A new discovery has been made in cancer research. Researchers from the
Laboratoire des collisions atomiques et moléculaires (CNRS/Université
Paris 11) and the Laboratoire Génotoxicologie et cycle cellulaire
(CNRS/Institut Curie) were the first to show that it is possible to
improve hadrontherapy’s(1) targeting and destruction of
tumor cells by loading the cells with heavy atoms like platinum. This
new method enables both the treatment’s effectiveness and the ions’
ballistic effect to be improved without damaging healthy tissue.
One of the fundamental challenges in radiation therapy is to destroy
tumors with irradiation while preserving healthy tissue. With
hadrontherapy, the use of fast ions as ionizing particles offers a
major advantage because they deposit most of their energy in the tissue
at the end of their range. This method enables tumors to be destroyed
in a targeted manner by adjusting the initial energy of the particles.
Also, the ions used in this technique are more effective in destroying
cancerous tissue than conventional treatments (X-rays, for example).
In this work, the researchers combined, for the first time, ionic
radiation with platinum-enriched cells, using agents such as
cis-platinum(2), similar to molecules used in medicine. The
impact of the incident ions (protons, carbon) and the electrons ejected
along the way causes the platinum atoms to become highly ionized. The
process of electron capture and emission that ensues significantly
increases damage to surrounding molecules and considerably enhances
cell death rate. In the presence of platinum, the effectiveness of ions
at their end point is increased by at least 50 percent, thus improving
how well the tumor can be targeted.
These results suggest that the combination of hadrontherapy and the
addition of heavy atoms like platinum can improve both tumor targeting
and the effectiveness of cancer treatments while preserving healthy
tissue (the onset of toxicity results from the irradiation, and the
molecules used are not themselves toxic for the cell). This work paves
the way for research on new, non-toxic radiosensitizing agents –
molecules, nanoparticles, and lysosomes(3) –containing large numbers of atoms(4).
In practice, there are very few medical centers in the world
specializing in hadrontherapy because this new technique is still very
expensive. Researchers and clinicians at the Heavy Ion Medical
Accelerator (HIMAC) in Chiba, Japan, were the first to demonstrate the
effectiveness of carbon ions in therapeutic treatments. In France,
proton therapy at the Centre de protonthérapie at the Institut Curie
(Orsay) already makes it possible to treat certain cases of cancer that
cannot be cured by conventional methods. Another technology is
currently being developed that uses carbon ions, and although more
expensive, this technique is also more effective in certain cases. In
2012, a treatment center using carbon therapy will be opened in Lyon
(“Projet étoile”), which will improve cancer treatment.
(1) Hadrontherapy uses atomic ions (such as protons or carbon ions,
which are very effective in inducing therapeutic cell death) to treat
(2) Cis-platinum is a platinum-containing molecule that is frequently used in chemotherapy.
(3) Lysosomes are cellular components found in the cytoplasm. They contain proteins that break molecules and can destroy cells.
(4) In other words, high-Z atoms (atoms with a high atomic number,
i.e., that have a large number of protons and electrons). (Z=78 for
N. Usami, Y. Furusawa, K. Kobayashi, S. Lacombe, A Reynaud-Angelin,
E. Sage, Ting-Di Wu, A. Croisy, J-L. Guerquin-Kern and C. Le Sech.
Mammalian cells loaded with Platinum-containing molecules are
sensitised to fast atomic ions. International Journal of Radiation
Biology, 84, July 2008.
Source : CNRS. August 2008.