CD4 and breast cancer: Although the treatment of recombinant EphA4 protein could reduce T‐cell cytotoxicity against RNase1‐overexpressing breast cancer cells, these results cannot fully support RNase1‐induced CD4+ T‐cell activation through RNase1‐EphA4 axis due to the other functions or off‐target effects of recombinant EphA4 protein.