In
traditional Chinese Medicine, the preparation Danggui Longhui Wan has been used for years in the treatment of
chronic myelocytic leukemia. The compound
indirubin has been shown to be the active constituent. A cell permeable derivative,
indirubin-3'-monoxime, is a selective and potent inhibitor of
cyclin-dependent kinases (cdk). The ability of
indirubin-3'-monoxime to induce apoptosis and
tumor cell death in transitional cell
cancer cell lines was investigated here. The growth-inhibitory properties were evaluated by EZ4U, a cytotoxic assay; apoptosis induction was determined by immunoblotting of cleaved PARP and flow cytometry of
Annexin-V/PI staining during treatment. To evaluate further the underlying molecular action of
indirubin-3'-monoxime on the cell cycle, the levels of cdk-1 and
survivin, a mitotic spindle checkpoint and apoptosis-regulating
protein, respectively, were additionally determined by flow cytometry and immunoblotting. The results indicated that
indirubin-3'-monoxime induced reversible growth arrest in all four cell lines and an increase of apoptosis in two of them. The treatment with
indirubin-3'-monoxime increased the expression of
survivin almost four times in the RT4 cells and more than doubled it in the RT112 and T24 cells. In the SUP cells, the expression of
survivin increased more than seven-fold after 72-h incubation. No clear correlation between the low apoptosis induction rate and extent of
survivin expression was found. Cdk expression was not significantly altered by
indirubin-3'-monoxime. In summary,
indirubin-3'-monoxime might be a promising candidate for targeted
cancer therapy, however, its molecular action remains to be further evaluated.