Mémoires de Fin d’Etudes
Etablissement
Université de Biskra - Mohamed Khider
Affiliation
Département des Sciences Nature et de la vie
Auteur
BELLEBCIR, Leila
Directeur de thèse
Abidli Nacira (أستاذ محاضر)
Filière
Biologie
Diplôme
Doctorat
Titre
study on biological effects of some medicinal Plant Extracts or their compounds on cancer cells and its effects on anticancer drugs toxicity
Mots clés
Aristoloche , Astragal, métabolisme secondaire, étude phytochimique et pharmalogique
Résumé
The Problematic: Every year, millions of people are diagnosed with cancer, leading to death in a majority of the cases (1). Cancer is a multi-stage phenomenon including initiation, fixation of mutation, transformation, promotion, proliferation, progression, and cell heterogeneity, respectively (2, 3). The treatment of choice remains mainly surgical resection, radiotherapy, and chemotherapy (4, 5). For many years, the cytotoxic actions of the chemotherapeutic drugs were ascribed solely to their ability to induce genotoxic death.However, there were accumulating evidences that these agents exert their cytotoxic effects mainly by inducing apoptosis in tumor cells. Impairment of apoptosis is known to be related to cell immortality and carcinogenesis and the induction of apoptosis in neoplastic cells, therefore, is vital in cancer treatment. The chemotherapeutic drugs that have been observed to induce apoptosis in vitro include etoposide, camptothecin, VM26, vincristine, cis-platinum, cyclophosphamide, paclitaxel, 5- fluorouracil and doxorubicin (7, 8, 9, 10, 11). In accordance with these in vitro studies, other studies also provide evidences that chemotherapeutic agents induce apoptotic tumor cell death in vivo. Experimental studies of murine tumors have demonstrated that cis-paltinum, cyclophosphamide and other chemotherapeutic agents induced apoptosis in various tumors in vivo (12). Several clinical studies have also shown that chemotherapy triggers apoptotic cell death in patients undergoing chemotherapy (13). There has been growing interest in naturally occurring compounds with anti-cancer potential (14).Cytotoxic substances derived from plants (e.g. vinca alkaloids or paclitaxel (Taxol)) are often used in oncology as highly potent drugs and/or serve as model for synthetic compounds (15). Thymoquinone (TQ) has been shown to exert anti-neoplastic effects. Nevertheless, TQ is known to induce apoptosis by p53-dependent and p53-independent pathways in cancer cell lines. Growth inhibition is associated with induction of cell cycle arrest (14). Injury to nontargeted tissues in chemotherapy often complicates cancer treatment by limiting therapeutic dosages of anticancer drugs and by impairing the quality of life of patients during and after treatment. It is known that many plant extracts have plenty of the molecules witch is reasonable to investigate plants for their capacity to prevent the toxic potency of chemotherapy toxicit . Therefore, the aim of this study were to evaluate the plant extracts cytotoxic properties and to determine the possible mechanisms of apoptosis elicited by the plant extracts on cancer cells( relation ship activity / structure ) and their effects on anticancer drug toxicity.
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