Norcantharidin inhibits DNA replication and induces apoptosis with the cleavage of initiation protein Cdc6 in HL-60 cells

Norbornene and Related Structures as Scaffolds in the Search for New Cancer Treatments

The norbornene scaffold has arisen as a promising structure in medicinal chemistry due to its possible therapeutic application in cancer treatment. The development of norbornene-based derivatives as potential chemotherapeutic agents is attracting significant attention. Here, we report an unprecedented review on the recent advances of investigations into the antitumoral efficacy of different compounds, including the abovementioned bicyclic scaffold in their structure, in combination with chemotherapeutic agents or forming metal complexes. The impact that structural modifications to these bicyclic compounds have on the antitumoral properties and the mechanisms by which these norbornene derivatives act are discussed in this review. In addition, the use of norbornene, and its related compounds, encapsulation in nanosystems for its use in cancer therapies is here detailed.

Norcantharidin promotes cancer radiosensitization through Cullin1 neddylation-mediated CDC6 protein degradation

Radiotherapy (RT) is a conventional cancer therapeutic modality. However, cancer cells tend to develop radioresistance after a period of treatment. Diagnostic markers and therapeutic targets for radiosensitivity are severely lacking. Our recently published studies demonstrated that the cell division cycle (CDC6) is a critical molecule contributing to radioresistance, and maybe a potential therapeutic target to overcome radioresistance. In the present study, we for the first time reported that Norcantharidin (NCTD), a demethylated form of cantharidin, re-sensitized radioresistant cancer cells to overcome radioresistance, and synergistically promoted irradiation (IR)-induced cell killing and apoptosis by inducing CDC6 protein degradation. Mechanistically, NCTD induced CDC6 protein degradation through the ubiquitin-proteasome pathways. By using small interfering RNA (siRNA) interference or small compound inhibitors, we further determined that NCTD induced CDC6 protein degradation through a neddylation-dependent pathway, but not through Huwe1, Cyclin F, and APC/C-mediated ubiquitin-proteasome pathways. We screened the six most relevant Cullin subunits (CUL1, 2, 3, 4A, 4B, and 5) using siRNAs. The knockdown of Cullin1 but not the other five cullins remarkably elevated CDC6 protein levels. NCTD promoted the binding of Cullin1 to CDC6, thereby promoting CDC6 protein degradation through a Cullin1 neddylation-mediated ubiquitin-proteasome pathway. NCTD can be used in combination with radiotherapy to achieve better anticancer efficacy, or work as a radiosensitizer to overcome cancer radioresistance.

Insight into norcantharidin, a small-molecule synthetic compound with potential multi-target anticancer activities

Norcantharidin (NCTD) is a demethylated derivative of cantharidin, which is an anticancer active ingredient of traditional Chinese medicine, and is currently used clinically as a routine anti-cancer drug in China. Clarifying the anticancer effect and molecular mechanism of NCTD is critical for its clinical application. Here, we summarized the physiological, chemical, pharmacokinetic characteristics and clinical applications of NCTD. Besides, we mainly focus on its potential multi-target anticancer activities and underlying mechanisms, and discuss the problems existing in clinical application and scientific research of NCTD, so as to provide a potential anticancer therapeutic agent for human malignant tumors.

Cantharidic acid induces apoptosis of human leukemic HL-60 cells via c-Jun N-terminal kinase-regulated caspase-8/-9/-3 activation pathway

Cantharidin, a natural toxin from blister beetles, has shown potent anticancer activities on many solid tumor cells. Recently, cantharidin and its analogue, norcantharidin, were also shown to suppress nonsolid tumors such as chronic myeloid leukemia, acute myeloid leukemia (AML), and leukemic stem cells. However, there is no available information to address the effects of cantharidic acid (CAC), a hydrolysis product of cantharidin, on human AML cells. The present study showed that CAC, at a range of concentrations (0-20 μM), concentration-dependently inhibited cell proliferation in the HL-60 AML cell line. Western blot and flow cytometric assays demonstrated that CAC induced several features of apoptosis such as sub G1-phase cell increase, phosphatidylserine (PS) externalization, and significantly activated proapoptotic signaling including caspase-8, -9, and -3 activation and poly(ADP-ribose) polymerase (PARP) cleavage in HL-60 AML cells. Moreover, treatment of HL-60 cells with CAC induced concentration- and time- dependent activation of p38 mitogen-activated protein kinase (p38 MAPK) and c-Jun N-terminal kinase (JNK). Only JNK-, but not p38 MAPK-specific inhibitor can reverse the CAC-induced activation of the caspase-8, -9, and -3. We concluded that CAC can induce apoptosis in human leukemic HL-60 cells via a caspases-dependent pathway, and that the apoptosis-inducing effect of CAC can be regulated by JNK activation signaling.

