Tiazofurin: molecular and clinical action

Area of Science:

• Biochemistry
• Molecular Biology
• Oncology

Background:

• Inosine monophosphate dehydrogenase (IMP DH) activity is elevated in various human tumors, particularly leukemic blast cells.
• This elevation is linked to increased mRNA concentration of the type II isozyme.

Purpose of the Study:

• To provide an overview of the molecular and clinical impact of tiazofurin.
• To elucidate the mechanism of action and therapeutic efficacy of tiazofurin in cancer treatment.

Main Methods:

• Biochemical assays to measure IMP DH activity and GTP concentration.
• Analysis of mRNA levels for IMP DH isozymes.
• Clinical studies involving tiazofurin and allopurinol administration.
• Assessment of signal transduction pathway modulation.

Main Results:

• Tiazofurin is converted to its active metabolite, TAD, which inhibits IMP DH activity by binding to the NADH site.
• Inhibition of IMP DH leads to decreased GTP concentration, down-regulation of ras and myc oncogenes, and induced blast cell maturation.
• Tiazofurin and allopurinol combination therapy reduced IMP DH activity and GTP levels in patients, with increased serum hypoxanthine being crucial for treatment success.
• Tiazofurin demonstrated additive or synergistic effects with several other anti-cancer agents, including ribavirin and taxol.

Conclusions:

• Tiazofurin and allopurinol effectively reduce GTP concentration in leukemic blast cells by inhibiting IMP DH and guanine-5'-phosphate reductase (GPRT) activities.
• This leads to induced cell maturation, down-regulation of oncogenes, and potentially reduced signal transduction.
• Tiazofurin treatment in leukemic patients yields over 75% therapeutic response rates, allowing for prolonged treatment with good quality of life.