Project description:Skeletal muscle wasting is a devastating consequence of cancer that affects up to 80% of cancer patients and associates with reduced survival. Herein we identified the transcriptional repressor protein, Forkhead box P1 (FoxP1), as a downstream target gene of FoxO1 whose skeletal muscle expression is elevated in multiple models of cancer cachexia and in patients with cancer who exhibit cachexia. Through generation of inducible skeletal muscle-specific FoxP1 over-expressing (FoxP1iSkmTg/Tg) mice, we demonstrate that FoxP1 upregulation is sufficient to induce features of cachexia, including body and skeletal muscle wasting characterized by reduced muscle fiber cross-sectional area of type IIX/B muscle fibers. Muscles from FoxP1iSkmTg/Tg mice also showed significant muscle damage and myopathy characterized by the accumulation of p62 and cellular material-filled vesicles, the presence of centrally nucleated myofibers, and were significantly weaker than controls. In the context of cancer cachexia, blocking FoxP1 upregulation prevented the cancer-induced repression of target genes critical to muscle structural integrity and repair, including Myocyte enhancer factor 2c (Mef2c), improved muscle ultrastructure and significantly attenuated muscle fiber atrophy. We further show that the muscle wasting phenotype induced by FoxP1 required the activity of histone deacetylase (HDAC) proteins, which are well-established to cooperate with FoxP1 to mediate gene repression, and which were necessary for FoxP1-dependent repression of Mef2c. In summary, we identify FoxP1 as a negative transcriptional regulator of skeletal muscle mass and function, whose up-regulation mediates cancer-induced muscle wasting. We used microarrays to investigate the genome-wide transcriptional networks regulated by the FoxO1 and FoxP1 transcription factors in skeletal muscle of tumor-bearing mice.
Project description:Skeletal muscle wasting is commonly associated with chronic kidney disease (CKD), resulting in increased morbidity and mortality. However, the link between kidney and muscle function remains poorly understood. Here, we took a complementary interorgan approach to investigate skeletal muscle wasting in CKD. We identified an increased production and elevated blood levels of soluble pro-cachectic factor Activin A, directly linking experimental and human CKD to skeletal muscle wasting programs. Systemic pharmacological blockade of Activin A using soluble activin receptor type IIB ligand trap prevented muscle wasting in a mouse model of experimental CKD.
Project description:Skeletal muscle wasting is commonly associated with chronic kidney disease (CKD), resulting in increased morbidity and mortality. However, the link between kidney and muscle function remains poorly understood. Here, we took a complementary interorgan approach to investigate skeletal muscle wasting in CKD. We identified an increased production and elevated blood levels of soluble pro-cachectic factor Activin A, directly linking experimental and human CKD to skeletal muscle wasting programs. Single cell sequencing data identified the expression of Activin A in specific kidney cell populations, namely a subpopulation of fibroblasts and cells of the juxtaglomerular apparatus. Based on our findings, we propose that persistent and increased kidney production of pro-cachectic factors combined with a lack of kidney clearance facilitate a vicious signalling kidney-muscle cycle, leading to exacerbated blood accumulation of Activin A, and thereby skeletal muscle wasting in CKD.
Project description:Investigating muscle wasting in a murine model of cancer cachexia, we identified Oncostatin M (OSM) as a potential mediator of inflammatory responses in skeletal muscle. OSM is a member of the IL-6 family of cytokines and has crucial functions in cell growth, differentiation, and inflammation. Our results demonstrate that OSM induces muscle atrophy. To understand if its effect is specific or it is a general effect of IL6 family cytokines, primary myotubes were treated with OSM, IL6 and LIF for 48hrs. Our findings showed that OSM potently induces muscle wasting in differentiated myotubes.
