PAF1/HIF1α Axis Promotes Pancreatic Cancer Aggressiveness by Regulating Glycolytic Metabolism

Background

Pancreatic cancer (PC) is a highly aggressive malignant tumor, with pancreatic ductal adenocarcinoma (PDAC) being the most common type. Despite significant advancements in cancer treatment in recent years, the 5-year survival rate for pancreatic cancer remains extremely low, at approximately 12.5%. The aggressiveness and drug resistance of pancreatic cancer are closely related to metabolic reprogramming, particularly the enhancement of glycolytic metabolism. However, the specific mechanisms underlying metabolic reprogramming in pancreatic cancer remain unclear.

RNA polymerase II-associated factor 1 (PAF1) is a transcription elongation factor. Previous studies have shown its important role in various cancers, including the proliferation, metastasis, and maintenance of cancer stem cells (CSCs) in pancreatic cancer. However, the role of PAF1 in the metabolic reprogramming of pancreatic cancer has not been thoroughly investigated. This study aims to explore the role of PAF1 in the metabolic reprogramming of pancreatic cancer, particularly its interaction with hypoxia-inducible factor 1α (HIF1α) and its regulation of lactate dehydrogenase A (LDHA) expression.

Source of the Paper

This paper was authored by Ayoola O. Ogunleye and colleagues from multiple departments at the University of Nebraska Medical Center, including the Department of Biochemistry and Molecular Biology, the Department of Pathology and Microbiology, and the Fred & Pamela Buffett Cancer Center. The paper was published in 2024 in the journal Cancer & Metabolism, titled “PAF1/HIF1α axis rewires the glycolytic metabolism to fuel aggressiveness of pancreatic cancer.”

Research Process and Results

1. Correlation Analysis of PAF1 with Glycolytic Metabolic Genes

The study first explored the relationship between PAF1 and metabolic pathways in pancreatic cancer through gene expression analysis. The results showed that PAF1 expression is significantly correlated with glycolysis and oxidative phosphorylation pathways. Further analysis revealed that PAF1 is positively correlated with key glycolytic genes (such as LDHA, PDK1, and GLUT1). Immunohistochemical analysis showed that the expression of PAF1 and LDHA gradually increased in pancreatic cancer tissues, while their expression was lower in normal pancreatic tissues. These results suggest that PAF1 may play an important role in the glycolytic metabolism of pancreatic cancer.

2. Effect of PAF1 Knockdown on Glycolytic Gene Expression

To validate the role of PAF1 in glycolytic metabolism, the research team used shRNA technology to knock down PAF1 expression in pancreatic cancer cell lines (Mia PaCa-2 and SW1990). The results showed that PAF1 knockdown significantly reduced the mRNA and protein levels of key glycolytic genes (such as LDHA, PDK1, and GLUT1). Additionally, PAF1 knockdown significantly reduced the clonogenic ability of cells, indicating the important role of PAF1 in the proliferation of pancreatic cancer cells.

3. Effect of PAF1 Knockdown on Lactate Production and Glucose Uptake

The study further assessed the impact of PAF1 knockdown on pancreatic cancer cell metabolism through lactate production and glucose uptake experiments. The results showed that PAF1 knockdown significantly reduced extracellular lactate concentration and glucose uptake, indicating that PAF1 plays a key role in the glycolytic metabolism of pancreatic cancer cells.

4. Effect of PAF1 Knockdown on Cellular Energy Metabolism

By measuring extracellular acidification rate (ECAR) and oxygen consumption rate (OCR), the research team found that PAF1 knockdown significantly reduced the glycolytic rate of pancreatic cancer cells while increasing the oxidative phosphorylation rate. These results suggest that PAF1 knockdown shifts pancreatic cancer cells from glycolytic metabolism to oxidative phosphorylation.

5. Interaction Between PAF1 and HIF1α

Through co-immunoprecipitation experiments, the research team confirmed that PAF1 specifically interacts with HIF1α in pancreatic cancer cells, while no such interaction was observed in normal pancreatic cells. Additionally, immunofluorescence experiments showed that PAF1 and HIF1α are highly co-expressed in pancreatic cancer cells but expressed at lower levels in normal pancreatic cells.

6. Regulation of the LDHA Promoter by the PAF1/HIF1α Complex

Using chromatin immunoprecipitation (ChIP) experiments, the research team found that the PAF1/HIF1α complex binds to the HIF1α binding site on the LDHA promoter, thereby regulating LDHA transcription. This result indicates that PAF1 regulates LDHA expression through a HIF1α-mediated mechanism, thereby influencing the glycolytic metabolism of pancreatic cancer.

Conclusion and Significance

This study demonstrates that PAF1 regulates LDHA expression through a HIF1α-mediated mechanism, thereby promoting glycolytic metabolism and tumor progression in pancreatic cancer. The PAF1/HIF1α axis plays a key role in the metabolic reprogramming of pancreatic cancer, providing a new potential target for pancreatic cancer treatment. The findings not only reveal a new function of PAF1 in pancreatic cancer metabolism but also provide a theoretical basis for the development of anticancer drugs targeting the PAF1/HIF1α axis.

Research Highlights

1. First Reveal of PAF1’s Role in Pancreatic Cancer Metabolic Reprogramming: This study is the first to elucidate the mechanism by which PAF1 regulates LDHA expression through HIF1α, revealing its key role in the glycolytic metabolism of pancreatic cancer.
2. Specific Interaction of the PAF1/HIF1α Complex: The study confirmed the specific interaction between PAF1 and HIF1α in pancreatic cancer cells, providing a new perspective for understanding metabolic regulation in pancreatic cancer.
3. Potential Clinical Application: The discovery of the PAF1/HIF1α axis provides a new potential target for pancreatic cancer treatment. In the future, inhibiting this axis may block the metabolic reprogramming of pancreatic cancer, thereby suppressing tumor growth.

Additional Valuable Information

This study also provides detailed experimental methods and data analysis processes, including shRNA knockdown, co-immunoprecipitation, and ChIP experiments, offering important references for subsequent research. Additionally, the research team validated the experimental results using multiple cell lines and tissue samples, ensuring the reliability and generalizability of the study.