We previously developed a mouse mAb (clone PMab-2) against the platelet aggregation-stimulating domain of rat podoplanin.(24) Podoplanin is a type I transmembrane protein, which is highly expressed in many normal cells and cancer cells, and is involved in tumor-induced platelet aggregation by binding to CLEC-2 on platelets.(3,25–33) Because PMab-2 possesses high affinity and specificity against rat podoplanin,(24) it was expected to be useful as an antitag antibody. This evidence concerns the gene PDPN and cancer.