Outstanding Progress｜Cancer Chemotherapy Center

Update : 2015-12-16

Targeting a novel domain in podoplanin for inhibiting platelet-mediated tumor metastasis

Takaya Sekiguchi^1,2, Ai Takemoto¹, Satoshi Takagi¹, Kazuki Takatori^1,2, Shigeo Sato¹, Miho Takami¹, Naoya Fujita^1,3＊

Oncotarget In press

Affiliation

Division of Experimental Chemotherapy, Cancer Chemotherapy Center of JFCR
Graduate School of Frontier Sciences, the University of Tokyo
Director’s Room, Cancer Chemotherapy Center of JFCR

＊Corresponding author

Podoplanin, also known as Aggrus, is a sialoglycoprotein expressed on various cancers. We previously identified podoplanin as a key factor for tumor-induced platelet aggregation. The podoplanin-mediated platelet aggregation enhanced tumor growth and metastasis by secreting growth factors and by forming tumor emboli in microvasculature, respectively. Thus, precise analysis of the mechanisms of podoplanin-mediated platelet aggregation was desired for developing new anti-tumor therapies. Here we report the discovery of a novel platelet aggregation-inducing PLAG4 domain (81-EDLPT-85) in human podoplanin. PLAG4 domain has some homology to the previously reported PLAG3 domain and contributes to the binding to its platelet receptor CLEC-2. Analysis using point mutants and deletion mutants revealed that PLAG4 domain exhibited predominant platelet-aggregating function over PLAG3 domain, and that conserved Glu81/Asp82/Thr85 residues in PLAG4 domain were indispensable for the binding to CLEC-2. By immunizing mice with PLAG4 containing peptide, we established anti-PLAG4 neutralizing mAbs. We found that the mAbs could suppress CLEC-2 binding, platelet aggregation and tumor emboli formation in vivo, suggesting the importance of PLAG4 domain in platelet-aggregating function. Our results indicate the requirement of simultaneous inhibition of PLAG3/4 domains for complete suppression of podoplanin-mediated tumor growth and metastasis.