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Treatment of pediatric leukaemia often involves the use of high doses of anthracyclines, which results in severe side-effects including cardiotoxicity and the development of secondary cancers. Based on previous studies showing that anthracyclines such as doxorubicin (DXR) can target therapy-resistant leukemia stem cells (LSCs) at low, generally non-toxic doses, we repurposed DXR as a targeted inhibitor rather than a broadly cytotoxic chemotherapy. In contrast to typical clinical usage, low-dose DXR treatment reduces expression of multiple immune checkpoint (IC) inhibitors, which exposes LSCs to elimination by cytotoxic T lymphocytes. In the laboratory, anthracyclines can also stimulate immunogenic cell stress/death (ICD). Unlike other forms of cellular death, ICD can induce an anti-cancer immune response, effectively immunizing against cancer recurrence. Unfortunately, this effect is generally not observed in the clinic possibly due to the high-dose, and thus immunosuppressive nature of current treatment regimens. Indeed, our data indicates this is due to fundamentally unique gene expression programs induced by high vs. low doses.

Here, we will test the hypothesis, supported by preliminary data, that low to intermediate DXR exposure reduces IC expression and initiates stress-inducing ICD, respectively. Thus, discovering genes that inhibit or synergize with IC suppression and ICD induction will identify targets that can be activated or inhibited to enhance clinical efficacy of anthracyclines and other ICD-inducers at low concentrations that are not toxic to healthy tissues. Utilizing CRISPR-Cas9 gene editing technology we have developed whole genome screens to construct and validate a chemical-genetic strategy for investigating the effects of differential doses of doxorubicin on leukemia cells for identifying IC suppressors/ICD inducers. Ultimately, this project will reveal novel therapeutic strategies for harnessing the immune system to enhance and potentiate the ICD response of low-dose DXR treatment, thus providing durable, less toxic cures for pediatric cancer.

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Development Of Whole-Genome CRISPR-CAS9 Screens To Discover Novel Immunotherapy Targets In Pediatric Leukaemia