PB0748 - Diminished platelet CLEC-2 sensitivity in kaposiform hemangioendothelioma identified with novel CLEC-2 antagonists

Monday, July 11, 2022

6:30 PM – 7:30 PM

Location: Exhibition

Presentation Format: Virtual

Co-Author(s)

AM

Alexey A. Martyanov

Researcher
Center for Theoretical Problems of Physicochemical Pharmacology
Moscow, Moskva, Russia
Ivan Tesakov, MD

Resident physician (hematologist)
Dmitry Rogachev National Medical Research Center Of Pediatric Hematology, Oncology and Immunology
Moscow, Moskva, Russia

Presenting Author(s)

Olga I. An

Junior Researcher
Center for Theoretical Problems of Physicochemical Pharmacology
Moscow, Moskva, Russia

Co-Author(s)

AI

Anastasia A. Ignatova

Researcher
Dmitry Rogachev National Medical Research Center Of Pediatric Hematology, Oncology and Immunology
Moscow, Moskva, Russia
GS

Galina S. A. Svidelskaya

Research Assistant
Dmitry Rogachev National Medical Research Centre of Pediatric Hematology, Oncology and Immunology
Moscow, Moskva, Russia
LK

Lili A. A. Khachatryan

Head of Department
Dmitry Rogachev National Medical Research Centre of Pediatric Hematology, Oncology and Immunology
Moscow, Moskva, Russia
JE

Johannes A. Eble

Professor
Institute of Physiological Chemistry and Pathobiochemistry, University of Münster
Munich, Bayern, Germany
DK

Dmitrii V. Kalinin

Research Group Leader
Institute of Pharmaceutical and Medicinal Chemistry, University of Münster
Munster, Nordrhein-Westfalen, Germany
AS

Anastasia N. Sveshnikova

Senior Researcher
Dmitry Rogachev National Medical Research Centre of Pediatric Hematology, Oncology and Immunology
Moscow, Moskva, Russia

Background: Kaposiform hemangioendothelioma (KHE) is a rare vascular tumor. 70% cases of KHE are associated with Kasabach-Merritt phenomenon (KMP) which includes thrombocytopenia and coagulopathy. Platelets are involved in KHE/KMP pathogenesis: KHE is enriched with podoplanin, which induces platelet adhesion and activation via CLEC-2 receptor. While applicability of conventional anti-platelet agents in KHE/KMP patients is controversial, novel anti-CLEC-2 agents could be beneficial.

Aims: The evaluation of CLEC-2-induced platelet activation in KHE/KMP.

Methods: 7 pediatric patients with KHE/KMP were enrolled in the study and compared with age-matched healthy donors (HDs). Platelets of the KHE/KMP patients were analyzed by flow cytometry and low-angle light-scattering aggregometry. The study was approved by the independent ethics committee of CTP PCP RAS and performed according to the Declaration of Helsinki. Mann-Whitney and Wilcoxon criteria were used for the data analysis.

Results: Quiescent platelet cytosolic calcium as well as platelet responsiveness to ADP, TRAP-6 and CRP was within normal ranges. Pre-incubation of platelets with CLEC-2 antagonists 2CP and HB125 resulted in mild increase in cytosolic calcium in HD platelets, but not in those of patients. CLEC-2 agonist rhodocytin-induced (200 nM) calcium and fibrinogen responses were diminished in KHE/KMP. CLEC-2 antagonists, 2CP and HB125, inhibited rhodocytin-induced platelet activation in both patients and HDs. Neither 2CP nor HB125 affected platelet responses to ADP or TRAP-6. However, 2CP inhibited CRP-induced platelet activation. Similar results were obtained in the aggregation assays.

Conclusion(s): CLEC-2-induced platelet signaling in KHE/KMP is significantly impaired. 2CP and HB125 decreased CLEC-2 induced calcium mobilization in both patients and HDs. Presumably, the high podoplanin expression in KHE cause consumption of platelets with normal and high CLEC-2 expression and thus enrich platelets with lower CLEC-2 in these patients. The study was supported by the ICCR of University of Münster (IZKF grant: Ebl4/009/21) and the RFBR Grants 17-00-00138 and 21-51-10005 (together with the RS of London).