Laser waves focused on the tumor area can damage cancer cells and blood vessels feeding them. The process becomes more efficient if nanoparticles are preliminary introduced into the tumor. At the conference “Nanotechnologies in Oncology in 2010”, Russian oncologists explained how laser irradiation is absorbed by nanoparticles, what particular nanoparticles should be used and to what extent their application increases therapeutic effect with animals suffering with cancer.

Pulsed laser hyperthermia is the tumor elimination method based on injecting sensitizers (nanoparticles) into the pathological tissue and further irradiation by high-energy laser pulses, the wave length of which is the area of applied nanoparticles absorption. Efficiency and mechanism of action of this approach were studied by specialists of the  Moscow Scientific Research Institute of Oncology named after P.A. Hertzen, State Research Center “NIOPIK” and the A.N. Frumkin Institute of Physical Chemistry and Electrochemistry. Andrei Pankratov and his colleagues investigated more than 15 nanostructure varieties of different chemical nature, structure and size. Nanoparticles of zinc phthalocyanine (ZnPc) were researched in most detail. The researchers have demonstrated that pulsed laser hyperthermia involving ZnPc particles use results in lengthy inhibition in growth of tumors of various nature: sarcomata, colon carcinoma, carcinoma of lung, melanoma. Part of the animals (from 10 to 70%, depending on cancer разновидности рака and investigated treatment method) has demonstrated complete recovery.

The mechanism of antitumoral action of pulsed laser hyperthermia with nanoparticles used as sensitizers has not been fully studied yet. The new research enables to state that the main reason of therapeutic effect is destruction of the tumor vascular system. When the tumor is laser-irradiated, nanoparticle microexplosions occur in blood vessels feeding it. The researchers have demonstrated that significant decrease of oxygen partial pressure is observed in the tumor tissues after irradiation: from 40-60 down to 0.5-5 mm of mercury. After irradiation is over, oxygen partial pressure level was not restored with the majority of animals that had underwent treatment with ZnPc particles. Blood vessel destruction in the tumor was also observed when investigation tissues under a microscope. A day after irradiation, blood vessel density in the tumor was almost 10 times lower than that in the reference group (unfortunately, several days after irradiation, vessel growth restarts in the tumor).

The researchers have also investigated safety of nanoparticles they used. They have demonstrated that ZnPc nanoparticles are removed from the blood flow within 3 hours, that the maximum endurable dose in case of intravenous induction exceeds the minimal dose necessary for treatment by 35 times, and that nanoparticles at the 0.2% concentration do not lead to blood corpuscle destruction. Nanoparticles are able to accumulate in the lungs, liver, kidneys and spleen, however, a year after nanoparticle injections, including those in high doses, the researchers did not reveal abnormal changes in these organs.

Source of information: Pankratov A.A., Andreeva T.N.., Yakubovskaya R.I., Kogan B.Ya., Butenin A.V., Feizulova R.A., Rudoi V.M. “Nanostructure composites for laser hyperthermia: various aspects of safety”. Report theses for the “Nanotechnologies in Oncology in 2010” conference.

Further information: Andrei Alexandrovich Pankratov, senior staff scientis, department of modifiers and protectors for antitumoral therapy, Moscow Scientific Research Institute of Oncology named after P.A. Hertzen. Tel. + 7(494)945-87-16, e-mail andreimnioi@yandex.ru.