Exosomal IL-8 derived from Lung Cancer and Colon Cancer cells induced adipocyte atrophy via NF-κB signaling pathway

Background: Cytokines secreted in the tumor microenvironment function in Cancer cachexia (CC), a common clinicopathological syndrome associated with adipocyte wasting and skeletal muscle atrophy. Extracellular vesicles (EVs) secreted by Cancer cells actively engage in inter-tissue communication; EVs and enclosed cytokines are largely undefined in CC adipocytes wasting.

Methods: EVs derived from Lewis lung carcinoma (LLC) and colorectal Cancer C26 cells were extracted and characterized. Conditioned medium and EVs from Cancer cells were applied to 3 T3-L1 adipocytes. Recombinant IL-8, IL-8 neutralizing antibody, CXCR2 and NF-κB Inhibitor were examined in functional assays. Lipolysis of adipocytes was monitored by Western blots, Oil red O staining and glycerol assays. Furthermore, LLC and C26 cell lines were established as cachexia model to explore the relevance of IL-8 and NF-κB signaling in CC adipose wasting. Adipose tissues were collected for histology analyses.

Results: LLC and C26 cell-derived EVs induced lipolysis of 3 T3-L1 adipocytes. Specially, Dil-labeled EVs were effectively taken up by 3 T3-L1 adipocytes, which were motivated by the delivered IL-8 to elicit the NF-κB pathway. In comparison, special IL-8 neutralizing antibody relieved that lipolysis of 3 T3-L1 adipocytes induced by EVs together with conditioned medium of LLC and C26 cells, respectively. Consistently, both CXCR2 and NF-κB inhibitors would lessen the phenotype of lipolysis in 3 T3-L1 adipocytes. In the in vivo settings, both LLC and C26-tumor bearing mice had higher serum IL-8 levels as compared to the control groups. Two typical lipolysis markers, PGC1α and UCP1, were also up-regulated in the adipose tissues of LLC and C26-tumor mice groups, respectively.

Conclusions: EVs secreted by LLC and C26 tumor cells would induce adipocyte wasting via extracellular IL-8-mediated NF-κB signaling. Our study pointed out the physiological and therapeutic values of exosomal IL-8 in CC lipolysis.