Determining if telomeres matter in colon cancer initiation or progression

Expression of Stem Cell Markers in High-LET Space Radiation-Induced Intestinal Tumors in Apc1638N/+ Mouse Intestine

Estimation of cancer risk among astronauts planning to undertake future deep-space missions requires understanding the quantitative and qualitative differences in radiogenic cancers after low- and high-LET radiation exposures. Previously, we reported a multifold higher RBE for high-LET radiation-induced gastrointestinal (GI) tumorigenesis in Apc1638N/+ mice. Using the same model system, i.e., Apc1638N/+ mice, here, we report qualitative differences in the cellular phenotype of low- and high-LET radiation-induced GI tumors. Stem cell (SC) phenotypes were identified using BMI1, ALDH1, CD133, DCLK1, MSI1, and LGR5 markers in low (γ-rays)- and high (56Fe)-LET radiation-induced and spontaneous tumors. We also assessed the expression of these markers in the adjacent normal mucosa. All six of these putative SC markers were shown to be overexpressed in tumors compared to the adjacent normal intestinal tissue. A differential SC phenotype for spontaneous and radiogenic intestinal tumors in Apc1638N/+ mice was observed, where the ALDH1, BMI1, CD133, MSI1, and DCLK1 expressing cells were increased, while LGR5 expressing cells were decreased in 56Fe-induced tumors compared to γ-ray-induced and spontaneous tumors. Furthermore, higher β-catenin activation (marked by nuclear localization) was observed in 56Fe-induced tumors compared to γ and spontaneous tumors. Since differential tumor cell phenotype along with activated β-catenin may very well affect malignant progression, our findings are relevant to understanding the higher carcinogenic risk of high-LET radiation. This study has implications for the assessment of GI-cancer risk among astronauts, as well as for the estimation of secondary cancer risk among patients receiving hadron therapy, considering that our results indicate increased stemness properties after radiation.

The TERT promoter SNP rs2853669 decreases E2F1 transcription factor binding and increases mortality and recurrence risks in liver cancer

A common single-nucleotide polymorphism in the telomerase reverse transcriptase (TERT) promoter, rs2853669 influences patient survival rates and the risk of developing cancer. Recently, several lines of evidence suggest that the rs2853669 suppresses TERT promoter mutation-mediated TERT expression levels and cancer mortality as well as recurrence rates. However, no reports are available on the impact of rs2853669 on TERT expression in hepatocellular carcinoma (HCC) and its association with patient survival. Here, we found that HCC-related overall and recurrence-free survival rates were not associated with TERT promoter mutation individually, but rs2853669 and the TERT promoter mutation in combination were associated with poor survival rates. TERT mRNA expression and telomere fluorescence levels were greater in patients with HCC who had both the combination. The combination caused TERT promoter methylation through regulating the binding of DNA methyltransferase 1 and histone deacetylase 1 to the TERT promoter in HCC cell lines. The TERT expression level was significantly higher in HCC tumor with a methylated promoter than in that with an unmethylated promoter. In conclusion, we demonstrate a substantial role for the rs2853669 in HCC with TERT promoter mutation, which suggests that the combination of the rs2853669 and the mutation indicate poor prognoses in liver cancer.

The relationship between telomere length and clinicopathologic characteristics in colorectal cancers among Tunisian patients

Alterations in telomere dynamics have emerged as having a causative role in carcinogenesis. Both the telomere attrition contribute to tumor initiation via increasing chromosomal instability and that the telomere elongation induces cell immortalization and leads to tumor progression. The objectives of this study are to investigate the dynamics of telomere length in colorectal cancer (CRC) and the clinicopathological parameters implicated. We measured the relative telomere length (RTL) in cancerous tissues and in corresponding peripheral blood leukocytes (PBL) using quantitative PCR (Q-PCR) from 94 patients with CRC. Telomere length correlated significantly in cancer tissues and corresponding PBL (r = 0.705). Overall, cancer tissue had shorter telomeres than PBL (p = 0.033). In both cancer tissue and PBL, the RTL was significantly correlated with age groups (p = 0.008 and p = 0.012, respectively). The RTL in cancer tissue was significantly longer in rectal tumors (p = 0.04) and in the late stage of tumors (p = 0.01). In PBL, the RTL was significantly correlated with the macroscopic aspect of tumors (p = 0.02). In addition, the telomere-length ratio of cancer to corresponding PBL increased significantly with late-stage groups. Shortening of the telomere was detected in 44.7%, elongation in 36.2%, and telomeres were unchanged in 19.1% of 94 tumors. Telomere shortening occurred more frequently in the early stage of tumors (p = 0.01). This study suggests that the telomere length in PBL is affected by the macroscopic aspect of tumors and that telomere length in cancer tissues is a marker for progression of CRC and depends on tumor-origin site.

In colon cancer, normal colon tissue and blood cells have altered telomere lengths

BACKGROUND

Telomere length (TL) shortened occurs in colorectal carcinogenetic process. Our objective is to determine if it is only a local fact or there are alterations in normal colon cells and in other body cells.

METHODS

TL of tumoral and normal mucosa and leukocytes of 40 patients operated of colorectal cancer (CRC) and 40 control patients with normal colonoscopy were measured by Southern-blot. Groups were matched by the same localization as tumors, sex, and age.

RESULTS

In CRC patients, TRFL (Telomere Repeat Factor Length) leukocytes mean was 8.84 kpb, normal colonic mucosa 7.97 kpb, and tumoral mucosa 7.33 kpb (P < 0.001). In the 40 normal control patients, mean TRFL of colonic mucosa was 7.76 kpb, while in blood cells was 7.01 kpb (P < 0.001). We observed an inverse correlation between leukocytes TRFL and age (r(2)  = 0.17, P = 0.008). Mucosa TRFL correlates significantly with patient's age (r(2)  = 0.138, P = 0.018). TRFL of controls colonic mucosa correlates with TRFL of their blood cells (r(2)  = 0.354, P < 0.001).

CONCLUSIONS

Normal colonic mucosa and leukocytes in CCR patients presents telomere altered in respect to normal patients. Telomere length in normal leukocytes could be an initial marker for colorectal cancer.