Inhibition of the proliferation of human neural neoplastic cell lines by cysteamine

Cysteamine (CySH), a thiol compound that crosses the blood-brain barrier, inhibited the proliferation of neural neoplastic cells in vitro. The IC50 of cysteamine with respect to inhibition after 72 h of drug exposure, was ~70 μM in the glioma cell line, 2607, and ~80 μM in the neuroblastoma cell line, DAOY. Interestingly, the inhibition of proliferation of 2607 cells produced by 72 h treatment with CySH could also be induced with exposure periods as short as 8 h. Another thiol bearing compound, penicillamine methyl ester, also arrested the proliferation of 2607 cells with IC50 ~160 μM. Cell cycle analysis revealed that CySH acted to lengthen the cell cycle period of 2607 cells by slowing the passage of cells through S phase and caused the cells to finally arrest in G2/M. In the other cell lines tested, CySH arrested cells in all phases of the cell cycle. These observations suggest that CySH and its congeners may have some utility in the treatment of neoplasia in vivo.