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ACS Omega Feb 2020Triethylphosphinegold(I) complexes [Au(HL1)P(CHCH)]PF (), [Au(HL2)P(CHCH)]PF (), and [Au(HL3)P(CHCH)]PF () were obtained with...
Triethylphosphinegold(I) complexes [Au(HL1)P(CHCH)]PF (), [Au(HL2)P(CHCH)]PF (), and [Au(HL3)P(CHCH)]PF () were obtained with ()-2-(1-(2-methyl-5-nitro-1H-imidazol-1-yl)propan-2-ylidene)hydrazinecarbothioamide (), ()--methyl-2-(1-(2-methyl-5-nitro-1H-imidazol-1-yl)propan-2-ylidene)hydrazinecarbothioamide (), and ()-2-(1-(2-methyl-5-nitro-1H-imidazol-1-yl)propan-2-ylidene)--phenylhydrazinecarbothioamide (). All compounds were assayed for their cytotoxic activities against HCT-116 colorectal carcinoma cells under normoxia and hypoxia conditions and against nonmalignant HEK-293 human embryonic kidney cells under normoxia conditions. The thiosemicarbazone ligands - were inactive against HCT-116 cells under hypoxia but while was inactive, and proved to be cytotoxic to both cell lineages under normoxia conditions. Complexes (-) and the triethylphosphinegod(I) precursor proved to be active against both cell lineages in normoxia as well as in hypoxia. While and revealed to be active against HEK-293 and HCT-116 cells, being approximately as active against HCT-116 cells in normoxia as under hypoxia, complex () proved to be more active against HCT-116 cells under hypoxia than under normoxia conditions, and more active against HCT-116 cells than against the nonmalignant HEK-293 cells, with the selectivity index, calculated as SI = IC/IC, equal to 3.7, similar to the value obtained for the control drug tirapazamine (tirapazamine (TPZ), SI = 4). Although the compounds showed distinct cytotoxic activities, the electrochemical behaviors of - were very similar, as were the behaviors of complexes (-). Complex () deserves special interest since it was significantly more active under hypoxia than under normoxia conditions. Hence, in this case, selective reduction of the nitro group in a low oxygen pressure environment, resulting in toxic reactive oxygen species (ROS) and damage to DNA or other biomolecules, might operate, while for the remaining compounds, other modes of action probably occur.
PubMed: 32095716
DOI: 10.1021/acsomega.9b03778 -
Molecules (Basel, Switzerland) Jul 2019Extracellular acidification is an important feature of tumor microenvironments but has yet to be successfully exploited in cancer therapy. The reversal of the pH...
Extracellular acidification is an important feature of tumor microenvironments but has yet to be successfully exploited in cancer therapy. The reversal of the pH gradient across the plasma membrane in cells that regulate intracellular pH (pHi) has potential to drive the selective uptake of weak acids at low extracellular pH (pHe). Here, we investigate the dual targeting of low pHe and hypoxia, another key feature of tumor microenvironments. We prepared eight bioreductive prodrugs based on the benzotriazine di-oxide (BTO) nucleus by appending alkanoic or aminoalkanoic acid sidechains. The BTO acids showed modest selectivity for both low pHe (pH 6.5 versus 7.4, ratios 2 to 5-fold) and anoxia (ratios 2 to 8-fold) in SiHa and FaDu cell cultures. Related neutral BTOs were not selective for acidosis, but had greater cytotoxic potency and hypoxic selectivity than the BTO acids. Investigation of the uptake and metabolism of representative BTO acids confirmed enhanced uptake at low pHe, but lower intracellular concentrations than expected for passive diffusion. Further, the modulation of intracellular reductase activity and competition by the cell-excluded electron acceptor WST-1 suggests that the majority of metabolic reductions of BTO acids occur at the cell surface, compromising the engagement of the resulting free radicals with intracellular targets. Thus, the present study provides support for designing bioreductive prodrugs that exploit pH-dependent partitioning, suggesting, however, that that the approach should be applied to prodrugs with obligate intracellular activation.
Topics: Cell Hypoxia; Cell Line, Tumor; Chemical Phenomena; Dose-Response Relationship, Drug; Drug Design; Humans; Hydrogen-Ion Concentration; Models, Biological; Molecular Structure; Neoplasms; Oxidation-Reduction; Oxides; Prodrugs; Triazines
PubMed: 31295864
DOI: 10.3390/molecules24142524 -
The Journal of Clinical Investigation Jun 2021Hypoxia, a hallmark feature of the tumor microenvironment, causes resistance to conventional chemotherapy, but was recently reported to synergize with poly(ADP-ribose)...
