Cancer-associated fibroblasts regulate the plasticity of lung cancer stemness via paracrine signalling. Chen Wan-Jiun,Ho Chao-Chi,Chang Yih-Leong,Chen Hsuan-Yu,Lin Chih-An,Ling Thai-Yen,Yu Sung-Liang,Yuan Shin-Sheng,Chen Yu-Ju Louisa,Lin Chien-Yu,Pan Szu-Hua,Chou Han-Yi Elizabeth,Chen Yu-Ju,Chang Gee-Chen,Chu Wen-Cheng,Lee Yee-Ming,Lee Jen-Yi,Lee Pei-Jung,Li Ker-Chau,Chen Huei-Wen,Yang Pan-Chyr Nature communications Cancer stem cells (CSCs) are a promising target for treating cancer, yet how CSC plasticity is maintained in vivo is unclear and is difficult to study in vitro. Here we establish a sustainable primary culture of Oct3/4(+)/Nanog(+) lung CSCs fed with CD90(+) cancer-associated fibroblasts (CAFs) to further advance our knowledge of preserving stem cells in the tumour microenvironment. Using transcriptomics we identify the paracrine network by which CAFs enrich CSCs through de-differentiation and reacquisition of stem cell-like properties. Specifically, we find that IGF1R signalling activation in cancer cells in the presence of CAFs expressing IGF-II can induce Nanog expression and promote stemness. Moreover, this paracrine signalling predicts overall and relapse-free survival in stage I non-small cell lung cancer (NSCLC) patients. IGF-II/IGF1R signalling blockade inhibits Nanog expression and attenuates cancer stem cell features. Our data demonstrate that CAFs constitute a supporting niche for cancer stemness, and targeting this paracrine signalling may present a new therapeutic strategy for NSCLC. 10.1038/ncomms4472