- Hammerhead ribozyme against gamma-glutamylcysteine synthetase sensitizes human colonic cancer cells to cisplatin by down-regulating both the glutathione synthesis and the expression of multidrug resistance proteins. Iida, T., Kijima, H., Urata, Y., Goto, S., Ihara, Y., Oka, M., Kohno, S., Scanlon, K.J., Kondo, T. Cancer Gene Ther. (2001)