Incubating Progress: Talent + Technology + Teamwork

Cancer Center chemists discover, develop new approach that holds promise in treating kidney tumors


High-throughput screening

Under normal conditions, hypoxia-inducible factors, or HIFs, allow the body’s cells to thrive in low-oxygen environments, such as high altitudes. By responding to changes in oxygen levels, HIFs serve as master regulators, determining whether multiple genes that help healthy cells survive and reproduce are activated downstream. But this mechanism also promotes growth and survival of cancer cells.

HIFs accumulate and drive these other genes when the von Hippel-Lindau (VHL) gene—normally a tumor suppressor that breaks HIFs down—is inactivated. This loss of VHL leads to the most common type of kidney cancer, renal clear cell carcinoma.

At UT Southwestern, fundamental studies into one type of HIF, called HIF-2, have blossomed into a promising potential treatment.

The Foundations

1997: UT Southwestern biochemist Steven McKnight, Ph.D., and molecular geneticist David Russell, Ph.D., lead research discovering and describing the protein encoded by the EPAS-1 gene, also known as HIF-2α. Additional research at UT Southwestern sheds more light on the workings of the HIF family and related molecules, especially HIF-2α.

Dr. Richard Bruick
Richard Bruick, Ph.D.

2000–2009: Over the course of a decade, the laboratories of Drs. Richard Bruick and Kevin Gardner tease apart the structure of HIF-2. Biochemical analysis reveals how HIF-2α docks with another protein to assemble into a functional HIF-2 complex, and how mutations that disrupt this binding halt HIF-2 activity. Finding drug-like chemicals that can likewise disrupt HIF binding holds the promise of impairing various downstream cancer-promoting targets, such as the VEGF receptor.

2009: The Bruick-Gardner research reveals a cavity within the HIF-2α protein that is a potential “sweet spot” where disrupters may bind and shut down HIF-2 activity.

The Translation

20072008: After gleaning insights from earlier, more focused screens, scientists deploying the Cancer Center’s High-Throughput Screening shared resource systematically test more than 200,000 drug-like molecules, one at a time, to see which ones might interfere with HIF-2. The effort identifies a slate of successful compounds.

20082013: Medicinal chemists at Simmons Cancer Center study the HIF-2 disrupters, learning more about how they work and refining the most promising of these compounds to increase their potency and improve their safety profile.

Dr. Kevin Gardner
Kevin Gardner, Ph.D. (CUNY/photo)

2013: UT Southwestern scientists including Drs. Bruick, Gardner, John MacMillan, and Uttam Tambar detail how chemicals bind with the “sweet spot” cavity to disrupt HIF-2 function. The findings indicate that small molecules can feasibly regulate HIF-2α, a type of molecule previously considered “undruggable.”

2013: Research shows that the newly discovered and refined compounds can block the assembly of the HIF-2 complex and disrupt its function in living cells originating from actual human tumors—rendering HIF-2 unable to turn on other cancer-related genes.

The Impact

2011: The most promising compounds are licensed to Peloton Therapeutics, a biotech firm co-founded by Dr. McKnight and based in new, state-of-the-art facilities on UT Southwestern’s BioCenter campus.

2014: The first HIF-2 inhibitor in clinical development, an oral drug known as PT2385, enters a phase I clinical trial for safety and dosing in patients with advanced or metastatic renal clear cell carcinoma. Kevin Courtney, M.D., Ph.D., heads the trial at UT Southwestern, one of six sites across the U.S. testing the drug.

BioCenter at UT Southwestern Medical Center
BioCenter at UT Southwestern Medical Center

The Future

A mouse model of human renal clear cell carcinomas, developed and validated by UT Southwestern kidney cancer specialist James Brugarolas, M.D., Ph.D., and colleagues, may provide insights into which patients are most likely to benefit from treatment with HIF-2 inhibitors.

HIF-2 also appears significant in other types of cancer, including deadly brain cancers called glioblastomas and non-small cell lung cancer, the most common type of lung malignancy.

Key Publications

Tian, H. et al. Endothelial PAS domain protein 1 (EPAS1), a transcription factor selectively expressed in endothelial cells. Genes Dev 11, 72-82 (1997).

Erbel, P.J. et al. Structural basis for PAS domain heterodimerization in the basic helix-loop-helix-PAS transcription factor hypoxia-inducible factor. Proc Natl Acad Sci U S A 100, 15504-09 (2003).

Yang, J. et al. Functions of the Per/ARNT/Sim domains of the hypoxia-inducible factor. J Biol Chem 280, 36047-54 (2005).

Scheuermann, T.H. et al. Artificial ligand binding within the HIF2alpha PAS-B domain of the HIF2 transcription factor. Proc Natl Acad Sci U S A 106, 450-55 (2009).

Scheuermann, T.H. et al. Allosteric inhibition of hypoxia inducible factor-2 with small molecules. Nat Chem Biol 9, 271-76 (2013).

Rogers, J.L. et al. Development of inhibitors of the PAS-B domain of the HIF-2alpha; transcription factor. Journal of Medicinal Chemistry 56, 1739-47 (2013).