Uptake of platelets by cancer cells and recycling of the platelet protein CD42a.

Background It is well accepted that the bidirectional crosstalk between platelets and cancer cells promote tumorigenesis and metastasis. In an early step cancer cells trigger platelet granule and extracellular vesicle release that is needed to facilitate cancer cells survival in circulation. Objectives To discover the early crosstalk of cancer cells and platelets. Methods Cancer cells were incubated with freshly isolated and stained human platelets. Confocal laser scanning microscopy and flow cytometry was used to visualize and to quantify platelet uptake and the membrane presence of CD42 on cancer cells. Dyngo4a was used to test if platelet uptake is a dynamin-dependent process. Results We found a dynamin dependent uptake of platelets by cancer cells. This is followed by the recycling of the platelet-specific protein CD42a and its incorporation into cancer cell`s plasma membrane which is not a result of platelet RNA transfer by platelet derives microparticles and exosomes. Time course of platelet uptake follows a sigmoid function revealing that 50% of the cancer cells are positive for platelets after approx. 38min. Platelet uptake was observed for the tested cancerous cells (A549, MCF-7 and MV3) but not for the non-cancerous cell line 16HBE14o-. Conclusions Our results demonstrate that cancer cells hijack platelets by phagocytosis and recycling of platelet membrane proteins. The uptake of platelets has additional advantages for cancer cells: Access to the entire and undiluted platelet proteome, transcriptome and secretome. These novel findings will allow further mechanistic elucidation and thus gain deeper insights into platelet-assisted hematogenous metastasis.