SEMA4D and breast cancer: To confirm if Sema molecules interact with PLXNB2 in breast cancer cells, we performed a co-immunoprecipitation for human PLXNB2 using clustered TNBC cells; and found that SEMA4C was specifically enriched in the PLXNB2 protein complex, whereas SEMA4D was nearly undetectable (Fig. 4c), demonstrating SEMA4C-PLXNB2 interactions in the homotypic CTC clusters.