Carly Griffin

Pancratistatin causes early activation of caspase-3 and the flipping of phosphatidyl serine followed by rapid apoptosis specifically in human lymphoma cells.

Recently a major research effort has been focused on the development of anticancer drugs by targeting the components of a biochemical pathway to induce apoptosis in cancerous cells. Some of the natural products (e.g. paclitaxel) have been proven to be useful in inducing apoptosis in cancer cells with limited specificity. Pancratistatin, a natural product isolated and characterized over a decade ago, has been shown to be cytostatic and antineoplastic. We investigated the specificity and biochemical mechanism of action of pancratistatin. Pancratistatin seemed to show more specificity than VP-16 or paclitaxel as an efficient inducer of apoptosis in human lymphoma (Jurkat) cells, with minimal effect on normal nucleated blood cells. Caspase-3 activation and exposure of phosphatidyl serine on the outer leaflet of the plasma membrane were earlier events than the generation of ROS and DNA fragmentation observed following pancratistatin treatment. This indicates a possible involvement of caspase-3 and plasma membrane proteins in the induction phase of apoptosis. Our results indicate that pancratistatin does not cause DNA double-strand breaks or DNA damage prior to the execution phase of apoptosis in cancer cells. Parallel experimentation with VP-16, a currently used medication for cancer treatment, indicated that VP-16 causes substantial DNA damage in normal non-cancerous blood cells, while pancratistatin does not cause any DNA double-strand breaks or DNA damage in non-cancerous cells. Taken together, our finding that pancratistatin induces apoptosis in cancer cells using non-genomic targets, and more importantly does not seem to have any affect non-cancerous cells, presents a significant platform to develop non-toxic anticancer therapies.

Structure-activity studies on the lycorine pharmacophore: a potent inducer of apoptosis in human leukemia cells.

Abstract The direct chemoselective differential functionalization of the ring-C hydroxyl groups present in the Amaryllidaceae alkaloid lycorine is described allowing for selective manipulation of the 1,2-hydroxyl groups. A mini-library comprised of synthetic and natural lycorane alkaloids was prepared and their apoptosis-inducing activity investigated in human leukemia (Jurkat) cells. Further insights into the nature of this interesting apoptosis-inducing pharmacophore are described, including the requirement of both free hydroxyl groups in ring-C.

Chemoenzymatic Synthesis of Amaryllidaceae Constituents and Biological Evaluation of their C-1 Analogues. The Next Generation Synthesis of 7-Deoxypancratistatin and trans-Dihydrolycoricidine†

An efficient synthesis of C-1 derivatives of 7-deoxypancratistatin is reported. The key steps include the following: selective opening of an epoxide with aluminum acetylide in the presence of an aziridine; solid-state silica-gel-catalyzed opening of an aziridine; and oxidative cleavage of a phenanthrene core and its recyclization to phenanthridone to provide the key C-1 aldehyde 22. The conversion of this aldehyde to C-1 acetoxymethyl and C-1 hydroxymethyl derivatives is described along with the evaluation of their biological activity against several cancer cell lines and in an apoptosis study. The C-1 acetoxymethyl derivative has shown promising activity comparable to that of the natural product. In addition, a total synthesis of trans-dihydrolycoricidine and a formal total synthesis of 7-deoxypancratistatin are reported from aldehyde 22. Detailed experimental and spectral data are provided for all new compounds.

Selective induction of apoptosis through activation of caspase-8 in human leukemia cells (Jurkat) by dandelion root extract.

