Project description:Background: Cancer cachexia is a life-threatening metabolic syndrome that causes significant loss of skeletal muscle mass and significantly increases mortality in cancer patients. Currently, there is an urgent need for better understanding of the molecular pathophysiology of this disease, so that effective therapies can be developed. Almost all pre-clinical studies evaluating skeletal muscle’s response to cancer have focused on one or two pre-clinical models, and almost all have focused specifically on limb muscles. In the current study, we reveal key differences in the histology and transcriptomic signatures of a limb muscle and a respiratory muscle in orthotopic pancreatic cancer patient-derived xenograft (PDX) mice. Methods: To create the four cohorts of PDX mice evaluated in this study, tumors resected from four pancreatic ductal adenocarcinoma (PDAC) patients were portioned and attached to the pancreas of immunodeficient NSG mice. Results: Body weight, muscle mass, and fat mass were significantly decreased in each PDX line. Histological assessment of cryosections taken from the tibialis anterior (TA) and diaphragm (DIA) revealed differential effects of tumor-burden on their morphology. Subsequent genome-wide microarray analysis on TA and DIA revealed key differences between their transcriptomes in response to cancer as well. Indeed, upregulated genes in the diaphragm were enriched for extracellular matrix (ECM) protein-encoding genes and genes related to the inflammatory response, and downregulated genes were enriched for mitochondria related protein-encoding genes. Conversely, the TA showed upregulation of canonical atrophy-associated pathways such as ubiquitin-mediated protein degradation and apoptosis and enrichment of downregulated genes encoding ECM proteins. Conclusions: These data suggest that distinct biological processes account for wasting in different skeletal muscles in response to the same tumor burden. Further investigation into these differences will be critical for the future development of effective clinical strategies to counter cancer cachexia.

Project description:BackgroundCancer cachexia is a life-threatening metabolic syndrome that causes significant loss of skeletal muscle mass and significantly increases mortality in cancer patients. Currently, there is an urgent need for better understanding of the molecular pathophysiology of this disease so that effective therapies can be developed. The majority of pre-clinical studies evaluating skeletal muscle's response to cancer have focused on one or two pre-clinical models, and almost all have focused specifically on limb muscles. In the current study, we reveal key differences in the histology and transcriptomic signatures of a limb muscle and a respiratory muscle in orthotopic pancreatic cancer patient-derived xenograft (PDX) mice.MethodsTo create four cohorts of PDX mice evaluated in this study, tumours resected from four pancreatic ductal adenocarcinoma patients were portioned and attached to the pancreas of immunodeficient NSG mice.ResultsBody weight, muscle mass, and fat mass were significantly decreased in each PDX line. Histological assessment of cryosections taken from the tibialis anterior (TA) and diaphragm (DIA) revealed differential effects of tumour burden on their morphology. Subsequent genome-wide microarray analysis on TA and DIA also revealed key differences between their transcriptomes in response to cancer. Genes up-regulated in the DIA were enriched for extracellular matrix protein-encoding genes and genes related to the inflammatory response, while down-regulated genes were enriched for mitochondria related protein-encoding genes. Conversely, the TA showed up-regulation of canonical atrophy-associated pathways such as ubiquitin-mediated protein degradation and apoptosis, and down-regulation of genes encoding extracellular matrix proteins.ConclusionsThese data suggest that distinct biological processes may account for wasting in different skeletal muscles in response to the same tumour burden. Further investigation into these differences will be critical for the future development of effective clinical strategies to counter cancer cachexia.

