Radiobiological analysis of human melanoma cells on the 62 MeV CATANA proton beam.
OBJECTIVE
To measure the ability of protons and gamma-rays to effect cell viability and cell survival of human HTB140 melanoma cells.


METHODS
Exponentially growing HTB140 cells were irradiated close to the Bragg peak maximum of the 62 MeV protons or with 60Co gamma-rays with single doses, ranging from 8 - 24 Gy. Cell viability using the 3-(4,5-dimethylthiazol-2yl)-2,5-diphenyltetrazolium bromide (MTT) assay was evaluated at 6 h, 24 h, 48 h or 7 days after irradiation and clonogenic survival was assessed at 7 days after irradiation. Cell cycle phase redistribution and the level of apoptosis were evaluated at 6 h and 48 h after irradiation.


RESULTS
The study of cell viability as a function of time (cell survival progression) and cell survival, using a clonal assay, demonstrated the considerably stronger inactivation effect of protons compared to gamma-rays with a relative biological effectiveness (RBE) of approximately 1.64. Cell cycle phase distribution and apoptosis levels with time enabled us to investigate the development and the character of the damage induced by irradiation. Due to the high radio-resistance of HTB140 cells, cell cycle phase redistribution exhibited only a modest cell accumulation in G2/M phase. Protons but not gamma-rays induced apoptosis.


CONCLUSIONS
It appears that protons reduce the number of HTB140 cells by apoptosis as well as by severe DNA damage, while gamma-rays eliminate viable cells primarily by the production of irreparable DNA damage. Protons have an increased RBE relative to gamma-rays.
Petrović
Ivan
I
Vinca Institute of Nuclear Sciences, Belgrade, Serbia and Montenegro.
Ristić-Fira
Aleksandra
A
Todorović
Danijela
D
Valastro
Lucia
L
Cirrone
Pablo
P
Cuttone
Giacomo
G
D017209:Apoptosis / Q000528:radiation effects; D002453:Cell Cycle / Q000528:radiation effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000528:radiation effects; D004273:DNA, Neoplasm / Q000235:genetics / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D008545:Melanoma / Q000235:genetics* / Q000473:pathology*; D011522:Protons; D011829:Radiation Dosage; D011853:Radiobiology / Q000379:methods
D004273:DNA, Neoplasm; D011522:Protons