2-chloro-n(6)-(3-iodobenzyl)adenosine-5--n-methyluronamide and Thyroid-Neoplasms

Apoptosis is an endogenous process that can be a useful anti-cancer tool. This study aimed to investigate the effect of Cl-IB-MECA, adenosine receptor A3 agonist, on TRAIL-induced apoptosis of thyroid carcinoma cells. Cl-IB-MECA enhanced TRAIL-mediated apoptosis in FRO but not in ARO cells. This effect was correlated to higher expression levels of DR5 on FRO than ARO cells, that instead presented higher levels of decoy receptors, DcR1 and DcR2. To understand the cross-talk between the effect of Cl-IB-MECA and TRAIL, we evaluated the nuclear translocation of p65 and c-Rel. Since the dependency by NF-kappaB, TRAIL promoted the nuclear translocation of both p65 and c-Rel subunits. However, the addition of Cl-IB-MECA led to the predominant translocation of c-Rel after TRAIL addition. Furthermore, Bcl-2, cFLIP and pAkt were lower induced than caspase-3 and -9 in FRO cells. To discriminate a specific effect of TRAIL, we used tumour necrosis factor-alpha (TNF-alpha) with Cl-IB-MECA. In this case, no synergism was observed. In addition, the effect of Cl-IB-MECA was not A3 receptor-dependent since its antagonists, MRS1191 and FA385, failed to block Cl-IB-MECA activity on TRAIL-treated FRO cells. In conclusion, Cl-IB-MECA enhanced TRAIL-mediated apoptosis via NF-kappaB/c-Rel activation and DR5-dependent manner. This study may shed light on a potential drug cocktail that may prove useful as anti-cancer in an in vivo animal model.

Topics: Adenosine; Adenosine A3 Receptor Antagonists; Apoptosis; CASP8 and FADD-Like Apoptosis Regulating Protein; Cell Line, Tumor; Drug Resistance, Neoplasm; Drug Synergism; Humans; NF-kappa B; Phosphorylation; Proto-Oncogene Proteins c-akt; Proto-Oncogene Proteins c-bcl-2; Proto-Oncogene Proteins c-rel; Receptor, Adenosine A3; Receptors, TNF-Related Apoptosis-Inducing Ligand; Signal Transduction; Thyroid Neoplasms; TNF-Related Apoptosis-Inducing Ligand; Tumor Necrosis Factor-alpha

A3 adenosine receptor (A3AR) agonists have been reported to modulate cellular proliferation. This work was aimed to investigate the expression and the possible implication of A3AR in the human thyroid carcinomas. Normal thyroid tissue samples did not express A3 adenosine receptor, while primary thyroid cancer tissues expressed high level of A3AR, as determined by immunohistochemistry analysis. In human papillary thyroid carcinoma cell line, NPA, at concentrations > or =10 microM, the A3AR-selective agonist 2-chloro-N(6)-(3-iodobenzyl)adenosine-5'-N-methylcarboxamide (Cl-IB-MECA) produced inhibition of cell growth, by blocking the G(1) cell cycle phase in a concentration- and time-dependent manner. This effect was well correlated with a reduction of protein expression of cyclins D1 and E2 after 24 hours of Cl-IB-MECA treatment. Moreover Cl-IB-MECA induced dephosphorylation of ERK1/2 in a time- and concentration-dependent manner, which in turn inhibits cell proliferation. The effect of Cl-IB-MECA was not prevented by A3AR antagonists, MRS1191 or MRS1523 or FA385. Furthermore, neither nucleoside transporter inhibitors, Dypiridamole and NBTI, nor the A1, A2A and A2B receptors antagonists were able to block the response to Cl-IB-MECA. Although Cl-IB-MECA has been shown to influence cell death and survival in other systems through an A3AR-mediated mechanism, in NPA cells the growth inhibition induced by micromolar concentrations of Cl-IB-MECA is not related to A3AR activation and hence that its effects on human papillary carcinoma cell line seem to be independent of the presence of this receptor subtype.

Topics: Adenosine; Adenosine A3 Receptor Agonists; Cell Cycle; Cell Line, Tumor; Cell Proliferation; Cyclins; Dose-Response Relationship, Drug; G1 Phase; Humans; Immunohistochemistry; Thyroid Neoplasms; Time Factors