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  • The decelerating age adjusted LTL attrition

    2018-11-13

    The decelerating age-adjusted LTL attrition in cancer cases as they approach diagnosis suggests that telomere ICG001 mechanisms may be activated in the blood due to cancer initiation. Telomere integrity is primarily maintained by telomerase, which catalyzes the synthesis of telomere repeats and adds telomere sequences onto chromosome ends. It is well known that telomere shortening is an early event in carcinogenesis. Critically shortened telomeres may trigger cellular senescence and apoptosis. Activation of telomerase occurs in the majority of cancers to counter-balance the critical shortening of telomeres in tumor cells, which can stabilize and elongate telomeres, overcome senescence and apoptosis, and increase cellular lifespan of malignant cells. Prior studies have also reported telomerase activity in normal and leukocytes (). Biologically, it is fathomable that individuals with higher telomere erosion rate over their early lifetime have increased cancer risks; however, as their LTL reaches a threshold and cancer is well on its trajectory of development, their telomere elongation mechanisms are hijacked to stabilize and elongate telomeres even in blood leukocytes, thus, providing better survival. Normal leukocytes benefit from telomere elongation mechanisms, resulting in longer LTL for cancer patients near their diagnosis. This divergence of LTL at some point before cancer ICG001 diagnosis has important implications in assessing the relationship of LTL with the cancer risks. Current literature in this regard all measured LTL at a single time point. The timing of blood collection was not strictly controlled. The above observation by indicates that the differences in sample collection time relative to cancer development and diagnosis will have a significant impact on assessing the association of LTL with cancer risks, which at least partially contributes to the inconsistency in literature. Future association studies of single time measurement of LTL should carefully control the timing of blood collection. More importantly, studies with multiple blood collection are warranted to establish the temporal associations between LTL and cancer risks, and to assess the dynamic changes of LTL in relation to cancer development. Due to the small sample size, this study of could only evaluate prostate cancer and the odds ratio is likely inflated. Whether a similar phenomenon occurs to other cancer types is unclear. Recent large cross-sectional studies and prospective studies have shown that both long LTL and short LTL can predispose individuals to increased cancer risks and the direction of association is not only cancer type-dependent, but also histology-dependent (). For example, long LTL was associated with an increased risk of lung adenocarcinoma, whereas short LTL was associated with a reduced risk of lung squamous cell carcinoma (). The study of adds additional complexity to the link of LTL to cancer risks. The cancer type- and histology-dependent association between LTL and cancer risks, accelerated age-related LTL shortening in cancer cases, and decelerating age-adjusted LTL attrition in cancer cases as they approach diagnosis, all point to a complex and dynamic relationship between LTL and cancer development. Future large, prospective, longitudinal studies are needed to confirm and extend the intriguing observations of . A full understanding of LTL epidemiology and cancer association will facilitate intervention efforts to prevent cancer and improve our lives through modulating telomere dynamics. Conflicts of Interest
    Colorectal cancer (CRC) is one of the leading causes of cancer death worldwide with the majority of cases having no previous family history. The most effective way to reduce mortality is to detect precancerous adenoma in an early stage. Several screening methods are now available; however as each modality has its limitation there is no superb strategy so far to conquer cancer death with colorectal cancer (). Fecal occult blood testing (FOBT) is the most widely employed screening tools, but sensitivity varies from 30% to 90% and depends on whether the specimens are rehydrated or not. The value of colonoscopy in screening can be appreciated, but it is costly and invasive. Moreover its effectiveness also depends on the endoscopist\'s skill. Computed tomographic colonoscopy (CTC) may another modality and rapidly evolving, but there are no controlled trials of screening CTC (). The risk of cumulative radiation exposure is also unknown. A special adaptation of capsule endoscopy has been developed to obtain images of the colon using tiny video cameras embedded in the two ends of an ingested capsule; however several studies have found a relatively low sensitivity for polyp detection (). Current serum markers are not sufficiently sensitive or specific to be used for screening.