[Cell cycle arrest and apoptosis induced by tubeimoside in HeLa cell]

Tubeimoside, which is composed of tubeimoside I (79%) and II (21%), was isolated from the tubers of Bolbostemma paniculatum (Maxim) Franquet (Cucurbitaceae), a traditional Chinese medicine, "Tu-Bei-Mu". This study was designed to investigate the anti-tumor mechanism of tubeimoside.

Growth inhibition was measured by MTT assay. Induction of cell cycle arrest and apoptosis was determined by flow cytometry, fluorescence and electron microscopy, and gel electrophoresis of fragmented DNA.

Tubeimoside display strong growth inhibitory effect in a dose- and time-dependant manner against HeLa cells with estimated IC50 values of 20.0, 18.8, and 8.8 mumol/L after 24, 48, and 72 h of treatment with tubeimoside. The flow cytometry profiles revealed that treatment with tubeimoside (5 h; 15, 30, 35 mumol/L) led to a dose-dependant shift from 9.80% up to 21.90%, and 27.00% in percentage of cells with a G2/M-like DNA content. On the other hand, treatment with tubeimoside (12 h, 15, 30, 35 mumol/L) led to a time-dependant shift from 8.20% up to 21.40%, 31.15%, and 34.55%, respectively. Exposure of HeLa cells to 40 mumol/L of tubeimoside induced nuclear shrinkage, chromation condensation and margination against nuclear envelope, subdiploid peak, and DNA fragmentation, characteristic as seen in apoptotic cells.

Induction of cell cycle arrest and apoptosis may play an important role in the anti-tumor effect of tubeimoside.