Cytotoxicity of a Series of Norcantharidin-Inspired Tetrahydroepoxyisoindole Carboxamides

A series of 28 norcantharidin (NorC)-inspired analogues were accessed via a robust two-step Ugi intramolecular Diels-Alder (IMDA) sequence. Four analogues displayed whole-cell cytotoxicity equipotent to that of NorC and cisplatin against a number of cancer cell lines and a normal breast cell line (MCF10A). Notably, (3S,3aS,6R)-2-benzyl-7-methyl-N-(naphthalen-2-yl)-1-oxo-1,2,3,6-tetrahydro-3a,6-epoxyisoindole-3-carboxamide (trans-27) displayed superior whole-cell activity against breast (MCF-7, GI₅₀ =2.9 μm) and colon (HT29, GI₅₀ =6.4 μm) cancer cell lines relative to the control (cisplatin), which elicited respective GI₅₀ values of 6.5 and 11.3 μm against the aforementioned cell lines. This analogue also displayed improved activity relative to NorC across the breast (MCF-7, GI₅₀ =2.9 μm; NorC GI₅₀ =7.5 μm), ovarian (A2780, GI₅₀ =2.2 μm; NorC GI₅₀ =4.4 μm), and neuroblastoma (BE2-C, GI₅₀ =2.2 μm; NorC GI₅₀ =3.7 μm) cancer cell lines. Structure-activity relationship (SAR) investigations demonstrated that retention of sp² hybridized connections within the tetrahydroepoxyisoindole carboxamide scaffold is crucial, as aromatization to a phenolic functionality decreased activity, whereas removal of a single olefin bond abolished cytotoxicity. Nonetheless, with respect to the latter, use of crotonic acid as opposed 2-butynoic acid in the Ugi-IMDA sequence imparted a significant improvement to diastereoselectivity, with the cis/trans isomer ratio shifting from ≈1:1.2 to ≈0.5:9.5.

Role of Cdc6 During Oogenesis and Early Embryo Development in Mouse and Xenopus laevis

Cdc6 is an important player in cell cycle regulation. It is involved in the regulation of both S-phase and M-phase. Its role during oogenesis is crucial for repression of the S-phase between the first and the second meiotic M-phases, and it also regulates, via CDK1 inhibition, the M-phase entry and exit. This is of special importance for the reactivation of the major M-phase-regulating kinase CDK1 (Cyclin-Dependent Kinase 1) in oocytes entering metaphase II of meiosis and in embryo cleavage divisions, in which precise timing allows coordination between cell cycle events and developmental program of the embryo. In this chapter, we discuss the role of Cdc6 protein in oocytes and early embryos.

Comparative assessment of therapeutic safety of norcantharidin, N-farnesyloxy-norcantharimide, and N-farnesyl-norcantharimide against Jurkat T cells relative to human normal lymphoblast: A quantitative pilot study

The therapeutic safety of an anticancer drug is one of the most important concerns of the physician treating the cancer patient. Half maximal inhibitory concentration (IC50) and hillslope are usually used to represent the strength and sensitivity of an anticancer drug on cancer cells. The therapeutic safety of the anticancer drug can be assessed by comparing the IC50 and hillslope of anticancer drugs on cancer cells relative to normal cells. Since there are situations where "more anticancer activity" implies "more toxicity," the safety of an anticancer drug in these situations is hard to evaluate by using IC50 and hillslope alone. In a previous study, the "net effect" index was devised to represent the net therapeutic effects of one anticancer drug relative to the other. However, the therapeutic safety of one specific anticancer drug alone was not defined in the "net effect" index. This study introduced the "safety index (SI)" to quantify the degree of safety of an anticancer drug by using 4-parameter logistic model on cancer cells relative to normal cells. The therapeutic safety of norcantharidin (NCTD), N-farnesyloxy-norcantharimide (NOC15), and N-farnesyl-norcantharimide (NC15) in the treatment of Jurkat T cells relative to human normal lymphoblast was compared using the newly defined SI. We found that the SI of NOC15 and NC15 was significantly higher than that of NCTD, suggesting that both NOC15 and NC15 can damage more cancer cells and less normal cells than NCTD. We conclude that both NOC15 and NC15 are safer anticancer drugs than NCTD in the treatment of Jurkat T cells relative to human normal lymphoblast. The SI can be further applied to the screening, developments, and applications of anticancer drugs in the future.

