PAX5 and neoplasm: Since differences in the number of B cells present in each tumor sample, and the presence of infiltrating T cells, could potentially obscure differences in cellular gene expression specific to the B-cell population, we initially compared the expression of a B-cell specific gene, PAX5, and the expression of several different well-known EBNA3C target genes in the Δ3C virus-infected versus WT virus-infected tumors.