PTGDR and gastric cancer: As mentioned above, among the GC cells, PCED1B-AS1 expression was the highest in HGC-27 and the lowest in NCI-N87, so we transfected siRNA (si-PCED1B-AS1-1, si-PCED1B-AS1-2, and si-PCED1B-AS1-3) and PCED1B-AS1 overexpression vector (pc-PCED1B-AS1) targeting PCED1B-AS1 into HGC-27 and NCI-N87, respectively (Figure 2a).