CD8A and breast cancer: Interestingly, a recent study revealed that TGFB inhibition-caused tumor-killing effect is mediated by CD4+ helper T cells, rather than CD8+ effector T cells.3 Liu et al silenced the expression of TGFB receptors on CD4+ T cells and CD8+ T cells in mice with breast cancer and found that tumor growth is severely inhibited when CD4+ T cells, rather than CD8+ T cells, lack TGFB receptors.