BACKGROUND Patients with severe psoriasis may be unresponsive to or unable to tolerate the adverse effects of traditional therapy. Thioguanine has been used to treat psoriasis, but experience is limited. Most previous studies have used daily therapy and have demonstrated significant hematologic abnormalities. OBJECTIVE To reduce the adverse effects of traditional thioguanine therapy, our stud...

Thioguanine and mercaptopurine are prodrugs requiring conversion into thiopurine nucleotides to exert cytotoxicity. Thiopurine S-methyltransferase (TPMT), an enzyme subject to genetic polymorphism, catabolizes thiopurines into inactive methylated bases, but also produces methylthioguanine nucleotides and methylmercaptopurine nucleotides from thioguanine and mercaptopurine nucleotides, respectiv...

The effects of 6-thioguanine on purine biosynthesis and cell viability have been examined in H.Ep. 2 cells grown in culture. Toxicity is not reversed by aminoimidazolecarboxamide, suggesting that inhibition of purine biosynthesis de novo is not the sole mechanism of toxicity. Also, 6-(methylmercapto)purine ribonucleoside, a potent inhibitor of purine biosynthesis de novo, produces more marked r...

Regenerating rat liver was used as a semisynchronous system in which to investigate the effects of 6-thioguanine on biochemical processes occurring in discrete phases of the cell cycle. 6-Thioguanine inhibited the first wave of DNA biosynthesis in regenerating rat liver. This effect appeared to be the result of a decrease, caused by 6-thioguanine, in the induction of several enzyme activities (...

thioguanine is attributable to incorporation of the anti metabolite into deoxyribonucleic acid (DNA) and that re sistance may be the result of a lower capacity for such in corporation; and (d) Paterson (17, 19), using a 6-mercap topurine-resistant Ehrlich carcinoma, proposed a decreased rate of transport of drug across the cell membrane as a possible mechanism for the resistant character of thi...

The differential sensitivity of mammalian tissues to 6-thioguanine was studied by measuring the metabolic fate of this agent in the bone marrow and intestinal mucosa of rabbits. After the injection of thioguanine-S35, intestinal mucosa contained, per gram of tissue, a sixteen-fold higher level of 6-thiouric acid, but less than one-half the quantity of thioguanine mononucleotide than did bone ma...

The guanine analog, 6-thioguanine (4), has been found to be a potent inhibitor of animal neoplasms (2) and human leukemia (5) when administered alone, and even more potent when used in com bination with the inhibitor of de novo purine syn thesis, azaserine (10, 12). We have developed a thioguanine-resistant subline of the Ehrlich ascites carcinoma. Using this as a tool, we have studied the meta...

BACKGROUND Psoriasis is a common and persistent disease characterized chiefly by marked epidermal and endothelial cell proliferation and inflammation. These changes are likely a result of activated T lymphocytes infiltrating skin tissue or, in the case of psoriatic arthritis, the joints. OBJECTIVE To test the hypothesis that the antimetabolite 6-thioguanine (Sigma-Aldrich, St Louis, Mo) might...

The capacity of several purinethiol derivatives to produce prolongation of survival in mice bearing ascites-cell tumors and to produce feedback inhibition of purine synthesis in vivo in the tumor cells was investigated. Included were tumors susceptible and tumors resistant to treatment with 6-thioguanine. With susceptible tumors, certain of the purinethiols could increase survival of tumor-bear...

6-Thioguanine (3) has been shown to inhibit a wide spectrum of neoplasms. Its anti-tumor prop erties are markedly potentiated when combined with azaserine, an inhibitor of the synthesis de novo of purines (10, 13). One of these reports also indicated that, for maximum effect, the antimetabolites had to be administered simultaneous ly. These results suggest that thioguanine inter feres with some...