Hypoxia, a hallmark feature of the tumor microenvironment, causes resistance to conventional chemotherapy, but was recently reported to synergize with poly(ADP-ribose) polymerase inhibitors (PARPis) in homologous recombination-proficient (HR-proficient) cells through suppression of HR. While this synergistic killing occurs under severe hypoxia (<0.5% oxygen), our study shows that moderate hypoxia (2% oxygen) instead promotes PARPi resistance in both HR-proficient and -deficient cancer cells. Mechanistically, we identify reduced ROS-induced DNA damage as the cause for the observed resistance. To determine the contribution of hypoxia to PARPi resistance in tumors, we used the hypoxic cytotoxin tirapazamine to selectively kill hypoxic tumor cells. We found that the selective elimination of hypoxic tumor cells led to a substantial antitumor response when used with PARPi compared with that in tumors treated with PARPi alone, without enhancing normal tissue toxicity. Since human breast cancers with BRAC1/2 mutations have an increased hypoxia signature and hypoxia reduces the efficacy of PARPi, then eliminating hypoxic tumor cells should enhance the efficacy of PARPi therapy.
Topics: Animals; Cell Hypoxia; Cell Line, Tumor; DNA Damage; Female; Homologous Recombination; Humans; Mice; Mice, Nude; Neoplasms, Experimental; Poly(ADP-ribose) Polymerase Inhibitors; Reactive Oxygen Species; Xenograft Model Antitumor Assays
PubMed: 34060485
DOI: 10.1172/JCI146256 -
Angewandte Chemie (International Ed. in... Sep 2020Tirapazamine (TPZ) has been tested in clinical trials on radio-chemotherapy due to its potential highly selective toxicity towards hypoxic tumor cells. It was suggested...
Tirapazamine (TPZ) has been tested in clinical trials on radio-chemotherapy due to its potential highly selective toxicity towards hypoxic tumor cells. It was suggested that either the hydroxyl radical or benzotriazinyl radical may form as bioactive radical after the initial reduction of TPZ in solution. In the present work, we studied low-energy electron attachment to TPZ in the gas phase and investigated the decomposition of the formed TPZ anion by mass spectrometry. We observed the formation of the (TPZ-OH) anion accompanied by the dissociation of the hydroxyl radical as by far the most abundant reaction pathway upon attachment of a low-energy electron. Quantum chemical calculations suggest that NH pyramidalization is the key reaction coordinate for the reaction dynamics upon electron attachment. We propose an OH roaming mechanism for other reaction channels observed, in competition with the OH dissociation.
PubMed: 32543771
DOI: 10.1002/anie.202006675 -
Molecules (Basel, Switzerland) Oct 2020Hypoxia is an adverse prognostic feature of solid cancers that may be overcome with hypoxia-activated prodrugs (HAPs). Tirapazamine (TPZ) is a HAP which has undergone...
Hypoxia is an adverse prognostic feature of solid cancers that may be overcome with hypoxia-activated prodrugs (HAPs). Tirapazamine (TPZ) is a HAP which has undergone extensive clinical evaluation in this context and stimulated development of optimized analogues. However the subcellular localization of the oxidoreductases responsible for mediating TPZ-dependent DNA damage remains unclear. Some studies conclude only nuclear-localized oxidoreductases can give rise to radical-mediated DNA damage and thus cytotoxicity, whereas others identify a broader role for endoplasmic reticulum and cytosolic oxidoreductases, indicating the subcellular location of TPZ radical formation is not a critical requirement for DNA damage. To explore this question in intact cells we engineered MDA-231 breast cancer cells to express the TPZ reductase human NADPH: cytochrome P450 oxidoreductase (POR) harboring various subcellular localization sequences to guide this flavoenzyme to the nucleus, endoplasmic reticulum, cytosol or inner surface of the plasma membrane. We show that all POR variants are functional, with differences in rates of metabolism reflecting enzyme expression levels rather than intracellular TPZ concentration gradients. Under anoxic conditions, POR expression in all subcellular compartments increased the sensitivity of the cells to TPZ, but with a fall in cytotoxicity per unit of metabolism (termed 'metabolic efficiency') when POR is expressed further from the nucleus. However, under aerobic conditions a much larger increase in cytotoxicity was observed when POR was directed to the nucleus, indicating very high metabolic efficiency. Consequently, nuclear metabolism results in collapse of hypoxic selectivity of TPZ, which was further magnified to the point of reversing O dependence (oxic > hypoxic sensitivity) by employing a DNA-affinic TPZ analogue. This aerobic hypersensitivity phenotype was partially rescued by cellular copper depletion, suggesting the possible involvement of Fenton-like chemistry in generating short-range effects mediated by the hydroxyl radical. In addition, the data suggest that under aerobic conditions reoxidation strictly limits the TPZ radical diffusion range resulting in site-specific cytotoxicity. Collectively these novel findings challenge the purported role of intra-nuclear reductases in orchestrating the hypoxia selectivity of TPZ.
