PLAC1 and neoplasm: When CXCL11 expression was knocked down by siRNA, both Plac1‐NC HN6 cells (p = 0.0153) and Plac1‐OE Cal27 cells (p < 0.0001) recruited less CD4+ T cells than did the control cells, while no significant differences were seen in Plac1‐KO HN6 cells or Plac1‐VEC Cal27 cells, which suggested that the CD4+ T cell recruitment efficacy was associated with the Plac1 expression level in tumor cells (Figure 6G).