PB0739 - Study of a low anticoagulant bovine heparin as a drug capable of disrupting tumor cell-platelet interaction and preventing hematogenous metastasis

Background: Metastasis is the leading cause of death in cancer patients. During metastasis, circulating tumor cells need to survive in the bloodstream and their interaction with platelets through P-selectin-ligand seems to be crucial. It has been demonstrated that unfactionated heparin sourced from porcine mucosa (porcine UFH) may interfere with P-selectin interaction. Recently, our group developed a new low-anticoagulant heparin derived from bovine mucosa ( LABH) with anticoagulant potency ~ 85% lower than porcine UFH. The advantage of LABH is their reduced risk of bleeding.

Aims: Our aim in this work was to investigate the potential use of LABH as an antimetastatic agent, evaluating its ability to interfere with tumor cell-platelet interaction

Methods: To evaluate the antimetastatic potential, C57Bl/6 mice were challenged with porcine UFH or LABH followed by intravenous injection of B16F10 cells (murine melanoma cell line). After 21 days, lungs were analyzed and metastatic foci were counted. To asses the effect of heparins in interfering with tumor cell-platelet interaction, isolated platelets from healthy volunteers were incubated with MV3 cells (human melanoma cell line). Next, we analyze the heparin ability of blocking P-selectin binding using U937 cell (PSGL-1+) and immobilized P-selectin.

Results: We observed that the number of metastatic foci in the lungs was significantly reduced when animals were pretreated with heparins (~80%). Both heparins were efficient in blocking MV3-platelet interaction in a dose-response manner, but LABH required higher doses than porcine UFH. When analyzing the heparin ability of blocking direct binding to P-selectin, we observed that porcine UFH showed ~ 60% of inhibition, while LABH was less effective (~ 45% ).

Conclusion(s): Our results demonstrate that despite presenting distinct patterns of sulfation and anticoagulant potential, both heparins significantly reduced lung metastasis, platelet-tumor cell adhesion and P-selectin binding. On the other hand, we hypothesize that LABH may act suppressing metastasis also by other mechanisms.