Pristimerin induces caspase-dependent apoptosis in MDA-MB-231 cells via direct effects on mitochondria

Elephantopus scaber induces apoptosis through ROS-dependent mitochondrial signaling pathway in HCT116 human colorectal carcinoma cells

ETHNOPHARMACOLOGICAL RELEVANCE

Elephantopus scaber also known as Elephant's foot (Asteraceae family) has a plethora of traditional applications including dysuria, diarrhea, dysentery, leukemia and cancer. This study aimed to investigate the apoptosis inducing effects of E. scaber and the underlying mechanisms in HCT116 colorectal cell line.

METHODS

The MTT assay was used to determine the IC50 values on cancer cell lines by the ethanol, hexane, ethyl acetate and water fractions. Apoptosis was detected by cell morphologic observation through Hoechst 33342/PI dual staining, phosphatidylserine externalization by Annexin V/PI staining and DNA fragmentation by TUNEL assay. The caspase activity, Bcl-2 family and p53 proteins were determined by flow cytometric analysis. The cleaved PARP protein expression was assessed by western blot analysis

RESULTS

The ethanol extract of E. scaber and its fractions significantly inhibited the growth of HCT116 and HT-29 cells and induced apoptosis. The E. scaber ethyl acetate fraction (ESEAF) was the most potent on HCT116 cell line with the IC50 value of 1.42 ± 0.10 µg/mL. The induction of apoptosis was marked by nuclear shrinkage accompanied with chromatin condensation, DNA fragmentation and phosphatidylserine externalization. The results showed that ESEAF-induced apoptosis was associated with an upregulation of proapoptotic Bax, elevation of Bax/Bcl-2 ratio, dissipation of mitochondrial membrane potential, activation of caspase-3 and cleavage of poly (ADP-ribose) polymerase (PARP). In addition, a compromised mitochondrial membrane potential and overproduction of ROS demonstrated the involvement of the mitochondrial signaling pathway. Mechanistic studies further revealed that ESEAF caused the augmentation of the intracellular ROS, subsequently incited the increase in p53 protein expression and led to oligomerization of Bax, depolarization of mitochondrial membrane potential and caspases cascade (caspase-3/7 and -9) in a time-dependent manner. The attenuation of intracellular ROS level by N-acetyl-l-cysteine (NAC) preserved the integrity of mitochondrial membrane and rescued the cells from cell death. Furthermore, caspase cascade results in the cleavage of PARP which ultimately activated DNA fragmentation and eventually apoptosis.

CONCLUSION

Taken together, cumulative evidences in this study suggest that ESEAF induces apoptosis through ROS-dependent mitochondrial signaling pathway and holds potential therapeutic effect for colorectal cancer.

Inhibition of hTERT/telomerase contributes to the antitumor activity of pristimerin in pancreatic ductal adenocarcinoma cells

Pristimerin (PM) is a promising anticancer agent that has exhibited strong antiproliferative and apoptosis-inducing activity in various types of cancer cells. In the present study, we investigated the role of telomerase in mediating the antitumor activity of PM in pancreatic ductal adenocarcinoma (PDA) cells. PM inhibited cell proliferation, arrested cells in the G1 cell cycle phase and induced apoptosis in MiaPaCa-2 and Panc-1 PDA cells. These antitumor activities of PM correlated well with the inhibition of human telomerase reverse transcriptase (hTERT), the gene that codes for the catalytic subunit of telomerase complex. Gene knockin and knockdown approaches demonstrated that hTERT regulates the response of PDA cells to PM. PM inhibited hTERT expression by suppressing the transcription factors Sp1, c-Myc and NF-κB which control hTERT gene expression. PM also inhibited protein kinase Akt, which phosphorylates and facilitates hTERT nuclear importation and its telomerase activity. These findings identified hTERT (telomerase) as a potential therapeutic target of PM for the treatment of PDA.

Development of human serine protease-based therapeutics targeting Fn14 and identification of Fn14 as a new target overexpressed in TNBC

The cytokine TWEAK and its receptor, Fn14, have emerged as potentially valuable targets for cancer therapy. Granzyme B (GrB)-containing Fn14-targeted constructs were generated containing either the Fn14 ligand TWEAK (GrB-TWEAK) or an anti-Fn14 humanized single-chain antibody (GrB-Fc-IT4) as the targeting moieties. Both constructs showed high affinity and selective cytotoxicity against a panel of Fn14-expressing human tumor cells including triple-negative breast cancer (TNBC) lines. Cellular expression of the GrB inhibitor PI-9 in target cells had no impact on the cytotoxic effect of either construct. Cellular expression of MDR1 showed no cross-resistance to the fusion constructs. GrB-TWEAK and GrB-Fc-IT4 activated intracellular caspase cascades and cytochrome c-related proapoptotic pathways consistent with the known intracellular functions of GrB in target cells. Treatment of mice bearing established HT-29 xenografts with GrB-TWEAK showed significant tumor growth inhibition compared with vehicle alone (P < 0.05). Both GrB-TWEAK and GrB-Fc-IT4 displayed significant tumor growth inhibition when administered to mice bearing orthotopic MDA-MB-231 (TNBC) tumor xenografts. The Cancer Genome Atlas analysis revealed that Fn14 mRNA expression was significantly higher in TNBC and in HER2-positive disease (P < 0.0001) compared with hormone receptor-positive breast cancer, and in basal-like 2 tumors (P = 0.01) compared with other TNBC molecular subtypes. IHC analysis of a 101 patient TNBC tumor microarray showed that 55 of 101 (54%) of tumors stained positive for Fn14, suggesting that this may be an excellent potential target for precision therapeutic approaches. Targeting Fn14 using fully human, GrB-containing fusion constructs may form the basis for a new class of novel, potent, and highly effective constructs for targeted therapeutic applications.

Ubiquitin-proteasomal degradation of antiapoptotic survivin facilitates induction of apoptosis in prostate cancer cells by pristimerin

Pristimerin (PM), a quinonemethide triterpenoid, is a promising anticancer agent with potent antiproliferative and apoptosis-inducing activities against cancer cell lines. However, the anticancer activity and mechanisms of PM in prostate cancer cells have not been adequately investigated. Here we report that the degradation of survivin plays an important role in the antiproliferative and proapoptotic effects of PM in carcinoma of the prostate (CaP) cell lines. Treatment with PM inhibited proliferation and induced apoptosis in LNCaP and PC-3 cells as characterized by the loss of cell viability and an increase in Annexin V-binding and cleavage of PARP-1, respectively. The antiproliferative and apoptosis-inducing effects of PM were associated with the inhibition of cell cycle regulatory proteins, antiapoptotic survivin and members of the Bcl-2 family. Data showed that response to PM is regulated by survivin since overexpression of survivin rendered CaP cells resistant to PM. Furthermore, downregulation of survivin by PM was mediated through the ubiquitin-proteasomal degradation. Together, these data demonstrate that pristimerin inhibits proliferation and induces apoptosis in CaP cells by abolishing survivin through the ubiquitin-proteasome pathway.

