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Updated: Jul 15, 2025
The Drosophila Imaginal Disc Tumor Model: Visualization and Quantification of Gene Expression and Tumor Invasiveness Using Genetic Mosaics
Published on: October 6, 2016
Single-cell sequencing of tumor-associated macrophages in a Drosophila model
Dilan Khalili1, Mubasher Mohammed1, Martin Kunc1,2
1The Wenner-Gren Institute, Department of Molecular Biosciences, Stockholm University, Stockholm, Sweden.
Introduction:
Tumor-associated macrophages may act to either limit or promote tumor growth, yet the molecular basis for either path is poorly characterized.
Methods:
We use a larval Drosophila model that expresses a dominant-active version of the Ras-oncogene (RasV12) to study dysplastic growth during early tumor progression. We performed single-cell RNA-sequencing of macrophage-like hemocytes to characterize these cells in tumor- compared to wild-type larvae. Hemocytes included manually extracted tumor-associated- and circulating cells.
Results And Discussion:
We identified five distinct hemocyte clusters. In addition to RasV12 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 cells-they 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 effectors-antimicrobial 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.
Insights
This study reveals that tumor-associated macrophages in Drosophila larvae exhibit distinct behaviors, with increased proliferation and altered immune responses depending on tumor characteristics. These findings highlight Drosophila as a model for studying tumor-host interactions.
Area of Science:
- * Developmental Biology
- * Immunology
- * Cancer Research
Background:
- * Tumor-associated macrophages (TAMs) play a complex role in cancer, potentially limiting or promoting tumor growth.
- * The molecular mechanisms governing TAM function remain poorly understood.
- * A larval Drosophila model offers a powerful system to investigate early tumor progression and host responses.
Purpose of the Study:
- * To characterize the molecular and functional differences of hemocytes (macrophage-like cells) in a Drosophila tumor model.
- * To investigate how Ras-oncogene activation and apoptosis resistance influence hemocyte behavior.
- * To explore the immune responses and proliferative capacity of hemocytes in response to tumors.
Main Methods:
- * Single-cell RNA-sequencing of hemocytes from RasV12-expressing Drosophila larvae and control wild-type larvae.
- * Analysis of hemocytes from a caspase-inhibited tumor model to mimic apoptosis resistance.
- * Proliferation assays and immune effector gene expression analysis.
Main Results:
- * Five distinct hemocyte clusters were identified.
- * Circulating hemocytes in tumor models showed enrichment in cell division genes, indicating increased proliferation, especially in apoptosis-resistant settings.
- * Tumor-associated hemocytes activated different immune responses, with antimicrobial peptides dominating in one model and proteolytic cascades in the caspase-inhibited model.
- * Evidence for transcript transfer between hemocytes was observed.
Conclusions:
- * Drosophila hemocytes exhibit distinct proliferative and immune responses to tumors, influenced by oncogenic signaling and apoptosis resistance.
- * The study demonstrates the utility of Drosophila as a model organism for studying tumor-host interactions at the organismal level.
- * Findings provide insights into the molecular basis of TAM heterogeneity and function in cancer progression.
