Dual addressing of thymidine synthesis pathways for effective targeting of proliferating melanoma

Area of Science:

• Oncology
• Molecular Biology
• Radiochemistry

Background:

• Melanoma cell proliferation relies on nucleotide synthesis pathways.
• Targeting salvage pathways offers a potential therapeutic strategy.
• Differential enzyme expression (thymidylate synthase, thymidine kinase 1) exists between melanoma subtypes.

Purpose of the Study:

• To investigate blocking thymidine de novo synthesis for sensitizing melanoma cells to nucleoside salvage pathway targeting.
• To evaluate the expression of key enzymes in differentiated and invasive melanoma cells.
• To assess the efficacy of a radioactive thymidine analog for in vivo tumor targeting.

Main Methods:

• Enzyme expression analysis of thymidylate synthase (TS) and thymidine kinase 1 (TK1).
• Inhibition of de novo synthesis using 5-fluoro-2'-deoxyuridine (FdUrd) or methotrexate (MTX).
• Treatment with irradiation-emitting thymidine analog [123/125I]-5-iodo-4'-thio-2'-deoxyuridine (123/125I-ITdU) and in vivo imaging.

Main Results:

• FdUrd pretreatment significantly increased 125I-ITdU uptake and DNA incorporation in invasive IGR37 melanoma cells.
• This sensitization effect was less pronounced in differentiated IGR1 cells.
• Inhibition of TS resulted in preferential accumulation of 123I-ITdU in tumor tissue in vivo.

Conclusions:

• Blocking thymidine de novo synthesis enhances the efficacy of radioactive salvage pathway targeting in melanoma.
• This preclinical study provides a rationale for developing targeted radiotherapeutic approaches for melanoma.
• Selective targeting of salvage pathways offers a promising strategy for melanoma treatment.