More than 45,000 new cases Lung Cancer They were diagnosed in France in 2018. Several factors may explain their occurrence: smokingExposure to carcinogens at work and pollution. In 2013, the World Health Organization, through the International Agency for Research on Cancer, classified air pollution and fine particulate matter as carcinogenic to humans. But the reasons for this link between cancer and air pollution remain uncertain. in review eLifea team of researchers from Nanjing University (China) provides explanations.

The indirect effect of pollution on cancer cells

Work on fine particles and its effects on human cells. “Recent research indicates that inhalable fine particles do not directly promote – and may inhibit – the growth of lung cancer cellsidentifies the lead author, Zhenzhen Wang, a research associate at Nanjing University (NJU). This indicates that inhaled microparticles can cause cancer through indirect means that promote tumor growth.. “With his team, he worked on a hypothesis previously put forward by other researchers: that microparticles could impede the movement and functioning of immune cells. To test this theory, they collected samples of the microparticles at seven Chinese sites, then tested them on immune cells whose role is to fight tumor growth, cytotoxic T cells (CTL), in an experiment conducted on mice. In mice given lung cancer cells that were not exposed to the microparticles, CTLs migrated to the lungs to destroy cancer cells. In contrast, in mice whose lungs were exposed to the particles, CTL infiltration was delayed, allowing tumor cells to establish themselves in lung tissue.

The cells are slowed down due to a change in the structure of the lung tissue

Second, the scientific team wanted to understand why CTLs do not enter the lungs so quickly, in case they are exposed to contamination. By studying these immune cells, they found that CTLs exposed to microparticles still retained their ability to migrate, but exposure to contamination greatly compressed the structure of lung tissue and the spaces between them. immune cells We are moving. Additional tissue analysis demonstrated that the structural changes were caused by increases in a subtype of collagen It is called collagen IV. By continuing their work, they found that exposure to microparticles causes changes in the action of an enzyme, peroxidacin, which is responsible for this increase in collagen production. “This means that wherever fine particles are present in the lungs, increased activity of peroxidacin leads to structural changes in lung tissue that can prevent immune cells from entering the developing cancer cells and hinder their growth.”Zhenzhen Wang confirms. According to him, these findings could allow the development of new approaches to prevent or treat the initial changes in the lung that lead to cancer.