Gradient increases in selenium concentrations (1 μM to 10 μM) induce dose-dependent elevations in the amount and activity of thioredoxin reductase in non-resistant neoplastic cells while precipitating declines in thioredoxin reductase (e.g. doxorubicin-resistant small cell carcinoma) [140]. Here, PRDX5 is linked to small cell carcinoma.