Publications

  • [Show abstract] [Hide abstract]
    ABSTRACT: Reduced CYP2D6 metabolism and low Z-endoxifen (ENDX) concentrations may increase the risk of breast cancer recurrence in tamoxifen (TAM)-treated women. Little is known regarding the differences between TAM and ENDX murine pharmacokinetics or the effect of administration route on plasma concentrations of each drug.
    Cancer Chemotherapy and Pharmacology 10/2014; · 2.80 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Improving patient outcome by personalized therapy involves a thorough understanding of an agent's mechanism of action. β-Lapachone (clinical forms, Arq501/Arq761) has been developed to exploit dramatic cancer-specific elevations in the phase II detoxifying enzyme, NAD(P)H:quinone oxidoreductase (NQO1). NQO1 is dramatically elevated in solid cancers, including primary and metastatic (e.g., triple-negative (ER-, PR-, Her2/Neu-)) breast cancers. To define cellular factors that influence the efficacy of β-lapachone using knowledge of its mechanism of action, we confirmed that NQO1 was required for lethality and mediated a futile redox cycle where ~120 moles of superoxide were formed per mole of β-lapachone in 5 min. β-Lapachone induced reactive oxygen species (ROS), stimulated DNA single strand break-dependent PARP1 hyperactivation, caused dramatic loss of essential nucleotides (NAD+/ATP) and elicited programmed necrosis in breast cancer cells. While PARP1 hyperactivation and NQO1 expression were major determinants of β-lapachone-induced lethality, alterations in catalase expression, including treatment with exogenous enzyme, caused marked cytoprotection. Thus, catalase is an important resistance factor, and highlights H2O2 as an obligate ROS for cell death from this agent. Exogenous superoxide dismutase (SOD) enhanced catalase-induced cytoprotection. β-Lapachone-induced cell death included AIF translocation from mitochondria to nuclei, TUNEL+ staining, atypical PARP1 cleavage, and GAPDH S-nitrosylation, which were abrogated by catalase. We predict that the ratio of NQO1:catalase activities in breast cancer versus associated normal tissue are likely to be the major determinants affecting the therapeutic window of β-lapachone and other NQO1 bioactivatable drugs.
    Molecular Cancer Therapeutics 07/2013; · 5.60 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Aminoflavone is a unique DNA damaging agent currently undergoing phase I evaluation in a prodrug form (AFP464). In anticipation of combination regimens, interactions between aminoflavone and several anticancer drugs were investigated in MCF-7 breast cancer cells to determine whether synergistic cancer cell killing effects were observed. Colony formation assays were performed to assess the effect of combining aminoflavone with a variety of anticancer drugs. Changes in initial uptake, retention or efflux of aminoflavone and the second agent were compared to the behavior of drugs alone. Key features required for aminoflavone activity in cell culture models were also explored, focusing on the obligatory induction of CYP1A1/1A2 and binding of reactive aminoflavone metabolites to tumor cell total macromolecules and DNA. Aminoflavone was synergistic when co-incubated with paclitaxel, camptothecin or SN38. Uptake of neither aminoflavone nor any of the other three compounds was altered in combination incubations. Paclitaxel did not inhibit DNA binding of aminoflavone metabolites, while camptothecin did. Aminoflavone-induced CYP1A1 induction was observed in the presence of camptothecin or paclitaxel. Aminoflavone is a promising therapeutic agent for breast cancer due to its unique mechanism of action compared to commonly used drugs. Combined treatments utilizing aminoflavone in conjunction with paclitaxel or camptothecin may provide an even greater cytotoxic effect than achieved with aminoflavone alone.
    Cancer Chemotherapy and Pharmacology 12/2009; 66(3):575-83. · 2.80 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Commonly used antitumor agents, such as DNA topoisomerase I/II poisons, kill cancer cells by creating nonrepairable DNA double-strand breaks (DSBs). To repair DSBs, error-free homologous recombination (HR), and/or error-prone nonhomologous end joining (NHEJ) are activated. These processes involve the phosphatidylinositol 3'-kinase-related kinase family of serine/threonine enzymes: ataxia telangiectasia mutated (ATM), ATM- and Rad3-related for HR, and DNA-dependent protein kinase catalytic subunit (DNA-PKcs) for NHEJ. Alterations in these repair processes can cause drug/radiation resistance and increased genomic instability. beta-Lapachone (beta-lap; also known as ARQ 501), currently in phase II clinical trials for the treatment of pancreatic cancer, causes a novel caspase- and p53-independent cell death in cancer cells overexpressing NAD(P)H:quinone oxidoreductase-1 (NQO1). NQO1 catalyzes a futile oxidoreduction of beta-lap leading to reactive oxygen species generation, DNA breaks, gamma-H2AX foci formation, and hyperactivation of poly(ADP-ribose) polymerase-1, which is required for cell death. Here, we report that beta-lap exposure results in NQO1-dependent activation of the MRE11-Rad50-Nbs-1 complex. In addition, ATM serine 1981, DNA-PKcs threonine 2609, and Chk1 serine 345 phosphorylation were noted; indicative of simultaneous HR and NHEJ activation. However, inhibition of NHEJ, but not HR, by genetic or chemical means potentiated beta-lap lethality. These studies give insight into the mechanism by which beta-lap radiosensitizes cancer cells and suggest that NHEJ is a potent target for enhancing the therapeutic efficacy of beta-lap alone or in combination with other agents in cancer cells that express elevated NQO1 levels.
