Somatostatin and opioid receptors do not regulate proliferation or apoptosis of the human multiple myeloma U266 cells

BACKGROUND: opioid and somatostatin receptors (SSTRs) that can assemble as heterodimer were individually reported to modulate malignant cell proliferation and to favour apoptosis. Materials and methods: SSTRs and opioid receptors expression were examined by RT-PCR, western-blot and binding assays, cell proliferation was studied by XTT assay and propidium iodide (PI) staining and apoptosis by annexin V-PI labelling. RESULTS: almost all human malignant haematological cell lines studied here expressed the five SSTRs. Further experiments were conducted on the human U266 multiple myeloma cells, which express also μ-opioid receptors (MOP-R). XTT assays and cell cycle studies provide no evidence for a significant effect upon opioid or somatostatin receptors stimulation. Furthermore, neither direct effect nor potentiation of the Fas-receptor pathway was detected on apoptosis after these treatments. CONCLUSION: these data suggest that SSTRs or opioid receptors expression is not a guaranty for an anti-tumoral action in U266 cell line.