NIEHS-supported scientists have identified a way that exposure to diesel exhaust stimulates the growth of cancerous tumors. Using a laboratory mouse research model, the research team determined that exposure to diesel exhaust particles stimulates the growth and formation of new blood vessels necessary for solid tumors to grow. The studies were carried out at exposure levels similar to those found in urban areas with heavy commuting traffic.
Most inhaled diesel exhaust particles are less than 0.1 micrometers in diameter, which enables them to penetrate the circulatory system and other organs and cause damage in just about any tissue in the body.
The researchers implanted small platforms embedded with normal endothelial cells, the cells that line blood vessels, under the skin of a group of healthy mice. In another set of mice, the researchers surgically created an ischemic condition in the hind limbs, resulting in a severe lack of oxygen.
Exposure to diesel exhaust for six hours per day caused a six-fold increase in new blood vessel formation in the ischemic limbs at eight weeks and a four-fold increase in the non-ischemic limbs compared to mice breathing normal air. Similar effects were seen in the mice with the implanted cells.
The team determined that exposure to diesel particles activates vascular endothelial growth factor, a chemical signal associated with new blood vessel development, and lowers activity for an enzyme involved in tumor suppression. The researchers are now conducting experiments to determine whether exposure to diesel exhaust influences metastasis of tumors as well.
Citation: Xu X, Kherada N, Hong X, Quan C, Zheng L, Wang A, Wold L, Lippmann M, Chen LC, Rajagopalan S, Sun Q. (http://www.ncbi.
2009. Diesel exhaust exposure induces angiogenesis. Toxicol Lett. Epub ahead of print.