Deregulation of methylation of transcribed-ultra conserved regions in colorectal cancer and their diagnostic and prognostic value.

Abstract

e15130 Background: Expression of Transcribed Ultra Conserved Regions (T-UCRs) is often deregulated in cancer. We investigated the role of three T-UCRs (Uc160, Uc283 and Uc346) in colorectal adenocarcinomas and their prognostic and diagnostic value. Methods: Expression and methylation levels of the T-UCRs were assessed in neoplastic and paired non-malignant fresh frozen (FF) tissue specimens from 64 colorectal cancer (CRC) patients, as well as in 6 FF adenoma tissue specimens. In addition, T-UCR methylation levels were assessed in FFPE tumor tissues from 80 CRC patients and in plasma from 161 patients (50 CRC, 59 adenoma patients, 40 healthy subjects and 12 patients with colon inflammation or diverticulosis). Results: Expression levels of all three T-UCRs were lower in neoplastic, compared to non-malignant tissues, although at a statistically significant level only for Uc160 ( p< 0.001). Also, methylation levels of Uc160, Uc283 and Uc346 were higher in tumors compared to non-malignant tissues ( p< 0.001, p= 0.001 and p= 0.004 respectively). Tissue methylation levels of Uc160 were associated with TTP ( p= 0.017). The combination of Uc283 and Uc346 methylation levels was related to OS, however without reaching statistical significance ( p= 0.066). Methylation status of Uc160 and Uc346 in plasma differed significantly among the four patient groups with CRC patients exhibiting the higher levels. Moreover, a strong correlation was found between Uc160 plasma methylation levels and adenoma or adenocarcinoma size and lymph node infiltration ( p< 0.001 and p= 0.024 respectively). When methylation status was used to predict if a subject has CRC, sensitivity and specificity were 35% and 89% respectively, while the values changed to 45% and 74.3% respectively when we combined the sum of the three T-UCR plasma methylation levels. For adenomas, the combination of Uc160 and Uc346 plasma methylation displayed 30.2% (sensitivity) and 80.7% (specificity). Conclusions: T-UCR expression and methylation is deregulated in CRC while their methylation has prognostic value and appears a promising non-invasive screening test for CRC and adenomas, provided that the sensitivity of the assay is improved.