ABSTRACT
Title
Botanicals used as food supplements interfering with EphA2-ephrinA1 system: a screening study
Authors
C. Giorgio1, I. Hassan Mohamed1, R. Bruni2, L. Flammini1, E. Barocelli1, A. Guerrini3, S. Bertoni1, M. Tognolini1.
1 Dipartimento di Scienze Farmacologiche, Biologiche e Chimiche Applicate, Università di Parma, Italy
2 Dipartimento di Biologia Evolutiva e Funzionale, Università di Parma, Italy
3 Dipartimento di Biologia ed Evoluzione – Sez. Risorse Agrotecnologiche e Farmaceutiche – AgriUnife, Università degli Studi di Ferrara, Italy
1 Dipartimento di Scienze Farmacologiche, Biologiche e Chimiche Applicate, Università di Parma, Italy
2 Dipartimento di Biologia Evolutiva e Funzionale, Università di Parma, Italy
3 Dipartimento di Biologia ed Evoluzione – Sez. Risorse Agrotecnologiche e Farmaceutiche – AgriUnife, Università degli Studi di Ferrara, Italy
Abstract
The Eph tyrosine kinase receptors and their ephrin ligands have been extensively studied for their roles in embryogenesis, where play a critical role in tissue boundaries formation and neuronal circuits development. In the adult ephrin system has also been implicated in several biological processes such as the regulation of insulin secretion, bone homeostasis, immune function, blood clotting and angiogenesis. Moreover increasing evidence showed an implication of this system in cell growth and survival, cell attachment and migration, highlighting a possible critical role in tumorigenesis, cancer progression, invasiveness and metastasis. Indeed altered expression and/or function of many members of this system, both receptors and ligands, promotes tumorigenesis and an aggressive tumor phenotype. Among all Ephs and ephrins, EphA2 receptor is the most widely studied because its overexpression has been correlated with poor prognosis and decreased survival in several cancers.
This scenario renders valuable the search for chemical entities interfering with the Eph-ephrin system and on this regard few information is available on the influence of secondary metabolites of plant origin. Interestingly phytocyanins, specific classes of plant proteins, have been found to share topological similarity with ephrin-B2 ectodomain and to be physiologically prone to interact with small molecular weight compounds, which in turn could interact also with ephrin system. On this regard it has been recently found that green tea catechins affect ephrin-induced angiogenesis in a no better-explained way, reinforcing this hypothesis. In order to verify if further plant sources, other than green tea, may inhibit ephrinA1-EphA2 interaction, we set and performed an ELISA screening binding assay for 133 plant extracts used as food supplements, essential and fixed oils.Given the limited knowledge on this topic, we have chosen to screen, the widest possible array of plant sources.
None of the essential oils resulted to be active up to 500μg/ml but we identified nine plant extracts able to reversibly inhibit binding between ephrinA1-Fc and EphA2-Fc in a dose-dependent manner (IC50 0.83-24μg/ml). Functional studies on PC3 prostate adenocarcinoma cells, naturally expressing EphA2 receptor, revealed that active extracts antagonized ephrinA1-Fc-induced EphA2–phosphorylation at concentrations (IC500.31-11.3μg/ml) comparable with working concentrations in the binding studies and without affecting cell viability or the phosphorylation of other receptor tyrosine kinases such as EGFR.
Our work, beside clarifying the action of green tea on ephrin system, identified other nine extracts interfering with this system. This data can be a starting point for the identification and isolation of the bioactive molecules contained in these extracts. Elucidation of the chemical structure could be useful for the development of synthetic molecules endowed with anticancer potential.
This scenario renders valuable the search for chemical entities interfering with the Eph-ephrin system and on this regard few information is available on the influence of secondary metabolites of plant origin. Interestingly phytocyanins, specific classes of plant proteins, have been found to share topological similarity with ephrin-B2 ectodomain and to be physiologically prone to interact with small molecular weight compounds, which in turn could interact also with ephrin system. On this regard it has been recently found that green tea catechins affect ephrin-induced angiogenesis in a no better-explained way, reinforcing this hypothesis. In order to verify if further plant sources, other than green tea, may inhibit ephrinA1-EphA2 interaction, we set and performed an ELISA screening binding assay for 133 plant extracts used as food supplements, essential and fixed oils.Given the limited knowledge on this topic, we have chosen to screen, the widest possible array of plant sources.
None of the essential oils resulted to be active up to 500μg/ml but we identified nine plant extracts able to reversibly inhibit binding between ephrinA1-Fc and EphA2-Fc in a dose-dependent manner (IC50 0.83-24μg/ml). Functional studies on PC3 prostate adenocarcinoma cells, naturally expressing EphA2 receptor, revealed that active extracts antagonized ephrinA1-Fc-induced EphA2–phosphorylation at concentrations (IC500.31-11.3μg/ml) comparable with working concentrations in the binding studies and without affecting cell viability or the phosphorylation of other receptor tyrosine kinases such as EGFR.
Our work, beside clarifying the action of green tea on ephrin system, identified other nine extracts interfering with this system. This data can be a starting point for the identification and isolation of the bioactive molecules contained in these extracts. Elucidation of the chemical structure could be useful for the development of synthetic molecules endowed with anticancer potential.