Pristimerin, a natural anti-tumor triterpenoid, inhibits LPS-induced TNF-α and IL-8 production through down-regulation of ROS-related classical NF-κB pathway in THP-1 cells

Pristimerin, a naturally occurring quinonemethide triterpenoid compound, is known to exert a variety of pharmacological activities. In the present study, we investigated the molecular actions of pristimerin against LPS-induced inflammatory responses in human monocytic THP-1 cells. The results showed that pristimerin inhibited the production of TNF-α and IL-8 in a dose-dependent manner. To explore the possible mechanisms underlying these inhibitions by pristimerin, we examined the intracellular ROS level and the NF-κB protein signaling pathway. Pristimerin clearly scavenged LPS-induced intracellular ROS production. In addition, pristimerin prevented LPS-induced NF-κB activation through the inhibition of phosphorylation of IKKα/β, phosphorylation and degradation of IκBα, as well as phosphorylation and nuclear translocation of NF-κB p65. These findings suggest that pristimerin down-regulates the expression of pro-inflammatory mediators through blocking of NF-κB activation by inhibiting interconnected ROS/IKK/NF-κB signaling pathways.

Pristimerin, a quinonemethide triterpenoid, induces apoptosis in pancreatic cancer cells through the inhibition of pro-survival Akt/NF-κB/mTOR signaling proteins and anti-apoptotic Bcl-2

Lack of effective therapeutics for pancreatic cancer at the present time underscores the dire need for safe and effective agents for the treatment of this malignancy. In the present study, we have evaluated the anticancer activity and the mechanism of action of pristimerin (PM), a quinonemethide triterpenoid, against MiaPaCa-2 and Panc-1 pancreatic ductal adenocarcinoma (PDA) cell lines. Treatment with PM inhibited the proliferation and induced apoptosis in both cell lines as characterized by the increased Annexin V-binding and cleavage of PARP-1 and procaspases -3, -8 and -9. PM also induced mitochondrial depolarization and the release of cytochrome c from the mitochondria. The induction of apoptosis by PM was associated with the inhibition of the pro-survival Akt, NF-κB and mTOR signaling proteins and their downstream intermediaries such as Foxo-3α and cyclin D1 (Akt); Cox-2 and VEGF (NF-κB); p-S6K1 and p-4E-BP1 (mTOR) as well as PKCɛ. Treatment with PM also inhibited the expression of anti-apoptotic Bcl-2 and survivin but not Bcl-xL. The downregulation of Bcl-2 by PM was not due to proteasomal or lysosomal proteolytic degradation of Bcl-2, since treatment with PM in the presence of proteasomal inhibitors MG132 or lactacystin (LAC) or calpain inhibitor MG101 failed to block the downregulation of Bcl-2 by PM. On the other hand, RT-PCR analysis showed the inhibition of Bcl-2 mRNA by PM in a dose-related manner, indicating that inhibition of Bcl-2 by PM is mediated through the suppression of Bcl-2 gene expression. Thus, the mechanistic understanding of the antitumor activity of pristimerin could facilitate in vivo efficacy studies of pristimerin for pancreatic cancer.

Multifunctional pentacyclic triterpenoids as adjuvants in cancer chemotherapy: a review

The protective adjuvants in chemotherapy.

Anticancer activity of pristimerin in epidermal growth factor receptor 2-positive SKBR3 human breast cancer cells

Pristimerin is a naturally occurring triterpenoid that causes cytotoxicity in several cancer cell lines. However, the mechanism of action for the cytotoxic effect of pristimerin has not been unexplored. The purpose of this study was to investigate the effect of pristimerin on cytotoxicity using the epidermal growth factor receptor 2 (HER2)-positive SKBR3 human breast cancer cell line. Pristimerin inhibited proliferation in dose- and time-dependent manners in cells. We found it to be effective for suppressing HER2 protein and mRNA expression. Fatty acid synthase (FASN) expression and FASN activity were downregulated by pristimerin. Adding of exogenous palmitate, the end product of de novo fatty acid synthesis, reduced the proliferation activity of pristimerin. The changes in HER2 and FASN expression induced by pristimerin altered the levels of Akt and mitogen-activated protein kinase (MAPK) phosphorylation (Erk1/2, p38, and c-Jun N-terminal kinase (JNK)). Pristimerin lowered the levels of phosphorylated mammalian target of rapamycin (mTOR) and its downstream targets such as phosphoprotein 70 ribosomal protein S6 kinase and 4E binding protein1. Pristimerin inhibited migration and invasion of cells, and co-treatment with the mTOR inhibitor rapamycin additionally suppressed these activities. Pristimerin-induced apoptosis was evaluated using Western blotting for caspase-3, -8, -9, and poly (ADP-ribose) polymerase expression and flow cytometric analysis for propidium iodide labeling. These results suggest that pristimerin is a novel HER2-downregulated compound that is able to decrease fatty acid synthase and modulate the Akt, MAPK, and mTOR signaling pathways to influence metastasis and apoptosis. Pristimerin may be further evaluated as a chemotherapeutic agent for HER2-positive breast cancers.

Chemopreventive effects of Ginkgo biloba extract in estrogen-negative human breast cancer cells

Excessive level of estrogen is considered as a main cause of breast cancer, therefore, many studies have focused on estrogen receptor (ER)-positive breast cancer, even though ER-negative cancer has a poor prognosis than ER-positive breast cancer. We evaluated the anti-cancer effects of Ginkgo biloba extract (GBE) in estrogen-independent breast cancer. GBE has been traditionally used as a platelet activating factor, a circulatory stimulant, a tonic, and anti-asthmatic drug, and anti-cancer agent. However, anti-cancer effects of GBE on ER-negative breast cancer have not been proved yet. In this study, we tested chemotherapeutic potential of GBE in the MDA-MB-231 (ER-negative) human breast cancer cell line. Our results showed that cytotoxicity effects of GBE in MDA-MB-231 lead to DNA fragmentation at high concentrations (500 and 1,000 μg/ml). Caspase-3 was significantly activated and mRNA levels of apoptosis-related genes (Bcl-2 and Bax) were altered. These results indicate that GBE induces apoptosis in MDA-MB-231 cells. It is presumed that GBE has chemopreventive effects in ER-independent breast cancer through anti-proliferation and apoptosis-inducing activities.

