Abstract:

Background and purpose: Despite the high remission rate in patients with multiple myeloma (MM) after the standard regimen, but often relapsed and resistant. It has been shown that modulation of cAMP can induce cell cycle arrest and apoptosis in a variety of tumor cells, which has become an interesting approach to cancer therapy. This study aimed to investigate possible effects of cyclic adenosine monophosphate (cAMP) analogue 8-(4-chlorophenylthio) adenosine 3’, 5’-cyclic monophosphate (8-CPT-cAMP) on multiple myeloma cells, provide direction to develop new drugs for the treatment of MM. Methods: The myeloma cell line U266 cells were treated with 8-CPT-cAMP of different concentrations. The proliferation of U266 cells was evaluated through cell counting kit (CCK-8) assay, flow cytometry was used to analyze the changes of cell were distribution, apoptosis rate as well as mitochondrial transmembrane potential (ΔΨm) in U266 cells before and after the treatment. Meanwhile, real-time quantitative polymerase chain reaction (RT-PCR) and Western blot assay were used to detect expression levels of apoptosis regulators including caspase-8, caspase-9, Bcl-2 and Bax genes in U266 cells before and after the treatment. Results: The U266 cells were treated 5 days with 8-CPT-cAMP of different concentration, it was shown that 8-CPT-cAMP could significantly inhibit cell growth of U266 cells in a concentration and time dependent manner, the IC50 of 8-CPT-cAMP was reduced obvious prolonged reaction time, and reached to 58.52 μmol/L in the fifth day. The cell cycle of U266 cells was stopped in G₀/G₁ stage as the progress of concentration. It was showed statistical significant difference associated with the cellular proliferation inhibition rate and apoptosis rate in different concentration and control (P<0.05). Meanwhile, 8-CPT-cAMP could induce mitochondrial transmembrane potential collapse in U266 cells. Compared with control groups, the levels of Bcl-2 mRNA transcripts and protein in U266 cells were reduced in 8-CPT-cAMP treated groups (P<0.05), while the levels of caspase-9, Bax mRNA transcription and the expression of Bax protein were increased in treatment groups, but the caspase-8 mRNA had no statistical significant difference with controls. Conclusion: 8-CPT-cAMP can inhibit the proliferation and promote apoptosis of myeloma cells, which might be mediated by caspase via mitochondrial pathway.

Key words: cAMP, Myeloma, Cell apoptosis