Hepatic signal transducer and activator of transcription-3 signalling drives early-stage pancreatic cancer cachexia via suppressed ketogenesis.

BACKGROUND: Patients with pancreatic ductal adenocarcinoma (PDAC) often suffer from cachexia, a wasting syndrome that significantly reduces both quality of life and survival. Although advanced cachexia is associated with inflammatory signalling and elevated muscle catabolism, the early events driving wasting are poorly defined. During periods of nutritional scarcity, the body relies on hepatic ketogenesis to generate ketone bodies, and lipid metabolism via ketogenesis is thought to protect muscle from catabolizing during nutritional scarcity. METHODS: We developed an orthotopic mouse model of early PDAC cachexia in 12-week-old C57BL/6J mice. Murine pancreatic cancer cells (KPC) were orthotopically implanted into the pancreas of wild-type, IL-6-/-, and hepatocyte STAT3-/- male and female mice. Mice were subject to fasting, 50% food restriction, ad libitum feeding or ketogenic diet interventions. We measured longitudinal body composition by EchoMRI, body mass and food intake. At the endpoint, we measured tissue mass, tissue gene expression by quantitative real-time polymerase chain reaction, whole-body calorimetry, circulating hormone levels, faecal protein and lipid content, hepatic lipid content and ketogenic response to medium-chain fatty acid bolus. We assessed muscle atrophy in vivo and C2C12 myotube atrophy in vitro. RESULTS: Pre-cachectic PDAC mice did not preserve gastrocnemius muscle mass during 3-day food restriction (-13.1 ± 7.7% relative to food-restricted sham, P = 0.0117) and displayed impaired fatty acid oxidation during fasting, resulting in a hypoketotic state (ketogenic response to octanoate bolus, -83.0 ± 17.3%, P = 0.0328; Hmgcs2 expression, -28.3 ± 7.6%, P = 0.0004). PDAC human patients display impaired fasting ketones (-46.9 ± 7.1%, P < 0.0001) and elevated circulating interleukin-6 (IL-6) (12.4 ± 16.5-fold increase, P = 0.0001). IL-6-/- PDAC mice had improved muscle mass (+35.0 ± 3.9%, P = 0.0031) and ketogenic response (+129.4 ± 44.4%, P = 0.0033) relative to wild-type PDAC mice. Hepatocyte-specific signal transducer and activator of transcription 3 (STAT3) deletion prevented muscle loss (+9.3 ± 4.0%, P = 0.009) and improved fasting ketone levels (+52.0 ± 43.3%, P = 0.018) in PDAC mice. Without affecting tumour growth, a carbohydrate-free diet improved tibialis anterior myofibre diameter (+16.5 ± 3.5%, P = 0.0089), circulating ketone bodies (+333.0 ± 117.6%, P < 0.0001) and Hmgcs2 expression (+106.5 ± 36.1%, P < 0.0001) in PDAC mice. Ketone supplementation protected muscle against PDAC-induced atrophy in vitro (+111.0 ± 17.6%, P < 0.0001 myofibre diameter). CONCLUSIONS: In early PDAC cachexia, muscle vulnerability to wasting is dependent on inflammation-driven metabolic reprogramming in the liver. PDAC suppresses lipid ß-oxidation and impairs ketogenesis in the liver, which is reversed in genetically modified mouse models deficient in IL-6/STAT3 signalling or through ketogenic diet supplementation. This work establishes a direct link between skeletal muscle homeostasis and hepatic metabolism. Dietary and anti-inflammatory interventions that restore ketogenesis may be a viable preventative approach for pre-cachectic patients with pancreatic cancer.

Postpartum breast cancer has a distinct molecular profile that predicts poor outcomes.

Young women's breast cancer (YWBC) has poor prognosis and known interactions with parity. Women diagnosed within 5-10 years of childbirth, defined as postpartum breast cancer (PPBC), have poorer prognosis compared to age, stage, and biologic subtype-matched nulliparous patients. Genomic differences that explain this poor prognosis remain unknown. In this study, using RNA expression data from clinically matched estrogen receptor positive (ER+) cases (n = 16), we observe that ER+ YWBC can be differentiated based on a postpartum or nulliparous diagnosis. The gene expression signatures of PPBC are consistent with increased cell cycle, T-cell activation and reduced estrogen receptor and TP53 signaling. When applied to a large YWBC cohort, these signatures for ER+ PPBC associate with significantly reduced 15-year survival rates in high compared to low expressing cases. Cumulatively these results provide evidence that PPBC is a unique entity within YWBC with poor prognostic phenotypes.

Immune Milieu Established by Postpartum Liver Involution Promotes Breast Cancer Liver Metastasis.

In rodents, we identified a physiologic process within the normal liver that creates a pre-metastatic niche. This physiology is weaning-induced liver involution, characterized by hepatocyte cell death, immune influx, and extracellular matrix remodeling. Here, using weaning-induced liver involution as a model of a physiologically regulated pro-metastatic niche, we investigate how liver involution supports breast cancer metastasis. Liver metastases were induced in BALB/c immune competent hosts by portal vein injection of D2OR (low metastatic) or D2A1 (high metastatic) mouse mammary tumor cells. Tumor incidence and multiplicity increased in involution hosts with no evidence of a proliferation advantage. D2OR tumor cell extravasation, seeding, and early survival were not enhanced in the involuting group compared to the nulliparous group. Rather, the involution metastatic advantage was observed at 14 days post tumor cell injection. This metastatic advantage associated with induction of immune tolerance in the involution host liver, reproductive state dependent intra-tumoral immune composition, and CD8-dependent suppression of metastases in nulliparous hosts. Our findings suggest that the normal postpartum liver is in an immune suppressed state, which can provide a pro-metastatic advantage to circulating breast cancer cells. Potential relevance to women is suggested as a postpartum diagnosis of breast cancer is an independent predictor of liver metastasis.