Anti-inflammatory effect of pristimerin on lipopolysaccharide-induced inflammatory responses in murine macrophages

Pristimerin, a quinonemethide triterpenoid derived from Celastraceae and Hippocrateaceae, has recently been found to suppress tumor promotion, metastasis and angiogenesis. In the present study, we evaluated the anti-inflammatory potentials of pristimerin in a cell culture system. Pristimerin suppressed not only the generation of nitric oxide (NO) and prostaglandin E2, but also the expression of inducible NO synthase and cyclooxygenase-2 induced by lipopolysacharide (LPS) in murine macrophage RAW264.7 cells. Similarly, pristimerin inhibited the release of pro-inflammatory cytokines, namely, tumor necrosis factor-α and interleukin-6, induced by LPS. The underlying mechanism of the anti-inflammatory action of pristimerin was correlated with down-regulation of nuclear factor-κB and the mitogen-activated protein kinase signal pathway.

Pristimerin inhibits breast cancer cell migration by up- regulating regulator of G protein signaling 4 expression

BACKGROUND/AIM

Pristimerin isolated from Celastrus and Maytenus spp can inhibit proteasome activity. However, whether pristimerin can modulate cancer metastasis is unknown.

METHODS

The impacts of pristimerin on the purified and intracellular chymotrypsin proteasomal activity, the levels of regulator of G protein signaling 4 (RGS 4) expression and breast cancer cell lamellipodia formation, and the migration and invasion were determined by enzymatic, Western blot, immunofluorescent, and transwell assays, respectively.

RESULTS

We found that pristimerin inhibited human chymotrypsin proteasomal activity in MDA-MB-231 cells in a dose-dependent manner. Pristimerin also inhibited breast cancer cell lamellipodia formation, migration, and invasion in vitro by up-regulating RGS4 expression. Thus, knockdown of RGS4 attenuated pristimerin-mediated inhibition of breast cancer cell migration and invasion. Furthermore, pristimerin inhibited growth and invasion of implanted breast tumors in mice.

CONCLUSION

Pristmerin inhibits proteasomal activity and increases the levels of RGS4, inhibiting the migration and invasion of breast cancer cells.

Pristimerin Induces Apoptosis in Prostate Cancer Cells by Down-regulating Bcl-2 through ROS-dependent Ubiquitin-proteasomal Degradation Pathway

Pristimerin is a quinonemethide triterpenoid with the potential of a promising anticancer agent. Pristimerin (PM) has shown anticancer activity against a range of cancer cell lines, but its activity for prostate cancer has not been adequately investigated. In the present study we have examined the underlying mechanisms of the apoptotic response of the hormone-sensitive (LNCaP) and hormone-refractory (PC-3) prostate cancer cell lines to PM. Treatment with PM induced apoptosis in both cell lines as characterized by increased annexin V-binding and cleavage of PARP-1 and procaspases-3 and -9. It also induced mitochondrial depolarization, cytochrome c release from mitochondria and generation of reactive oxygen species (ROS). Response to PM is regulated by Bcl-2 since it down-regulated Bcl-2 expression and overexpression of Bcl-2 rendered prostate cancer cells resistant to PM. ROS plays a role in down-regulation of Bcl-2, since treatment with PM in the presence of various ROS modulators, e.g., n-acetylcysteine (NAC), a general purpose antioxidant; diphenylene iodonium (DPI), a NADPH inhibitor; rotenone (ROT), a mitochondrial electron transport chain interrupter rotenone or MnTBAP, a O₂ scavenger, attenuated the down-regulation of Bcl-2. Furthermore, ROS is also involved in the ubiquitination and proteasomal degradation of Bcl-2 as both of these events were blocked by O ₂^- scavenger MnTBAP. Thus, pristimerin induces apoptosis in prostate cancer cells predominately through the mitochondrial apoptotic pathway by inhibiting antiapoptic Bcl-2 through a ROS-dependent ubiquitin-proteasomal degradation pathway.

The triterpenoid pristimerin induces U87 glioma cell apoptosis through reactive oxygen species-mediated mitochondrial dysfunction

It has become evident that some of the natural or synthetic triterpenoids are natural proteasome inhibitors that have great potential for use in cancer prevention and treatment. However, the mechanisms for the antitumor activity of triterpenoids remain to be elucidated. In the present study, we investigated the anticancer activities of a natural triterpenoid, pristimerin, and the signaling pathways affected. Pristimerin was found to possess potent cytotoxic effects, inducing apoptosis and inhibiting proliferation in U87 human glioma cells. Hoechst 33258 staining and Annexin V/PI double staining exhibited the typical nuclear features of apoptosis and increased the proportion of apoptotic Annexin V-positive cells in a dose-dependent manner, respectively. Moreover, western blotting assay revealed that this apoptotic induction was associated with activated caspase-9, caspase-3, PARP cleavage and downregulation of Bcl-xl/Bax in a concentration-dependent manner. Pristimerin also increased the generation of reactive oxygen species and induced the subsequent release of cytochrome c from the mitochondria into the cytosol. Additionally, pristimerin downregulated EGFR protein expression and inhibited downstream signaling pathways in U87 cells. Our results suggest that pristimerin may have potential as a new targeting therapeutic strategy in the treatment of EGFR-overexpressing gliomas.

Pristimerin causes G1 arrest, induces apoptosis, and enhances the chemosensitivity to gemcitabine in pancreatic cancer cells

Despite rapid advances in chemotherapy and surgical resection strategies, pancreatic cancer remains the fourth leading cause of cancer related deaths in the United States with a 5-year survival rate of less than 5%. Therefore, novel therapeutic agents for the prevention and treatment of pancreatic cancer are urgently needed. The aim of this study was to investigate the effect of pristimerin, a quinonemethide triterpenoid compound isolated from Celastraceae and Hippocrateaceae, on inhibition of cell proliferation and induction of apoptosis in three pancreatic cancer cells, BxPC-3, PANC-1 and AsPC-1, in both monotherapy and in combination with gemcitabine. Treatment with pristimerin decreased the cell proliferation of all three pancreatic cancer cells in a dose- and time-dependent manner. Treatment of pancreatic cancer cells with pristimerin also resulted in G1-phase arrest which was strongly associated with a marked decrease in the level of cyclins (D1 and E) and cyclin-dependent kinases (cdk2, cdk4 and cdk6 ) with concomitant induction of WAF1/p21 and KIP1/p27. Pristimerin treatment also resulted in apoptotic cell death, cleavage of caspase-3, modulation in the expressions of Bcl-2 family proteins, inhibition of the translocation and DNA-binding activity of NF-κB. In addition, pristimerin potentiated the growth inhibition and apoptosis inducing effects of gemcitabine in all three pancreatic cancer cells, at least in part, by inhibiting constitutive as well as gemcitabine-induced activation of NF-κB in both its DNA-binding activity and transcriptional activity. Taken together, these data provide the first evidence that pristimerin has strong potential for development as a novel agent against pancreatic cancer.

