AUTHOR=Khalili Dilan , Mohammed Mubasher , Kunc Martin , Sindlerova Martina , Ankarklev Johan , Theopold Ulrich 

TITLE=Single-cell sequencing of tumor-associated macrophages in a Drosophila model

JOURNAL=Frontiers in Immunology

VOLUME=Volume 14 - 2023

YEAR=2023

URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2023.1243797

DOI=10.3389/fimmu.2023.1243797

ISSN=1664-3224

ABSTRACT=Tumor-associated macrophages may act to either limit or promote tumor growth, yet the molecular basis for either path is poorly characterized.We use a larval Drosophila model that expresses a dominant-active version of the Rasoncogene (Ras V12 ) to study dysplastic growth during early tumor progression. We performed singlecell RNA-sequencing of macrophage-like hemocytes to characterize these cells in tumor-compared to wild type larvae. Hemocytes included manually extracted tumor-associated-as well as circulating cells.We identified 5 distinct hemocyte clusters. In addition to Ras V12 larvae we included a tumor model where the activation of effector caspases was inhibited, mimicking an apoptosis-resistant setting. Circulating hemocytes from both tumor models differ qualitatively from control wild-type cellsthey display an enrichment for genes involved in cell division, which was confirmed using proliferation assays. Split analysis of the tumor models further reveals that proliferation is strongest in the caspase-deficient setting. Similarly, depending on the tumor model, hemocytes that attach to tumors activate different sets of immune effectorsantimicrobial peptides dominate the response against the tumor alone, while caspase inhibition induces a shift toward members of proteolytic cascades. Finally, we provide evidence for transcript transfer between hemocytes and possibly other tissues. Taken together, our data support the usefulness of Drosophila to study the response against tumors at the organismic level.