No description available.

No description available.

No description available.

Thesis (M. Phil.)--University of Hong Kong, 1999. / Includes bibliographical references (leaves 132-149).

Thesis (doctoral)--Lund University, 1996. / Added t.p. with thesis statement inserted.

Thesis (doctoral)--Lund University, 1996. / Added t.p. with thesis statement inserted.

published_or_final_version / Paediatrics / Master / Master of Philosophy

No description available.

Dans le traitement des cancers des voies aérodigestives supérieures (VADS), une approche biologique par des anti-EGFR (Epidermal Growth Factor Receptor) comme le cetuximab (Erbitux®) a récemment été proposée. Le cetuximab est un anticorps monoclonal chimérique qui se lie spécifiquement au domaine extracellulaire de l’EGFR, régulateur central de la prolifération et de la différenciation dans les cancers. Par cette liaison, le cetuximab entre en compétition avec les ligands du récepteur et empêche son activation, induit son internalisation et bloque la transduction du signal vers les voies de signalisation en aval. Même si cette approche thérapeutique est rationnelle puisque l’EGFR est surexprimé dans la plupart des cancers et notamment dans les cancers des VADS, certains types de cancers présentent une résistance à cet anticorps. Parmi les molécules qui ciblent EGFR il existe également des inhibiteurs de l’activité tyrosine kinase intracellulaire de l’EGFR comme le gefitinib (Iressa®), mais ce dernier n’est actuellement pas prescrit dans le traitement des cancers des VADS.Le but de notre travail a été d’étudier les mécanismes de résistance au cetuximab dans des lignées cellulaires de cancers des VADS puis de proposer des associations thérapeutiques pouvant pallier à cette résistance.Nous avons choisi deux lignées cellulaires de cancers des VADS, CAL33 et SQ20B en comparaison à la lignée épidermoïde A431 sur exprimant EGFR et sensible au cetuximab. Nous avons pu mettre en évidence que CAL33 et SQ20B étaient résistantes au cetuximab mais de manière surprenante sensibles au gefitinib. Nous avons montré que l’absence d’inhibition de phosphorylation d’AKT et qu’une altération de l’internalisation de l’EGFR par le cetuximab étaient responsables en partie de la résistance au cetuximab dans ces modèles cellulaires.Afin de pallier à cette résistance nous avons alors étudié les conséquences biologiques de l’association du cetuximab avec (i) des inhibiteurs de la voie PI3K/AKT par différentes approches et avec (ii) les radiations ionisantes. Dans un premier temps, nous avons étudié l’influence de l’inhibition de la voie AKT par un inhibiteur de PI3K ou un siRNA ciblant AKT. Nous avons démontré que l’inhibition de la phosphorylation d’AKT par l’inhibiteur LY294002 sensibilisait au cetuximab la lignée CAL33 porteuse d’une mutation activatrice du gène PIK3CA codant pour la sous-unité catalytique p110 de la protéine PI3K. Nous avons montré que la persistance de l’activation d’AKT dans la lignée CAL33 prévenait l’effet anti tumoral du cetuximab, tandis que la résistance au cetuximab dans la lignée SQ20B ne semblait pas dépendante de la voie AKT.Une association de traitement du cetuximab avec les radiations ionisantes est déjà proposée en clinique dans le traitement des cancers des VADS. Nous avons donc dans un second temps déterminé les effets de cette association de traitement dans les lignées SQ20B et CAL33 respectivement sauvage et mutée dans la voie de signalisation AKT et dans la lignée contrôle A431. Nous avons montré que l’association du cetuximab aux radiations ionisantes potentialisait l’effet du