Circulating lung cancer exosomes damage the niche of intestinal stem cells

Cancer-associated weight loss occurs frequently in patients with advanced lung cancer. Many studies have demonstrated that tumor-derived exosomes could mediate the interplay between tumor cells and distal organs. In this study, we explored the interaction between lung cancer cell-derived exosomes (LCCDEs) and the niche of intestinal stem cells (ISCs).

Lewis lung carcinoma-1 (LLC1)-conditional medium (LLC1-CM), N,N'-Bis[5-(2,3-dihydro-1H-indol-1-yl)pentyl]-1,6-hexanediamine (GW4869)-conditional medium (GW4869-CM), LCCDEs and phosphate-buffered saline (PBS) were used to treat 6- to 8-week-old healthy male C57BL/6J mice (18-22 g) and B6.129P2-Lgr5^{tm1(cre/ERT2)Cle}/J (Lgr5-EGFP-IRES-creERT2) mice (Lgr5-EGFP mice). Additionally, enteroids were treated with LLC1-CM, A549 human lung adenocarcinoma cells (A549)-CM, LCCDEs of LLC1 cells and A549 cells and PBS. LCCDEs were characterized by transmission electron microscopy, Western blot, and nanoparticle tracking analysis. The influence of LCCDEs on intestine and ISCs was explored by hematoxylin & eosin staining, proliferation, differentiation, enteroid culture, and quantitative polymerase chain reaction. PKH26-labeled LCCDEs were detected in intestinal epithelial cell line 6 (IEC-6) cells and Lgr5-EGFP mice. The changes of ISCs' niche caused by LCCDEs were examined by p-S6, pERK1/2 and p-STAT3 immunostaining.

LLC1-CM damaged the small intestines and small intestinal organoids. The inhibition of exosomes by GW4869 partially alleviated these effects. Purified LCCDEs altered the structure of the intestines, changed the proliferation and differentiation of ISCs and inhibited the growth of enteroids. In addition, PKH26-labeled LCCDEs entered the cytoplasm of IECs and Paneth cells and changed the messenger ribonucleic acid (mRNA) expression of many genes, including stem cell marker genes, growth factor genes, and epithelial marker genes. Mechanistically, LCCDEs decreased mTORC1 activity in Paneth cells and inhibited p-ERK1/2 signaling in ISCs.

We demonstrated that circulating exosomes derived from lung cancer could impair ISCs and alter their niche in mice, which further explained the interaction between lung cancer and the gastrointestinal tract. This study proposes a promising and novel therapy to overcome weight loss in patients by decreasing LCCDEs secretion and blocking their binding to the intestine, which might be a feasible therapeutic approach in future clinical practice.