CD4 and cancer: This corresponded to a relative downregulation of T cell markers such as CD3, CD8, CD4, CD27 and CD44 in both the OSCC and the CRC cancer tissue, along with reduced expression of the proliferation marker Ki-67, and suggests that T cells are excluded in bacteria-colonized regions of these two cancers of the gastrointestinal tract (Fig. 2b and Supplementary Table 4).