Mutant cohesin drives chromosomal instability in early colorectal adenomas

Chromosome missegregation leads to chromosomal instability, thought to play a role in cancer development. As cohesin functions in guaranteeing correct chromosome segregation, increasing data suggests its involvement in tumorigenesis. In a screen of a large series of early colorectal adenomas, a precocious step during colorectal tumorigenesis, we identified eleven mutations in SMC1A core cohesin subunit. In addition, we sequenced the SMC1A gene in colorectal carcinomas and we found only one mutation. Finally, the transfection of the SMC1A mutations identified in early adenomas and wild-type SMC1A gene silencing in normal human fibroblasts led to chromosomal instability. Our findings that SMC1A mutations decrease from early adenomas to colorectal cancers and that mutations lead to chromosomal instability suggest that mutant cohesin could play a pivotal role during colorectal cancer development.