Understanding the Factors Behind Cancer Cell Metabolism Changes

Investigation of Cancer Cell Metabolism Shifts

Understanding Cancer Cell Characteristics

Recent research explores the underlying causes of metabolic shifts in cancer cells. Cancer is characterized by the uncontrolled proliferation of cells, which necessitates substantial energy and raw materials for continuous division. In solid tumors, these cancer cells often exist in environments deficient in nutrients and oxygen. As a result, they undergo significant alterations in their metabolic pathways to survive these challenging conditions.

Metabolic Pathway Differences

Normal cells typically convert glucose into pyruvate during energy production through oxidative phosphorylation. In contrast, cancer cells primarily rely on glycolysis, resulting in the production of lactic acid instead of pyruvate. This metabolic shift, known as the Warburg effect, is beneficial for rapidly dividing cancer cells, as it enables them to produce energy and carbon, essential for creating new cells. By comprehending this fundamental biological difference, researchers aim to identify innovative methods for targeting and treating cancer.

Key Factors in Metabolic Changes

The Role of RAS Gene Mutations

One gene frequently mutated in cancer is RAS, which has been shown to influence the metabolic reprogramming of cancer cells. The specific proteins that interact with RAS to alter metabolic signaling remain largely unknown, but those involved in maintaining mitochondrial function are likely contributors, given the mitochondria’s role as the cell’s powerhouse.

Dynamin-related Protein 1 and Pancreatic Cancer

A recent study published in Cell Reports examined the function of Dynamin-related protein 1 (Drp1) in the development and progression of pancreatic cancer. Researchers focused on whether RAS could regulate Drp1’s activity, as this protein is crucial for mitochondrial fragmentation during cell proliferation. Fragmented mitochondria can accelerate glycolysis, facilitating cancer growth.

Drp1’s Influence on Cancer Development

Experimental Findings on Drp1

The study involved generating cells with RAS mutations that either produced Drp1 or did not. A control cell line without RAS mutations but capable of producing Drp1 was also used. The findings indicated that cells lacking Drp1 were unable to divide and grow. Reintroducing Drp1 enabled these cells to resume division. This pattern was replicated in patient-derived cell lines where the absence of Drp1 led to inhibited growth, suggesting that Drp1 is critical for the cancerous potential of RAS-mutated cells.

Impact of Drp1 on Metabolism

The research team discovered that cells without Drp1 produced lower amounts of lactic acid, indicating Drp1’s involvement in glycolytic metabolism. They examined the interaction between Drp1 and hexokinase-2, a protein present on the mitochondrial membrane that remains active when the RAS gene is mutated. The results showed that deletion of Drp1 in RAS-mutated cells decreased hexokinase-2 expression, implying Drp1’s role in stabilizing this enzyme, which is vital for glycolysis.

The Role of Drp1 in Tumor Dynamics

Genetically Engineered Mouse Model

Researchers developed genetically engineered mice predisposed to pancreatic cancer and administered tamoxifen to inhibit Drp1 production. Mice without Drp1 exhibited a 45-day longer survival rate compared to those without the inhibitor. Although these mice still developed tumors, their cancer progressed more slowly. Notably, some Drp1 production persisted even with tamoxifen treatment, indicating strong selective pressure against the loss of Drp1 in cancer cells.

Effects of Drp1 on Mitochondrial Function

The study further established that the absence of Drp1 led to mitochondrial dysfunction, impacting fatty acid metabolism. Observations revealed delays in the movement of fatty acids from lipid droplets. When cells were forced to rely on fatty acid oxidation, those unable to produce Drp1 failed to grow.

Conclusion and Future Directions

Drp1’s Dual Role in Cancer Progression

The researchers concluded that Drp1 plays two critical roles in tumor progression: facilitating the switch to glycolysis via hexokinase-2 stabilization and regulating mitochondrial function. This suggests that inhibiting Drp1 in cancer cells may offer therapeutic potential. However, testing Drp1 inhibitors on pancreatic cancer cells remains necessary to validate this approach.

Dr. Kashatus, the principal investigator of the study, noted, “Inhibiting [mitochondrial division in patients’ cancer cells] would be a nice future goal for us. However, the drugs targeting this process are really very early in development, and so it’s not something that will really be ready for the clinic anytime soon.”

References

Cohen, R. et al. Targeting cancer cell metabolism in pancreatic adenocarcinoma. Oncotarget 6, 16832 (2015).
Guillaumond, F., Iovanna, J. L. & Vasseur, S. Pancreatic tumor cell metabolism: focus on glycolysis and its connected metabolic pathways. Archives of biochemistry and biophysics 545, 69-73 (2014).
Kimmelman, A. C. (AACR, 2015).
Kashatus, D. F. The regulation of tumor cell physiology by mitochondrial dynamics. Biochemical and biophysical research communications 500, 9-16 (2018).
Nagdas, S. et al. Drp1 Promotes KRas-Driven Metabolic Changes to Drive Pancreatic Tumor Growth. Cell Reports 28, 1845-1859. e1845 (2019).
Barney, J. Pancreatic cancer discovery reveals how the aggressive cancer fuels its growth (2019).
Image by Konstantin Kolosov from Pixabay.