AIM OF STUDY Dandelion extracts have been used in traditional Native American Medicine and Traditional Chinese Medicine (TCM) for treatment of leukemia and breast cancer; however, the mechanism of action remains unknown. Today, DRE is mainly marketed for management of gastrointestinal and liver disorders. The current study aims to determine the anti-cancer activity of dandelion root extract (DRE) against human leukemia, and to evaluate the specificity and mechanism of DRE-induced apoptosis. MATERIALS AND METHODS The effect of DRE on cell viability was evaluated using the colorimetric-based WST-1 assay. Apoptotic cell death was monitored by nuclear condensation and confirmed by exposure of phosphatidylserine to outer leaflet of plasma membrane. Activation of caspases was detected using a fluorogenic substrate specific to either caspase-8 or -3. Loss of mitochondrial membrane potential was observed by microscopy using JC-1 dye. The apoptotic effect of DRE was also evaluated on a dominant-negative FADD (Fas-associated death domain) cell line and non-cancerous peripheral blood mononuclear cells (PBMCs). RESULTS Aqueous DRE effectively induces apoptosis in human leukemia cell lines in a dose and time dependent manner. Very early activation of caspase-8 and the subsequent activation of caspase-3 indicate that DRE may be inducing extrinsic or receptor-mediated apoptosis. Caspase inhibition rendered this extract ineffective, thus DRE-induced apoptosis is caspase-dependent. Moreover, the dominant-negative FADD cells that are unable to form a complete DISC (death-inducing signaling complex) were resistant to DRE treatment, which further confirms our hypothesis that DRE induces receptor-mediated apoptosis. Interestingly, non-cancerous peripheral blood mononuclear cells (PBMCs) exposed to aqueous DRE under the same treatment conditions as leukemia cells were not significantly affected. CONCLUSION Our results suggest that aqueous DRE contains components that act to induce apoptosis selectively in cultured leukemia cells, emphasizing the importance of this traditional medicine and thus presents a potential novel non-toxic alternative to conventional leukemia therapy.

Pancratistatin Selectively Targets Cancer Cell Mitochondria and Reduces Growth of Human Colon Tumor Xenografts

The naturally occurring Amaryllidaceae alkaloid pancratistatin exhibits potent apoptotic activity against a large panel of cancer cells lines and has an insignificant effect on noncancerous cell lines, although with an elusive cellular target. Many current chemotherapeutics induce apoptosis via genotoxic mechanisms and thus have low selectivity. The observed selectivity of pancratistatin for cancer cells promoted us to consider the hypothesis that this alkaloid targets cancer cell mitochondria rather than DNA or its replicative machinery. In this study, we report that pancratistatin decreased mitochondrial membrane potential and induced apoptotic nuclear morphology in p53-mutant (HT-29) and wild-type p53 (HCT116) colorectal carcinoma cell lines, but not in noncancerous colon fibroblast (CCD-18Co) cells. Interestingly, pancratistatin was found to be ineffective against mtDNA-depleted (ρ0) cancer cells. Moreover, pancratistatin induced cell death in a manner independent of Bax and caspase activation, and did not alter β-tubulin polymerization rate nor cause double-stranded DNA breaks. For the first time we report the efficacy of pancratistatin in vivo against human colorectal adenocarcinoma xenografts. Intratumor administration of pancratistatin (3 mg/kg) caused significant reduction in the growth of subcutaneous HT-29 tumors in Nu/Nu mice (n = 6), with no apparent toxicity to the liver or kidneys as indicated by histopathologic analysis and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling. Altogether, this work suggests that pancratistatin may be a novel mitochondria-targeting compound that selectively induces apoptosis in cancer cells and significantly reduces tumor growth. Mol Cancer Ther; 10(1); 57–68. ©2011 AACR.

Synergy of Pancratistatin and Tamoxifen on breast cancer cells in inducing apoptosis by targeting mitochondria.

Pancratistatin (PST), a natural compound obtained from the Hawaiian spider lily, is known to be specific and selective in inducing apoptosis in multiple cancer cell lines while sparing non-cancerous cells and cell lines. Here we report the ability of PST to induce apoptosis specifically in human breast cancer cell lines MCF-7 and Hs-578-T compared to their non cancerous counterparts. In cancer cells PST caused increased levels of reactive oxygen species (ROS), decreased ATP and mitochondrial membrane permeabilization indicating the activation of the mitochondrial pathway of apoptosis. In combination with the anti-estrogen Tamoxifen, PST had a synergic effect. Both compounds caused increased production of ROS when applied to isolated mitochondria from these cancer cell lines supporting the observation that Tamoxifen might work through mechanisms distinct from the canonical estrogen receptor antagonism.

