Prevention of hematogenous metastasis by neutralizing mice and its chimeric anti‐Aggrus/podoplanin antibodies

The platelet aggregation‐inducing factor, Aggrus (also known as podoplanin), is reported to contribute to cancer metastasis by mediating cancer cell–platelet interaction. Aggrus has been shown to be upregulated in many different types of cancers. Thus, not only the functional inhibition of Aggrus, but also its application as a cancer‐specific antigen has therapeutic potential. Among a series of anti‐Aggrus mAb established previously, no mouse anti‐human Aggrus mAb exists that possesses the ability to neutralize platelet aggregation. For precise preclinical examinations of mouse and monkey models, the establishment of Aggrus‐neutralizing mouse mAb and their chimeric Abs is needed. In this study, we established two mouse anti‐human Aggrus mAb, P2‐0 and HAG‐3. A precise analysis of their epitopes revealed that P2‐0 recognized the conformation near the bioactive O ‐glycosylation site at the Thr 52 residue. In contrast, HAG‐3 recognized the amino‐terminus side at a short distance from the conformation recognized by P2‐0. We observed that only P2‐0 attenuated Aggrus‐induced platelet aggregation and Aggrus binding to its platelet receptor, that is, the C‐type lectin‐like receptor‐2. Consistent with these data, only P2‐0 prevented the experimental metastasis of human Aggrus‐overexpressing CHO cells. Subsequently, we cloned the complementary determining region of P2‐0 and produced the murine/human chimeric P2‐0 antibody. This chimeric antibody maintained its inhibitory activity of Aggrus‐induced platelet aggregation and experimental metastasis. Thus, P2‐0 and its chimeric antibody are expected to aid the development of preclinical and clinical examinations of Aggrus‐targeted cancer therapy. ( Cancer Sci 2011; 102: 2051–2057)