Chromosomal Instability, Aneuploidy, and Gene Mutations in Human Sporadic Colorectal Adenomas

Whether in vivo specific gene mutations lead to chromosomal instability (CIN) and aneuploidy or viceversa is so far not proven. We hypothesized that aneuploidy among human sporadic colorectal adenomas and KRAS2 and APC mutations were not independent. Additionally, we investigated if 1p34–36 deletions by dual target FISH were associated with aneuploidy. Among 116 adenomas, 29 were DNA aneuploid by flow cytometry (25%) and 29 were KRAS2 mutated (25%). KRAS2 mutations were associated with aneuploidy (P = 0.02). However, while G–C and G–T transversions were strongly associated with DNA aneuploidy (P = 0.007), G–A transitions were not. Within a second series of 61 adenomas, we found, instead, that APC mutational status and aneuploidy by flow cytometry were not associated. However, a statistically significant association was found with specific APC mutations, i.e., occurring in the mutation cluster region (MCR, codons 1200–1500) or downstream (P = 0.016). Finally, the correlation of 1p34–36 deletions with flow cytometric and FISH detected aneuploidy was also significant (P = 0.01). Specific KRAS2 and APC mutations and loss of genes in the 1p34–36 region appear associated with aneuploidy suggesting that these events are not independent and may cooperate in inducing human sporadic colorectal adenomas. A cause effect relationship between gene mutations and aneuploidy remains, however, to be demonstrated.