Nonetheless, because of limitations in dose availability, rather than used as single agents polyphenols are better valuable as radio-or chemosensitizers in combination with other chemotherapeutic agents. The utility has been mainly demonstrated in solid tumourderived cell models and in combination with classic DNA-damaging agents, but there is less information in leukaemia cell models, and almost no information in combination with the above-mentioned mitochondriotoxic drugs. Apoptosis and necrosis are the two classic forms of cell death. Necrosis is a nonregulated form of death derived from the rapid loss of cell homeostasis, upon severe cell injury. Apoptosis, is a a regulated form of death, which may be executed following two pathways, namely the death-receptor (“extrinsic”) pathway, and the mitochondrial (“intrinsic”) pathway. The later one is normally produced by most anti-cancer agents, and likely by mitonchodria-targeting drugs. The intrinsic pathway is initiated by the permeabilization of the outer mitchondria membrane (mOMP), the release of mitochondria-located apoptogenic factors, ending in the activation of the caspase- 9/caspase-3 pathway. It is normally associated to pore opening at the mitochondrial inner membrane (mIMP), and hence to dissipation of intermembrane potential (m). In addition, it is regulated by multiple signalling factors, including: (a) Oxidative stress, which, depending on the intensity, may cause apoptosis or necrosis, and either produce cell death per se or facilitate the generation of cell death by other agents. Oxidative stress may be evidenced by the over-accumulation of reactive oxigen species (ROS), and/or the loss of anti-oxidant factors (e.g., reduced glutatione, GSH). (b) Alterations in protein kinase signalling pathways, such as the oxidant-sensitive, normally proapoptotic, p38-MAPK and JNK kinases, or the normally defensive MEK/ERK and PI3K/Akt pathways. (c) Alterations in the activity of the NF-κB transcription factor, which in general operates as a defensive factor. (d) Alterations in the expression heatshock proteins (HSPs), a complex family of chaperones, some of which (as Hsp-70) functioning as an anti-apoptotic factors. Objectives The general purpose of this thesis was to investigate the capacity of selected polyphenols, with particular interest on curcumin and resveratrol, to potentiate the cytoreductive capacity of ATO and lonidamine. For this purpose we analyze cell cycle, cell death (necrosis and apoptosis), mitochondrial dysfunction (mIMP, apoptogenic protein release) and some regulatory factors (oxidative stress, protein kinases, NF-κB, Hsp-70) which might explain the apoptotic response. Both the mitocondriotoxic drugs and phenolic agents will be normally used at sub-cytotoxic concentrations, wihin or close to the range of pharmacologically useful doses. As cell models we use the human acute myeloid (promonocytic) leukaemia U-937 cell line, and for comparison other myeloid and lymphoid leukemia cells. Also for comparison, some DNA-targeting drugs will be used instead of the mitochondriotoxic drugs.

Introduction Mitochondria-targeting drugs (“mitochondriotoxics”, or “mitocans”) represent an family of anticancer agents the toxicity of which is caused by direct interaction with mitochondrial structures (e.g., permeability transition pore (mPTP), respiratory chain complexes, mtDNA…etc). This enables these agents to overcome certain forms of drug resistance arising when other chemotherapeutic agents (e.g., DNA-targeting drugs) are used. In the present work we have employed arsenic trioxide (ATO, Trisenox) and lonidamine, the main (but not only) target of them being some proteins which form part or are associated to the mPTP – adenine nucleotide translocator and/or hexokinase II-. ATO is clinically used against acute promyelocytic leukaemia, where it promotes growth arrest and terminal differentiation due to disruption of the oncogenic fusion protein PML-RARα, but is also potentially useful against other haematologic diseases via apoptosis induction. Lonidamine, formerly used as anti-spermiogenic agent, is a safe, non toxic agent incorporated in clinical protocols against solid tumours, but also potentially useful in leukaemia. Nevertheless the efficacy of these agents is normally low in monotherapy, and hence the generation of sensitizing strategies is required. Natural polyphenols represent a family of hundreds of compounds present in the vegetal kingdom. Upon long-term administration at low doses (e.g., in the diet) polyphenols are antioxidants and protective agents, preventing inflammation, aging, and cancer initiation and progression. On the other hand, at high but still pharmacologically achievable concentrations, polyphenols may in some circumstance behave as prooxidants, causing cell cycle impairment, cell death, and elimination of mature tumours.

Proyecto SAF2010-20256 del MINECO y contrato (2008-2012) de la CAM

Tesis de Gloria Pilar Simón García de Mora. 242 p.-71 fig.-1 tab.

Peer reviewed