STAT3 and gastric cancer: In addition, PD-L1 overexpression could restore the miR-502-5p-overexpression induced cellular effects whereas CD40/STAT3 overexpression could partially restore the miR-502-5p-overexpression suppressed gastric cancer cells proliferation, migration and invasion (Additional file 4: Figure S3, Additional file 5: Figure S4 and Additional file 6: Figure S5).