Vitamin C-induced epigenomic remodeling as a preventive therapy for leukemic transformation

Despite the overall improved diagnostics, standard of care and therapeutic options, most acute myeloid leukemia (AML) patients suffer from severe therapy-related side effects and still only 28% of them reach 5-year overall survival. The hypothesis that drives my project is that mutations which affect DNA-modifying enzymes disrupt a methylation-based control mechanism that regulates gene expression in a way that halts the normal cellular differentiation process. The discovery that vitamin C acts as an enzymatic co-factor that is able to revert this methylation defect in affected cells, provides a unique opportunity to transfer this knowledge to the development of novel, less toxic treatment strategies for patients that harbour these mutations. Within the scope of this project, I plan to explore whether and to which extent I can restore the normal DNA methylation signature in patient-derived leukemic cells in mice, either through vitamin C treatment alone or in addition to Health-Canada approved AML drugs. Further, I will explore the potential of vitamin C treatment to delay or prevent the transformation of not yet leukemic cellular states towards myeloid malignancy.

End of Award Update – August 2023

Most significant outputs

The most exciting results are yet to come: two manuscripts are currently in preparation to be submitted to Genome Biology and Leukemia within the year.

Impact

Despite the overall improved diagnostics, standard of care, and therapeutic options, most acute myeloid leukemia (AML) patients suffer from severe therapy-related side effects and only every third patient reaches 5-year overall survival. An observation that formed the foundation for this project is the frequent occurrence of mutations in AML cells which affect enzymes that contribute to a special control mechanism that regulates if and how much of a gene is read from our DNA to produce functional proteins. This control mechanism involves the precise placement and removal of “methylation marks” – either directly on top of the DNA strands or at proteins that help to organize the DNA into the three-dimensional structure we call chromosomes. If the placement or removal of these methylation marks is altered, protein production and cell survival mechanisms are disturbed as a consequence – a characteristic which we often observe in cancer cells. In the past, our lab contributed to the discovery that vitamin C acts as a co-factor that helps to re-activate the enzymes that deposit and remove methylation marks, even despite their mutations. Thus, treating affected AML cells with vitamin C can help to revert their methylation defect, which directs their gene expression to a healthier state and causes cancer cells to die under controlled laboratory conditions. As vitamin C is a non-toxic, well-tolerated, widely available, and cost-effective substance, its potential anti-cancer effect provided us with a unique opportunity to test whether this knowledge could be translated into effective but less toxic alternative treatment strategies for AML patients who harbour these mutations.

Within the scope of this Health Research BC and Lotte and John Hecht Foundation co-funded project, we have created murine leukemia model systems that allowed us to confirm the vitamin C anti-leukemic effect in living organisms. Interestingly, while studying these models more deeply, we observed that not all cells within a pool of leukemia cells responded equally to vitamin C – whereas most cells matured and died, there seemed to be some cells that were able to survive the treatment despite carrying the same disease-initiating mutations. This observation directly impacts the potential to utilize vitamin C in a therapeutic setting, arguing that even among AML cases that display the same disease-driving genetic abnormalities, not all patients will respond to vitamin C. Also, these findings are consistent with clinical observations, where historically, vitamin C was reported to be both highly effective and not effective at all in a series of trials in the 1970’s and 80’s that assessed the activity of vitamin C against terminal stage solid cancers.

Potential Influence

In the remaining months of finalizing this project, we are focusing on identifying what makes some cells sensitive and others tolerant to vitamin C, despite the presence of the same disease-driving mutations. Therefore, we have selected individual cells from a pool of mutation-positive AML cells which display the ability to produce a leukemia-like myeloid cell hierarchy in a culture dish. Through repeated treatment and testing, we could identify both model hierarchies that repeatedly tolerated or succumbed to the presence of vitamin C. As each cell within a model hierarchy stem from a single ancestor cell, we hypothesize that it is the maturation state of the ancestor cell – in combination with the present mutations – that mediates the observed differential vitamin C responsiveness. Further, we argue that we will be able to observe this difference in maturation state in a cell or a hierarchy’s DNA methylation patterns. We are working to confirm this hypothesis to define a diagnostic molecular signature (a so-called biomarker) that might help decide which AML patients can benefit from vitamin C in a clinical setting.

Next Steps

This research will be continued in the Hirst lab; however, I will move on to a new position soon as the time I am allowed to work as a postdoctoral fellow in Canada is coming to an end