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Telomeric DNA induces apoptosis and senescence of human breast carcinoma cells.

Yaar M, Eller MS, Panova I, Kubera J, Wee LH, Cowan KH, Gilchrest BA - Breast Cancer Res. (2007)

Bottom Line: We have identified an inducible cancer avoidance mechanism in cells that reduces mutation rate, reduces and delays carcinogenesis after carcinogen exposure, and induces apoptosis and/or senescence of already transformed cells by simultaneously activating multiple overlapping and redundant DNA damage response pathways.The human breast carcinoma cell line MCF-7, the adriamycin-resistant MCF-7 (Adr/MCF-7) cell line, as well as normal human mammary epithelial (NME) cells were treated with DNA oligonucleotides homologous to the telomere 3' overhang (T-oligos).Acting through ataxia telangiectasia mutated (ATM) and its downstream effectors, T-oligos induced apoptosis and senescence of MCF-7 cells but not NME cells, in which these signaling pathways were induced to a far lesser extent.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Dermatology, Boston University School of Medicine, Albany Street, Boston, MA 02118-2394, USA.

ABSTRACT

Introduction: Cancer is a leading cause of death in Americans. We have identified an inducible cancer avoidance mechanism in cells that reduces mutation rate, reduces and delays carcinogenesis after carcinogen exposure, and induces apoptosis and/or senescence of already transformed cells by simultaneously activating multiple overlapping and redundant DNA damage response pathways.

Methods: The human breast carcinoma cell line MCF-7, the adriamycin-resistant MCF-7 (Adr/MCF-7) cell line, as well as normal human mammary epithelial (NME) cells were treated with DNA oligonucleotides homologous to the telomere 3' overhang (T-oligos). SCID mice received intravenous injections of MCF-7 cells followed by intravenous administration of T-oligos.

Results: Acting through ataxia telangiectasia mutated (ATM) and its downstream effectors, T-oligos induced apoptosis and senescence of MCF-7 cells but not NME cells, in which these signaling pathways were induced to a far lesser extent. In MCF-7 cells, experimental telomere loop disruption caused identical responses, consistent with the hypothesis that T-oligos act by mimicking telomere overhang exposure. In vivo, T-oligos greatly prolonged survival of SCID mice following intravenous injection of human breast carcinoma cells.

Conclusion: By inducing DNA damage-like responses in MCF-7 cells, T-oligos provide insight into innate cancer avoidance mechanisms and may offer a novel approach to treatment of breast cancer and other malignancies.

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Related in: MedlinePlus

T-oligo induces apoptosis of MCF-7 cells. MCF-7 and normal mammary epithelial (NME) cells were treated as above. Apoptosis was determined by TUNEL analysis and by the level of cytoplasmic DNA-histone complexes 96 hours after a single treatment at time 0. (a) MCF-7 cells underwent apoptosis as observed by the prominent shift in fluorescent peak. (b) In contrast, there was only a minimal shift in the fluorescent peak of NME cells. (c) There is a significant increase in the levels of cytoplasmic DNA-histone complexes in T-oligo-treated MCF-7 cells compared to diluent-treated MCF-7 cells (p < 0.02, n = 3). In contrast, DNA-histone complexes in NME cells were not significantly increased above the background (Bkgd) level (p = 0.89).
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Figure 3: T-oligo induces apoptosis of MCF-7 cells. MCF-7 and normal mammary epithelial (NME) cells were treated as above. Apoptosis was determined by TUNEL analysis and by the level of cytoplasmic DNA-histone complexes 96 hours after a single treatment at time 0. (a) MCF-7 cells underwent apoptosis as observed by the prominent shift in fluorescent peak. (b) In contrast, there was only a minimal shift in the fluorescent peak of NME cells. (c) There is a significant increase in the levels of cytoplasmic DNA-histone complexes in T-oligo-treated MCF-7 cells compared to diluent-treated MCF-7 cells (p < 0.02, n = 3). In contrast, DNA-histone complexes in NME cells were not significantly increased above the background (Bkgd) level (p = 0.89).

Mentions: To determine if the T-oligo effect on cell yields in MCF-7 and NME cells is due to apoptosis in addition to S phase arrest, cultures were stimulated with T-oligo as above and TUNEL assays were performed and levels of cytoplasmic DNA-histones were determined 96 hours after stimulation (Figure 3). While in MCF-7 cells T-oligos induced substantial apoptosis, as shown by the prominent shift in the fluorescent peak (Figure 3a), in NME cells there was less of a shift (Figure 3b). In addition, the level of cytoplasmic DNA-histone complexes was significantly higher (p < 0.03) in T-oligo-treated MCF-7 cells than in NME cells (Figure 3c), in which the level of cytoplasmic DNA-histone complexes was identical to the background level (p = 0.9), showing that T-oligo induces significantly more apoptosis in MCF-7- than in NME cells, thus accounting for the greater reduction in cell yields.