Project description:Cancer-induced muscle wasting reduces quality of life, complicates or precludes cancer treatments, and predicts early mortality. Herein, we investigated the requirement of the muscle-specific E3 ubiquitin ligase, MuRF1, for muscle wasting induced by pancreatic cancer. Murine pancreatic cancer (KPC) cells, or saline, were injected into the pancreas of WT and MuRF1-/- mice, and tissues analyzed throughout tumor progression. KPC tumors induced progressive wasting of skeletal muscle and systemic metabolic reprogramming in WT mice, but not MuRF1-/- mice. KPC tumors from MuRF1-/- mice also grew slower, and showed an accumulation of metabolites normally depleted by rapidly growing tumors. Mechanistically, MuRF1 was necessary for the KPC-induced increases in cytoskeletal and muscle contractile protein ubiquitination, and the depression of proteins that support protein synthesis. Together, these data demonstrate that MuRF1 is required for KPC-induced skeletal muscle wasting, whose deletion reprograms the systemic and tumor metabolome and delays tumor growth.
Project description:Cancer-induced muscle wasting reduces quality of life, complicates or precludes cancer treatments, and predicts early mortality. Herein, we investigated the requirement of the muscle-specific E3 ubiquitin ligase, MuRF1, for muscle wasting induced by pancreatic cancer. Murine pancreatic cancer (KPC) cells, or saline, were injected into the pancreas of WT and MuRF1-/- mice, and tissues analyzed throughout tumor progression. KPC tumors induced progressive wasting of skeletal muscle and systemic metabolic reprogramming in WT mice, but not MuRF1-/- mice. KPC tumors from MuRF1-/- mice also grew slower, and showed an accumulation of metabolites normally depleted by rapidly growing tumors. Mechanistically, MuRF1 was necessary for the KPC-induced increases in cytoskeletal and muscle contractile protein ubiquitination, and the depression of proteins that support protein synthesis. Together, these data demonstrate that MuRF1 is required for KPC-induced skeletal muscle wasting, whose deletion reprograms the systemic and tumor metabolome and delays tumor growth.
Project description:Skeletal muscle wasting is a debilitating condition that occurs with aging and with many diseases, but the underlying mechanisms are incompletely understood. Previous work determined that common transcriptional changes occur in skeletal muscle during atrophy induced by different stimuli. However, whether this holds true at the proteome level remains largely unexplored. Here, we find that, contrary to this earlier model, distinct atrophic stimuli (corticosteroids, cancer, and aging) induce largely different mRNA and protein changes during muscle wasting in mice. Moreover, there is widespread transcriptome-proteome disconnect. Consequently, atrophy markers (atrogenes) identified in earlier microarray-based studies do not emerge from these proteomic surveys as the most relevantly associated with atrophy. Based on these analyses, we identify atrophy-regulated proteins (here defined as “atroproteins”) such as the myokine CCN1/Cyr61, which we find regulates myofiber type switching during sarcopenia. Altogether, these integrated analyses indicate that different catabolic stimuli induce muscle wasting via largely distinct mechanisms.
Project description:Existing data suggest that NF-kappaB signaling is a key regulator of cancer-induced skeletal muscle wasting. However, identification of the components of this signaling pathway and of the NF-κB transcription factors that regulate wasting is far from complete. In muscles of C26 tumor bearing mice, overexpression of d.n. IKKβ blocked muscle wasting by 69%, the IκBα-super repressor blocked wasting by 41%. In contrast, overexpression of d.n. IKKα or d.n. NIK did not block C26-induced wasting. Surprisingly, overexpression of d.n. p65 or d.n. c-Rel did not significantly block muscle wasting. Genome-wide mRNA expression arrays showed upregulation of many genes previously implicated in muscle atrophy. To test if these upregulated genes were direct targets of NF-κB transcription factors, we compared genome-wide p65 or p50 binding to DNA in control and cachectic muscle using ChIP-sequencing. Bioinformatic analysis of ChIP-seq data from control and C26 muscles showed increased p65 and p50 binding to a few regulatory and structural genes but only two of these genes were upregulated with atrophy. The p65 and p50 ChIP-seq data are consistent with our finding of no significant change in protein binding to an NF-κB oligo in a gel shift assay. Taken together, these data support the idea that although inhibition of IκBα, and particularly IKKβ, blocks cancer-induced wasting, the alternative NF-κB signaling pathway is not required. In addition, the downstream NF-κB transcription factors do not regulate the transcriptional changes. These data are consistent with the growing body of literature showing that there are NF-κB-independent substrates of IKKβ and IκBα that regulate physiological processes.