    Cancer Research 08/2007; 67(14):6936-45. · 8.65 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Lung cancer is the number one cause of cancer-related deaths in the world. Patients treated with current chemotherapies for non-small-cell lung cancers (NSCLCs) have a survival rate of ≈15% after 5 years. Novel approaches are needed to treat this disease. We show elevated NAD(P)H:quinone oxidoreductase-1 (NQO1) levels in tumors from NSCLC patients. β-Lapachone, an effective chemotherapeutic and radiosensitizing agent, selectively killed NSCLC cells that expressed high levels of NQO1. Isogenic H596 NSCLC cells that lacked or expressed NQO1 along with A549 NSCLC cells treated with or without dicoumarol, were used to elucidate the mechanism of action and optimal therapeutic window of β-lapachone. NSCLC cells were killed in an NQO1-dependent manner by β-lapachone (LD50, ≈4 μM) with a minimum 2-h exposure. Kinetically, β-lapachone-induced cell death was characterized by the following: (i) dramatic reactive oxygen species (ROS) formation, eliciting extensive DNA damage; (ii) hyperactivation of poly(ADP-ribose)polymerase-1 (PARP-1); (iii) depletion of NAD+/ATP levels; and (iv) proteolytic cleavage of p53/PARP-1, indicating μ-calpain activation and apoptosis. β-Lapachone-induced PARP-1 hyperactivation, nucleotide depletion, and apoptosis were blocked by 3-aminobenzamide, a PARP-1 inhibitor, and 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid acetoxymethyl ester (BAPTA-AM), a Ca2+ chelator. NQO1− cells (H596, IMR-90) or dicoumarol-exposed NQO1+ A549 cells were resistant (LD50, >40 μM) to ROS formation and all cytotoxic effects of β-lapachone. Our data indicate that the most efficacious strategy using β-lapachone in chemotherapy was to deliver the drug in short pulses, greatly reducing cytotoxicity to NQO1− “normal” cells. β-Lapachone killed cells in a tumorselective manner and is indicated for use against NQO1+ NSCLC cancers.
    Proceedings of the National Academy of Sciences 07/2007; 104(28):11832-11837. · 9.81 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Work from the laboratory of Dr. Arthur B. Pardee has highlighted basic principles that govern cellular and molecular biological processes in living cells. Among the most important governing principles in cellular and molecular responses are: (i) threshold "restriction" responses, wherein a level of response is reached and a "point of no return" is achieved; (ii) feedback regulation; and (iii) redundancy. Lessons learned from the molecular biology of cellular stress responses in mammalian cancer versus normal cells after ionizing radiation (IR) or chemotherapeutic agent exposures reveal similar instances of these guiding principles in mammalian cells. Among these are the: (i) induction of cell death responses by beta-lapachone (beta-lap), a naphthoquinone anti-tumor agent that kills cancer cells via an NQO1 (i.e., X-ray-inducible protein-3, xip3)-dependent mechanism; (ii) induction of secretory clusterin (sCLU) in response to TGF-beta1 exposure, and the ability of induced sCLU protein to down-regulate TGF-beta1 signaling; and (iii) induction of DNA mismatch repair-dependent G(2) cell cycle checkpoint responses after exposure to alkylating agents. We have learned these lessons and now adopted strategies to exploit them for improved therapy. These examples will be discussed and compared to the pioneering findings of researchers in the Pardee laboratory over the years.