cetuximab sur l’inhibition de prolifération de la lignée A431 alors que nous n’avons observé aucune potentialisation de l’effet du cetuximab sur la prolifération dans les lignées résistantes CAL33 et SQ20B. Dans ce travail, nous montrons que la voie AKT apparaît donc comme un élément central dans la réponse au cetuximab dans la lignée CAL33 et que l’association du cetuximab avec un inhibiteur de la voie PI3K/AKT pourrait être une bonne option thérapeutique dans le traitement des cancers des VADS mutés pour PIK3CA. / In the treatment of HNSCC (Head and Neck Squamous Cell Carcinoma), a biological approach by anti-EGFR (Epidermal Growth Factor Receptor) such as cetuximab (Erbitux ®) has been recently proposed. Cetuximab is a chimeric monoclonal antibody that specifically binds the extracellular domain of EGFR, a central regulator of proliferation and differentiation in cancer. For this binding, cetuximab is in competition with EGFR ligands, prevents receptor activation, induces its internalization and blocks the transduction and the downstream signaling pathways. Although this therapeutic approach is rational because EGFR is overexpressed in most of cancers, some cancers are resistant to this antibody. Among the molecules that target EGFR, there are also inhibitors of intracellular tyrosine kinase activity of EGFR such as gefitinib (Iressa ®), but these molecules are not currently used for the treatment of HNSCC cancers. The aim of our study was to characterize resistance mechanisms to cetuximab in a panel of HNSCC cell lines and to propose the treatment combination able to overcome this resistance.We chose two cell lines of HNSCC, CAL33 and SQ20B in comparison with A431 cell line which over express EGFR and which is sensitive to cetuximab. We had shown that CAL33 and SQ20B were resistant to cetuximab but sensitive to gefitinib. This study showed that the absence of inhibition of phosphorylation of AKT by cetuximab and the alteration of the EGFR internalization were responsible in part of the cetuximab resistance in these cell models. Then we studied the biological effects of the combination of cetuximab with (i) inhibition of PI3K/AKT by different approaches and (ii) ionizing radiation.We initially studied the influence of inhibition of AKT pathway by a PI3K inhibitor or siRNA targeting Akt. We demonstrated that inhibition of AKT phosphorylation by LY294002 sensitized CAL33 to cetuximab. This cell line carries an activating mutation of the PIK3CA gene encoding the catalytic subunit p110 of PI3K protein. We have shown that persistent activation of AKT in line CAL33 warned antitumor effect of cetuximab, while resistance to cetuximab in line SQ20B did not seem dependent on the AKT pathway. A combination therapy of cetuximab with ionizing radiation is already proposed in the clinical treatment of these cancers. We therefore determined n the second step, the effects of this combination treatment in lines CAL33 and SQ20B respectively in the wild and mutant AKT signaling pathway and the control line A431. We have shown that the combination of cetuximab to ionizing radiation potentiated the effect of cetuximab on the inhibition of proliferation of line A431, whereas we observed no potentiation of the effect of cetuximab on the proliferation in the resistant lines CAL33 and SQ20B. In this work, we show that the AKT pathway is therefore a central element in the response to cetuximab in line CAL33 and the combination of cetuximab with an inhibitor of the PI3K/AKT pathway might be a good therapeutic option in the treatment of these cancers with a PIK3CA mutation.

