Stimulation of mesothelioma markers in nanoparticle‐stressed pulmonary mesothelial cells

Response of the lung to carbon nanoparticle (CN) exposure has become important with increased CN industrial use. The nanofiber chains, created when CN are exposed to the aqueous pulmonary environment, have been compared in toxicity to asbestos, a known mesothelioma producer. With the hypothesis that CN‐stressed human mesothelial cells would secrete markers of mesothelioma, MeT‐5A (untransformed human mesothelial) cells were exposed to CN and NCI‐H28 human mesothelioma cells were the positive control. Two potential endpoint markers were selected: Mesothelin (clinical diagnostic mesothelioma assay) and osteopontin (a research mesothelioma marker). A dose‐response analysis of CN toxicity demonstrated that the best cell stress level utilized 25 micrograms CN per mL medium, producing 80% viability compared to untreated cells. Flasks were divided at confluency; aliquots of cells and supernatants were frozen for batch testing by ELISA for mesothelin and osteopontin. Cultures were continued for the lifespan of the MeT‐5A cells. Cell culture medium showed expression of both markers in the CN‐stressed cells but not in CN‐free controls. Mesothelin averaged 411.7 ng/mL (CN exposed) vs. 44.5 unexposed at 48 hr, p=0.03 ANOVA. Osteopontin appeared only at 24 h: 4.44 ng/mL CN‐exposed vs. 1.1 unexposed. NCI‐H28 mesothelioma cells released both markers after only overnight nanoparticle exposure, p<0.001 vs. unexposed cells. In summary, acute CN‐induced stress to MeT‐5A cells produces changes associated with secretion of mesothelioma markers. Processes involved in these cellular changes are under investigation in vivo. Sponsor: Saint Luke's Hospital Foundation, UMKC Sarah Morrison Grant