Role of cell cycle on analyzing telomerase activity with a fluorescence off-on system

Cancer is a significant cause of death worldwide and many efforts have been devoted to the development of methods for early detection. Telomerase are considered as a tumor biomarker for early diagnosis because the telomerase of more than 80% immortalized cells are reactivated and provides the sustained proliferative capacity of these cells, but the telomerase activity are not detectable in normal somatic cells. Telomerase is a ribonucleoprotein complex that is thought to add telomeric repeats onto the ends of chromosomes during the replicative phase (S phase) of the cell cycle.

Recently, Xia Wu, Jun Wu, Feng Wu, Xiaoding Lou, Fan Xia from the China University of Geosciences and Jun Dai, Biao Chen, Zhe Chen, Shixuan Wang from Huazhong University of Science and Technology made exciting progress and investigated the role of cell cycle progression on analyzing telomerase activity in cancer cells based on an AIEgen-based fluorescence detecting system. The fluorescence signal of cancer cells gradually increased from G0/G1, G1/S to S phase. In contrast, both cancer cells arrested at G2/M phase and normal cells exhibited the negligible fluorescence intensities, which demonstrates that future studies on tumor biomarkers analyzing, such as TERT mRNA and telomerase activity should consider the phase of cell cycle.

First, PyTPA-DNA and Silole-R bioprobe were used to investigate the expression of TERT mRNA and telomerase activity under different cell cycle of HeLa cells. Upon progression through the cell cycle, the PyTPA-DNA faintly fluoresced in G0/G1 stage but demonstrated an enhancement of fluorescence when responded to G1/S phase, finally reached the strongest output in S stage. However, cells arrested at G2/M phase showed the weakest fluorescence in contrast to the other three cell cycle. Furthermore, cell cycle-dependent alterations of TERT mRNA expression in HeLa cells was reconfirmed by qPCR. The similar responses of telomerase activity were also given by evaluated with using Silole-R bioprobe in different cell cycle. Moreover, TRAP assay was selectively analyzed and found to be the strongest expression levels in S stage.

Second, the intracellular imaging of TERT mRNA and telomerase activity during different stages of cancer cell cycle also demonstrated that the cell cycle has dramatic effects on the localization of TERT mRNA and telomerase activity, which S phase-specific boost and G2/M phase-specific reduce of TERT mRNA and telomerase activity in human cancer cells.

Then, the expression level of TERT mRNA and telomerase activity in different period of HeLa cells were compared with human lung fibroblasts (HFL-1) cells (normal cells) and found that somatic cells have almost no activation of telomerase during three phase of cell cycle. The level of TERT mRNA and active telomerase in most phases of cell cycle (G0/G1, G1/S, S) are above normal cells, while, cells arrested in G2/M phase exhibited almost the same level of normal cells.

In addition, a map of transcriptome information during different phases of cell cycle was performed. The parameters of CA9, CDKN1A, TK1 and EGFR were significantly elevated in G1/S stage and the activities of KRAS, CYC1 and PLOD3 were remarkably weakened in G0/G1 and G1/S phases. These results indicated that different tumor markers were highly diversified and varied in functions of different cell cycle.

It is worth noting that cell cycle served as a major role for the cellular processes and held the ability to modulate various biomarkers. These results, therefore, suggested that future studies on tumor biomarkers analyzing, such as TERT mRNA and telomerase activity should consider the phase of cell cycle.

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This research received funding from the National Key R&D Program of China (2020YFA0211200), the National Natural Science Foundation of China (21722507, 21525523, 21974128, 21874121), the Natural Science Foundation of Hubei Province (2019CFA043), the project funded by China Postdoctoral Science Foundation (2020M672436) and the Hubei Postdoctoral Innovative Research Foundation (to Jun Wu).

See the article:

Xia Wu, Jun Wu, Jun Dai, Biao Chen, Zhe Chen, Shixuan Wang, Feng Wu, Xiaoding Lou and Fan Xia

Role of cell cycle progression on analyzing telomerase in cancer cells based on aggregation-induced emission luminogens

Natl Sci Rev,2021, doi: 10.1093/nsr/nwaa306

https://doi.org/10.1093/nsr/nwaa306