Blocking podoplanin suppresses growth and pulmonary metastasis of human malignant melanoma

Mengqiao Xu,Yanfang Pan,Lijun Xia,Yiming Zhao,Bin Yan,Xia Wang,Changgeng Ruan,Xingpeng Zhao

doi:10.1186/s12885-019-5808-9

Abstract

BackgroundPodoplanin (PDPN), a transmembrane O-glycoprotein, is up-regulated in many tumors and is involved in tumor metastasis and malignant progression. In previous studies, we generated a functional blocking monoclonal antibody (mAb, SZ168) against the extracellular domain of human PDPN. This study is aimed to investigate whether blocking PDPN by SZ168 inhibits tumor growth and metastasis.MethodsMalignant melanoma xenograft model by inoculating subcutaneously human malignant melanoma cell line C8161 into the back of BALB/c nude mice was used. Endogenous PDPN expression in C8161 cells and nasopharyngeal cancer cell line CNE-2 was detected using western blot and flow cytometry.ResultsSZ168 significantly inhibited C8161 or CNE-2 cell-induced platelet aggregation in a dose-dependent manner with a maximal inhibition of 73.9 ± 3.0% in C8161 cells or 77.1 ± 2.7% in CNE-2 cells. Moreover, SZ168 inhibited the growth and pulmonary metastasis of C8161cells in vivo. The number of lung metastatic foci in the SZ168-treated group was significantly decreased compared with that in the control mouse IgG group (1.61 ± 0.44 vs.3.83 ± 0.60, P < 0.01). Subcutaneous tumor volume, weight, and incidence were also significantly reduced in the SZ168-treated group compared to the control group (P < 0.05). Additionally, SZ168 recognized PDPN in immunohistochemical analyses of tumor tissue sections.ConclusionsSZ168 blocks growth and pulmonary metastasis of human malignant melanoma by inhibiting the interaction between tumor PDPN and platelet CLEC-2 and therefore is a promising antibody for therapeutic development against malignant melanoma.

Highlights

Podoplanin (PDPN), a transmembrane O-glycoprotein, is up-regulated in many tumors and is involved in tumor metastasis and malignant progression
SZ163 and SZ168 detect PDPN expression on the membrane of C8161 and CNE-2 cells Our previous study found that SZ163 and SZ168 detected hPDPN in Chinese hamster ovary (CHO)/hPDPN, NCI-H226, and U87 cells but not CHO cells [24], indicating that SZ163 and SZ168 recognize hPDPN
Flow cytometry assay showed that SZ163 and SZ168 detected endogenous PDPN in the human cancer cell lines C8161 and CNE-2, to the 18H5 as positive control antibody (Fig. 1a, b)

Summary

Introduction

Podoplanin (PDPN), a transmembrane O-glycoprotein, is up-regulated in many tumors and is involved in tumor metastasis and malignant progression. This study is aimed to investigate whether blocking PDPN by SZ168 inhibits tumor growth and metastasis. One of the mechanisms is tumor cell-induced platelet aggregation (TCIPA) [3, 4], which may enhance embolism in the Podoplanin (PDPN) is a transmembrane sialo-glycoprotein and its overexpression has been detected in many types of tumors, including squamous cell carcinoma [5,6,7], malignant mesothelioma [8, 9], Kaposi’s sarcoma [10], testicular seminoma [11], and brain tumors [12]. Recent studies suggested that the role of PDPN is associated with tumor metastasis, malignancy, and poor prognosis [13,14,15,16,17,18].

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