of 20q11.21 in four of the 22 cases selected for further study and in one new case. The shortest amplified region of 250 kb in a series of five patients with three to ten copies of the 20q11.21 region contained the complete HCK, TM9SF4, PLAGL2, and POFUT1 genes. By RT-PCR we have shown that there is correlation between amplification and increased expression of these four genes in most cases. Localized and high level amplification of the common 250 kb region is evidence for activation of an oncogene in this region in these MDS and AML cases. Cases with 20q11.21 amplification tended to have a high proportion of erythroblasts in the marrow, with two cases diagnosed as erythroleukemia (AML-M6). Chromosome sub-band 20q11.21 amplification may therefore prove to be a marker of a specific subset of AML/MDS with a significant erythroid component.

ADP-ribosylation is an important posttranslational protein modification that regulates diverse biological processes, controlled by dedicated transferases and hydrolases. Here, we show that frequent deletions (∼30%) of the mono-ADP-ribosylhydrolase locus in human colorectal cancer cause impaired PARP1 transferase activity in a gene dosage-dependent manner. haploinsufficiency alters DNA repair and sensitivity to DNA damage and results in chromosome instability. Heterozygous and homozygous depletion of enhances intestinal tumorigenesis in mice and the growth of human colorectal cancer xenografts. deletion in sporadic colorectal cancer is associated with the extent of chromosome instability, independent of clinical parameters and other known genetic drivers. We conclude that acts as a haploinsufficient tumor suppressor, with loss of function promoting chromosome instability, thereby driving cancer evolution. Chromosome instability (CIN) is a hallmark of cancer. We identify deletion as a cause of CIN in human colorectal cancer. MACROD2 loss causes repression of PARP1 activity, impairing DNA repair. haploinsufficiency promotes CIN and intestinal tumor growth. Our results reveal as a major caretaker tumor suppressor gene..