Aberrant Myelopoiesis and Haematopoietic Stem Cell Niche Remodelling Precedes Cancer Cachexia Onset in a Sex-Dependent Manner.

Abstract

Background: Male cancer patients are 30% more likely to develop cachexia compared to females; however, the underlying aetiology remains unknown. Myelopoiesis induces inflammation in cancer cachexia, which contributes to muscle atrophy. Whether differences in myelopoiesis during cancer cachexia initiation contribute to sex-based differences in cachexia incidence remains unknown.

Methods: Male and female C57BL/6 and B6(C)-Ccr2^tm1.1Cln/J mice were randomized into sham (PBS) or were inoculated subcutaneously with Lewis lung carcinoma (LLC) to induce cachexia. Mice were sacrificed 2 (14 days), 2.5 (17 days) and 3.5 weeks (24 days) post-inoculation. Changes in body composition, haematopoietic stem and progenitor cells (HSPCs), myeloid immune cell migration, bone marrow niche cellular dynamics and CCL2 expression were assessed.

Results: LLC inoculation reduced tumour-free body weight, lean mass, gastrocnemius-soleus mass and myofiber cross-sectional area (CSA) in males at 3.5 weeks (p < 0.05), while females maintained tumour-free body weight, lean mass and CSA. Within the bone marrow, haematopoietic stem cells (HSCs) were increased at 2, 2.5 and 3.5 weeks compared to sham in males and at 2.5 weeks compared to 2 and 3.5 weeks in females (p < 0.05). Multipotent progenitors (MPPs) were significantly increased at 2, 2.5 and 3.5 weeks compared to sham in males and at 2.5 weeks compared to sham, 2 and 3.5 weeks in females (p < 0.05). Downstream, common myeloid progenitors (CMPs) and granulocyte-monocyte progenitors (GMPs) were elevated in males at 2.5 weeks, with CCR2⁺GMPs peaking at 2.5 weeks in males and 3.5 weeks in females (p < 0.05). Sex differences in HSC niche composition were also observed with osteoprogenitors, osteoblasts and endothelial cells increased at 2 weeks in males, while females showed increased osteoprogenitors and endothelial progenitors at 2.5 weeks in tumour-bearing mice (p < 0.05). Plasma C-C motif chemokine ligand 2 (CCL2) concentrations increased with tumour progression in both sexes; however, CCR2⁺-progenitors and macrophages were decreased at 2.5 and 3.5 weeks compared to 2 weeks (p < 0.05). In skeletal muscle, CCL2 concentration increased at 3.5 weeks, and the proportion of CCR2⁺/CD206^- macrophages increased, while total macrophage abundance remained unchanged (p < 0.05). Macrophage subpopulations were related to decreasing CSA in males but not females.

Conclusion: Our study suggests that aberrant myelopoiesis and sex-specific HSC niche remodelling precede muscle atrophy during cachexia development in males. These findings provide an important first step in understanding the role aberrant myelopoiesis plays in cancer cachexia and establish myeloid skewing as a potential therapeutic target.