N-Farnesyloxy-norcantharimide inhibits progression of human leukemic Jurkat T cells through regulation of mitogen-activated protein kinase and interleukin-2 production

This study investigated the anticancer effects of N-farnesyloxy-norcantharimide (NOC15), a newly synthesized norcantharidin (NCTD) analogue, on human leukemic Jurkat T cells and the signaling pathway underlying its effects. We found that the half maximal inhibitory concentration (IC50) of NOC15 on Jurkat T cells is 1.4 μmol/l, which is 11.14-fold (=15.6÷1.4) smaller than the 15.6 μmol/l of NCTD on Jurkat T cells, whereas the IC50 of NOC15 on human normal lymphoblast (HNL) is 207.9 μmol/l, which is 8.17-fold (=1698.0÷207.8) smaller than the 1698.0 μmol/l of NCTD on HNL cells. These results indicated that NOC15 exerts a higher anticancer effect on Jurkat T cells and has higher toxicity toward HNL cells than NCTD. Thus, NOC15 is 1.36-fold (=11.14÷8.17) beneficial as an anticancer agent toward Jurkat T cells compared with NCTD. Moreover, NOC15 can increase the percentage of cells in the sub-G1 phase and reduce the cell viability of Jurkat T cells, stimulate p38 and extracellular signal-regulated protein kinase 1/2 (ERK1/2) of mitogen-activated protein kinases (MAPKs) signaling pathway, and inhibit calcineurin expression and interleukin-2 (IL-2) production. However, NOC15 exerted no effects on the Jun-N-terminal kinase 1/2 (JNK1/2) signaling pathway, the production of IL-8, and tumor necrosis factor-α. We conclude that the anticancer activity of the newly synthesized NOC15 is 1.36-fold beneficial than NCTD as an anticancer agent and that NOC15 can increase the percentage of cells in the sub-G1 phase through the stimulation of p38 and ERK1/2 of the MAPK signaling pathway and the inhibition of calcineurin expression and IL-2 production. The NOC15 may have the potential of being developed into an anticancer agent in the future.

A potential small-molecule synthetic antilymphangiogenic agent norcantharidin inhibits tumor growth and lymphangiogenesis of human colonic adenocarcinomas through blocking VEGF-A,-C,-D/VEGFR-2,-3 "multi-points priming" mechanisms in vitro and in vivo

Background

Tumor lymphangiogenesis plays an important role in promoting growth and metastasis of tumors, but no antilymphangiogenic agent is used clinically. Based on the effect of norcantharidin (NCTD) on lymphangiogenesis of human lymphatic endothelial cells (LECs), we firstly investigated the antilymphangiogenic activity of NCTD as a tumor lymphangiogenic inhibitor for human colonic adenocarcinomas (HCACs).

Methods

In vivo and in vitro experiments to determine the effects of NCTD on tumor growth and lymphangiogenesis of the in-situ colonic xenografts in nude mice, and lymphatic tube formation of the three-dimensional (3-D) of the co-culture system of HCAC HT-29 cells and LECs were done. Proliferation, apoptosis, migration, invasion, Ki-67, Bcl-2 and cell cycle of LECs and the co-culture system in vitro were respectively determined. Streparidin-peroxidase staining, SABC, western blotting and RT-PCR were respectively used to examine the expression of LYVE-1, D2-40, CK20 (including their LMVD), and VEGF-A, VEGF-C, VEGF-D, VEGFR-2 and VEGFR-3 in vitro and in vivo.

