Collateral sensitivity to azidothymidine in methotrexate resistant human leukemia cells

Area of Science:

• Biochemistry
• Pharmacology
• Cancer Biology

Background:

• Methotrexate (MTX) resistance is a significant clinical challenge in leukemia treatment.
• Understanding resistance mechanisms is crucial for developing effective therapeutic strategies.
• The CCRF-CEM human leukemia cell line provides a model for studying in vivo-like MTX resistance.

Purpose of the Study:

• To investigate the mechanisms of MTX resistance in the CCRF-CEM leukemia cell line.
• To determine if MTX-resistant cells exhibit collateral sensitivity to other drugs.
• To explore potential clinical implications of MTX resistance mechanisms.

Main Methods:

• Evolving a methotrexate-resistant subline (CEM/MTX) from CCRF-CEM cells through stepwise MTX exposure.
• Analyzing dihydrofolate reductase (DHFR) activity and gene amplification in resistant cells.
• Assessing methotrexate uptake in both sensitive and resistant cell lines.
• Measuring thymidine kinase (TK) activity and evaluating sensitivity to azidothymidine (AZT).

Main Results:

• A 15.8-fold MTX-resistant cell line (CEM/MTX) was successfully generated.
• CEM/MTX cells showed increased DHFR activity due to gene amplification and impaired MTX uptake.
• A 2-fold increase in TK activity was observed in CEM/MTX cells.
• CEM/MTX cells exhibited collateral sensitivity to azidothymidine (AZT).

Conclusions:

• Methotrexate resistance in leukemia involves multiple mechanisms, including DHFR amplification and reduced drug uptake.
• Increased thymidine kinase activity in MTX-resistant cells confers collateral sensitivity to azidothymidine.
• These findings suggest that azidothymidine could be a viable therapeutic option for patients with MTX-resistant leukemia.