The correlation between telomerase activity and Bax/Bcl-2 ratio in valproic acid-treated MCF-7 breast cancer cell line

Document Type : Original Article

Authors

Department of Biochemistry and Biophysics, Disorder Metabolic Research Center, Golestan University of Medical Sciences, Gorgan, Iran

Abstract

Objective(s):Valproic acid (VPA), a drug used in the treatment of neurological disorders, has been shown to have cytotoxic effects on cancer cells through different mechanisms. Telomerase, a ribonucleoprotein reverse transcriptase, is responsible for elongation of the telomere and is activated in cancers. A relation between telomerase activity and resistance to apoptosis has been established. This study focused on probable effects of VPA on MCF-7 cancer cells. In particular, we investigated VPA effects on viability, apoptosis and telomerase activity.
Materials and Methods: Cytotoxicity effects of VPA on MCF-7 cells were determined by neutral red uptake assay. Cells were treated with different concentrations of VPA (0-32 mM) and telomerase activity and Bax and Bcl-2 protein levels were determined using TRAP assay (PCR-ELISA) method and ELISA method, respectively.
Results: The cytotoxic effects of different concentration of VPA on MCF-7 cells were observed as a reduction in cell viability and telomerase activity and altered expression of Bcl-2 family protein levels. The results also showed that there is a significant correlation between reduction of telomerase activity and increase in Bax/Bcl-2 ratio (P=0.001).
Conclusion: Our study demonstrated that cell viability of MCF-7 cells was decreased after treatment with VPA, probably through a reduction of telomerase activity and an increase in Bax/bcl-2 ratio. Therefore, it could be concluded that VPA is a potent anti-cancer agent for breast cancer cells through inhibition of telomerase activity and induction of apoptosis.

Keywords

References

1. Jemal A, Bray F, Center MM, Ferlay J, Ward E, Forman D. Global cancer statistics. CA-Cancer J Clin 2011; 61:69-90.
2. Xia Q, Sung J, Chowdhury W, Chen C-l, Höti N, Shabbeer S, et al. Chronic administration of valproic acid inhibits prostate cancer cell growth in vitro and in vivo. Cancer Res 2006; 66:7237-7244.
3. Ververis K, Hiong A, Karagiannis TC, Licciardi PV. Histone deacetylase inhibitors (HDACIs): multitargeted anticancer agents. Biologics 2013; 7: 47–60.
4. Rahman R, Osteso-Ibanez T, Hirst RA, Levesley J, Kilday J-P, Quinn S, et al. Histone deacetylase inhibition attenuates cell growth with associated telomerase inhibition in high-grade childhood brain tumor cells. Mol Cancer Ther 2010; 9:2568-2581.
5. Rao Y, Xiong W, Liu H, Jia C, Zhang H, Cui Z, et al. Inhibition of telomerase activity by dominant-negative hTERT retards the growth of breast cancer cells. Breast Cancer 2014; 1-8.
6. Shay JW, Wright WE. Telomerase therapeutics for cancer: challenges and new directions.  Nat Rev Drug Discovery 2006; 5:577-584.
7. Wai LK. Telomeres, telomerase, and tumorigenesis--a review. Med Gen Med 2004; 6:19.
8. Massard C, Zermati Y, Pauleau A, Larochette N, Metivier D, Sabatier L, et al. hTERT: a novel endogenous inhibitor of the mitochondrial cell death pathway. Oncogene 2006; 25:4505-4514.
9. Buseman C, Wright W, Shay J. Is telomerase a viable target in cancer? Muta Res 2012; 730:90-97.
10. Woo HJ, Lee SJ, Choi BT, Park Y-M, Choi YH. Induction of apoptosis and inhibition of telomerase activity by trichostatin A, a histone deacetylase inhibitor, in human leukemic U937 cells. Expmolpathol 2007; 82:77-84.
11. Rubis B, Holysz H, Gladych M, Toton E,  Paszel A,  Lisiak N, et al. Telomerase downregulation induces proapoptotic genes expression and initializes breast cancer cells apoptosis followed by DNA fragmentation in a cell type dependent manner. Mol Biol Rep 2013; 40:4995-5004.
12. Kim NW, Piatyszek MA, Prowse KR, Harley CB, West MD, Ho PdL, et al. Specific association of human telomerase activity with immortal cells and cancer. Science 1994; 266:2011-2015.
13. Byun S-S, Kim FJ, Khandrika L, Kumar B, Koul S, Wilson S, et al. Differential effects of valproic acid on growth, proliferation and metastasis in HTB5 and HTB9 bladder cancer cell lines. Cancer let 2009; 281:196-202.
14. Fortunati N, Bertino S, Costantino L, Bosco O, Vercellinatto I, Catalano MG, et al. Valproic acid is a selective antiproliferative agent in estrogen-sensitive breast cancer cells. Cancer Lett 2008; 259:156-164.
15.  Li Y, Yin S, Feng S, Nie D, Xie S, Ma L, et al. [Effect of valproic acid on apoptosis of leukemia HL-60 cells and expression of h-tert gene]. Zhongguoshiyanxue ye Xuezazhi 2010; 18:1445-1450.
16. Khaw AK, Silasudjana M, Banerjee B, Suzuki M, Baskar R, Hande MP. Inhibition of telomerase activity and human telomerase reverse transcriptase gene expression by histone deacetylase inhibitor in human brain cancer cells. Mutat Res 2007; 625:134-144.
17. Wu P, Meng L, Wang H, Zhou J, Xu G, Wang S, et al. Role of hTERT in apoptosis of cervical cancer induced by histone deacetylase inhibitor. Biochem Biophys Res Commun 2005; 335:36-44.
18. Meeran SM, Patel SN, Tollefsbol TO. Sulforaphane causes epigenetic repression of hTERT expression in human breast cancer cell lines. PloS One 2010; 5:e11457.
19. Adams JM, Cory S. Bcl-2-regulated apoptosis: mechanism and therapeutic potential. Curr Opin Immunol 2007; 19:488-496.
20. Tsujimoto Y, Shimizu S. Role of the mitochondrial membrane permeability transition in cell death. Apoptosis 2007; 12:835-840.
21. Bokelmann I, Mahlknecht U. Valproic acid sensitizes chronic lymphocytic leukemia cells to apoptosis and restores the balance between pro-and antiapoptotic proteins. Mol Med 2008; 14:20-27.

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