Digest Journal of Nanomaterials and Biostructures Vol. 6, No 1, January-March 2011, p. 259-264 INVESTIGATION OF APOPTOSIS IN NORMAL AND LEUKEMIC CELLS INDUCED BY X-RAY IRRADIATION A. NEVOIE a* , M. PASCARIU a , D. JITARU b , I. IVANOV b,c , D. CONSTANTINESCU b,d , E. CARASEVICI b,c , T. LUCHIAN a a Faculty of Physics, “Al. I. Cuza” University, Iasi, Romania, b Laboratory of Immunology and Genetics, Hospital "St. Spiridon ", Iasi, Romania, c University of Medicine and Pharmacy "Gr T. Popa "Iasi, Romania d Public Health Institute, Iasi, Romania The aim of this work is the stydy of the functional changes of normal and leukemic cells exposed to X radiation. Normal mononuclear cells and two human leukemia cell lines (Jurkat and K562) were used for this study. The cells have been grown in the same medium and same conditions. To irradiate the human cells cultures, different doses were used. The process of programmed cell death, apoptosis, has been analyzed using the flow cytometry technique at 3, 24, 48 and 72 hours from irradiation. After 72 hours after the irradiation, the cells show the characteristic signs of apoptosis. (Received January 6, 2010; accepted January 26, 2011) Keywords: Normal mononuclear cell, Leukemia cell line, X-ray, Apoptosis, Dose rate. 1. Introduction Ionizing radiation has been used to treat human cancer [1]. The objective of radiotherapy is to kill cancer cells and to protect the surrounding normal tissue [1]. The total body irradiation is a external beam radiotherapy used in haematopoietic stem cell or bone marrow transplantation. It involves the irradiation of whole body and it represents radiation sterilization of tumoral cells, especially leukemic cells using high doses which range from 10 to more than 12 Gy. In modern practice, total body irradiation is fractionated. The research in bone marrow transplantation shows that if the total body irradiation dose is fractionated into smaller doses, the toxicity is smaller than in the case of a single dose [2-5]. Leukemic cells are very radiosensitive and they have a little or no capacity to repair the chromosomal abnormalities induced by ionizing radiation. However, the radiosensitivity varies from patient to patient [2]. The in vitro cellular systems are very used in radiobiology research, because the cellular and molecular interactions can be precisely controlled and manipulated. Ionizing radiation, induce chromosomal abnormalities including base pair deletion, cross-linking injuries, single and double strand break and multiple lesions appear [6]. Apoptosis plays an important role in tumor response to radiation [7, 8]. Therefore, low doses and repeated action protect normal cells. The ability to cure a tumor with ionizing radiation depends on various factors, most important is tumor cell radiosensitivity [9]. In the present study we proposed to follow the functional changes induced by X-rays with different doses at the cellular level in normal and tumor cell culture. Two human leukemia cell lines (Jurkat and K562) and normal mononuclear cell culture were used for this study.