Despite notable improvements in childhood cancer survival rates, patients with relapsed or refractory disease
face grim prospects, and childhood cancer remains the commonest cause of death from disease in children.
This program aims to tackle this issue, focusing primarily on the challenging pediatric cancer, high-risk
neuroblastoma (NB), a tumor of the sympathetic nervous system which accounts for up to 15% of childhood
cancer deaths and is the commonest solid tumor of young children. Recent research by our international
collaborative team has revealed a novel mechanism of cancer drug resistance linked to epigenetic activation of
LINE1 (L1) retrotransposons. We have provided preliminary evidence that these retrotransposons can be
effectively targeted by existing nucleoside reverse transcriptase inhibitors (NRTIs), offering a promising avenue
for repurposing these safe and effective antiviral agents as potential treatments for refractory tumors. While the
significance of retrotransposon activation has been established in various adult cancer types, a substantial
knowledge gap exists concerning its role in pediatric malignancies. Closing this gap is imperative, as controlling
retrotransposon activation with NRTIs, and potentially also with immunotherapeutic approaches, holds
substantial potential for significantly improving treatment outcomes for pediatric cancers, including refractory NB.
Our program seeks to explore the feasibility of retrobiome-targeted pharmacological and immunotherapeutic
strategies in NB. This exploration will be guided by a comprehensive assessment of retrotransposons’ activities
and their impact on tumor characteristics, in NB and also in all other solid tumors of childhood, employing a
unique and extensive range of preclinical models and clinical samples with associated comprehensive clinical
and molecular data. Our program capitalizes on a longstanding, fruitful collaboration between US and Australian
teams, drawing upon our complementary expertise in basic and translational science. We also build upon our
teams' foundational research on the epigenetic control of retrotransposons in cancer, their recognition by humoral
and T cell immunity, and the potential druggability of retrotransposon-induced malignant traits, particularly drug
resistance. Our specific aims are as follows: (SA1) to comprehensively characterize retrotransposon activity in
NB and other solid tumors of childhood, and assess its potential therapeutic and diagnostic significance, (SA2)
to investigate the impact of retrotransposon derepression on NB treatment resistance and the potential of reverse
transcriptase inhibitors to enhance refractory NB treatment outcomes in preclinical models and (SA3) to explore
immune responses to L1 retrotransposon antigens and evaluate the efficacy of anti-L1 immunotherapy in
preclinical NB models. The outcomes of the proposed program will guide the rational design of future
pharmacological and immunotherapeutic interventions for refractory NB and subsequently other poorly curable
pediatric cancers.