Our Team

Our current members

The power of the Challen Lab is to gather unique individuals from all over the world sharing the same passion for improving the lives of patients afflicted with hematopoietic disorders.

Won Kyun Koh

Graduate Student, DBBS

Won was a PhD student from December 2016 – May 2022 in the Challen Lab. His thesis project revolved around investigating the potential non-canonical roles of DNMT3A in the hematopoietic stem cell function through the use of conditional genetic mouse models. This project has a novelty in providing tools to study the catalytic mutations of DNMT3A in hematopoiesis in vivo with the long-term implications of better understanding the DNMT3A molecular mechanisms in stem cell biology.  

Christine Zhang, PhD

Post Doctoral Research Associate

Christine was conferred with a PhD degree in Epigenetics and Neuroscience from University of Queensland, 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. 

Sammi Burkart

Lab Manager

Sammi received her BS in Biotechnology from Missouri Baptist University in 2013 and complete her Masters of Biology from Washington University St. Louis in 2020. Following undergrad, she spent time in industry with Eurofins Pharma working on clinical trial drug testing before returning to academia in 2017 as a Researcher Technician in Dr. Todd Druley’s lab at Washington University working on pediatric oncology. She later joined the Challen Lab in December of 2018 to assume the role of Lab Manager. In her free time, Sammi enjoys playing softball and doing CrossFit. spending time with family and friends, listening to country music, and cooking.  

Tyler Parsons, PhD

Post Doctoral Research Associate

Tyler completed his PhD work at Oakland University and the Beaumont Research Institute in Michigan where he targeted blood stem cell lineages which showed propensity to aid in solid tumor growth by utilizing a small molecule inhibitor given in conjunction with hyper-fractionated, photonic radiation. His work is currently being built upon for the launch of a clinical trial. Now, a postdoctoral research scientist in the Challen Lab, Tyler is investigating bone marrow clonal hematopoiesis and the genetic mutations which drive the poorly understood transformation of chronic, JAK2-mutant myeloproliferative neoplasms into secondary acute myeloid leukemia. 

His career goals include translating complex, clinically relevant discoveries at the bench into understandable, tangible science to reach a broader audience for the ultimate purpose of clinical application and improving patient outcomes. Tyler serves on various outreach/policy committees and organizations on and off campus as a postdoc representative for WashU. In his free time, Tyler enjoys cooking, exploring the city and parks with his two dogs, and all things sports.

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.

Aishwarya Krishnan

Graduate Student — Cancer Biology, DBBS

Aishwarya received her B.E. degree in Biotechnology from Ramaiah Institute of Technology in Bangalore, India following which she moved to the US to pursue her Master’s in Medical Biotechnology at the University of Illinois, Chicago. Following graduation, she worked as a Research Technician in Dr. Ross Levine’s lab at Memorial Sloan Kettering Cancer Center, with a focus on preclinical murine modeling and the study of novel therapeutic agents towards treatment of Myeloproliferative Neoplasms (MPN) and Acute Myeloid Leukemia (AML). Aishwarya was accepted into the Cancer Biology PhD program at Washington University in St. Louis, where she rotated in the Challen lab and joined soon after.  

Outside of lab, Aishwarya is a part of the Women in STEM group at WashU, a Potterhead, a Pure Barre addict, loves to read, hangs out with friends and is constantly figuring out how to successfully adult.

Wangisa "Wangi" Dunuwille, PhD

Post Doctoral Research Associate

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.

Andrew Young, MD PhD.

Post Doctoral Research Associate

Andrew is fascinated by clonal evolution and understanding why we get cancer. During his MD/PhD training in Todd Druley’s lab at WashU, he developed methods for rare somatic mutation detection. This led to the discovery that clonal hematopoiesis—ostensibly healthy hematopoietic cells harboring leukemia-associated mutations in disease-free individuals—was a ubiquitous phenomenon by middle age. Andrew continued internal medicine residency and hematology/oncology fellowship training at WashU and Barnes Jewish Hospital. Andrew joined the Challen Lab as a postdoc to study clonal hematopoiesis and develop tools for detecting occult malignancy. Outside of lab he enjoys wood splitting, birdwatching and parenting. 

Nancy Issa, M.D.

Research Technician II

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.

Wentao Han

Graduate Student, DBBS

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.

Infencia Xavier Raj

Graduate Student — Cancer Biology Program

Originally from Chennai, India. Graduated undergrad and masters from India. Worked as a Research Scholar in University of Washington, Seattle.  Joined Challen lab in 2022 after my rotation. 

Outside lab I enjoy hiking, reading books and Barre classes. Love trying new foods and not a fan of Beer. 

Proud Hufflepuff!

Jason Arand

Research Technician II

Laboratory Technician with 19 years of animal experience, 11 years in laboratory setting.  

Joined Dr. Challen’s lab in July of 2021.  Hobbies include basketball, golf, biking, and hiking.

Our alumni

Thanks to our alumni, the lab is where it is today. 

Hamza Celik, PhD

Hamza joined the Challen Lab as a post-doctoral research fellow in December of 2013. He quickly became an integral part of the lab, mentoring countless students and peers during his seven year tenure with the lab. His research focused on the functional characterization of tumor suppressors in leukemic transformation of chronic myeloid malignancies through the use of novel mouse models that have many features of human blood diseases. In December 2020, Hamza joined Incyte Research Institute in Wilmington, DE, as a principal investigator.

Beth Ostrander, PhD

Beth joined the Challen Lab as a graduate research assistant after entering Washington University’s graduate program in 2013. Beth’s research focused on the roles of mutated epigenetic modifiers such as Dnmt3a and Tet2 in clonal hematopoiesis and leukemogenesis. Beth earned her PhD in November 2019 and moved on to join fellow Challen Lab alum Cates Mallaney at PierianDx as a Clinical Genomics Specialist.

Andy Martens

As one of the original hires of the Challen Lab, Andy assisted Grant in building the foundation of the lab. He served as Lab Manager for seven years beginning in March of 2012 until accepting a position with the biotech company Wugen in January of 2019.

Casey Wilson, PhD

Casey joined the Challen Lab in September of 2016. His research investigated the role of epigenetic regulation in adult and pediatric T-cell Leukemia. He completed his tenure with the lab in April of 2018 before joining Arch Oncology as a Research Scientist.

Cates Mallaney, PhD

Cates joined the Challen Lab as a PhD candidate in August of 2012. Her work in the lab centered around the effects of histone modifiers in hematopoietic stem cell fate decisions and leukemogenisis. After completing her PhD in September of 2018, she accepted a position with PieranDx as a Clinical Genome Director.

Ashley Kramer

Ashley was a member of the lab from 2015 until her entrance into medical school in 2017.

Ethan Krug

Ethan joined the Challen Lab in January of 2020 after completing his BA in Film Media Studies at Washington University in St. Louis. Ethan’s primary role in the lab was assisting Dr. Hamza Celik with a various projects, including developing a humanized model for myelofibrosis. Ethan was a Challen Lab member throughout 2020 until his fall admission to New York Medical College.

Alok Kothari

Alok was a member of the lab from 2013 until 2015.

Ryan Rees

Ryan was a member of the lab from 2013 until his entrance into medical school in 2015.

John Nikitas

John was a member of the lab from 2013 to 2016.

Join Our Team

Challen Lab actively recruits motivated and enthusiastic post-docs, Ph.D. students and technicians to work and assist on projects related to stem cells, epigenetics and leukemia research!

Challen Lab trainees have a 100% success rate for acquiring awards and fellowships!

Please send CV/resume, references, and research statements to Dr. Grant Challen