Radiosensitivity of human melanoma cell lines

R.M. BERGOC; V. MEDINA; G. CRICCO; N. MOHAMAD; G. MARTIN; M. NUÑEZ; M. CROCCI; CRESCENT, E; ES RIVERA.

Madrid, Spain

Congreso; XI International Radioprotection Congress of the International Radiation Protection Association; 2004

International Radiation Protection Association

Cutaneous melanoma is a skin cancer resulting from the malign transformation of skin pigmented cells, the melanocytes. The radiotherapy, alone or in combination with other treatments, is an important therapy for this disease. The objective of this paper was to determine in vitro the radiosensitivity of two human melanoma cell lines with different metastatic capability: WM35 and M1/15, and to study the effect of drugs on radiobiological parameters. The Survival Curves were adjusted to the mathematical Linear-quadratic model using GraphPad Prism software. Cells were seeded in RPMI medium (3000-3500 cells/flask), in triplicate and irradiated 24 h later. The irradiation was performed using an IBL 437C H Type equipment (189 TBq, 7.7 Gy/min) calibrated with a TLD 700 dosimeter. The range of Doses covered from 0 to 10 Gy and the colonies formed were counted at day 7th post-irradiation. Results obtained were: for WM35, α=0.37±0.07 Gy-1 and β=0.06±0.02 Gy-2; for M1/15, α=0.47±0.03 Gy- 1 and β=0.06±0.01 Gy-2. The α/β values WM35: α/β = 6.07 Gy and M1/15: α/β = 7.33 Gy were similar, independently of their metastatic capability and indicate that both lines exhibit high radioresintance. Microscopic observation of irradiated cells showed multinuclear cells with few morphologic changes non-compatible with apoptosis. By means of specific fluorescent dyes and flow cytometry analysis we determined the intracellular levels of the radicals superoxide and hydrogen peroxide and their modulation in response to ionizing radiation. The results showed a marked decreased in H2O2 intracellular levels with a simultaneous increase in superoxide that will be part of a mechanism responsible for induction of cell radioresistance. This response triggered by irradiated cells could not be abrogated by different treatments like histamine or the combination of oligoelements plus phospholipase (O-LM). poster