ALTERED PYRUVATE KINASE MRNA EXPRESSION AND ABNORMAL METABOLIC PROFILES IN MELANOMA CELLS EXPRESSING THE WARBURG EFFECT
Jonathan McKinney1, Todd Thompson2.
1McDaniel College, Westminster, MD, 2The University of New Mexico, Albuquerque, NM.
Many cancer cells preferentially undergo lactic acid fermentation from glycolysis rather than oxidative phosphorylation. Even with adequate amounts of oxygen to metabolize glucose that could yield higher amounts of energy, cancer cells produce lactic acid in a process called the Warburg effect. Moreover, melanoma cancers can exhibit excessive lactic acid production, as was found in the SKMEL19 and SKMEL29 melanoma cell lines that exhibit the Warburg effect. Phenotypic changes that may facilitate the Warburg effect include alterations in the expression of splice variants of pyruvate kinase (PK), which performs the final step in glycolysis, and increased expression of lactate dehydrogenase A (LDH-A), the enzyme responsible for producing lactic acid from pyruvate. Surprisingly, in the current study, gene expression measured using QPCR showed decreased levels of LDH-A mRNA in SKMEL19 and SKMEL29 melanoma cells compared to cancer cells that do not undergo this process (i.e., PC3 and SKMEL103 cells). However, increased LDH protein expression was observed in these cells. Inhibition of LDH via oxamic acid led to decreased growth. Levels of PK mRNA isoforms PKM1 and PKM2 were also determined, the latter being characteristic of cancers exhibiting the Warburg effect. The ratio of PKM2 to PKM1 mRNA was found to be increased in SKMEL19 and SKMEL29 cells, ultimately suggesting PKM2 as a key player in mediating the Warburg effect. Our results suggest that cancer cells exhibiting the Warburg effect have developed highly coordinated metabolic adaptations that promote cancer growth.