Project description:Cancer cachexia represents a debilitating muscle wasting condition that is highly prevalent in patients with pancreatic ductal adenocarcinoma (PDAC). Cachexia is estimated to contribute to ~30% of cancer-related deaths, with deterioration of respiratory muscles suspected to be a key contributor to cachexia-associated morbidity and mortality. In recent studies, we identified inflammation and fibrotic remodeling of respiratory accessory muscles as a key feature of human PDAC cachexia. To gain insight into mechanisms driving respiratory muscle wasting and fibrotic remodeling in response to PDAC, we conducted temporal histological and transcriptomic analyses on diaphragm muscles harvested from mice bearing orthotopic murine pancreatic (KPC) tumors at time points reflective of pre-cachexia (D8 and D10), mild-moderate cachexia (D12 and D14) and advanced cachexia (endpoint). Compared to Sham, KPC mice showed progressive diaphragm myofiber atrophy beginning on D12 (-16 to -24% , D12toendpointvs.Sham,P< 0.05), which preceded reductions in breathing frequency (-55%,P= 0.0074) and diaphragm excursion (-43%,P= 0.0006) observed at endpoint. During the pre-cachexia phase, diaphragms showed significantleukocyte infiltration (+3 fold to +13-fold; D8–endpointvs.Sham,P< 0.05) and transcriptomic enrichment of inflammatory processes associated with tissue injury that remained increased through endpoint. Diaphragm inflammation was followed by increases in PDGFR+ fibroadipogenic progenitors (+2.5 to +3.8-fold; D10–endpointvs.Sham,P< 0.05), ECM expansion (+1.5 to +1.8-fold; D14–endpointvs.Sham),P<0.05) and collagen accumulation (+3.8-fold; Endpointvs.Sham,P= 0.0013). These processes were supported by changes in the diaphragm transcriptome. Ingenuity pathway analysis predicted factors involved in inflammatory responses to tissue injury, including TGF-B1, Angiotensin, and PDGF BB, as top upstream regulators activated in diaphragms prior to and throughout cachexia progression, while PGC-1α and the insulin receptor were among the top upstream regulators predicted to be suppressed. The transcriptomic dataset further revealed progressive disturbances to networks involved in lipid, glucose and oxidative metabolism, activation of the unfolded protein response and neuromuscular junction remodeling associated with denervation. In summary, our data support leukocyte infiltration and fibroadipogenic progenitor expansion as early events that precede wasting and fibrotic remodeling of respiratory muscles in response to PDAC that may also underlie metabolic disturbances, weakness and respiratory complications.

Project description:Background. Pancreatic Ductal AdenoCarcinoma (PDAC), the most frequent pancreatic cancer, is a deadly cancer since often diagnosed late and resistant to current therapies. A high proportion of PDAC patients are affected by cachexia induced by the tumor. This cachexia, characterized by loss of muscle mass and strength, contributes to patient frailty and poor therapeutic response. We showed that mitochondrial metabolism is reprogrammed in PDAC tumor cell and constitutes a vulnerability, opening novel therapeutic avenues. The objective of the present work was to investigate the molecular mechanisms underlying mitochondrial remodeling in PDAC cachectic skeletal muscle. Methods. Our study focused on the gastrocnemius muscle of genetically-engineered mice developing spontaneously a PDAC associated with cachexia (KIC GEMM). We compared KIC mice developing a pancreatic tumor in 9-10 weeks to control littermates. We did an integrative study combining in vivo functional analyses by non-invasive Magnetic Resonance, and ex-vivo histology, Seahorse, RNA-sequencing, and proteomic mass spectrometry and western blotting analyses. Results. The cachectic KIC PDAC mice show a severe sarcopenia with loss of muscle mass and strength associated with a diminution in muscle fiber’s size and induction of protein degradation processes. Mitochondria in PDAC atrophic muscles show decreased respiratory capacities and structural alterations (“hyperfused” mitochondria), associated with deregulation of oxidative phosphorylation and mitochondrial dynamics pathways at the molecular level. Increased expression of multiple reactive oxygen species (ROS) defense genes suggests oxidative stress prone to affect mitochondrial macromolecules and homeostasis. Interestingly, multiple genes and proteins involved in DNA metabolism pathways, such as DNA damage, degradation of DNA, nucleotide synthesis, and folate pathway were found altered in sarcopenic mitochondria. While the number of mitochondria was not changed, the mitochondrial mass was decreased by a factor of 2 and the mitochondrial DNA by a factor of 3, suggesting a defect in mitochondrial genome homeostasis. Conclusions. We unveiled that mitochondrial alterations in skeletal muscle play a central role in PDAC-induced cachexia. Muscle atrophy is associated with strong mitochondrial metabolic defects that are not limited to carbohydrates and protein, but concern also lipids, ROS and nucleic acids. Our data provide a frame to guide towards the most relevant molecular markers that would be affected at the start of tumor development and could be targets in the clinic to limit PDAC-induced cachexia at early stages of the pathology.

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Mouse limb and respiratory muscle show distinct cachexia profiles in response to human pancreatic tumors

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