BackgroundCancer cachexia is a metabolic wasting syndrome that is strongly associated with a poor prognosis. The initiating factors causing fat and muscle loss are largely unknown. Previously, we found that leukaemia inhibitory factor (LIF) secreted by C26 colon carcinoma cells was responsible for atrophy in treated myotubes. In the present study, we tested whether C26 tumour‐derived LIF is required for cancer cachexia in mice by knockout of Lif in C26 cells.MethodsA C26 Lif null tumour cell line was made using CRISPR‐Cas9. Measurements of cachexia were compared in mice inoculated with C26 vs. C26Lif−/− tumour cells, and atrophy was compared in myotubes treated with medium from C26 vs. C26Lif−/− tumour cells. Levels of 25 cytokines/chemokines were compared in serum of mice bearing C26 vs. C26Lif−/− tumours and in the medium from these tumour cell lines.ResultsAt study endpoint, C26 mice showed outward signs of sickness while mice with C26Lif−/− tumours appeared healthy. Mice with C26Lif−/− tumours showed a 55–75% amelioration of body weight loss, muscle loss, fat loss, and splenomegaly compared with mice with C26 tumours (P < 0.05). The heart was not affected by LIF levels because the loss of cardiac mass was the same in C26 and C26Lif−/− tumour‐bearing mice. LIF levels in mouse serum was entirely dependent on secretion from the tumour cells. Serum levels of interleukin‐6 and G‐CSF were increased by 79‐fold and 68‐fold, respectively, in C26 mice but only by five‐fold and two‐fold, respectively, in C26Lif−/− mice, suggesting that interleukin‐6 and G‐CSF increases are dependent on tumour‐derived LIF.ConclusionsThis study shows the first use of CRISPR‐Cas9 knockout of a candidate cachexia factor in tumour cells. The results provide direct evidence for LIF as a major cachexia initiating factor for the C26 tumour in vivo. Tumour‐derived LIF was also a regulator of multiple cytokines in C26 tumour cells and in C26 tumour‐bearing mice. The identification of tumour‐derived factors such as LIF that initiate the cachectic process is immediately applicable to the development of therapeutics to treat cachexia. This is a proof of principle for studies that when carried out in human cells, will make possible an understanding of the factors causing cachexia in a patient‐specific manner.

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Cancer cachexia represents a debilitating syndrome that diminishes quality of life and augments the toxicities of conventional treatments. Cancer cachexia is particularly debilitating in patients with pancreatic cancer (PC). Mechanisms responsible for cancer cachexia are under investigation and are largely derived from observations in syngeneic murine models of cancer which are limited in PC. We evaluate the effect of human PC cells on both muscle wasting and the systemic inflammatory milieu potentially contributing to PC-associated cachexia. Specifically, human PC xenografts were generated by implantation of pancreatic cancer cells, L3.6pl and PANC-1, either in the flank or orthotopically within the pancreas. Mice bearing orthotopic xenografts demonstrated significant muscle wasting and atrophy-associated gene expression changes compared to controls. Further, despite the absence of adaptive immunity, splenic tissue from orthotopically engrafted mice demonstrated elevations in several pro-inflammatory cytokines associated with cancer cachexia, including TNFα, IL1β, IL6 and KC (murine IL8 homologue), when compared to controls. Therefore, data presented here support further investigation into the complexity of cancer cachexia in PC to identify potential targets for this debilitating syndrome.

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. 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. Methods To 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. 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 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. Conclusions These 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.

This study investigates the role of NLRP3 inflammasome and its main effector Caspase-1 in inflammation and alveolar bone resorption associated with periodontitis. Heat-killed Aggregatibacter actinomycetemcomitans (Aa) was injected 3x/week (4 weeks) into gingival tissues of wild-type (WT), Nlrp3-KO and Caspase1-KO mice. Bone resorption was measured by µCT and osteoclast number was determined by tartrate-resistant acid phosphatase (TRAP) staining. Inflammation was assessed histologically (H/E staining and immunofluorescence of CD45 and Ly6G). In vitro studies determined the influence of Nlrp3 and Caspase-1 in Rankl-induced osteoclast differentiation and activity and on LPS-induced expression of inflammation-associated genes. Bone resorption was significantly reduced in Casp1-KO but not in Nlrp3-KO mice. Casp1-KO mice had increased in osteoclast numbers, whereas the inflammatory infiltrate or on gene expression were similar to those of WT and Nlrp3-KO mice. Strikingly, osteoclasts differentiated from Nlrp3-deficient macrophages had increased resorbing activity in vitro. LPS-induced expression of Il-10, Il-12 and Tnf-α was significantly reduced in Nlrp3- and Casp1-deficient macrophages. As an inceptive study, these results suggest that Nlrp3 inflammasome does not play a significant role in inflammation and bone resorption in vivo and that Caspase-1 has a pro-resorptive role in experimental periodontal disease.