Disparate Response to Methotrexate in Stem Versus Non-Stem Cells

Area of Science:

• Biochemistry
• Cell Biology
• Pharmacology

Background:

• Methotrexate (MTX) is a chemotherapy drug that inhibits dihydrofolate reductase (DHFR), crucial for nucleotide synthesis.
• MTX's non-selectivity causes damage to normal cells, particularly affecting bone and connective tissues.
• The role of DHFR in normal cell response to MTX and differential sensitivity among connective tissue cell types is not well understood.

Purpose of the Study:

• To investigate the role of DHFR and nucleotide synthesis in normal cell response to MTX.
• To compare MTX adverse effects across different normal cell types, identifying sensitive populations and resistant sources for regenerative medicine.
• To explore therapeutic strategies for mitigating MTX toxicity in patients undergoing chemotherapy.

Main Methods:

• Overexpression of DHFR and exogenous delivery of amino acids and nucleosides to rescue normal cells.
• DHFR knockdown in adipose-derived stem cells (ASCs) to assess its impact on osteogenesis.
• Comparative analysis of MTX sensitivity in ASCs, bone marrow stem cells, and osteoblasts at different differentiation stages.

Main Results:

• DHFR overexpression or nutrient supplementation protected normal cells from MTX toxicity.
• DHFR knockdown compromised MTX-treated ASC osteogenesis.
• ASCs and bone marrow stem cells exhibited greater MTX resistance than osteoblasts, but stem cells became sensitive upon differentiation.

Conclusions:

• Stem cell survival and tissue maintenance under MTX treatment depend on their undifferentiated state.
• Preserving the stem cell state during chemotherapy may improve long-term tissue health.
• Targeting DHFR and nucleotide synthesis pathways offers potential therapeutic avenues for managing MTX side effects.