Results

NCTD inhibited tumor growth and lymphangiogenesis of the in-situ colonic xenografts in vivo, and these observations were confirmed by facts that lymphatic tube formation, proliferation, apoptosis, migration, invasion, S-phase cell cycle, and Ki-67 and Bcl-2 expression in vitro, and LYVE-1, D2-40, CK20 expression and their LMVD in vitro and in vivo were inhibited and affected. Furthermore, the expression of VEGF-A, VEGF-C, VEGF-D, VEGFR-2 and VEGFR-3 at protein/mRNA levels in the process of lymphatic tube formation in vitro and tumor lymphangiogenesis in vivo was downregulated; NCTD in combination with mF4-31C1 or Sorafenib enhanced these effects.

Conclusions

NCTD inhibits tumor growth and lymphangiogenesis of HCACs through “multi-points priming” mechanisms i.e. affecting related malignant phenotypes, inhibiting Ki-67 and Bcl-2 expression, inducing S-phase cell cycle arrest, and directly or indirectly downregulating VEGF-A,-C,-D/VEGFR-2,-3 signaling pathways. The present finding strongly suggests that NCTD could serve as a potential antilymphangiogenic agent for tumor lymphangiogenesis and is of importance to explore NCTD is used for antitumor metastatic comprehensive therapy for HCACs.

N-Farnesyloxy-norcantharimide and N-farnesyl-norcantharimide inhibit the progression of leukemia and increase survival days in a syngeneic mouse leukemia model

This study investigated the anticancer effects of two newly synthesized norcantharidin analogs, N-farnesyloxy-norcantharimide (NOC15) and N-farnesyl-norcantharimide (NC15), in L1210 cells and in a syngeneic mouse leukemia model (L1210 cell line plus DBA/2 mice). We found that the half-maximal inhibitory concentration (IC50) of NOC15 and NC15 on L1210 cells is 1.56 and 2.62 μmol/l, respectively, and that the IC50 of NOC15 and NC15 on human normal lymphoblast is 207.9 and 2569 μmol/l, respectively. In cell cycle analysis, NOC15 could increase the sub-G1 phase, whereas NC15 could induce G2/M arrest. Annexin-V apoptosis assay indicated that both NOC15 and NC15 could induce cell apoptosis. In the syngeneic mouse leukemia model, both NOC15 and NC15 could increase the survival days of mice and decrease the tumor weight. Moreover, both NOC15 and NC15 could retard the increase in peripheral blood leukocyte count due to L1210 cells. In the subcutaneous (s.c.) group, the treatment with NOC15 could retard the decrease in the weight of the liver and the spleen caused by L1210 cells, whereas the treatment with NC15 could retard the decrease in the weight of the spleen caused by L1210 cells. We conclude that the new compounds NOC15 and NC15 have strong anticancer activity and low toxicity both in vitro and in vivo. NOC15 and NC15 may have the potential to be developed into anticancer agents in the future.

Inhibition of tumor vasculogenic mimicry and prolongation of host survival in highly aggressive gallbladder cancers by norcantharidin via blocking the ephrin type a receptor 2/focal adhesion kinase/paxillin signaling pathway

Vasculogenic mimicry (VM) is a newly-defined tumor microcirculation pattern in highly aggressive malignant tumors. We recently reported tumor growth and VM formation of gallbladder cancers through the contribution of the ephrin type a receptor 2 (EphA2)/focal adhesion kinase (FAK)/Paxillin signaling pathways. In this study, we further investigated the anti-VM activity of norcantharidin (NCTD) as a VM inhibitor for gallbladder cancers and the underlying mechanisms. In vivo and in vitro experiments to determine the effects of NCTD on tumor growth, host survival, VM formation of GBC-SD nude mouse xenografts, and vasculogenic-like networks, malignant phenotypes i.e., proliferation, apoptosis, invasion and migration of GBC-SD cells. Expression of VM signaling-related markers EphA2, FAK and Paxillin in vivo and in vitro were examined by immunofluorescence, western blotting and real-time polymerase chain reaction (RT-PCR), respectively. The results showed that after treatment with NCTD, GBC-SD cells were unable to form VM structures when injecting into nude mouse, growth of the xenograft was inhibited and these observations were confirmed by facts that VM formation by three-dimensional (3-D) matrix, proliferation, apoptosis, invasion, migration of GBC-SD cells were affected; and survival time of the xenograft mice was prolonged. Furthermore, expression of EphA2, FAK and Paxillin proteins/mRNAs of the xenografts was downregulated. Thus, we concluded that NCTD has potential anti-VM activity against human gallbladder cancers; one of the underlying mechanisms may be via blocking the EphA2/FAK/Paxillin signaling pathway.

