31 research outputs found
Impact of Mistletoe Triterpene Acids on the Uptake of Mistletoe Lectin by Cultured Tumor Cells
Complementary treatment possibilities for the therapy of cancer are increasing
in demand due to the severe side effects of the standard cytostatics used in
the first-line therapy. A common approach as a complementary treatment is the
use of aqueous extracts of Viscum album L. (Santalaceace). The therapeutic
activity of these extracts is attributed to Mistletoe lectins which are
Ribosome-inactivating proteins type II. Besides these main constituents the
extract of Viscum album L. comprises also a mixture of lipophilic ingredients
like triterpene acids of the oleanane, lupane and ursane type. However, these
constituents are not contained in commercially available aqueous extracts due
to their high lipophilicity and insolubility in aqueous extraction media. To
understand the impact of the extract ingredients in cancer therapy, the
intracellular uptake of the mistletoe lectin I (ML) by cultured tumor cells
was investigated in relation to the mistletoe triterpene acids, mainly
oleanolic acid. Firstly, these hydrophobic triterpene acids were solubilized
using cyclodextrins ("TT" extract). Afterwards, the uptake of either single
compounds (isolated ML and the aqueous "viscum" extract) or in combination
with the TT extract (ML+TT, viscumTT), was analyzed. The uptake of ML was
studied inTHP-1-, HL-60-, 143B- and Ewing TC-71-cells and determined after 30,
60 and 120 minutes by an enzyme linked immunosorbent assay which quantifies
the A-chain of the hololectin. It could be shown that the intracellular uptake
after 120 minutes amounted to 20 % in all cell lines after incubation with
viscumTT. The studies further revealed that the uptake in THP-1-, HL-60- and
Ewing TC-71-cells was independent of the addition of TT extract.
Interestingly, the uptake of ML by 143B-cells could only be measured after
addition of triterpenes pointing to resistance to mistletoe lectin
Synergistic Antitumour Properties of viscumTT in Alveolar Rhabdomyosarcoma
Aqueous mistletoe extracts from the European mistletoe (Viscum album) contain
mainly mistletoe lectins and viscotoxins as cytotoxic compounds. Lipophilic
triterpene acids, which do not occur in conventional mistletoe preparations,
were solubilised with β-cyclodextrins. The combination of an aqueous extract
(viscum) and a triterpene-containing extract (TT) recreated a whole mistletoe
extract (viscumTT). These extracts were tested on rhabdomyosarcoma in vitro,
ex vivo, and in vivo with regard to anticancer effects. Viscum and viscumTT
inhibited cell proliferation and induced apoptosis effectively in a dose-
dependent manner in vitro and ex vivo, whereas TT showed only moderate
inhibitory effects. viscumTT proved to be more effective than the single
extracts and displayed a synergistic effect in vitro and a stronger effect in
vivo. viscumTT induced apoptosis via the extrinsic and intrinsic pathways,
evidenced by the loss of mitochondrial membrane potential and activation of
CASP8 and CASP9. CASP10 inhibitor inhibited apoptosis effectively, emphasising
the importance of CASP10 in viscumTT-induced apoptosis. Additionally, viscumTT
changed the ratio of apoptosis-associated proteins by downregulation of
antiapoptotic proteins such as XIAP and BIRC5, thus shifting the balance
towards apoptosis. viscumTT effectively reduced tumour volume in patient-
derived xenografts in vivo and may be considered a promising substance for
rhabdomyosarcoma therapy
A Natural Combination Extract of Viscum album L. Containing Both Triterpene Acids and Lectins Is Highly Effective against AML In Vivo
Aqueous Viscum album L. extracts are widely used in complementary cancer
medicine. Hydrophobic triterpene acids also possess anti-cancer properties,
but due to their low solubility they do not occur in significant amounts in
aqueous extracts. Using cyclodextrins we solubilised mistletoe triterpenes
(mainly oleanolic acid) and investigated the effect of a mistletoe whole plant
extract on human acute myeloid leukaemia cells in vitro, ex vivo and in vivo.
