2‑Cl‑IB‑MECA regulates the proliferative and drug resistance pathways, and facilitates chemosensitivity in pancreatic and liver cancer cell lines.

Specific A3 adenosine receptor (A3AR) agonist, 2‑chloro‑N6‑(3‑iodobenzyl)‑5'‑N‑methylcarboxamidoadenosine (2‑Cl‑IB‑MECA), demonstrates anti‑proliferative effects on various types of tumor. In the present study, the cytotoxicity of 2‑Cl‑IB‑MECA was analyzed in a panel of tumor and non‑tumor cell lines and its anticancer mechanisms in JoPaca‑1 pancreatic and Hep‑3B hepatocellular carcinoma cell lines were also investigated. Initially, decreased tumor cell proliferation, cell accumulation in the G1 phase and inhibition of DNA and RNA synthesis was found. Furthermore, western blot analysis showed decreased protein expression level of β‑catenin, patched1 (Ptch1) and glioma‑associated oncogene homolog zinc finger protein 1 (Gli1), which are components of the Wnt/β‑catenin and Sonic hedgehog/Ptch/Gli transduction pathways. In concordance with these findings, the protein expression levels of cyclin D1 and c‑Myc were reduced. Using a luciferase assay, it was revealed for the first time a decrease in β‑catenin transcriptional activity, as an early event following 2‑Cl‑IB‑MECA treatment. In addition, the protein expression levels of multidrug resistance‑associated protein 1 and P‑glycoprotein (P‑gp) were reduced and the P‑gp xenobiotic efflux function was also reduced. Next, the enhancing effects of 2‑Cl‑IB‑MECA on the cytotoxicity of conventional chemotherapy was investigated. It was found that 2‑Cl‑IB‑MECA enhanced carboplatin and doxorubicin cytotoxic effects in the JoPaca‑1 and Hep‑3B cell lines, and a greater synergy was found in the highly tumorigenic JoPaca‑1 cell line. This provides a novel