Norcantharidin inhibits pre-replicative complexes assembly of HepG2 cells

Norcantharidin (NCTD) is currently used for anticancer therapy but the exact mechanism of action remains unknown. Pre-replicative complexes (pre-RCs) are essential for cell DNA replication and highly related to malignant proliferation. Here, we examined the inhibitory effect of NCTD on pre-RC components in HepG2 cells. We showed that NCTD induced degradation of Cdc6 and Mcm2 in a dose-dependent manner. Under 100 μM NCTD concentration, about 70% of Cdc6 and 50% of Mcm2 were degraded. In addition, the nuclear translocation of Mcm6 was inhibited by NCTD. Further studies aiming at G1 synchronous cells showed that, NCTD reduced the chromatin-bound Cdc6, Mcm2 and Mcm6. Moreover, the cells were blocked from entering the S phase and accumulated at the G1 phase when released synchronously into the cell cycle. Consistently, the DNA replication was inhibited by NCTD. Finally, the combination NCTD with Cdc6 depletion lead to more severe cytotoxicity (88%) than NCTD (52%) and Cdc6 depletion (39%) alone. A synergic cytotoxicity was observed between Cdc6 depletion and NCTD. In conclusion, our results demonstrate that NCTD inhibits pre-RC assembly; subsequently blocks the G1 to S transition; and inhibits DNA replication in HepG2 cells. Pre-RCs are an intriguing target for cancer therapy, which merits further investigations for anticancer development.

Preclinical evaluations of norcantharidin-loaded intravenous lipid microspheres with low toxicity

OBJECTIVES

The aim of this study was to perform a systematic preclinical evaluation of norcantharidin (NCTD)-loaded intravenous lipid microspheres (NLM).

RESEARCH DESIGN AND METHODS

Pharmacokinetics, biodistribution, antitumor efficacy and drug safety assessment (including acute toxicity, subchronic toxicity, hemolysis testing, intravenous stimulation and injection anaphylaxis) of NLM were carried out in comparison with the commercial product disodium norcantharidate injection (NI).

RESULTS

The pharmacokinetics of NLM in rats was similar to that of NI, and a non-linear correlation was observed between AUC and dose. A comparable antitumor efficacy of NLM and NI was observed in mice inoculated with A549, BEL7402 and BCAP-37 cell lines. It was worth noting that the NLM produced a lower drug concentration in heart compared with NI, and significantly reduced the cardiac and renal toxicity. The LD(50) of NLM was twice higher than that of NI. In NLM, over 80% of NCTD was loaded in the lipid phase or bound with phospholipids. Thus, NCTD was sequestered by direct contacting with body fluids and largely avoided distribution into tissues, consequently leading to significantly reduced cardiac and renal toxicity.

CONCLUSIONS

These preclinical results suggested that NLM could be a useful potential carrier for parenteral administration of NCTD, while providing a superior safety profile.

Effect of norcantharidin on the human breast cancer Bcap-37 cells

Norcantharidin (NCTD), a chemically modified form of cantharidin, is a potential anticancer drug. In this study, the effects of NCTD on the cellular viability, reactive oxygen species (ROS), mitochondrial membrane potential (MMP), and DNA damage in the human breast cancer cell line Bcap-37 were investigated with confocal and fluorescence microscopy. The cell cycle was further analyzed using the CellQuest software of a Becton-Dickinson FACS flow cytometer. The results indicated that the cellular viability was decreased with the growing concentrations of NCTD and time exposure. Moreover, the fluorescence intensity of ROS was increased, whereas the MMP was decreased in Bcap-37 cells with the growing concentrations of NCTD. NCTD induced a dose-dependent DNA damage and reduced the G1 peak in Bcap-37 cells. The G2/M peak of Bcap-37 was also decreased by the higher concentration of NCTD.

