Unlike gastric cancers in their natural immune microenvironment, PDX samples did not exhibit elevated IDO1 expression (Figure 4I) or enrichment of W>F substitutants (Figure 4J), illustrating that the emergence of W>F substitutants in gastric cancer did not due to the EB virus, but to the host tumor microenvironment and compatible immune response. The gene discussed is IDO1; the disease is neoplasm.