Selective cytotoxicity of Pancratistatin-related natural Amaryllidaceae alkaloids: evaluation of the activity of two new compounds

BackgroundPancratistatin (PST), a compound extracted from an Amaryllidaceae (AMD) family plant, has been shown to specifically induce apoptosis in cancer cells with no/minimal toxic effect on normal cells. A systematic synthetic approach has indicated that the minimum cytotoxic pharmacophore comprises the trans-fused b/c-ring system containing the 2, 3, 4-triol unit in the C-ring. To further explore the structure-activity relationship of this group of compounds we have investigated the anti-cancer efficacy and specificity of two PST-related natural compounds, AMD4 and AMD5. Both of these compounds lack the polyhydroxylated lycorane element of PST instead having a methoxy-substuituted crinane skeleton.ResultsOur results indicate that AMD5 has efficacy and selectivity similar to PST, albeit at a 10-fold increased concentration. Interestingly AMD4 lacks apoptotic activity.ConclusionOur results indicate that the phenanthridone skeleton in natural Amaryllidaceae alkaloids may be a significant common element for selectivity against cancer cells; furthermore, the configuration of the methoxy-side groups is responsible for higher binding affinity to the target protein/s thus making for a more efficient anti-cancer agent.

Pancratistatin induces apoptosis in clinical leukemia samples with minimal effect on non-cancerous peripheral blood mononuclear cells

BackgroundPancratistatin, a natural compound extracted from Hymenocallis littoralis, can selectively induce apoptosis in several cancer cell lines. In this ex vivo study, we evaluated the effect of pancratistatin on peripheral blood mononuclear cells obtained from 15 leukemia patients prior to clinical intervention of newly diagnosed patients, as well as others of different ages in relapse and at various disease progression states.ResultsMononuclear cells from healthy volunteers and leukemia patients were exposed to 1 μM pancratistatin for up to 48 h. Irrespective of leukemia type, pancratistatin induced apoptosis in the leukemic samples, with minimal effects on non-cancerous peripheral blood mononuclear control cells.ConclusionOur results show that pancratistatin is an effective and selective anti-cancer agent with potential for advancement to clinical trials.

Pancratistatin induces apoptosis and autophagy in metastatic prostate cancer cells

The Amaryllidaceae alkaloid pancratistatin has been proven to selectively induce apoptotic cell death in a variety of human cancer cells with an insignificant effect on non-cancerous cells. In this study we report, for the first time, the effects of pancratistatin (PST) on models of metastatic prostate cancer. The effects of pancratistatin on prostate cancer DU145 and LNCaP cell lines was assessed by microscopy, enzymatic activity assays and Western blotting. Apoptosis was determined by nuclear condensation and caspase activation, and autophagy was observed by MDC staining and LC3 expression levels. Human prostate xenografts were used to test the potential therapeutic efficacy of intra-tumor administration of pancratistatin in vivo. Pancratistatin treatment reduced cell viability and induced apoptosis in androgen-responsive (LNCaP) and androgen-refractory (DU145) prostate cancer cell lines in a dose- and time-dependent manner, but with an insignificant effect on normal human fibroblast (NHF) cells at the effective dose. Increased reactive oxygen species production and collapse of mitochondrial membrane potential resulted from treatment with pancratistatin in both cancer cell lines. This study presents the novel finding that pancratistatin treatment caused decreased migration capacity and increased autophagy levels in metastatic prostate cancer cells. Importantly, in this proof-of-concept study, pancratistatin reduced the volume of xenograft tumors compared to control-treated animals, and was well-tolerated. Our results highlight the potential of pancratistatin for clinical development as a selective therapeutic for treatment of metastatic prostate cancer.