Background: The oncogenic single nucleotide polymorphism rs6983267, located on 8q24.21, may affect copy number aberrations and/or expression profiles in colorectal cancer (CRC). We investigated the role of this single nucleotide polymorphism in the clinical outcome of CRC.
Methods: Array comparative genomic hybridization (aCGH) and oligomicroarrays were performed on cancer cells from 157 primary CRC tissues. Expression profiles were analyzed by means of extraction expression module (EEM) analyses. Mutations in TP53, KRAS, and BRAF and microsatellite instability were also examined in 107 of the 157 cases.
Results: aCGH analysis revealed two clusters; more frequent genomic copy number alteration (CNA) was observed in the 89 cases in cluster B than in the 18 cases in cluster A. The average CNA was higher in samples containing the major allele (GT/TT) of rs6983267 than in those containing the minor allele (GG). Additionally, MYC expression was the highest in samples containing the GG allele (n = 18), followed by the GT and TT alleles (n = 41 and 48, respectively). EEM analysis revealed dominant up-regulation of MYC in samples containing the minor allele. Moreover, the presence of the minor allele in a MYC-positive, CNA-negative context predicted a poorer prognosis than the presence of the major allele in a MYC-negative, CNA-positive context in CRC.
Conclusions: The presence of the minor allele of rs6983267 at 8q24.21 worsened the prognosis of CRC through up-regulation of MYC transcription. Furthermore, progression of CRC may require global CNA in the presence of the major allele and with lack of MYC transcription.