Norcantharidin Induces HL-60 Cells Apoptosis In Vitro

Norcantharidin (NCTD) is the demethylated form of cantharidin, which is the active substance of mylabris, and is known to have anticancer potentials. The aim of this paper was to assess the apoptosis-inducing effect of NCTD on HL-60 cells. Methods. The effects of NCTD were detected by flow cytometer on the cell toxicity, cell cycle, and apoptosis of HL-60 cells cultured in vitro. Results. After 48-hour treatment with NCTD, the growth of HL-60 cells was inhibited significantly. The summit of apoptosis appeared after 24 hours. The percentage of the cells in G₁ phase decreased and then increased in S and G₂+ M phase, while the S and G₂+ M phases were blocked after treatment with 5, 10, and 50 μmol/L NCTD for 24 hours. Conclusions. NCTD can induce the apoptosis of HL-60 cells and inhibit the fissiparism, and the domino effect was obviously correlated with the time and dosage.

Norcantharidin enhances ABT-737-induced apoptosis in hepatocellular carcinoma cells by transcriptional repression of Mcl-1

Small-molecule cell-permeable Bcl-2/Bcl-xL antagonist ABT-737 has recently emerged as a novel cancer therapeutic agent because it potently induces apoptosis in certain cancer cells. However, since ABT-737 binds to Mcl-1 with low affinity, ABT-737-mediated apoptosis signaling is inhibited in hepatocellular carcinoma (HCC) cells and other solid cancer cells due to the elevated expression of Mcl-1. Accordingly, strategies that target Mcl-1 are explored for overcoming ABT-737-resistance. In this study, we reported that Norcantharidin (NCTD), a small-molecule anticancer drug derived from Chinese traditional medicine blister beetle (Mylabris), induced transcriptional repression of Mcl-1 and considerably enhanced ABT-737-triggered cell viability inhibition and apoptosis in multiple HCC cell lines. Moreover, we observed that the enhancement of ABT-737-mediated apoptosis by NCTD was associated with activation of mitochondrial apoptosis signaling pathway, which involved cytosolic release of cytochrome c, cleavage of caspase-9 and caspase-3. Additionally, knockdown of Bax/Bak, the key effectors permeabilizing mitochondrial outer membrane significantly attenuated the enhancement, indicating mitochondrial apoptosis pathway played an essential role in the execution of the apoptosis. Finally, knockdown of Mcl-1 substantially potentiated ABT-737-mediated apoptotic cell death, confirming the potency of Mcl-1 repression by NCTD in enhancing ABT-737-induced apoptosis. These results therefore suggest that combination treatment with NCTD can overcome ABT-737 resistance and enhance ABT-737 therapeutic efficacy in treating human HCC.

Fighting fire with fire: poisonous Chinese herbal medicine for cancer therapy

ETHNOPHARMACOLOGICAL RELEVANCE

Following the known principle of "fighting fire with fire", poisonous Chinese herbal medicine (PCHM) has been historically used in cancer therapies by skilled Chinese practitioners for thousands of years. In fact, most of the marketed natural anti-cancer compounds (e.g., camptothecin derivatives, vinca alkaloids, etc.) are often known in traditional Chinese medicine (TCM) and recorded as poisonous herbs as well. Inspired by the encouraging precedents, significant researches into the potential of novel anticancer drugs from other PCHM-derived natural products have been ongoing for several years and PCHM is increasingly being recognized as a gathering place for promising anti-cancer drugs. The present review aimed at giving a rational understanding of the toxicity of PCHM and, especially, providing the most recent developments on PCHM-derived anti-cancer compounds.

MATERIALS AND METHODS

Information on the toxicity and safety control of PCHM, as well as PCHM-derived anti-cancer compounds, was gathered from the articles, books and monographs published in the past 20 years.

RESULTS

Based on an objective introduction to the CHM toxicity, we clarified the general misconceptions about the safety of CHM and summarized the traditional experiences in dealing with the toxicity. Several PCHM-derived compounds, namely gambogic acid, triptolide, arsenic trioxide, and cantharidin, were selected as representatives, and their traditional usage and mechanism of anti-cancer actions were discussed.

CONCLUSIONS

Natural products derived from PCHM are of extreme importance in devising new drugs and providing unique ideas for the war against cancer. To fully exploit the potential of PCHM in cancer therapy, more attentions are advocated to be focused on their safety evaluation and mechanism exploration.

