What type of study is this?

This is a Single-nucleus RNA-seq study (also classified as: Bulk RNA-seq).

September 10, 2025

Pancreatic Cancer Induces Population-Specific Switching of Myosin Isoforms and Discrete Activation of Cachexia Genes in Skeletal Muscle Myocytes

Key Points

Cachexia induces a progressive loss of muscle differentiation factor Maf, while increasing Myh1 and Myh2 expression.
Single-nucleus RNA-seq reveals global shifts in myofiber gene expression identity and a unique myonuclear subpopulation related to cachexia.
Myo-nuclei fate occurs before muscle wasting, suggesting early cachexia gene expression differs from later stages.
Results highlight the need for targeted approaches to skeletal muscle wasting during cancer cachexia, addressing cellular population changes.

Abstract

Skeletal muscle loss in pancreatic cancer is a significant cause of morbidity and mortality for patients. In order to understand myocytes changes we examined myonuclei- and myofiber-specific dynamics during pancreatic cancer cachexia progression. Single-nucleus RNA-seq was used to interrogate myonuclear gene expression, and RNAscope and immunofluorescence characterized myofiber-specific changes. Bulk RNA-seq of skeletal muscle provided a whole-muscle transcriptomic profile. Cachexia induces a progressive loss of muscle differentiation factor Maf and its target Myh4, accompanied by increased expression of Myh1 and Myh2. This myofiber dedifferentiation occurs without evidence for fiber type shifting, regeneration, or proliferation. Single-nuclei analysis reveals global shifts in myofiber gene expression identity including the identification of a cachexia only myonuclear subpopulation. Cachexia gene expression was not restricted solely to this PDAC-specific myonuclear subpopulation and did not overlap with Myh1 and Myh2 expressing myonuclei early in cachexia. Altogether, PDAC cachexia elicits distinct transcriptional responses across different myonuclear populations. These results reveal population-specific heterogeneity in cachexia gene activation, rather than a uniform upregulation of cachexia mediators across muscle tissue. Our data suggest that myonuclei fate occurs prior to overt muscle wasting when cachexia gene expression only modestly overlaps with differentiation factors, with a strong association after irreversible muscle wasting. These findings explain the challenge of effectively targeting skeletal muscle wasting in cancer cachexia requires addressing the changing cell population induced through non overlapping mechanisms.

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