Immune cells in the blood previously exposed to asbestos increased the proliferation of mesothelial cells, according to a study published in the journal Oncology Letters, titled “The proliferative effects of asbestos-exposed peripheral blood mononuclear cells on mesothelial cells.”
Malignant mesothelioma (MM) is an aggressive tumor with a poor prognosis, thought to arise mainly from exposure to asbestos, a carcinogen that causes damage to the DNA, shifting the mesothelial cells toward a malignant state. Recent findings have shown that asbestos exposure can also modify cells from the immune system, suppressing their function and allowing the transformed cells to evade immune defenses, leading to MM development.
Patients with mesothelioma have been reported to have increased levels of specific cytokines — small molecules derived from the immune cells that have an important role in cell signaling. However, whether the production of these cytokines by immunocompetent cells could affect normal mesothelioma cells remained to be addressed.
Researchers from Japan analyzed the effects of asbestos exposure on immune cells isolated from blood, and whether they were producing cytokines that supported the proliferation of human mesothelioma cells. To achieve this, researchers exposed immune cells to two types of asbestos, chrysotile A and crocidolite, for seven days, after which they removed the supernatant (containing only the molecules released by the immune cells, such as cytokines), and used it to culture the mesothelioma cells.
The team found that the mesothelioma cells grown in the supernatant of cells exposed to asbestos exhibited increased proliferation. After analyzing the supernatant, researchers found markedly higher levels of specific cytokines, such as granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin (IL)-1α, IL-1β, IL-3, IL-5, IL-13 and IL-17A, often reported as pro-inflammatory cytokines.
Apart from G-CSF and GM-CSF, all these cytokines were able to induce mesothelioma cell growth when administered alone. However, such effect was not observed upon combined administration, revealing the need to identify the optimal combination of cytokines for the growth of mesothelioma cells or other secreted molecules that may be affecting those cells.
“The effects of cytokines produced by immune cells upon exposure to asbestos may contribute to the development of MM in individuals exposed to asbestos, in addition to the direct effect of asbestos on mesothelial cells,” the authors concluded. “Further studies are required to evaluate the association between immunological disturbances caused by asbestos and the pathogenesis of MM.”