Pristimerin, a triterpenoid, inhibits tumor angiogenesis by targeting VEGFR2 activation

Pristimerin is a triterpenoid isolated from Celastrus and Maytenus spp. thathas been shown to possess a variety of biological activities, including anti-cancer activity. However, little is known about pristimerin’s effects on tumor angiogenesis. In this study, we examined the function and the mechanism of this compound in tumor angiogenesisusing multiple angiogenesis assays. We found that pristimerin significantly reduced both the volume and weight of solid tumors and decreased angiogenesis in a xenograft mouse tumor model in vivo. Pristimerin significantly inhibited the neovascularization of chicken chorioallantoic membrane (CAM) in vivo and abrogated vascular endothelial growth factor (VEGF)-induced microvessel sprouting in an ex vivo rat aortic ring assay. Furthermore, pristimerin inhibited the VEGF-induced proliferation, migration and capillary-like structure formation of human umbilical vascular endothelial cells (HUVECs) in a concentration-dependent manner. Mechanistic studies revealed that pristimerin suppressed the VEGF-induced phosphorylation of VEGF receptor 2 kinase (KDR/Flk-1) and the activity of AKT, ERK1/2, mTOR, and ribosomal protein S6 kinase. Taken together, our results provide evidence for the first time that pristimerin potently suppresses angiogenesis by targeting VEGFR2 activation. These results provide a novel mechanism of action for pristimerin which may be important in the treatment of cancer.

Using the pER8:GUS reporter system to screen for phytoestrogens from Caesalpinia sappan

Arabidopsis thaliana pER8:GUS, a low-cost, highly efficient, and convenient transgenic plant system, was used to assay the estrogen-like activity of 30 traditional Chinese medicines. The MeOH extract of Caesalpinia sappan exhibited significant bioactivity in this assay, and subsequent bioactivity-guided fractionation of the extract led to the isolation of one new compound, (S)-3,7-dihydroxychroman-4-one (1), and 10 known compounds. Both the plant pER8:GUS and in vitro estrogen response element reporter assays were used to evaluate the estrogenic activity of the isolated compounds, and these two systems produced comparable results. Compounds 6, 8, and 11 showed significant estrogenic activity comparable to genistein. These active compounds were determined to be nontoxic new sources of phytoestrogens. In addition, compounds 2 and 3 inhibited ERE transcription induced by 17β-estradiol. A docking model revealed that compounds 6, 8, and 11 showed high affinity to the estrogen receptor. The pER8:GUS reporter system was demonstrated to be a useful and effective technique in phytoestrogen discovery.

Effect of thymol on peripheral blood mononuclear cell PBMC and acute promyelotic cancer cell line HL-60

Thymol, a naturally occurring phenolic compound, has been known for its antioxidant, anti microbial, and anti inflammatory activity. Thymol has also been reported as anti-cancer agent, but its anti-cancer mechanism has not yet been fully elucidated. Thus, we aimed to investigate anticancer activity of thymol on HL-60 (acute promyelotic leukemia) cells. In our study, thymol demonstrated dose dependent cytotoxic effects on HL-60 cells after 24h of exposure. However, thymol did not show any cytotoxic effect in normal human PBMC. The cytotoxic effect of thymol on HL-60 cells appears to be associated with induction of cell cycle arrest at sub G0/G1 phase, and apoptotic cell death based on genomic DNA fragmentation pattern. Thymol also showed significant increase in production of reactive oxygen species (ROS) activity, increase in mitochondrial H(2)O(2) production and depolarization of mitochondrial membrane potential. On performing Western Blot analysis, thymol showed increase in Bax protein level with a concomitant decrease in Bcl2 protein expression in a dose dependent manner. Our study also showed activation of caspase -9, -8 and -3 and concomitant PARP cleavage, which is the hallmark of caspase-dependent apoptosis. Moreover, to rule out the involvement of other mechanisms in apoptosis induction by thymol, we also studied its effect on apoptosis inducing factor (AIF). Thymol induced AIF translocation from mitochondria to cytosol and to nucleus, thus indicating its ability to induce caspase independent apoptosis. We conclude that, thymol-induced apoptosis in HL-60 cells involves both caspase dependent and caspase independent pathways.

Bluetongue virus infection: activation of the MAP kinase-dependent pathway is required for apoptosis

Bluetongue virus (BTV) is a double-stranded RNA virus that induces apoptosis both in mammalian cell cultures and in target tissues. Based on information that members of the mitogen-activated protein kinase family (MAPKs) are mediators of apoptosis, we have examined in detail the MAPK-dependent apoptosis in BTV infection. Previously, we have shown that apoptosis in BTV infection requires the participation of mitochondrial apoptotic pathways. In addition, we demonstrated that NF-κB is activated and that its inhibition substantially reduces cellular apoptosis. For the first time, here we demonstrated the activation of MAPKs after BTV infection. Moreover, by pre-treatment with MAPK inhibitors, c-Jun N-terminal kinases (JNKs) and p38 MAPK, but not extracellular signal-related kinase (ERK), significantly decreased the induction of apoptosis. JNK and p38 activation regulated the cytochrome c released from mitochondria and caspase 3 activation. These results strengthen the understanding of BTV infection and contribute to our previous data confirming that BTV infection induces robust apoptosis in mammalian cells and is likely to play a primary role in BTV pathophysiology.

Triterpenoids as potential agents for the chemoprevention and therapy of breast cancer

Breast cancer remains a major cause of death in the United States as well as the rest of the world. In view of the limited treatment options for patients with advanced breast cancer, preventive and novel therapeutic approaches play an important role in combating this disease. The plant-derived triterpenoids, commonly used for medicinal purposes in many Asian countries, posses various pharmacological properties. A large number of triterpenoids are known to exhibit cytotoxicity against a variety of tumor cells as well as anticancer efficacy in preclinical animal models. Numerous triterpenoids have been synthesized by structural modification of natural compounds. Some of these analogs are considered to be the most potent antiinflammatory and anticarcinogenic triterpenoids known. This review examines the potential role of natural triterpenoids and their derivatives in the chemoprevention and treatment of mammary tumors. Both in vitro and in vivo effects of these agents and related molecular mechanisms are presented. Potential challenges and future directions involved in the advancement of these promising compounds in the prevention and therapy of human breast cancer are also identified.

