Abstract: (Sp)-Octyl-8-chloroadenosine-3',5'-cyclophosphate (OCC), a newly synthesized 8-Cl-c-AMP derivative, strongly induced inhibition and differentiation in human leukemia HL 60 cells. In flow cytometry, OCC brought about a block at the G1 phase of HL-60 cell cycle. OCC inhibited strongly the synthesis of DNA without affecting the synthesis of RNA and protein in HL-60 cells and also activated the c-AMP dependent protein kinase in the cytosol of HL-60 cells. 8-Chloroadenosine is the active metabolite of OCC and inhibited significantly the growth of tumour in vitro and in vivo tests. 8-Chloroadenosine can induce differentiation of gastric mucoid adenocarcinoma cell line MGc80-3 and induce apoptosis in the MOLT-4 cells. The mechanism of the antitumour effects of 8 chloroadenosine was discussed.

Key words: (Sp)-Octyl-8-chloroadenosine-3',5'-cyclophosphate (OCC), 8-Chloroadeno- sine, Antitumour activities