    Journal of Cellular Physiology 01/2007; 209(3):604-10. · 4.22 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: After genotoxic stress poly(ADP-ribose) polymerase-1 (PARP-1) can be hyperactivated, causing (ADP-ribosyl)ation of nuclear proteins (including itself), resulting in NAD(+) and ATP depletion and cell death. Mechanisms of PARP-1-mediated cell death and downstream proteolysis remain enigmatic. beta-lapachone (beta-lap) is the first chemotherapeutic agent to elicit a Ca(2+)-mediated cell death by PARP-1 hyperactivation at clinically relevant doses in cancer cells expressing elevated NAD(P)H:quinone oxidoreductase 1 (NQO1) levels. Beta-lap induces the generation of NQO1-dependent reactive oxygen species (ROS), DNA breaks, and triggers Ca(2+)-dependent gamma-H2AX formation and PARP-1 hyperactivation. Subsequent NAD(+) and ATP losses suppress DNA repair and cause cell death. Reduction of PARP-1 activity or Ca(2+) chelation protects cells. Interestingly, Ca(2+) chelation abrogates hydrogen peroxide (H(2)O(2)), but not N-Methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced PARP-1 hyperactivation and cell death. Thus, Ca(2+) appears to be an important co-factor in PARP-1 hyperactivation after ROS-induced DNA damage, which alters cellular metabolism and DNA repair.
    Journal of Biological Chemistry 12/2006; 281(44):33684-96. · 4.65 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Defective or abortive repair of DNA lesions has been associated with carcinogenesis. Therefore it is imperative for a cell to accurately repair its DNA after damage if it is to return to a normal cellular phenotype. In certain circumstances, if DNA damage cannot be repaired completely and with high fidelity, it is more advantageous for an organism to have some of its more severely damaged cells die rather than survive as neoplastic transformants. A number of DNA repair inhibitors have the potential to act as anticarcinogenic compounds. These drugs are capable of modulating DNA repair, thus promoting cell death rather than repair of potentially carcinogenic DNA damage mediated by error-prone DNA repair processes. In theory, exposure to a DNA repair inhibitor during, or immediately after, carcinogenic exposure should decrease or prevent tumorigenesis. However, the ability of DNA repair inhibitors to prevent cancer development is difficult to interpret depending upon the system used and the type of genotoxic stress. Inhibitors may act on multiple aspects of DNA repair as well as the cellular signaling pathways activated in response to the initial damage. In this review, we summarize basic DNA repair mechanisms and explore the effects of a number of DNA repair inhibitors that not only potentiate DNA-damaging agents but also decrease carcinogenicity. In particular, we focus on a novel anti-tumor agent, beta-lapachone, and its potential to block transformation by modulating poly(ADP-ribose) polymerase-1.
    Journal of Molecular Histology 10/2006; 37(5-7):203-18. · 1.55 Impact Factor
  • Source
    Kathryn E. Reinicke, David A. Boothman
    [Show abstract] [Hide abstract]
    ABSTRACT: We report the development of mono(arylimino) derivatives of beta-lap as potential prodrugs (Reinicke et al. 2005). They undergo hydrolytic conversion to beta-lap at rates dependent on the electron-withdrawing strength of their substituent groups and pH of the diluent. Once converted, they caused NQO1-dependent, - calpain-mediated cell death in human cancer cells identical to that caused by beta-lap. NQO1 reduces beta-lap to an unstable hydroquinone that rapidly undergoes a two-step oxidation back to the parent compound. The resultant futile cycling generates reactive oxygen species (ROS). We hypothesize that O2"- is generated by the NQO1-mediated metabolism of -lap. Comet assay analyses and measurements of disulfide glutathione levels suggest that NQO1- dependent beta-lap metabolism produces DNA damaging oxidative stress. Our data indicate that ROS formation is upstream of subsequent endoplasmic reticulum calcium store release, suggesting that beta-lap-mediated ROS formation may be necessary, but not sufficient, to induce cell death.
