Telomerase activation without shortening of telomeric 3'-overhang is a poor prognostic factor in human colorectal cancer

TPP1 is associated with risk of advanced precursors and cervical cancer survival

It is unclear how telomere-binding protein TPP1 interacts with human telomerase reverse transcriptase (hTERT) and influences cervical cancer development and progression. This study included all eligible 156 cervical cancers diagnosed during 2003-2008 and followed up through 2014, 102 cervical intraepithelial neoplasia (CIN) patients, and 16 participants with normal cervix identified at the same period. Correlation of expression of TPP1 and hTERT in these lesions was assessed using Kappa statistics. TPP1 was knocked down by siRNA in three cervical cancer cell lines. We assessed mRNA expression using quantitative real-time polymerase chain reaction and protein expression using tissue microarray-based immunohistochemical staining. We further analyzed the impact of TPP1 expression on the overall survival of cervical cancer patients by calculating the hazard ratio (HR) with 95% confidence intervals (CIs) using the multivariable-adjusted Cox regression model. Compared to the normal cervix, high TPP1expression was significantly associated with CIN 3 and cervical cancers (P<0.001 for both). Expressions of TPP1 and hTERT were highly correlated in CIN 3 (Kappa statistics = 0.50, P = 0.005), squamous cell carcinoma (Kappa statistics = 0.22, P = 0.011), and adenocarcinoma/adenosquamous carcinoma (Kappa statistics = 0.77, P = 0.001). Mechanistically, knockdown of TPP1 inhibited the expression of hTERT in both mRNA and protein levels. High expression of TPP1 (HR = 2.61, 95% CI 1.23-5.51) and co-high expression of TPP1 and hTERT (HR = 2.38, 95% CI 1.28-4.43) were independently associated with worse survival in cervical cancer patients. TPP1 and hTERT expression was correlated and high expression of TPP1 was associated with high risk of CIN 3 and cervical cancer and could predict a worse survival in cervical cancer.

Non-canonical roles of canonical telomere binding proteins in cancers

Reactivation of telomerase is a major hallmark observed in 90% of all cancers. Yet paradoxically, enhanced telomerase activity does not correlate with telomere length and cancers often possess short telomeres; suggestive of supplementary non-canonical roles that telomerase might play in the development of cancer. Moreover, studies have shown that aberrant expression of shelterin proteins coupled with their release from shortening telomeres can further promote cancer by mechanisms independent of their telomeric role. While targeting telomerase activity appears to be an attractive therapeutic option, this approach has failed in clinical trials due to undesirable cytotoxic effects on stem cells. To circumvent this concern, an alternative strategy could be to target the molecules involved in the non-canonical functions of telomeric proteins. In this review, we will focus on emerging evidence that has demonstrated the non-canonical roles of telomeric proteins and their impact on tumorigenesis. Furthermore, we aim to address current knowledge gaps in telomeric protein functions and propose future research approaches that can be undertaken to achieve this.

The predictive and prognostic potential of plasma telomerase reverse transcriptase (TERT) RNA in rectal cancer patients

BACKGROUND

Preoperative chemoradiotherapy (CRT) followed by surgery is the standard care for locally advanced rectal cancer, but tumour response to CRT and disease outcome are variable. The current study aimed to investigate the effectiveness of plasma telomerase reverse transcriptase (TERT) levels in predicting tumour response and clinical outcome.

METHODS

176 rectal cancer patients were included. Plasma samples were collected at baseline (before CRT=T0), 2 weeks after CRT was initiated (T1), post-CRT and before surgery (T2), and 4-8 months after surgery (T3) time points. Plasma TERT mRNA levels and total cell-free RNA were determined using real-time PCR.

RESULTS

Plasma levels of TERT were significantly lower at T2 (P<0.0001) in responders than in non-responders. Post-CRT TERT levels and the differences between pre- and post-CRT TERT levels independently predicted tumour response, and the prediction model had an area under curve of 0.80 (95% confidence interval (CI) 0.73-0.87). Multiple analysis demonstrated that patients with detectable TERT levels at T2 and T3 time points had a risk of disease progression 2.13 (95% CI 1.10-4.11)-fold and 4.55 (95% CI 1.48-13.95)-fold higher, respectively, than those with undetectable plasma TERT levels.

CONCLUSIONS

Plasma TERT levels are independent markers of tumour response and are prognostic of disease progression in rectal cancer patients who undergo neoadjuvant therapy.

Rho GDP-dissociation inhibitor α is a potential prognostic biomarker and controls telomere regulation in colorectal cancer

Rho GDP‐dissociation inhibitor α (RhoGDIα) is an essential regulator for Rho GTPases. Although RhoGDIα may serve as an oncogene in colorectal cancer (CRC), the underlying mechanism is still unclear. We investigated the function, mechanism, and clinical significance of RhoGDIα in CRC progression. We founded that downregulation of RhoGDIα repressed CRC cell proliferation, motility, and invasion. Overexpression of RhoGDIα increased DNA damage response signals at telomeres, and led to telomere shortening in CRC cells, also being validated in 26 pairs of CRC tissues. Mechanistic studies revealed that RhoGDIα could promote telomeric repeat factor 1 (TRF1) expression through the phosphatidylinositol 3‐kinase–protein kinase B signal pathway. Moreover, RhoGDIα protein levels were strongly correlated with TRF1 in CRC tissues. A cohort of 297 CRC samples validated the positive relationship between RhoGDIα and TRF1, and revealed that RhoGDIα and TRF1 levels were negatively associated with CRC patients' survival. Taken together, our results suggest that RhoGDIα regulate TRF1 and telomere length and may be novel prognostic biomarkers in colorectal cancer.