在哺乳動物中，表皮生長因子(EGF)家族及其同源受體(EGFR)家族是卵泡生成的重要調節者。表皮生長因子受體信號轉導不但在促黃體激素誘導的卵母細胞成熟和排卵中是必不可少的，而且也通過與促性腺激素互相作用而影響卵泡的類固醇生產和生存。表皮生長因子對卵母細胞成熟的促進作用，也保存在金魚和斑馬魚等硬骨魚類。然而，在硬骨魚類中，有關表皮生長因子家族功能的知識仍然是非常有限的。在本研究中，我們的目的如下: (1)試圖找出那些表皮生長因子受體信號轉導路徑傳達表皮生長因子對卵母細胞成熟; (2)表皮生長因子受體和促黃體激素的潛在關係; (3)表皮生長因子和其他身體激素之間的相互作用。所有發現都可以幫助我們更系統地更了解表皮生長因子在斑馬魚卵泡發育中的作用。 / 我們實驗室先前的研究表明，表皮生長因子促進斑馬魚卵母細胞的成熟是通過激活素系統，但不知道其通過什麼細胞內信號轉導路徑調節激活素系統的表達。在這裡，我們使用斑馬魚卵泡培養和藥理抑製劑來研究幾個熟知的表皮生長因子受體轉導信號在表皮生長因子刺激激活素亞基表達的作用。我們發現，有絲分裂原活化蛋白質激酶3/1(MAPK3/1)，p38有絲分裂原活化蛋白質激酶 (p38MAPK)，蛋白激酶C(PKC)和蛋白激酶A(PKA)在抑制素βAA(inhbaa)和抑制素βB(inhbb)亞基表達中起到刺激作用，但對抑制素βAB(inhbab)的表達起抑制作用。另一方面，只有磷脂酰肌醇3激酶(PI3K)調節表皮生長因子對抑制素βB的表達，而它沒有對抑制素βAA和抑制素βB亞基的表達起任何淨影響。 / 除了表皮生長因子在斑馬魚卵巢自己產生的作用， 探討表皮生長因子和其他因素之間的相互作用也是很重要的，因為卵泡是由多種激素和彼此互動的因素控制。 / 在雌性哺乳動物的生殖中，表皮生長因子受體轉導促黃體激素的作用是十分重要的，這使我們很感興趣研究這種情況是否在斑馬魚一樣發生。 和哺乳動物不同，人绒毛膜促性腺激素(hCG)沒有激活斑馬魚表皮生長因子受體。另一方面，和哺乳動物相似，人绒毛膜促性腺激素誘導有絲分裂原活化蛋白質激酶3 / 1在斑馬魚卵泡細胞中的磷酸化，但它是通過蛋白激酶A不是表皮生長因子受體的。此外，在雌性哺乳動物中，人绒毛膜促性腺激素對有絲分裂原活化蛋白質激酶3 / 1的作用是使卵母細胞成熟, 但這作用可能不在斑馬魚中發生，因為它負調控抑制素βAB的表達。 / 表皮生長因子在斑馬魚卵巢的另一個有趣地方是胰島素的存在改變它對調節芳香化酶表達中的作用。表皮生長因子對芳香化酶表達起輕微的抑制效果，但它提高了胰島素對芳香化酶表達的刺激作用。此外，胰島素，促性腺激素和表皮生長因子一起的時候，更加增加了芳香化酶的表達。然而，表皮生長因子抑制佛司可林(FK)對芳香化酶和抑制素αmRNA表達的刺激作用。 / 兩者合計，我們提供了一些基本但重要的信息有關表皮生長因子及其受體在斑馬魚卵巢的功能，包括每個表皮生長因子受體信號轉導信號路徑的分子機制及它們參與調節激活素亞基的表達；表皮生長因子，促黃體激素和胰島素之間的相互作用。這些信息可以讓我們進一步探討表皮生長因子在斑馬魚卵泡以及其他脊椎動物的重要角色。 / In mammals, epidermal growth factor (EGF) family and its cognate receptor (EGFR) family are the key regulators of folliculogenesis. EGFR signaling not only is indispensable in luteinizing hormone-induced oocyte maturation and ovulation, but also influences steroidogenesis and survival of follicles via interacting with gonadotropins. The positive role of EGF on oocyte maturation is shown to conserve in teleosts such as goldfish and zebrafish. However, the knowledge about the functions of EGF family in teleosts is still very limited. In the present study, we sought to find out the EGFR signaling pathways that mediate the action of EGF on oocyte maturation, the potential relationship of EGFR and LH and the interaction between EGF and systemic hormones. All these findings help us to understand more about the role of EGF in zebrafish folliculogenesis in a more systematic manner. / Our lab previously demonstrate that EGF promotes oocyte maturation in zebrafish via activin system but the contribution of the EGFR signaling pathways in regulating the activin system is not known. Here, we investigated the role of several well-known EGFR signaling cascades in EGF-stimulated activin subunit expression using cultured zebrafish follicle and pharmacological inhibitors. We found that MAPK3/1, p38 MAPK, PKC and PKA played stimulatory role in the expression of inhbaa and inhbb but suppressive role in inhbab. On the other hand, only PI3K was found to mediate the action of EGF on the expression of inhbab while it did not have any net effect on the expression of inhbaa and inhbb. / Apart from its own action in zebrafish ovary, it is essential to investigate the interaction or cross-talk between EGF and other factors because folliculogenesis is controlled by many hormones and factors interacting with each other. / The vital mediatory action of EGFR on LH in female reproduction of mammals was led us to ask whether the situation is the same as in zebrafish. However, unlike in mammals, hCG did not transactivate zebrafish EGFR. On the other hand, similar to mammals, hCG did induce MAPK3/1 phosphorylation in zebrafish follicle cells but it was via PKA dependent but not EGFR dependent