Pulmonary Exposure To Multi-Walled Carbon Nanotubes Promotes Angiogenesis And Metastasis Of Breast Tumor

Exposure to multi-walled carbon nanotubes(MWCNT)by intratracheal instillation has been reported to induce pulmonary inflammation and fibrosis in the mice,which was implicated in the carcinogenesis of adjacent organ.However,it is still unclear whether pulmonary exposure to MWCNT should facilitate the growth and metastasis of tumors in distant organs.Our studies reported that long-term pulmonary exposure to MWCNT dramatically enhanced the angiogenesis of the orthotopically implanted mammary carcinoma and promoted the migration and invasion of the mammary carcinoma cells,which further promoted tumor metastasis into the lung in the Balb/c mice.We found that MWCNT exposure increased the serum levels of angiogenic factors,VEGFA and bFGF,and the raised VEGFA led to elevated expression of cyclooxygenase-2(COX-2)in the tumor cells and in turn upregulate VEGFA expression in our model,which formed positive loop of COX-2 and VEGFA.This work indicated that inhaled exposure to nanoparticles may promote tumor metastasis patients with breast cancers and expand toxic impact of nanoparticles on human health.