3A4, a new potential target for B and myeloid lineage leukemias

Antibody-targeting therapy has drawn great interests to the hematologists and oncologists. Many antibodies have been studied for their potential targeting for hematopoietic malignancies. A few have been proved to be very effective for patients with these diseases. However, more antibodies are needed for clinical use. CD45 and its isoforms may convey clinical potential in terms of targeting therapy. Zhejiang Children's Hospital (ZCH)-6-3A4 (3A4), a novel antibody that can recognize an isoform of CD45 has been found to react with restricted cell components in hematopoietic system, which may have the potential for targeting therapy. Herein, we conducted an in vitro study of our newly prepared antibody 3A4 using various cellular and immunocytological methods. The results showed that the antibody 3A4 (murine IgG1κ) was a new clone of anti-CD45RA. It could block the binding to an epitope of CD45RA recognized by a standard anti-CD45RA antibody (Clone name L48). The reactivity of the 3A4 to both fresh leukemia cells from patients and well-defined leukemia cell lines was largely similar to those of L48, but the former recognized more leukemia cells than the latter. Cytometric analysis after papain treatment showed that the internalization rate of the 3A4 antibody to the target cells was as high as 71.3% after incubation at 37°C for 4 h, which was significantly higher than that of L48 (20.4%). The norcantharidin (NCTD)-conjugated immunotoxin (NCTD-3A4) was generated using an active ester method. The targeting inhibition rate on KG1a was as high as 61.10% after 96 h incubation in a dose-dependent manner, which was significantly higher than that (3.56%, P < 0.01) with 3A4-negative Nalm-6 cells. In conclusion, our new anti-CD45RA antibody 3A4 is probably a new target molecule of leukemia cells and holds a targeting therapeutic potential for hematopoietic malignancies, which warrants further development of this agent.

Norcantharidin reduced cyclins and cytokines production in human peripheral blood mononuclear cells

AIMS

To evaluate potential agents of therapeutic value in tissue inflammation, we studied norcantharidin (NCTD) and its derivatives for their effects on immune responses of human peripheral blood mononuclear cells (PBMC) in vitro.

MAIN METHODS

PBMC proliferation was evaluated by tritiated thymidine uptake method. The production and gene expression of cytokines were determined with enzyme immunoassays (EIA) and reverse transcription-polymerase chain reaction (RT-PCR), respectively.

KEY FINDINGS

Five derivatives from NCTD had no significant effect on cell proliferation in PBMC. NCTD inhibited PBMC proliferation induced by phytohemagglutinin (PHA) with a 50% inhibitory concentration (IC(50)) 42.1+/-2.3 microM. The inhibitory action of NCTD did not involve direct cytotoxicity. To localize the point in the PBMC proliferation where arrest occurred, a set of key regulatory events leading to the cell proliferation, including cell cycle progression, production and gene expression of interleukin-2 (IL-2), IL-4, IL-10, and interferon-gamma (IFN-gamma) and cyclins was examined. Data demonstrated NCTD arrested the cell cycle progression of activated PBMC from the G1 transition to the S phase. The cyclin D3, E, A, and B transcripts and protein production in PHA-treated PBMC was reduced by NCTD. Whereas NCTD exerted no effect on IL-4 and IFN-gamma production, it significantly alleviated the production and mRNA expression of IL-2 and IL-10 in activated PBMC.

SIGNIFICANCE

The suppressant effects of NCTD on proliferation of PBMC activated by PHA therefore appear to be mediated, at least in part, through inhibition of cyclins and IL-2 production and arrest of cell cycle progression in the cells.

Progress in the treatment of hepatitis B and digestive tumors with cantharidin and its analogues

Blister beetle or mylabris, pungent in flavor and toxic in nature, has been used for more than 2000 years as traditional Chinese medicine in China. Cantharidin, an active ingredient of the blister beetle, is an effective therapeutic agent against cancers of the liver, breast, esophagus, lung and intestine, etc. However, it is very toxic. Nocantharidin (NCTD), a derivative of cantharidin first synthesized in China, is a new anti-tumor drug with strong anti-tumor activities and increases the number of while blood cells. Cantharidin can be used in the treatment of hepatitis B and pointed condyloma. This paper reviews the progress in its clinical applications at home and abroad.