    02/2006;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: beta-Lapachone, an o-naphthoquinone, induces a novel caspase- and p53-independent apoptotic pathway dependent on NAD(P)H:quinone oxidoreductase 1 (NQO1). NQO1 reduces beta-lapachone to an unstable hydroquinone that rapidly undergoes a two-step oxidation back to the parent compound, perpetuating a futile redox cycle. A deficiency or inhibition of NQO1 rendered cells resistant to beta-lapachone. Thus, beta-lapachone has great potential for the treatment of specific cancers with elevated NQO1 levels (e.g., breast, non-small cell lung, pancreatic, colon, and prostate cancers). We report the development of mono(arylimino) derivatives of beta-lapachone as potential prodrugs. These derivatives are relatively nontoxic and not substrates for NQO1 when initially diluted in water. In solution, however, they undergo hydrolytic conversion to beta-lapachone at rates dependent on the electron-withdrawing strength of their substituent groups and pH of the diluent. NQO1 enzyme assays, UV-visible spectrophotometry, high-performance liquid chromatography-electrospray ionization-mass spectrometry, and nuclear magnetic resonance analyses confirmed and monitored conversion of each derivative to beta-lapachone. Once converted, beta-lapachone derivatives caused NQO1-dependent, mu-calpain-mediated cell death in human cancer cells identical to that caused by beta-lapachone. Interestingly, coadministration of N-acetyl-l-cysteine, prevented derivative-induced cytotoxicity but did not affect beta-lapachone lethality. Nuclear magnetic resonance analyses indicated that prevention of beta-lapachone derivative cytotoxicity was the result of direct modification of these derivatives by N-acetyl-l-cysteine, preventing their conversion to beta-lapachone. The use of beta-lapachone mono(arylimino) prodrug derivatives, or more specifically a derivative converted in a tumor-specific manner (i.e., in the acidic local environment of the tumor tissue), should reduce normal tissue toxicity while eliciting tumor-selective cell killing by NQO1 bioactivation.
    Clinical Cancer Research 05/2005; 11(8):3055-64. · 7.84 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Severe trauma (e.g. whole body ionising radiation (IR)), leads to multiple organ dysfunction (MOD) and death. Although not completely understood, proposed triggering events of MOD include reactive oxygen species (ROS), released Ca(2+) from endoplasmic reticulum (ER) stores, cell debris resulting from apoptosis and/or necrosis, and liberation of cytokines. Little is known about the defence mechanisms that protect against events that trigger MOD. We propose that the secreted form of clusterin (sCLU) is a major protective factor against trauma-induced MOD. sCLU is induced by IR and by other cytoprotective agents. Interestingly, this secreted protein is cytoprotective in a variety of cell systems following various agents. We demonstrate that sCLU is induced by thapsigargin (TG), a sarcoplasmic-endoplasmic reticulum Ca(2+) ATPase (SERCA) pump inhibitor, which causes Ca(2+) release from the ER. sCLU induction was delayed, with the earliest increase in sCLU levels detected at 18-24 h post IR, and peak levels noted at 72-96 h. IR and TG exposures resulted in similar induction kinetics, wherein transcription and translation of sCLU occurred with nearly identical temporal responses. Human CLU promoter activity mimicked induction of sCLU protein levels (p<0.01). Interestingly, cells pre-treated with BAPTA-AM, an intracellular Ca(2+) chelator, did not prevent sCLU induction or lethality after TG or IR exposures. In fact, high dose exposures of BAPTA-AM induced sCLU responses. Thus, sCLU induction is triggered by ROS, changes in Ca(2+) homeostasis and lipid peroxidation, factors prominent in triggering MOD. Future studies should directly examine the role(s) of sCLU in preventing MOD, which may be very important in comtermeasures to MOD in accident victims.
    BJR supplement / BIR 02/2005; 27:106-13.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Beta-lapachone (beta-Lap) triggers apoptosis in a number of human breast and prostate cancer cell lines through a unique apoptotic pathway that is dependent upon NQO1, a two-electron reductase. Recently, our laboratory showed that beta-lap-exposed MCF-7 cells exhibited an early increase in intracellular cytosolic Ca(2+) from endoplasmic reticulum stores, and that BAPTA-AM (an intracellular Ca(2+) chelator) blocked these early increases and partially inhibited all aspects of beta-lap-induced apoptosis. We now show that exposure of NQO1-expressing breast cancer cells to beta-lap stimulates a unique proteolytic apoptotic pathway involving mu-calpain activation. No apparent activation of m-calpain was noted. Upon activation, mu-calpain translocated to the nucleus concomitant with specific nuclear proteolytic events. Apoptotic responses in beta-lap-exposed NQO1-expressing cells were significantly delayed and survival enhanced by exogenous over-expression of calpastatin, a natural inhibitor of mu- and m-calpains. Furthermore, purified mu-calpain cleaved PARP to a unique fragment (approximately 60 kDa), not previously reported for calpains. We provide evidence that beta-lap-induced, mu-calpain-stimulated apoptosis does not involve any known apoptotic caspases; the activated fragments of caspases were not observed after beta-lap exposures, nor were there any changes in the pro-enzyme forms as measured by Western blot analyses. The ability of beta-lap to trigger an apparently novel, p53-independent, calpain-mediated apoptotic cell death further support the development of this drug for improved breast cancer therapy.
    Cancer biology & therapy 2(2):141-52. · 3.29 Impact Factor

7 Following View all

12 Followers View all