JAK Inhibitors Suppress Colon Cancer Cachexia-Associated Anorexia and Adipose Wasting in Mice

Abstract

Abbreviations: CX, cachexia; IL-6, interleukin 6; JAK, janus kinase; LIF, leukemia inhibitory factor; rLIF, recombinant leukemia inhibitory factor; STAT3, signal transducer and activator of transcription 3. ABSTRACTBackground: Cachexia (CX), a syndrome of muscle atrophy, adipose loss, and anorexia, is associated with reduced survival in cancer patients. The colon adenocarcinoma C26c20 cell line secretes the cytokine leukemia inhibitor factor (LIF) which induces CX. We characterized how LIF promotes CX-associated weight loss and anorexia in mice through JAK-dependent changes in adipose and hypothalamic tissues.Methods: CX was induced in vivo with C26c20 colon adenocarcinoma cells or recombinant LIF administration in the absence or presence of JAK inhibitors. Blood, adipose, and hypothalamic tissues were collected and processed for cyto/adipokine ELISAs, immunoblot analysis, and quantitative RT-PCR. CX was induced in vitro by stimulating differentiated adipocytes with recombinant LIF or IL-6 in the absence or presence of lipase or JAK inhibitors. These activated adipocytes were processed for lipolysis, immunoblot analysis, and RT-PCR.Results: Tumor-secreted LIF induced changes in adipose tissue expression and serum levels of IL-6 and leptin in a JAK-dependent manner influencing CX-associated adipose wasting and anorexia. We identified two JAK inhibitors that block cytokine-mediated adipocyte lipolysis and IL-6 induction using an in vitro CX lipolysis assay. JAK inhibitors administered to in vivo colon cancer CX mouse models led to 1) a decrease in STAT3 phosphorylation in hypothalamic and adipose tissues, 2) a reverse in the CX serum cyto/adipokine signature, 3) a delay in colon cancer CX-associated anorexia and adipose loss, and 4) an improvement in overall survival. Conclusions: JAK inhibitors suppress cytokine-associated adipose loss and anorexia in multiple in vitroand in vivo models of cancer CX.

LIFR-α-dependent adipocyte signaling in obesity limits adipose expansion contributing to fatty liver disease

“…The adipocyte fractions were subjected to qRT-PCR, and Adipoq-Cre;-LIFR fl/fl adipocytes demonstrated no detectable mRNA expression of LIFR, verifying disruption of the gene in adipocytes in the adipose tissue of the knockout animals ( Figure 1C). Adipocytes from the LIFR knockout mice also had a significant decrease in IL6 expression compared with littermate controls, which is consistent with our previous findings that LIF increases IL6 expression in a JAK-dependent manner in differentiated adipocytes (Arora et al, 2020). At the protein level, there was a significant reduction in LIFR-a in eWAT of knockout mice compared with controls, with equivalent hepatic levels of LIFR-a in knockout and littermate controls ( Figure 1D).…”

“…We have now shown that LIF signals through its receptor LIFR-a to induce STAT3 activation and adipocyte lipolysis in adipose. We previously showed that LIF and other IL-6 family members increase the lipolysis potential of the adipocyte through a JAK-dependent mechanism (Arora et al, 2020). Although we observed an association of STAT3 phosphorylation with LIF and IL-6-mediated lipolysis, there was no evidence that STAT3 was required for IL-6 family cytokine-mediated adipocyte lipolysis.…”

“…Multiple cellular (adipocytes and non-adipocytes) and soluble components are contributors to the chronic inflammation observed in adipose during obesity development. We previously showed that recombinant LIF could increase JAK-dependent STAT3 inflammation in adipose tissue to restrict further adipose expansion when administered to wild-type and obese murine models (Arora et al, , 2020. As the adipocytespecific STAT3 knockout model demonstrated no additional phenotypic changes beyond those observed in the adipocyte-specific LIFR knockout mouse, we conclude that the upstream LIFR-a component of this signaling axis is important to STAT3 adipose activation in DIO.…”

“…Although obesity is associated with adipose inflammation, the role of cytokine inflammatory signaling in regulating adipose expansion and related metabolic sequelae remain unclear. Previously, we provided insight into how IL-6 family cytokines, including LIF, induce adipose inflammation and lipolysis in a JAKdependent manner to regulate adipose levels in mouse models of obesity and cachexia (Arora et al, , 2020. In this study, we addressed the role of LIFR-a adipocyte signaling during DIO-associated metabolic states of adipose inflammation.…”

“…These cytokines are also associated with adipose inflammation in cachexia, a syndrome on the opposite end of the metabolic spectrum Auernhammer and Melmed, 2000;Seto et al, 2015). LIF signals through its canonical receptor LIFR-a (LIFR gene) and co-receptor gp130 to activate the JAK/STAT inflammatory pathway (Arora et al, , 2020Song and Lim, 2006). LIF signaling in differentiated adipocytes leads to JAK-dependent STAT3 phosphorylation, which (1) increases basal level lipolysis to break down triacylglycerol (TAG) to glycerol and fatty acids and (2) increases expression of the gene encoding IL-6 (IL6).…”