Purine enzyme profile in human colon-carcinoma cell lines and differential sensitivity to deoxycoformycin and 2'-deoxyadenosine in combination.
Different cell lines, 2 from human colon carcinoma (LoVo and HT29) and 1 from Chinese hamster ovary (CHO K-I), were examined to assess the effect of deoxycoformycin (dCF), an inhibitor of adenosine deaminase (ADA), and 2'-deoxyadenosine (dAdo) on their growth. When used alone, neither dCF or dAdo were cytotoxic for the 3 cell lines, while their combination caused inhibition of cell growth, with the following sensitivity: CHO K-I > LoVo > HT29. We studied the pattern of enzymatic activities involved in the metabolism of dAdo in the 3 cell lines. The phosphorylation of dAdo by adenosine kinase appears to play a central role in the toxicity of the deoxynucleoside in combination with dCF. In fact, CHO K-I cells, which are the most sensitive, possess the highest level of this enzyme. Moreover, the cytotoxic effect was almost completely reversed in the 3 cell lines when inhibitors of adenosine kinase, such as 5'-amino-5'-deoxyadenosine and iodotubercidine, were added to the culture medium together with dCF and dAdo. In addition, baby hamster kidney (BHK) adenosine-kinase-deficient (AK-) cells were highly resistant to this treatment. Uptake inhibition of dAdo using dipyridamole also caused reversal of the toxicity. The AMP and deoxyAMP dephosphorylating activities, much lower in the CHO K-I cells, also appear to play a central role in the toxicity of dAdo when adenosine deaminase is inhibited. However, our data suggest that other factors may modulate the toxic effect, such as S-adenosyl-homocysteine-hydrolase inhibition by dAdo at high concentrations.
Camici
M
M
Dipartimento di Fisiologia e Biochimica, Università di Pisa, Italy.
Turriani
M
M
Tozzi
M G
MG
Turchi
G
G
Cos
J
J
Alemany
C
C
Miralles
A
A
Noe
V
V
Ciudad
C J
CJ
D000248:Adenosine Kinase / Q000378:metabolism; D000964:Antimetabolites, Antineoplastic; D002455:Cell Division / Q000187:drug effects; D003110:Colonic Neoplasms; D003839:Deoxyadenosines / Q000008:administration & dosage*; D004176:Dipyridamole / Q000494:pharmacology; D004357:Drug Synergism; D006801:Humans; D066298:In Vitro Techniques; D015649:Pentostatin / Q000008:administration & dosage*; D011687:Purines / Q000378:metabolism*; D012435:S-Adenosylhomocysteine / Q000494:pharmacology; D014407:Tumor Cells, Cultured / Q000201:enzymology
D000964:Antimetabolites, Antineoplastic; D003839:Deoxyadenosines; D011687:Purines; D015649:Pentostatin; D004176:Dipyridamole; D012435:S-Adenosylhomocysteine; D000248:Adenosine Kinase; C058118:2'-deoxyadenosine