THE NATURAL FLAVONOID LUTEOLIN INDUCES APOPTOSIS IN COLON CANCER CELLS BY DYSREGULATING THE SPHINGOLIPID RHEOSTAT
Tesi di Dottorato
Data di Pubblicazione:
2014
Citazione:
THE NATURAL FLAVONOID LUTEOLIN INDUCES APOPTOSIS IN COLON CANCER CELLS BY DYSREGULATING THE SPHINGOLIPID RHEOSTAT / L. Abdel Hadi ; docente guida: L. Riboni ; coordinatore: F. Bonomi. DIPARTIMENTO DI BIOTECNOLOGIE MEDICHE E MEDICINA TRASLAZIONALE, 2014 Feb 27. 26. ciclo, Anno Accademico 2013. [10.13130/abdel-hadi-loubna_phd2014-02-27].
Abstract:
Colorectal cancer is one of the most common malignancies and a leading cause of cancer death in the world. More powerful and safer therapeutic approaches are urgently needed to reduce mortality and garner better curative effects. In this regard, dietary supplements capable of preventing carcinogenesis and inhibiting the growth of colon carcinoma cells have generated intense interest. Luteolin (LU), a common dietary flavonoids, has emerged as a powerful anticancer agents able to sensitize different cancer cells, including colon cancer ones, to therapeutic-induced cytotoxicity. However, the molecular mechanisms underlying LU effects in colon cancer are largely unknown.
Sphingolipids have critical functions as signaling molecules. In particular, Ceramide (Cer) and Sphingosine-1-phosphate (S1P) are involved as key antagonist mediators in regulating crucial cell responses such as proliferation and apoptosis. Cer can act as a second messenger, and, by activating a variety of signaling pathways, is able to promote growth arrest, apoptosis, or cell differentiation. To the opposite, the sphingoid mediator S1P can act as a potent mitogen and survival factor for a variety of cell types. These two lipids together form the “sphingolipid rheostat” regulating the balance between cell growth and cell death.
The objective of our study was to investigate the effects and the molecular mechanisms of LU in colon cancer, focusing on the role of the bioactive sphingoid molecules Cer and S1P. To this purpose, we used the Caco-2 cell line, obtained from a human colon adenocarcinoma, as cell model of both colon cancer cells, and differentiated intestinal enterocytes. Indeed, in long-term culture, these cells undergo a spontaneous differentiation into polarized cells, representing so far the best available in vitro model of absorptive enterocytes. These two models might thus allow to distinguish the potential LU effects on colon cancer cells in comparison to their healthy counterparts.
At first, we characterized the morphological and biochemical features of both models. We found that Caco-2 cell differentiation was accompanied by the formation of “domes” across the monolayer, known as characteristic structures of differentiated cells, and indicative of their property of absorptive epithelium. In addition, the activity of the alkaline phosphatase, a membrane-associated hydrolase was found significantly increased in differentiated Caco-2 cells compared to the tumoural cancer ones. Furthermore, we found that Caco-2 differentiation was associated with a reduction of the phospholipids/protein ratio, and whereas phosphatidylcholine was the most abundant phospholipid species of tumoural cells, phosphatidylethanolamine prevailed in the differentiated ones. Moreover, phosphatidylethanolamine plasmalogen, a quantitative relevant species in the cancer cells, exhibited a marked decrease with intestinal differentiation.
As far as the sphingolipid composition concerns, we first demonstrated that Caco-2 differentiation was associated to an increase in the total amount of sphingolipids, including Sphingomyelin (SM), the major component and precursor of both Cer and S1P, and above all ceramide. Since the SM hydrolysis, triggered by Sphingomyelinases (SMases), has been implicated in colon tumourigenesis, we then evaluated whether changes in the activity of the known different SMases (the neutral (N-SMase) and alkaline (Alk-SMase) enzymes) occur with cell differentiation. We found that the Alk-SMase activity which was barely detectable in tumoural cancer cells, significantly increased in differentiated ones. The high level of this enzyme is consistent with its presence in the apical brush border, characteristic of intestinal cells. Interestingly a significant inc
Tipologia IRIS:
Tesi di dottorato
Keywords:
colorectal cancer ; Luteolin ; ceramide ; sphingosine-1-phosphate ; sphingolipid rheostat ; apoptosis ; ceramide traffic
Elenco autori:
L. ABDEL HADI
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