Capability of Platelet Factor 4 to Induce Apoptosis in the Cancerous Cell Lines in Vitro

Platelet factor 4 (PF4) or CXCL4 is a member of CXC chemokine family which is stored in alpha granules of platelets. The main function known for PF4 is angiostasis which may contribute to prevent tumor metastasis. This feature is mediated by CXCR3 on the endothelial cells. Our principal aim was to study the apoptosis induction in three cell lines treated with PF4 and obtained from human platelet concentrates.
We evaluated the apoptotic effect of platelet-derived PF4 on the U266B1 and K562 cell lines expressing CXCR3, compared with Daudi as a CXCR3-negative cell line. PF4 was purified from human platelet concentrates by immunoaffinity chromatography and was concentrated. The quantity and molecular weight of the obtained PF4 was determined by enzyme-linked immunosorbent assay and sodium dodecyl sulfate polyacrylamide gel electrophoresis methods respectively. Cell lines were treated for 72 and 96 h with 90 μg/ml of PF4. Apoptosis was assayed by using CD95, WST-1, active caspase-3, and cell count.
Platelet-derived PF4 was a weak agent to induce apoptosis in U266B1 and K562 cell lines. Our data showed in terms of WST-1 and cell count had a significant difference between control and experiment groups (p≤0.05), while CD95, LDH, and active caspase-3 did not show such a difference (p>0.05).
We observed that PF4 released from platelets has a weak potential to induce apoptosis in cancerous cell lines. Other factors may also contribute to this process including the applied dose, purification method, cell line type, and its proteoglycan carrier.