Targeting inflammatory pathways by triterpenoids for prevention and treatment of cancer

Traditional medicine and diet has served mankind through the ages for prevention and treatment of most chronic diseases. Mounting evidence suggests that chronic inflammation mediates most chronic diseases, including cancer. More than other transcription factors, nuclear factor-kappaB (NF-κB) and STAT3 have emerged as major regulators of inflammation, cellular transformation, and tumor cell survival, proliferation, invasion, angiogenesis, and metastasis. Thus, agents that can inhibit NF-κB and STAT3 activation pathways have the potential to both prevent and treat cancer. In this review, we examine the potential of one group of compounds called triterpenes, derived from traditional medicine and diet for their ability to suppress inflammatory pathways linked to tumorigenesis. These triterpenes include avicins, betulinic acid, boswellic acid, celastrol, diosgenin, madecassic acid, maslinic acid, momordin, saikosaponins, platycodon, pristimerin, ursolic acid, and withanolide. This review thus supports the famous adage of Hippocrates, “Let food be thy medicine and medicine be thy food”.

3β-hydroxylup-20(29)-ene-27,28-dioic acid dimethyl ester, a novel natural product from Plumbago zeylanica inhibits the proliferation and migration of MDA-MB-231 cells

Plumbago zeylanica, a traditional Indian herb is being used for the therapy of rheumatism and has been approved for anti-tumor activity. However, the molecular mechanisms involved in the biological action are not very well understood. In this study, the anti-invasive activities of P. zeylanica methanolic extract (PME) and pure compound 3β-hydroxylup-20(29)-ene-27,28-dioic acid (PZP) isolated from it are investigated in vitro. PME and PZP were noted to have the ability to induce apoptosis as assessed by flow cytometry. Further, the molecular mechanism of apoptosis induced by PME and PZP was found by the loss of mitochondrial membrane potential with the down regulation of Bcl-2, increased expression of Bad, release of cytochrome c, activation of caspase-3 and cleavage of PARP leading to DNA fragmentation. Importantly, both PME and PZP were observed to suppress MDA-MB-231 cells adhesion to the fibronectin-coated substrate and also inhibited the wound healing migration and invasion of MDA-MB-231 cells through the reconstituted extracellular matrix. Gelatin zymography revealed that PME and PZP decreased the secretion of matrix metalloproteinases-2 (MMP-2) and metalloproteinases-9 (MMP-9). Interestingly both PME and PZP exerted an inhibitory effect on the protein levels of p-PI3K, p-Akt, p-JNK, p-ERK1/2, MMP-2, MMP-9, VEGF and HIF-1α that are consistent with the observed anti-metastatic effect. Collectively, these data provide the molecular basis of the anti-proliferative and anti-metastatic effects of PME and PZP.

Pristimerin induces apoptosis in imatinib-resistant chronic myelogenous leukemia cells harboring T315I mutation by blocking NF-kappaB signaling and depleting Bcr-Abl

Background

Chronic myelogenous leukemia (CML) is characterized by the chimeric tyrosine kinase Bcr-Abl. Bcr-Abl-T315I is the notorious point mutation that causes resistance to imatinib and the second generation tyrosine kinase inhibitors, leading to poor prognosis. CML blasts have constitutive p65 (RelA NF-κB) transcriptional activity, and NF-κB may be a potential target for molecular therapies in CML that may also be effective against CML cells with Bcr-Abl-T315I.

Results

In this report, we discovered that pristimerin, a quinonemethide triterpenoid isolated from Celastraceae and Hippocrateaceae, inhibited growth and induced apoptosis in CML cells, including the cells harboring Bcr-Abl-T315I mutation. Additionally, pristimerin inhibited the growth of imatinib-resistant Bcr-Abl-T315I xenografts in nude mice. Pristimerin blocked the TNFα-induced IκBα phosphorylation, translocation of p65, and expression of NF-κB-regulated genes. Pristimerin inhibited two steps in NF-κB signaling: TAK1→IKK and IKK→IκBα. Pristimerin potently inhibited two pairs of CML cell lines (KBM5 versus KBM5-T315I, 32D-Bcr-Abl versus 32D-Bcr-Abl-T315I) and primary cells from a CML patient with acquired resistance to imatinib. The mRNA and protein levels of Bcr-Abl in imatinib-sensitive (KBM5) or imatinib-resistant (KBM5-T315I) CML cells were reduced after pristimerin treatment. Further, inactivation of Bcr-Abl by imatinib pretreatment did not abrogate the TNFα-induced NF-κB activation while silencing p65 by siRNA did not affect the levels of Bcr-Abl, both results together indicating that NF-κB inactivation and Bcr-Abl inhibition may be parallel independent pathways.

Conclusion

To our knowledge, this is the first report to show that pristimerin is effective in vitro and in vivo against CML cells, including those with the T315I mutation. The mechanisms may involve inhibition of NF-κB and Bcr-Abl. We concluded that pristimerin could be a lead compound for further drug development to overcome imatinib resistance in CML patients.

Synthesis and anti breast cancer activity of biphenyl based chalcones

A series of (2E,2'E)-1,1'-(3-hydroxy-5-methylbiphenyl-2,6-diyl)-bis(3-pheylprop-2-ene-1-ones (5-33) were prepared by the reaction of 1,3-diacetyl biphenyls (1-4) with different aldehydes in presence of catalytic amount of solid KOH in ethanol in excellent yields. The compounds were evaluated for anticancer activity against human breast cancer MCF-7 (estrogen responsive proliferative breast cancer model) and MDA-MB-231 (estrogen independent aggressive breast cancer model) cell lines, HeLa (cervical cancer) cell line, and human embryonic kidney (HEK-293) cells. Most of the compounds preferentially inhibited the growth of the aggressive human breast cancer cell lines, MDA-MB-231 in the range of 4.4-30 μM. The two compounds 9 and 29 proved to be better anticancer agents than the standard drug tamoxifen against the MDA-MB-231 cell lines. Mode of action of these compounds was established to be apoptosis, cell cycle arrest and loss of mitochondrial membrane potential.

Cordyceps pruinosa extracts induce apoptosis of HeLa cells by a caspase dependent pathway

AIM OF THE STUDY

Cordyceps is a parasitic fungus and has long been used as a traditional Chinese medicine to treat illnesses, promote longevity, increase athletic power, and relieve exhaustion and cancer. In this study, we reveal the mechanisms underlying apoptosis induced by Cordyceps pruinosa butanol fraction (CPBF) in the human cervical adenocarcinoma cell line, HeLa.

