Won "One" Kyun Koh

Graduate Student, DBBS

Seoul, South Korea

Won earned a BS in Biology and a BA in Japanese at the University of Texas at Austin. Following undergrad, Won earned a Master’s in Biochemistry and Cell Biology at Stony Brook University. After completing his MS, Won came to Washington University as a Research Technician in Zhongsheng You's lab. He later joined the PhD program where he rotated with Dr. Challen’s lab and subsequently joined in December of 2016. Won’s work in the lab centers around the potential non-canonical roles of DNMT3A in the hematopoietic stem cell function through the use of conditional genetic mouse models. His long term goal is to identify molecular mechanisms and genetic players that regulate stem cell biology, which could have implications on the early diagnosis of leukemia as well as improved treatments. When Won is away from the lab, he enjoys working out, playing tennis, reading, going to the whiskey bar with friends, and indulging in Mission Taco's late night $2 tacos.

Jake Fairchild

Research Technician II

St. Louis, MO, USA

Jake received his BS in Biology with emphasis in Ecology and Evolution from Lindenwood University – St. Charles in 2018. His studies focused on understanding and exploring the mechanisms of evolution. Following graduation, Jake joined the Challen Lab as a Research Technician in October of 2018. Jake's primary responsibilities include maintaining the Challen Lab mouse colony and assisting rotation students, PhD candidates, and postdoctoral research fellows with various lab research projects. Outside of work, Jake enjoys playing golf and guitar.

Nancy Issa, M.D.

Research Technician II

Koura, Lebanon

Nancy received her medical degree from the American University of Beirut. Following medical school, she sought to gain experience in basic research prior to applying for a residency position, which brought her to the Challen Lab in July of 2019. Nancy has since developed a passion for research while exploring the genetic drivers of T-ALL and searching for molecular drug targets that may help improve the prognosis and quality of life in T-ALL patients. After building a good foundation in basic research, Nancy hopes to improve her clinical journey by implementing her research skills to a residency position in Internal Medicine.

Sammi Burkart

Lab Manager

St. Louis, MO, USA

Sammi received her BS in Biotechnology from Missouri Baptist University in 2013. Following undergrad, she spent time in industry with Eurofins Pharma before returning to academia in 2017 as a Research Technician in Dr. Todd Druley's lab at Washington University. She later joined the Challen Lab in December of 2018 to assume the role of Lab Manager. Sammi is currently working towards her Masters in Biology at Washington University. In her free time, Sammi enjoys softball and crossfit, spending time with family and friends, country music, and sushi.

Christine Zhang, PhD

Post Doctoral Research Associate

Brisbane, Australia

Christine was conferred with a PhD degree in Epigenetics and Neuroscience from University of Queensland in 2014, for her enthusiasm in exploring the fundamental mechanism of suboptimal heath conditions. As a budding scientist, Christine is passionate about translating the understanding of the genetics and epigenetics of cancers (such as hematopoietic malignancies) into clinic to improve wellbeing through personalized medicine. Her current research is to dissect the role of inflammatory responses in clonal hematopoiesis and leukemogenesis.

Wangisa "Wangi" Dunuwille, PhD

Post Doctoral Research Associate

Kandy, Sri Lanka

Wangi earned a Bachelor of Veterinarian Science and a Master's degree at the University of Peradeniya near his home town of Kandy, Sri Lanka. He then enrolled in the PhD program at the University of Kentucky. Wangi joined the Challen Lab in October of 2019 upon the completion of his PhD. His primary work in the lab is centered around investigating which mechanisms cause the subset of T-ALL with Dnmt3a inactivating mutations to be relatively more aggressive and chemotherapy resistant than other strains. Outside of work, Wangi enjoys photography and taking road trips.

Hassan Bjeije, PhD

Post Doctoral Research Associate


Hassan came to the Challen Lab in February of 2020 after completing his PhD in Molecular Genetics at Tarbiat Modares University in Iran. Hassan is working to build on the lab’s previous studies showing that Jarid2 functions as a tumor suppressor in myeloid neoplasms by repressing self-renewal in hematopoietic progenitor cells. The overall aim of the current study is to unravel the molecular mechanisms through which Jarid2 controls the self-renewal process in normal and malignant hematopoietic progenitor cells. Hassan will use innovative techniques that specifically identify Jarid2 functional domains, Jarid2 interacting proteins, and negative regulators of Jarid2 gene expression with the aim to elucidate novel therapeutic strategies for MPN/sAML patients. When Hassan is not working in the lab, he enjoys cooking, billiards, working out, and reading novels.

Jacob Tao

Undergraduate Research Assistant

San Diego, CA, USA

Jacob is an undergraduate student at Washington University studying Molecular Biology and Biochemistry. He joined the Challen Lab in January 2018 prompted by his interest in leukemia and lymphoma research. Jacob's research interests include the role of Dnmt3a as an epigenetic regulator in normal and malignant hematopoiesis. His goal is to better understand how mutations in Dnmt3a can affect the development of hematopoietic malignancies and to research its role in regulating DNA methylation. Jacob hopes to contribute to future potential treatment methods. Following his undergraduate degree, Jacob plans to attend medical school.

Wentao Han

Graduate Student, DBBS

Luoyang, China

Wentao earned his BS in Biological Sciences from Beijing Forestry University in Beijing, China. He then enrolled in Washington University in St. Louis' MCB Graduate Program. Wentao first came to Challen Lab as a rotation student in February of 2019 and subsequently joined the lab soon after. Wentao's research is centered around the balance between cell differentiation and self renewal for ex vivo hematopoietic stem cell expansion.

Anneliese Ceisel

Undergraduate Research Assistant

Kenosha, WI, USA

Anneliese is an undergraduate student at Washington University. She is double majoring in Computational Biology and Spanish. She joined the Challen Lab in the summer of 2018 while participating in Washington University’s uSTAR Summer Scholars Program. Currently, Anneliese works under the guidance of Dr. Hamza Celik on the functional characterization of tumor suppressors involved in normal and malignant hematopoiesis. She also aids in various experiments around the Challen Lab. Following undergrad, Anneliese plans to pursue a PhD in stem cell research.

Ostap Kukhar

Research Technician I

Bettendorf, IA, USA

Ostap joined the Challen Lab in August of 2020 shortly after completing his double major in Biology and Economics at Washington University in St. Louis. Currently, he assists Dr. Hamza Celik with primary myelofibrosis research, which includes preclinical drug trials and developing a humanized mouse model. Outside the lab, Ostap enjoys soccer, hiking, and trying new restaurants.