Pharmacological inhibition of DNA repair enzymes differentially modulates telomerase activity and apoptosis in two human leukaemia cell lines

• Published in: International journal of radiation biology Vol. 80; no. 8; pp. 593 - 605
• Main Authors: Dubner, D., del Rosario Pérez, M., Michelin, S., Bourguignon, M., Moreau, P., Carosella, E. D., Gisone, P.
• Format: Journal Article
• Language: English
• Published: England Informa UK Ltd 01.08.2004; Taylor & Francis
• Subjects: Androstadienes - pharmacology; Apoptosis - drug effects; Benzamides - pharmacology; Cell Cycle - drug effects; Cell Cycle - radiation effects; Cell Line, Tumor; DNA Repair - drug effects; Enzyme Inhibitors - pharmacology; Humans; Phosphatidylinositol 3-Kinases - antagonists & inhibitors; Poly(ADP-ribose) Polymerase Inhibitors; Space life sciences; Telomerase - antagonists & inhibitors
• ISSN: 0955-3002; 1362-3095
• DOI: 10.1080/09553000412331283506

Purpose: To investigate the effect of wortmannin and 3-aminobenzamide (3-AB) on telomerase activity and apoptosis in two human leukaemia cells. Materials and methods: MOLT-4 (p53-wild type) and KG1a (p53-null) cells were irradiated with γ-rays (3 Gy at 1.57 Gy min−1) and the effects of wortmannin and 3-AB were evaluated. Telomerase activity was measured by polymerase chain reaction and the expression of human telomerase reverse transcriptase, human telomerase RNA and telomerase-associated protein 1 was assessed by reverse transcriptase-polymerase chain reaction. Apoptosis was evaluated by fluorescence microscopy and flow cytometry. Results: A radiation-induced up-regulation of telomerase activity was observed from 4 h post-irradiation in both cell lines. This up-regulation was abrogated by wortmannin and 3-AB. Telomerase activity was maximal 24 h post-irradiation, coinciding with an accumulation of human telomerase reverse transcriptase mRNA. Apoptosis and G2 M arrest were evident from 4 h post-irradiation in MOLT-4 cells. KG1a cells exhibited a G2 M block at 24 h post-irradiation and apoptosis increased between 24 and 48 h post-irradiation. 3-AB abolished G2 M blockage and enhanced radiation-induced apoptosis in both cell lines, while wortmannin increased apoptosis only in MOLT-4 cells. Conclusions: 3-AB inhibits the radiation-associated telomerase activity increase and enhances apoptosis in MOLT-4 and KG1a cells. Wortmannin, which also inhibits the radiation-associated telomerase activity increase in both cell lines, does not modify radiation-induced apoptosis in KG1a cells. DNA repair enzymes might be selective targets for enhancing radiosensitivity in certain tumour cells.