Ispitivanje uticaja aloe emodina na ćelije melanoma B16 i A375 i njihovu osetljivost na citostatike i imunski odgovor
Evaluation of aloe emodin effect on B16 and A375 melanoma cells and their sensitivity to anticancer drugs and immune response
Докторанд
Radović, Julijana M.Ментор
Maksimović-Ivanić, DanijelaЧланови комисије
Kataranovski, MilenaMijatović, Sanja
Stošić-Grujičić, Stanislava
Božić, Biljana
Метаподаци
Приказ свих података о дисертацијиСажетак
Aloe emodin (AE) spada u biljne molekule antraciklinskog tipa koji zahvaljujući
reaktivnim grupama na atomima ugljenika benzenovih prstenova pokazuje izrazitu
reaktivnost i posledično široki spektar biološke aktivnosti poput baktericidnog,
fungicidnog, viricidnog, imunosupresivnog, antiinflamatornog, hepatoprotektivnog,
laksativnog i vazorelaksirajućeg delovanja. Istraživanja novijeg datuma stavljaju u žižu
interesovanja njegova antitumorska dejstva.
Ciljevi koji su postavljeni u ovoj tezi podrazumevali su utvrđivanje tumoricidnog delovanja
AE-a na ćelije mišjeg, B16 i humanog, A375 melanoma koje se inicijalno razlikuju u
redoks statusu i aktivnosti signalnih puteva uključenih u kancerogenezu. Uz uporednu
analizu unutarćelijskog odgovora pomenutih linija na tretman AE-om, ispitivan je i uticaja
AE-a na osetljivost melanoma na imunski odgovor usmeren protiv transformisane ćelije
kao i na efikasnost konvencionalne citostatske terapije.
AE je snažno inhibirao rast obe ćelijske linije posr...edstvom različitih mehanizama. U
slučaju A375 ćelija, AE je doveo do indukcije apoptoze zavisne od aktivnosti kaspaza uz
smanjenje nivoa antiapoptotskih proteina XIAP i Bcl-2. Suprotno, tretman AE-om je
indukovao ireverzibilnu diferencijaciju B16 ćelija u smeru primarnog fenotipa
manifestovanog povećanom ekspresijom enzima tirozinaze i naknadnom produkcijom
melanina. Opisana promena B16 ćelija bila je praćena brzom akumulacijom p53, ciklina D1
i D3. Ključni događaj u diferencijaciji B16 ćelija je, najverovatnije, povećana produkcija
H2O2 indukovana AE-om. U osnovi heterogenih ishoda tretmana istovetnim agensom je
recipročna regulacija aktivnosti ERK1/2 i Akt. Poseban značaj ima podatak da se apoptoza
pokrenuta AE-om u A375 ćelijama odvija u uslovima prekomerne aktivnosti Akt. Analiza
paralelnog tretmana ćelija melanoma AE-om i konvencionalnim citostaticima
(doksorubicin i paklitaksel) pokazala je da pomenuta supstanca umanjuje efikasnost
hemioterapije. Nekonzistentnost ishoda ko-tretmana AE-a i medijatora imunskog odgovora
iz familije TNF molekula ukazala je na kompleksnost uticaja mikrosredine na učinak AE-a.
U celini, rezultati ove doktorske disertacije pokazuju kako specifičnost ćelija melanoma
definiše mehanizam delovanja AE-a iako ne ugrožava njegov antitumorski potencijal. S
druge strane, opisani rezultati upozoravaju na opasnost kombinovanja biljnih preparata sa
konvencionalnim terapeuticima usled mogućeg neutrališućeg efekta.
Aloe emodin is an herbal antraquinone that, due to reactive groups on the carbon atoms of
benzene rings, posseses a strong reactivity and consequently shows a wide range of
biological activities such as antibacterial, antifungal, antiviral, diuretic,
immunosuppressive, anti-inflammatory, hepatoprotective, laxative and vasorelaxant.
Recent studies put the focus on its antitumor effects. The aim of this thesis was to
determine and evaluate antitumor activity of AE on two melanoma cell lines that initially
differs in redox status and activities of signaling pathways involved in carcinogenesis:
mouse melanoma B16, and human melanoma A375 cells. Together with comparative
analysis of the intracellular responses of two lines to the AE treatment, the impact of AE on
the sensitivity of melanoma to antitumor immune response as well as the efficiency of
conventional cytostatic therapy, were examined. AE decreased the growth of both cell lines through different mechanisms. In the case of
A375 cell...s, AE inducted caspase dependent apoptosis by reducing protein levels of
antiapoptotic molecules XIAP and Bcl-2. In contrast, treatment with AE promoted
irreversible differentiation of B16 cells towords its primary phenotype manifested through
increased expression of the tyrosinase and the subsequent production of melanin. Described
change in B16 cells was accompanied by a rapid accumulation of p53, cyclin D1 and D3.
Increased production of H2O2 triggered by AE is probably first in a line of events
responsible for induction of differentiation of B16 cells. Opposite regulation of two main
signaling pathways involved in cell proliferation, differentiation and death- MEK-ERK1/2
and PI3K-Akt in tested cell lines could be essential for different outcome of the treatment
with single agent. Furthermore, analysis of the parallel treatment of melanoma cells with
the AE and conventional cytostatics (doxorubicin and paclitaxel) showed that introduced
substance decreases the effectiveness of chemotherapy. Incoherent outcome of co-treatment
of AE and TNF, FasL or TRAIL, the most relevant mediators of nonspecific immune
response aginst tumor cells, points to the complexity of the influence of
microenvironmental factors to the effect of AE. In general, the results of this PhD thesis
show that cell specificity of melanomas defines the mechanism of AE action, while it does
not jeopardize its anticancer potential. On the other hand, presented results point to a
danger of combining herbal medicines with conventional therapeutics due to their possible
neutralizing effects.