Telomeric DNA induces apoptosis and senescence of human breast carcinoma cells.

Yaar M, Eller MS, Panova I, Kubera J, Wee LH, Cowan KH, Gilchrest BA - Breast Cancer Res. (2007)

T-oligo induces apoptosis of MCF-7 cells. MCF-7 and normal mammary epithelial (NME) cells were treated as above. Apoptosis was determined by TUNEL analysis and by the level of cytoplasmic DNA-histone complexes 96 hours after a single treatment at time 0. (a) MCF-7 cells underwent apoptosis as observed by the prominent shift in fluorescent peak. (b) In contrast, there was only a minimal shift in the fluorescent peak of NME cells. (c) There is a significant increase in the levels of cytoplasmic DNA-histone complexes in T-oligo-treated MCF-7 cells compared to diluent-treated MCF-7 cells (p < 0.02, n = 3). In contrast, DNA-histone complexes in NME cells were not significantly increased above the background (Bkgd) level (p = 0.89).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC1851376&req=5

Figure 3: T-oligo induces apoptosis of MCF-7 cells. MCF-7 and normal mammary epithelial (NME) cells were treated as above. Apoptosis was determined by TUNEL analysis and by the level of cytoplasmic DNA-histone complexes 96 hours after a single treatment at time 0. (a) MCF-7 cells underwent apoptosis as observed by the prominent shift in fluorescent peak. (b) In contrast, there was only a minimal shift in the fluorescent peak of NME cells. (c) There is a significant increase in the levels of cytoplasmic DNA-histone complexes in T-oligo-treated MCF-7 cells compared to diluent-treated MCF-7 cells (p < 0.02, n = 3). In contrast, DNA-histone complexes in NME cells were not significantly increased above the background (Bkgd) level (p = 0.89).
Mentions: To determine if the T-oligo effect on cell yields in MCF-7 and NME cells is due to apoptosis in addition to S phase arrest, cultures were stimulated with T-oligo as above and TUNEL assays were performed and levels of cytoplasmic DNA-histones were determined 96 hours after stimulation (Figure 3). While in MCF-7 cells T-oligos induced substantial apoptosis, as shown by the prominent shift in the fluorescent peak (Figure 3a), in NME cells there was less of a shift (Figure 3b). In addition, the level of cytoplasmic DNA-histone complexes was significantly higher (p < 0.03) in T-oligo-treated MCF-7 cells than in NME cells (Figure 3c), in which the level of cytoplasmic DNA-histone complexes was identical to the background level (p = 0.9), showing that T-oligo induces significantly more apoptosis in MCF-7- than in NME cells, thus accounting for the greater reduction in cell yields.

Bottom Line: We have identified an inducible cancer avoidance mechanism in cells that reduces mutation rate, reduces and delays carcinogenesis after carcinogen exposure, and induces apoptosis and/or senescence of already transformed cells by simultaneously activating multiple overlapping and redundant DNA damage response pathways.The human breast carcinoma cell line MCF-7, the adriamycin-resistant MCF-7 (Adr/MCF-7) cell line, as well as normal human mammary epithelial (NME) cells were treated with DNA oligonucleotides homologous to the telomere 3' overhang (T-oligos).Acting through ataxia telangiectasia mutated (ATM) and its downstream effectors, T-oligos induced apoptosis and senescence of MCF-7 cells but not NME cells, in which these signaling pathways were induced to a far lesser extent.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Dermatology, Boston University School of Medicine, Albany Street, Boston, MA 02118-2394, USA.

ABSTRACT

Introduction: Cancer is a leading cause of death in Americans. We have identified an inducible cancer avoidance mechanism in cells that reduces mutation rate, reduces and delays carcinogenesis after carcinogen exposure, and induces apoptosis and/or senescence of already transformed cells by simultaneously activating multiple overlapping and redundant DNA damage response pathways.

Methods: The human breast carcinoma cell line MCF-7, the adriamycin-resistant MCF-7 (Adr/MCF-7) cell line, as well as normal human mammary epithelial (NME) cells were treated with DNA oligonucleotides homologous to the telomere 3' overhang (T-oligos). SCID mice received intravenous injections of MCF-7 cells followed by intravenous administration of T-oligos.

Results: Acting through ataxia telangiectasia mutated (ATM) and its downstream effectors, T-oligos induced apoptosis and senescence of MCF-7 cells but not NME cells, in which these signaling pathways were induced to a far lesser extent. In MCF-7 cells, experimental telomere loop disruption caused identical responses, consistent with the hypothesis that T-oligos act by mimicking telomere overhang exposure. In vivo, T-oligos greatly prolonged survival of SCID mice following intravenous injection of human breast carcinoma cells.

Conclusion: By inducing DNA damage-like responses in MCF-7 cells, T-oligos provide insight into innate cancer avoidance mechanisms and may offer a novel approach to treatment of breast cancer and other malignancies.

Show MeSH
Related in: MedlinePlus