Podoplanin Expression in Canine Melanoma

Abstract

A type I transmembrane protein, podoplanin (PDPN), is expressed in several normal cells such as lymphatic endothelial cells or pulmonary type I alveolar cells. We recently demonstrated that anticanine PDPN monoclonal antibody (mAb), PMab-38, recognizes canine PDPN of squamous cell carcinomas, but does not react with lymphatic endothelial cells. Herein, we investigated whether PMab-38 reacts with canine melanoma. PMab-38 reacted with 90% of melanoma cells (9/10 cases) using immunohistochemistry. Of interest, PMab-38 stained the lymphatic endothelial cells and cancer-associated fibroblasts in melanoma tissues, although it did not stain any lymphatic endothelial cells in normal tissues. PMab-38 could be useful for uncovering the function of PDPN in canine melanomas.Keywords: canine podoplanin, melanoma, monoclonal antibody, immunohistochemistry A type I transmembrane sialoglycoprotein, podoplanin (PDPN), is also known as gp40/T1a/Aggrus. (1)(2)(3)(4)(5) PDPN is expressed in normal cells including renal podocytes, pulmonary type I alveolar cells, and lymphatic endothelial cells.(4) PDPN activates platelet aggregation by binding to Ctype lectin-like receptor-2 (CLEC-2) on platelets, (6,7) and the PDPN-CLEC-2 interaction facilitates blood/lymphatic vessel separation.(8) The expression of human PDPN was reported in many tumors, including oral cancers,malignant brain tumors, (10)(11)(12) lung cancers, (13) esophageal cancers,malignant mesotheliomas, (15) testicular tumors, (16) and osteosarcomas.(17) PDPN expression is also associated with cancer metastasis and malignant progression. (6,10) We previously developed an anticanine PDPN monoclonal antibody (mAb), (18) which is useful for immunohistochemistry (IHC), flow cytometry, and Western blotting. Recently, we demonstrated that PMab-38 can recognize PDPN of canine squamous cell carcinomas using IHC.(19) Tumor cells in 15 out of 18 canine squamous cell carcinomas (83%) were stained by PMab-38 in IHC. Cancer-associated fibroblasts in 14 out of 18 cases (78%) were detected by PMab-38. In this study, we investigated whether canine melanoma was stained by PMab-38 because mouse PDPN expression and human PDPN expression were observed in melanomas.(20,21) Watanabe et al. reported that high expression of mouse PDPN is associated with the metastatic ability in metastatic variants of B16 melanomas. (20) We stained 10 canine oral melanomas, which are the most frequent oral cancers in dog. (22) As depicted in Figures 1 and 2A, melanoma cells were stained by PMab-38 in 9 of 10 cases. Although melanoma cells were not stained by PMab-38 in case 9 (Fig. 1), cancer-associated fibroblasts were recognized by PMab-38 (Fig. 2B). Both melanoma cells and cancer-associated fibroblasts were stained in case 5 (Fig. 1). Kan et al. reported that PDPN expression in cancer-associated fibroblasts correlates with aggressive behavior in human melanoma, (21) indicating that PDPN in cancer-associated fibroblasts of melanoma tissues might serve as a useful prognostic factor not only in human melanoma but ...

Chromatin run-on sequencing analysis finds that ECM remodeling plays an important role in canine hemangiosarcoma pathogenesis

“…This interaction then promotes the coating of tumor cells by platelets, thereby protecting tumor cells from the immune system [54]. In addition to its role in human cancers, PDPN is also overexpressed in canine squamous cell carcinomas and melanomas [55] and PDPN mAbs were recently found to have potent anti-tumor activity in mouse xenograft models of canine melanoma [56]. Interestingly, overexpression of PDPN in mice leads to disseminated intravascular coagulation [57], a condition that is strikingly similar to that seen in many dogs with HSA [58].…”

Chromatin run-on sequencing analysis finds that ECM remodeling plays an important role in canine hemangiosarcoma pathogenesis

“…This interaction then promotes the coating of tumor cells by platelets, thereby protecting tumor cells from the immune system [49]. In addition to its role in human cancers, PDPN is also overexpressed in canine squamous cell carcinomas and melanomas [50] and PDPN mAbs were recently found to have potent anti-tumor activity in mouse xenograft models of canine melanoma [51]. Interestingly, overexpression of PDPN in mice leads to disseminated intravascular coagulation [52], a condition that is strikingly similar to that seen in many dogs with HSA [53].…”

Antibody–Drug Conjugates Using Mouse–Canine Chimeric Anti-Dog Podoplanin Antibody Exerts Antitumor Activity in a Mouse Xenograft Model

“…(11) PMab-38 did not react with lymphatic endothelial cells, and recognized dPDPN of renal epithelial cells weakly (11) although dPDPN is expressed in those cells. (12) Immunohistochemical analyses demonstrated that PMab-38 stained canine squamous cell carcinomas (13) and canine melanomas, (14) indicating that PMab-38 demonstrated cancer specificity. Epitope mapping studies revealed Tyr67 and Glu68 of dPDPN to be the critical epitopes of PMab-38.…”