Bubbles against cancer
In experiments on mice, researchers at Thomas Jefferson University, working under the guidance of Dr. John Eisenbrey, demonstrated that the introduction of oxygen-filled microbubbles into a malignant breast tumor makes the tumor 3 times more susceptible to radiotherapy and improves the survival of animals.
An image of a round mammary tumor of a mouse model, along the thickness of which oxygen microbubbles (golden dots or specks) are distributed.
Microbubbles were originally developed to improve the efficiency of ultrasound imaging. However, the idea of introducing oxygen-filled microbubbles into the tumor using ultrasound seemed very promising to scientists.
The fact is that most solid tumors are depleted of oxygen, partly due to the fact that their size increases faster than new blood vessels are formed that can penetrate into the tumor mass.
Under the influence of radiation, oxygen contained in the tumor tissue reacts with various compounds to form reactive oxygen species and other free radicals. The less oxygen there is in the tissue, the less free radicals are formed and, accordingly, the less effective the therapy is. Thus, low oxygen levels make tumors resistant to radiation. According to Dr. Eisenbry, radiotherapy specialists have been working to solve this problem for more than 50 years.
As part of the work, the authors immediately before irradiation intravenously injected oxygen-filled microbubbles into mice with a simulated breast tumor, which were subsequently implanted into the tumor tissue under the local influence of ultrasound. It turned out to be interesting that this provided an increase in the level of molecular oxygen in the entire thickness of the tumor tissue, even in its regions that do not have direct blood supply.
According to subsequent observations, this manipulation can increase the susceptibility of the tumor to radiotherapy three times and almost double the survival rate of mice – up to 76 days compared to 46 days with placebo (nitrogen-filled microbubbles).
Currently, the authors are already testing a similar approach in a first-of-its-kind clinical study of microbubbles used to increase the effectiveness of radiotherapy for liver cancer. As part of the study, patients with liver cancer are injected with a microbubble contrast agent approved by the US Food and Drug Administration (FDA) in combination with standard methods of radioembolization therapy. Despite the fact that in this case the microbubbles do not contain oxygen, it is believed that their introduction causes the destruction of tumor tissue, increasing the effectiveness of combination therapy compared with the use of radioembolization alone.
Article by J.R. Eisenbrey et al. The sensitization of hypoxic tumors to radiation therapy using ultrasound sensitive oxygen microbubbles is published in the International Journal of Radiation Oncology.
Evgeniya Ryabtseva
Portal "Eternal youth" http://vechnayamolodost.ru based on the materials of Thomas Jefferson University: Microbubbles Make Breast Cancer More Susceptible to Radiation Therapy.