Single Viscum album L. extracts containing only solubilised triterpene acids
(TT) or lectins (viscum) inhibited cell proliferation and induced apoptosis in
a dose-dependent manner in vitro and ex vivo. The combination of viscum and TT
extracts (viscumTT) enhanced the induction of apoptosis synergistically. The
experiments demonstrated that all three extracts are able to induce apoptosis
via caspase-8 and -9 dependent pathways with down-regulation of members of the
inhibitor of apoptosis and Bcl-2 families of proteins. Finally, the acute
myeloid leukaemia mouse model experiment confirmed the therapeutic
effectiveness of viscumTT-treatment resulting in significant tumour weight
reduction, comparable to the effect in cytarabine-treated mice. These results
suggest that the combination viscumTT may have a potential therapeutic value
for the treatment AML
ViscumTT induces apoptosis and alters IAP expression in osteosarcoma in vitro and has synergistic action when combined with different chemotherapeutic drugs
GADD45A and CDKN1A are involved in apoptosis and cell cycle modulatory effects of viscumTT with further inactivation of the STAT3 pathway
Abstract ViscumTT, a whole mistletoe preparation, has shown synergistic induction of apoptosis in several pediatric tumor entities. High therapeutic potential has previously been observed in Ewing’s sarcoma, rhabdomyosarcoma, ALL and AML. In this study, we analyzed modulatory effects on the cell cycle by viscumTT in three osteosarcoma cell lines with various TP53 statuses. ViscumTT treatment induced G1 arrest in TP53 wild-type and null-mutant cells, but S arrest in TP53 mutant cells. Blockage of G1/S transition was accompanied by down-regulation of the key regulators CDK4, CCND1, CDK2, CCNE, CCNA. However, investigations on the transcriptional level revealed secondary TP53 participation. Cell cycle arrest was predominantly mediated by transcriptionally increased expression of GADD45A and CDKN1A and decreased SKP2 levels. Enhanced CDKN1A and GADD45A expression further played a role in viscumTT-induced apoptosis with involvement of stress-induced MAPK8 and inactivation of MAPK1/3. Furthermore, viscumTT inhibited the pro-survival pathway STAT3 by dephosphorylation of the two sites, Tyr705 and Ser727, by down-regulation of total STAT3 and its direct downstream targets BIRC5 and C-MYC. Moreover, tests of the efficacy of viscumTT in vivo showing reduction of tumor volume confirmed the high therapeutic potential as an anti-tumoral agent for osteosarcoma
Multiple Active Compounds from Viscum album L. Synergistically Converge to Promote Apoptosis in Ewing Sarcoma.
Ewing sarcoma is the second most common bone cancer in children and adolescents, with poor prognosis and outcome in ~70% of initial diagnoses and 10-15% of relapses. Hydrophobic triterpene acids and hydrophilic lectins and viscotoxins from European mistletoe (Viscum album L.) demonstrate anticancer properties, but have not yet been investigated for Ewing sarcoma. Commercial Viscum album L. extracts are aqueous, excluding the insoluble triterpenes. We recreated a total mistletoe effect by combining an aqueous extract (viscum) and a triterpene extract (TT) solubilized with cyclodextrins. Ewing sarcoma cells were treated with viscum, TT and viscumTT in vitro, ex vivo and in vivo. In vitro and ex vivo treatment of Ewing sarcoma cells with viscum inhibited proliferation and induced apoptosis in a dose-dependent fashion, while viscumTT combination treatment generated a synergistic effect. Apoptosis occurred via intrinsic and extrinsic apoptotic pathways, evidenced by activation of both CASP8 and CASP9. We show that viscumTT treatment shifts the balance of apoptotic regulatory proteins towards apoptosis, mainly via CLSPN, MCL1, BIRC5 and XIAP downregulation. ViscumTT also demonstrated strong antitumor activity in a cell line- and patient-derived mouse model, and may be considered an adjuvant therapy option for pediatric patients with Ewing sarcoma