manner. Moreover, hCG-induced MAPK3/1 activation is involved in oocyte maturation in mammals while in zebrafish, the function of this activation might not be the same as in mammals because it negatively regulated the expression of inhbab. / Another interesting issue about EGF in zebrafish ovary is that its role in regulating the expression of aromatase in response to insulin. EGF alone has slight suppressive effect on aromatase expression but it boosted the stimulatory effect of insulin on aromatase expression. Furthermore, insulin, hCG and EGF together even increased the expression of aromatase. However, EGF always suppressed the stimulatory effect of forskolin on aromatase and inhibin alpha mRNA expression. / Taken together, we provided some fundamental but important information about the function of EGF and its receptor in zebrafish ovary by elucidating the molecular mechanism of each EGFR signaling pathways involved in regulating the expression of activins subunits, the interaction between EGF, LH and insulin. All these studies not only allow us to further explore the elegant roles of EGF in zebrafish folliculogenesis, but also in other vertebrates in the future. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Chung, Chi Kin. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 116-132). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Abstract in English --- p.I / Abstract in Chinese --- p.III / Acknowledge --- p.V / Table of contents --- p.VI / List of figures and tables --- p.XI / Symbols and abbreviations --- p.XVI / Chapter Chapter 1 --- General Introduction / Chapter 1.1 --- Folliculogenesis --- p.1 / Chapter 1.1.1 --- In mammals --- p.1 / Chapter 1.1.2 --- In teleosts --- p.2 / Chapter 1.1.2.1 --- Vitellogenesis --- p.3 / Chapter 1.1.2.2 --- Oocyte maturation --- p.3 / Chapter 1.2 --- Epidermal growth factor receptor family --- p.4 / Chapter 1.2.1 --- Structure --- p.4 / Chapter 1.2.2 --- Signal transduction pathways --- p.5 / Chapter 1.2.2.1 --- MEK1/2-MAPK3/1 pathway --- p.6 / Chapter 1.2.2.2 --- p38 MAPK pathway --- p.6 / Chapter 1.2.2.3 --- PI3K pathway --- p.7 / Chapter 1.2.2.4 --- PKC pathway --- p.7 / Chapter 1.2.3 --- Reproductive function of EGFR signaling --- p.8 / Chapter 1.2.3.1 --- In mammals - mediator of luteinizing hormone --- p.9 / Chapter 1.2.3.2 --- In teleosts --- p.10 / Chapter 1.3 --- Interaction of EGF family with other hormones --- p.11 / Chapter 1.4 --- Objectives of the present study --- p.12 / Chapter Chapter 2 --- The Involvement of Diverse EGFR Signaling Pathways in Regulating the Expression of Activin Subunits in Zebrafish / Chapter 2.1 --- Introduction --- p.15 / Chapter 2.2 --- Materials and methods --- p.16 / Chapter 2.2.1 --- Animals and chemicals --- p.16 / Chapter 2.2.2 --- Primary zebrafish follicle cell culture --- p.17 / Chapter 2.2.3 --- Follicle incubation --- p.18 / Chapter 2.2.4 --- Immunoblotting --- p.18 / Chapter 2.2.5 --- Immunohistochemistry --- p.18 / Chapter 2.2.6 --- RNA extraction and reverse transcription --- p.19 / Chapter 2.2.7 --- Real-time quantitative polymerase chain reaction (qPCR) --- p.20 / Chapter 2.2.8 --- Data analysis --- p.20 / Chapter 2.3 --- Results / Chapter 2.3.1 --- Recombinant human EGF up-regulated the expression of all known activin subunits in zebrafish ovary via specific activation of zebrafish EGFR --- p.21 / Chapter 2.3.2 --- MAPK3/1, p38 MAPK, PKC and PKA played similar roles in regulating EGF-stimulated expression of activin subunits --- p.22 / Chapter 2.3.3 --- PI3K pathway