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Updated: Apr 19, 2026
The Colon-26 Carcinoma Tumor-bearing Mouse as a Model for the Study of Cancer Cachexia
Published on: November 30, 2016
Genome-wide identification of FoxO-dependent gene networks in skeletal muscle during C26 cancer cachexia
Sarah M Judge1, Chia-Ling Wu2, Adam W Beharry3
1Department of Physical Therapy, University of Florida, 1225 Center Drive, HPNP Building 1142, Gainesville, Florida, USA. smsenf@ufl.edu.
Background:
Evidence from cachectic cancer patients and animal models of cancer cachexia supports the involvement of Forkhead box O (FoxO) transcription factors in driving cancer-induced skeletal muscle wasting. However, the genome-wide gene networks and associated biological processes regulated by FoxO during cancer cachexia are unknown. We hypothesize that FoxO is a central upstream regulator of diverse gene networks in skeletal muscle during cancer that may act coordinately to promote the wasting phenotype.
Methods:
To inhibit endogenous FoxO DNA-binding, we transduced limb and diaphragm muscles of mice with AAV9 containing the cDNA for a dominant negative (d.n.) FoxO protein (or GFP control). The d.n.FoxO construct consists of only the FoxO3a DNA-binding domain that is highly homologous to that of FoxO1 and FoxO4, and which outcompetes and blocks endogenous FoxO DNA binding. Mice were subsequently inoculated with Colon-26 (C26) cells and muscles harvested 26 days later.
Results:
Blocking FoxO prevented C26-induced muscle fiber atrophy of both locomotor muscles and the diaphragm and significantly spared force deficits. This sparing of muscle size and function was associated with the differential regulation of 543 transcripts (out of 2,093) which changed in response to C26. Bioinformatics analysis of upregulated gene transcripts that required FoxO revealed enrichment of the proteasome, AP-1 and IL-6 pathways, and included several atrophy-related transcription factors, including Stat3, Fos, and Cebpb. FoxO was also necessary for the cancer-induced downregulation of several gene transcripts that were enriched for extracellular matrix and sarcomere protein-encoding genes. We validated these findings in limb muscles and the diaphragm through qRT-PCR, and further demonstrate that FoxO1 and/or FoxO3a are sufficient to increase Stat3, Fos, Cebpb, and the C/EBPβ target gene, Ubr2. Analysis of the Cebpb proximal promoter revealed two bona fide FoxO binding elements, which we further establish are necessary for Cebpb promoter activation in response to IL-6, a predominant cytokine in the C26 cancer model.
Conclusions:
These findings provide new evidence that FoxO-dependent transcription is a central node controlling diverse gene networks in skeletal muscle during cancer cachexia, and identifies novel candidate genes and networks for further investigation as causative factors in cancer-induced wasting.
Insights
Forkhead box O (FoxO) transcription factors drive cancer cachexia by regulating skeletal muscle gene networks. Blocking FoxO prevents muscle wasting and preserves muscle function in a mouse model, identifying key pathways for therapeutic intervention.
Area of Science:
- Molecular Biology
- Genetics
- Physiology
Background:
- Cancer cachexia involves skeletal muscle wasting, with Forkhead box O (FoxO) transcription factors implicated.
- The specific genome-wide gene networks and biological processes regulated by FoxO in cancer cachexia remain largely unknown.
- FoxO is hypothesized to be a central regulator of gene networks promoting muscle wasting during cancer.
Purpose of the Study:
- To investigate the genome-wide gene networks regulated by FoxO in skeletal muscle during cancer cachexia.
- To determine the role of FoxO as an upstream regulator of gene expression in cancer-induced muscle wasting.
Main Methods:
- Inhibition of endogenous FoxO DNA-binding in mouse limb and diaphragm muscles using a dominant-negative FoxO (d.n.FoxO) construct delivered via AAV9.
- Mice were inoculated with Colon-26 (C26) cancer cells, and muscles were harvested 26 days post-inoculation.
- Analysis of gene expression changes and validation through quantitative reverse transcription PCR (qRT-PCR).
Main Results:
- Blocking FoxO prevented C26-induced muscle fiber atrophy and preserved muscle force, indicating FoxO's critical role in muscle wasting.
- FoxO regulated 543 transcripts in response to C26; upregulated transcripts involved proteasome, AP-1, and IL-6 pathways, including atrophy factors Stat3, Fos, and Cebpb.
- FoxO was essential for downregulating extracellular matrix and sarcomere protein genes and directly activated Cebpb promoter via FoxO binding elements.
Conclusions:
- FoxO-dependent transcription is a central regulator of diverse gene networks in skeletal muscle during cancer cachexia.
- Identified novel candidate genes and pathways (e.g., proteasome, AP-1, IL-6, Stat3, Fos, Cebpb) involved in cancer-induced muscle wasting.
- These findings offer new targets for therapeutic strategies aimed at combating cancer cachexia.
