Fig. 4

LINC00240 interacts with oncoprotein DDX21 in gastric cancer cells. A LINC00240 predominantly locates in the nuclear fraction of gastric cancer cells. B LINC00240 pull-down followed by Western blot validated its interaction with DDX21 and other candidate proteins identified by Mass spectrometry. C LINC00240 could be precipitated with antibody against DDX21 as compared with the IgG control in HGC-27 and MGC80-3 cells. Relative enrichment (means ± SD) represents RNA levels associated with DDX21 relative to an input control from three independent experiments. D Diagrams of HA-tagged DDX21 and its truncated forms used in LINC00240 pull-down assays. Western blot of HA-tagged wild-type (WT) DDX21 and its truncated forms retrieved by in vitro transcribed biotinylated LINC00240. E Truncated LINC00240 mapping of DDX21 binding domain. Top panel: schematic diagrams of LINC00240 full-length and truncated fragments. Middle panel: RNA sizes of in vitro transcribed full-length and truncations of LINC00240. Bottom panel: Western blot of DDX21 pulled down by various LINC00240 fragments. F There were evidently increased DDX21 expression in gastric cancer tissues compared to normal tissues in both Discovery cohort and Validation cohort. G, H The high expression levels of DDX21 were significantly associated with poor OS or PFS of gastric cancer patients. I, J Silencing of DDX21 expression with different siRNAs in HGC-27 and MGC80-3 cells. K DDX21-knockdown significantly suppressed proliferation of HGC-27 and MGC80-3 gastric cancer cell lines. Data are shown as mean ± SD. ***P < 0.001 by unpaired Student’s t test (C, F, J, K)