Leukemic stem cells (LSCs) comprise a rare subpopulation of acute myeloid leukemia (AML) cells that possess extraordinary self-renewal and tumourigenic potential. Their unique ability to sustain tumour growth makes them an attractive target for the development of novel anticancer drugs. However, discerning the effects of perturbations on the LSC subpopulation relative to other more abundant tumour cell types can be challenging.
In a new study published in Blood Cancer Discovery, Dr. Ana Vujovic and colleagues at the University of Toronto and the University of California, San Diego deployed an innovative two-step in vivo CRISPR-Cas9-based serial transplantation screen to identify RNA-binding proteins that are required for LSC function. They uncovered a critical role for the RNA-stabilizing factor ELAVL1 in LSCs and demonstrated that inhibition of its function leads to a host of molecular changes and a loss of stem cell properties.
Rising Stars invited Ana to tell us about the work behind the paper.
What is your academic background?
I completed my BSc in Biochemistry and Biomedical Sciences at McMaster University. During my undergraduate degree I had the privilege of performing research in the lab of Dr. Kristin Hope for the last two years of my degree, where I primarily focused on investigating the biology of hematopoietic stem cells. It was during my first year in Kristin’s lab that I knew I wanted to pursue graduate studies in her lab focusing on stem cell and leukemia research. In 2017, I began my MSc studies in Kristin’s lab and after a year or so I transferred in to the PhD program. Just this past March I completed my PhD in the Medical Biophysics program at the University of Toronto.
What led you to focus on the role of RNA-binding proteins in leukemic stem cells?
When I joined Kristin’s lab in 2015, the research efforts in the field of AML aiming at uncovering regulators of LSCs were for the most part focused on transcriptional and epigenetic control of LSCs and there wasn’t as much known about the role that post-transcriptional circuitries play in mediating the function of LSCs. Studies from other healthy tissue and solid cancers indicated that certain RNA-binding proteins (RBPs), the core effectors of post-transcriptional control, represented key regulators of stem cell fate decision-making. In AML we found that the expression of RBPs as a class are enriched in the LSC-enriched fraction of human AML compared to the LSC-depleted fraction, which prompted us to further investigate these proteins in the context of LSC function.
What was the biggest challenge you encountered during the course of this study?
One major challenge in this study was performing the xenotransplantations of lentivirally-infected AML cells. In addition to the intrinsic heterogeneity between AML patient specimens, the infectability and engrafting potential of AML cells greatly varies across samples and so successful transplantation of a lentivirally-infected LSC, which is already an extremely rare subpopulation among the bulk cells in any given patient sample, was even more difficult. Another PhD student and I spent some time optimizing the vector system and lentivirus production approach that allowed for reproducibly high levels of infection across distinct AML patient specimens, which was integral in validating our findings in a clinically relevant human AML setting.
What were the most important lessons you learned while performing this study?
One of the important lessons I’ve learned is to stay persistent and focused on the main goal of the project. Technical challenges and troubleshooting are often perceived as roadblocks preventing progress, but ultimately this time spent on problem solving through these issues greatly pays off in the end. Working through and overcoming these kinds of challenges has ultimately led to some important and exciting findings in our study so it really is a rewarding feeling.
What was the most exciting moment you experienced while pursuing this work?
I would say there were several moments of excitement throughout the course of this work. From gathering data into figures after weeks long animal experiments to putting all the pieces of the paper together and seeing it published. There have been different milestones throughout the process that have been exciting in their own way. I think just seeing everything come together in its final form and being able to share it online has been super exciting!
What are your career plans, now that you have completed your PhD?
I just recently joined Dr. Craig Jordan’s lab in Colorado as a post-doctoral researcher, where I will be continuing research in AML stem cells and metabolism. My long-term goal is to ultimately have an independent lab in academic research.
Story contributed by:
Andrew O. Giacomelli, Ph.D.
Postdoctoral Researcher, Princess Margaret Cancer Centre, University Health Network
Delegate, Ontario Rising Stars in Cancer Research Network, Ontario Institute for Cancer Research