Methionine-sensitive glycolysis in transformed cells

Area of Science:

• Biochemistry
• Cell Biology
• Oncology

Background:

• Tumor cells exhibit altered metabolic pathways, including enhanced glycolysis (the Warburg effect).
• Targeting tumor cell metabolism is a promising strategy for cancer therapy.

Purpose of the Study:

• To investigate the effect of methionine on glycolysis in various tumor and normal cell lines.
• To understand the specificity and reversibility of methionine-induced glycolytic inhibition.

Main Methods:

• Culturing of Kirsten murine sarcoma virus-transformed rat kidney (K-NRK) cells, normal rat kidney (NRK-49F) cells, chemically transformed canine kidney cells, normal canine kidney cells, and Ehrlich ascites tumor cells.
• Treatment with varying concentrations of methionine and measurement of glycolysis rates.
• Assessment of reversibility by removing methionine and evaluating glycolytic activity.
• Testing the role of serum concentration and cycloheximide.
• Investigating the specificity of amino acid transport systems.

Main Results:

• Methionine significantly inhibited glycolysis in K-NRK cells (60-75%) and Ehrlich ascites tumor cells (approx. 50%) but had minimal effect on normal rat kidney cells.
• Chemically transformed canine cells showed sensitivity to methionine, unlike their normal counterparts.
• Inhibition was reversible within 2 hours of methionine removal.
• Methionine's inhibitory effect required a minimum serum level (7%) and was not affected by cycloheximide.
• Amino acids transported by system A specifically inhibited tumor cell glycolysis, with phenylalanine being an exception.

Conclusions:

• Methionine selectively inhibits glycolysis in transformed and tumor cells.
• The inhibition is dependent on specific amino acid transporters (System A) and is rapidly reversible.
• These findings suggest a potential metabolic vulnerability in tumor cells that can be targeted by specific amino acids.