USMLE (United States Medical Licensing Examination) Step 1 Practice Exam

What is a characteristic of the Warburg Effect in malignant cells?

1. Increased oxidative phosphorylation

2. High rates of glycolysis

3. Enhanced DNA repair mechanisms

4. Reduced cell growth

The correct answer is: High rates of glycolysis

The Warburg Effect is characterized by the preference of cancer cells to utilize glycolysis for energy production, even in the presence of adequate oxygen levels that would typically favor oxidative phosphorylation. This phenomenon leads to high rates of glycolysis, resulting in the production of lactate rather than complete oxidation of glucose. The reliance on glycolytic pathways allows malignant cells to generate ATP quickly and supports the biosynthetic processes necessary for rapid cell proliferation. This metabolic shift is advantageous for tumors, as it also provides intermediates for nucleotide, amino acid, and lipid synthesis, further facilitating their growth and survival. In contrast, increased oxidative phosphorylation refers to a more efficient energy production method that is not typically favored in cancer cells exhibiting the Warburg Effect. Enhanced DNA repair mechanisms and reduced cell growth are also not hallmarks of this metabolic change, as cancer cells generally exhibit compromised DNA repair in favor of proliferation and increased growth rates. Thus, the high rates of glycolysis stand out as a defining characteristic of the Warburg Effect in malignant cells.