The ability of betulinic acid to induce two different effects (cytotoxic and cytostatic) on two clones derived from the same human melanoma metastasis suggests that the development of clones resistant to this agent will be more unlikely, than that to conventional cytotoxic drugs. Moreover in spite of the lower potency compared with doxorubicin betulinic acid seems to be selective for tumor cells with minimal toxicity against normal cells. The effect of betulinic acid on melanoma cell lines is stronger than its growth-inhibitory effect on primary melanocytes. Study of combination of betulinic acid with ã-irradiation showed clearly additive effects, and indicates that they differ in their mode of action. Recently, Gauthier (2006) have synthesized a series of saponins of betulinic acid which demonstrated a strongly potent in vitro anticancer activity against human cancer cell lines.
Betulinic acid: a new chemotherapeutic agent in the treatment of neuroectodermal tumors.
University Children's Hospital, Ulm, Germany.
We identified betulinic acid (BetA) as a new cytotoxic agent active against neuroectodermal tumor cells including neuroblastoma, medulloblastoma, glioblastoma and Ewing's sarcoma cells representing the most common solid tumors of childhood. BetA induced apoptosis independent of wild-type p53 protein and accumulation of death-inducing ligand/receptor systems such as CD95. BetA had a direct effect on mitochondria resulting in the release of soluble apoptogenic factors such as cytochrome c or AIF from mitochondria into the cytosol where they induced activation of caspases. Overexpression of the anti-apoptotic proteins Bcl-2 or Bcl-XL that blocked loss of the mitochondrial membrane potential and cytochrome c release from mitochondria conferred resistance to BetA at the level of mitochondrial dysfunction, protease activation and nuclear fragmentation. Neuroblastoma cells resistant to CD95- or doxorubicin-triggered apoptosis remained sensitive to treatment with BetA suggesting that BetA may bypass some forms of resistance. Moreover, BetA exhibited potent antitumor activity on primary tumor cell cultures from all neuroblastoma (4/4), all medulloblastoma (4/4) and most glioblastoma patients (20/24) ex vivo. These findings suggest that BetA may be a promising new agent in the treatment of neuroectodermal tumors in vivo.