Telomerase downregulation induces proapoptotic genes expression and initializes breast cancer cells apoptosis followed by DNA fragmentation in a cell type dependent manner

Rubiś, Błażej; Hołysz, Hanna; Gladych, Marta; Totoń, Ewa; Paszel, Anna; Lisiak, Natalia; Kaczmarek, Mariusz; Hofmann, Johann; Rybczyńska, Maria

doi:10.1007/s11033-013-2600-9

Cited by 23 publications

(18 citation statements)

References 36 publications

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“…Together, this indicates that repression of miR-296-5p and miR-512-5p in basal type breast cancer cells releases hTERT from miRNA dependent repression, to enhance resistance to apoptosis and telomere maintenance, thus promoting cancer cell aggressiveness. These results are in line with the induction of apoptosis markers upon classic siRNA mediated depletion of hTERT [ 10 , 11 ]. Recently, miR-512-5p has been shown to modulate the expression of the apoptosis regulator MCL-1, and miR-296-5p has been demonstrated to reduce cell proliferation of breast and prostate cancer cells by targeting SCRIB or HMGA1, respectively [ 35 , 36 , 42 ].…”

Section: Discussionsupporting

confidence: 77%

Epigenetic silencing of miR-296 and miR-512 ensures hTERT dependent apoptosis protection and telomere maintenance in basal-type breast cancer cells

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et al. 2017

Oncotarget

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The catalytic subunit of the telomerase complex, hTERT, ensures unlimited proliferative potential of cancer cells by maintaining telomere function and protecting from apoptosis. Using a miRNA screening approach we identified miR-296-5p and miR-512-5p as miRNAs that target hTERT in breast cancer cells. Ectopic miR-296-5p and miR-512-5p reduce telomerase activity, drive telomere shortening and cause proliferation defects by enhancing senescence and apoptosis in breast cancer cells. In line with the relevance of hTERT expression for human cancer we found that miR-296-5p and miR-512-5p expression is reduced in human breast cancer. Accordingly, high expression of miR-296-5p and miR-512-5p target genes including hTERT is linked with significantly reduced distant metastasis free survival and relapse free survival of basal type breast cancer patients. This suggests relevance of the identified miRNAs in basal type breast cancer. Epigenetic silencing of miR-296 and miR-512 encoding genes is responsible for low levels of miR-296-5p and miR-512-5p expression in basal type breast cancer cells. Disrupting gene silencing results in a dramatic upregulation of miR-296-5p and miR-512-5p levels leading to reduced hTERT expression and increased sensitivity to the induction of apoptosis. Altogether, our data suggest that epigenetic regulatory circuits in basal type breast cancer may contribute to high hTERT levels by silencing miR-296-5p and miR-512-5p expression, thereby contributing to the aggressiveness of basal type breast cancer.

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Section: Discussionsupporting

confidence: 77%

Epigenetic silencing of miR-296 and miR-512 ensures hTERT dependent apoptosis protection and telomere maintenance in basal-type breast cancer cells

Dinami

Buemi

Sestito³

et al. 2017

Oncotarget

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“…Furthermore, the modest reduction in viability occurred in an oligonucleotide sequenceindependent manner, indicating a minimal and nonspecific effect on normal cells. Long-term telomerase inhibition is known to induce downregulation of hTERT and associated downstream cellular effects, for example those leading to altered regulation of the proapoptotic pathway (35). However, in the short timescale necessary for reduction in clonogenic survival following treatment with radiolabeled oligonucleotides, no effect on hTERT expression was observed ( Supplementary Fig.…”

Section: Htr-targeted 111 In-labeled Oligonucleotides Reduce the Survmentioning

confidence: 99%

Radiolabeled Oligonucleotides Targeting the RNA Subunit of Telomerase Inhibit Telomerase and Induce DNA Damage in Telomerase-Positive Cancer Cells

