To study the Siah1 protein level in H. pylori-infected gastric cancer cells (GCCs), MKN45 cells were infected with a cytotoxin-associated gene pathogenicity island-positive {cag PAI(+)} H. pylori strain 26695 at a multiplicity of infection (MOI) 100 and 200 for 3 h and 6 h. The gene discussed is SIAH1; the disease is infection.