Mechanisms to control rereplication and implications for cancer

Recent advances in the replication field have highlighted how the replication initiator proteins are negatively regulated by inhibitor proteins and ubiquitin-mediated degradation in mammalian cells to prevent rereplication. When these regulatory pathways go awry, uncontrolled rereplication ensues and a G2/M checkpoint is evoked to prevent cellular death. Many components of the checkpoints activated by rereplicaton are important for cancer prevention by facilitating DNA damage repair processes. The pathways that prevent rereplication themselves have also recently been implicated in preventing tumorigenesis. Studies from patient tumors, genetically altered mice, and mammalian cell culture suggest that deregulation of replication licensing proteins results in an increase in aneuploidy, chromosomal fusions, and DNA breaks. These studies provide a framework to address how regulators of replication function to maintain genomic stability.

DNA damage induced by novel demethylcantharidin-integrated platinum anticancer complexes

Oxaliplatin is a third generation platinum (Pt) drug with a diaminocyclohexane (DACH) entity, which has recently obtained worldwide approval for the clinical treatment of colon cancer, and apparently operates by a different mechanism of action to the classical cisplatin or carboplatin. Introducing a novel dual mechanism of action is one approach in designing a new platinum-based anticancer agent, whereby an appropriate ligand, such as demethylcantharidin (DMC), is released from the parent compound to exert a cytotoxic effect, in addition to that of the DNA-alkylating function of the platinum moiety. To investigate the likelihood of a novel dual mechanism of anticancer action, demethylcantharidin-integrated Pt complexes: Pt(R,R-DACH)(DMC) with the same Pt-DACH moiety as oxaliplatin, and Pt(NH(3))(2)(DMC) akin to carboplatin; were studied for their ability to induce DNA damage in HCT116 colorectal cancer cells by an alkaline comet assay. The results showed that the DMC ligand released from the novel complexes caused additional DNA lesions when compared with oxaliplatin and carboplatin. The comet assay also revealed that the DNA-damaging behavior of cisplatin is characteristically different; and this study is the first to demonstrate the ability of DMC to induce DNA lesions, thus providing sufficient evidence to explain the superior antiproliferative effect of the novel DMC-integrated complexes.

Molecular biology of cantharidin in cancer cells

Herbal medicine is one of the forms of traditional medical practice. Traditional Chinese medicine (TCM) and traditional Vietnamese medicine (TVM) are well-known for their long-standing tradition of herbal medicine. Secreted by many species of blister beetle, most notably by the 'Spanish fly' (Lytta vesicatoria), cantharidin inhibits protein phosphatases 1 and 2A (PP1, PP2A). Blister beetle has been used in Asian traditional medicine to treat Molluscum contagiosum virus (MCV) infections and associated warts, and is now also used for cancer treatment. A combination of both genomic and postgenomic techniques was used in our studies to identify candidate genes affecting sensitivity or resistance to cantharidin. Cantharidin was not found to be related to multidrug resistance phenotype, suggesting its potential usefulness for the treatment of refractory tumors. Oxidative stress response genes diminish the activity of cantharidin by inducing DNA strand breaks which may be subject to base excision repair and induce apoptosis in a p53- and Bcl2-dependent manner. Cantharidin is one of many natural products used in traditional Chinese medicine and traditional Vietnamese medicine for cancer treatment. Combined methods of pharmaceutical biology and molecular biology can help elucidate modes of action of these natural products.

Comparison of acute toxicity of two preparations of norcantharidin in mice

OBJECTIVE

To compare the acute toxicity of common injection and sustained-release preparation of norcantharidin for mice so as to identify the attenuation of the sustained-release preparation of norcantharidin.

METHODS

The poloxamer 407 was used as a sustained-release vehicle for topical administration of norcantharidin, and the acute toxicity of mice treated with common injection and sustained-release preparation of norcantharidin was observed. The median lethal dose (LD(50)) was calculated by Bliss software.

RESULTS

The symptoms of mice were similar between the two groups, but the appearance of symptoms in norcantharidin/poloxamer 407 group was 4 hours later than that in norcantharidin group. The LD(50) of norcantharidin administered through vein injection was 12.6 mg/kg. The LD(50) of norcantharidin/poloxamer 407 administered through intraperitoneal injection, intrahepatic injection and intramuscular injection were 19.9, 19.1 and 20.9 mg/kg, respectively, and the LD(50) of the common preparation were 13.0, 13.1 and 15.1 mg/kg, respectively.

CONCLUSION

The norcantharidin/poloxamer 407 is less toxic than the equivalent dose of norcantharidin, mainly because norcantharidin/poloxamer 407 may release norcantharidin sustainedly, thus reducing norcantharidin concentration in blood.