Anticancer therapeutic potential of Mn porphyrin/ascorbate system

• Type of Material: Article
• Authors: Artak Tovmasyan, Duke University; Romulo S. Sampaio, Duke University; Mary-Keara Boss, North Carolina State University; Jacqueline C. Bueno-Janice, Duke University; Bader H. Bader, Kuwait University; Milini Thomas, Kuwait University; Julio S. Reboucas, Universidade Federal da Paraiba; Michael Orr, Emory University; Joshua D. Chandler, Emory University; Young-Mi Go Kang, Emory University; Dean Jones, Emory University; Talaignair N. Venkatraman, Duke University; Sinisa Haberle, Duke University; Natalia Kyui, Bank of Canada; Christopher Lascola, Duke University; Mark W. Dewhirst, Duke University; Ivan Spasojevic, Duke University; Ludmil Benov, Kuwait University; Ines Batinic-Haberle, Duke University
• Language: English
• Date: 2015-12-01
• Publisher: Elsevier
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © 2015 Elsevier Inc. All rights reserved.
• License: Creative Commons Attribution 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.1016/j.freeradbiomed.2015.10.416
• Title of Journal or Parent Work: Free Radical Biology and Medicine
• ISSN: 0891-5849
• Volume: 89
• Start Page: 1231
• End Page: 1247
• Grant/Funding Information: JSR, JCBJ and RSP acknowledge CNPq and CAPES from Brazil. LB, BHB and MT acknowledge support by grants MB02/12, YM04/14 and SRUL02/13 from Kuwait University.; BH, AT and IS acknowledge NIH 1R03-NS082704-01, NIH U19AI067798, and BioMimetix JVLLC (USA). AT acknowledges mini-fellowship award from SFRBM. IS is grateful for the support to 5-P30-CA14236-29.; DJ and YG acknowledge NIH R01 ES023485 and R21 ES 025632.
• Keywords: Biochemistry & Molecular Biology; Cancer cells; Endocrinology & Metabolism; Mn porphyrin; PANCREATIC-CANCER; Life Sciences & Biomedicine; Cytotoxicity; Tumor growth suppression; HYDROGEN-PEROXIDE; MnTE-2-PyP; Ascorbate; Hydrogen peroxide; SOD MIMICS; TUMOR PROGRESSION; MANGANESE SUPEROXIDE-DISMUTASE; LYMPHOMA-CELLS; Science & Technology; Catalysis; OXIDATIVE STRESS; BREAST-CANCER CELLS; PHARMACOLOGICAL ASCORBATE; N-ALKYLPYRIDYLPORPHYRINS; SOD mimics
• Research Categories: Health Sciences, Oncology; Health Sciences, Radiology

Abstract

Ascorbate (Asc) as a single agent suppressed growth of several tumor cell lines in a mouse model. It has been tested in a Phase I Clinical Trial on pancreatic cancer patients where it exhibited no toxicity to normal tissue yet was of only marginal efficacy. The mechanism of its anticancer effect was attributed to the production of tumoricidal hydrogen peroxide (H2O2) during ascorbate oxidation catalyzed by endogenous metalloproteins. The amount of H2O2 could be maximized with exogenous catalyst that has optimized properties for such function and is localized within tumor. Herein we studied 14 Mn porphyrins (MnPs) which differ vastly with regards to their redox properties, charge, size/bulkiness and lipophilicity. Such properties affect the in vitro and in vivo ability of MnPs (i) to catalyze ascorbate oxidation resulting in the production of H2O2; (ii) to subsequently employ H2O2 in the catalysis of signaling proteins oxidations affecting cellular survival pathways; and (iii) to accumulate at site(s) of interest. The metal-centered reduction potential of MnPs studied, E1/2 of MnIIIP/MnIIP redox couple, ranged from -200 to +350 mV vs NHE. Anionic and cationic, hydrophilic and lipophilic as well as short- and long-chained and bulky compounds were explored. Their ability to catalyze ascorbate oxidation, and in turn cytotoxic H2O2 production, was explored via spectrophotometric and electrochemical means. Bell-shape structure-activity relationship (SAR) was found between the initial rate for the catalysis of ascorbate oxidation, vo(Asc)ox and E1/2, identifying cationic Mn(III) N-substituted pyridylporphyrins with E1/2>0 mV vs NHE as efficient catalysts for ascorbate oxidation. The anticancer potential of MnPs/Asc system was subsequently tested in cellular (human MCF-7, MDA-MB-231 and mouse 4T1) and animal models of breast cancer. At the concentrations where ascorbate (1 mM) and MnPs (1 or 5 μM) alone did not trigger any alteration in cell viability, combined treatment suppressed cell viability up to 95%. No toxicity was observed with normal human breast epithelial HBL-100 cells. Bell-shape relationship, essentially identical to vo(Asc)ox vs E1/2, was also demonstrated between MnP/Asc-controlled cytotoxicity and E1/2-controlled vo(Asc)ox. Magnetic resonance imaging studies were conducted to explore the impact of ascorbate on T1-relaxivity. The impact of MnP/Asc on intracellular thiols and on GSH/GSSG and Cys/CySS ratios in 4T1 cells was assessed and cellular reduction potentials were calculated. The data indicate a significant increase in cellular oxidative stress induced by MnP/Asc. Based on vo(Asc)ox vs E1/2 relationships and cellular toxicity, MnTE-2-PyP5+ was identified as the best catalyst among MnPs studied. Asc and MnTE-2-PyP5+ were thus tested in a 4T1 mammary mouse flank tumor model. The combination of ascorbate (4 g/kg) and MnTE-2-PyP5+ (0.2 mg/kg) showed significant suppression of tumor growth relative to either MnTE-2-PyP5+ or ascorbate alone. About 7-fold higher accumulation of MnTE-2-PyP5+ in tumor vs normal tissue was found to contribute largely to the anticancer effect.