The Relationship between Telomerase Activity and Clinicopathological Parameters in Colorectal Cancer: A Meta-Analysis

BACKGROUND

Recently, accumulated research has found that the expression of telomerase activity (TA) was associated with colorectal cancer (CRC) advancement, whereas the TA prognostic effect in CRC patients is still controversial.

AIMS

To investigate relationships between TA and CRC clinicopathological parameters.

STUDY DESIGN

Meta-analysis study.

METHODS

We searched published studies in databases, such as EMBASE, the Cochrane Library, PubMed, and Ovid databases (last search updated to October 2014) by meeting specified search criteria. The quality of the included studies was usually evaluated and a meta-analysis was implemented by Stata 12.0 software. We used an odds ratio (OR) with a 95% confidence interval (CI) to evaluate relationship strengths between TA and CRC clinicopathological parameters.

RESULTS

In total, 11 studies (715 patients) were included to assess the relation between TA and metastasis-related parameters in CRC patients. The results indicate that a senior TA expression was connected with the existence of lymph node metastasis (180 patients; OR=2.85, 95% CI=1.40-5.81, p=0.004), and tumor site (522 patients; OR=2.93, 95% CI=1.29-6.67, p=0.010). However, a senior TA expression was not connected with tumor size (137 patients; OR=1.57, 95% CI=0.71-3.47, p=0.267), histological differentiation (570 patients; OR=1.28, 95% CI=0.78-2.09, p=0.332), depth of invasion (57 patients; OR=3.76, 95% CI=0.61-23.04, p=0.152), distant metastasis (123 patients; OR=1.76, 95% CI=0.54-5.74, p=0.346), and clinical stage of the cancer (543 patients; OR=1.59, 95% CI=0.74-3.38, p=0.232).

CONCLUSION

This meta-analysis suggests that a positive TA was correlated with lymph node metastasis progression and tumor site of the CRC but did not correlate with other important clinicopathological parameters. TA can play a useful part in the prognosis and treatment of CRC patients, but further studies are required to confirm this.

Telomeres, telomerase and colorectal cancer

Colorectal cancer (CRC) is the third most common cancer worldwide and, despite improved treatments, is still an important cause of cancer-related deaths. CRC encompasses a complex of diseases arising from a multi-step process of genetic and epigenetic events. Besides heterogeneity in the molecular and biological features of CRC, chromosomal instability is a hallmark of cancer and cancer cells may also circumvent replicative senescence and acquire the ability to sustain unlimited proliferation. Telomere/telomerase interplay is an important mechanism involved in both genomic stability and cellular replicative potential, and its dysfunction plays a key role in the oncogenetic process. The erosion of telomeres, mainly because of cell proliferation, may be accelerated by specific alterations in the genes involved in CRC, such as APC and MSH2. Although there is general agreement that the shortening of telomeres plays a role in the early steps of CRC carcinogenesis by promoting chromosomal instability, the prognostic role of telomere length in CRC is still under debate. The activation of telomerase reverse transcriptase (TERT), the catalytic component of the telomerase complex, allows cancer cells to grow indefinitely by maintaining the length of the telomeres, thus favouring tumour formation/progression. Several studies indicate that TERT increases with disease progression, and most studies suggest that telomerase is a useful prognostic factor. Plasma TERT mRNA may also be a promising marker for the minimally invasive monitoring of disease progression and response to therapy.

Telomerase is an independent prognostic marker of overall survival in patients with colorectal cancer

Background:

Colorectal cancer (CRC) is an important cause of cancer-related death. Prediction of recurrence is an important issue in the treatment of disease, particularly for stage II patients. The level of telomere-specific reverse transcriptase (hTERT), the catalytic component of the telomerase complex, increases along with CRC progression, but its prognostic value is still unclear.

Methods:

One hundred and thirty-seven CRC patients were studied for hTERT expression in tumour cells by real-time PCR. hTERT level was evaluated as a prognostic factor of overall survival (OS) in all patients and of disease recurrence in a subgroup of 50 stage II patients.

Results:

The median hTERT level was 93.8 copies (interquartile range 48–254). Patients with high hTERT levels (above the median) showed a significantly worse survival than those with low hTERT levels (below the median; log-rank test P<0.0001; hazard ratio (HR)=3.30 (95% confidence interval (CI) 1.98–5.52); P<0.0001). The negative prognostic value of high hTERT level is independent of the pathological stage and microsatellite instability (HR=2.09 (95% CI 1.20–3.64), P=0.009). Moreover, in stage II CRC, high hTERT levels identified patients with a higher risk of disease recurrence (HR=3.06 (95% CI 1.03–9.04), P=0.043) and death (HR=3.24 (95% CI 1.37–7.71), P=0.008).

Conclusion:

hTERT level is an independent prognostic marker of OS in CRC patients. In addition, assessment of hTERT level could improve stratification of stage II CRC patients for the risk of disease recurrence.

Shelterin complex and digestive system tumor

The Shelterin complex is the crucial components of telomere binding proteins. The regulation of this complex, together with telomerase and the alterative lengthening of telomeres (ALT mechanism), plays a critical role in maintaining telomere functions. Telomeres are DNA-protein complexes that contain short repeat sequences added on to the ends of chromosome by the telomerase for protecting the ends of chromosome and preventing chromosome fusion. The loss of protective function of telomeres is closely related to genome instability, and this is the molecular basis for tumor development. Thus, telomeres play key roles in the process of malignant tumor development. Many studies have shown that telomere binding proteins are associated with gastric, colorectal and liver cancers, and other digestive system tumors. This review will focus on the role of the shelterin complex in digestive system neoplasms to provide an insight into prevention and targeted therapy of these malignancies.