title: Inhibition of poly (ADP-Ribose) polymerase-1 in telomerase deficient mouse embryonic fibroblasts increases arsenite-induced genome instability.
abstract: BACKGROUND
  The telomerase enzyme is a viable target for anti-cancer therapy given the innate differences in telomerase activity between tumour cells and normal somatic cells. However, the time lag between telomerase inhibition and telomeres becoming critically short to trigger cell death, allows cancer cells to acquire drug resistance. Inhibition of DNA repair pathways along with telomerase could be an alternative strategy to enhance anti-tumour effects and circumvent the possibility of drug resistance. Poly (ADP-Ribose) Polymerase-1 (PARP-1), an important DNA damage sensor and a DNA repair factor, has important roles in maintaining telomeres and chromosomal stability. In this study, the effects of combined inhibition of PARP-1 and telomerase in mouse embryonic fibroblasts (MEFs) following sodium arsenite exposure (a carcinogen and potent DNA damaging agent), were evaluated.
  
  
  RESULTS
  Inhibition of PARP in telomerase deficient MEFs induced an increase in arsenite-induced DNA damage as compared to control cells. Combined inhibition also resulted in enhanced genomic instability, demonstrated by elevated micronuclei induction and chromosomal aberrations with decreased cell survival. In addition, telomerase inhibition in PARP-1 deficient MEFs led to greater telomere shortening and increased genomic instability.
  
  
  CONCLUSIONS
  Our study demonstrated that the co-inhibition of PARP-1 and telomerase in MEFs rendered cells more susceptible to DNA damaging agents. Hence, these results offer support for the use of combined inhibition of PARP-1 and telomerase as a strategy to minimise the problems associated with long-term telomerase inhibition in cancer therapeutics.
authors.affiliation: Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117597. phsmph@nus.edu.sg.
authors.forename: Resham L
authors.initials: RL
authors.lastname: Gurung
authors.forename: Lakshmidevi
authors.initials: L
authors.lastname: Balakrishnan
authors.forename: Rabindra N
authors.initials: RN
authors.lastname: Bhattacharjee
authors.forename: Jayapal
authors.initials: J
authors.lastname: Manikandan
authors.forename: Srividya
authors.initials: S
authors.lastname: Swaminathan
authors.forename: M Prakash
authors.initials: MP
authors.lastname: Hande