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Zahra Habibi

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					  Radiotherapy with heavy ion beam in the presence of platinum as a radiosensitizer


                                    Z. Habibi Kelishomi


                                 Email: Zhabibi@ibb.ut.ac.ir


Introduction: Malignant tumors or cancers have now become one of the most frequent
causes of death in human society; hence, new protocols have been developed with the
purpose of focusing and maximizing the energy deposition of the ionizing particles into the
volume of the tumor. Methods: First: Experiments consist of irradiation of dried DNA in
vacuum with Ar ions at low keV energies for different time intervals. The DNA is analyzed
by agarose gel electrophoresis. Second: DNA Plasmids (pBR322) loaded with different
amounts of platinum contained in a terpyridine platinum chloride (PtTC) were irradiated by
C6+ ions and Fe 26+ ions. The Linear Energy Transfer (LET) values ranged between 13.4
keV/µm and 550 keV/µm. In some experiments, dimethyl sulfoxide was added. Third:
Chinese Hamster Ovary cells were incubated for six hours in medium containing 350 µM
terpyridine platinum chloride, and then irradiated by fast ions C6+ and He2+, with Linear
Energy Transfer within range 2–70 keV/µm. In some experiments, dimethyl sulfoxide was
added to investigate the role of free radicals. The intracellular localization of platinum was
determined by Nano Secondary Ion Mass Spectroscopy. Result: In all experiments, a
significant increase in DNA strand breaks was observed when platinum was present. Also,
experiments showed that for all LET examined, cell death rate is largely enhanced when
irradiating in presence of PtTC. They indicate that molecules containing high-Z elements
might act as sensitize. Discussion and conclusion: These findings show that more DNA
breaks are induced by atomic ions when platinum is present, and hadrontherapy or
protontherapy therapeutic index could be improved by combining irradiation procedure with
concomitant chemotherapy protocols using platinum salts.
Keywords: Hadrontherapy, Auger effect, Cancer therapy, radiosensitizing, platinum
compounds.



References

[1] K. Kobayashi, N. Usami, E. Porcel, S. Lacombe, C. Le Sech, Enhancement of radiation
effect by heavy elements, Mutation Research. 704 (2010) 123–131.
[2] S. Lacombe, C. Le Sech, Advances in radiation biology: radiosensitization in DNA and
living cells, Surf. Sci. 603 (2009) 1953–1960.

				
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