was involved in EGF-stuimulated expression of inhbab but not inhbaa and inhbb in zebrafish follicle cells --- p.24 / Chapter 2.3.4 --- MAPK3/1, p38 MAPK and PKC all together were sufficient to mediate the action of EGF on the expression of all activin subunits in zebrafish follicle cells --- p.24 / Chapter 2.3.5 --- Signaling cross-talk between PKA, MAPK3/1 and PI3K in zebrafish follicle cells --- p.25 / Chapter 2.3.6 --- EGFR signaling in the intact zebrafish follicles --- p.25 / Chapter 2.3.7 --- EGF and hCG togher up-regulatory the expression of inhbab synergistically in zebrafish follicle cells --- p.25 / Chapter 2.4 --- Discussion --- p.26 / Chapter Chapter 3 --- hCG-induced MAPK3/1 Phosphorylation in the Zebrafish Follicle Cells is Independent of EGFR Activation / Chapter 3.1 --- Introduction --- p.52 / Chapter 3.2 --- Materials and methods --- p.54 / Chapter 3.2.1 --- Animals and chemicals --- p.54 / Chapter 3.2.2 --- Primary zebrafish follicle cell culture --- p.54 / Chapter 3.2.3 --- Immunoblotting --- p.54 / Chapter 3.2.4 --- RNA extraction and reverse transcription --- p.54 / Chapter 3.2.5 --- Real-time quantitative polymerase chain reaction (qPCR) --- p.54 / Chapter 3.2.6 --- Data analysis --- p.54 / Chapter 3.3 --- Results --- p.54 / Chapter 3.3.1 --- hCG stimulated MAPK3/1 phosphorylation in zebrafish follicle cells --- p.54 / Chapter 3.3.2 --- hCG-induced MAPK3/1 phosphorylation was PKA-dependent but EGFR-independent --- p.55 / Chapter 3.3.3 --- Role of hCG-induced MAPK3/1 activation in regulating the expression of activin subunits --- p.55 / Chapter 3.4 --- Discussion --- p.56 / Chapter Chapter 4 --- Interaction between EGF, hCG and insulin on the Expression of inha and cyp19a1a in Zebrafish Follicles - a Potential Link between Nutrition and Reproduction / Chapter 4.1 --- Introduction --- p.67 / Chapter 4.2 --- Materials and chemicals --- p.69 / Chapter 4.2.1 --- Animals and chemicals --- p.69 / Chapter 4.2.2 --- Primary zebrafish follicle cell culture --- p.69 / Chapter 4.2.3 --- Follicle incubation --- p.69 / Chapter 4.2.4 --- Immunhistochemistry --- p.69 / Chapter 4.2.5 --- RNA extraction and reverse transcription --- p.70 / Chapter 4.2.6 --- Real-time quantitative polymerase chain reaction (qPCR) --- p.70 / Chapter 4.2.7 --- Data analysis --- p.70 / Chapter 4.3 --- Results --- p.70 / Chapter 4.3.1 --- Recombinant human insulin up-regulated the expression of inha and cyp19a1a in zebrafish follicles --- p.70 / Chapter 4.3.2 --- Interaction between insulin and hCG on the expression of cyp19a1a and inha in intact zebrafish follicles and follicle cells --- p.71 / Chapter 4.3.3 --- Interaction of cAMP pathway and insulin in the regulation of cyp19a1a and inha in zebrafish follicle and zebrafish follicle cells --- p.72 / Chapter 4.3.4 --- Differential effect of EGF on insulin, hCG and FK-regulated expression of cyp19a1a and inha in zebrafish follicles and follicle cells --- p.72 / Chapter 4.3.5 --- Insulin activated Akt pathway in both follicle cells and oocyte in zebrafish follicles --- p.73 / Chapter 4.4 --- Discussion --- p.73 / Chapter Chapter 5 --- General Discussion --- p.96 / Chapter Appendix --- Chapter Phosphorylation of MAPK3/1 in the Follicle in Vivo Evidence for Roles of MAPK3/1 in the Two Compartments of Follicles during Final Maturation and Ovulation / Introduction --- p.104 / Materials and methods --- p.105 / Animals and chemicals --- p.105 / Immunohistochemistry --- p.105 / Results --- p.105 / Discussion --- p.106 / References --- p.116