Ongoing Projects

• The frequently altered expression of metabolism genes in solid tumors such as clear cell renal cell cancer (ccRCC) has reinforced the importance of dysregulated metabolism in driving tumor expansion.  Indeed, constitutive activation of the hypoxia inducible transcription factor (HIF) through mutations in the von Hippel Lindau (VHL) tumor suppressor gene or through exposure to hypoxia, results in enhanced glucose uptake, glycolytic flux, lactate secretion and suppression of mitochondrial activity. Conversely, reactive oxygen species produced by the mitochondria stimulate HIF-dependent transcription, creating an intricate signaling loop that balances mitochondrial oxygen consumption with the cellular response to hypoxia. In addition to stimulating glycolysis while suppressing OXPHOS, hypoxia has also been demonstrated to stimulate de novo lipogenesis through reductive glutamine metabolism, although it has not yet known how this reductive glutamine metabolism contributes to lipid accumulation in solid tumors and the clear cell phenotype in ccRCC. Importantly, HIF-dependent metabolic changes have been exploited therapeutically, indicating that a more comprehensive understanding of HIF regulated metabolism may yield novel anti-cancer therapies. Oxidative metabolism, which broadly encompasses carbohydrate oxidation, glutamine oxidation, and fatty acid β-oxidation, is controlled by a number of nuclear and mitochondrial transcription factors that together promote the biogenesis and enzymatic function of mitochondria and is often found repressed in many tumors including ccRCC. Our recent studies indicate that PGC-1α is suppressed in ccRCC through a HIF-α/Dec1 transcriptional axis.  The suppression of PGC-1α in VHL-wild type renal proximal tubule cells is associated with reduced mitochondrial activity and acquisition of the clear cell (lipid and glycogen accumulation) phenotype, a histological hallmark of ccRCC.  These findings provide the first evidence linking the clear cell phenotype to multiple aspects of renal tumorigenesis and raise the potential for PGC-1α stimulation as a novel therapeutic modality in the treatment of renal cell carcinoma, and potentially other solid tumors. Our goals are to explore the molecular mechanisms governing lipid homeostasis in cancer and to characterize their contribution to tumorigenesis and identify ways that they can be therapeutically targeted. 
  
  

• A patient presents with a primary pancreatic tumor that has metastasized to the liver. The liver is completely infiltrated with metastasis, and ultimately the metastasis will prevent the liver from functioning, and death will ensue. This is a frustrating situation, because we know where the metastases are located, we can image them, and attempt to treat them with cytotoxic chemotherapy. Unfortunately, chemotherapy only inhibits the metastasis in a short-term manner, and rarely eradicates the disease.  Unlike chemotherapy, radiotherapy is highly effective in eradicating tumors, but it cannot be used to treat widespread metastasis in the liver due to normal tissue toxicity, especially at the doses of radiation needed to eliminate the metastasis. For radiotherapy to be used in such a manner, we need to develop effective radioprotectors that protect normal tissue, but not tumor tissue from radiation induced cell death. We have identified prolyl hydroxylase (PHD) inhibitors as promising agents that both stimulate erythropoiesis and protect the gastrointestinal tract from lethal doses of radiation without any effect on tumor radiosensitivity. Such agents will revolutionize the use of radiation for the treatment of metastasis, and most importantly would start to increase the long-term survival of patients with metastatic disease.  So, our big idea for the next ten years is the normal tissues from radiation-induced lethality. This is a completely different approach to the treatment of metastatic disease that is risky, but would be revolutionary.