Cell experiment:

Various amounts of cells, ranging from 1,000 to 900,000, suspended in 3 mL of standard medium, are plated in 35-mm dishes and incubated in the absence (control) and in the presence of both 1 μM dCF and 0.1 mM dAdo, as indicated in each experiment. dCf was added to the standard medium 30 min before 2’-deoxyadenosine (dAdo). Furthermore, an incubation is performed in which 0.1 mM 2’-deoxyadenosine alone is added to the standard medium. After 4 days of incubation, the standard medium is withdrawn, then 0.5 mL of 0.025% trypsin containing 0.02% EDTA is added and kept for few minutes at 37℃. The cells are collected, diluted in an appropriate volume of standard medium, and counted[1].

2’-deoxyadenosine inhibits the growth of human colon-carcinoma cell lines and is found to be associated with purine nucleoside phosphorylase (PNP) deficiency.

In the absence of deoxycoformycin, 2’-deoxyadenosine is primarily deaminated to 2’-deoxyinosine and then converted into hypoxanthine. In the presence of the inhibitor, the deoxynucleoside, in addition to a phosphorylation process, undergoes phosphorolytic cleavage giving rise to adenine. The conversion of 2’-deoxyadenosine to adenine might represent a protective device, emerging when the activity of adenosine deaminase is reduced or inhibited. There is much evidence to indicate that the enzyme catalyzing this processs may be distinct from methylthioadenosine phosphorylase and S-adenosyl homocysteine hydrolase, which are the enzymes reported to be responsible for the formation of adenine from 28-deoxyadenosine in mammals[1].

References:
[1]. Bemi V, et al. Deoxyadenosine metabolism in a human colon-carcinoma cell line (LoVo) in relation to its cytotoxic effect in combination with deoxycoformycin. Int J Cancer. 1998 Mar 2;75(5):713-20.