MATERIALS AND METHODS

Proliferation and apoptosis of cells were examined by MTT assay, DNA fragmentation, phosphatidyl serine distribution assay, Western blot analysis, and immunocytochemistry. To determine the association between CPBF related apoptosis and ROS, electron spin resonance (ESR) trapping experiments were used.

RESULTS

CPBF inhibited proliferation and induced apoptosis in HeLa cells in a dose-dependent manner using a MTT assay, DNA fragmentation, and a phosphatidyl serine distribution assay. Western blot analysis showed that apoptosis in HeLa cells was caspase-3- and -9-dependent. Proteolytic cleavage of PARP and the release of cytochrome c from the mitochondria into the cytosol were significantly increased and the Bcl-2/Bax protein ratio was decreased. Apoptosis induced by CPBF was not prevented by various antioxidants.

CONCLUSIONS

These results indicate that apoptotic effects of CPBF on HeLa cells are mediated by mitochondria-dependent death-signaling pathway independent of reactive oxygen species, suggesting that CPBF might be effective as an anti-proliferative agent for cancer.

Targeting tumor proteasome with traditional Chinese medicine

The proteasome is a multicatalytic protease complex whose activity is required for the growth of normal or tumor cells. It has been shown that human cancer cells are more sensitive to proteasome inhibition than normal cells, indicating that the proteasome could be a target of chemotherapy. Studies suggest that traditional Chinese medicine (TCM) is an effective approach for cancer treatment. Here we reviewed several TCMs for their potential in treatment of cancer. This short review focuses mainly on the TCMs that potentially target the tumor cellular proteasome and NF-kappaB pathway whose activation is dependent on the proteasome activity.

ABL-N-induced apoptosis in human breast cancer cells is partially mediated by c-Jun NH2-terminal kinase activation

Introduction

The present study was designed to determine the possibility of acetylbritannilactone (ABL) derivative 5-(5-(ethylperoxy)pentan-2-yl)-6-methyl-3-methylene-2-oxo-2,3,3a,4,7,7a-hexahydrobenzofuran-4-yl 2-(6-methoxynaphthalen-2-yl)propanoate (ABL-N) as a novel therapeutic agent in human breast cancers.

Methods

We investigated the effects of ABL-N on the induction of apoptosis in human breast cancer cells and further examined the underlying mechanisms. Moreover, tumor growth inhibition of ABL-N was done in xenograft models.

Results

ABL-N induced the activation of caspase-3 in estrogen receptor (ER)-negative cell lines MDA-MB-231 and MDA-MB-468, as evidenced by the cleavage of endogenous substrate Poly (ADP-ribose) polymerase (PARP). Pretreatment of cells with pan-caspase inhibitor z-VAD-fmk or caspase-3-specific inhibitor z-DEVD-fmk inhibited ABL-N-induced apoptosis. ABL-N treatment also resulted in an increase in the expression of pro-apoptotic members (Bax and Bad) with a concomitant decrease in Bcl-2. Furthermore, c-Jun-NH₂-terminal kinase (JNK) and p38 mitogen-activated protein (MAP) kinase (p38) were activated in the apoptosis induced by ABL-N and JNK-specific inhibitor SP600125 and JNK small interfering RNA (siRNA) antagonized ABL-N-mediated apoptosis. However, the p38-specific inhibitor SB203580 had no effect upon these processes. Moreover, neither of the caspase inhibitors prevented ABL-N-induced JNK activation, indicating that JNK is upstream of caspases in ABL-N-initiated apoptosis. Additionally, in a nude mice xenograft experiment, ABL-N significantly inhibited the tumor growth of MDA-MB-231 cells.

Conclusions

ABL-N induces apoptosis in breast cancer cells through the activation of caspases and JNK signaling pathways. Moreover, ABL-N treatment causes a significant inhibition of tumor growth in vivo. Therefore, it is thought that ABL-N might be a potential drug for use in breast cancer prevention and intervention.

Reactive oxygen species-dependent activation of Bax and poly(ADP-ribose) polymerase-1 is required for mitochondrial cell death induced by triterpenoid pristimerin in human cervical cancer cells

Naturally occurring triterpenoid compounds have long been used as anti-inflammatory, antimalarial, and insecticidal agents. It has become evident that some of the natural or synthetic triterpenoids have promising clinical potential as both a therapeutic and chemopreventive agent for cancer. However, the molecular basis for the antitumor activity of triterpenoid has yet to be defined. In this study, we show that pristimerin, a natural triterpenoid, induces mitochondrial cell death in human cervical cancer cells and that reactive oxygen species (ROS)-dependent activation of both Bax and poly(ADP-ribose) polymerase-1 (PARP-1) is critically required for the mitochondrial dysfunction. We also showed that c-Jun N-terminal kinase (JNK) is involved in ROS-dependent Bax activation. Treatment of pristimerin induced an increase in intracellular ROS, JNK activation, conformational change, and mitochondrial redistribution of Bax, mitochondrial membrane potential loss, and cell death. The PARP-1 was also found to be activated by pristimerin treatment. An antioxidant, N-acetyl-l-cysteine (NAC), inhibited pristimerin-induced JNK activation, Bax relocalization, and PARP-1 activation, as well as mitochondrial cell death. Moreover, inhibition of JNK clearly suppressed conformational change and mitochondrial translocation of Bax and subsequent mitochondrial cell death but did not affect PARP-1 activation. Inhibition of PARP-1 with 1,5-dihydroxyisoquinoline (DIQ) or with small interfering RNA of PARP-1 significantly attenuated pristimerin-induced mitochondrial membrane potential loss and cell death but did not affect JNK activation and Bax relocalization. These results indicate that the natural triterpenoid pristimerin induces mitochondrial cell death through ROS-dependent activation of both Bax and PARP-1 in human cervical cancer cells and that JNK is involved in ROS-dependent Bax activation.

Influenza A (H(1)N(1)) Antiviral and Cytotoxic Agents from Ferula assa-foetida

Two new sesquiterpene coumarins, designated 5'-acetoxy-8'-hydroxyumbelliprenin (1) and 10'R-acetoxy-11'-hydroxyumbelliprenin (2), and a new diterpene, 15-hydroxy-6-en-dehydroabietic acid (3), along with 27 known compounds, were isolated from a CHCl(3)-soluble extract of Ferula assa-foetida through bioassay-guided fractionation. The structures of the new metabolites 1-3 were identified by spectroscopic data interpretation and by the Mosher ester method. Compounds 4 and 6-13 showed greater potency against influenza A virus (H(1)N(1)) (IC(50) 0.26-0.86 microg/mL) than amantadine (IC(50) 0.92 microg/mL), and 11 exhibited the best potency (IC(50) 0.51, 2.6, and 3.4 microg/mL) of these compounds against the HepG2, Hep3B, and MCF-7 cancer cell lines, respectively.