Topics: Antineoplastic Agents; Cell Engineering; Cell Hypoxia; Cell Line, Tumor; Cell Membrane; Cell Nucleus; Cell Survival; Copper; DNA Damage; Humans; Hypoxia; Models, Biological; NADPH-Ferrihemoprotein Reductase; Oxygen; Prodrugs; Tirapazamine
PubMed: 33105798
DOI: 10.3390/molecules25214888 -
Journal of Nanobiotechnology Mar 2021Areas of hypoxia are often found in triple-negative breast cancer (TNBC), it is thus more difficult to treat than other types of breast cancer, and may require...
BACKGROUND
Areas of hypoxia are often found in triple-negative breast cancer (TNBC), it is thus more difficult to treat than other types of breast cancer, and may require combination therapies. A new strategy that combined bioreductive therapy with photodynamic therapy (PDT) was developed herein to improve the efficacy of cancer treatment. Our design utilized the characteristics of protoporphyrin IX (PpIX) molecules that reacted and consumed O at the tumor site, which led to the production of cytotoxic reactive oxygen species (ROS). The low microenvironmental oxygen levels enabled activation of a bioreductive prodrug, tirapazamine (TPZ), to become a toxic radical. The TPZ radical not only eradicated hypoxic tumor cells, but it also promoted therapeutic efficacy of PDT.
RESULTS
To achieve the co-delivery of PpIX and TPZ for advanced breast cancer therapy, thin-shell hollow mesoporous Ia3d silica nanoparticles, designated as MMT-2, was employed herein. This nanocarrier designed to target the human breast cancer cell MDA-MB-231 was functionalized with PpIX and DNA aptamer (LXL-1), and loaded with TPZ, resulting in the formation of TPZ@LXL-1-PpIX-MMT-2 nanoVector. A series of studies confirmed that our nanoVectors (TPZ@LXL-1-PpIX-MMT-2) facilitated in vitro and in vivo targeting, and significantly reduced tumor volume in a xenograft mouse model. Histological analysis also revealed that this nanoVector killed tumor cells in hypoxic regions efficiently.
CONCLUSIONS
Taken together, the synergism and efficacy of this new therapeutic design was confirmed. Therefore, we concluded that this new therapeutic strategy, which exploited a complementary combination of PpIX and TPZ, functioned well in both normoxia and hypoxia, and is a promising medical procedure for effective treatment of TNBC.
Topics: Animals; Antineoplastic Agents; Aptamers, Nucleotide; Cell Line, Tumor; Combined Modality Therapy; Female; Humans; Mice; Nanoparticles; Oxygen; Photochemotherapy; Prodrugs; Reactive Oxygen Species; Silicon Dioxide; Tirapazamine; Triple Negative Breast Neoplasms; Tumor Burden; Tumor Hypoxia; Xenograft Model Antitumor Assays
PubMed: 33781277
DOI: 10.1186/s12951-021-00786-8 -
ACS Omega Jul 2020The process selection and subsequent development of a reliable, scalable synthesis of the anticancer prodrug tirapazamine (SR259075) is described in this paper. Reaction...
The process selection and subsequent development of a reliable, scalable synthesis of the anticancer prodrug tirapazamine (SR259075) is described in this paper. Reaction of benzofuroxan with cyanamide in acetonitrile in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene at 20-25 °C afforded, after an acidic workup, the targeted molecule in good yield at a kilogram scale. Notable critical parameters and safety enhancements are defined and successfully implemented to produce three consecutive validation batches in a reproducible manner.
PubMed: 32685820
DOI: 10.1021/acsomega.0c01250 -
Journal of Nanobiotechnology Jun 2024Hypoxia-activated prodrug (HAP) is a promising candidate for highly tumor-specific chemotherapy. However, the oxygenation heterogeneity and dense extracellular matrix...
BACKGROUND
Hypoxia-activated prodrug (HAP) is a promising candidate for highly tumor-specific chemotherapy. However, the oxygenation heterogeneity and dense extracellular matrix (ECM) of tumor, as well as the potential resistance to chemotherapy, have severely impeded the resulting overall efficacy of HAP.
