Cadmium poisoning has been known to result in a wide variety of cellular responses, including oxidative stress and kinase activation. It has been reported that ERK is activated following acute cadmium exposure, and this response is commonly seen as a classical ERK survival mechanism. Here, we analyzed different cell types for their responses to low concentrations of cadmium poisoning. We found that there is an association between cell susceptibility to cadmium toxicity and ERK activation. This activation is atypical, since it consists of a sustained ERK phosphorylation, that lasts up to 6 days post stimulation. This activation is associated with the appearance of cleaved caspases 8 and 3, processed PARP, and irreversible damage. Pharmacological inhibition of ERK phosphorylation results in the ability of cells to resist cadmium poisoning. Our data indicate that low cadmium concentrations result in an unconventional ERK sustained phosphorylation, which in turn leads to death signaling. (c) 2006 Elsevier Inc. All rights reserved.