Carbon nanotubes(CNTs)are high-aspect ratio nanomaterials that have increasingly been used for a wide variety of industrial and commercial applications owing to their unique properties such as high tensile strength,extreme light weight,and high electrical and thermal conductivity.However,there is a great concern about the potential carcinogenicity of CNTs because of their properties such as biopersistence,needle-like shape and mode of exposure similar to asbestos fibers,which is a known human carcinogen causing lung cancer and mesothelioma.Our group has been investigating the long-term health effects of CNTs with a focus on lung cancer and mesothelioma.There is evidence that CNTs can gain access to the nucleus and cause genetic aberrations.Recent studies have shown that CNTs can induce or promote tumor formation in animals,suggesting their potential carcinogenicity in humans.Studies by our group indicate that CNTs can induce malignant transformation of human lung epithelial and mesothelial cells after chronic exposure in culture,as demonstrated by anchorage-independent cell growth,loss of contact inhibition,evasion of apoptosis,and increased cell invasion and migration activities,all of which are hallmarks of cancer cells.The transformed cells also induce tumor formation in mice,substantiating the tumorigenicity of CNTs.Furthermore,whole genome expression signature analysis identified oncogene signaling mechanisms in CNT-induced cell transformation that were substantially different from asbestos-exposed cell.This talk will focus on evidence of CNT carcinogenesis and examine the potential underlying mechanisms with the goal of developing mechanism-based risk assessment and early detection strategies.