Fig. 2
Identification of the IL-6/Jak1/STAT3 axis as a specific communicator between cancer-associated fibroblasts (CAFs) and gastric cancer cells. a Interleukin-6 (IL-6), interleukin-8 (IL-8), and C-C motif chemokine ligand 2 (CCL2) were secreted at higher levels in the media after co-culture with CAFs and MKN-45 cells than in the media used for culturing MKN-45 cells alone. Each of these factors were correlated with the Jak-STAT3 signal transduction pathway. The Western blot analysis shows expression changes of the indicated proteins with and without co-culture with CAFs for 6 or 24 h. b A flow chart depicting the transcriptome analysis of one paired set of normal-associated fibroblasts (NAFs) and CAFs. The pie graph presents the number of upregulated and downregulated genes in CAFs compared with those in NAFs. The graph and table show the functional annotation of results for 784 upregulated genes in CAFs from the Database for Annotation, Visualization, and Integrated Discovery (DAVID: https://david.ncifcrf.gov), which is based on the Kyoto Encyclopedia of Genes and Genomes pathways. c Results from quantitative PCR (qPCR) analysis showing the comparative mRNA expression of ACTC2, IL6, IL12A, and IL24 between the NAFs and CAFs. The graphs show the mean (± SEM) ratio of mRNA expression in CAFs compared to those in NAFs. *P < 0.05, based on paired t-tests. d Reverse transcription PCR (RT-PCR) results showing mRNA expression of IL-6 and its receptors in cells from the gastric cancer cell lines AGS, MKN-1, and MKN-45, and four paired NAFs and CAFs. e ELISA results showing IL-6 levels in the conditioned media from four paired NAFs and CAFs and from cells of the gastric cancer cell lines KATO-III, MKN-28, and MKN-45. *P < 0.05 and **P < 0.001, according to paired t-tests. f, g Western blot analysis showing the expression levels of the indicated proteins after 5-fluorouracil (5-FU) treatment (5 μM) with and without co-culture with CAFs and with and without recombinant IL-6 treatment in MKN-45 cells and MKN-1 cells