et al. 2019

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Telomerase is expressed in the majority (>85%) of tumors, but has restricted expression in normal tissues. Long-term telomerase inhibition in malignant cells results in progressive telomere shortening and reduction in cell proliferation. Here we report the synthesis and characterization of radiolabeled oligonucleotides that target the RNA subunit of telomerase, hTR, simultaneously inhibiting enzymatic activity and delivering radiation intracellularly. Oligonucleotides complementary (Match) and noncomplementary (Scramble or Mismatch) to hTR were conjugated to diethylenetriaminepentaacetic dianhydride (DTPA), allowing radiolabeling with the Auger electron-emitting radionuclide indium-111 (111 In). Match oligonucleotides inhibited telomerase activity with high potency, which was not observed with Scramble or Mismatch oligonucleotides. DTPA-conjugation and 111 In-labeling did not change telomerase inhibition. In telomerase-positive cancer cells, unlabeled Match oligonucleotides had no effect on survival, however, 111 In-labeled Match oligonucleotides significantly reduced clonogenic survival and upregulated the DNA damage marker gH2AX. Minimal radiotoxicity and DNA damage was observed in telomerase-negative cells exposed to 111 In-Match oligonucleotides. Match oligonucleotides localized in close proximity to nuclear Cajal bodies in telomerasepositive cells. In comparison with Match oligonucleotides, 111 In-Scramble or 111 In-Mismatch oligonucleotides demonstrated reduced retention and negligible impact on cell survival. This study indicates the therapeutic activity of radiolabeled oligonucleotides that specifically target hTR through potent telomerase inhibition and DNA damage induction in telomerase-expressing cancer cells and paves the way for the development of novel oligonucleotide radiotherapeutics targeting telomerase-positive cancers. Significance: These findings present a novel radiolabeled oligonucleotide for targeting telomerase-positive cancer cells that exhibits dual activity by simultaneously inhibiting telomerase and promoting radiation-induced genomic DNA damage.

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“…The MCF-10A cell line is a spontaneously immortalised, but non-transformed human mammary epithelial cell line derived from breast tissue [ 28 ]. This cell line maintains telomere length through telomerase, but its expression is low [ 29 , 30 ], making it hard to see a clear band of hTERT by western blotting ( Supplementary Figure 1 ). Furthermore, despite being commonly recognised as normal cells, the karyotype is cytogenetically abnormal ( Supplementary Figure 2A ) and harbours genetic abnormalities commonly associated with cultured mammary epithelial cells such as deletion of the locus containing p16 INK4a and p14 ARF , as well as MYC amplification [ 31 , 32 ].…”

Section: Resultsmentioning

confidence: 99%

Acute telomere deprotection prevents ongoing BFB cycles and rampant instability in p16INK4a-deficient epithelial cells

et al. 2018

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Telomere dysfunction drives chromosome instability through endless breakage-fusion-bridge (BFB) cycles that promote the formation of highly rearranged genomes. However, reactivation of telomerase or ALT-pathway is required for genome stabilisation and full malignant transformation. To allow the unrestricted proliferation of cells at risk of transformation, we have established a conditional system of telomere deprotection in p16INK4a-deficient MCF-10A cells with modified checkpoints. After sustained expression of a dominant negative form of the shelterin protein TRF2 (TRF2ΔBΔM), cells with telomere fusion did progress to anaphase but no signs of ongoing BFB cycles were observed, thus anticipating proliferation defects. Indeed, 96 h TRF2ΔBΔM expression resulted in noticeable growth proliferation defects in the absence of cell cycle disturbances. Further transient periods of 96 h telomere uncapping did not result in cell cycle disturbances either. And reduction of the telomere damage to short acute deprotection periods did not in any case engender cells with a reorganised karyotype. Strikingly, the growth arrest imposed in cells showing dysfunctional telomeres was not accompanied by an activation of the DNA damage response at cellular level, or by the presence of visible markers of senescence or apoptosis. We propose that the deprotection of many telomeres simultaneously, even for a short time, results in a local activation of the cellular stress response which consequently triggers gradual cell withdrawal from cell cycle, restraining the onset of genomic instability.

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Telomerase downregulation induces proapoptotic genes expression and initializes breast cancer cells apoptosis followed by DNA fragmentation in a cell type dependent manner

Cited by 23 publications

References 36 publications

Epigenetic silencing of miR-296 and miR-512 ensures hTERT dependent apoptosis protection and telomere maintenance in basal-type breast cancer cells

Epigenetic silencing of miR-296 and miR-512 ensures hTERT dependent apoptosis protection and telomere maintenance in basal-type breast cancer cells

Radiolabeled Oligonucleotides Targeting the RNA Subunit of Telomerase Inhibit Telomerase and Induce DNA Damage in Telomerase-Positive Cancer Cells

Acute telomere deprotection prevents ongoing BFB cycles and rampant instability in p16INK4a-deficient epithelial cells

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