Methyl jasmonate decreases membrane fluidity and induces apoptosis through tumor necrosis factor receptor 1 in breast cancer cells

In recent years, studies with plant compounds have shown both chemotherapeutic and chemopreventive properties. This study with plant stress hormones (jasmonates) showed growth inhibitory effects in breast cancer cells. cis-Jasmone and methyl jasmonate (MJ) inhibited the long-term proliferation of MDA-MB-435 and MCF-7 cells. Cell cycle analysis showed G0/G1 and S-phase arrest with increasing apoptotic population. Cellular signaling studies with MJ showed decreased membrane fluidity and activation of extrinsic and intrinsic apoptotic pathways. Specifically in extrinsic apoptotic pathway increased expression of TNF receptor 1, activation of mitogen-activated protein kinase and caspase-8 was observed. MJ also decreased the mitochondrial membrane potential and activated caspase-3 in breast cancer cells. In conclusion our results revealed novel-signaling mechanism of MJ in breast cancer cells, indicating that MJ could have potential applications for chemotherapeutic purposes.

Bioactive cembrane diterpenoids of Anisomeles indica

Five new cembrane-type diterpenoids with a trans-fused alpha-methylene-gamma-lactone (1-5), a new flavonoid glucoside (6), and 17 known compounds were isolated from a methanol extract of Anisomeles indica. The structures of 1-6 were elucidated by spectroscopic analysis, and the absolute configuration of compound 1 was determined using the modified Mosher's method. Compound 8 (4,5-epoxovatodiolide) exhibited cytotoxicity against a small panel of human cancer cell lines. Additionally, compounds 4 and 7 (ovatodiolide) exhibited selective antiplatelet aggregation activities toward collagen, while compounds 4, 5, and 8 showed inhibitory effects on antiplatelet aggregation induced by thrombin.

Natural compounds with proteasome inhibitory activity for cancer prevention and treatment

The proteasome is a multicatalytic protease complex that degrades most endogenous proteins including misfolded or damaged proteins to ensure normal cellular function. The ubiquitin-proteasome degradation pathway plays an essential role in multiple cellular processes, including cell cycle progression, proliferation, apoptosis and angiogenesis. It has been shown that human cancer cells are more sensitive to proteasome inhibition than normal cells, indicating that a proteasome inhibitor could be used as a novel anticancer drug. Indeed, this idea has been supported by the encouraging results of the clinical trials using the proteasome inhibitor Bortezomib (Velcade, PS-341), a drug approved by the US Food and Drug Administration (FDA). Several natural compounds, including the microbial metabolite lactacystin, green tea polyphenols, and traditional medicinal triterpenes, have been shown to be potent proteasome inhibitors. These findings suggest the potential use of natural proteasome inhibitors as not only chemopreventive and chemotherapeutic agents, but also tumor sensitizers to conventional radiotherapy and chemotherapy. In this review, we will summarize the structures and biological activities of the proteasome and several natural compounds with proteasome inhibitory activity, and will discuss the potential use of these compounds for the prevention and treatment of human cancers.

Pristimerin induces apoptosis by targeting the proteasome in prostate cancer cells

Pristimerin is a natural product derived from the Celastraceae and Hippocrateaceae families that were used as folk medicines for anti inflammation in ancient times. Although it has been shown that pristimerin induces apoptosis in breast cancer cells, the involved mechanism of action is unknown. The purpose of the current study is to investigate the primary target of pristimerin in human cancer cells, using prostate cancer cells as a working model. Nucleophilic susceptibility and in silico docking studies show that C6 of pristimerin is highly susceptible towards a nucleophilic attack by the hydroxyl group of N-terminal threonine of the proteasomal chymotrypsin subunit. Consistently, pristimerin potently inhibits the chymotrypsin-like activity of a purified rabbit 20S proteasome (IC50 2.2 micromol/L) and human prostate cancer 26S proteasome (IC50 3.0 micromol/L). The accumulation of ubiquitinated proteins and three proteasome target proteins, Bax, p27 and I kappa B-alpha, in androgen receptor (AR)-negative PC-3 prostate cancer cells supports the conclusion that proteasome inhibition by pristimerin is physiologically functional. This observed proteasome inhibition subsequently led to the induction of apoptotic cell death in a dose- and kinetic-dependent manner. Furthermore, in AR-positive, androgen-dependent LNCaP and AR-positive, androgen-independent C4-2B prostate cancer cells, proteasome inhibition by pristimerin results in suppression of AR protein prior to apoptosis. Our data demonstrate, for the first time, that the proteasome is a primary target of pristimerin in prostate cancer cells and inhibition of the proteasomal chymotrypsin-like activity by pristimerin is responsible for its cancer cell death-inducing property.

Antiproliferative activity of pristimerin isolated from Maytenus ilicifolia (Celastraceae) in human HL-60 cells

Pristimerin has been shown to be cytotoxic to several cancer cell lines. In the present work, the cytotoxicity of pristimerin was evaluated in human tumor cell lines and in human peripheral blood mononuclear cells (PBMC). This work also examined the effects of pristimerin (0.4; 0.8 and 1.7 microM) in HL-60 cells, after 6, 12 and 24h of exposure. Pristimerin reduced the number of viable cells and increased number of non-viable cells in a concentration-dependent manner by tripan blue test showing morphological changes consistent with apoptosis. Nevertheless, pristimerin was not selective to cancer cells, since it inhibited PBMC proliferation with an IC50 of 0.88 microM. DNA synthesis inhibition assessed by 5-bromo-2'-deoxyuridine (BrdU) incorporation in HL-60 cells was 70% and 83% for the concentrations of 0.4 and 0.8 microM, respectively. Pristimerin (10 and 20 microM) was not able to inhibit topoisomerase I. In AO/EB (acridine orange/ethidium bromide) staining, all tested concentrations reduced the number of HL-60 viable cells, with the occurrence of necrosis and apoptosis in a concentration-dependent manner, results in agreement with trypan blue exclusion findings. The analysis of membrane integrity and internucleosomal DNA fragmentation by flow cytometry in the presence of pristimerin indicated that treated cells underwent apoptosis. The present data point to the importance of pristimerin as representative of an emerging class of potential anticancer chemicals, exhibiting an antiproliferative effect by inhibiting DNA synthesis and triggering apoptosis.

