Cancer is an ongoing challenge for doctors, especially in the diagnosis and treatment of diseases. This is due, inter alia, to tumor heterogeneity. The team of scientists from Helmholtz Zentrum Muenchen, the Juelich Research Center, the Technical University of Munich and the Heinrich Heine University in Düsseldorf have now demonstrated that the harmless purple bacteria of Rhodobacter can visualize some aspects of this. The heterogeneity of the tumor. With the help of photoacoustic imaging, the researchers used these microbes to observe the cells of the immune system, the so-called macrophages* (Greek is the "big eater"), which also play a role in tumor development. Their findings are now published in Nature Communications .
Many cancers form solid tumors. Internally, this tumor reveals major differences in cellular and molecular levels. One of them involves the localization and activity of macrophages. Although these cells are critical for a healthy immune system, they also play a key role in tumor development. With the help of photosynthetic bacteria, new photoacoustic techniques have now been developed that indicate the presence and active location of such macrophages.
"We can prove that the bacteria of the Rhodobacter ** genus that are harmless to humans are suitable as indirect markers for the presence and activity of macrophages," said Dr. Andre C. Stiel, Institute of Biological and Medical Imaging. (IBMI) Head of the Cell Engineering Group, HelmholtzZentrum München. Rhodobacter Bacteria produce a large amount of photosynthetic pigment bacteria chlorophyll a. This pigment allows researchers to detect bacteria in tumors by multispectral photoacoustic tomography (MSOT)***.
How does this principle work? Macrophage phagocytic bacteria are part of their natural scavenging activity and are known as phagocytosis. This changes the surrounding environment of the bacteria, their absorption of electromagnetic radiation, and therefore also the photoacoustic signal. Therefore, Rhodobacter bacteria, like scientists' sensors, provide them with information about the presence and activity of macrophages.
"In a further step, these bacteria will provide new methods for non-invasive techniques, opening up entirely new possibilities for innovative diagnostic and therapeutic procedures," Benedict Heiner University Bacterial Photobiotechnology Group The person in charge, Dr. Thomas Drepper added. Düsseldorf. In the future, bacteria may be able to reveal the location of the tumor and also be able to detect increased macrophage activity. Based on their location, macrophages can provide information about unwanted inflammation or desired responses to immunotherapy and can ultimately be used to improve treatment strategies.
* As is known today, tumors have a specific microenvironment. One component of the tumor microenvironment is tumor-associated macrophages. These scavenger cells are part of our immune system, but in the case of cancer, they are involved in unnecessary inflammation of the tumor tissue – a process that leads to further disease progression.
** Rhodobacter occurs in stagnant and flowing waters worldwide. Bacteria produce different pigments for photosynthesis. These include the bacterial chlorophyll a, which is suitable for MSOT examination to localize solid tumors. Rhodobacter Cells do not cause human infection.
*** During an MSOT scan, the light is initially converted to sound and then converted to visual information. Initially, a weak pulsating laser beam is directed at the body. When the beam encounters molecules and cells, they are heated to a minimum and respond with minimal vibration, which in turn produces an acoustic signal. These are then picked up by the sensor and converted into an image. The manner in which individual cells and molecules react to the laser depends on their optical properties – in this case, for example, the nature of the bacterial pigment.
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