Telomere shortening in non-tumorous and tumor mucosa is independently related to colorectal carcinogenesis in precancerous lesions.

Telomere shortening is associated with colorectal carcinogenesis and recent studies have focused on its characteristics in both normal mucosa and tumor tissues. To clarify the role of telomeres in colorectal carcinogenesis, we analyzed telomere shortening in normal and tumor regions of 93 colorectal precursor lesions. Telomere length was examined in 61 tubular adenomas (TAs) and 32 serrated polyps (SPs), and PIK3CA expression, KRAS mutation, BRAF mutation, and MSI were also analyzed. Telomere length was similar in normal and tumor tissues of TAs and SPs. In normal tissues of TAs, telomere shortening was associated with PIK3CA amplification (81.3% vs. 18.8%, p < 0.001), whereas it was associated with BRAF mutation in normal tissues of SPs (66.7% vs. 23.1%, p = 0.060). According to the analysis on tumor tissues, KRAS and BRAF mutations were mutually exclusive in TAs and SPs (p < 0.001), and telomere shortening was associated with mitochondrial microsatellite instability (63.6% vs. 36.4%, p = 0.030). These data suggested a pivotal role of telomere shortening in normal colorectal tissue for proceeding to TAs or SPs along with PIK3CA amplification and BRAF mutation, respectively. Moreover, telomeres in TAs may collaborate with mitochondrial instability for disease progression.