Q39, a novel synthetic Quinoxaline 1,4-Di-N-oxide compound with anti-cancer activity in hypoxia

Hypoxia is one of the inevitable circumstances in various tumors and results in tumor resistance to radiotherapy and chemotherapy. The present data showed that 3-(4-bromophenyl)-2-(ethylsulfonyl)-6-methylquinoxaline 1,4-dioxide (Q39), derived from Quinoxaline 1,4-Di-N-oxide, possessed high anti-cancer activity in hypoxia. Cytotoxicity assay demonstrated that Q39 is a potential and high efficient anti-cancer compound in all tested cell lines with IC50 values of 0.18+/-0.03-8.88+/-1.12 microM in hypoxia and 0.33+/-0.04-8.74+/-1.28 microM in normoxia . In the following work concerning the mechanism of Q39 in hypoxia, we confirmed that Q39 could cause the apoptosis of K562 cells in a time-dependent manner. By fluorescence stain assay, Q39-induced mitochondria membrane potential (Delta Psi m) loss was observed in K562 cells in hypoxia. Based on the western blotting, Q39 decreased the protein expression of hypoxia-inducible factor-1alpha (HIF-1alpha) and vascular endothelial growth factor (VEGF) in hypoxia. The compound caused the activation of caspase-3 and subsequent cleavage of its substrate poly (ADP-ribose) polymerase (PARP) in hypoxia. Meanwhile, we found the upregulation of Bax by Q39 in K562 cells as well as the downregulation of Bcl-2. Q39 also influenced the expression of Mitogen-Activated Protein Kinase (MAPKs) and other proteins relative to mitochondria induced apoptosis. In addition, Q39-mediated apoptosis was not reversed after treatment with the JNK-specific inhibitor. In summary, the present study demonstrated Q39 was a novel compound against cancer cells in hypoxia. The mitochondrial pathway mediated by Bcl-2 protein family and MAPKs and the HIF-1 pathway might be involved in signaling Q39-induced apoptosis.

Pro-apoptotic effect of fly ash leachates in hepatocytes of freshwater fish (Channa punctata Bloch)

The pro-apoptotic effect of fly ash leachates (FAL) was studied in the hepatocytes of an Indian freshwater fish, Channa punctata Bloch. Hepatocytes were exposed to different concentrations of '7-day' FAL for 24 and 48h and various parameters of apoptosis were studied using standardized procedures. FAL-induced apoptosis in hepatocytes was indicated by cytological examination, DNA fragmentation and DNA laddering. The induction in cytochrome-c release, caspases 3, 7, 10 and 9 activities and lactate dehydrogenase level provide mechanistic platform for FAL-induced apoptosis. Cytological examination showed an unambiguous apoptotic effect of ash leachates in fish hepatocytes. Exposed hepatocytes also showed increased production of H(2)O(2), superoxide ions and an increase in lipid peroxidation (LPO). The present study suggests a possible role of reactive oxygen species (ROS) in FAL-induced apoptosis in hepatocytes. Lactate dehydrogenase, LPO and apoptosis as biomarkers of cytotoxicity have recently been used for assessment of ecotoxicological impact of environmental chemicals. Our findings show that these biomarkers may also be used for evaluation of ecotoxicological impact of complex chemical mixture such as fly ash and its leachates.

MZ3 induces apoptosis in human leukemia cells

PURPOSE

4-(4-Bromophenyl)-2,3-dihydro-N,3-bis(3,4,5-trimethoxyphenyl)-2-oxoidmi-dazole-1-carboxamide (MZ3) is one of the synthesized combretastatin-A-4 analogues and has been reported that it displayed a promising specific activity against leukemia cell lines. Our purpose was to investigate the mechanism of MZ3's cytotoxicity.

METHODS

Cytotoxicity was measured by MTT method, apoptosis was measured by flow cytometry. DNA fragmentation was tested by agarose gel electrophoresis. Mitochondrial membrane potential (DeltaPsim) was detected by JC1 staining and flow cytometry, while intracellular reactive oxygen species (ROS) was detected by 5-(and-6)-carboxy-2'-7'-dichlorofluorescin diacetate staining and flow cytometry. Protein expression was analyzed by western blotting. In vivo activity of MZ3 was assayed through severe combined immunodeficiency (SCID) mice model of human leukemia engrafts.

RESULTS

MZ3 exhibited high anti-cancer activity in six leukemia cell lines, including two drug-resistant cell lines. MZ3 induced DNA fragmentation, and caused an elevation of ROS and a loss of DeltaPsim in HL60 cells. MZ3 also induced the activation of caspase-3, influenced the expression of Bcl-2 family members, MAPKs and other proteins relative to mitochondria-induced apoptosis. In addition, N-acetylcysteine cannot inhibit HL60 cell apoptosis caused by MZ3. Furthermore, a prolonged survival time was observed after treatment with MZ3 in SCID mice model of human leukemia engrafts.

CONCLUSIONS

MZ3 is a potent compound against leukemia cell lines both in vitro and in vivo, and the mitochondrial pathway mediated by Bcl-2 protein family and MAPKs might be involved in signaling MZ3-induced apoptosis.

Mitochondria as therapeutic targets for cancer chemotherapy

Mitochondria are vital for cellular bioenergetics and play a central role in determining the point-of-no-return of the apoptotic process. As a consequence, mitochondria exert a dual function in carcinogenesis. Cancer-associated changes in cellular metabolism (the Warburg effect) influence mitochondrial function, and the invalidation of apoptosis is linked to an inhibition of mitochondrial outer membrane permeabilization (MOMP). On theoretical grounds, it is tempting to develop specific therapeutic interventions that target the mitochondrial Achilles' heel, rendering cancer cells metabolically unviable or subverting endogenous MOMP inhibitors. A variety of experimental therapeutic agents can directly target mitochondria, causing apoptosis induction. This applies to a heterogeneous collection of chemically unrelated compounds including positively charged alpha-helical peptides, agents designed to mimic the Bcl-2 homology domain 3 of Bcl-2-like proteins, ampholytic cations, metals and steroid-like compounds. Such MOMP inducers or facilitators can induce apoptosis by themselves (monotherapy) or facilitate apoptosis induction in combination therapies, bypassing chemoresistance against DNA-damaging agents. In addition, it is possible to design molecules that neutralize inhibitor of apoptosis proteins (IAPs) or heat shock protein 70 (HSP70). Such IAP or HSP70 inhibitors can mimic the action of mitochondrion-derived mediators (Smac/DIABLO, that is, second mitochondria-derived activator of caspases/direct inhibitor of apoptosis-binding protein with a low isoelectric point, in the case of IAPs; AIF, that is apoptosis-inducing factor, in the case of HSP70) and exert potent chemosensitizing effects.