RESULTS
A HAP potentiating strategy is proposed based on ultrasound responsive nanodroplets (PTP@PLGA), which is composed of protoporphyrin (PpIX), perfluoropropane (PFP) and a typical HAP, tirapazamine (TPZ). The intense vaporization of PFP upon ultrasound irradiation can magnify the sonomechanical effect, which loosens the ECM to promote the penetration of TPZ into the deep hypoxic region. Meanwhile, the PpIX enabled sonodynamic effect can further reduce the oxygen level, thus activating the TPZ in the relatively normoxic region as well. Surprisingly, abovementioned ultrasound effect also results in the downregulation of the stemness of cancer cells, which is highly associated with drug-refractoriness.
CONCLUSIONS
This work manifests an ideal example of ultrasound-based nanotechnology for potentiating HAP and also reveals the potential acoustic effect of intervening cancer stem-like cells.
Topics: Humans; Tirapazamine; Protoporphyrins; Fluorocarbons; Prodrugs; Cell Line, Tumor; Nanoparticles; Neoplastic Stem Cells; Antineoplastic Agents; Ultrasonic Waves; Animals; Extracellular Matrix; Mice; Neoplasms
PubMed: 38907270
DOI: 10.1186/s12951-024-02623-0 -
Journal of Pharmacy & Pharmaceutical... 2020The reduction potentials of bioreductively-activated drugs represent an important design parameter to be accommodated in the course of creating lead compounds and...
The reduction potentials of bioreductively-activated drugs represent an important design parameter to be accommodated in the course of creating lead compounds and improving the efficacy of older generation drugs. Reduction potentials are traditionally reported as single-electron reduction potentials, E(1), measured against reference electrodes under strictly defined experimental conditions. More recently, computational chemists have described redox properties in terms of a molecule's highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), in electron volts (eV). The relative accessibility of HOMO/LUMO data through calculation using today's computer infrastructure and simplified algorithms make the calculated value (LUMO) attractive in comparison to the accepted but rigorous experimental determination of E(1). This paper describes the correlations of eV (LUMO) to E(1) for three series of bioreductively-activated benzotriazine di-N-oxides (BTDOs), ring-substituted BTDOs, ring-added BTDOs and a selection of aromatic nitro compounds. The current computational approach is a closed-shell calculation with a single optimization. Gas phase geometry optimization was followed by a single-point DFT (Density Functional Theory) energy calculation in the gas phase or in the presence of polar solvent. The resulting DFT-derived LUMO energies (eV) calculated for BTDO analogues in gas phase and in presence of polar solvent (water) exhibited very strong linear correlations with high computational efficiency (r2 = 0.9925) and a very high predictive ability (MAD = 7 mV and RMSD = 9 mV) when compared to reported experimentally determined single-electron reduction potentials.
Topics: Density Functional Theory; Electrons; Hypoxia; Oxidation-Reduction; Tirapazamine
PubMed: 32574141
DOI: 10.18433/jpps30602 -
APL Bioengineering Sep 2020Hepatocellular carcinoma (HCC) is an intractable cancer with a high mortality rate. Transarterial chemoembolization (TACE), a non-curative method, is the first line...
Hepatocellular carcinoma (HCC) is an intractable cancer with a high mortality rate. Transarterial chemoembolization (TACE), a non-curative method, is the first line therapy for intermediate stage patients. This effectively extends patient survival but requires a complicated intraarterial catheterization procedure and is poorly suited to repeated administration. Here, we investigate gas chemoembolization, a less invasive, more easily administered transient occlusion method that circumvents these limitations. We examined the efficacy of repeated embolization combined with systemically administered doxorubicin, the most common chemotherapeutic in TACE, or tirapazamine, a hypoxia-activated cytotoxic agent, in an ectopic xenograft model of HCC. Emboli were generated using acoustic droplet vaporization, the noninvasive focused ultrasound-mediated conversion of intravenously administered perfluorocarbon microdroplets into microbubbles. Gas embolization alone significantly reduced the Ki67 index and tumor viability (11.6 ± 6.71% non-necrotic vs 100% in control; p < 0.01) after 3 treatments, as assessed by histological analysis. Mice treated for three weeks exhibited significant tumor regression compared to control (23.8 ± 5.37% of initial volume vs 427 ± 49.7% in controls, p < 0.01), irrespective of the chosen chemotherapeutic agent. However, an additional three weeks of monitoring post-treatment elucidated a significant difference in the tumor recurrence rate, with combined gas embolization and doxorubicin resulting in the best treatment outcomes (60% complete regression). While doxorubicin administration resulted in significant cardiotoxicity (p < 0.01), it strongly interacted with the droplet shells, reducing the systemic dose by 11.4%. Overall, gas chemoembolization shows promise as a developmental therapy and merits further study in more complex tumor models.
PubMed: 32923844
DOI: 10.1063/5.0005329